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Abridged User's Guide for RAM The document contained in this file

1. SECTION 3 FEATURES AND LIMITATIONS USES ALGORITHM ASSUMPTIONS SECTION 4 BASIS FOR RAM DILUTION BY THE WIND STEADY STATE CONDITIONS SECTION 5 TECHNICAL DESCRIPTION CONCENTRATION SUM OF INDIVIDUAL CONTRIBUTIONS WIND SPEED PLUME RISE FOR POINT SOURCES BUOYANCY INDUCED DISPERSION FOR POINT SOURCES EFFLUENT RISE FOR AREA SOURCES CONCENTRATION FORMULAS N ECTION 6 VERIFICATION RUN N ECTION 7 USES OF RAM N ECTION 8 COMPUTER ASPECTS OF THE MODEL STRUCTURE OF RAM PROGRAM MODULES BRIEF DESCRIPTION OF SUBROUTINES PROCESSOR PROGRAM RAMMET N ECTION 9 INPUT DATA PREPARATION WN ECTION 10 EXECUTION OF THE MODEL AND SAMPLE TEST iii DISPERSION RESULTS IN GAUSSTAN DISTRIBUTED CROSS SECTIONS J 14 14 14 14 15 15 15 15 19 20 WN 7 ECTION 11 EFERENCES ERROR MESSAGES AND REMEDIAL ACTION 48 52 TABLE TABLE TABLE WM rR LIST OF TABLES EXPONENTS FOR WIND PROFILES RECORD INPUT SEQUENCE FOR RAM ERROR MESSAGES AND CORRECTIVE ACTION 15 30 48 The information in the original document of which this is an abridgement has been funded by the United States Environmental Protection Agency under Contract No EPA 68 02 4106 to Aerocomp Inc The original document was subjected to the Agency s peer and administrative review and was approved for publication as an EPA document Mention of trade names or commercia
2. First actual or estimated wind speed at stack top u h iS assumed to be available Stack Downwash To consider stack downwash the physical stack height is modified following Briggs 1973 p 4 The h is found from h h 2 v u h 1 5 d for v lt 1 5 uch 2 h h for v gt 1 5 u h where h is physical stack height meters v is stack gas velocity meters per second and d is inside stack top diameter meters This h is used throughout the remainder of the plume height computation If stack downwash is not considered h h in the following equations Buoyancy Flux For most plume rise situations the values of the Briggs buoyancy flux parameter F m s is needed The following equation is equivalent to Briggs 1975 p 63 Eq 12 F g v d T 4 T 3 where g is the acceleration of gravity 9 806 m s T T T T is stack gas temperature Kelvin and T is ambient air temperature Kelvin at stack top Unstable or Neutral Crossover Between Momentum and Buoyancy For cases with stack gas temperature greater than or equal to ambient air temperature it must be determined whether the plume rise is dominated by momentum or buoyancy The crossover temperature difference T is determined for 1 F less than 55 or 2 F greater than or equal to 55 If the difference between stack gas temperature and ambient air temperature T exceeds or equals the T plume rise is assumed to be buoya
3. AREA SOURCES UNITS OR SIDE LENGTHS SPECIFIED INCORRECTLY ERROR ON EAST MAXIMUM BOUNDARY The area source east boundary extends beyond the east boundary of the modeling region Reduce the area source size increase the size of the modeling region or recompile the program with larger dimensions AREA SOURCES UNITS OR SIDE LENGTHS SPECIFIED INCORRECTLY ERROR ON NORTH MAXIMUM BOUNDARY The area source north boundary extends beyond the north boundary of the modeling region Reduce the area source size increase the size of the modeling region or recompile the program with larger dimensions SOURCE x IS ALREADY LOCATED AT POSITION x CHECK SOURCE x Two sources are collocated Verify the input stream and separate or combine the 66 MESSAGE ACTION MESSAGE DESCRIPTION ACTION MESSAGE DESCRIPTION ACTION MESSAGE DESCRIPTION ACTION MESSAGE DESCRIPTION collocated sources AREA ARRAY IS TOO WIDE FOR PAGE SIZE THEREFORE WILL NOT BE PRINTED The area source array cannot be printed due to its size If a printout reduce the size of the area source region is needed AKERROR USER TRIED TO SPECIFY x SIGNIFICANT SOURCES BUT IS ONLY ALLOWING y TOTAL SIGNIFICANT SOURCES IN THIS RUN RUN TERMINATED CHECK INPUT DATA total The number of significant sources exceeds the significant sources specified Verify consistency of significant sources in
4. 2 Side length of area source user units Note that ASORC 5 NAS side length is read out of order to conform with the existing order of IPP emissions data ASORC 3 NAS 43 52 F10 2 Sulfur dioxide emission g sec rate for entire area ASORC 4 NAS 53 62 F10 2 Particulate emission rate g sec for entire area Particulate Emission Rate for entire area is a total rate for the entire area It is later transformed into gm sec m As with point sources 51 emission rates for other pollutants may be substituted for sulfur dioxide and particulates with appropriate name changes made in the data statements to modify titles on the printouts ASORC 6 NAS 63 72 F10 2 Area source height m Although only one pollutant can be considered for a given run of RAM both of the entered emission rates are listed in the output One of the emission rates may be left off and will appear as zeros in the output Area sources can vary in size but certain requirements must be met There must be a definable internal unit such that the side length of all other area sources is an integer multiple of the side length of this internal unit For example if an emission inventory consists of area source squares having side lengths of 1 2 5 5 and 10 km the internal unit must be chosen to equal 0 5 km It is better to conduct emission inventories so that area source squares have side lengths that are multiples of the side lengths of the smallest area source 44
5. 4 35 IDATE 1 IDATE 2 THSTRT xFF is free format FFX FF FF 36 2 digit year Starting Julian day Starting hour 4444444444444444444444444444444404 4444444444444444444444444444444444444 4 Record type and variable Units Column Format Variable description 4444444444444444444444444444444404 4444444444444444444444444444444444444 4 NPER oe NAVG TPOL aoe MUOR jog NSIGP ae NSIGA ges NAVS 5 CONONE ae Example multipliers are FF FF FF FF FF FF FF FF Number of averaging periods Number of hours in an aie averaging period com monly 24 Pollutant indicator 3 sulfur dioxide 4 suspended particulate Model indicator 1 urban mode 2 rural mode Number of point sources from which concentration contributions are desired maximum 25 Number of area sources from which concentration contributions are desired maximum 10 Additional averaging time for high five table Usu ally 2 4 6 or 12 Multiplier to convert user units to kilometers 3 048 x 10 for feet to kilometers 1 609347 37 for miles to kilometers 1 0 x 10 for meters to kilometers UNITS FF Number of user units per smallest area source side length Should equal 1 if no area sources internal units Z FF Receptor height 38 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type and
6. Briggs plume rise equations are used to estimate effective height of point sources Concentrations from the point sources are determined using distance crosswind and distance upwind from the receptor to each source Considerable time is saved in calculating concentrations from area sources by using a narrow plume simplification which considers sources at various distances on a line directly upwind from the receptor to be representative in the crosswind direction of the sources at those distances affecting the receptor Area source sizes are used as given in the emission inventory in lieu of creating an inventory of uniform elements Options are available to allow the use of four different types of receptor locations those with coordinates input by the user those with coordinates determined by RAM and are downwind of significant point and area sources where maxima are likely to occur those with coordinates determined by RAM to give good area coverage of a specific portion of the region and those with coordinates determined by RAM to radially circle a designated point radial distances are supplied by the user Options are also available to limit the output produced Urban planners may use RAM to determine the effects of new source locations and control strategies upon short term air quality If the input meteorological parameter values can be forecast with sufficient accuracy control agency officials may use RAM to predi
7. CONTRIBUTIONS The total concentration of a pollutant at a receptor is taken as the sum of the individual concentration estimates from each point and area source affecting that receptor that is concentrations are additive Concentration estimates for averaging time longer than one hour are determined by linearly averaging the hourly concentrations during the period WIND SPEED In RAM the input wind speed data must include the height above ground of the measurements and may include the exponents for the wind profile If no exponents are given in the input the values in Table 1 are used The wind speed at the physical stack height h is calculated from u h u h h ee where u is the input wind speed for this hour h is the height of wind measurement and the exponent p for the wind profile is a function of stability If u h is determined to be less than 1 m s it is set equal to 1 m s TABLE 1 EXPONENTS FOR WIND PROFILES 44444444444444444444444444444444044444444444444444444444444444444444444 4 URBAN RAM RURAL RAMR Stability class exponent exponent 44444444444444444444444444444444044444444444444444444444444444444444444 4 A 0 16 0 07 B 0 15 0 07 C 0 20 0 10 D 0 25 0 1 5 E 0 30 0 35 F 0 30 0595 4444444444444444444444444444444444444444444 444444444444444444444444444 PLUME RISE FOR POINT SOURCES 18 The use of the methods of Briggs to estimate plume rise and effective height of emission are discussed below
8. Height If vertical temperature soundings are available from a representative location they should be used with hourly surface temperatures to estimate hourly mixing heights for periods with neutral or unstable stratification If National Weather Service hourly data are used in the model two values of mixing height per day are required These are the maximum and minimum mixing heights as defined by Holzworth 1972 The preprocessor program RAMMET provides a crude interpolation to obtain hourly mixing heights however this interpolation does not consider hourly surface temperatures Wind Speeds and Directions Wind speeds and directions should be hourly averages National Weather Service hourly observations are not really hourly averages but are averages of a few minutes at the time of the observation usually 5 to 10 minutes prior to the hour Input winds should be representative of the entire region In addition to input winds the user is required to give the anemometer height The increase of wind speed with height is included based upon a power law wind profile The exponent is dependent upon the stability classification and surface roughness See Irwin 1979 For any given hour winds at various heights above ground are likely to deviate considerably from this climatological mean profile If user defined exponents are not supplied default exponents are used by the model There is no inclusion of directional shear with height
9. TOPT 20 20 I1 Omit point source list IOPT 21 21 I1 Omit area source list and o map IOPT 22 22 I1 Omit emissions with height table IOPT 23 23 I1 Omit resultant meteorology o data summary for averaging period IOPT 24 24 I1 Omit all hourly output point area summaries IOPT 25 25 I1 Omit hourly point contribu o tions IOPT 26 26 I1 Omit meteorology data on B hourly point contribu tions IOPT 27 27 I1 Omit plume height and distance to final rise on hourly point contribution IOPT 28 28 I1 Omit hourly area contributions IOPT 29 29 I1 Omit meteorology data on 43 IOPT 30 LOPT C31 IOPT 32 IOPT 33 30 31 32 33 I1 I1 I I1 44 hourly area contributions Omit hourly summary Omit meteorological data on hourly summary Omit all averaging period output Omit point averaging period contributions 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type and variable Column Format Variable description Units 44444444 4444444444 44444444 44444404 4444444444 444444444444444444 444444444 4 IOPT 34 34 I1 Omit area averaging period contributions IOPT 35 35 I1 Omit averaging period summary IOPT 36 36 I1 Omit average concentrations and highest five concen trations table IOPT 37 37 Pi Not used The remaining options control the flow of the program and the amount of output This is especially so for Option 40 in which a l
10. This means that the direction of flow is assumed to be the same at all levels over the region The taller the effective height of the emission the larger the expected error in the direction of plume transport Although the effects of surface friction are such that wind direction usually veers turns 10 clockwise with height the thermal effects in response to the horizontal temperature gradient in the region may cause increased veering or can overcome the effect of friction and cause backing turning counterclockwise with height National Weather Service observations report wind to the nearest 10E In order to avoid unrealistic results that would occur from having the wind come from exactly the same direction hour after hour the program RAMMET which processes the meteorological data uses random numbers from 0 to 9 to add from 4E to 5E to the reported wind direction The purpose of this is to prevent an extreme overestimate of concentration at a point downwind of a source during a period of steady wind when sequential observations show the same direction Rather than allow the plume centerline to remain in exactly the same position for several hours the alteration allows for some variation of the plume centerline within the 10E sector Although this can in no way simulate the actual sequence of hourly events wind direction to 1E accuracy cannot be obtained from wind direction reported to the nearest 10E such alterations can be expecte
11. and area source emissions specification of significant point and area sources input of receptors by specifying coordinates option for RAM to generate receptors downwind of significant point and area sources option for RAM to generate a honeycomb array of receptors input of radial distances to generate a polar coordinate receptor array The following are options to omit certain outputs A number of these options should be used or the program will generate large quantities of printed information point source list area source list and map emissions with height table resultant meteorological data summary for the averaging period all hourly output point area summaries hourly point contribution meteorological data on hourly point contributions plume height and distance to final rise on hourly point contributions hourly area contributions meteorological data on hourly area contributions hourly summary meteorological data on hourly summary all averaging period output point averaging period contributions area averaging period contributions averaging period summary average concentrations and high five table The following options can also affect the amount of output use of a default option use of parts of segmented runs output of partial concentrations to disk or tape output of hourly concentrations to disk or tape output of averaging period concentrations
12. are allowed for adjacent hours Hourly mixing height is interpolated from the twice a day estimates Hourly meteorological data of wind direction wind speed temperature stability class and mixing height are written into a file with one record per day for the entire year Random numbers can be read from a file or generated by the computer used 34 SECTION 9 INPUT DATA PREPARATION In this section the general input data requirements are listed There are 18 record types in the input stream Each record type consists of one or more records Table 2 describes the input data in some cases an explanation follows the entry TABLE 2 RECORD INPUT SEQUENCE FOR RAM 444444444444444444444444444444444444404 44444444444 444444444444444444444 4 Record type and variable Column Format Variable description Units 444444 44444444444444444444444444444444444444444444440444444444444444444 4 Record type 1 LINE1 1 80 20A4 80 character title Record type 2 LINE2 1 80 20A4 80 character title Record type 3 LINE3 1 80 20A4 80 character title RECORDS 1 3 Each card image has up to 80 alphanumeric characters The input title appears on all output and can suit the user Normal use has been to identify the user and run date on card image 1 the location and date of the emissions data on card image 2 and the location and dates of both surface and upper air meteorological data on card image 3 RAM RECORD TYPE 4 14 variables Record type
13. combination with any of Options 15 16 or 17 IOPT 43 43 I1 Write averaging period concentrations in card image format 80 bytes to Unit 1 IOPT 44 44 I1 Not used this version IOPT 45 45 I1 Not used this version IOPT 46 46 I1 Not used this version IOPT 47 47 I1 Not used this version IOPT 48 48 I1 Not used this version IOPT 49 49 I1 Not used this version 47 IOPT 50 50 I1 Not used this version RAM RECORD TYPE 6 2 variables 1 to 7 values Selection of the default option Option 38 causes wind exponents to be set to the default values for the appropriate urban or rural cases This record is still required to input the anemometer height all other data on the record will be ignored when Option 38 is set Record type 6 HANE FF Anemometer height m PECT FF Wind speed power law exponents 48 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type and variable Column Format Variable description Units 44444444 4444444444 44444444 44444404 4444444444 444444 444444444444 444444444 4 RAM RECORD TYPE 7 9 variables 8 values one of these records for each point source This is used if Option 5 1 the user inputs point sources and Option 7 0 no emissions are entered from a previous run Record type 7 PNAME I NPT 1 12 3A4 l2 character point source identification SOURCE 1 NPT 13 20 F8 2 East coordinate of point source user units SOURCE 2 NPT
14. iS usually dominated by buoyancy plume rise due to momentum is also taken into account Merging of nearby buoyant plumes is not considered Stack tip downwash is considered but building downwash is not The variation of effective height of emission from area sources as a function of wind speed is thought to be an important factor in properly simulating dispersion in urban areas Since this effect is seldom considered in the compilation of urban area emission inventories it is difficult to have the appropriate parameters to estimate this effect however it can be approximated in RAM The methodology used is explained in Section 5 Emission Inventories For similar meteorological conditions the contribution to the concentration at a receptor from a source is directly proportional to the emission rate from that source It is imperative therefore to have emissions expressed accurately Many air pollutant sources vary emissions with time such as by hour of the day or weekdays versus weekends and attempts should be made to include these variations For facilities with detailed emission inventories hourly emissions can be determined external to RAM and entered via a separate file Hourly exit velocities are calculated within RAM in proportion to annual exit velocities as hourly emissions are to annual emissions Removal or Chemical Reactions Transformations of a pollutant primarily as a function of time resulting in loss of that polluta
15. match the internal date calculated by RAM Verify data sequence in the hourly area source emission file 4444444444444444444444444444444444444444444444444444444444444444444444 4 69 REFERENCES Briggs Gary A 1969 Plume Rise USAEC Critical Review Series TID 25075 National Technical Information Service Springfield VA 81 pp Briggs Gary A 1971 Some recent analyses of plume rise observation in Proceedings of the Second International Clean Air Congress edited by H M Englund and W T Beery Academic Press New York pp 1029 1032 Briggs Gary A 1972 Discussion on chimney plumes in neutral and stable surroundings Atmos Environ 6 507 510 Briggs Gary A 1974 Diffusion Estimation for Small Emissions In ERL ARL USAEC Report ATDL 106 U S Atomic Energy Commission Oak Ridge TN 59pp Briggs Gary A 1975 Plume rise predictions Chapter 3 pp 59 111 in Lectures on Air Pollution and Environmental Impact Analysis Duane A Haugen editor Amer Meteorol Soc Boston Mass 296 pp Chico Thomas and Joseph Catalano 1986 Addendum to the User s Guide for MPTER EPA 600 8 86 021 U S Environmental Protection Agency Research Triangle Park NC 196 pp July 1986 Available only from NTIS Accession No PB 86 217 163 AS Gifford Franklin A Jr 1960 Atmospheric dispersion calculations using the generalized Gaussian plume model Nucl Saf 2 2 56 59 Gifford Franklin A and Hanna Steven R 197
16. may be very steep especially those due to point source plumes Therefore the addition of more receptors will result in a more complex concentration pattern and some hot spots The user when searching for maximum concentrations must decide on receptor spacing commensurate with resources analysis 28 time and the purpose of the project before including additional receptors For the typical run hourly output would be desired so option 24 should be set for hourly output If option 24 is not set no hourly output is printed The use of option 40 to write partial concentrations onto a disk file should be used only if additional computer analysis is intended using the individual contributions of sources upon particular receptors Computer programs to perform this analysis must be written by the individual user to suit his or her purpose Option 30 is checked only if option 24 is used to obtain hourly summaries The use of option 30 will print a summary page for each hour This summary provides the total concentration for each receptor the contribution to the concentration from all point sources the contribution to the concentration from all area sources the contribution from all the significant point sources combined and the contribution from all the significant area sources Information that will be obtained by using option 24 but not option 30 are the contributions to the concentrations at each of the receptors from each of the signific
17. release the plume is nearly symmetrical about its centerline buoyancy induced dispersion in the horizontal direction F equal to that in the vertical direction is used Foa ATES 20 To yield an effective lateral dispersion value Fe this expression is combined with that for dispersion due to ambient turbulence A a tas 21 EFFLUENT RISE FOR AREA SOURCES RAM can include in effective height with wind speed for area sources The input area source height H is assumed to be the average physical height of the area source plus the effluent rise with a wind speed of 5 m s The user specifies the fraction f of the input height that represents the physical height h This fraction is the same for all area sources in the inventory p h f H 22 p 23 The difference is the effluent rise for a wind speed of 5 m s JH u 5 H h 23 p If f 1 there is no rise and the input height is the effective height for all wind speeds For any wind speed u the rise is assumed to be inversely proportional to wind speed and is determined from H u CH h Zu 24 and the effective height is He u h H u 25 p CONCENTRATION FORMULAS Concentrations from Point Sources The upwind distance x of the point source from the receptor and the crosswind distance y of the point source from the receptor are calculated as part of estimates for each source receptor pair for each simulated hour Both dispersion parame
18. the model If they are input by the user receptor name as well as coordinates may be provided If generated by the program the user selects whether a polar coordinate grid of 180 receptors 36 radials by 5 distances or a honeycomb receptor configuration is desired Also when significant sources are specified the model selects two receptors downwind of each source where maxima are likely to occur A total of 180 receptors are permitted On output the model produces printed and disk or tape files The printed output lists the options and source information including a ranking according to source height those selected by the user as Significant are properly identified Receptors are next listed with their appropriate coordinates This is followed by the meteorological parameters as input by the user Model calculated concentrations are tabulated by receptor Various other output files can be obtained SECTION 1 INTRODUCTION The RAM system is based on the Gaussian plume equation which assumes steady state it includes dispersion algorithms for both urban and rural situations The algorithm can be used for short term one hour to one day determination of urban air quality resulting from pollutants released from multiple point and area sources The algorithm was first described by Novak and Turner 1976 It is applicable to locations with level or gently rolling terrain where a single wind vector for each hour is a reasonable approximatio
19. to a file output of averaging period concentrations to card image records Meteorological Data The meteorological data required for the model are power law wind profile exponents for each stability class anemometer height stability class at the hour of measurement wind speed air temperature wind direction mixing height Source Emissions Data The information required of the emissions sources is coordinates of the point source emission rate for sulfur dioxide emission rate for suspended particulates physical stack height stack gas temperature stack exit diameter stack gas exit velocity coordinates of SW corner of area source side length of area source The user may also specify up to 25 point sources and up to 10 area sources as being significant i e sources for which additional information is output Receptor Data The user may also choose to input the coordinates of the receptors up to 180 or enter one to five radial distances in which case RAM will generate 36 receptors for each distance entered If the user specifies the array boundaries RAM can also generate its own honeycomb array of receptors Additionally RAM can generate receptors downwind of Significant point or area sources if the significant source option is used SECTION 3 FEATURES AND LIMITATIONS USES RAM is primarily a short term one hour to one day urban or rural algorithm used to estimate ai
20. variable Column Format Variable description Units 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 HAFL FF Pollutant half life sec An entry of zero in HAFL will cause RAM to skip pollutant loss calculations RAM RECORD TYPE 5 The values are for 50 different options 1 is used to employ the option and a zero indicates non use Record type 5 IOPT 1 1 I1 No stack downwash IOPT 2 2 I1 No gradual plume rise IOPT 3 3 I1 Use buoyancy induced dispersion IOPT 4 4 I1 Not used IOPT 5 5 I1 Input point sources IOPT 6 6 I1 Input area sources IOPT 7 7 I1 Use emissions from previous run Data accessed from Unit 9 IOPT 8 8 I1 Meteorology data in input 39 stream Otherwise input from Unit 11 IOPT 9 9 I1 Read hourly point source emissions Unit 15 IOPT 10 10 I1 Read hourly area source emissions Unit 16 IOPT 11 11 I1 Specify significant point sources Option 11 will allow the examination of the individual contributions to each receptor from each of the specified sources Both point and area sources may be specified See IOPT 12 40 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type and variable Column Format Variable description Units 44444444 4444444444 44444444 44444404 4444444444 444444444444444444 444444444 4 IOPT 12 12 I1 Specify significant area sources IOPT 13 13 I1 Not used IOPT 14 14 I1 Ente
21. vector for the averaging period selected is used to determine the direction of these receptors from the sources averaging times that contain significant wind shifts may result in misleading averages The user should note that when options 15 and 16 are used to locate receptors downwind from significant sources the locations for these receptors will shift for each averaging period dependent upon the resultant meteorological conditions for each period Therefore receptors with the same numbers will be at different locations for different averaging times If the user desires to cover a specific area so that pollutant patterns are discerned option 17 can be used to place additional receptors The pattern used is such that adjacent receptors are equidistant this is referred to aS a honeycomb pattern The distance between receptors is selected by the user as are the boundaries of the area covered If the boundaries are entered as zeros the boundaries are set to coincide with the boundaries of the area source map array Since the honeycomb receptors are set for each averaging time they may be different from one averaging time to another The model can be executed for an hour without receptors downwind of significant sources in order to obtain a list of receptors for good area coverage Their coordinates can then be input for a longer period run where it is desired to have receptors in fixed positions It should be noted that concentration gradients
22. 1 Urban air pollution modeling in Proceedings of the Second International Clean Air Congress edited by H M Englund and W T Beery Academic Press New York pp 1146 1151 Gifford Franklin A 1976 Turbulent diffusion typing schemes a review Nucl Saf 17 1 68 86 Holzworth George C 1972 Mixing Heights Wind Speeds and Potential for Urban Air Pollution through the contiguous United States Office of Air Programs Publication No AP 101 U S Environmental Protection Agency Raleigh NC 118 pp Irwin J S 1979 A theoretical variation of the wind profile law exponent as a function of surface roughness and stability Atmos Environ 13 191 194 Novak Joan Hrenko and Turner D Bruce 1976 An efficient Gaussian plume multiple source air quality algorithm J Air Poll Control Assoc 26 6 570 575 Pasquill Frank 1961 The estimation of the dispersion of windborne material Meteorol Mag 90 1063 33 49 Pasquill Frank 1974 Atmospheric Diffusion 2d ed John Wiley and Sons New York 429 pp 70 Pasquill Frank 1976 Atmospheric Dispersion Parameters in Gaussian Plume Modeling Part II Possible Requirements for Change in the Turner Workbook Values EPA 600 4 76 030b U S Environmental Protection Agency Research Triangle Park NC 44 pp Pierce T E and D B Turner 1980 User s Guide for MPTER A Multiple Point Gaussian Dispersion Algorithm with Optional Terrain Adjustment EPA 600 8 80 016 U S
23. 21 28 F8 2 North coordinate of point source user units SOURCE 3 NPT 29 36 F8 2 Sulfur dioxide emission g sec rate Emission rates for pollutants other than sulfur dioxide and particulates may be substituted If substitutions are made changes in data statements are necessary in order to have the proper pollutant names on the printed output SOURCE 4 NPT 37 44 F8 2 Particulate emission rate g sec SOURCE 5 NPT 45 52 F8 2 Physical stack height m SOURCE 6 NPT 53 60 F8 2 Stack gas temperature K SOURCE 7 NPT 61 68 F8 2 Stack inside diameter 49 m SOURCE 8 NPT 69 76 F8 2 Stack gas exit velocity m Sec To indicate the end of point source records the word ENDP is placed in record columns 1 to 4 RAM RECORD TYPE 8 7 variables 6 values one of these records is required for each area source This is used if Option 6 1 the user inputs area sources and Option 7 0 no emissions input from previous run 50 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type and variable Column Format Variable description Units 44444444 444444444 444444444 44444404 4444444444 444444444444444444 444444444 4 Record type 8 ANAME Jd NAS 1 12 3A4 12 character area source identification ASORC 1 NAS 13 22 F10 2 East coordinate of SW comer of area source user units ASORC 2 NAS 23 32 F10 2 North coordinate of SW corner of area source user units ASORC 5 NAS 33 42 F10
24. 44444444444444444444444444444444444444444444444444444444444444444444 4 Record type and variable Column Format Variable description Units 4444444444444444444444444444444444444444444444444444444444444444444444 4 squares Also if a grid is constructed of unlt squares squares having side length of one internal unit the boundaries of all area sources must coincide with lines In that grid there can be no overlap of one area source over another Although these statements may seem restrictive the area source entries to RAM are quite versatile Concentrations from area sources are calculated by performing computations for each area source encountered in proceeding from a receptor in the upwind direction until the upwind boundary of the area source is encountered If there are large areas larger than the unit square of zero emissions within the rectangle that includes all area sources area source region it is desirable to define these as area sources with zero emissions in squares as large as possible This will result in considerable savings in computer processing time If the height of emission is the effective height of the area source at a wind speed of 5 m sec and if the physical height of the source is a set fraction of this value which is the same for all area sources it will be possible to consider the variation of effective height of area sources with wind speed in RAM Otherwise the fraction will be 1 0 and 52 it will be ass
25. Abridged User s Guide for RAM The document contained in this file is an abridged version of the most recent version of the RAM User s Guide This document has been placed on the SCRAM website to facilitate the immediate use of the RAM model without having to wait for delivery of the complete user s guide Although some portions of the User s Guide have been omitted to keep the file size to a reasonable size nothing was omitted that is needed by the user to run the model Nevertheless the user is strongly encouraged to obtain the complete user s guide from NTIS The NTIS document number and ordering information can be found on the SCRAM website on the User s Guide page under NTIS Availability Abridgement of EPA 600 8 87 046 October 1987 USER S GUIDE FOR RAM SECOND EDITION ABRIDGED by Joseph A Catalano Aerocomp Inc 3303 Harbor Boulevard Costa Mesa California 92626 and D Bruce Turner and Joan H Novak Meteorology and Assessment Division Atmospheric Sciences Research Laboratory Research Triangle Park NC 27711 Abridged version by Computer Sciences Corporation under contract to the U S EPA ATMOSPHERIC SCIENCES RESEARCH LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U S ENVIRONMENTAL PROTECTION AGENCY RESEARCH TRIANGLE PARK NC TABLE OF CONTENTS AFFILIATION PREFACE TO THE ABRIDGED VERSION ACKNOWLEDGMENTS EXECUTIVE SUMMARY SECTION 1 INTRODUCTION SECTION 2 DATA REQUIREMENTS CHECKLIST
26. Briggs 1969 p 59 Eq 5 2 H h 3 d v u h 10 Briggs 1969 suggests that this equation is most applicable when v u is 20 greater than 4 Since momentum rise occurs quite close to the point of release the distance to final rise is set equal to zero Stability Parameter For stable situations the stability parameter s is calculated from the equation Briggs 1971 p 1031 s g M M T 11 where 2 is potential temperature AS an approximation for stability class E or 5 M 2z is taken as 0 02 K m and for stability class F or 6 M M is taken as 0 035 K m Stable Crossover Between Momentum and Buoyancy For cases with stack gas temperature greater than or equal to ambient air temperature it must be determined whether the plume rise is dominated by momentum or buoyancy The crossover temperature difference T is found by setting Briggs 1975 p 96 Eq 59 equal to Briggs 1969 p 59 Eq 4 28 and solving for T The result is T 0 019582 v T st G12 if the difference between stack gas temperature and ambient air temperature T exceeds or equals T the plume rise is assumed to be buoyancy dominated if T is less than T the plume rise is assumed to be momentum dominated Stable Buoyancy Rise For situations where T is greater than or equal to T buoyancy is assumed to dominate The distance to final rise in kilometers is determined by the equivalent of a combination of Brigg
27. E NUMBER OF SIGNIFICANT POINT SOURCES WAS FOUND TO EXCEED THE LIMIT 25 USER TRIED TO INPUT x SOURCES AK mKIAK EXECUTION TERMINATED 4 DESCRIPTION The maximum number of significant point sources allowed by the program is 25 ACTION Modify the value input in record type 9 to be 25 MESSAGE NSIGA THE NUMBER OF SIGNIFICANT AREA SOURCES WAS FOUND TO EXCEED THE LIMIT 10 USER TRIED TO INPUT x SOURCES BARA EXECUTION TERMINATED rae es DESCRIPTION The maximum number of significant area sources allowed by the program is 10 A C T I O0 N Modify the input value to be 10 MESSAGE USER TRIED TO INPUT MORE THAN x POINT SOURCES THIS GOES BEYOND THE CURRENT PROGRAM DIMENSIONS DESCRIPTION The maximum number of point sources is 250 ACTION Reduce the number of point sources to comply with the maximum of 250 65 MESSAGE DESCRIPTION ACTION MESSAGE Oo ACTION MESSAGE Oo ACTION MESSAGE Oo ACTION MESSAGE DESCRIPTION ACTION ESCRIPTION ESCRIPTION ESCRIPTION USER TRIED TO INPUT MORE THAN x AREA SOURCES BEYOND THE CURRENT PROGRAM DIMENSIONS THIS GOES The maximum number of area sources is 100 Reduce the number of area maximum of 100 sources to comply with the DIMENSIONS TOO SMALL TO HOLD ARRAY x BY y The internal dimensions of the area 25 25 for internal units source array are Recompile with dimensions larger than 25 25
28. Environmental Protection Agency Research Triangle Park NC 247 pp Pierce T E D B Turner J A Catalano and F V Hale 1982 PTPLU A Single Source Gaussian Dispersion Algorithm EPA 600 8 82 014 U S Environmental Protection Agency Research Triangle Park NC 27711 Turner D B 1964 A diffusion model for an urban area J Appl Meteorol 3 1 83 91 Turner D B 1970 Workbook of Atmospheric Dispersion Estimates Office of Air Programs Publication No AP 26 U S Environmental Protection Agency Research Triangle Park NC 84 pp U S Environmental Protection Agency 1986 User s Network for Applied Modeling of Air Pollution UNAMAP Version 6 Library of Computer Programs on Magnetic Tape NTIS PB86 222 361 National Technical Information Service Springfield VA U S Environmental Protection Agency 1984 Calms Processor CALMPRO User s Guide EPA 901 9 84 001 U S Environmental Protection Agency Region I Boston MA 02003 Available only from NTIS Accession Number PB84 229 467 U S Environmental Protection Agency 1986 Guideline on Air Quality Models Revised EPA 450 2 78 027R U S Environmental Protection Agency Research Triangle Park NC 27711 FA
29. ST RAM produces an error free compile on IBM MVS and DEC VAX VMS computers with comparable output results Job Control Language JCL for model execution on an IBM system under MVS would be as follows JOBID JOB PROJ ACCT OTHER TIME 1 RAMP EXEC PGM RAM TIME 20 STEBLIB DD DSN USERID MODELS LOAD DISP SHR FTO6FO01 DD SYSOUT A FTO5F001 DD Input records Sample Test The example given in Chapter 10 of the original User s Guide available from NTIS uses one year of meteorological data processed by RAMMET and uses the default option for regulatory application in the urban mode When the default option is exercised the following features apply urban dispersion parameters are used final plume rise is used buoyancy induced dispersion is accounted for urban profile exponents of 215 15 2205 25 30 and 30 are used stack tip downwash is calculated calms are processed according to regulatory guidance options 7 8 11 12 15 16 and 39 through 43 are set to zero and output options 23 through 35 are set to 1 64 SECTION 11 ERROR MESSAGES AND REMEDIAL ACTION RAM can generate up to 22 error messages some of which cause program termination Table 3 lists each message along with error description and suggested corrective action TABLE 3 ERROR MESSAGES AND CORRECTIVE ACTION FADAAAAAAAAAAAAAAAAAAAAAA4AAAAAANA 4444444444444444444444444444444444444 4 MESSAGE NSIGP TH
30. ant sources The maximum of 10 significant area sources results in an additional page of output per simulated hour The maximum of 25 Significant point sources results in three additional pages of output per simulated hour one page for every 10 significant point sources or fraction thereof Unless the concentration contributions are specifically needed for analysis of contributions from particular sources option 30 should be zero to reduce the quantity of output Option 8 would be set to one to enter meteorological data as part of the run stream rather than reading an external file using unit 11 Options 9 and 10 are set to one to enter hourly emissions If the contribution at a receptor from particular sources is of interest and if these particular sources are not high enough to be included in the significant source list from RAM options 11 and 12 may be used to specify the sources of interest If option 11 or 12 is used to obtain concentration contributions for the averaging time it is desirable to leave option 30 off to obtain hourly output Option 41 or 42 would not usually be employed unless concentrations at each receptor are required for further analysis or are to be used with graphics software to produce concentration isopleth maps 29 SECTION 8 COMPUTER ASPECTS OF THE MODEL STRUCTURE OF RAM RAM consists of three sections preprocessing subroutines main logic and output subroutines Inputs for the model are assumed t
31. arge file can be generated by employing this option IOPT 38 38 I1 Set default option for regulatory application Option 38 sets a series of options and parameters when the model is to be used for regulatory application IOPT 39 39 I1 Part of segmented run IOPT 40 40 I1 Write partial concentra tions to disk or tape Unit 10 The user will need to write the software to process this output Although it is unlikely that Options 39 and 40 will be employed on the same run it is possible to do so However the second and subsequent 45 segments will not skip over previously generated partial concentration files Therefore unless Unit 10 accesses a different file on each segment any previously generated partial concentration files will be overwritten 46 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type and variable Column Format Variable description Units 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 IOPT 41 41 I1 Write hourly concentrations to disk or tape Unit 12 IOPT 42 42 I1 Write averaging period concentration to disk or tape Unit 13 The output files generated by Options 41 and 42 are useful only when the receptors are set for the run and not varying from one averaging period to another Therefore these options can be used with Options 14 and 18 but a program termination will occur in trying to use Option 41 or 42 in
32. bstituted instead General In working through the receptors to determine concentrations for a given hour the first time a source is found to lie upwind of a receptor the following quantities are determined and stored for that source u h h F H and X These quantities are then used each time this source is encountered during this hour without recalculation Only if the upwind receptor source distance is less than x is the effective plume height determined for each occurrence by the last equation mentioned 22 BUOYANCY INDUCED DISPERSION FOR POINT SOURCES For strongly buoyant plumes entrainment as the plume ascends through the ambient air contributes to both vertical and horizontal spread Pasquill 1976 suggests that this induced dispersion F can be approximated by the plume rise divided by 3 5 F h 3 5 18 where h is either the gradual plume rise as calculated by Eq 5 for distances less than the distance to final rise or the final rise for distances greater than that distance The effective dispersion can then be determined by adding variances P52 Fa FANA 19 where F is the effective dispersion and F is the dispersion due to ambient turbulence levels At the distance of final rise and beyond the induced dispersion is constant based on the height of final rise At distances closer to the source gradual plume rise is used to determine the induced dispersion Since in the initial growth phases of
33. ccount these deficiencies by calculating averages for periods longer than three hours in such a way that persistent light wind conditions do not cause a gross overestimate of concentrations at a given receptor RAM is not appropriate for making concentration estimates for topographic complications The greater the departure from relatively flat terrain conditions the greater the departure from the assumptions of the algorithm RAM is most applicable for pollutants that are quite stable chemically and physically A general loss of pollutant with time can be accounted for by the algorithm Selective removal or reaction at the plume ground interface or dependence upon concentration levels may not be well handled by RAM 15 SECTION 4 BASIS FOR RAM The basis for RAM is also discussed in Novak and Turner 1976 The user may select use of either urban or rural parameters The urban dispersion parameters F and F are those suggested by Briggs and reported by Gifford 1976 The urban F s are functions of distance between source and receptor and of atmospheric stability class where the class is specified by open country conditions The dispersion parameters for rural conditions are those of Pasquill Gifford Pasquill 1961 Gifford 1960 as used in the UNAMAP programs PTPLU CRSTER and MPTER These values are equivalent to the dispersion parameter values given in Figures 3 2 and 3 3 of the Workbook of Atmospheric Dispersion Estimates Tur
34. ct ambient air quality levels primarily over the 24 hour averaging time to locate mobile air sampling units and to assist with emission reduction tactics Diurnal and day to day emission variations must be considered in the source inventory input to the model especially for control tactics For most of these uses the optional feature to assist in locating concentration maxima should be used Computations are organized so that execution of the program is rapid thus real time computations are feasible This document is divided into three parts each directed to a different reader managers dispersion meteorologists and computer specialists The first three sections are aimed at managers and project directors who wish to evaluate the applicability of the model to their needs Sections 4 5 6 7 and 10 are directed to dispersion meteorologists or engineers who are required to become familiar with details of the model Finally Sections 8 through 11 are directed toward persons responsible for implementing and executing the program SECTION 2 DATA REQUIREMENTS CHECKLIST Model Options RAM requires data on options sources meteorology and receptors The user must indicate which of the following options are to be used stack tip downwash gradual plume rise buoyancy induced dispersion input of point and area sources emissions from a previous run of RAM meteorological data on card image records input of hourly point
35. d to result in concentrations over a period of record to be more representative than those obtained using winds to only the 10E increments reported Sensitivity tests of this alteration for single sources have indicated that where a few hours of unstable conditions are critical to producing high concentrations the resulting concentrations are extremely sensitive to the exact sequence of random numbers used such as two wind directions 1E apart versus two wind directions 9E apart Differences of 24 hour concentrations from a single source by 40 to 50 percent have appeared in the sensitivity tests due to the alteration It is therefore important to use accurate wind information as input to RAM Dispersion Parameter Values The dispersion parameter values representative for urban areas are those recommended by Briggs and included in Figure 7 and Table 8 of Gifford 1976 The dispersion parameter values representative for open countryside are the Pasquill Gifford curves Pasquill 1961 Gifford 1960 which appear in the Workbook of Atmospheric Dispersion Estimates Turner 1970 The subroutines used to determine the open countryside parameter values are the same as in the UNAMAP programs MPTER and PTPLU Pierce and Turner 1980 Pierce et al 1982 Chico and Catalano 1986 Plume Rise Plume rise from point sources is calculated using the methods of Briggs 11 1969 1971 1972 1974 1975 Although the plume rise from point sources
36. downwash gradual plume rise and buoyancy induced dispersion The user also specifies types of sources and those that are significant receptor configuration characteristics of emission sources and meteorological inputs Whether the run is part of a segmented run outputs desired and use of the default feature are also specified by the user The default feature sets parameters and options for regulatory application final plume rise and momentum plume rise are used as are buoyancy induced dispersion and stack tip downwash Calm wind conditions are treated following the Calms Processor CALMPRO User s Guide U S EPA 1984 Both point and area sources are considered by the model Their particulars can be included in the run stream or they can be read from disk or tape files Source coordinates and parameters must be given as well as emission rates A total of 250 point sources and 100 area sources are permitted Of these up to 25 point sources and 10 area sources can be labeled significant to obtain their contribution at a receptor separately As with the data on emissions the meteorology can be read as part of the input stream from a file processed by the program RAMMET or froma file having the format of RAMMET Surface parameters and mixing height must be present for each simulation hour the meteorological file is of a variable length from one hour to one year Receptors can be specified by the user or they can be generated by
37. e end of receptor input ACTION Modify the input as needed MESSAGE NO RECEPTORS HAVE BEEN CHOSEN DESCRIPTION Either user input or program generated receptors are required Neither type was specified ACTION Correct the input stream to specify receptors MESSAGE DAYS DO NOT MATCH IDAY x IDAYS Y DESCRIPTION If the run is part of a segmented run the starting day must match the day in the prior run ACTION Modify the input stream to effect a match 68 MESSAGE DESCRIPTION ACTION MESSAGE Oo ACTION MESSAGE DESCRIPTION ACTION MESSAGE DESCRIPTION ACTION ESCRIPTION RUN TERMINATED CAN NOT WRITE FILES OPTIONS 41 OR 42 WHEN HAVING RAM GENERATE RECEPTORS FOR EACH AVERAGING PERIOD OPTIONS 15 16 17 Options 41 or 42 are not compatible with options 15 16 17 Modify the input stream to ensure compatibility DATE ON MET TAPE x DOES NOT MATCH INTERNAL DATE y The Julian date calculated by RAM does not match the date in the input meteorological tape Verify the proper data sequence in the input meteorology HOUR x IS NOT PERMITTED HOURS MUST BE DEFINED BETWEEN 1 AND 24 The hour specified is other than 1 24 Modify the input to conform to the hour stipulation required by RAM DATE BEING PROCESSED IS x DATE OF HOURLY POINT EMISSION RECORD IS y PLEASE CHECK EMISSION RECORDS In the point emission record in process the date does not
38. he actual page numbers in your copy of the document may differ from those indicated in the Table of Contents depending on the kind of printer as well as the available type font that is used to print your copy of this document vi The abridged version of the RAM user s guide was composed by Computer Sciences Corporation Research Triangle Park North Carolina for the SCRAM BBS vii ACKNOWLEDGMENTS The authors wish to express their appreciation to Russell Lee for helpful comments regarding aspects of the work presented here Special mention is made to Mr John Crouch who assembled and corrected the text Most of the text presented in this document was excerpted from publications dealing with RAM and MPTER over the past few years Support of Aerocomp by the Environmental Protection Agency Contract No 68 02 4106 is also gratefully acknowledged viii EXECUTIVE SUMMARY The RAM algorithm is a Gaussian plume dispersion model that calculates short term pollutant concentrations from multiple point and or area sources at a user specified receptor grid in level or gently rolling terrain Pollutants considered are relatively non reactive such as sulfur dioxide and suspended particulates Both urban and rural Situations can be simulated In the rural mode those proposed by Briggs based on the work of Pooler McElroy are used Plume rise is calculated following the methods of Briggs and both buoyancy rise and momentum rise are included F
39. ification of the meteorological tape to be used For tapes generated by the National Climatic Data Center this will normally be the surface station number ISFCYR FF Year of surface meteoro logy data IMXD FF Upper air Station Identifier IMXYR FF Year of mixing height data 2 digits 56 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type and variable Column Format Variable description Units 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 RAM RECORD TYPE 14 3 variables 7 values This record is used with Option 18 input of polar coordinates if the user chooses to input receptor positions according to a radial distance from a coordinate source Record type 14 RADIL T FF One to five radial dis tances user units RADIL I is one to five radial distances with the remaining distances entered as zeros centered on any location Each radial distance generates 36 receptors at each radial distance at azimuths of 10 to 360 degrees CENTX FF East coordinate about which radials are centered user units CENTY FF North coordinate about which radials are cen tered user units RAM RECORD TYPE 15 3 variables If Option 14 user specifies receptor coordinates is used there will be one record for each receptor that the user specifies Record type 15 RNAME I 1 8 2A4 8 digit alphanumeric stati
40. inates of receptors by specifying up to five radial distances To account for variability in emission rates with time in order to simulate emissions most accurately it is possible to enter new emission rates for each of the sources for each simulated hour using Option 9 and or Option 10 In order to employ this option emissions for each source must have been determined and written on two tape or disk files one for point sources and one for area sources with one record for each hour that is to be simulated The emission information from RAM is still required and must be a normal emission rate in order that the exit velocity of the source can be scaled up or down in proportion to the hourly emission rate Also all permanent information about sources such as coordinates physical stack height and diameter are furnished on record type 8 Meteorological Data and RAMMET As noted previously meteorological data for RAM can be furnished in either of two ways 1 records containing the meteorological data for each simulated hour one record per hour or 2 magnetic disk or tape output from program RAMMET Meteorological data output from RAMMET may be used as input to RAM RAMMET requires one year of hourly surface observations and one year plus two days of daily maximum and minimum mixing height data The hourly surface data normally on magnetic tape in card image format CARD DECK 144 can be obtained from the National Climatic Center in Ashevi
41. ing that area sources at various distances on a line directly upwind from the receptor are representative of the sources at those distances that affect the receptor This assumption is best fulfilled by gradual rather than abrupt changes in area emission rates from adjacent area sources The narrow plume simplification is considered in more detail in the next section Meteorological Conditions Representative of the Region The meteorological input for each hour consists of a value for each of the five parameters wind direction wind speed temperature stability class and mixing height all of which should be representative of the entire region containing the sources and receptors Mixing height is required only if the atmospheric stability is neutral or unstable Steady state Calculations are made as if the atmosphere had reached a steady state Concentrations for a given hour are calculated independently of conditions for the previous hour s Concentration Sum of Contributions The total concentration for a given hour for a particular receptor is the sum of the estimated contributions from each source Vertical Stability Except for stable layers aloft which inhibit vertical dispersion the atmosphere is treated as a single layer in the vertical with the same rate of vertical dispersion throughout the layer Complete eddy reflection is assumed both from the ground and from the stable layer aloft given by the mixing layer Mixing
42. iptions that follow are called by RAM to perform specific tasks ANGARC JMHREC JMHHON Pal s RCON ore 2 JMH54 This function determines the appropriate arctan of the east resultant wind component over the north resultant wind component with the resulting angle between OE and 360E This subroutine and entry point GREC called by RAM determine receptor locations downwind of significant sources based upon the resultant meteorological conditions for the averaging period usually 3 or 24 hours Plume rise and effective height of emission are calculated The distance of the maximum concentration is determined as a function of the stability and the effective height of emission in order to locate the position of a receptor Two receptors are generated for each significant point source one at the expected distance of maximum concentration and one at twice this distance One receptor is generated for each significant area source at the expected distance of maximum concentration This subroutine called by RAM generates additional receptors within a specified area in order to give adequate coverage of that area with the minimum number of receptors Receptors are placed equidistant from nearby receptors resulting in a honeycomb array The distance between receptors is an input to the main program Proposed honeycomb receptors located closer than half this distance to any other receptor are not included This subroutine calc
43. is not available in RAM outside of the default option If not using the default calms are treated as 1 0 m s winds Summary The closer the situation to be simulated agrees with the assumptions Stated above the greater the expectation of reasonable results The narrow plume simplification is most reasonable for situations where there are no great variations in area emission rates for adjacent area sources The higher the effective height of a point source the greater is the chance for poor results since actual directional shear in the atmosphere not included in the algorithm will cause plumes to move in directions different from the direction input to the model Also the higher the source height the greater is the potential for encountering layers in the atmosphere having dispersion characteristics different from those being used As stated above it is necessary to properly consider variations in emissions 14 Reliable meteorological inputs are also necessary The light wind situation is most likely to violate assumptions since variations in the flow over the region are likely to occur and the slower transport may cause buildup of pollutants from hour to hour Unfortunately these are the conditions that are likely to be associated with maximum 3 hour and 24 hour concentrations in urban areas These light wind situations do not conform to the assumptions of Gaussian steady state models The calms processing segment in RAM takes into a
44. l products does not constitute endorsement or recommendation for use AFFILIATION Mr Joseph A Catalano is the Technical Director of Aerocomp Inc Costa Mesa California Mr D Bruce Turner is Chief of the Environmental Operations Branch Meteorology amp Assessment Division and Ms Joan H Novak is Chief Data Systems and Analysis Branch of the U S Environmental Protection Agency Research Triangle Park North Carolina Mr Turner and Ms Novak are on assignment from the National Oceanic and Atmospheric Administration U S Department of Commerce PREFACE TO THE ABRIDGED VERSION This abridged version of the most recent RAM User s Guide has been created for users of the Support Center for Regulatory Air Models Bulletin Board System SCRAM BBS It is stored in Word Perfect format on the SCRAM BBS in the Regulatory Models Section under Documentation The availability of this and other model user s guides on the SCRAM BBS will facilitate the immediate user of models which have been downloaded from the SCRAM BBS without having to wait for delivery of the complete user s guide Although some portions of the User s Guide have been omitted to save Space nothing was omitted that is needed by the user to run the model Nevertheless the user is strongly encouraged to obtain the complete user s guide from NTIS NTIS Document Numbers for model user s guides can be found on the SCRAM BBS in the Models Documents Section under News Note that t
45. lle NC All required surface data for each hour must be included on the tape therefore all data flagged as missing by RAMMET must be accounted for determined and included in the data set before proceeding The data used from the surface observation tape for each hour are year month day hour cloud ceiling code wind direction wind speed temperature and opaque cloud cover 62 The mixing height data is expected in card image format for RAMMET one card per day containing the minimum and maximum mixing height for that day When using meteorological data from RAMMET there are greater restrictions on certain input parameters than there are when meteorological data from cards are used Using RAMMET data one averaging time must be used and it must be evenly divisible into 24 The start hour must be 1 Periods must be sequential in the time series The starting day may be any day included in the file The file will be positioned to the correct start day One averaging time must be used when using meteorological data with the run stream but it can be any integer value from 1 to 24 The start hour can be any hour from 1 to 24 Day and hour values must be entered correctly and must be in sequence within each period Data from period to period needs to be in sequence for example calculations for two 2 hour periods can be done first day 181 hour 24 followed by day 182 hour 1 63 SECTION 10 EXECUTION OF THE MODEL AND SAMPLE TE
46. n of the flow over the source area considered A single mixing height and a single stability class for each hour are assumed representative of the area The use of RAM is restricted to relatively non reactive pollutants and is usually applied to sulfur dioxide and total suspended particulates Emission information required of point sources consists of source coordinates emission rate physical height stack diameter stack gas exit velocity and stack gas temperature Emission information required of area source squares consists of south west corner coordinates source side length total area emission rate and effective area source height Output consists of calculated air pollutant concentrations at each receptor for hourly averaging times and a longer averaging time specified by the user Contributions to the concentration in the two categories point sources and area sources are also given on output The contributions to the concentration from specific point and area sources can be obtained at the option of the user Computations are performed hour by hour as if the atmosphere had achieved steady state condition Therefore errors will occur where there is a gradual buildup or decrease in concentrations from hour to hour such as under light wind conditions Also with light wind conditions the definition of wind direction is likely to be inaccurate variations in the wind flow from location to location in the area are quite probable
47. ncy dominated if the difference is less than T plume rise is assumed to be momentum dominated see below The crossover temperature difference is found by setting Briggs 1969 p 59 Eq 5 2 equal to the combination of Briggs 1971 p 1031 Eqs 19 6 and 7 and solving for T For F less than 55 Te 0027 Wart Tod 4 For F equal to or greater than 55 T 0 00575 v T d 5 Unstable or Neutral Buoyancy Rise For situations where T exceeds or is equal to T as determined above buoyancy is assumed to dominate The distance to final rise x in kilometers is determined from the equivalent of Briggs 1971 p 1031 Eq 7 and the distance to final rise is assumed to be 3 5x where x is the distance at which atmospheric turbulence begins to dominant entrainment For F less than 55 x 0 049 FS 6 For F equal to or greater than 55 x 0 119 FS 7 The plume height H in meters is determined from the equivalent of the combination of Briggs 1971 p 1031 Eqs 6 and 7 For F less than 55 H n 21 425 F uth 8 For F equal to or greater than 55 H h 38 71 F u h 9 Unstable or Neutral Momentum Rise For situations where the stack gas temperature is less than the ambient air temperature it is assumed that the plume rise is dominated by momentum Also if T is less than T from Eq 4 or 5 it is assumed that the plume rise is dominated by momentum The plume height is calculated from
48. ner 1970 DILUTION BY THE WIND Emissions from continuous sources are assumed to be stretched along the direction of the wind by the speed of the wind Thus the stronger the wind the greater the dilution of the emitted plume To approximate the increase in wind speeds with height from point of measurement to stack top a power law increase with height is used The exponent used is a function of stability DISPERSION RESULTS IN GAUSSIAN DISTRIBUTED CROSS SECTIONS The time averaged concentration distributions through a dispersed plume resulting from a continuous emission from a point source or an area element are considered to be Gaussian in both the horizontal and vertical directions Modification of the vertical distribution by eddy reflection at the ground or at a stable layer aloft is considered This eddy reflection is calculated by a folding back of the portion of the distribution that would extend beyond the barrier if it were absent This is equivalent to a virtual image source beneath the ground or above the stable layer STEADY STATE CONDITIONS Concentration estimates are made for each simulated hourly period using the mean meteorological conditions for that hour as if a steady state condition had been achieved Steady state Gaussian plume equations are used for point sources and the integrations of these equations are used 16 for area sources 17 SECTION 5 TECHNICAL DESCRIPTION CONCENTRATION SUM OF INDIVIDUAL
49. nt throughout the entire depth of each plume can be approximated by RAM This is accomplished by an exponential decrease with travel time from the source The input parameter is the time expected to lose 50 half life of the emitted pollutant RAM does not have the capability to change this parameter value during a given run If the loss to be simulated takes place through the whole plume without dependence upon concentration then the exponential loss may provide a reasonable simulator if the loss rate is realistic However if the loss mechanism is selective such as impaction with features on the ground reactions with materials on the ground or dependence on the concentration in a given small parcel of air requiring consideration of contributions from all sources to this parcel the loss mechanism built into RAM will not be adequate Topographic Influences 12 RAM is designed for application over level or gently rolling terrain where the assumption of a flat plane used in the algorithm is reasonable Dispersion parameters for the urban algorithms are representative of surface roughness over urban areas z 1m Dispersion parameters for the rural algorithms are representative of surface roughness over rural areas z zx 0 1 m The algorithms in RAM have no topographical influences incorporated and some difficulties might be expected in attempting to use the model in terrain situations Under unstable conditions plumes may tend to
50. o be from disk files outputs either go to disk or printer Options and program control are read from FORTRAN unit 5 processing is then controlled through specifications in this file If so specified in the control file meteorology and emissions can be obtained from units 11 15 and 16 respectively The program uses two temporary files for intermediate work but they are not temporary in the JCL sense i e they are not deleted at the end of the job step and should be deleted by the user when they are no longer needed As the program calculates concentrations they are averaged and written to units 1 10 12 and 13 Tabular output is written to unit 6 which is usually the default for printed files Preprocessing subroutines are used to initialize variables and are called to determine dispersion parameter values as functions of stability class and source receptor distance The data produced are coefficients and exponents for the various ranges of effective height of emission and are used to determine maximum Pu Q relative concentration normalized for wind speed for point sources and distance to maximum concentration for point and area sources as functions of stability class and effective height of emission Other subroutines process the emission data Their principal task is to set up the area source map array The area source map array provides correspondence between locations referred to by coordinates and area source number Other tasks
51. on identification RREC 9 18 F10 3 East coordinate of receptor user units SREC 19 28 F10 3 North coordinate of receptor user units 57 Both coordinates of receptors should be positive Receptors may be either inside or outside the area source region A record with ENDR in columns 1 4 signals that the receptor list has been completed 58 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type and variable Column Format Variable description Units 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 RAM RECORD TYPE 16 5 variables 5 values This record is needed only if Option 17 is used to generate additional receptors for area coverage Record type 16 GRDSPU FF Grid spacing between honeycomb receptors user units HRMIN FF Minimum east coordinate user units HRMAX FF Maximum east coordinate user units HSMIN FF Minimum north coordinate user units HSMAX FE Maximum north coordinate user units If HRMIN HRMAX HSMIN HSMAX are entered as zero the boundaries considered for these receptors will be the same as those of the area source region However if no area sources are input and if honeycomb receptors are to be generated this record must have boundaries included to provide the bounds for receptor generation RAM RECORD TYPE 17 2 variables This record is needed only if Option 39 is u
52. ons where uniform mixing is not assured F lt 1 6L the following equation is used P Qg 9 2BF F u 28 This equation incorporates multiple eddy reflections from the ground and the base of the stable layer aloft Concentrations from Area Sources The total concentration at a receptor from the two dimensional area source distribution is calculated using the narrow plume simplification discussed by Gifford and Hanna 1971 This simplification is assumed because the upwind zone of influence affecting a receptor an upwind oriented point source plume is normally quite narrow in comparison with the characteristic length scale for appreciable changes in the magnitude of the area source emission rate itself Under these circumstances the two dimensional integral that expresses the total area source contribution to concentration at a receptor can be replaced approximately 25 by a one dimensional integral This integral involves only knowledge of the distribution of the area source emission rates along the line in the direction of the upwind azimuth from the receptor location the meteorologically dependent function that specifies the crosswind integrated concentration in the Gaussian plume from a point source In using this area source technique Gifford and Hanna assumed area source emissions at ground level allowing integration upwind to be accomplished analytically In RAM the area sources are allowed to have an effecti
53. or point sources concentrations are determined using distance crosswind and distance upwind from the receptor to each source For area sources the narrow plume simplification of Gifford and Hanna is used with the modification that the area sources are not at ground level but have an effective height Inputs to the model are a set of options selected by the user source parameters meteorological data and receptor information Using the hourly meteorology concentrations are calculated for receptor locations either specified by the user or generated by the program Emissions and source parameters for point or area sources are required inputs The meteorological data baase and hence the simulation can vary from one hour to one year Concentrations for 5 averaging periods can be computed For long term runs such as a year a high five tabulation can be obtained to determine the highest and second highest concentrations at each receptor for each of five averaging periods Receptors can be specified by the user or they can be generated by the program If they are input by the user receptor name as well as coordinates may be provided on input For model execution the user specifies parameters and options needed for the application Required parameters are type of pollutant number of sources averaging period s power law wind profile exponents and whether the urban or rural mode is to be used Options are included for the treatment of stack tip
54. r quality from point and area sources Effects of either control strategies or tactics for specific short term periods may be examined by users The expected effect of a proposed source or sources can also be determined The spatial variation in air quality throughout the urban rural area or in a portion of the area for specific periods can be evaluated readily In a forecast or predictive mode such as over a 24 hour period the algorithm can assist in locating mobile or portable air samplers and can assist with emission reduction tactics Successful use of RAM in the forecast mode is contingent on the validity of the algorithm assumptions and the ability to accurately forecast both the input meteorological parameter values and the input emission parameter values The model has the following added features urban dispersion coefficients recommended by Briggs see Figure 7 and Table 8 of Gifford 1976 wind profile exponents for urban and rural situations optional treatment of calm conditions following methods developed by the EPA 1984 Stack tip downwash using the algorithm of Briggs 1974 momentum plume rise to treat momentum dominated plumes as suggested by Briggs 1969 buoyancy induced dispersion following the method of Pasquill 1976 and a default option primarily for regulatory application of the model These features were added to satisfy the requirements outlined in Guideline on Air Quality Model
55. r receptors by specifying coordinates IOPT 15 15 I1 RAM generates receptors downwind of significant point sources IOPT 16 16 I1 RAM generates receptors downwind of significant area sources IOPT 17 J67 I1 RAM generates honeycomb array of receptors to cover specified area RAM generates a honeycomb array of receptors placed equidistant in staggered rows over a specified area This insures good area coverage Candidate receptor positions are checked against other receptors either input or generated by other options of the program and if the distance between the proposed receptor is less than one half the normal distance between honeycomb receptors then the candidate receptor is not added to the list The boundaries of the area to be covered by these receptors are specified by the user IOPT 18 18 I1 Input radial distances to generate polar coordinate receptor array 41 36 receptors for each distance IOPT 19 19 Il Not used Printed output is controlled by the options that follow Options 20 through 36 are all options to omit output In the program default most of these options to omit output are used since some of the options can generate large amounts of printed output 42 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type and variable Column Format Variable description Units 44444444 4444444444 44444444 44444404 4444444444 444444444444444444 444444444 4
56. rces along the line This is accomplished by finding the nearest and farthest distance of each source along the path and calling subroutine JMHPOL for each distance JMHPOL This subroutine called by JMHARE interpolates for a given distance from the values in the tables generated by subroutine JMH54 This yields the effect of an area source at the given height extending upwind to this distance RANK This subroutine arranges concentrations of various averaging times into tables of the highest five concentrations for each receptor for each averaging time high five tables OUTPT This subroutine produces output concentrations in micrograms per cubic meter for each hour for significant sources and for the summaries OUTAV This Subroutine called by RAM gives concentrations for the averaging period Contributions and or summary information are also generated by OUTAV PROCESSOR PROGRAM RAMMET If option 8 specifies that meteorological data should be expected from a file a peripheral program RAMMET can be used to generate the file RAMMET processes meteorological data for one year The data input consists of hourly meteorological records in the standard card format 144 of the National Climatic Data Center and twice a day estimates of mixing height minimum and maximum Hourly stability class is determined using 33 the objective method of Turner 1964 based on Pasquill s technique Pasquill 1961 Shifts by only one stability class
57. rise is calculated and calms are treated according to methods developed by the EPA 1984 These are discussed next 13 Optional Treatment of Calm Conditions When the default option is exercised calm conditions are handled according to methods developed by EPA A calm hour is indicated in the preprocessed meteorological data as an hour with a wind speed of 1 0 m sec and a wind direction the same as the previous hour When a calm is detected in the meteorological data the concentrations at all receptors are set to zero When calculating a multiple hour average concentration the sum of the hourly concentrations is divided by the number of hours less the number of calm hours provided that the divisor used in calculating the average is never permitted to be less than 75 percent of the averaging time being considered This results in the following 3 hour averages are always determined by dividing the sum of the hourly contributions by 3 i e no change from prior methods 8 hour averages are calculated by dividing the sum of the hourly contributions by the number of non calm hours or 6 whichever is greater 24 hour averages are determined by dividing the sum of the hourly contributions by the number of non calm hours or 18 whichever is greater and period of record averages are calculated by dividing the sum of all the hourly contributions by the number of non calm hours during the period of record This calms procedure
58. rise over terrain obstructions under stable conditions leveled off plumes may remain at nearly the same mean sea level height but may be expected to alter the plume path in response to the terrain features resulting in a different wind direction locally than that specified for the region Fumigation Fumigation is a transient phenomenon that eliminates the inversion layer containing a stable plume from below causing mixing of pollutants downward and resulting in uniform concentrations with height beneath the original plume centerline This phenomenon is not included in the calculations made by RAM Conditions specified for each hour are calculated as if a steady state had been achieved Default Option A default option is a feature of the model which facilitates compliance with regulatory requirements For either rural or urban situations exercising this option overrides other user input selections and results in the following final plume rise is used gradual or transitional plume rise is not used for plume height but it is used to calculate the magnitude of the buoyancy induced dispersion buoyancy induced dispersion is used stack tip downwash is considered default urban or rural wind profile exponents are used as given in Table 1 default vertical potential temperature gradients for stable conditions are used a decay half life of four hours for S0 in urban mode is used otherwise no decay momentum plume
59. s 1975 p 96 Eqs 48 and 59 X 0 0020715 u h s7 13 The plume height is determined by the equivalent of Briggs 1975 p 96 Eque 59 H h 2 6 F u h s 14 The stable buoyancy rise for calm conditions Briggs 1975 pp 81 82 21 is also evaluated ES eb eke OP ga 15 The lower of the two values obtained from Eqs 14 and 15 is taken as the final effective height Stable Momentum Rise When the stack gas temperature is less than the ambient air temperature it is assumed that the plume rise is dominated by momentum If T is less than T as determined by Eq 12 it is also assumed that the plume rise is dominated by momentum The plume height is calculated from Briggs 1969 p 59 Eq 4 28 H h 1 5 v2 d T 4 T u h e s7 16 The equation for unstable or neutral momentum rise 10 is also evaluated The lower result of these two equations is used as the resulting plume height All Conditions Distance Less than Distance to Final Rise Gradual Rise Where gradual rise is to be estimated for unstable neutral or stable conditions if the distance upwind from receptor to source x in kilometers is less than the distance to final rise the equivalent of Briggs 1971 p 1030 Eq 2 is used to determine height H h 160 FY x70 17 This height is used only for buoyancy dominated conditions should it exceed the final rise for the appropriate condition the final rise is su
60. s Revised EPA 1986 The default option is designed as a convenience for the user to help avoid inadvertent errors in setting the appropriate switches for regulatory use The reader is cautioned to refer to the current regulatory guidance contained in the Guideline on Air Quality Models Urban and Rural Modes The urban dispersion parameter values are those recommended by Briggs and included in Figure 7 and Table 8 of Gifford 1976 They have been coded in a subroutine which yields dispersion coefficients as functions of atmospheric stability and downwind distance Separate urban and rural default wind profile exponents are used in the model These exponents are used by the model when the user exercises the default option or when they have not been provided on input The rural exponents correspond to a surface roughness of about 0 1 meters the urban exponents result from a roughness of about 1 meter plus urban heat release influences For a more detailed discussion of wind profiles the reader is referred to Irwin 1979 ALGORITHM ASSUMPTIONS Gaussian Plumes Calculations of concentrations from point sources are made for emissions diluted according to the mean wind speed assuming that the time averaged plumes over 1 hour periods have Gaussian normal distributions perpendicular to the plume centerline in the horizontal and vertical Narrow Plume Simplification Calculations of concentrations from area sources are made by consider
61. sed i e this run is part of a segmented run Record type 17 IDAY FF Number of days previously processed 59 LDRUN EE Last day to be processed in this run 60 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type and variable Column Format Variable description Units 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 RAM RECORD TYPE 18 8 variables 8 values Meteorology Used if Option 8 0 Record type 18 JYR FF Year of meteorology data 2 digits DAY1 FF Julian day of meteoro logy data JHR FF Hour of meteorology data IKST EF Stability class for this hour QU FF Wind speed for this hour m sec QTEMP FF Ambient air temperature K for this hour QTHETA FF Wind direction for this deg hour degrees azimuth from which winds blows QHL FF Mixing height for this hour 61 Emissions Data In the emissions file either point sources area sources or both may be included When both types are included the user still has the option to select one or both source types Any rectangular coordinate system is allowed provided that the positive quadrant is used that is all coordinate values are positive and a single coordinate system is used for both point and area sources The scale of the coordinate system is arbitrary An option is also available in which the user can specify radial coord
62. such as ranking sources according to set criteria are also accomplished RAM expects hourly meteorological input data including mixing height and Stability class This and other values can be entered in the input stream or from a preprocessed file The auxiliary program RAMMET can process raw meteorological data into the needed format using hourly surface data and mixing heights from the National Climatic Data Center Input consists of one year of surface data one observation per hour and one maximum and one minimum mixing height per day RAMMET determines hourly stability and performs interpolations to estimate hourly mixing 30 heights The output data are organized to produce a single record for each day The output subroutines are OUTPUT and QOUTAV OUTPUT provides hourly concentrations in micrograms per cubic meter including the contributions from significant point sources along with a summary table OUTAV provides the same information for the averaging period PROGRAM MODULES After initialization the flow is governed by three loops calendar days averaging time and hours A minimum of one hour and a maximum of 8 784 hours can be processed by the model A brief description of the main program and subroutines follows MAIN The main program determines Pu Q maxima and distance to the point of maximum for point sources as functions of stability class and effective height of emissions Coefficients and exponents relating these t
63. t s for area source integrations Same number as NHTS RAM RECORD TYPE 11 1 variable 1 or 2 values This record is required only if record type 10 is used Record type 11 BPH FF Breakpoint heights between m area source heights These values are to be used as boundaries between the specified area source heights used for calculations If only one area source height is 54 to be used only one BPH value is entered it should be greater than any area source height of the area source data If NHTS is 2 the single value for BPH should be between the two HINT values If NHTS is 3 and the three HINT values are for example 15 25 and 35 the two values for BPH might be 20 and 30 RAM RECORD TYPE 12 2 variables 1 to 11 values This record is required only if Option 12 is used i e user specifies significant area sources 55 44444444444 4444444444444 4444444404 4444444444 444444 444444444444 444444444 4 Record type and variable Column Format Variable description Units 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type 12 INAS 1 3 I3 Number of user specified significant area sources max 10 MAS 4 33 13 INAS area source numbers the user wants to consider significant RAM RECORD TYPE 13 4 variables Used if Option 8 0 meteorological data will be input on Unit 11 Record type 13 ISFCD FF Surface Met Station Identifier ISFCD is a 5 digit ident
64. ter values F and F are determined as functions of this upwind distance x and stability class The terms below are used in the equations that follow g exp 0 5y F g exp 0 5 z H F exp 0 5 z H F 7 4 g E exp 0 5 z H 2NL F 7 N 4 exp 0 5 z H 2NL F This infinite series converges rapidly and evaluation with N varying from 4 to 4 is usually sufficient where H effective height of emissions meters L mixing height the top of the unstable layer meters y crosswind distance meters Z receptor height above ground meters 24 F standard deviation of plume concentration distribution in the horizontal meters F standard deviation of plume concentration distribution in the vertical meters One of three equations is used to estimate concentrations under various conditions of stability and mixing height The equation P Qg 9 2BF F u 26 is used for stable conditions or for unlimited mixing where P ground level concentration from a single point source g m and Q point source emission rate g sec In this equation eddy reflection at the ground is assumed For unstable or neutral conditions where vertical dispersion is great enough that uniform mixing is assured F gt 1 6L beneath an elevated inversion the following equation is used P Og FyLu 2B 27 If H or z is above the mixing height P 0 For unstable or neutral conditi
65. the input stream MPS THE INPUT SIGNIFICANT SOURCE NUMBER WAS FOUND TO EQUAL ZERO USER CHECK INPUT DATA total The number of significant sources exceeds the Significant sources specified Verify consistency of significant sources in the input stream THE INPUT LIMIT OF MAXIMUM DISTANCE FOR AREA INTEGRATION x CONVERTS TO y KM WHICH EXCEEDS STORAGE LIMITATIONS UP TO 116 KM DISTANCES ARE ALLOWED The maximum distance for area exceeded source integration was Modify the limit such that the distance does not exceed 116 km ERROR IN SPECIFYING SIGNIFICANT POINT SOURCES 67 DESCRIPTION The significant point sources were not input properly ACTION Verify the input stream and correct as needed MESSAGE DISAGREEMENT OF IDENTIFIERS SURFACE DATA FROM CARD STATION x YEAR x FROM MET FILE STATION y YEAR y MIXING HEIGHT DATA FROM CARD STATION x YEAR x FROM MET FILE STATION y YEAR y DESCRIPTION Header information in the meteorological file is not in agreement with that specified in the input stream ACTION Modify the input stream or replace the meteorological data set to effect a match MESSAGE AAXUSER EITHER TRIED TO INPUT MORE THAN 180 RECEPTORS OR ENDR WAS NOT PLACED AFTER THE LAST RECEPTOR CARD RARAASEAE XE GUD LON TERMENATED AAS SOR DESCRIPTION The maximum number of user specified receptors is 180 and a record with ENDR in columns 1 4 is required to signify th
66. ulates concentrations from point sources Subroutines RCON and SYZ ENTRY point in SYSZ are called to complete the computations This subroutine called by PT calculates P Q the relative concentrations from point sources This subroutine calls SYZ This subroutine called by RCON calculates the standard deviation of the concentration in the y and z directions It employs the Briggs urban dispersion parameters for urban conditions and the Pasquill Gifford parameters for rural conditions This subroutine called by RAM generates tables of Pu q relative concentration normalized for wind speed from area sources that extend from a receptor to various upwind distances A table is 32 produced for each area source height One to three heights can be used This subroutine calls subroutine JMHCZ JMHCZ This subroutine called by JMH54 calculates concentrations from infinite crosswind line sources at a distance x upwind from a receptor To obtain the vertical dispersion parameter value F subroutine SIGZ is called SIGZ This subroutine called by JUMHCZ determines the value of the vertical dispersion parameter F for a given upwind distance of a receptor to the source The parameter values for urban areas are those put into equation form by Briggs The parameter values for rural areas are from Pasquill Gifford JMHARE This subroutine performs the integration along the line upwind from the receptor to obtain the effect of all area sou
67. umed that the input height of emission is the effective height for all wind speeds RAM RECORD TYPE 9 2 variables This record is required only if Option 11 is used i e the user will specify significant point sources Record type 9 INPT 1 3 FS Number of user specified significant sources The maximum number of user specified significant point sources is 25 this number must be non zero MPS I 4 78 3 INPT point source numbers the user wants considered Significant max 25 There will be as many sources in this list as indicated in INPT RAM RECORD TYPE 10 4 variables 4 values Information for area sources This record is required only if Option 6 is employed user will input area sources 53 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type and variable Column Format Variable description Units 44444444 444444444 444444444 44444404 4444444444 444444 444444444444 444444444 4 Record type 10 FH FF Fraction of area source height which is physical height XLIM FF Distance limit on inte gration for area source user units The distance XLIM should be equal to or exceed the greatest possible distance from a receptor including receptors generated by RAM to the farthest corner of the area source region for this run but cannot exceed 116 kilometers NHTS FF Integer number of heights to be used for area sources min 1 max 3 HINT FF Heigh
68. ve height requiring the integration to be accomplished numerically Internal tables of integrations for one to three effective area source heights are calculated at the beginning of each simulated hour using the specific meteorological conditions for that hour The total concentration from all area sources is determined by performing the integration piecewise over each source in the upwind direction from the receptor until the farthest boundary of the source region is reached 26 SECTION 6 VERIFICATION RUN A sample input data set and the resulting output are distributed with the model code for verification purposes A detailed discussion of that data set can be found in Section 6 of the complete User s Guide for RAM which is available from NTIS 27 SECTION 7 USES OF RAM RAM simulates pollutants from point and area sources in urban or rural settings over periods of one hour to one year The meteorological data can be entered on cards with one card for each simulated hour or on magnetic media by using option 8 General emission information can also be on the input stream or from disk or tape files using option 9 or 10 Point and area sources are specified by options 5 and 6 The locations of receptors may be specified by the user option 14 The use of options 15 and 16 to locate additional receptors downwind of significant point and area sources assists in determining locations of maximum concentration Since the resultant wind
69. wo parameters to effective height of emission are determined for various stability and effective height range combinations These coefficients and exponents as well as ones for determining the distance of the maximum concentration downwind from the edge of an area source are calculated for use in the emissions module which processes emission inventory information for later use An important aspect of this is the construction of the area source map array which allows a correspondence between any location in the area source region and the number of the area source at that location All source coordinates in units convenient to the user user units are converted to internal units An internal unit is a length such that any area source side length used in a given run can be expressed as an integer multiple of an internal unit The internal unit is generally equal to the length of the side of the smallest area in the emission inventory The user must determine the internal unit length and specify it in user units Both point and area sources are ranked according to expected impact at ground level The 25 point sources and the 10 area sources with the greatest expected ground level impact are listed Also the total emissions from various physical heights for both point and area sources are listed This helps the user in determining area source heights and the number to be used BRIEF DESCRIPTION OF SUBROUTINES 31 The subroutine and function descr

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