MARS CLIMATE DATABASE 3.0 "ATMEMCD" SUBROUTINE
Contents
1. cones 13 34 1 Berturbed atmosphere istae ee aliene Ge tete ptg te e E pete e dte perd edet 13 5 4 2 Running Meien nin EE 13 ANNEXE MCD CONTENTS sise ie Foe erae ERE E Ee era e eo so Vos ea eoe Ue pa ee PY E EEEE Pep aT Ces Vases re seo ERU anse sed aaie 14 6 1 DATABASE FILE NAMING CONVENTIONS iii sesessaesesceesaeececessseseces sensn nasse etna 14 6 1 1 Atmospheric Database File Naming Convention sise tenente netten entente 14 6 1 2 Orographic Database File Naming Convention ss 15 6 2 DIMENSIONAL REPRESENTATION csessessscsececssssnsecsececesnsesecesssseesescesnneee sesesssuaeececenseeeecensneeecen senseacesesenseesescesneesecscs 15 ODED Definitions cese Rep RO TRIER e RR ete REOR Un ERE HE CR rire ERES 15 6 3 DATA STRUCTURAL REPRESENTATION SUMMARY ccccccssssssecssssececsececesseccessecenseseecsseecessees en sente ne eene erae entes eer aen 16 6 3 1 Meat Paramelers sse et ip teet em ce a re Tel an teer ae Sete 16 6 3 2 Standard Deviation Parameters eee e nee ene eene hne nnn n nnn ases es sense se eiie ases es se enean eret nien 16 6 3 3 FOR POrQmelelsutu eR EM De E M E 17 6 3 4 Oro graphic P rameters iesu tei terne tede Feed eie Pere 17 ACRONYMS DRS EOF GCM GrADS LMD Mars GRAM MCD PC Data Retrieval and Storage System Empirical Orthogonal Functions General Circulation Model Grid Analysis a2. rho EOFS for density ps EOFs for pressure pesmth smooth principal components PC pevar PCs with variance Data Name Longitudinal Latitudinal Vertical Statistical Temporal Dust Structure Structure Structure Structure Structure Scenario o levels 669 times a year normt normu Y Y normv Y normr Y t y y y y u y y y Y y y rho y Y ps y y y y pcsmth pcvar y y 6 3 4 OROGRAPHIC PARAMETERS topogy maps the topographic height on Mars substd standard deviation of the topographic height for computing gravity wave perturbations areoid areoid radius m Data Name Horizontal Structure 5 x 5 topogy Substd N areoid Y
3. mean surface temperatures Other 2D variables co2ice emis radiative fluxes Data Name Horizontal Vertical Temporal Seasonal Dust Scenario Structure Structure Structure Structure 5 x 5 o levels 12 times a day 12 times a year y y y y u y y y y y Y y y Y y y rho y y tsurf 6 3 2 STANDARD DEVIATION PARAMETERS sdt standard deviation temperatures sdu standard deviation eastward winds sdy standard deviation northward winds sdrho standard deviation densities sdps standard deviation surface pressures sdtsurf standard deviation surface temperatures Other 2D variable sdco2ice sdemis Data Name Horizontal Vertical Temporal Seasonal Dust Scenario Structure Structure Structure Structure 3 75 x 3 75 o levels 1 time a day 12 times a year sdt y sdu Y sdv sdrho sdps sdtsurf 6 3 3 EOF PARAMETERS normt normalization factors for temperature normu normalization factors for eastward wind normy normalization factors for northward wind normp normalization factors for pressure normr normalization factors for density is EOFs for temperature u EOFs for eastward wind y EOFs for northward wind
4. sample makefile file containing information required by make is provided The makefile file is adapted to test emcd and mcdgm but it is straightforward to adapt it to your own program by mimicking what is done for test emcd For instance to compile and run test emcd type gt make test emcd test emcd Then just answer the questions In the emcd testcase sub directory a tool to test the accurate performance of atmemcd on your computer is provided Please read the README file for further information ATMEMCD SUBROUTINE INPUTS Name Type description double precision Height in meters above zero datum Mars geoid or areoid see note below xlat double precision Latitude in radians Xlon double precision EAST Longitude in radians Xdate double precision Date IF Xdate gt 0 Earth Julian date see note below IF Xdate 0 Mars xdate INT Ls localtime 100 i e xdate 91 18 means Ls 91 LT 18 00 Dset Character chain Data set name can be any length to specify a full path to any data set It can usually be a blank to get the default data set see note below Scena Integer Dust scenario 1 MGS dust Scenario 2 Viking dust 3 low dust 4 moderate global dust storm 2 5 heavy global dust storm 5 Typper double precision dim 2 Perturbation type to add to the mean values 1 0 none 2 se
5. season 10 Ls 270 300 seas s11 is season 11 Ls 300 330 seas s12 is season 12 Ls 330 360 seas all is the whole year for the Empirical Orthogonal Functions EOF data for the large scale variability model and where type indicates the type of data in the file type me means mean data type sd means standard deviation data type eo means EOF data for large scale perturbations 6 1 2 OROGRAPHIC DATABASE FILE NAMING CONVENTION Three files moutain dat moutain dic and mountain ctl are provided which contain maps of the topographic height on Mars map of the zero datum areoid radius from the center of Mars and sub grid standard deviation of the topographic height The model of surface topography used by MCD is the topography retrieved by the Mars Orbiter laser Altimeter MOLA aboard Mars Global Surveyor Note that the MOLA aeroid is not the same as the DTM zero datum previously used it is usually higher 6 2 DIMENSIONAL REPRESENTATION Each file with the mentioned file naming convention contains a set of variables stored with a specific structural representation which depends on the variable type A summary of the variables type name and dimensional representation is given in section 4 3 for the variables accessed by the atmemcd subroutine For the other variables see RD2 6
6. since the previous version of the database Compared to the previous version of atmemcd V2 3 the main differences are e Dimensions in constants atmemcd h were changed for new database resolution for new horizontal grid now 5 x5 and for increased range in vertical coordinates 6 p ps EOFs now stored on a slightly different latitude grid e New table variables tabfslw tabfslw tabftlw tabftsw were introduced to hold fluxes at surface and top of atmosphere Code added to read these into atmemcd with other mean variables e Changes to arguments to atmemcd Time and date can be provided in Mars time Solar Longitude and local time in addition to Earth date i e Julian dates coputed from time day month year 3 dset special options of s and b have been removed since only one set of dust properties is now suppplied dset still used to choose default link or specify a full path to the data scena and internal variable dust can now take values from 1 to 5 to allow for new default MGS scenario note values of other scenarios have increased by 1 1 MGS dust 2 Viking dust 3 low dust 4 dust storm tau 2 5 dust storm tau 5 The Variable intens has been removed extvar now increased to dimension 25 to allow for extra variables to be returned at positions 15 onwards all variables from v2 3 keep the same index in the extvar vector 1 14 The new Extvar variables are extvar 15 mean surface p
7. to create randomly perturbed atmospheres but only as a mean to globally overestimate or underestimate the profiles of the meteorological variables To generate randomly perturbed atmospheres you must use small or large scale perturbations which take into account some correlation of perturbations in the space and between variables Then when you use the type 5 perturbation you have to keep the same n factor along the whole trajectory to avoid to introduce unrealistic gradients between to consecutive values When you generate a randomly perturbed atmosphere using the large scale perturbations to simulate a trajectory you will have to give the same seed number input for all the points of your trajectory to retain the correlation between these points When using the perturbation due to gravity wave propagation small scale perturbation if you generate a vertical profile the same phase then the seed number must be used for the whole profile If you simulate a trajectory with a high resolution that is with small distance between two consecutive points it doesn t make much sense to reset randomly the phase because it can give huge unrealistic horizontal gradients Then the better is to hold the phase constant that is hold the same seed number for all the trajectory Of course if you use the large and small scale perurbations the same seed number must be used for all the points of the trajectory or vertical profile 5 4 2 RUNNING TIME To mak
8. to the MCD data in binary format Files ending with dic are DRS dictionary files Files ending with ctl are provided for accessing the database using a graphical software package GrADS not provided See http grads iges org grads and the User Manual RD2 for more details on GrADS 6 1 1 ATMOSPHERIC DATABASE FILE NAMING CONVENTION The file naming convention for each file with filename extension dic dat and ctl is as follows Data Filename scen seas type filename extension where scen denotes the dust scenario type scen mgs indicates Mars Global Surveyor scenario scen low indicates low dust scenario scen vik indicates Viking Lander scenario data scen ds indicates dust storm with optical depth 2 moderate storm scen ds5 indicates dust storm with optical depth 5 heavy storm where seas denotes the season number seas 501 is season 1 Ls 0 30 seas s02 is season 2 Ls 30 60 seas 503 is season 3 Ls 60 90 seas s04 is season 4 Ls 90 120 seas 505 is season 5 Ls 120 150 seas s06 is season 6 Ls 150 180 seas 07 is season 7 Ls 180 210 seas s08 is season 8 Ls 210 240 seas 09 is season 9 Ls 240 270 seas s10 is
9. value 16 km is used 5 3 ATMEMCD SUBROUTINE OUTPUTS Name Type description Seedout double precision seed number to generate the next perturbed atmosphere Pres double precision pressure Pa Ro double precision density kg m Temp double precision temperature K Ventu double precision zonal wind component Eastward in m s Ventv double precision meridional wind component Northward in m s Meanvar double precision dim 5 mean values array meanvar 1 mean pressure meanvar 2 mean density meanvar 3 mean temperature meanvar 4 mean zonal wind component meanvar 5 2 mean meridional wind component Extvar double precision dim 25 supplementary variables array extvar 1 upper density value kg m extvar 2 lower density value kg m extvar 3 2 density standard deviation kg m extvar 4 random density perturbation kg m extvar 5 scale height H p extvar 6 density scale height H rho km extvar 7 Reserved for future use extvar 8 Reserved for future use extvar 9 Reserved for future use extvar 10 2 mean ground temperature K extvar 11 2 maximum ground temperature K extvar 12 2 minimum ground temperature K extvar 13 density small scale perturbation gravity wave kg m3 extvar 14 orographic height m extvar 15 2 mean surface pressure Pa extvar 16 daily maximum mean surface pressure Pa extvar 17 daily minimum mean s
10. 2 1 DEFINITIONS dust scenario representation see file naming convention seasonal representation see file naming convention horizontal structure grid of 5 x 5 longitude and latitude points 72 longitude points numbered from 0 to 355 and 36 latitude points numbered from 87 5 to 87 5 vertical structure the database vertical coordinate is defined by the sigma levels p Ps where p is the surface pressure and p is the pressure at the altitude of the point Hence o is 1 at the surface and 0 at infinite height temporal representation mean data are stored 12 times per seasonal mean Martian day using prime meridian time not local time Day to day standart deviation data are only stored once per season 669 days in a Martian year splitted in 12 seasons 16 longitudinal structure of the EOF large scale variability model first element in longitude is 180 and last element is 160 Step size is 20 latitudinal structure of the EOF large scale variability model first element in latitude is 77 5 and last element is 82 5 statistical structure series including 72 coefficients calculated over the entire year 6 3 DATA STRUCTURAL REPRESENTATION SUMMARY 6 3 1 MEAN PARAMETERS D mean temperatures tu mean eastward winds ty mean northward winds Other 3D variables q2 Turbulent kinetic energy tho mean densities ps mean surface pressures tsurf
11. MARS CLIMATE DATABASE 3 0 ATMEMCD SUBROUTINE PROGRAMMER S GUIDE F Forget LMD Paris C Hourtolle H Fraysse CNES Toulouse S R Lewis AOPP Oxford ESTEC Contract 11369 95 NL JG SOMMAIRE d aS 1 REFERENCE DOCUMENT UE 1 SCOPE Ur sense 2 INTRODUCTION P H siis 2 DIFFERENCES BETWEEN THE DELIVERED VERSIONS ssscccsssssccessscccssscccsssccscssccsssscccssscces secsecssccssecccenee 2 SOFTWARE PACKAGE D ie 3 INSTALLING UTOR LO Pp 2088 4 RUNNING THE MCD SUBROUTINE MODE e esee ee eee ee to netten sssccesscscccsseccessccesscecens sae t etes e etna 5 5 1 ROLE OF assesses esee seite etie e uses e assesses esses eese ete een EEEE 5 5 2 COMPILING AND RUNNING ATMEMCD iii seeeeessaeccecesssececesesaesee senten sse enean annes 6 ATMEMCD SUBROUTINE INPUTS Rer esses ess e ie eese este seseseeauassessesceceesecessesesussensensss 7 53 ATMEMCD SUBROUTINE OUTPUTS ccccccccsssceceessececessecesecceesscesesseccseecn e tenet erre serae entere 9 54 THE RIGHT USE OF THE ATMEMCD
12. d in files mountain dat dic ctl which is read by subroutine height for instance e The altitude used by the database is thus an areocentric altitude This means that the altitude above the reference aeroidoid is computed as the difference between the areocentric spacecraft radius and the radius to the surface of the reference ellipsoid The radius of the reference ellipsoid is of course computed at the same areocentric latitude of areocentric altitude 7 M Point P pi Mars North Pole Local re Horizontal Areographic Altitude Planet Equatorial Center Plane Areographic Areocentric Latitude Latitude Mars Reference Ellipsoid the spacecraft Julian date A subroutine namely julian in julian F is provided to compute the Julian date given a calendar date day month year hour minute second on Earth Dataset If the datset is not specified i e dset is equal to blank the default path for the data file directory is EMCD DATA Scenario type The different scenarios differ by dust amount and distribution used to create the data files Dust is highly variable on Mars The MGS scenario Scena 1 is thought to represent a moderate realistic Mars Atmosphere without big dust storms The other scenarios are provided to account for the variability on Mars including the possibility of global dust storms Please see the Detailed design document for further 9 informat
13. ded in Annexe A m drs contains the DRS library with some documentation used to read the database files 4 INSTALLING THE MCD See User Manual RD2 section Installation 5 RUNNING THE MCD SUBROUTINE MODE 5 1 ROLE OF ATMEMCD e The subroutine ATMEMCD allows to compute the following basic meteorological variables for atmospheric trajectory computation pressure temperature density wind speed defined by two components the meridional wind positive when oriented from south to north the zonal wind positive when oriented from west to east The radiative fluxes Solar and thermal IR on the ground and at the top of the atmosphere are also available e The values are dependant of the point of the space defined by its altitude latitude and longitude and of the date Meteorological variables are calculated by interpolation in space and day time no interpolation on season from data stored in the MCD e Above the top level of the database currently at sigma level 2 209 107 about 120 km the density and pressure are computed by integration of hydrostatic equation assuming that mean temperature follow a linear transition from the top level to an additional thermosphere level located at sigma level 1 269 10 around 140 150 km above which the temperature is set to 200K The wind components are kept equal to the value in the upper layer of the database e For the variables the subroutine delivers mean
14. e www lmd jussieu fr mars html The data in the MCD have been written using the Data Retrieval and Storage System DRS and a package of FORTRAN77 and C subroutines have been developed to access the data A subroutine mode of the software supplied with the Mars Climate Database MCD has been developed by CNES for trajectory simulation programs RD1 2 4 5 should be consulted for more information on the original source code and description of the method When refered to in an article or a document the references Forget et al 1999 and Lewis et al 1999 RD4 and RD5 should be cited The subroutine computes a set of meteorological variables at a given location and time Several dust scenarios are available The subroutine provides mean values of the variables and allows to account for realistic types of perturbations This version of the database extend up to about 120 km height Above the top model level the subroutine provides relatively realistic values of the meteorological variables e g density by integration of hydrostatic equation assuming a constant thermospheric temperature of 200 K above 140km with a linear transition between the upper database layer 120km and the 140 km level 2 DIFFERENCES BETWEEN THE DELIVERED VERSIONS Difference between Version 3 0 and Version 2 3 of ATMEMCD This corresponds to version 3 0 of the Mars Climate Database See main user manual for further informations about the evolution
15. e amplitude saturates Wave amplitudes at very low speeds are likely to be limited by algorithm which now checks stability anyway 3 SOFTWARE PACKAGE The delivery contains the FORTRAN77 subroutines and data files required to use the Martian Climate Database in subroutine mode for trajectory simulation programs The delivery is composed of 4 directories m emcd contains the file atmemcd F which contains the ATMEMCD main subroutine and all the subroutines or functions it calls the include file constantes atmemcd h 4 the julian F file which contains the subroutine which computes Julian date from calendar date The height F file which contains a subroutine used to make the conversion between height above the local surface height above the zero datum areoid and the distance radius from the centre of the planet The file test emcd F which contains a simple sample program using atmemcd julian and height A makefile used to compile these softwares see user manual A subdirectory testcase containing test cases used to test the accuracy of your installation of the database See user manual As well as the Mars Gram like interface and other tools see main user manual m data contains the full MCD dataset derived from the model GCM run m docs contains the documentation associated to the MCD V3 0 software RD1 et RD2 in postscript and pdf format The complete description of each directory is provi
16. e the computation time faster the data corresponding to the season determined by the input xdate are read and loaded from the database at the first call of the atmemcd This loading is time consuming but these data are loaded once and then used for the further calls as long as the season does not change In the same way only the strictly required data are loaded for example if no perturbation are requested only the mean values are loaded If you have to simulate several trajectories in the same season the best way to save time is to loop on the simulations at the main program level This way the data are not reloaded from the database If you want to simulate trajectories thought different perturbed atmospheres you can use seedout value as new seed number for the next atmosphere If the supplementary variables are requested this implies an extra running time to compute them and to load data used for small and large scale perturbation computation if large and small scale perturbations are not already requested 6 ANNEXE MCD CONTENTS 6 1 DATABASE FILE NAMING CONVENTIONS The data in the MCD have been written using the Data Retrieval and Storage DRS library These binary data can be accessed using the DRS library subroutines provided in mcd drs lib You need files ending with filename extension dic and dat Files ending with ctl are provided but not used by the subroutine ATMEMCD Files ending with dat correspond
17. ed number add large scale 3 seed number add small scale 4 seed number add small and large scale 5 number of standard deviation add n times the standard deviation Invar double precision An argument used to allow control of the variability model features In the current versions invar is the vertical gravity wave wavelength see note below init atm logical true re initialize atmospheric model perturbations see note below Ikey Integer Flag to request extra variable computation 0 extra variables not computed 1 extra variables computed Altitude A subroutine namely height in height F is provided to make the conversion between height above the local surface height above the zero datum areoid and the distance radius from the centre of the planet meters Given any of the above this routine finds the other two according to the value of input index iconv e The model of surface topography used by MCD is the topography retrieved by the Mars Orbiter laser Altimeter MOLA aboard Mars Global Surveyor Note that the MOLA aeroid is not the same as the DTM zero datum previously used it is slighly higher The zero elevation is now defined as the gravitational equipotential surface whose average value at the equator is equal to the mean radius as determined by MOLA This areoid is not defined by an ellipsoid but by a map of radius from the center of the planet provide
18. he altitude z assuming adiabatic motion between those altitudes 2 The large scale perturbation in the Mars Climate Database is represented using a technique that is widely used in meteorological data analysis namely Empirical Orthogonal Function EOF analysis A two dimensional multivariate EOF of the main atmospheric variables surface pressure temperature wind components and density is used which describes correlations in the model variability as a function of both height and longitude 72 EOFs have been retained in the series It allows to capture approximately 95 or greater of the variance Above the top level of the database the perturbation represents a constant percentage of the mean value this percentage is equal to those at the top of the database 3 For the last type of perturbation i e n times the standard deviation the standard deviation is interpolated from the standard deviation values stored in the database Above the top level of the database the standard deviation represents a constant percentage of the mean value this percentage is equal to those at the top of the database 5 2 COMPILING AND RUNNING ATMEMCD A simple program using the atmemcd subroutine as well as the complementary subroutines julian and height named test emcd is provided in the emcd directory You can easily modify it or use part of this code for your own purpose To compile the program the Unix command make can be used For that purpose a
19. ion Note that for the dust storm scenarios the data were only stored in the database when dust storm are most likely to occur that is for seasons 8 10 corresponding to Ls 2 0 300 Perturbations For the small scale or large scale perturbations a seed number input has to be specified as a real double precision The subroutine convert this input in a negative integer for the random number generator When large scale perturbation is requested as long as the seed number remains the same no new random vector is generated and you work with the same correlated perturbed atmosphere When small scale perturbation is requested a new random phase is computed if the seed number input changes or if the displacement in latitude or in longitude is greater than 1 degree because gravity waves are not correlated on large scale low resolution map init atm This logical argument is used to indicate whether a new set of random atmospheric perturbations are required this time It is set to true on first call if using perturbation models It is reset by the subroutine atmemcd to false on output to maintain the same set of perturbations EOF amplitude Gravity Wave phase for next call If uncorrelated perturbations are required then set it to true for each call of the subroutine atmemcd Invar Invar is used in the current version to control the vertical gravity wave wavelength km It should be between 2 and 30 km If set to O the default
20. nd Display System Laboratoire de Meteorologie Dynamique Mars Global Reference Atmospheric Model Mars Climate Database Principal Component REFERENCE DOCUMENT 8 1 802 803 8 4 RD5 MARS CLIMATE DATABASE v3 0 Detailed Design Document S R Lewis M Collins and F Forget MARS CLIMATE DATABASE v3 0 User Manual S R Lewis M Collins F Forget ATMEMCD subroutine programmer s guide F Forget C Hourtolle S Lewis A climate Database for Mars Lewis et al Journal of Geophysical Research 104 24 1777 24 188 1999 Improved General circulation models of the Martian atmosphere from the surface to above 80 km Forget et al Journal of Geophysical Research 104 24 1755 24 176 1999 SCOPE This document is the programmer s guide for the subroutine mode of the Mars Climate Database V3 0 Subroutine ATMEMCD which computes meteorological variables from Mars Climate Database MCD developped by LMD Paris and AOPP Oxford with the support of the European Space Agency The subroutine mode was especially developped by CNES Toulouse for Atmospheric Trajectories Computation purpose but it can be used for various technical or scientifical application 1 INTRODUCTION The MCD is a database of atmospheric statistics compiled from General Circulation Model GCM simulations of the Martian atmosphere These data have been validated through several Mars missions observations The database can be consulted on web sit
21. ressure Pa extvar 16 daily maximum mean surface pressure Pa extvar 17 daily minimum mean surface pressure Pa extvar 18 seasonal std dev surface pressure Pa extvar 19 mean LW flux to surface W m2 extvar 20 mean SW flux to surface W m2 extvar 21 mean LW flux to space W m2 extvar 22 mean SW flux to space W m2 extvar 23 areocentric longitude of Mars Ls deg extvar 24 local solar time hrs extvar 25 prime meridian time hrs e Internal changes The meteorological data retrieved by atmemcd are now interpolated in time of day but not season between database timestep Thus universal time local tile at longitude 0 is now transfered between most subroutines atime routine replaced by mars_ptime which returns a prime meridian time as a real hour number and mcd_time Above the top model level the subroutine provides relatively realistic values of the meteorological variables e g density by assuming a constant thermospheric temperature of 200 K above 140km with a linear transition between the upper database layer 120km and the 140 km level rather than keeping the top model level temperature as before New internal parameters used in grwpb small scale variance routine hmax is now set to 100km since model data is reliable to greater heights than was the case before hmax is the level above which perturbations amplitude is kept constant usat is set to 0 5 m s for windspeeds below usat wav
22. urface pressure Pa extvar 18 seasonal std dev surface pressure Pa extvar 19 mean LW flux to surface W m2 extvar 20 mean SW flux to surface W m2 extvar 21 mean LW flux to space W m2 extvar 22 mean SW flux to space W m2 extvar 23 areocentric longitude of Mars Ls deg extvar 24 local solar time hrs extvar 25 universal prime meridian time hrs Ier integer Error code 0 OK 1 unknown database 2 unknown scenario 3 unknown perturbation type 4 underground object 5 no dust storm for the season 6 impossible to open database file 7 impossible to load data from database 8 undetermined sigma levels Supplementary variables extvar is computed if and only if ikey 1 Otherwise it remains equal to 0 0 Usually these supplementary variables are not used for atmospheric trajectories computation but useful for environmental studies extvar 1 amp extvar 2 upper and lower density Upper and lower densities are equal to Pmean Op pertyw where Pmean is the mean value of density interpolated from MCD data o the density standard deviation interpolated from MCD data and pert the density perturbation due to gravity wave i e small scale perturbation extvar 3 density standard deviation the density standard deviation is computed by interpolation of MCD density standard deviations extvar 4 random density perturbation
23. value 12 This variable is equal to the random component computed for the density large scale perturbation from EOF data stored in MCD extvar 5 amp extvar 6 scale height H pressure and H density these values are evaluated with the formula R Temp g with R equal to 191 2 and g equal to 3 72 extvar 7 amp extvar 8 amp extvar 9 Set to 999 for the moment extvar 10 amp extvar 11 amp extvar 12 respectively the mean surface temperature for the given latitude longitude and day time the daily maximum mean surface temperature and daily minimum mean surface temperature for the season are computed using the MCD data extvar 14 the orographic height is the surface elevation relative to zero datum areoid extvar 19 20 Radiative fluxes W m2 at Shortwave SW solar wavelength below 5 microns and at Longwave LW thermal infrared beyond 5 microns incident to the surface extvar 21 22 Radiative fluxes W m2 at Shortwave SW solar wavelength below 5 microns and at Longwave LW thermal infrared beyond 5 microns emitted to space at the top of the atmosphere Error detection When an error is raised by the subroutine a message is delivered on the standard output and all the outputs are set to 999 5 4 THE RIGHT USE OF THE ATMEMCD SUBROUTINE 5 41 PERTURBED ATMOSPHERE The perturbation consisting to add n times the standard deviation to the mean value type 5 must not be used
24. values as stored in the database On request supplementary variables are computed see output description Also if requested different kind of perturbation can be added to the mean values The available perturbations are small scale perturbations due to the upward propagation of gravity waves for any altitudes no small scale perturbation for pressure large scale perturbations due to the motion of baroclinic weather systems These perturbations are correlated in longitude and altitude perturbation equal to n times the standard deviations for all the variables The two first types of perturbations have a random component The perturbations are described in details in the Detailed Design Document In summary 1 The gravity wave perturbation to a meteorological variable is calculated by considering vertical displacements of the form h z sn 0 where 6 A is a characteristic vertical wavelenght for the gravity wave input of atmemcd Default value 16 km 15 a randomly generated surface angle h is the amplitude of the wave depending of the height z If z is higher than 100 km the amplitude of the wave is taken equal to the amplitude at 100 km The amplitude of the wave is limited to 2 to saturate the amplitude of the perturbation when it becomes statically unstable The perturbation is deduced from the difference between the variable value at the altitude z z and the variable value at t
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