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1. Note 4 22 GHz Brightness Temperature The SSM I sensor is not dual polarized at 22 235 GHz Hence the conversion from antenna temperature to brightness temperature needs to be done differently This problem is discussed on page 13 of the User s Manual SSM I Antenna Temperature Tapes Rev 1 For V7 we use the following Tg22V 1 01911 T 22V 1 93574 for earth incidence angle of 52 7 Tp22V 1 01865 T 22V 2 05980 for earth incidence angle of 53 7 RSS Technical Document 07032014SSMI These two incidence angles bracket the incidence angle variation experienced the SSM Is For incidence angles between 52 7 and 53 7 a linear interpolation is used to find Ts22V Note that the array corresponding to Tg22V is called FCDR_brightness_temperature_22V 4 MISSING Tg VALUES A Tg value of 100 0 indicates no Tx value is available to the User The fill value of 100 0 Tg occurs when the following events occur a If quality flags 1 2 3 and or 4 are equal to 1 then all Tgs in the scan for all channels are set to 100 0 b If either the v pol or h pol calibration problem flag is 1 for a particular frequency then all Tgs in the scan for that frequency both v pol and h pol are set to 100 0 c If the Earth viewing count is out of bounds or if the recovered Earth viewing count is not an integer then the Tg just for that observation is set to 100 0 Depending on your reading software capabilities you may or may not need to che2. respectively The following types of anomalies will trigger this flag a Cold calibration counts and or hot calibration counts that are out of bounds b Automatic gain control setting that is currently changing Flag 12 Removal of moon contamination in the cold mirror was not possible for the lower frequency channels 19 37 GHz Flag 13 Removal of moon contamination in the cold mirror was not possible for the 85 GHz channels Flag 14 Not used Note 2 Sun Glint The sun glint angle is defined as the angle between two vectors a and b Vector a is the vector going from the SSM I footprint to the SSM I antenna Vector b is the vector pointing in the direction of sunlight reflected off the Earth surface at the location of the SSM I footprint assuming that the earth surface is a specular reflector Low sun glitter angles mean that reflected sunlight is being received by the SSM I Note 3 Land and Sea Ice Percentage land contamination is defined as the percentage of the power received by the SSM I 19 GHz antenna pattern that comes from land The ice flag is based on a monthly climatology A value of ice_flag_res 0 means that we have never seen sea ice at that location and month since the first SSM I was launched in 1987 Hence it is extremely unlikely that the footprint will contain ice The one exception to this is icebergs which may pass through grid cells located off the East Coast of Argentina yielding an ice_flag 0 during passage
3. 350 0 Float n a FCDR_brightness_temperature_19H footprint_number_lores scan_number lores 19 35GHz H pol Ts kelvin 100 0 50 0 to 350 0 Float n a FCDR_brightness_temperature_22V footprint_number_lores scan_number_lores 22 235GHz V pol Ts Note 4 kelvin 100 0 50 0 to 350 0 Float n a FCDR_brightness_temperature_37V footprint_number_lores scan_number_lores 37 0GHz V pol Ts kelvin 100 0 50 0 to 350 0 Float n a FCDR_brightness_temperature_37H footprint_number_lores scan_number_lores 37 0GHz H pol Ts kelvin 100 0 50 0 to 350 0 Float n a Geodetic latitude for hi res degrees Latitude_hires footprint_number_hires scan_number_hires channels North 30000 90 0 to 90 0 Integer2 0 01 Longitude_hires footprint_number_hires scan_number_hires eet longitude for hi res cg 30000 180 to 180 Integer2 0 01 Geodetic latitude for lo res degrees Latitude_lores footprint_number_lores scan_number_lores channels North 30000 90 0 to 90 0 Integer2 0 01 x Geodetic longitude for lo res degrees p Longitude_lores footprint_number_lores scan_number_lores channels East 30000 180 to 180 Integer2 0 01 RSS Technical Document 07032014SSMI Note 1 Quality Control Flags The iqual_flag for the lo res and hi res channels indicates the quality of the scan If all the flag values are not zero then there is a problem with the scan We advise Users to look at the individual flags to decide if the scan should be used for their purposes In general if the
4. FCDR_V07RO00_F _Dyyyymmdd_Sittt_Etttt_R nc where is the SSM I satellite number i e 08 10 11 13 14 and 15 yyyy is the long year mm is month dd is day of month tttt is hour and minute of UTC day 24 hour clock start time and end time HHH is the orbit number i e 00001 to 99999 also referred to as the granule number By definition an SSM I orbit begins near the South Pole at the point where the z component i e north south of the spacecraft velocity vector changes from a negative value to a positive value For previous users of this data set be sure to note that this is a different convention than that used in any earlier versions of RSS brightness temperature data files This change in convention brings uniformity to SSM I SSMIS WindSat and AMSRP E data from RSS Each orbital file contains additional scans at the beginning and end of each orbit For example the file for orbit 10000 contains scans starting with orbit position 9999 95 and ending with orbit position 10001 05 The data at the end of orbit file 10000 are then given again in orbit file 10001 This 5 overlap of the orbit files facilitates user requirements that involve scan averaging In order to reduce the downlink telemetry data rate the SSM I only takes measurements for the 3 lower frequencies 19 22 and 37 GHz every other scan The 85 GHz measurements are taken every scan Likewise the lower frequency measurements are only taken at every other alon
5. RSS Technical Document 07032014SSMI RSS SSM I Version 7 Brightness Temperature Data Set netCDF File Format Specification Version 7 Release 0 July 3 2014 1 INTRODUCTION This document describes the Version 7 V7 SSM I Brightness Temperature Tg Dataset produced by Remote Sensing Systems RSS in netCDF version 4 0 format for the NOAA CDR program This document provides further details of the metadata listed in the netCDF files Users are advised to refer to the references below for greater detail and historical SSM I information The V7 Tg dataset incorporates improved geolocation calibration and quality control procedures in a consistent manner for the entire 28 year SSM I dataset In addition the six SSM Is F08 F10 F11 F13 F14 and F15 have been carefully inter calibrated among themselves and with WindSat AMSR E and the F17 SSMIS This allows investigators to confidently use these SSM I products for detailed interannual and decadal trend studies Users should read the V7 SSM I Calibration Report for detailed description of the improvements in geolocation and calibration of the SSM I instruments The netCDF files are generated from the V7 binary brightness temperature files using an IDL program Any known problems with this or earlier versions of the data set are listed in Section 9 below 2 FILE NAME STRUCTURE and FORMAT The SSM I brightness temperature data are stored in orbital files The file names have the form RSS_SSMI_
6. above 2 The scan_time_lores variable has the wrong dimension It should be the number of scans for the low resolution channels 1800 but instead was accidentally dimensioned with the number of scans for the high resolution channels 3600 The first 1800 values contain the valid scan times for the variable the remaining 1800 values remain as the default __fillvalue 1 0E30 The table above lists the correct dimension that scan_time_lores should be 1800
7. ck if Tp 100 0 and exclude these missing values 5 QUALITY FLAG VALUES AND SUGGESTED FILTERING For a given observation cell look at the Tg values required for your particular application If any of these Tg values is 100 0 skip the cell Also if your application requires the low frequency channels 19 37 GHz and quality flag 12 is 1 skip the cell Likewise if your application requires the high frequency channels 85 GHz and quality flag 13 is 1 skip the cell 6 DATA USE CITATION Please acknowledge use of these data in your publications Development of this type of data set has taken many years and much effort on the part of the scientists involved These scientists rely on the fair use and proper acknowledgment of the CDR to sustain their professional reputations and careers Please use the suggested Acknowledgement Request The SSM I CDR used in this study was acquired from NOAA s National Climatic Data Center http www ncdc noaa gov This CDR was originally developed by Frank Wentz and colleagues for the NOAA CDR Program Citation Request Hilburn K A and F J Wentz 2008 Intercalibrated Passive Microwave Rain Products from the Unified Microwave Ocean Retrieval Algorithm UMORA Journal of Applied Meteorology and Climatology 47 778 794 NOAA s CDR Program and or its official distribution partners provide sustained open access to released CDR packages and related information To ensure use of official products and acc
8. e Data Record FCDR intercalibrated and homogenized brightness temperature polar orbiting product with quality flags starting from July 1987 keywords EARTH SCIENCE gt SPECTRAL ENGINEERING gt MICROWAVE gt BRIGHTNESS TEMPERATURE keywords_vocabulary NASA Global Change Master Directory GCMD Earth Science Keywords Version 6 0 platform DMSP 5D 2 F13 gt Defense Meteorological Satellite Program F13 sensor SSM I gt Special Sensor Microwave Imager cdm_data_type Swath cdr_program CICS NC supported Climate Data Record Program for satellites FY 2011 cdr_variable fcdr_brightness_temperature_19V fcdr_brightness_temperature_19H fcdr_brightness_temperature_22V fcdr_brightness_temperature_37V fcedr_brightness_temperature_37H fcdr_brightness_temperature_85V fcedr_brightness_temperature_85H source F13 142247 dat date_created 201207111T0536282 creator_name Carl Mears creator_url http www remss com creator_email mears remss com institution Remote Sensing Systems processing_level NOAA Level 2 references doi 10 1175 2007JAMC1635 1 doi 10 1126 science 1140746 SSM I Users Interpretation Guide UG32268 900 Rev C 29 Nov 2000 history 1 2011 09 30 Carl Mears Remote Sensing Systems created initial netCDF file converted from the original RSS data format geospatial_lat_min 87 729996f float geospatial_lat_max 87 52
9. ess to the latest codes data sets and usage information e g known issues users agree to not redistribute the CDR in whole or in part to others 7 REFERENCES Users should read this document in conjunction with the earlier versions of RSS SSM I Users Manuals which give more details on the SSM I data history including gt SSMI Version 7 Calibration Report January 10 2012 gt Users Manual SSM I Antenna Temperature Tapes Rev 2 December 1993 gt Users Manual SSM I Antenna Temperature Tapes Rev 1 December 1991 These and other documents are available from Remote Sensing Systems This document you are reading is primarily intended to describe the format of the RSS V7 netCDF files available from NOAA FCDR program RSS Technical Document 07032014SSMI 8 netCDF GLOBAL FILE ATTRIBUTES Below is an example of global file attributes for one netCDF file global attributes Conventions CF 1 5 Metadata_Conventions CF 1 5 Unidata Dataset Discovery v1 0 NOAA CDR v1 0 GDS v2 0 standard_name_vocabulary CF Standard Name Table v16 11 October 2010 id RSS_SSMIFCDR_V07R00_F13 D20030601 S0849 E1041 _R42247 nc naming_authority gov noaa ncdc metadata_link gov noaa ncdc C00810 title RSS Version 7 SSM I FCDR product_version vO07r00 date_issued 2011 09 30 summary Remote Sensing Systems RSS Version 7 Special Sensor Microwave Imager SSM l Fundamental Climat
10. f float geospatial_lon_min 180 0f float geospatial_lon_max 179 98999f float geospatial_lat_units degrees_north geospatial_lon_units degrees_east spatial_resolution 19 V H GHz 45km X 70km 22 V GHz 40km X 60km 37 V H GHz 30km X 38km 85 V H GHz 14km X 16km time_coverage_start 2003 06 01 08 49 082 time_coverage_end 2003 06 01 10 41 132 time_coverage_duration PT6724S license No restrictions on access or use contributor_name Frank Wentz Carl Mears contributor_role Principal investigator and originator of input source or antenna temperature data Processor and author of entire driver routine write_ssmi_tbs_netcdf pro which converts RSS native brightness temperature format to netCDF 4 CoordSysBuilder ucar nc2 dataset conv CF1Convention 6 RSS Technical Document 07032014SSMI 9 Known Problems Errata in RSS SSM I V7 netCDF Data Set The RSS SSM I V7 netCDF data set files are produced using an IDL program to translate the RSS binary format L1B brightness temperature data files available from RSS Identified problems are listed below for each data set version Version 7 Release 0 1 The land_percentage_hires and land_percentage_lores variables each have a valid range of 0 to 100 but the valid range listed in the netCDF file states 0 to 250 The actual range 0 to 100 as opposed to the file metadata 0 to 250 is listed in the table
11. footprint degrees 30000 180 to 180 Integer2 0 01 clockwise from North Sun_glitter_angle_hires footprint_number_hires scan_number_hires Paes ao degrees 30000 0 to 180 Integer2 0 01 Land_percentage_hires footprint_number_hires scan_number_hires Rs E a 255 0 to 100 Integer2 0 4 Observation sea ice flag O no ice Ice_flag_hires footprint number_hires scan_number_hires Note 3 n a 255 ice possible Integer2 n a FCDR_brightness_temperature_85V footprint_number_hires scan_number_hires 85 5 GHz V pol Ts kelvin 100 0 50 to 350 Float n a FCDR_brightness_temperature_85H footprint_number_hires scan_number_hires 85 5 GHz H pol Ts kelvin 100 0 50 to 350 Float n a Earth_incidence_angle_lores footprint_number_lores scan_number_lores ep eae Mes degrees 30000 50 0 to 58 0 Integer2 0 002 Observation earth azimuth Earth_azimuth_angle_lores footprint_number_lores scan_number_lores angle for lo res footprint degrees 30000 180 to 180 Integer2 0 01 clockwise from North Sun_glitter_angle_lores footprint_number_lores scan_number_lores SCL se eEERNGn 2y degrees 30000 0 to 180 Integer2 0 01 Land_percentage_lores footprint_number_lores scan_number_lores Sarin POA 255 0 to 100 Integer2 0 4 Observation sea ice flag O no ice Ice_flag_lores footprint ynumber_lores scan_number_lores Note 3 n a 255 1 ice possible Integer2 n a FCDR_brightness_temperature_19V footprint_number_lores scan_number_lores 19 35GHz V pol Ts kelvin 100 0 50 0 to
12. g scan position The 85 GHz measurements are taken at all scan positions For example an orbital file typically has about 3546 scans and the total number of observations taken during the Earth viewing portion of the scan is 128 Thus the arrays of 85 GHz observations are 128 by 3546 However the arrays for the lower frequency observations are 64 by 1773 We refer to the 85 GHz grid as hi res and the lower frequency grid as lo res The maximum number of scans in an orbital file is about 3546 To be safe we allow for a maximum value of 3600 The vectors and arrays in the data file are a fixed dimensional size with 3600 being the scan dimension of the high resolution data and 1800 being the scan dimension of the low resolution data RSS Technical Document 07032014SSMI 3 SUMMARY OF DATA FIELDS Each netCDF SSM I brightness temperature file contains the following scalars vectors and arrays Dimension definitions scan_number_hires 3600 scan_number_lores 1800 footprint_number_hires 128 footprint_number_lores 64 fourteen_flags 14 Scalar Variables Name Long Name Description Units _Fill Value Valid Range Type iorbit integer orbit number n a 0 1 to 100000 Integer2 Vector Variables Dimension is max number of scans for that resolution Name Description Units _ Fill Value Valid Range Type Scale when scaled Factor Scan start time UTC for high resolution scans second
13. s since 2000 scan_time_hires scan_number_hires in a referenced or elapsed time format 01 01 00 00 00 1 0E30 1 0E9 to 1 0E9 Double n a Scan start time UTC for low resolution scans seconds since 2000 scan_time_lores scan_number_lores in a referenced or elapsed time format 01 01 00 00 00 1 0E30 1 0E9 to 1 0E9 Double n a orbit_position scan_number_hires Orbit number with position in orbit as fraction n a 0 0 1 0 to 100000 0 Double n a eg 9999 95 i Spacecraft nadir geodetic latitude at 2 sc_lat scan_number_hires time scan_time degrees North 500 0 90 0 to 90 0 Float n a sc_lon scan_number_hires ee E geodetic east longitudeat degrees East 500 0 0 0 to 360 0 Float n a sc_alt scan_number_hires Spacecraft 1 nadir altitude at time scan_time meters 500 0 400000 0 to 1200000 0 Float n a RSS Technical Document 07032014SSMI Array Variables ae _Fill Valid Range Scale Name Description Units Value when scaled Type Factor iqual_flag_hires scan_number_hires fourteen_flags E aa erties y n a 0 Oor1 Byte n a iqual_flag_lores scan_number_lores fourteen_flags fies eres cle fi n a 0 Oor1 Byte n a Earth_incidence_angle_hires footprint_number_hires scan_number_hires senate eh toads degrees 30000 50 to 58 Integer2 0 002 Observation earth azimuth Earth_azimuth_angle_hires footprint_number_hires scan_number_hires angle for hi res
14. sum of the iqual_flags is not zero then the scan should be skipped However there are situations where too much data may be discarded For example for the F08 SSM I the 85 GHz channels for the most part are erroneous and flags 9 10 and 12 will usually be equal to 1 For this case if the User does not need the 85 GHz observations then a sum of flags check would remove data that could be used Ignoring flags 9 10 and 12 would be acceptable The flags have the following meanings Flag 1 Scan is missing no data Missing scans that occur in the middle of an orbit are included in the orbital file as zero filled spacers However missing scans that occur at the beginning or end of the orbit are not included The appropriate scan_time is set to 1 e30 the fill value Flag 2 Scan occurs during a period of erroneous data This problem only occurs for the early SSM I data F08 F10 F11 and F13 before 1999 See the SSM I T User s Manual Revision 2 December 1993 for more information Flag 3 Scan is affected by calibration errors due to NRL scan averaging This problem only occurs for the early SSM I data between October 9 1990 and August 29 1992 See the SSM I Ta User s Manual Revision 2 December 1993 for more information Flag 4 Thermistor readings for the scan are out of bounds Flags 5 11 These flags indicate a problem with the calibration data for the scan These 7 flags refer to channels 19V 19H 22V 37V 37H 85V and 85H
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