
 Info
TRMM Product Level 2B Combined (PR, TMI) Rainfall Profile
Data Access for 2B31:
http://mirador.gsfc.nasa.gov/cgibin/mirador/presentNavigation.pl?tree=project&project=TRMM&dataGroup=Orbital&dataset=2B31%20(Version%20007):%20Combined%20Rainfall%20Profile%20(PR,%20TMI)&version=007 Contents: 2B31, "TRMM Combined", derives vertical hydrometeor proles using data from PR radar and TMI. It also computes the correlationcorrected massweighted mean drop diameter and its standard deviation, and latent heating. The following sections describe the structure and contents of the format. PR Level 1A ==> 1B11 TMI Calibrated Brightness Temperature and 1C21 PR Reflectivities 1C21 ==> 2B31 Combined (PR, TMI) Rainfall Profile The data flow of all products are shown in Satellite Algorithm Flow Diagram. Data Characteristics TRMM 2B31 Data Characteristics   Preboost (before 20010807)  Postboost (after 20010 824)  Temporal Coverage  Start Date: 19971208 Stop Date: 20010807  Start Date: 20010824 Stop Date:   Geographic Coverage  Latitude: 38°S  38°N Longitude:180°W  180°E  Latitude: 38°S  38°N Longitude:180°W  180°E  Temporal Resolution  About 91.5 minutes per orbit About 16 orbits per day More information about revisit frequency  About 92.5 minutes per orbit About 16 orbits per day More information about revisit frequency  Horizontal Resolution  4.3 km  5.0 km  Scan Characteristics  Swath Width: 215 km Rays/Scan: nray = 49 Scans/Second (SS): 1/0.6 Seconds/Orbit (SO): 5490 Average Scans/Orbit: nscan = SS*SO = 9150  Swath Width: 247 km Rays/Scan: nray = 49 Scans/Second (SS): 1/0.6 Seconds/Orbit (SO): 5550 Average Scans/Orbit: nscan = SS*SO = 9250  Average File Size  Compressed: ~11 MB  Compressed: ~11 MB  File Type  HDF  HDF  Data Format Structure Further information on the contents and structure of the 2B31 product can be found in: File Specifications for TRMM Products  Version 7.00 Data Format Structure for 2B31, Combined (PR, TMI) Rainfall Profile  Name  Type  Record Size (byte)  Dim Size/ # of Records  Scaled by  Range  Unit  Description  ECS Core Metadata  Char Attribute  10,000          ECS Core Metadata.  PS Metadata  Char Attribute  10,000          Product Specific Metadata.  Swath Structure  Char Attribute  5,000          Specification of the swath geometry.  Scan Time  Vdata Table  8  nscan        Time associated with the scan, expressed as 8byte float UTC second of the day.  Latitude  Float SDS  4  nray*nscan      degree  Geolocation is the earth location of the center of the IFOV at the altitude of the earth ellipsoid.  Longitude  Float SDS  4  nray*nscan      degree  Geolocation is the earth location of the center of the IFOV at the altitude of the earth ellipsoid.  Scan Status  Vdata Table  15  nscan        Status of each scan.  Navigation  Vdata Table  88  nscan        Spacecraft geocentric information.  Dhat  Integer SDS  2  nray*nscan  100  0.7 ~ 1.8  mm^{*}  Correlationcorrected massweighted mean drop diameter. ( more )  SigmaDhat  Integer SDS  2  nray*nscan  100  0.00 ~ 2.00  mm^{*}  RMS uncertainty in DHat. The accuracy is 0.01 "normalized" mm.  graupel  Integer SDS  2  Nradarrange x nray x nscan  1000  0 ~ 10  g/m^{3}  graupel is defined as frozen hydrometeors with a density of 600 Kg=m3. "graupel" thus is mostly bigger, denser frozen hydrometeors, and would represent aggregates, graupel, and hail.  snow  Integer SDS  2  Nradarrange x nray x nscan  1000  0 ~ 10  g/m^{3}  snow is dened as frozen hydrometeors with a density of 100 Kg=m3. "snow" thus is mostly smaller, uer frozen hydrometeors.  prSurf  Float SDS  4  nray x nscan    0 ~ 500  mm/hr  The surface precipitation rate (liquid plus solid). The accuracy is 0.1 mm/hr.  Rhat  Integer SDS  2  Nradarrange*nray*nscan  10  0.0 ~ 500.0  mm/hr  Instantaneous rain rate at the radar range gates. The accuracy is 0.1 mm/hr.  SigmaRhat  Integer SDS  2  Nradarrange*nray*nscan  10  125 ~ 125  mm/hr  RMS uncertainty in the Rhat estimated at the radar range gates. (The negative sign indicating estimates based on a "rainpossible" detection by the radar rather than the "raincertain" associated with positive values). The values 125 and 125 are reserved for cases where the RMS uncertainty could not be accurately estimated. The accuracy is 0.5 mm/hr.  RRSurf  Float SDS  4  nray*nscan    0.0 ~ 500.0  mm/hr  Surface rain rate.  SigmaRRSurf  Integer SDS  2  nray*nscan  100  125 ~ 125  mm/hr  RMS uncertainty in RRSurf. (The negative sign indicating estimates based on a "rainpossible" detection by the radar rather than the "raincertain" associated with positive values). The values 125 and 125 are reserved for cases where the RMS uncertainty could not be accurately estimated. The accuracy is 0.5 mm/hr.  latentHeadHH  Float SDS  4  nlayer*nray*nscan      °K/hr  The "hydrometeor heating" calculated from the vertical fluxes of the different hydrometeor species and using average archival temperature/ pressure/humidity soundings which depend on longitude and latitude only. In V7 all the precipitation is assumed to be liquid. Heating is listed for 13 layers.  spare  Float SDS  4  4*nray*nscan        Contents and ranges are not public.  * "normalized units" are defined as follows: If a variable X, expressed in grams, is correlated with the rain rate R and a variable Y is defined where Y = X * R^{0.37} R, then the unit of Y is called "normalized grams". Nradarrange: The number of radar range gates, up to about 20 km from the earth ellipsoid (80). The gates range from gate 0 to gate 79. Each gate is 250 m apart, with gate 79 at the earth ellipsoid.  TRMM 2B31 can be accessed and ordered using the Goddard DAAC's TRMM Data Search and Order System at http://mirador.gsfc.nasa.gov/cgibin/mirador/presentNavigation.pl?tree=project&project=TRMM&dataGroup=Orbital&dataset=2B31%20(Version%20007):%20Combined%20Rainfall%20Profile%20(PR,%20TMI)&version=007 . Appendix TRMM 2B31 Geolocation  Geolocation is the earth location of the center of the IFOV at the altitude of the earth ellipsoid. The first dimension is latitude and longitude, in that order. The next dimensions are numbers of pixels and scans. Values are represented as floating point decimal degrees. Offearth is represented as 9999.9. Latitude is positive north, negative south. Longitude is positive east, negative west. A point on the 180° meridian is assigned to the western hemisphere.  TRMM 2B31 Dhat Description  Dhat is the correlationcorrected massweighted mean drop diameter. The accuracy is 0.01 "normalized" mm (the value 0 indicates no rain or bad data). The average value of dHat is around 1.1 "normalized" mm, a unit which comes from the fact that dHat is related to the true massweighted mean drop diameter D* mm by the formula dHat = D*rHat0.155 (with rHat in mm/hr).  

