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TRMM Product Level 2B Combined (PR, TMI) Rainfall Profile

Data Access for

2B31:

http://mirador.gsfc.nasa.gov/cgi-bin/mirador/presentNavigation.pl?tree=project&project=TRMM&dataGroup=Orbital&dataset=2B31%20(Version%20007):%20Combined%20Rainfall%20Profile%20(PR,%20TMI)&version=007


Contents:

Summary

2B31, "TRMM Combined", derives vertical hydrometeor pro les using data from PR radar and TMI. It also computes the correlation-corrected mass-weighted mean drop diameter and its standard deviation, and latent heating. The following sections describe the structure and contents of the format.

Data Flow Description

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 Set Description

Data Characteristics

TRMM 2B31 Data Characteristics
  Pre-boost (before 2001-08-07) Post-boost (after 2001-0 8-24)
Temporal Coverage Start Date: 1997-12-08
Stop Date: 2001-08-07
Start Date: 2001-08-24
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 nscan - - - Time associated with the scan, expressed as 8-byte 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.
D-hat Integer SDS nray*nscan 100 0.7 ~ 1.8 mm* Correlation-corrected mass-weighted mean drop diameter. ( more )
Sigma-D-hat Integer SDS nray*nscan 100 0.00 ~ 2.00 mm* RMS uncertainty in D-Hat. The accuracy is 0.01 "normalized" mm.
graupel Integer SDS 2 Nradarrange x nray x nscan 1000 0 ~ 10 g/m-3 graupel is de fined 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 de ned 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.
R-hat Integer SDS 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.
Sigma-R-hat Integer SDS Nradarrange*nray*nscan 10 -125 ~ 125 mm/hr RMS uncertainty in the R-hat estimated at the radar range gates. (The negative sign indicating estimates based on a "rain-possible" detection by the radar rather than the "rain-certain" 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.
RR-Surf Float SDS nray*nscan - 0.0 ~ 500.0 mm/hr Surface rain rate.
Sigma-RR-Surf Integer SDS nray*nscan 100 -125 ~ 125 mm/hr RMS uncertainty in RR-Surf. (The negative sign indicating estimates based on a "rain-possible" detection by the radar rather than the "rain-certain" 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 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*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 * R0.37 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/cgi-bin/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. Off-earth 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 D-hat Description
D-hat is the correlation-corrected mass-weighted 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 mass-weighted mean drop diameter D* mm by the formula dHat = D*rHat-0.155 (with rHat in mm/hr).
Layers and upper and lower boundaries
in km above the earth ellipsoid
used in calculating Latent Heat
Layers Upper Boundary Lower Boundary
  1 18 16
  2 16 14
  3 14 12
  4 12 10
  5 10   8
  6   8   7
  7   7   6
  8   6   5
  9   5   4
10   4   3
11   3   2
12   2   1
13   1   0
     
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Last updated: Aug 28, 2014 11:11 AM ET
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