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Readme for TRMM Product 3B42 (V7)

Data Access for
TRMM and Other Satellites Precipitation Product

3B42: http://mirador.gsfc.nasa.gov/cgi-bin/mirador/presentNavigation.pl?tree=project&dataset=3B42:%203-Hour%200.25%20x%200.25%20degree%20merged%20TRMM%20and%20other%20satellite%20estimates&project=TRMM&dataGroup=Gridded&version=007


Contents of TRMM and Other Satellites Precipitation Product 3B42

Summary

The purpose of the 3B42 algorithm is to produce TRMM-adjusted merged-infrared (IR) precipitation and root-mean-square (RMS) precipitation-error estimates. The algorithm consists of two separate steps. The first step uses the TRMM VIRS and TMI orbit data (TRMM products 1B01 and 2A12) and the monthly TMI/TRMM Combined Instrument (TCI) calibration parameters (from TRMM product 3B31) to produce monthly IR calibration parameters. The second step uses these derived monthly IR calibration parameters to adjust the merged-IR precipitation data, which consists of GMS, GOES-E, GOES-W, Meteosat-7, Meteosat-5, and NOAA-12 data. The final gridded, adjusted merged-IR precipitation (mm/hr) and RMS precipitation-error estimates have a daily temporal resolution and a 0.25-degree by 0.25-degree spatial resolution. Spatial coverage extends from 50 degrees south to 50 degrees north latitude.

For more details of the algorithm, go to ftp://meso-a.gsfc.nasa.gov/pub/trmmdocs/3B42_3B43_doc.pdf

Data Flow Description

The data flow of 3B42 and the rest of the products are found in ftp://meso-a.gsfc.nasa.gov/pub/trmmdocs/3B42_3B43_doc.pdf.

Data Set Description

Data Characteristics

TRMM 3B42 Characteristics
Temporal Coverage Start Date: 1998-01-01; Stop Date: -
Geographic Coverage Latitude: 50°S - 50°N; Longitude:180°W - 180°E
Temporal Resolution 3-Hourly
Horizontal Resolution 0.25° x 0.25°; nlat = 400, nlon = 1440
Average File Size Compressed: ~0.71 MB; Original: ~11 MB
File Type HDF

Data Format Structure

Further information on the contents and structure of this product can be found in File Specifications for TRMM Products - Version 7.00

Data Format Structure for 3B42
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
Grid Structure Char Attribute 5,000  - - - - The specification of the grid geometry
precipitation Float SDS nlat*nlon - 0.0 - 100  mm hr-1 TMPA precipitation estimate
relativeError Float SDS nlat*nlon - 0.0 - 200 mm hr-1 TMPA random error estimate
satPrecipitationSource Integer SDS 2 nlat*nlon -     Flag to show source of data at each 0.25 x 0.25 degree box.
HQprecipitation Float SDS 4 nlat*nlon  - 0.0 - 100 mm hr-1 Pre-gauge-adjusted microwave precipitation estimate at each 0.25 x 0.25 degree box.
IRprecipitation Float SDS 4 nlat*nlon  - 0.0 - 100 mm hr-1 Pre-gauge-adjusted infrared precipitation estimate at each 0.25 x 0.25 degree box.
satObservationTime Integer SDS 1 nlat*nlon  - -90 - 90 minute Satellite observation time minus the time of the granule at each 0.25 x 0.25 degree box.
Note: nlat =  400: number of 0.25° latitude grids from 50°S - 50°N;
          nlon = 1440: number of 0.25° longitude grids from 180°W - 180°E;
          Missing data are given the value of -9999.9
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Last updated: Mar 18, 2013 04:39 PM ET