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TRMM Monthly 5 x 5 Degree Combined Rainfall Data 3B31

Data Access for

3B31: TRMM Monthly Combined Rainfall

Contents:

Summary

This document provides basic information on 3B31, TRMM Monthly 5 x 5 Degree Combined Rainfall Data. The purpose of 3B31 is to compare and accumulate the instantaneous rainfall products from the TMI (2A12) and Combined (2B31) algorithms. This is done because the combined algorithm should, in principle, produce better rainfall estimates than would the TMI alone. Its swath, however, is only 220 km compared to the 760 km swath of the TMI. Thus, for monthly accumulations, the best possible solution was thought to be the use of the TMI product (for sampling), but normalized by its ratio to 2B31. 3B31 contains these accumulations and ratio. The algorithm also provides the ratio rain water contents for 14 vertical layers as well.

Output data of 2A12 and 2B31 are input to the 3B31 and then accumulated for each month at 0.5 grid elements. Monthly surface rainfall totals are derived by multiplying the mean rainfall rate by the total number of hours in each month. Because the rain water content profile of 2A12 and rain rate profile of 2B31 are output at different vertical resolutions, averaging the outputs of 2B-31 over several radar range gates to match the 14 layers of 2A12 is necessary. Also, the rain rate (mm/hr) at each radar gate in 2B-31 is converted into rain water content (g/m3) to match that in 2A-12. The relationship between rain rate and rain water content can be found in Haddad et al., (1996).

Data Flow Description

The data flow of all products are shown in Satellite Algorithm Flow Diagram.

Data Set Description

Data Characteristics

Temporal Coverage Start Date: 1997-12-08; Stop Date: -
Geographic Coverage Latitude: 40°S - 40°N;Longitude:180°W - 180°E
Temporal Resolution Monthly
Horizontal Resolution 5° x 5°; nlat = 16, nlon = 72
Average File Size Compressed: ~380 KB; Original: ~440 KB
File Type HDF


Data Format Structure

The following table summarizes the contents and structure of the TRMM Monthly 5 x 5 Degree Combined Rainfall Data (3B31) product. Further information can be found in Volume 4 of the "File Specifications for TSDIS Products - Level 2 and Level 3" .

Data Format Structure for 3B31, TRMM Monthly 5 x 5 Degree Combined Rainfall Data
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
GridStructure Char Attribute 5,000  - - - - GridStructure gives the specification of the geometry of the grids.
sfcrainTMI Float SDS 4  nlat*nlon - 0.0 ~ 3000.0 mm Surface rain from 2A12 accumulated in each 5° x 5° box
convect Rain Float SDS 4  nlat*nlon - 0.0 ~ 3000.0 mm Convective surface rain from 2A12 accumulated in each 5° x 5° box
cloudWater Float SDS 4  nlat*nlon*nlayer - 0.0 ~ 10.0 g m-3 Monthly mean cloud water from 2A12 at each vertical layer in each 5° x 5° box
rainWaterTMI Float SDS 4  nlat*nlon*nlayer - 0.0 ~ 10.0 g m-3 Monthly mean rain water from 2A12 at each vertical layer in each 5° x 5° box
cloudIce Float SDS 4  nlat*nlon*nlayer - 0.0 ~ 10.0 g m-3 Monthly mean cloud ice from 2A12 at each vertical layer in each 5° x 5° box
graupel Float SDS 4  nlat*nlon*nlayer - 0.0 ~ 10.0 g m-3 Monthly mean graupel from 2A12 at each vertical layer in each 5° x 5° box
latentHeat Float SDS 4  nlat*nlon*nlayer - -256.0 ~ 256.0 deg hr-1 Monthly mean latent heating from 2A12 at each vertical layer in each 5° x 5° box
sfcrainCOMB Float SDS 4  nlat*nlon - 0.0 ~ 3000.0 mm Surface rain from 2B31 accumulated in each 5° x 5° box
rainWaterCOMB Float SDS 4  nlat*nlon*nlayer - 0.0 ~ 10.0 g m-3 Rain water at each vertical layer from 2B31 accumulated in each 5° x 5° box
sfcrainTMIoverlap Float SDS 4  nlat*nlon - 0.0 ~ 3000.0 mm Surface rain from 2A12 where 2A12 and 2B31 overlap accumulated in each 5° x 5° box
convectRainoverlap Float SDS 4  nlat*nlon - 0.0 ~ 3000.0 mm Convective surface rain from 2A12 where 2A12 and 2B31 overlap accumulated in each 5° x 5° box
sfcrainCOMBoverlap Float SDS 4  nlat*nlon - 0.0 ~ 3000.0 mm Surface rain from 2B31 where 2A12 and 2B31 overlap accumulated in each 5° x 5° box
surfAdjRatio Float SDS 4  nlat*nlon - - - The ratio of 2B31 to 2A12 surface rainfall, calculated from the swath overlap region for each 5° x 5° box
surfAdjRatiooverlap Float SDS 4  nlat*nlon - - - The ratio of 2B31 to 2A12 surface rainfall, calculated from the swath overlap region for each 5° x 5° box

Parameters used in above table:
Name Value Definition
nlat 16  the number of 5° grid intervals of latitude from 40° N to 40° S
nlon 72  the number of 5° grid intervals of longitude from 180° W to 180° E
nlayer 14  the number of profiling layers


14 Vertical Layers
Layer Index Layer Height
1 surface - 0.5 km
2 0.5 - 1.0 km
3 1.0 - 1.5 km
4 1.5 - 2.0 km
5 2.0 - 2.5 km
6 2.5 - 3.0 km
7 3.0 - 3.5 km
8 3.5 - 4.0 km
9 4.0 - 5.0 km
10 5.0 - 6.0 km
11 6.0 - 8.0 km
12 8.0 -10.0 km
13 10.0 -14.0 km
14 14.0 - 18.0 km
TRMM 3B31 can be accessed and ordered from the Goddard DAAC's TRMM Data Search and Order System at http://disc.sci.gsfc.nasa.gov/data/datapool/TRMM_DP/01_Data_Products/02_Gridded/04_Monthly_Combined_Rain_3B_31/ .

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  • Last updated: Sep 18, 2009 10:32 AM ET