TRMM Precipitation Radar (PR) Gridded Rainfall Product (TRMM Product 3A25)
Entry ID:
GES_DISC_TRMM_3A25_V7
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Summary
Abstract:
The primary objective of algorithm 3A25 is to compute various rainfall statistics over a month from the level 2 PR products. The statistics are derived at two spatial resolutions: (1) a standard space scale of 5 degrees by 5 degrees (latitude x longitude) cells and (2) a high resolution subset of 0.5 degree x 0.5 degree cells. The output variables include rainfall rate (mm/hour) profile at 2, 4, ... 6, 10, and 15 km, fractional rain, snow ice layer, and surface rain rate (mm/hour). The output statistics include probabilities of occurrence, means and standard deviations, histograms, and correlation coefficients.
All statistics in 3A-25, except near-surface rain rate, are computed only when rain is judged in 1C-21 to be "certain." When rain is judged in 1C-21 to be "possible," the observation is treated as a "no-rain" observation. For the near-surface rain rate, the statistics (mean, standard deviation, and histogram) are computed for "rain-possible" as for the usual "rain-certain." Because the "rain-possible" cases are dominated by noise so that the probability of false-alarm is high, the "rain-certain" statistics should be considered as more representative of the TRMM radar data.
Three types of rain rates are defined in 3A-25: (1) a "near-surface" rain rate that is obtained from the range bin closest to the surface which is not corrupted by the surface clutter, (2) a path-averaged rain rate calculated by summing the values from the storm top (first gate where rain is detected) to the last gate (gate nearest to the surface uncontaminated by surface clutter) and dividing by the number of gates in the interval, and (3) those at fixed heights above the ellipsoid (2, 4, 6, 10, and 15 km).
Spatial coverage is between 40 degrees North and 40 degrees South, owing to the 35 degree inclination of the TRMM satellite.
The data are stored in the Hierarchical Data Format (HDF). The low resolution grids are in the Planetary Grid 1 structure, and the high resolution grids are in the Planetary Grid 2 structure. The file size (one file per month) is about 16 MB (uncompressed). The description of file component objects can be obtained from Volume 4 - Levels 2 and 3 File Specifications provided by the TRMM Science Data and Information System (TSDIS): http://pps.gsfc.nasa.gov/.
The Tropical Rainfall Measuring Mission (TRMM) is a joint U.S.-Japan satellite mission to monitor tropical and subtropical precipitation and to estimate its associated latent heating. TRMM was successfully launched on November 27, at 4:27 PM (EST) from the Tanegashima Space Center in Japan.
The TRMM Precipitation Radar (PR), the first of its kind in space, is an electronically scanning radar, operating at 13.8 GHz that measures the 3-D rainfall distribution over both land and ocean, and defines the layer depth of the precipitation. 
Related URL
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Description:
OPeNDAP Earth Science Data TRMM 3A25.
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Multimedia Sample
View full image
Caption:
3A25 monthly accumulated 2 KM rainfall
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Geographic Coverage
(Click for Interactive Map)
Spatial coordinates
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N: 40.0
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S: -40.0
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E: 180.0
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W: -180.0
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Data Resolution
Latitude Resolution:
0.5 degree
Longitude Resolution:
0.5 degree
Horizontal Resolution Range:
500 km - < 1000 km or approximately 5 degrees - < 10 degrees
Temporal Resolution:
Monthly
Temporal Resolution Range:
Monthly - < Annual
Quality
Missing data scans are checked by monitoring the Scan Status contained in the TRMM 1C-21 product. Scan Status is a Table structure containing entries on a scan-by-scan basis. These entries include a geolocation flag and a data quality flag, indicating the percentage of pixels along each scan with values within a pre-defined range. If Scan Status indicates a missing scan, then no processing is done for that scan for the 3A25 product. However, checks for individual missing variables are not done explicitly.
Access Constraints
None
Data Set Progress
IN WORK
Distribution
Distribution Media:
FTP
Distribution Size:
Average file size: 37874 kb
Distribution Format:
HDF
Fees:
None
Personnel
Role:
TECHNICAL CONTACT
Phone:
(301) 614-5165
Fax:
(301) 614-5268
Email:
gsfc-help-disc at lists.nasa.gov
Contact Address:
Hydrology Data Support Team, Code 610.2
Goddard Space Flight Center
City:
Greenbelt
Province or State:
MD
Postal Code:
20771
Country:
USA
Role:
INVESTIGATOR
Phone:
(301) 614-5652
Fax:
(301) 614-5558
Email:
robert.meneghini-1 at nasa.gov
Contact Address:
Mailstop 614.6
Goddard Space Flight Center
City:
Greenbelt
Province or State:
MD
Postal Code:
20771
Country:
USA
Role:
DIF AUTHOR
Phone:
(301) 614-5165
Fax:
(301) 614-5268
Email:
gsfc-help-disc at lists.nasa.gov
Contact Address:
Hydrology Data Support Team, Code 610.2
Goddard Space Flight Center
City:
Greenbelt
Province or State:
MD
Postal Code:
20771
Country:
USA
Publications/References
TRMM V7 Precipitation Radar Algorithm Instruction Manual (Provided by JAXA): http://www.eorc.jaxa.jp/TRMM/documents/PR_algorithm_product_informa... File Specifications for TRMM Products: ftp://pps.gsfc.nasa.gov/pub/v7filespec/filespec.TRMM.V7.pdf Metadata for TRMM Products: ftp://pps.gsfc.nasa.gov/pub/v7filespec/filespecMeta.TRMM.V7.pdf TRMM V6 vs. V7 Major Data Format Changes: http://pps.gsfc.nasa.gov/Documents/formatChangesV7.pdf Meneghini, R., 1998, J. Appl. Meteor., 37, 924-938. Meneghini, R., and J. Jones, 1993, J. Appl. Meteor., 32, 386-398.
Creation and Review Dates
DIF Creation Date:
2011-07-19
Last DIF Revision Date:
2013-03-22
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