TRMM 3-Hourly 0.25 deg. TRMM and Other-GPI Calibration Rainfall Data
Entry ID:
GES_DISC_TRMM_3B42_V7
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Summary
Abstract:
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 rainfall measuring instruments on the TRMM satellite include the Precipitation Radar (PR), an ... electronically scanning radar operating at 13.8 GHz; TRMM Microwave Image (TMI), a nine-channel passive microwave radiometer; and Visible and Infrared Scanner (VIRS), a five-channel visible/infrared radiometer.
The purpose of the 3B42 algorithm is to produce TRMM-adjusted merged-infrared (IR) precipitation rate (in mm/hr) and root-mean-square (RMS) precipitation-error estimates. The algorithm combines multiple independent precipitation estimates from the TMI, Advanced Microwave Scanning Radiometer for Earth Observing Systems (AMSR-E), Special Sensor Microwave Imager (SSMI), Special Sensor Microwave Imager/Sounder (SSMIS), Advanced Microwave Sounding Unit (AMSU), Microwave Humidity Sounder (MHS), and microwave-adjusted merged geo-infrared (IR). All input microwave data are intercalibrated to TRMM Combined Instrument (TCI) precipitation estimates (TRMM product 3B31); the iIR estimates are computed using monthly matched microwave-IR histogram matching; then missing data in individual 3-hourly merged-microwave fields are filled with the IR estimates. After the preprocessing is complete, the 3-hourly multi-satellite fields are summed for the month and combined with the monthly accumulated Global Precipitation Climatology Centre (GPCC) rain gauge analysis using inverse-error-variance weighting to form a monthly best-estimate precipitation rate, which is TRMM Product 3B43. The final step is to scale all the 3-hourly estimates for the month to sum to the monthly value (for each gridbox separately). The final 3B42 precipitation (in mm/hr) estimates have a 3-hourly 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.
The data are stored in the Hierarchical Data Format (HDF), which includes both core and product specific metadata. The file size is about 0.74 MB (compressed).
Important Changes: After the initial Version 7 processing, it was discovered that AMSU data were neglected in the first retrospective processing of both the Version 7 TMPA (3B42/43) and TMPA-RT (3B40/41/42RT) data series, which created an important shortcoming in the inventory of microwave precipitation estimates used during 2000-2010. In addition, a coding error in the TMPA-RT replaced the occasional missings in product 3B42RT with zeros. Accordingly, both product series were retrospectively processed again. The main impact in both series was to improve the fine-scale patterns of precipitation during 2000-2010 (and for 3B4xRT into late 2012). Averages over progressively larger time/space scales should be progressively less affected. [This is the reason the lack of AMSU went undiscovered; the merger system copes very reasonably with missing data.] Nonetheless, users are urged to switch to the newest Version 7 data sets. The newest runs may be identified by the file names: V.7 3B42/43 suffix of "7A.HDF" for January 2000 - September 2010 V.7 3B4xRT suffix of "7R2.bin" for 1 March 2000 - 6 November 2012 It continues to be the case that the Version 7 3B42/43 is some 4% higher than the calibrating data set (2B31) over oceans, which is still under study. However, the initial conclusion is that it results from the sampling mismatch between the (very sparse) TCI and the (much denser) microwave constellation. At the large scales this offset seems to be nearly a proportional constant.
TRMM Product FAQ: http://disc.sci.gsfc.nasa.gov/additional/faq/precipitation_faq.shtml
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Related URL
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Description:
OPeNDAP Earth Science Data TRMM 3B42.
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Multimedia Sample
View full image
Caption:
3B42 TRMM and others combined 3 hour accumulated surface rainfall
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Geographic Coverage
(Click for Interactive Map)
Spatial coordinates
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N: 50.0
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S: -50.0
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E: 180.0
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W: -180.0
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Data Resolution
Latitude Resolution:
0.25 degree
Longitude Resolution:
0.25 degree
Horizontal Resolution Range:
10 km - < 50 km or approximately .09 degree - < .5 degree
Vertical Resolution:
Surface
Temporal Resolution:
3-hourly
Temporal Resolution Range:
Hourly - < Daily
Quality
Adjusted GPI relative error estimates are provided for each 0.25 x 0.25 degree box. There are currently no known deficiencies in the 3B42 algorithm. The quality of the 3B42 product is highly sensitive to the quality of the input data: TRMM VIRS (product 1B01), TMI (product 2A12), and TRMM Combined Instrument (TCI) (product 3B31). If the quality of the input data is less than anticipated, then the quality of 3B42 will also be less.
Access Constraints
None
Data Set Progress
IN WORK
Distribution
Distribution Media:
FTP
Distribution Size:
file size: 2250 kb
Distribution Format:
HDF
Fees:
none
Personnel
Role:
INVESTIGATOR
Phone:
301-614-6308
Fax:
301-614-5492
Email:
George.J.Huffman at nasa.gov
Contact Address:
NASA
Goddard Space Flight Center
Mailstop 612
City:
Greenbelt
Province or State:
Maryland
Postal Code:
20771
Country:
USA
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:
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
Product Readme: ftp://meso-a.gsfc.nasa.gov/pub/trmmdocs/3B42_3B43_doc.pdf 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 Huffman, G.J., 1997: "Estimates of ... Root-Mean-Square Random Error for Finite Samples of Estimated Precipitation," J. Appl. Meteor., 1191-1201.
Huffman, G.J., R.F. Adler, P. Arkin, A. Chang, R. Ferraro, A. Gruber, J. Janowiak, A. McNab, B. Rudolph, and U. Schneider, 1997: "The Global Precipitation Climatology Project (GPCP) Combined Precipitation Dataset," Bul. Amer. Meteor. Soc., 78, 5-20.
Huffman, G.J., R.F. Adler, B. Rudolph, U. Schneider, and P. Keehn, 1995: "Global Precipitation Estimates Based on a Technique for Combining Satellite-Based Estimates, Rain Gauge Analysis, and NWP Model Precipitation Information," J. Clim., 8, 1284-1295.
Interface Control Specification Between the Tropical Rainfall Measuring Mission Science Data and Information System (TSDIS) and the TSDIS Science User (TSU). Volume 4: File Specifications for TSDIS Products-Level 2 and Level 3. NASA Goddard Space Flight Center, March 17, 2000 (http://pps.gsfc.nasa.gov/).
gpi_daily-pentad_products.README file at anonymous FTP site:
ftp.ncep.noaa.gov in directory /pub/precip/TRMM/ir-products.
Extended Metadata Properties
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Creation and Review Dates
DIF Creation Date:
2011-07-19
Last DIF Revision Date:
2013-05-14
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