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Summary
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.
The 1C21 calculates the effective radar reflectivity factor at 13.8
GHz without any propagation loss (due to rain or any other atmospheric
gas) correction (Zm). Therefore, the Zm value can be calculated just
by applying a radar equation for volume scatter with PR system
parameters. The noise-equivalent Zm is about 21 dBZ. Through the
subtraction of the system noise, the Zm value as small as 16 or 18 dBZ
are still usable although the data quality is marginal. In 1C21, all
echoes stored in 1B21 are converted to "dBZ" unit. This is not
relevant for "non-rain" echo; however, this policy is adopted so that
the 1B21 and 1C21 product format should be as close as possible except
for the following points:
- Radar quantity is Zm in dBZ unit instead of received power (dBm).
- Data at echo-free range bins judged in 1B21 are replaced with a dummy value.
The data are stored in the Hierarchical Data Format (HDF), which
includes both core and product specific metadata applicable to the PR
measurements. A file contains a single orbit of data with a file size
of about 139 MB (uncompressed). The HDF-EOS "swath" structure is used
to accommodate the actual geophysical data arrays. There are 16 files
each of PR 1C21 produced per day.
Spatial coverage is between 38 degrees North and 38 degrees South,
owing to the 35 degree inclination of the TRMM satellite. There are,
in general, 9150 scans along the orbit, with each scan consisting of
49 rays. The scan width is about 220 km.
Contacts for Data Access Information
Goddard DAAC
Hydrology Data Support Team, Code 610.2
NASA Goddard Space Flight Center
Greenbelt, MD 20771
301-614-5224 voice
301-614-5268 fax
Email: help-disc@listserv.gsfc.nasa.gov
Data Center Identification
GSFC-TSS -
Goddard Space Flight Center Distributed Active Archive Center, NASA
References:
Tropical Rainfall Measuring Mission Science Data and Information System (TSDIS)
Interface Control Specification Between the TSDIS and the TSDIS Science User (TSU)
Volume 3: File Specifications for TRMM Products - Level 1,
http://pps.gsfc.nasa.gov/tsdis/Documents/ICSVol3.pdf
Volume 4: File Specifications for TRMM Products - Level 2 and Level 3,
http://pps.gsfc.nasa.gov/tsdis/Documents/ICSVol4.pdf
Document Information
Document Revision Date:Fri May 17 10:10:24 EDT 2002
Document Review Date: Wed May 15 10:24:19 EDT 2002
Document Author: Hydrology Data Support Team
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Atmos Composition
