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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 1B21 calculates the received power at the PR receiver input point
from the Level-0 count value which is linearly proportional to the
logarithm of the PR receiver output power. To convert the count value
to the input power, extensive internal calibrations are applied, which
are mainly based upon the system model, temperature dependence of
model parameters and many temperature sensors attached at various
locations of the PR. Periodically the input-output characteristics are
measured using an internal calibration loop for the IF unit and later
receiver stages. To make an absolute calibration, an Active Radar
Calibrator (ARC) is placed at Kansai Branch of CRL and overall system
gain of the PR is being measured every 2 months. Using the transfer
function based on the above internal and external calibrations, the PR
received power is obtained. Note that the value assumes that the
signal follows the Rayleigh fading, so if the fading characteristics
of a scatter is different, a small bias error may occur (within 1 or 2
dB).
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 1B21 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 10:10:18 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
