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TRMM Product Level 2A Precipitation Radar (PR) Surface Cross Section (2A21)

Online Access for TRMM 2A21:

2A21: http://mirador.gsfc.nasa.gov/cgi-bin/mirador/presentNavigation.pl?tree=project&dataset=2A21%20%28Version%20007%29:%20Radar%20Surface%20Cross-Section%20%28PR%29&project=TRMM&dataGroup=Orbital&version=007


Contents:

Summary

This document provides basic information on 2A21, the TRMM Precipitation Radar (PR) Surface Cross Section data product.

The TRMM 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 sigma zero algorithm (2A21) inputs the PR power (1B21) and computes an estimate of the path attenuation and its reliability by using the surface as reference target. It also computes the spatial and temporal statistics of the surface scattering cross section and classifies the cross sections into land/ocean and rain/no rain categories.

 

Data Flow Description

PR Level 1A ==> 1B21 PR Power ==> 2A21 PR Surface Cross Section

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

Data Set Description

Data Characteristics

TRMM 2A21 (PR) Data Characteristics
  Pre-boost (before 2001-08-07) Post-boost (after 2001-08-24)
Temporal Coverage Start Date: 1997-12-08
Stop Date: 2001-08-07
Start Date: 2001-08-24
Stop Date: -
Geographic Coverage Latitude: 38°S - 38°N
Longitude:180°W - 180°E
Latitude: 38°S - 38°N
Longitude:180°W - 180°E
Temporal Resolution About 91.5 minutes per orbit
About 16 orbits per day
More information about revisit frequency
About 92.5 minutes per orbit
About 16 orbits per day
More information about revisit frequency
Horizontal Resolution 4.3 km 5.0 km
Scan Characteristics Swath Width: 215 km
Rays/Scan: nray = 49
Scans/Second (SS): 1/0.6
Seconds/Orbit (SO): 5490
Average Scans/Orbit: nscan = SS*SO = 9150
Swath Width: 247 km
Rays/Scan: nray = 49
Scans/Second (SS): 1/0.6
Seconds/Orbit (SO): 5550
Average Scans/Orbit: nscan = SS*SO= 9250
Average File Size Compressed: ~11 MB Compressed: ~11 MB
File Type HDF HDF

Data Format Structure

Further information on the contents and structure of the 2A21, PR Surface Cross Section product can be found in File Specifications for TRMM Products - Version 7.00

Data Format Structure for 2A21, PR Surface Cross Section
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.
Swath Structure Char Attribute 5,000  - - - - Specification of the swath geometry.
Scan Time Vdata Table nscan - - - Time associated with the scan, expressed as 8-byte float UTC second of the day.
Latitude Float SDS 4 nray*nscan - - degree Earth location of the center of the IFOV at the altitude of the earth ellipsoid. The first dimension is latitude and longitude, in that order. The next dimensions are numbers of pixels and scans.
Longitude Float SDS 4 nray*nscan - - degree Earth location of the center of the IFOV at the altitude of the earth ellipsoid. The first dimension is latitude and longitude, in that order. The next dimensions are numbers of pixels and scans.
Scan Status Vdata Table 15  nscan - - - Status of each scan.
Navigation Vdata Table 88  nscan - - - Spacecraft geocentric information.
Sigma-zero Float SDS 4 nray*nscan - -50.0 ~ 50.0 dB Normalized surface cross section.
Pat Attenuation Float SDS 4 nray*nscan - -50.0 ~ 50.0 dB Estimate of positive 2-way integrated attenuation dB when rain is present.
Reliability Flag Integer SDS nray*nscan - - - Various reliability information in the form of single digit flags.
Reliability Factor Float SDS nray*nscan - -10 ~ 10 - Ratio of the estimated value of path attenuation
to standard deviation associated with the mean value
of the reference estimate
Incident Angle Float SDS 4 nray*nscan - -30.0 ~ +30.0 degree Angle, in degree, between the PR nadir and the radar beam.
Rain Flag Integer SDS nray*nscan - - 0 or 1 Rain flag. 0: no rain, 1: Rain present.

TRMM 2A21 can be accessed and ordered using the Goddard DISC's TRMM Data Search and Order System at

http://mirador.gsfc.nasa.gov/cgi-bin/mirador/presentNavigation.pl?tree=project&dataset=2A21%20%28Version%20007%29:%20Radar%20Surface%20Cross-Section%20%28PR%29&project=TRMM&dataGroup=Orbital&version=007


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Last updated: Mar 15, 2013 02:51 PM ET
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