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TRMM Precipitation Radar (PR) Level 2 Rainfall Rate and Profile Product (TRMM Product 2A25)

Entry ID: GES_DISC_TRMM_2A25_V7

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Summary

Abstract: 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 objectives of 2A25 is to correct for the rain attenuation in measured radar reflectivity and to estimate the ... instantaneous three-dimensional distribution of rain from the TRMM Precipitation Radar (PR) data. The estimates of attenuation-corrected radar reflectivity factor and rainfall rate are given at each resolution cell of the PR. The estimated near-surface rainfall rate and average rainfall rate between the two pre-defined altitudes (2 and 4 km) are also calculated for each beam position.

2A25 basically uses a hybrid of the Hitschfeld-Bordan method and the surface reference method to estimate the vertical true radar reflectivity (Z) profile. (The hybrid method is described in Iguchi and Meneghini (1994)). The vertical rain profile is then calculated from the estimated true Z profile by using an appropriate Z-R relationship.

The attenuation correction is, in principle, based on the surface reference method. This method assumes that the decrease in the apparent surface cross section (delta sigma-zero) is caused by the propagation loss in rain. The coefficient a in the k-Z relationship, k=a Z**b, is adjusted in such a way that the path-integrated attenuation (PIA) estimated from the measured Zm-profile will match the delta sigma-zero. The attenuation correction of Z is carried out by the Hitschfeld-Bordan method with the modified a. Since a is adjusted, this type of surface reference method is called the a-adjustment method. The a-adjustment method assumes that the discrepancy between the PIA estimate from delta sigma-zero and that from the measured Zm-profile can be attributed to the inappropriate choice of a values, which may vary depending on the raindrop size distribution and other conditions. It assumes that the radar is properly calibrated and that the measured Zm has no error.

In order to avoid inaccuracies in the attenuation correction when rain is weak, a hybrid of the surface reference method and the Hitschfeld-Bordan method is used (Iguchi and Meneghini, 1994). The PIA is first estimated from the precipitation echo alone. The weight given by the hybrid method to the PIA estimate from the surface reference increases as the attenuation estimate increases. When rain is very weak and the attenuation estimate is small, the PIA estimate from the surface reference is effectively neglected. With the introduction of the hybrid method, the divergence associated with the Hitschfeld-Bordan method is also prevented.

One major difference from the method described in the above reference is that, in order to deal with the beam-filling problem, a non-uniformity parameter is introduced and is used to correct the bias in the surface reference arising from the horizontal non-uniformity of rain field within the beam. Since radar echoes from near the surface are contaminated by the mainlobe clutter, the rain estimate at the lowest point in the clutter-free region is given as the near-surface rainfall rate for each angle bin.

Spatial coverage is between 38 degrees North and 38 degrees South, owing to the 35 degree inclination of the TRMM satellite. This orbit provides extensive coverage in the tropics and allows each location to be covered at a different local time each day, enabling the analysis of the diurnal cycle of precipitation. There are, in general, 9150 scans along the orbit, with each scan consisting of 49 rays. The scan width is about 220 km.

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 242 MB (uncompressed). The HDF-EOS "swath" structure is used to accommodate the actual geophysical data arrays. There are 16 files of PR 2A25 data produced per day.

Related URL

Link: GET DATA

Description: Data access for TRMM Precipitation Radar (PR) Level 2 Rainfall Rate and Profile Product, TRMM 2A25

Link: GET DATA > MIRADOR

Description: The Mirador Earth Science Data Search Tool includes TRMM 2A25, Level 2A-25F Precipitation rate profile. Mirador features include location and event gazetteers.

Link: VIEW RELATED INFORMATION

Description: Documentation and data access for TRMM Precipitation Radar (PR) Level 2 Rainfall Rate and Profile Product, TRMM 2A25

Link: VIEW RELATED INFORMATION

Description: Information and data access for all of the Goddard DAAC's hydrology data holdings, including TRMM data from the TMI, Precipitation Radar (PR) and Visible and Infrared Scanner (VIRS) instruments, the Ground Validation (GV) radar data, and ancillary and correlative data products.

Geographic Coverage

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Spatial coordinates

N: 38.0

S: -38.0

E: 180.0

W: -180.0

Data Set Citation

Dataset Originator/Creator: NASA, JAXA, Tropical Rainfall Measuring Mission (TRMM)

Dataset Title: TRMM Precipitation Radar (PR) Level 2 Rainfall Rate and Profile Product (TRMM Product 2A25)

Version: 7

Online Resource: http://mirador.gsfc.nasa.gov/cgi-bin/mirador/presentNavigation.pl?t...

Temporal Coverage

Start Date: 1997-12-07

Location Keywords

GEOGRAPHIC REGION > TROPICS

Data Resolution

Latitude Resolution: 4 km
Longitude Resolution: 4 km
Horizontal Resolution Range: 1 km - < 10 km or approximately .01 degree - < .09 degree
Vertical Resolution: 250 m
Vertical Resolution Range: 100 meters - < 1 km
Temporal Resolution: 16 orbits per day
Temporal Resolution Range: Daily - < Weekly

Science Keywords

ATMOSPHERE > PRECIPITATION > PRECIPITATION AMOUNT

ATMOSPHERE > PRECIPITATION > PRECIPITATION ANOMALIES

ATMOSPHERE > PRECIPITATION > PRECIPITATION RATE

ISO Topic Category

CLIMATOLOGY/METEOROLOGY/ATMOSPHERE

IMAGERY/BASE MAPS/EARTH COVER

Platform

TRMM > Tropical Rainfall Measuring Mission

Instrument

PR > TRMM Precipitation Radar

Project

EOS > Earth Observing System

EOSDIS > Earth Observing System Data Information System

Quality Scan Status is provided 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
...

Access Constraints None

Ancillary Keywords

EOSDIS

Data Set Progress

IN WORK

Originating Center

GSFC_GES_DISC

Data Center

Goddard Earth Sciences Data and Information Services Center (formerly Goddard DAAC), Global Change Data Center, Earth Sciences Division, Science and Exploration Directorate, Goddard Space Flight Center, NASA

Data Center URL: http://disc.gsfc.nasa.gov/

Data Center Personnel
Name: GES DISC HELP DESK SUPPORT GROUP Phone: 301-614-5224 Fax: 301-614-5268 Email: gsfc-help-disc at lists.nasa.gov Contact Address: Goddard Earth Sciences Data and Information Services Center Code 610.2 NASA Goddard Space Flight Center City: Greenbelt Province or State: MD Postal Code: 20771 Country: USA

Distribution

Distribution Media: FTP

Distribution Size: 15-16 file/day; 19000-20000 kb/file

Distribution Format: HDF

Fees: none

Personnel

HYDROLOGY DATA SUPPORT TEAM

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

TOSHIO IGUCHI

Role: INVESTIGATOR

Phone: 81-299-84-7117

Fax: 81-299-84-7157

Email: iguchi at crl.go.jp

Contact Address:

Communications Research Laboratory

Global Environment Division

4-2-1 Nukui-Kita-Machi

City: Koganei,

Province or State: Tokyo

Postal Code: 184-8795

Country: Japan

HYDROLOGY DATA SUPPORT TEAM

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

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

...

Extended Metadata Properties

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Creation and Review Dates

DIF Creation Date: 2011-07-15

Last DIF Revision Date: 2013-03-22

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