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Liang LiaoGoddard Earth Sciences & Technology Research
Morgan State UniversityGreenbelt, MD 20771
Robert MeneghiniNASA/Goddard Space Flight Center
Greenbelt, MD 20771
Evaluation of TRMM Precipitation Radar for Estimates of Surface Rainfall Rate
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Objectives
IGARSS 2011 Vancouver
• Validating TRMM PR Measurements– Compare with the well-calibrated non-
attenuated ground-based radar measurements.
• Examining TRMM PR Algorithms– Rain attenuation correction
– Rain rate estimation
– Version-7 vs. Version-6
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IGARSS 2011 Vancouver
WSR-88D Ground-Based Radar
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IGARSS 2011 Vancouver
Earth Coordinate System
Schematic diagram of the earth coordinate system in which the latitude, , and longitude, , are defined.
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IGARSS 2011 Vancouver
Geometry for correction of PR offsets (x and y) in x and y axes at a height of h.
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IGARSS 2011 Vancouver
Radar Measurements (3/9/1998)
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IGARSS 2011 Vancouver
PR vs. WSR-88D in Melborne
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IGARSS 2011 Vancouver
Radar Reflectivity (3/9/1998) h
= 1
.5 k
mh
= 3
km
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IGARSS 2011 Vancouver
Radar Reflectivity at h=7.5 (1998-2007)
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IGARSS 2011 Vancouver
Radar Reflectivity at h=1.5 (1998-2007)
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IGARSS 2011 Vancouver
Scatter Plots of Mean Reflectivity (h=3 km)
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IGARSS 2011 Vancouver
Scatter Plots of Rain (1998-2007)
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IGARSS 2011 Vancouver
Scatter Plots of Mean Rain (1998-2007)
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IGARSS 2011 Vancouver
Area-Averaged Rain
WSR-88DTRMM PR
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IGARSS 2011 Vancouver
Area-Averaged Rain (1998-2007)
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IGARSS 2011 Vancouver
Scatter Plots of Mean Reflectivity (2008-2009)
PR (v6) vs. WSR-88D at a height of 3.0 km in MELB PR (v7) vs. WSR-88D at a height of 3.0 km in MELB
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IGARSS 2011 Vancouver
Scatter Plots of Mean Rain (2008-2009)
PR (v6) vs. WSR-88D in MELB PR (v7) vs. WSR-88D in MELB
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IGARSS 2011 Vancouver
Relative Biases (2008-2009)
)(
)()(
WSRR
WSRRPRRR
Storm Type
(Surface) R6(PR) R7(PR)
Stratiform -5.5% -3.8%
Convective -27.8% -18.8%
Ocean -22.0% -12.8%
Land -22.3% -16.6%
Coast -18.2% -14.0%
All Cases -20.9% -14.1%
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IGARSS 2011 Vancouver
Relative Bias (2008-2009)
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• Comparisons of the PR-derived reflectivities and rain rates with the same quantities derived from near-simultaneous measurements by the WSR-88D ground-based Melbourne radar are presented for more than 230 overpasses during 1998-2007.
• The reflectivity fields derived from the PR data after attenuation correction, and the conditional mean and area-averaged rain rates from the PR agree well with those obtained from the WSR-88D.
• Improvement of rain estimates is found from PR version-6 to version-7 standard products.
• Further comparisons will be conducted in the future as more data become available and these procedures will be extended to the other climatological sites.
Summary
IGARSS 2011 Vancouver