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TRMM Rain Rate Validation: Regional Bias of TRMM Algorithms

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Rain rates from gauge measurements and TRMM algorithms were compared to evaluate their regional biases. The comparison results show possibly region-specific seasonal differences in the bias patterns. For global applications of TRMM algorithms, biases for different regions need to be established.


Diagram for a TRMM Algorithm Process (3B42)
3B423B433G68 TMI3G68 TPR3G68 TCI


  • Time Series: Monthly time series of TRMM and gauge rain rates from January 1998 to November 2003.
  • Linear Regression: A linear relationship presented by a 'best-fit' straight line on a scatter plot of TRMM versus gauge rain rates.
  • Bias: To determine if TRMM rain rates over or under estimate gauge measurements.
  • T-test: To determine the significance (p=0.05) of the differences between the means of TRMM and gauge rain rates.

Results (Oklahoma, U.S.)

Click on image to enlarge
 Time Series chart thumbnail
Time Series
Linear Regression chart thumbnail
Linear Regression
Bias chart thumbnail
T-test Table thumbnail



Chiu, L., C. Lim, and W. Teng, 2004. Development of Agricultural Information System: Comparison of TRMM and climate division rain rates in Oklahoma, 2nd International TRMM Conference, Nara, Japan.

Chiu, L.S., Z. Liu, J. Vongsaard, S. Morain, A. Budge, P. Neville, and C. Bales, 2006. Comparison of TRMM and water district rain rates over New Mexico. Advances in Atmospheric Sciences, 23(1), 1-13.

Shin, D.-B., L.S. Chiu, and M. Kafatos, 2001. Comparison of the monthly precipitation derived from the TRMM satellite. Geophysical Research Letters, 28(5), 795-798.

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Last updated: Jun 13, 2011 01:09 PM ET