Validation and Analysis of Microwave-Derived Rainfall Over the Tropics
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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A recently developed single channel microwave rain rate retrieval algorithm exists to measure global precipitation over the data-sparse tropical oceans. The objective of this study is to retrieve and validate rainfall using this algorithm, followed by an analysis of the derived rainfall fields. Retrieval consists of applying the algorithm technique to the extraction of four years worth of achieved data from the Electrically Scanning Microwave Radiometer ESMR instrument flown aboard the NIMBUS 5 satellite. The Pacific Atoll Raingage Data Set is chosen as a ground truth measure to validate the ESMR- Derived rainfall data against, comparing slope, intercept and correlation between 5 deg x 5 deg area average. Despite limitations imposed by the comparison of point measurements to area-averaged rainfall, results show a 0.80 correlation. Monthly and quarterly climatological mean rainfall estimates are produced, with a consequent analysis of prominent signals, especially in the Intertropical Convergence Zone ITCZ, South Pacific Convergence Zone SPCZ and the Indian monsoon. Latent heat flux is computed, using the ESMR-derived rainfall, and plotted to show qualitatively where seasonal latent thermodynamic energy sources and sinks exist in the atmosphere. A comparison of the summer and winter quarterly composites of the above products with previously compiled climatologies and Outgoing Longwave Radiation OLR showed only minor discrepancies in location and intensity, which are discussed in some detail.