A PASSIVE MICROWAVE TECHNIQUE FOR ESTIMATING RAINFALL AND VERTICAL STRUCTURE INFORMATION FROM SPACE .2. APPLICATIONS TO SSM I DATA/

A multichannel physical approach for retrieving rainfall and its verti cal structure from SSM/I observations is examined. While a companion p aper was devoted exclusively to the description of the algorithm, its strengths, and its limitations, the main focus of this paper is to rep ort on the results, applicability, and expected accuracies from this a lgorithm. Some examples are given that compare retrieved results with ground-based radar data from different geographical regions to illustr ate the performance and utility of the algorithm under distinct rainfa ll conditions. More quantitative validation is accomplished using two months of radar data from Darwin, Australia, and the radar network ove r Japan. Instantaneous comparisons at Darwin indicate that root-mean-s quare errors for 1.25 degrees areas over water are 0.09 mm h(-1) compa red to the mean rainfall value of 0.224 mm h(-1) while the correlation exceeds 0.9. Similar results are obtained over the Japanese validatio n site with rms errors of 0.615 mm h(-1) compared to the mean of 0.880 mm h(-1) and a correlation of 0.9. Results are less encouraging over land with root-mean-square errors somewhat larger than the mean rain s ates and correlations of only 0.71 and 0.62 for Darwin and Japan, resp ectively. These validation studies are further used in combination wit h the theoretical treatment of expected accuracies developed in the co mpanion paper to define error estimates on a broader scale than indivi dual radar sites from which the errors may be analyzed. Comparisons wi th simpler techniques that are based on either emission or scattering measurements are used to illustrate the fact that the current algorith m, while better correlated with the emission methods over water, canno t be reduced to either of these simpler methods.