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Modifications to the [14] model for specular ocean emissivity have recently been suggested by [7] in order to improve the performance at high microwave frequencies. The work presented here tests both the original and modified models using a set of satellite and ground-based observations that is designed to eliminate as much as possible the dependence of the test on parameters other than the surface emission itself. Clear sky, low humidity, and low wind conditions were used exclusively to reduce the dependence of the test on atmospheric and wind-roughened sea models. Radiosonde observations (RaObs) coincident with TOPEX satellite overpasses were used to reduce errors due to inexact knowledge of the atmosphere. Our tests confirm the superior performance of the Ellison model at higher frequencies. In an effort to remove the residual bias between the models and the observations, we also suggest a parameterized modification to both models that "best fits" the models to the data. In this case, the modified Ellison model maintains its superior performance at high frequencies, suggesting that it has an inherently more accurate frequency dependence. The root mean-squared (RMS) error in the modified Ellison emissivity model, over the range of 18-40 GHz, is found to be 0.0037, which translates into a model error of approximately 1 K in terms of brightness temperatures.

Precipitation is an important environmental parameter which affects the hydrology of the land surface, coastal processes, terrain stability, and climate and global heat circulation. Understanding rainfall distribution and intensity can improve protection of environmental and human resources, and knowledge of geophysical process of land, ocean and atmosphere. Rain measurements have been historically verified using traditional rain-gauges in high detail or microwave radars that cover vast areas. Nevertheless, in order to develop more accurate rainfall forecast algorithms and validate them, the drop size distribution (DSD) of rainfall events need to be studied. Using measurements from NASA TRMM satellite and rain gauges, the raindrop size distribution will be studied and used in analyzing disdrometer rain retrieval. The comparison took place on September 15 th to 17 th , 2004 in San Juan, Puerto Rico; when the tropical storm Jeanne passed by the island of Puerto Rico, in the Caribbean. Only 4 out of 21 locations worldwide where 2DVDs have been deployed in the past are in the tropics, therefore we expect this work to provide further insight into the rainfall statistics of tropical regions.

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