THE GROUND-TRUTH PROBLEM FOR SATELLITE ESTIMATES OF RAIN RATE

In this paper a scheme is proposed to use a point raingage to compare contemporaneous measurements of rain rate from a single-field-of-view estimate based on a satellite remote sensor such as a microwave radiom eter. Even in the ideal case the measurements are different because on e is at a point and the other is an area average over the field of vie w. Also the point gauge will be located randomly inside the field of v iew on different overpasses. A space-time spectral formalism is combin ed with a simple stochastic rain field to find the mean-square deviati ons between the two systems. It is found that by combining about 60 vi sits of the satellite to the ground-truth site, the expected error can be reduced to about 10% of the standard deviation of the fluctuations of the systems alone. This seems to be a useful level of tolerance in terms of isolating and evaluating typical biases that might be contam inating retrieval algorithms.