Microwave Rain Gauge

This proposal describes a plan for the Design and Development of line of sight area averaged rain measurements using microwave backscatter techniques. The line averaged (and area covered) could be made variable, from as low as 100m to several km. The individual units can thus be used for both local measurements as well as for extending the observation over rain-cells. The techniques might be extended using multi-frequency and other techniques to obtain independent estimates of drop size distribution. Both microwave attenuation and phase-shift are potential candidates for measuring rain rates. Microwave attenuation increases with frequency up to 100 GHz. The choice of appropriate frequencies is important, and optimization may become necessary in terms of available technology, cost and accuracies. The proposed effort describes a plan to develop a versatile instrument for measuring backscattered attenuation and phase at several frequencies. Experiments performed using the instrument will allow us to infer the optimum system parameters during Phase II. Such a system will be valuable for earth communities, scientific research, global environment, agriculture and forestry among others. It would be valuable for NASA in estimating the ground truth and calibration and for comparison with the TRMM Rain Radar.