Measurements of natural precipitation with 35 GHz scatterometer and corresponding simulations

Natural precipitation shows different size distribution patterns and great variability in space. Ground and airborne based radars are widely used for rainfall rate estimations but, looking at non homogeneous reflecting volumes, they typically average over different hydrometeors' types loosing the fine structure of precipitation. In order to improve the understanding of microphysical structure of hydrometeors we have developed a scatterometer at 35.8 GHZ, able to operate with two different linear polarization states (and therefore to determine the main depolarization parameters) and at different elevation angles. The scatterometer has been tested in an anechoic chamber with known artificial targets in the last years. Preliminary measurements have been acquired and compared with raindrops size distribution information deduced by numerical acquisitions. At the same time numerical skill have been developed by modifying a code based on T - matrix approach to compute all radar parameters: Variation of water refractive index, size and shape distribution of rain, scatterometer geometric configuration are easy to implement in this context. At the moment results are only preliminary; in the near future, measurements in dual polarization and varying elevation angle have been planned in junction with an X - band disdrometer able to acquire the size distribution of the observed natural event. (C) 2000 Elsevier Science Ltd. All rights reserved.