Polarimetric X-band weather radar measurements in the tropics: radome and rain attenuation correction

[摘要] A polarimetric X-band radar has been deployed during one month (April 2011)for a field campaign in Fortaleza, Brazil, together with three additionallaser disdrometers. The disdrometers are capable of measuring the raindropsize distributions (DSDs), hence making it possible to forward-modeltheoretical polarimetric X-band radar observables at the point where theinstruments are located. This set-up allows to thoroughly test the accuracyof the X-band radar measurements as well as the algorithms that are used tocorrect the radar data for radome and rain attenuation. For the campaign inFortaleza it was found that radome attenuation dominantly affects themeasurements. With an algorithm that is based on the self-consistency of thepolarimetric observables, the radome induced reflectivity offset wasestimated. Offset corrected measurements were then further corrected for rainattenuation with two different schemes. The performance of thepost-processing steps was analyzed by comparing the data withdisdrometer-inferred polarimetric variables that were measured at a distanceof 20 km from the radar. Radome attenuation reached values up to 14 dB whichwas found to be consistent with an empirical radome attenuation vs. rainintensity relation that was previously developed for the same radar type. Incontrast to previous work, our results suggest that radome attenuation shouldbe estimated individually for every view direction of the radar in order toobtain homogenous reflectivity fields.

[学科分类] 几何与拓扑