Assessment and tuning of the behaviour of a microphysical characterisation scheme

摘要

The correct classification of prevailing bulk hydrometeor type within aradar resolution volume is a challenge task even if a full set ofpolarimetric radar observables is available. Indeed scattering andpropagation effects from the variety of hydrometeors present interact eachothers and sometimes, if not often, tend to obscure the characteristicsignature of each weather radar target type. This consideration is enforcedwhen the atmospheric volume is sampled with a wavelength where both Miescattering effects and attenuation start to become relevant.

In this paper, we utilize the hydrometeor classification scheme developed atthe National Severe Storms Laboratory (USA). Briefly, the scheme uses afuzzy logic approach to combine different polarimetric variables andenvironmental temperature in order to determine the most likely type ofprevalent hydrometeor in the radar volume. This means that the resultingclassification is based on two characteristics: the volume polarimetricresponses and the thermal value. The relative balance between these two ismanaged through the coefficients in the fuzzy scheme. We have observed thatthese parameters are crucial in order to get "physical reasonable result",independently from the meteorological character of the event investigated.

Our work is based on a reduced set of polarimetric variables (Z andZ_DR) as input. Data used in this study were collected by a C-band radar over weather events ranging from convective to stratiform.