Retrieval of storm microphysics using K_a band radarobservations

摘要

Polarimetric radar measurements can be used to deduce the shapeand orientation of non-spherical scatterers in the Rayleigh scatteringregime. At K_a-band and for larger sized particles, Miescattering effects dominate by introducing oscillations in differentialbackscattering parameters. Albeit at these frequencies deducing the meanshape of non-spherical scatterers might be difficult, radarbackscattering signatures like the linear depolarization ratio (LDR),differential propagation phase (KDP) and co-polar cross-correlationcoefficient provide information about the thermodynamic phase state ofthe scatterers. Tumbling non-spherical particles such as graupel andhail, exhibit enhanced depolarization characteristics which can be usedto delineate regions of ice, melting-ice and rain. Additionally, forwardscattering parameters such as attenuation and differential attenuationbetween H and V polarized waves display monotonic increase with the sizeof the scatterer. Polarimetric radar modeling of hydrometeors such asgraupel, hail and rain at 35 GHz (K_a-band) based on theMueller matrix formulation is presented. The various transitorythermodynamic phase states of ice hydrometeors have also beenincorporated in the modeling. In the Rayleigh regime scatteringparameters such as differential reflectivity and LDR are used toinvestigate the feasibility of deducing the mean axis-ratio and spreadin the canting angle distributions of these types of hydrometeors. Themodeling results could be applied to understand and interpret LDRsignatures recorded by airborne radars with vertical incidence