Examination of Early Echoes of Developing Convective Storms

In this study, the characteristics of the initial radar echoes of developing convective storms are investigated. Storms are simulated using the Hebrew University Cloudy Model (HUCM), a two-dimensional non-hydrostatic model with spectral bin microphysics, and the associated polarimetric variables are calculated using a coupled polarimetric operator. The impacts of changing various environmental parameters are investigated and discussed, with a focus on the implications for storm-scale radar data assimilation and the reduction of spin-up time. Additionally, the relations between latent heating rate, the polarimetric radar variables, and their temporal derivatives are also examined via the results of the HUCM simulations.

Analysis of the polarimetric characteristics of the first echoes observed in deep convective storms reveals enhanced values of differential reflectivity (Z_DR) and reduced values of correlation coefficient (ρ_hv), indicative of strong size sorting processes. As a result, the relations between rain and ice water content and the polarimetric radar variables during the initial stage of convective development are significantly different from the ones applicable during the mature or dissipating stages of the cloud cycle. This should be taken into account in microphysical retrievals using multiparameter radar data.