Observed differences of triple-frequency radar signatures between snowflakes in stratiform and convective clouds

Abstract

Observed triple-frequency signatures of snowflakes are investigated using a coincident dataset of the CloudSat Cloud Profiling Radar (CPR) and the Global Precipitation Measurement Dual-frequency Precipitation Radar (DPR) over ocean. A clear difference is noticed in the triple-frequency signatures between stratiform and convective clouds. Analyzing modeled backscattering properties of various snow particles, it is shown that this difference is likely to be a result of prevalent particle modes occurring in stratiform and convective clouds. Namely, snowflakes in stratiform clouds are mainly large unrimed particles (type B), while convective clouds contain abundant considerably aggregated and/or rimed particles(type C). Those very small particles with similarly weak triple-frequency signatures (type A) are less observed in both cloud types. Based on 2-year combined CPR and DPR data, the relation between snowflake types as defined above and air temperature is investigated. Results show that in stratiform clouds, type B particles dominate in warm temperature regions, while type C particles are frequently populated in cold temperature regions. In convective clouds, type B particles take up a large portion at warmer temperature regions, and type C particles are dominant across regions of a broad temperature range. This work demonstrates the potential of triple-frequency radar measurements in improving the understanding of snowflake microphysics and the modeling of snowflake single scattering properties.