Retrievals of ice hydrometeor shapes using polarimetric radar measurements

Sergey Matrosov

CIRES and NOAA Physical Sciences Laboratory

Tuesday, Oct 20, 2020, 2:00 pm
Webinar

Abstract

Knowing a general shape of atmospheric ice particles is important for many practical applications ranging from validation of the advanced cloud and precipitation models, which predict particle shapes, to radar-based snowfall quantitative precipitation estimation (QPE) methods. This presentation describes a novel remote sensing method to retrieve shape parameters of ice hydrometeors expressed by mean aspect ratios, which are defined as the minor-to-major particle dimension ratios. This method uses polarimetric radar measurements for the aspect ratio retrievals. The variables used for retrievals include reflectivity, differential reflectivity, and the copolar correlation coefficient. The retrievals are applied to a wide range of conditions ranging from non-precipitating ice clouds to heavy snowfall observed at the U.S. Department of Energy’s Alaska facilities. The retrievals of ice hydrometeor shapes were validated using collocated in situ particle measurements from ground and balloon-borne sensors. It is shown that the radar-based retrievals are able to provide quantitative information on changes of dominant particle habits due to processes of crystal growth, aggregation, and riming. The retrievals are used to develop statistical relations between mean ice particle aspect ratios and ambient temperature. The retrieval method can be potentially modified for the use with operational weather radars. Examples of the snowflake shape retrievals using NEXRAD measurements will be shown.