Abstract
The cutoff point of the snowflake (or snow and ice particle) size distribution (SSD) used for modeling the snowfall radar reflectivity and for snowfall retrievals in radar remote sensing is characterized by high uncertainties because only very limited information is available about the maximum snowflake size for different snow types and snowfall conditions. To complement previous works that examined the influence of other snowfall microphysical characteristics on the analysis of snowfall radar reflectivity, this study investigates the impact of SSD cutoff size on modeled snowfall radar reflectivity factors at X, Ku, Ka, and W band and evaluates implications for radar snowfall retrievals. While a detailed assessment can only be realized for snowfall retrieval algorithms individually, this study focuses on identifying typical snowfall characteristics where accounting for uncertainties in SSD cutoff size can be especially important. These include snowflake populations limited to a maximum snowflake size of a few mm or characterized by a small SSD (exponential) slope parameter or a large SSD (gamma distribution) shape parameter. In general, using SSD cutoff sizes that overestimate the maximum snowflake size has a smaller impact on modeled radar reflectivity and simulated snowfall retrievals than underestimating the maximum snowflake size by the same amount. Summarizing SSDs by their median volume diameter, i.e., combining SSD slope parameter, shape parameter, and cutoff size into a single characteristic snowflake size, mitigates the impact that uncertainties in these parameters can have on the analysis of snowfall radar reflectivity and may therefore offer a robust approach for relating radar snowfall retrievals to snowfall microphysics.
Published Version
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