Microwave radiometer snow categorization tool for Summit, Greenland, 2010 - 2015

This product categorizes snowfall events at Summit Station, Greenland by their associated cloud type using observations from the NSF ICECAPS project. The categories are determined primarily by signatures observed in ground based microwave radiometers (MWR) deployed at Summit as part of the ICECAPS instrument suite. Microwave radiances have differing sensitivity as a function of frequency to different atmospheric components. For ground-based MWRs, the observed signals at all frequencies include contributions from gases like water vapor and oxygen as well as from clouds (when in the field of view of the radiometer). The spectral regions between these gaseous absorption features are referred to as “windows”, where the contribution from the gases is relatively small. The 31.40 and 150 GHz MWR channels are considered a window channels. We designate the 150 GHz window channel as “HF” and the 31.40 GHz window channel as “LF”. When CLW is present in the column both the LF and HF channels observe emission from the condensed water, increasing the observed brightness temperature (BT). When ice hydrometeors are present in the atmosphere, they will affect the observed downwelling radiance primarily through scattering of the surface radiation back at he HF MWR channel only. By using the differences in the ratios of the HF to LF MWR observations of each scenario, we classify the snow into categories: precipitation originating from a fully glaciated ice cloud, i.e., “ice cloud (IC)” snow, precipitation originating from a mixed-phase cloud – snow that is has some CLW layers present, i.e., “CLW containing” snow, and precipitation that we cannot distinguish accurately the cloud type, i.e., “Indeterminate (IND) snow.”