Analyses of Two Distinct Precipitation Regimes over Central Greenland Inferred from 5 Years of ICECAPS Observations

A novel method for classifying Arctic precipitation using ground-based microwave remote sensors is presented. Using differences in the spectral variation of microwave absorption and scattering properties of cloud liquid water and ice, this method can distinguish between different types of snowfall events depending on the presence or absence of condensed liquid water in the clouds associated with the precipitation. This classification scheme reveals two distinct, primary regimes of precipitation over the central Greenland Ice Sheet (GIS): one originating from fully glaciated ice clouds and the other from mixed-phase clouds. Five years of co-located, multi-instrument data from the Integrated Characterization of Energy, Clouds, Atmospheric state, and Precipitation at Summit (ICECAPS) project are used to examine cloud characteristics, meteorological properties, and large-scale circulation patterns associated with each precipitation regime. Cloud and precipitation observations from additional ICECAPS instruments illustrate distinct macro- and microphysical properties for each regime, as well as quantifying occurrence and accumulation statistics. Local meteorological data, reanalysis products, and back-trajectory analyses illustrate different synoptic-scale forcing associated with each precipitation regime. Snowfall originating from the ice clouds is coupled to deep, frontal cloud systems advecting up and over the steep terrain of the southeast Greenland coast to the central GIS. Snowfall originating from mixed-phase clouds slowly propagates from the south and southwest Greenland along a quiescent flow above the GIS. The ice cloud precipitation regime corresponds to specific North Atlantic storm tracks. These particular events are associated with low-pressure systems tracking into the Baffin Bay and across the southern tip of the GIS, which is coupled to Greenland lee cyclogenesis. In contrast, the precipitation originating from the mixed-phase clouds is often connected to anomalously high geopotential heights (blocking) over the entire GIS and the negative phase of the North Atlantic Oscillation.