Abstract
Abstract. A novel method for classifying Arctic precipitation using ground based 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 that generate the precipitation. The classification reveals two distinct, primary regimes of precipitation over the 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) are used to examine cloud and meteorological properties and patterns associated with each precipitation regime. The occurrence and accumulation of the precipitation regimes are identified and quantified. Cloud and precipitation observations from additional ICECAPS instruments illustrate distinct characteristics for each regime. Additionally, reanalysis products and back-trajectory analysis show different synoptic-scale forcings associated with each regime. Precipitation over the central GIS exhibits unique microphysical characteristics due to the high surface elevations as well as connections to specific large-scale flow patterns. Snowfall originating from the ice clouds is coupled to deep, frontal cloud systems advecting up and over the southeast Greenland coast to the central GIS. These events appear to be associated with individual storm systems generated by low pressure over Baffin Bay and Greenland lee cyclogenesis. Snowfall originating from mixed-phase clouds is shallower and has characteristics typical of supercooled cloud liquid water layers, and slowly propagates from the south and southwest of Greenland along a quiescent flow above the GIS.
Highlights
The Greenland Ice Sheet (GIS) is losing mass at an accelerating rate (Shepherd et al, 2012)
We utilize the differences between low frequency (LF) and high frequency (HF) channels when ice is present, coupled with the ability of the microwave radiometers (MWRs) to detect cloud liquid water (CLW), to classify snowfall events into categories: events with snow originating from fully glaciated ice clouds (IC snow), events occurring with a measurable amount of cloud liquid water in the column (CLW snow), and events where we cannot assign a distinct cloud type (Indeterminate snow)
We introduced a MWR-based method for classifying the precipitation at Summit to discriminate snow events originating from fully glaciated ice clouds (IC) from those associated with mixed-phase clouds (CLW)
Summary
The Greenland Ice Sheet (GIS) is losing mass at an accelerating rate (Shepherd et al, 2012). We utilize the differences between LF and HF channels when ice is present, coupled with the ability of the MWR to detect cloud liquid water (CLW), to classify snowfall events into categories: events with snow originating from fully glaciated ice clouds (IC snow), events occurring with a measurable amount of cloud liquid water in the column (CLW snow), and events where we cannot assign a distinct cloud type (Indeterminate snow). These profiles are correlated with features of fully glaciated and mixed-phase clouds, respectively Using reanalysis and back-trajectory data, we further study the relationship of IC and CLW events with large-scale forcings (Sect. 5)
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