The annual cycle of snowfall at Summit, Greenland

Abstract

While snow accumulation over central Greenland has been extensively studied, interannual variability of snowfall in the region is not well understood due to a dearth of observations. The Integrated Characterization of Energy, Clouds, Atmospheric state and Precipitation at Summit (ICECAPS) project at Summit, Greenland, offers a unique, ground-based opportunity to study precipitation in central Greenland where the surface mass balance is positive. Combining data from a Precipitation Occurrence Sensor System (POSS), Millimeter-wavelength Cloud Radar (MMCR), and snow stake field, the annual cycle of precipitation at Summit is examined. Average daily snowfall is higher by a factor of 3 from June to October compared to November to May, while surface height change is only higher by 15% during the same timeframes. This reduced variability in surface height is explained by the seasonally varying nature of latent heat flux, compaction, and wind contributions. The ICECAPS remote sensors and stake field measurements do not agree as far as total annual water equivalent. This discrepancy is likely due to a low bias in the POSS and MMCR snowfall retrievals for Summit. To further examine the seasonal cycle, snowfall measurements by the POSS were linked to local meteorological parameters, including wind direction, liquid water path (LWP), 2 m temperature, and precipitable water vapor. An observed wind direction and moisture dependence are consistent with snowfall being linked to pulses of moist air that originate over nearby, ice-free ocean, a resource that becomes more readily available in summertime as the winter sea ice retreats. LWP is shown to have little relationship to snowfall, indicating that ice-phase precipitation processes are quite important for snowfall at Summit.

A Shallow Cumuliform Snowfall Census Using Spaceborne Radar

“…These radar observations can readily discriminate snowfall modes and can be exploited as an independent assessment tool (e.g., Kneifel et al 2011;Castellani et al 2015). For instance, future studies will assess whether numerical models realistically represent shallow convective snowfall and global reanalyses datasets (e.g., spatially, seasonally, and from a precipitation intensity and accumulation fraction perspectives).…”

The meteorology and chemistry of high nitrogen oxide concentrations in the stable boundary layer at the South Pole

“…However, in contrast, direct measurements of BLD at Summit Station Greenland (3216 m a.s.l., 72.6 • N, 38.5 • W) show values of NO in the range of only 10-30 pptv with BLD on the order of 5 m (Van Dam et al, 2013). One potential explanation for this difference is the high snow accumulation rate in the summer at Summit Station of 5.0 to 7.5 cm month −1 in the summer, maximizing in July (Castellani et al, 2015).…”

Evaluation of CloudSat's Cloud‐Profiling Radar for Mapping Snowfall Rates Across the Greenland Ice Sheet

“…Yet observations from the dry, high-elevation interior of the ice sheet may not necessarily evaluate a model's ability to simulate accumulation at the wetter, ablating margins. Secondly, ice cores are almost always used to evaluate modeled accumulation at an annual to decadal temporal resolution (e.g., Fettweis et al, 2017;Noël et al, 2018), precluding evaluation of a model's ability to simulate accumulation over monthly or seasonal timescales (e.g., Castellani et al, 2015;Dibb & Fahnestock, 2004;Pettersen et al, 2018). Finally, most of the spatially distributed firn and ice cores were collected during the 1990s (Mosley- Thompson et al, 2001) and may not be representative of 21st century climate, a period of anomalously low surface mass balance.…”