Snowfall Regimes at two Distinct Sites in Scandinavia

Snowfall is important for energy balance and the hydrologic cycle, and high-latitude precipitation is projected to change in a warming climate. Ground-based instrument suites provide opportunities to study precipitation and atmospheric characteristics that are important for understanding future changes. This work investigates snowfall regimes through measurements made from the NSF-funded High-Latitude Measurement of Snowfall (HiLaMS) project in the high-latitude winter months (November-April). The prevailing snowfall regimes at two Scandinavian sites (Haukeliseter, Norway and Kiruna, Sweden) are characterized using ground-based in-situ and remote sensing methods. Characterization of snowfall regimes include observations from a ground-based, K-band, vertically-pointing Micro Rain Radar (MRR), a custom video disdrometer Precipitation Imaging Package (PIP), and surface-based meteorological measurements. ERA5 reanalysis products provide insight to the associated synoptic scale conditions. The analyses indicate that three distinct snowfall regimes occur at both sites: shallow, deep, and intermittent snowfall. The shallow snowfall regime produces the lowest snowfall rates and occurs under regions of high pressure. Deep snowfall events are associated with weak low pressure and high relative humidity throughout the troposphere. The heaviest snowfall rates are associated with intermittent events, and the snowfall alternates between high and low intensity. The intermittent regime is associated with anomalous, deep low pressure along the coast of Norway, and enhanced relative humidity at lower levels. The analysis reveals that there are unique characteristics of shallow, deep, and intermittent snowfall regimes that are common between the sites, and supports the pursuit of characterizing snowfall regimes and processes at other high-latitude sites.