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Keywords:

  • Arctic;
  • radar;
  • precipitation;
  • low-level convection;
  • GEM-LAM 2.5

Abstract

Small accumulation precipitation events are critical for the high-latitude hydrological cycle. They contribute to more than 50% of total accumulation in the area and occur at a greater frequency than high-accumulation events. Despite their importance, the processes controlling them have not been investigated in sufficient detail. This study characterizes an unexpected high-latitude snowfall event at Iqaluit, Nunavut, and surrounding area during the Storm Studies in the Arctic field project. High-resolution data collected, from both ground based and airborne Doppler radar, along with upper air and surface observations, provided the basis for analysis of the conditions that led to the event and offer some insight as to why it was not well forecast by the Canadian operational model. Several factors worked in concert to produce this event. Low-level convection and upslope processes were important in cloud and precipitation generation over the orography upstream. When combined with additional lift from the passing of a weak trough, cloud and precipitation production were enhanced, allowing these features to penetrate over the terrain and resulted in precipitation at Iqaluit. Analysis of the global environmental multiscale limited area model (2.5 km resolution) suggests that upstream convection and upslope processes were affected by model errors. As a consequence, precipitation onset was delayed, and the total accumulation was 50% lower than the observations. Results indicate that the complexity of precipitation events in the region represents a significant challenge for predicting and modeling and understanding their role in the region's hydrological cycle.