Characterization of orographic cloud and precipitation features over southern Baffin Island and surrounding area

• Main Author: Fargey, Shannon
• Other Authors: Hanesiak, John (Environment and Geography), Stewart, Ronald (Environment and Geography) Stadnyk, Tricia (Civil Engineering) Dery, Stephen (Environmental Science and Engineering, University of Northern British Columbia)
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Taylor & Francis Publishing 2014
• Subjects: Arctic; cloud; precipitation; Baffin Island; Nunavut; Baffin; Sea ice
• Online Access: http://hdl.handle.net/1993/23730

Improved characterization of cloud and precipitation features are required to understand the impact of a changing climate in high latitude regions and accurately represent these features in models. The importance of cold season precipitation to regional moisture cycling and our limited understanding of orographic cloud and precipitation processes in the Arctic provide the motivation for this research. Using high-resolution datasets collected during the Storm Studies in the Arctic (STAR) field project this thesis examines cloud and precipitation features over southern Baffin Island in Nunavut. Cloud and precipitation features were shown to differ over orography compared to the adjacent ocean regions upstream. Gravity waves, terrain shape, atmospheric stability and atmosphere-ocean exchanges were all associated with precipitation enhancement. In addition, high sea ice extent, low-level blocking in the upstream environment and sublimation were factors that reduced precipitation. The nature of hydrometeors was variable and accretion and aggregation were found to be important determinants of whether precipitation reached the ground. The processes controlling a snowfall event over southern Baffin Island were found to be complex, representing a significant challenge for modelling in the region. Low-level convection over adjacent ocean regions, strong upslope flow over the terrain, and the passing of a weak trough collectively produced the event. Analysis of the Global Environmental Multi-scale limited area model (GEM-LAM 2.5) revealed that upstream convection and upslope processes were affected by model errors. Consequently, precipitation onset was delayed and total modelled accumulation was 50% less than observations. Further evaluation of a numerical weather prediction model during STAR cases provided descriptions of model errors and proficiencies for different synoptic forcing and surface environments. Overall the model overestimated temperature and had difficulties representing thermal inversions over sea ice. The ...