5b.16
Numerical simulation of an Arctic ground blizzard
Stephen J. Déry, McGill University, Montreal, PQ, Canada; and M. K. Yau
A ground blizzard occurred from 16 to 18 November 1996 in the northern sectors of the Mackenzie River Basin (MRB) of Canada and adjacent Beaufort Sea. This hazardous event, accompanied by a low-level jet with wind speeds approaching 20 m/s and extensive blowing snow near the surface (but clear sky aloft), is forced by a strong sea-level pressure gradient that forms between a rapidly intensifying anticyclone over the Nunavut and Northwest Territories (NWT) of Canada and an intense depression over the frozen Arctic Ocean.
The event is first simulated at a horizontal grid size of 18 km using the uncoupled Canadian Mesoscale Compressible Community (MC2) model. This experiment is shown to capture the rapid anticyclogenesis event within 2 hPa of its central sea-level pressure and the blizzard conditions near the Canadian Arctic coastline and the Beaufort Sea. Meteorological conditions observed at Trail Valley Creek (TVC), a small Arctic tundra watershed where ground blizzard conditions were experienced during the event, are also accurately reproduced by the uncoupled simulation with the notable exception of the blowing snow process. Thus, the mesoscale model is then coupled to the PIEKTUK blowing snow model and a second simulation is conducted. This additional experiment reveals the presence of extensive blowing snow associated with a strong low-level jet over TVC and the adjacent frozen Beaufort Sea. Our findings show that blowing snow affects the surface mass balance through sublimation and transport which combine to erode about 1.4 mm snow water equivalent (swe) per day at TVC. The concurrent moistening and cooling of near-surface air due to blowing snow sublimation emerge during the blizzard, but to a lesser extent than in an idealized modelling framework as a consequence of entrainment and horizontal advection. Therefore, blowing snow sublimation rates are evaluated to be 1.8 times larger than in the stand-alone application of the PIEKTUK model to the same data. We will also discuss the effects of blowing snow sublimation to the surface energy budget.
Session 5b, Polar Weather Forecasting: Continued (Parallel with Session 5A)
Friday, 18 May 2001, 10:30 AM-12:30 PM
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