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Observation and Simulation of Arctic Boundary Layer Clouds Associated With a Polynya During FIRE.ACE |
Meteorological Service of Canada,
(1) Recherche en prevision numerique, Dorval, QC, Canada,
(2) Cloud Physics Division, Toronto, ON, Canada,
(3) Cloud Physics Division, Dorval, QC, Canada
Measurements over a large polynya in the Beaufort Sea were made with the Canadian Convair-580 aircraft during FIRE.ACE. Instrumentation onboard the aircraft provided detailed observations of surface sensible and latent heat fluxes, and cloud thermodynamical and microphysical properties. On 25 April 1998, strong surface heat fluxes were associated with cold air advection over the polynya and a cloud formed at the top of the Arctic boundary layer, downwind of the polynya. On 29 April 1998, because of warm air advection, smaller surface fluxes were observed with no indication of cloud formation. Both cases have been simulated using a mesoscale model (MC2) at 2-km resolution, with a detailed treatment of surface processes over land and sea ice and with the actual observed structure of the large polynya. The sensitivity of the Arctic boundary layer cloud formation and properties to various surface and microphysical processes are examined. The model evolution of the Arctic boundary layer over the polynya, together with the characteristics of the associated clouds are compared with the detailed in situ aircraft observations.
