lake-effect-like snow storms in the Arctic

Lake-effect-like snow storms in the Arctic

Bart Geerts and Yonggang Wang, University of Wyoming

Lake-effect snow is well known to impact coastal areas near the Laurentian Great Lakes and near other mid-latitude mesoscale bodies of water such as the Baltic Sea and the Sea of Japan.  This snow grows remarkably efficiently in shallow mixed-phase clouds that form when cold air moves over ice-free water.  These clouds are highly turbulent, mainly due to a high surface buoyancy flux, and the turbulence contributes to snow growth.  This boundary-layer convective precipitation (BLCP) also occurs in arctic coastal regions when the airflow is exposed to a sufficient fetch of open water.  The cloud-microphysical processes of BLCP remain poorly understood, even at mid-latitudes.  BLCP serves as a fine example of interactions between surface fluxes, boundary-layer turbulence, shallow convection and cloud processes that are not fully represented in operational numerical weather prediction (NWP) and climate models.      

Arctic coastal waters are remaining ice-free for longer periods in a warming global climate.  The arctic sea ice extent reached another historic minimum in September 2012.  This rapid change may lead to substantial increases in boundary-layer heat and moisture fluxes over previously ice-covered waters, especially during cold-air outbreaks early in the cold season.  This may substantially increase the frequency and intensity of snowfall along the arctic coast and near downwind shores of large boreal lakes.  This will increase total precipitation and snow depth, which will impact coastal erosion, regional hydrology, and ecosystems across the arctic coastal region.

BLCP in the Arctic is inadequately documented and characterized, and poorly captured in NWP and a fortiori in climate models.  Operational NWP models do generate some BLCP, but the amount and spatial distribution of the snowfall are poorly predicted, because these models do not capture the essential cloud-scale dynamics

This poster will document the characteristics, climatology, and trend of BLCP around the Arctic, primarily using A-train satellite data (MODIS, CloudSat, CALIPSO) and data from the Atmospheric Radiation Measurement Climate Research Facility at Barrow, Alaska. This study will set the stage for an observational BLCP field campaign in the Arctic, aimed at filling a keyknowledge gap in the arctic climate system and at improving our ability to predict the arctic weather, especially snowfall.