SNOW BREEZES IN THE BOREAL FOREST

This study examines thermally induced flows (or ''snow breezes'') asso ciated with snow cover in the boreal forest's of Canada. Observations from a lake less than 4 km across were made as part of the Boreal Ecos ystem-Atmosphere Study (BOREAS) winter field campaign. These are inter preted with the aid of idealized three-dimensional mesoscale model sim ulations representing the forest-lake contrast. Typically, strong fore st-lake temperature contrasts develop in the lowest 50 m of the atmosp here during the morning. The resulting pressure gradients induce low-l evel onshore wind components across the lake.;This snow breeze persist s into the afternoon provided that large-scale winds remain light. A c haracteristic snow breeze signature is clearly evident in wind observa tions averaged over 27 days of data, in agreement with model simulatio ns. The study Suggests that snow breezes will regularly develop over t he many larger lakes and other unvegetated areas in the region.