Solar and Daytime Infrared Irradiance during Winter Chinooks

Abstract

Chinook winds bring unseasonably warm temperatures to southern Alberta in the winter. They also melt the snow and evaporate, the surface and near surface soil water. Hitherto, the warmth of the wind had almost exclusively been linked to the adiabatic warming of airstreams of Pacific origin blowing down the Rockies. Measurements of components of the radiation balance and the variables that control them, made in an equal number of clear sky winter chinook days and arctic airmass chinook-free weather, show that the chinook has the potential to increase its own warmth because albedo is lower and atmospheric humidity higher. Infrared emissivity is smaller during a chinook due perhaps to the vertical distribution of water vapor and temperature.