An Estimate of Horizontal Heat Transport during a Chinook

Abstract

The chinook is the best example of the family of mountain winds that blows in regions where long mountain chains lie more or less at right angles to the prevailing wind. Apart from the unseasonable warmth it brings to the continental interior in winter, it represents an efficient system through which latent heat drawn from the Pacific coast is converted to sensible heat and transported zonally across the continent. Estimates of the quantities of heat involved and their significance are based on analyses of the radiation balance and average surface air temperatures measured during chinooks and chinook-free weather. Average daily net radiation is 22% lower during a chinook than during chinook-free weather. Net longwave radiation loss is 58% more. In daytime, net radiation is positive under chinook conditions, negative in chinookless weather. Net longwave radiation is 36% smaller in the former. At night, net radiation in chinook-free weather exceeds its chinook equivalent by about 32 W m?2. Despite these net losses, surface air temperature during a chinook averages about 14.7 K higher than in chinook-free weather. The mean horizontal heat transport into the chinook bell required to sustain the temperature gain is about 1.52 ? 1015 W. Daytime and nightlime values are 1.59 ? 1015 and 1.46 ? 1015 W, respectively.