Impact of the atmosphere on surface radiative fluxes and snowmelt at high latitudes

T. Zhang,.S. A. Bowling and K. Stamnes
Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK 99775

A comprehensive atmospheric radiative transfer model combined with a surface energy balance equation was applied to investigate the impact of variations of the meteorological characteristics of the atmosphere on surface radiative fluxes and snowmelt in the Arctic and Subarctic. The discrete ordinate method was used to calculate the atmospheric radiative fluxes. Variations in the incoming longwave radiation could account for the inter-annual variability of snowmelt in the Arctic and Subarctic. Under the clear sky conditions, change in the atmospheric water vapor content (WVC) is the most important single factor determining variations in incoming lonwave radiation. The overall magnitude of the temperature inversion is another important factor. Radiative fluxes are very sensitive to the temperature of the inversion but insensitive to the depth of the inversion layer. For an atmosphere with no inversion, about 87% of the incoming longwave radiation comes from the lowest 500 m of the atmosphere, about 65% from the lowest 100 m, more than 20% from the lowest 10 m and about 10% from the lowest 2 m. The coupling between the warmer, wetter atmosphere and snowmelt would enhance the warming in the Arctic and Subarctic predicted by global climate models in response to emissions of greenhouse gases.

Accepted by Journal of Geophysical Research