A numerical, analytical and observational study of the effect of clouds on surface wind and wind stress during the central Arctic winter

Abstract

Results of measurements from several Arctic field programs and numerical models show that clouds affect wind stress during the central Arctic winter by changing the longwave cooling of the surface and cloud layers. The longwave cooling alters the thermodynamic structure of the lower atmosphere which in turn affects the efficiency of momentum transfer to the surface. For typical Arctic conditions, wind stress is changed by about 40% one hour after a cloud condition change, due to changes in both the surface layer stability and surface layer wind speed. The actual wind stress effect due to clouds during this time is a function of wind speed, thermal wind, atmospheric boundary layer depth, magnitude of radiation change, snow age and, sometimes, snow depth. After several hours, surface heat fluxes are no longer important, but the structure of the atmosphere has been permanently altered. This affects the wind stress by about 10% to 20% during certain situations, but can vary depending on the initial atmospheric structure. Measurements of these effects show variations in wind stress associated with clouds. Operational and research studies of ice and ocean dynamics will benefit from consideration of cloud effects on wind stress.