Strong-wind events and their impact on the near-surface climate at Kohnen Station on the Antarctic Plateau.

Strong-wind events occur 10-20 times per year at Kohnen Station, East Antarctica (75°00'S, 0°04'E, 2892 m above sea level), and are often caused by warm-core cyclones in the north-eastern Weddell Sea. An uncommon event occurred in January 2002, when blocking both in the south Atlantic Ocean and in the south Tasman Sea caused a split-up of the circumpolar vortex, and large amounts of heat and moisture were transported onto the Antarctic Plateau. During strong-wind events over the plateau the near surface temperature can increase by tens of degrees, which is partly caused by the advection of heat, but for an important part by the destruction of the stable temperature-deficit layer by enhanced vertical mixing. The temperature rise is larger during the winter/night than during the summer/day, due to a better developed temperature deficit. Snowdrift during the January 2002 event linearly increased surface roughness for momentum with friction velocity, for values over about 0.18 m s^-1. The cloud cover during the event reduced down-welling solar radiation by 32%, and increased the albedo from about 0.86 to 0.92. Changes in longwave radiation largely cancelled the daytime changes in shortwave radiation, thus net radiation was most affected at night. [ABSTRACT FROM AUTHOR]