Analysis of a Record‐Breaking Strong Wind Event at Syowa Station in January 2015

Abstract

AbstractSyowa Station in Antarctica observed a January record strong surface wind on 17 January 2015 with a maximum mean wind speed of 41.8 m/s. The strong wind event is studied here using the Weather Research and Forecasting model. The event occurred under the influence of enhanced northerly wind associated with an intense synoptic‐scale depression that approached the west of Syowa station. The northerly wind turned easterly along the coast of the ice sheet with remarkable near‐surface acceleration. The acceleration of the surface wind at Syowa Station was connected with the establishment of the easterly low‐level jet that formed as a result of orographic blocking as follows: (1) Air with low potential temperature around the southern end of the northerly wind was forced to ascend by the slope of the ice sheet; (2) the upwelling transported air from the lower atmosphere, resulting in the establishment of a cold region along the slope; (3) the deformed temperature structure generated a strengthening horizontal pressure gradient; and (4) the negative pressure gradient ∂p/∂y was larger at lower altitudes, resulting in stronger easterly wind in the lower layer, consistent with thermal wind balance. During the strong wind event, katabatic wind was enhanced by the greater katabatic force associated with the stronger negative pressure gradient. Another interesting feature was a local warming at surface level in Lutzow‐Holm Bay. The warming was driven by a foehn mechanism. The other branch of the downslope wind upwelled again above the bay, and this upwelling extended up to the tropopause.