Characteristics and impact of a gale-force storm field over the Norwegian Sea

Abstract

A unique data set was sampled by aircraft, ship, drift buoys and satellites in a strong storm event which occurred over the Norwegian Sea in March 2005 during the LOFZY field experiment. The atmospheric characteristics and the impact on the upper ocean are investigated. The storm field with winds up to 27 m s −1 was situated on the west-side of a low-pressure trough along the Norwegian coast and was marked by a sharp wind front. The entire system of trough, front and storm field was about 200 km wide, had a lifetime of 2 d in the area and advanced at 1–3 m s −1 SE-wards. Temperature contrast across the system was small, but wind contrast was remarkable and concentrated in a step-like front with 5–15 m s −1 difference over a distance of 3 km. The entire system was restricted to the lowest 2 km. It was accompanied by wide-spread rain and snow. Precipitation slightly surpassed evaporation (0.22 mm h −1 ). Surface heat fluxes amounted up to 400 W m −2 . However, they cannot account for the observed sea surface temperature changes between −0.8 and +0.1 K within 6 h during the frontal passage. This is attributed to vertical mixing in the ocean caused by the frontal wind impact and superimposed to pre-existing mesoscale eddy circulations. The mixing acted on a temperature stratification in the uppermost 20–100 m which was opposite on both sides of the Norwegian Current.