Variation of the Wind Stress Related to Frontal Passages during FASINEX (Frontal Air-Sea Interaction Experiment) 1986

摘要

The variations of wind stress on the ocean surface during the passages of atmospheric cold fronts are investigated using data collected during the 1986 Frontal Air-Sea Interaction Experiment (FASINEX). Six frontal passages were observed from two ships (R/V's Oceanus and Endeavor) in the western North Atlantic during the period 14 February-6 March 1986. Wind stresses are calculated by both the dissipation method, using velocity variances measured with hot-film anemometers, and the bulk method, using mean wind, temperature, and humidity and a drag coefficient. The ratio of dissipation to bulk stress is found to be enhanced by factor of up to 1.4 within approximately 200 km of a frontal zone when averaged over six frontal passages. The enhancement during individual frontal passages was as high as 3.6, with the major peaks occurring from 300 km ahead of the front to 400 km behind the front. Investigation of the differences in direction between surface wind and sea swell suggests that the enhancement is produced in large part through a combination of two factors: modulation of high-frequency wind waves by underlying swell and chaotic seas resulting from radiation of swell waves generated in the cold sector through the front.