Sensitivity of Cyclogenesis to Sea Surface Temperature in the Northwestern Atlantic

Abstract

During the Intensive Observation Period 15 (13–15 February 1997) of the FASTEX Experiment, a major cyclone crossed the Atlantic Ocean from the Newfoundland Basin to southern Iceland. Its surface low center deepened by 17 hPa in 7 h when the perturbation crossed the North Atlantic Current (NAC) from cold (3°C) to warm water (15°C). To elucidate the role of sea surface temperature (SST) and air–sea fluxes in the dynamics of oceanic cyclones, three nonhydrostatic mesoscale simulations were performed. The first one is a control experiment with a realistic SST field describing in detail the oceanic front associated with the NAC system. The two following simulations are sensitivity experiments where the SST front is removed: the first one uses a uniformly cold SST equal to 3°C and the second one uses a uniformly warm SST equal to 15°C. The frontogenetic function and the vertical velocity sources in the lower-atmospheric layers of the three simulations were diagnosed. In the control simulation, the surf... Abstract During the Intensive Observation Period 15 (13–15 February 1997) of the FASTEX Experiment, a major cyclone crossed the Atlantic Ocean from the Newfoundland Basin to southern Iceland. Its surface low center deepened by 17 hPa in 7 h when the perturbation crossed the North Atlantic Current (NAC) from cold (3°C) to warm water (15°C). To elucidate the role of sea surface temperature (SST) and air–sea fluxes in the dynamics of oceanic cyclones, three nonhydrostatic mesoscale simulations were performed. The first one is a control experiment with a realistic SST field describing in detail the oceanic front associated with the NAC system. The two following simulations are sensitivity experiments where the SST front is removed: the first one uses a uniformly cold SST equal to 3°C and the second one uses a uniformly warm SST equal to 15°C. The frontogenetic function and the vertical velocity sources in the lower-atmospheric layers of the three simulations were diagnosed. In the control simulation, the surf...