AIR-SEA INTERACTION DURING AN EXTREME COLD AIR OUTBREAK FROM THE EASTERN COAST OF THE UNITED-STATES

We report on an aircraft investigation of boundary layer mean and turbulent structure and evaluate the Lagrangian budgets of temperature and moisture in the subcloud layer following a streamline during an extreme cold air outbreak. The maximum sea-air temperautre difference was 23 K. A stratocumulus overcast was found from about 60 km offshore to the Gulf Stream core with cloud top rising downstream. East of the Gulf Stream cumulus congestus and snow showers were observed. Lagrangian budgets showed most warming, and moistening of the layer between 70 m and about 100 m below mean cloud base was due to turbulent flux divergence. At 70 m a maximum total heat flux of 1174 W m-2(364 W m-2 sensible, 799 W m-2 latent) was observed over the Gulf Stream core. We estimated that cold, dry continental air can be transformed to air which can participate in deep convection in about 20-30 hours. -from Authors