Air-Sea Interaction Effects in the Lower Troposphere Across the North Wall of the Gulf Stream

Significant atmospheric and oceanographic differences have often been observed in the regions lying on either side of the north wall of the Gulf Stream. Satellite visible-range sensors have revealed changes in reflectivity across the Gulf Stream believed to be due to changes in sea state that are related to these atmospheric and oceanic differences. In addition, lines of low-level cloud, paralleling the edge of the Gulf Stream, have been observed to persist in satellite imagery for several days at a time. Anomalous radar propagation also has been noted to occur in these same regions. In an attempt to document the interrelation of these phenomena, the lower atmosphere over the north wall of the Gulf Stream was studied on two separate occasions. Sea state photography and measurements of sea surface temperature, air temperature, dew-point temperature and atmospheric pressure were made by an instrumented RP-3A aircraft flying at various altitudes from the Gulf Stream, across the north wall, and onto the Slope Water side. The data collected show significant low level atmospheric and sea state changes on crossing the north wall boundary. These changes appeared to be caused by differences in atmospheric turbulence created by variations in the air-sea temperature differential on each side of the north wall boundary.