Validity of similarity relations over the Gulf Stream

Observations obtained from aircraft, buoys, ships and vertical soundings made on 9, 10 and 22 February, 1986 during the Genesis of Atlantic Lows Experiment (GALE) are used to study the mean marine boundary-layer (MBL) structure over the cold coastal waters and the warm Gulf Stream. Different synoptic conditions prevailed on each day. The synoptic setting was characterized by prestorm conditions on 9 February and meso-low development on 10 and again on 22 February. Two convergence zones, one near the Gulf Stream and the other close to the coast were observed on both the days of cyclogenesis causing different stability conditions in the MBL near the coast and the Gulf Stream. The boundary-layer on 9 February was however well mixed. Temperature and humidity variances during prestorm conditions (9 February) generally followed the free convection relations. But on 10 and 22 February, in the presence of a meso-low, similarity relations do not appear to be valid for temperature and humidity variances and fluxes.