Scales and spectra of turbulence over the gulf stream during offshore cyclogenesis

Turbulence structure of the marine boundary layer (MBL) over the Gulf Stream and the adjacent coastal waters during the development of a storm is discussed. Prestorm conditions prevailed on 9 February and a meso-low formed on 10 February which intensified into an offshore cyclone on 11 February. Observations from aircraft, buoys and ships were made as part of the Genesis of Atlantic Lows Experiment (GALE, 86) during these three days. Analysis of the high frequency (20 Hz) turbulence data collected from low-level flights by the NCAR King Air and Electra indicates the effect of the storm development on the turbulence structure of the MBL.Observational data over the stable region near the coast on 10 February revealed the presence of internal gravity waves. Spectral analysis indicates that the size and energy of the eddies increased over the Gulf Stream and also increased as the storm developed. Results obtained using conditional sampling techniques suggest that intense narrower warm updrafts dominate the total heat flux. The broader, less intense cool downdrafts seem to occupy a large portion of the Gulf Stream.