Cold-air outbreaks over the northwest Florida continental shelf: heat flux processes and hydrographic changes.
Huh, O.K., Rouse, L.J. Jr., and Walker, N.D.
An experimental study of the meteorology and oceanography of the cold air outbreak cycle was conducted during the dall of 1978 off Panama City, Florida. Details of the air-sea interaction processes they induce on such upwind continental shelves are poorly known because of lack of appropriate measurements. Shallow depths and proximity to land make the processes significantly different from their deepwater counterparts. The cycle has three phases recognizable in the measurements: the prefrontal, frontal passage, and cold air outbreak/high-pressure phrases. The time variability of oceanic heat fluxes was monitored through the cycle in two ways: by measurements heat content changes and by measuring turbulent and radiative heat fluxes. Advective effects on the heat budget were minimized by the site selection. A mild cold air outbreak stripped 26.8 x 10^6 J m^2 (640 cal cm-2) of heat and 1.1 cm of liquid water from the shelf in 63 hours, and a severe cold air outbreak removed 147.6 x 10^6 J m^2 (3528 cal cm-2) and 4.4 cm of liquid water in 87 hours. For these events, evaporation, sensible heat loss, and radiative heat loss were 51, 16, and 33, and 58, 25 and 17% of the totals, respectively. A simple one-dimensional sallow water heat flux model predicted temperature and heat content changes during severe cold air outbreak to within 8%. Observations indicate the extreme time variability of heat flux processes and the hazards of extrapolating to daily rates from spot measurements or very short time series.