Understanding Near-Surface and In-Cloud Turbulent Fluxes in the Coastal Stratocumulus-Topped Boundary Layers

Aircraft data collected in Monterey Bay area from forty flights in the framework of Autonomous Ocean Sampling Network (AOSN-II) project were used to study the spatial variability and bulk parameterization of turbulence surface fluxes in a coastal region. Flight maneuvers were used to calibrate the turbulence wind data obtained from a radome probe. The typical flight pattern consisted of dense near sea surface straight legs. A variety of near surface flow patterns with downcoast and upcoast strong or weak flow as well as offshore flow was observed. The wind field was quite complex due to intense topographical effects like flow channeling and thermal flows. In addition, coastal upwelling and stratocumulus cloud contribute significantly in the complexity of the atmospheric flow in the measurements area. Measured surface turbulent fluxes were found to be systematically lower than bulk estimations. Non-homogeneity of the flow, limited validity of surface similarity functions, low level clouds effects and poor roughness length parameterization especially under stable atmospheric conditions in the coastal area are probable reasons for this deviation.
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