Coastal Winds in South Florida

Abstract

Thirteen-month records for the period of April 1994?April 1995 from eight (out of nine) Coastal-Marine Automatic Network (C-MAN) stations in south Florida are analyzed statistically to study alongshore variability of observed atmospheric variables. The surface variables largely are statistically homogeneous and coherent along the Straits of Florida. The maximum correlation for hourly wind components between adjacent stations (separated alongshore by 30?117 km) ranges from 0.9 to 0.75, respectively. However, there is a lack of coverage in the cross-shore direction; hence, a redistribution of C-MAN stations in the cross-shore direction should be considered to provide better spatial coverage of surface atmospheric variables in the south Florida region. Surface winds from the National Centers for Environmental Prediction (NCEP) 80-km grid, ? (Eta) Model analysis for the same period are compared statistically with observations from an air?sea interaction buoy and a C-MAN station in the south Florida coastal region. The ? winds represent the low-frequency winds (periods between 3 days and 3 weeks) fairly well (e.g., the coherence exceeds 0.8 and the phase difference is less than 15°) but generally are weaker in magnitude than are the observed winds. The difference can be up to 2 m s?1 for the monthly mean and 1 m s?1 for the seasonal mean. The histogram of the ? winds in winter has a single large peak instead of multiple peaks as occur in those of the observed winds. Southward bias in the ? winds exists in summer. The ? Model simulates well the flow patterns of a tropical cyclone and an extratropical cyclone on the regional scale but lacks local spatial variability. As demonstrated, local spatial variability can be represented better by a blend of model and observed winds than by either the model-based or observed local surface winds alone. These issues need to be reexamined periodically with upgraded versions of NCEP?s operational models.