A Statistical-Dynamical Model for Forecasting Cold Air Stratocumulus over the Yellow Sea.
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH
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Satellite pictures from NOAA-6 are used in satiscally analyzing cloud amounts from November 1981 through February 1982. Cloud amount N, defined as the amount of stratocumulus cloud field within the gridded area, is related to stability and relative humidity in the boundary layer. Stability is given by the boundary layer stability parameter, a quantity based on 850 mb height and temperature and the sea surface temperature. The statistical analysis yields regression equations which are used in a stepwise fashion to predict N. These are combined with a Lagrangian model to complete the statistical-dynamical model. The Lagrangian model simulations the modification of continental polar air to maritime polar air. Predictors for the empirical equations are obtained from the numerical simulation. Key variables, such as the 850 mb temperature and relative humidity, were found to agree well with observations. The sensitivity of the simulation to simplifying assumptions is investigated. The model is sensitive to variations in the range of vertical velocity and entrainment rate.