Geostrophic Drag and the Cross-Isobar Angle of the Surface Wind in a Baroclinic Convective Boundary Layer over the Ocean

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Abstract
Wind fields in the baroclinic, unstably stratified planetary boundary layer above the ocean have been analysed for the data of the AMTEX experiments executed during winter in the East China Sea. For the so-called cold air advection, the angle between winds and isobars increases as the height decreases at the lower half of the planetary boundary layer, while at the upper half layer the angles have negative values. The typical angles in the lower and upper layers are 20-50 deg. and -10- -40deg., respectively, when the horizontal temperature gradient is about 1.5°C per 100km. An empiric formula for the Rossby-number similarity theory is obtained, of which form is a modification of the AryaWyngaard's theoretical expression for the baroclinic, convective boundary layer model. The present result with respect to the baroclinicity dependence of the numerical constants of Rossbynumber similarity theory is slightly different from the empirical result derived from the Wangara data by Clarke and Hess.