The Effect of Horizontal Pressure Gradients on the Momentum Transport in Tropical Convective Lines. Part I: The Results of the Convective Parameterization

Abstract

Measuremenits of the momentum transport in tropical convective lines suggest that horizontal momentum can be generated by the pressure low located near the center of the convective part of the line. A simple convective parameterization is used to evaluate this effect. The parameterization is a version of the Fritsch and Chappell scheme, modified in order to evaluate the influence of the horizontal pressure gradients on momentum transport. The results suggest that in modeling of convective (particularly slow-moving) lines with 20 km resolution, subgrid horizontal pressure gradients should be taken into account. Sensitivity studies show that the magnitude of the calculated momentum flux strongly depends on the average vertical velocity and the vertical velocity in clouds.