Evaluation of the Influence of Saturation Adjustment with Respect to Ice on Meso-scale Model Simulations for the Case of 22 June, 2002

Abstract

A meso-scale model simulation is sometimes conducted with a saturation adjustment scheme with respect to ice in the upper troposphere. In such a simulation, the super-saturation with respect to ice is not permitted in upper tropospheric clouds, which is contradicting with natural situation.In this study, we evaluate the influence of the application of ice-saturation adjustment to upper tropospheric clouds in a meso-scale model. When the ice-saturation adjustment is applied, all of the excess water vapor in upper troposphere is consumed to produce large amount of cloud ice and subsequently snow. Small amount of excess water vapor remain for the depositional growth of snow. Since the fall velocity of snow becomes smaller, the residence time of snow in the atmosphere becomes longer. Consequently, the surface rainfall intensity, on domain-average, becomes slightly smaller through the integration time, compared to the simulation without ice-saturation adjustment.