Comparison between Two Anvil Cirrus Parameterizations using a 1-D Cloud Model.

摘要

Features and characteristics of a revised cirrus parameterization, tested for simulating anvils at the top of the deep convection, are investigated. The scheme assumes that the precipitation rate is related to the updraft velocity, retrieved from the convection scheme. A specific crystal number density and the mass and fall velocity of an average ice crystal represent the ice crystal size spectrum. In this way, a direct connection between dynamical features of the convection and the microphysical features characteristic of anvil ice is established. The scheme is tested using 1-D convective model and the simulated ice water contents are compared to those retrieved using an earlier (reference) cirrus scheme and the observational data typical of cold anvils. Furthermore, the ice water content is treated as a prognostic variable in the revised scheme, while in the reference scheme the appropriate ice water content is diagnosed based on the assumption of a relaxed quasi-steady state in which the forecasted convergence of vapor is balanced by its deposition to ice.