A model of marine boundary-layer cloudiness for mesoscale applications

Abstract

A one-dimensional version of a multilevel mesoscale model is used to represent the cloud-topped boundary layer (CTBL). Turbulent exchanges are parameterized with a prognostic equation for the turbulent kinetic energy and an improved length-scale formation. Furthermore, the scheme is extended to give a statistical description of the subgrid-scale condensation with a one-and-a-half-order closure. The model results are shown to be in reasonable agreement with both observational data and numerical outputs from the higher-order turbulence model. Finally, it is shown that the partial cloudiness scheme does not only produce more realistic cloudiness and cloud water content than a simple "all or nothing' condensation scheme, but that it also assures model stability by producing a smooth onset of condensation. -from Authors