A Simple Parameterization Scheme for Subtropical Marine Stratocumulus

Abstract

A simple scheme to represent the marine stratocumulus clouds off the west coast of continents is implemented in the Global Spectral Model (GSM) at Japan Meteorological Agency (JMA). The parameterization is based on diagnostic cloud schemes where cloud fraction is diagnosed mainly as a function of inversion strength considering other parameters. The global distribution of marine stratocumulus clouds off the west coast of continents is improved remarkably with this new scheme. Low-level cloud amount shows reasonable agreement with the International Satellite Cloud Climatology (ISCCP). With the improved cloud amount, the radiation fields are also improved in comparison with the Earth Radiation Budget Experiment (ERBE). Seasonal and diurnal variations of marine stratocumulus cloud amount off the west coast of continents also show reasonable agreement with surface-based cloud amount data from Klein and Hartmann (1993) and other observations.