Evaluation of Regime-sorted Cloud Properties in Six SCMs against the ARM Observations at the SGP Site

Description

This study evaluates the overall performances of six single-column models (SCMs) by comparing the simulated cloud fraction, cloud liquid and ice water content, and cloud radiative forcings with observations at the ARM SGP site from 01 January 1999 to 31 December 2001. The evaluation focuses on the model performance at different dynamical regimes classified by 500-hPa large-scale vertical pressure velocity. Results show that large model biases exist under strong updraft regimes: most SCMs overestimate the high-level clouds and underestimate the low-level clouds in most SCMs, which however are related to different combinations of their biases in frequency and mean cloud amount of cloudy events. Further analyses reveal distinct compensations at different levels between models’ biases in cloud fraction and cloud water content, which can be linked to deficiencies in the parameterizations of convective and stratiform clouds. Finally, the model biases in cloud fraction are shown to be the dominant contributor to the biases in the cloud radiative forcings (especially longwave) at TOA and the surface.