Effects of model resolution on entrainment (inversion heights), cloud-radiation interactions, and cloud radiative forcing

摘要

We undertook three-dimensional numerical studies of a marine stratus deckunder a strong inversion using an interactive shortwave- andlongwave-radiation module. A suite of sensitivity tests were conducted toaddress the effects of model resolution on entrainment (inversion heights),cloud-radiation interactions, and cloud radiative-forcings by varying modelhorizontal resolution only, varying vertical resolution only, and varyinghorizontal- and vertical-resolution simultaneously but with a fixed aspectratio of 2.5.Our results showed that entrainment (inversion height) is more sensitive tovertical- than to horizontal-resolution. A vertical resolution finer than40 m can simulate spatial- and temporal-variations in the inversion heightwell. The inversion height decreases with increasing vertical resolution, buttends to increase with increasing horizontal resolution. Cloud liquid waterpath doubles after refining both the vertical- and horizontal-resolution by afactor of four. This doubling is associated with a positive feedback betweencloud water and cloud top radiative cooling, which amplifies smalldifferences initiated by changes in the model resolution. The magnitude ofthe cloud radiative-forcing tends to increase with increasing modelresolution, mainly attributable to the increase in the cloud liquid waterpath. Shortwave radiative forcing is dominant, and more sensitive to modelresolution than the longwave counterpart.