Evaluation of parameterizations of the vertical fluxes induced by boundary-layer clouds using ARM observations and high-resolution simulations

Description

Boundary-layer clouds are intimately involved in the redistribution of enthalpy, moisture, and momentum in the lowest layers of the atmosphere and the transport and processing of aerosols. Thus, cloud parameterization must realistically determine the vertical fluxes induced by moist convection associated with clouds. However, not all information of vertical fluxes induced by clouds can be directly measured with the available instrumentation. To provide a comprehensive evaluation of the flux parameterization of clouds, ARM cloud observations must be incorporated with high resolution numerical simulations that explicitly resolve moist convection. In this study, the vertical flux parameterizations of shallow cumuli and stratocumulus clouds commonly used in climate models are evaluated using the case studies selected from ARM observations. We show that the advanced ARM Doppler cloud radars, such as the millimeter-wavelength cloud radar and the W-band ARM cloud radar, and the Doppler lidar provide a unique data set that can be combined with high resolution cloud simulations to provide critical evaluations of the parameterized vertical fluxes, particularly the vertical mass flux in both cloud layer and sub-cloud layer. Issues associated with vertical flux parameterizations of shallow cumuli and stratocumulus clouds are also discussed based on the evaluations performed in this study.