Evaluation of midlatitude clouds in a large‐scale high‐resolution simulation using CloudSat observations

The vertical representation, cloud radiative effects (CREs) and radiative heating rates of midlatitude clouds in a large‐scale cloud‐resolving model simulation were examined using CloudSat observations. Cloud Profiling Radar (CPR) reflectivity profiles were generated from model output and compared objectively to observed CPR profiles by applying cluster analysis to joint histograms of height and reflectivity (H‐dBZ). Results of the analysis identified four distinct cloud regimes for both the simulation and observations. Simulated patterns of H‐dBZ joint histograms correlated well with observations for all four cloud regimes, i.e., (1) cirrus and low‐level cloud, (2) thick cirrus, (3) midlevel convection, and (4) frontal precipitation. The simulation also reproduced well the relative frequency of occurrence of all cloud regimes and their latitudinal dependence. Using a CloudSat radiative flux‐heating rate simulator, net CREs at the top of atmosphere, bottom of atmosphere, and for the atmosphere as a whole were found to be in relatively good agreement with observations for cloud regime 1, which occurred over 60% of the time, but were significantly biased for other regimes. While both simulation and observations showed a net column radiative cooling for all cloud regimes, the simulated heating rates indicated much less variation with height. These differences were attributed mainly to errors in the simulated water content profiles and to a lesser extent possible deficiencies in certain ice conversion processes occurring within the model for frontal cloud systems.