Joint Seminar: Evaluation of 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 cloud-resolving Weather Research & Forecasting (WRF) 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). The analysis produced four distinct cloud regimes in both the simulation and observations. In all cases, the simulated patterns of H-dBZ joint histograms were significantly correlated with the observations. The simulation also reproduced well the relative frequency of occurrence and latitudinal dependence of the cloud regimes. 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 somewhat good agreement with observations for cirrus and low-level clouds, which occurred about 60% of the time. However, significant biases in these fluxes were found for other cloud regimes. While both simulation and observations showed a net column radiative cooling in all cases, 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.

Datum

12.10.2010

Uhrzeit

15:15 Uhr

Ort

Bundesstr. 53, room 022/023
Seminar Room 022/023, Ground Floor, Bundesstrasse 53, 20146 Hamburg, Hamburg

ReferentIn

Tom Greenwald, Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin, USA

Chair


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