14th Joint Conference on the Applications of Air Pollution Meteorology with the Air and Waste Management Assoc


Evaluation of modeled cloud properties for air quality applications

Junhua Zhang, MSC, Downsview, ON, Canada; and W. Gong

Clouds play an important role in processing and cycling atmospheric pollutants. Some of the physical and chemical processes involved include aerosol activation, aqueous-phase chemistry, and wet deposition. It is therefore important to represent these cloud processes when modelling the transport and transformation of atmospheric chemical tracers, particularly aerosols. A Canadian air quality model AURAMS (A Unified Regional Air-quality Modelling System) is driven "off-line" by the Canadian operational meteorological forecast model GEM (Global Environmental Multiscale model). A number of cloud microphysical parameters predicted by GEM are used in AURAMS' cloud processing of gases and aerosols. A previous AURAMS evaluation has shown that the ability of the meteorological model to predict cloud microphysics fields is critical to the modelling of tracer processing by clouds. In this study, temperature, dew point depression and cloud properties (cloud cover, cloud water content) predicted by GEM are evaluated against radiosonde, satellite and in-situ aircraft observations during an aircraft study of Chemical transport and Transformation by Cloud (CTC) conducted as part of the ICARTT (International Consortium for Atmospheric Research on Transport and Transformation) 2004 campaign. Different model resolutions and microphysical parameterizations are examined. Evaluation includes direct model-observation comparison and comparisons in terms of spatial variation and probability distribution of modeled vs. observed cloud water content. Uncertainty of air quality simulation caused by the uncertainty of cloud properties will also be briefly discussed in this presentation.

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Session 4, Emission and Air Quality Measurements and Model Evaluations
Tuesday, 31 January 2006, 1:45 PM-4:30 PM, A407

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