Department of Environmental Sciences

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Seminar Abstracts
Environmental Sciences Seminar Abstract            

  Coupling Organic Aerosol Modeling with Laboratory and Field Experiments
Kostas Tsigaridis
NASA Goddard Institute for Space Studies

Comparisons of individual models with organic aerosol (OA) measurements have shown a large underestimate of the OA component by the models. These discrepancies are very high in the free troposphere. Trying to bridge the gap between models and observations, several recent model developments account for secondary OA (SOA), intermediate volatility organics, multiphase chemistry and semi-volatile primary OA (POA). Nevertheless, OA simulations have many degrees of freedom due to the missing knowledge on the behavior and fate of both POA and SOA in the troposphere. Thus, several important assumptions need to be made and are translated to model tuning parameters that vary greatly from one model to the other. At the same time, chamber experiments provide more details concerning the OA formation, increasing the complexity, and potentially the accuracy, of the modeling efforts.

The sensitivity of physical and chemical lumping methods on SOA will be analyzed, together with an efficient way to include as many information as possible in global models, keeping at the same time the SOA calculations accurate and computationally inexpensive. Strong and weak points of chamber experiments will be presented. In addition, first results from the organic aerosol intercomparison AEROCOM exercise will be discussed, which aims to evaluate the actual status of global modeling of the OA occurrence in the global troposphere and analyze discrepancies both between models themselves, as well as between models and observations. It will quantify the uncertainties and attribute them to major contributors. It will also try to identify and analyze potential model systematic biases. The first results of the intercomparison will be presented together with a compilation of field data that will be used for the validation of the models results.

Last updated: 11/13/2009