Knowledge gaps in organic aerosol global modeling

Abstract:

Intense research on organic aerosols (OA) in the last years resulted in an increased understanding of their presence in the atmosphere, and guided the development of new OA parameterizations for use in models of all scales. These include both new parameterizations (e.g. volatility basis set) and new formation pathways (e.g. multiphase chemistry, sea spray organic enrichment, primary biological particles, brown carbon). The implementation of such parameterizations in global models follows the research priorities set by the various modeling groups. In addition, the models don’t always track the OA formed due to the new parameterizations, making a robust comparison of OA simulations among models extremely challenging.

This study presents in detail the most important inconsistencies that present-day OA models have, and suggests priorities in the implementation of new parameterizations and sources of OA in global models. New parameterizations that need immediate attention will be presented. These include the OA/OC ratio, which depends on OA sources and atmospheric processing and is important for a proper model evaluation against OA and OC observations, and the semi-volatility of OA, both primary and secondary. Multi-model comparisons against measurements will also be presented to demonstrate the need for convergence between models, and highlight the important role of the new processes in the OA global budget.