V. S. Bouchet

Cloud Processing of Gases and Aerosols in a Regional Air Quality Model (AURAMS): Evaluation Against Aircraft Data

Clouds play an active role in the processing and cycling of chemicals in the atmosphere. Gases and aerosols can enter cloud droplets through absorption/condensation (of soluble gases) and activation and impact scavenging (of aerosol particles). Once inside the cloud droplets these tracers can dissolve, dissociate, and undergo chemical reactions. It is believed that aqueous phase chemistry in cloud is the largest contributor to sulphate aerosol production. Some of the aqueousphase tracers will be removed from the atmosphere when precipitation forms and reaches the ground. However, the majority of clouds are non-precipitating, and upon cloud dissipation and evaporation, the tracers, physically and chemically altered, will be released back to the atmosphere. Updrafts and downdrafts in convective clouds are also efficient ways of redistributing atmospheric tracers in the vertical. It is therefore important to represent these cloud-related physical and chemical processes when modelling the transport and transformation of atmospheric chemical tracers, particularly aerosols. A new multiple-pollutant (unified) regional air-quality modelling system, AURAMS, with sizeand chemical-composition-resolved aerosols is being developed at the Meteorological Service of Canada. In the current version of AURAMS, many of the cloud processes mentioned above are represented. Evaluation of the model performance is underway for several selected periods (e.g., Makar et al., 2004a,b; Bouchet et al., 2004). In this paper we will focus on a comparison against aircraft measurements conducted during the EMEFS-1 campaign in the summer of

Wintertime and Summertime Evaluation of the Regional Pm Air Quality Model Aurams

Three dimensional air quality models have established themselves as valuable tools for the development of emission control strategies. They give scientists the ability to investigate the consequences of multiple emission reduction scenarios as well as research optimum sets of pollutant and/or precursor emission reductions under various meteorological conditions. This capability is becoming crucial as advances in atmospheric science in the past decades have revealed numerous links between ground-level air pollution problems such as ozone, acid rain and particulate matter (PM) (Hidy et al., 1998). With the recognition of PM, especially, as a severe human health concern (Samet et al., 2000; Brook et al., 2002), efforts have lately focused on addressing this new issue without compromising any achievement in reducing ozone and acid rain. As demonstrated by (1997), decreasing VOCs, which are ozone precursors, could free nitrogen oxides and results, under certain conditions, in an increase in PM mass. The so-called ‘one atmosphere’ models are therefore desirable to study PM issues.