Wintertime Arctic Air Pollution over Alaska

• Main Authors: Ioannidis, Eleftherios, Law, Kathy S., Raut, Jean-Christophe, Onishi, Tatsuo, Simpson, William, R., Kirpes, Rachel, M., Pratt, Kerri, A.
• Other Authors: TROPO - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Department of Chemistry and Biochemistry Fairbanks, University of Alaska Fairbanks (UAF), Department of Chemistry Ann Arbor, University of Michigan Ann Arbor, University of Michigan System-University of Michigan System, Department of Earth and Environmental Sciences Ann Arbor
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2020
• Subjects: [SDE]Environmental Sciences; Barrow; black carbon; Alaska
• Online Access: https://insu.hal.science/insu-04436738; https://doi.org/10.5194/egusphere-egu2020-7849

International audience The Arctic is influenced by long-range transport of aerosols, for example, sulphate, black carbon, and dust from mid-latitude emissions, especially in winter and spring, leading to the formation of Arctic Haze with enhanced aerosol concentrations. However, more recently, local sources of aerosols, such as wood-burning or resource extraction, are highlighted as already being important, but many uncertainties about sources and aerosol processes still remain. For example, the formation of secondary aerosols, such as sulphate, in winter despite very low temperatures and the absence of sunlight. In this study, which contributes to the international PACES-ALPACA initiative, the Weather Research Forecasting (WRF) and WRF-Chem models are used to investigate wintertime pollution over Alaska with a focus on regions influenced by local pollution, such as Fairbanks and by Arctic Haze, such as Utqiagvik (formerly known as Barrow). Fairbanks is the most polluted city in the United States during wintertime due to high emissions and the occurrence of strong surface temperature inversions. As a first step, background aerosols originating from remote sources were evaluated in large- scale quasi-hemispheric WRF-Chem runs using ECLIPSE anthropogenic emissions. The model performs quite well over Alaska at background sites (e.g. Denali Park) compared to observations from the US Environmental Protection Agency (EPA). Discrepancies in modelled aerosols due to formation mechanisms and aerosol acidity are being investigated. Secondly, in order to better simulate Arctic aerosols and local pollution episodes, different schemes in WRF were tested over Alaska with a particular focus on improving simulations of the Arctic boundary layer structure and, in particular, wintertime temperature inversions which trap pollution at the ground. In order to simulate these extreme/cold meteorological conditions, different schemes linked to boundary layer physics, surface layer dynamics and the land surface have been tested and ...