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Diagnostic Analysis of CMAQ Dry Deposition Fields in the Context of AQMEII4
Citation:
Hogrefe, C., J. Bash, Jon Pleim, D. Schwede, R. Gilliam, K. Foley, Keith Wyat Appel, AND R. Mathur. Diagnostic Analysis of CMAQ Dry Deposition Fields in the Context of AQMEII4. 38th International Technical Meeting on Air Pollution Modelling and its Application, Barcelona, Virtual, SPAIN, October 18 - 22, 2021.
Impact/Purpose:
This abstract describes the analysis of CMAQ simulations performed by AESMD to contribute to the fourth phase of the Air Quality Model Evaluation International Initiative (AQMEII). The focus of the analysis is on investigating the impacts of differences in the representation of the underlying land use and the scientific formulation of the dry deposition process on simulated deposition fluxes and concentrations.
Description:
Phase 4 of the Air Quality Model Evaluation International Initiative (AQMEII) is focused on the diagnostic intercomparison and evaluation of deposition simulated by regional-scale air quality modeling systems and employs both grid and box modeling techniques to accomplish this goal. This study presents an analysis of CMAQv5.3.1 simulations for the years 2010 and 2016 that were performed in the context of AQMEII4 over a North American modeling domain. The simulations used the two dry deposition schemes (M3DRY and STAGE) available in CMAQ. Meteorological fields were prepared with WRFv4.1.1 using the MODIS land-use classification scheme. Sensitivity simulations for 2016 were configured to use WRFv4.1.1 with the NLCD40 land-use classification scheme and satellite-derived leaf area index (LAI) and vegetation fractions. Results show that variability in the estimated dry deposition sink affected model performance and resulted from both differences in model process formulation (M3DRY vs. STAGE) and the representation of the underlying land use (MODIS vs. NLCD40). The STAGE dry deposition scheme resulted in generally higher ozone during the summer and lower ozone during the winter than M3DRY. Using WRF fields with MODIS land use information yielded consistently lower ozone than the NLCD40 setup while the effect was less pronounced for other species. To gain mechanistic insights into model behavior, the study also employed additional diagnostic variables defined for the AQMEII4 project., i.e. grid-scale and land-use specific effective conductances for the major dry deposition pathways (stomatal, cuticular, and vegetated and bare soil) as well as component resistances. Analysis of these variables indicated that there generally was a greater contribution to ozone dry deposition from the stomatal and cuticular pathways in M3DRY compared to STAGE, resulting in a stronger ozone sink over forested and agricultural regions during summer. These results will be discussed in the context of ongoing AQMEII4 grid and box modeling analyses.
