Abstract
Abstract. Horizontal grid resolution has a profound effect on model performances on meteorology and air quality simulations. In contribution to MICS-Asia Phase III, one of whose goals was to identify and reduce model uncertainty in air quality prediction, this study examined the impact of grid resolution on meteorology and air quality simulation over East Asia, focusing on the North China Plain (NCP) region. The NASA Unified Weather Research and Forecasting (NU-WRF) model has been applied with the horizontal resolutions at 45, 15, and 5 km. The results revealed that, in comparison with ground observations, no single resolution can yield the best model performance for all variables across all stations. From a regional average perspective (i.e., across all monitoring sites), air temperature modeling was not sensitive to the grid resolution but wind and precipitation simulation showed the opposite. NU-WRF with the 5 km grid simulated the wind speed best, while the 45 km grid yielded the most realistic precipitation as compared to the site observations. For air quality simulations, finer resolution generally led to better comparisons with observations for O3, CO, NOx, and PM2.5. However, the improvement of model performance on air quality was not linear with the resolution increase. The accuracy of modeled surface O3 of the 15 km grid was greatly improved over the one from the 45 km grid. A further increase in grid resolution to 5 km, however, showed diminished impact on model performance improvement on O3 prediction. In addition, a 5 km resolution grid showed large advantage in better capturing the frequency of high-pollution occurrences. This was important for the assessment of noncompliance with ambient air quality standards, which was key to air quality planning and management. Balancing the modeling accuracy and resource limitation, a 15 km grid resolution was suggested for future MICS-Asia air quality modeling activity if the research region remained unchanged. This investigation also found a large overestimate of ground-level O3 and an underestimate of surface NOx and CO, likely due to missing emissions of NOx and CO.
Highlights
Air pollution is a threat to human health and climate and detrimental to ecosystems (Anenberg et al, 2010; https://www.who.int/airpollution/ambient/en/, last access: 24 February 2020). Lelieveld et al (2015) estimated that over 3 million premature deaths could be attributable to outdoor air pollution worldwide in 2010 based on their analysis of data and the results from a high-resolution global air quality model
Contributing to MICS-Asia Phase III, whose goals included identifying and reducing air quality modeling uncertainty over the region, this investigation examined the impact of model grid resolutions on the performances of meteorology and air quality simulation
The modeling results were compared to the observations of surface meteorology archived by China Meteorological Administration (CMA) and of ground-level air quality collected via Chinese Ecosystem Research Network (CERN)
Summary
Air pollution is a threat to human health and climate and detrimental to ecosystems (Anenberg et al, 2010; https://www.who.int/airpollution/ambient/en/, last access: 24 February 2020). Lelieveld et al (2015) estimated that over 3 million premature deaths could be attributable to outdoor air pollution worldwide in 2010 based on their analysis of data and the results from a high-resolution global air quality model. Lee et al (2018) examined the importance of aerosol–cloud–radiation interactions to precipitation and the model resolution impact of key meteorological processes that affected precipitation using the Advanced Research WRF model They found that the coarse model resolution would lower updraft, alter cloud properties (e.g., mass, condensation, evaporation, and deposition), and reduce cloud sensitivity to ambient aerosol changes. The investigation would assist in gaining insights into how model horizontal resolution affects simulated meteorology and air quality and contribute to the formulation of uncertainties resulting from model resolutions for the MICS-Asia community. The latter would especially be valuable since most MICS-Asia Phase III model simulations were. Tao et al.: Evaluation of NU-WRF performance on air quality simulation under various model resolutions 2321 conducted at a specific horizontal resolution (i.e., 45 km for most participants)
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