Construction of a chemistry-weather assimilation system coupled with CMA-MESO and preliminary experiments assimilating aerosol observations

The CMA-CUACE-Haze atmospheric chemistry model developed in China is an important tool for aerosol process simulation and assessment, yet there is a lack of atmospheric chemistry variable analysis system. In this paper, an assimilation system for regional chemical weather coupling based on the CMA-MESO three-dimensional variational analysis is developed, which takes uncorrelated PM_2.5 and PM_2.5-10 variables as control variables and utilizes the modeled background error covariance to achieve assimilation analysis of aerosol observations of PM_2.5 and PM₁₀. The validity of the design of the coupled assimilation system is verified by aerosol single-station ideal tests, and assimilation experiment of aerosol PM_2.5 and PM₁₀ observations has been conducted for the heavy pollution process in December 2016. The analysis results indicate that the coupled atmospheric chemistry-weather assimilation system can perform simultaneous miniaturization analysis of aerosol observations and weather variable observations, and the analysis fields between atmospheric chemistry variables and weather variables do not affect each other. The assimilation of aerosol observations reasonably corrects the atmospheric chemical background field, and the analytical fields of PM_2.5 and PM₁₀ variables are closer to the observations. Aerosol assimilation has a significant effect on pollutant forecasts and the effect can last up to 72 h. The regional coupled chemistry-weather assimilation system developed in this study can provide more accurate chemical initial fields for the CMA-CUACE-Haze model.