Simulation And Evaluation Of Haze Dasy In Jiangsu Province Based On WRF/CMAQ Model

To our knowledge, haze is traditionally an atmospheric phenomenon where dust,smoke and other dry particles obscure the clarity of the sky, let visibility recduced to 10km below. Studies have indicated that haze weather are significantly relatced to climate background, local weather conditions, pollutant concentrations and its composition distribution.This paper evaluates the accuracy of the WRF / CMAQ numerical model for the 18-month haze simulation of Jiangsu Province from October 2014 to March 2016,and explores the possible causes of inaccuracies in haze forecast. The simulation results are compared with the observation data of meteorological factors such as visibility, relative humidity and wind speed in 72 meteorological stations in theprovince, and compared with the real-time PM_2.5 data of 64 provincial control monitoring sites issued by the Ministry of Environmental Protection. The temporal and spatial changes and seasonal variation characteristics of visibility, relative humidity, wind speed and PM_2.5 in Jiangsu Province were revealed, and the meteorological factors and pollutant simulation were analyzed.The research shows that: ?1? The WRF/CMAQ simulation showed coincidence with observation in relative humidity and PM_2.5. The average error is 2-5km between atmospheric visibility simulation values and observation values. In coastal and offshore cities, the simulated visibility is much greater than the observed, and root mean square error exceeds 10km. ?2? With aerosol extinction coefficient obtained from IMPROVE program, visibility that calculated from parameterization scheme A is much larger than the observed value when the visibility of the visibility is much larger than 10 km. Given the effects of N02 absorbance, visibility calculated from parameterization scheme B had a lower relative error compared to scheme A. ?3?Simulated haze days is far less than observed and the difference is within 60 days in Jiangsu area. The largest error of visibility can reach 10km and mostly happened in eastern coastal cities like Yancheng and Lianyungang which existed high simulated peaks. Simulated haze days in those cities are much less than observed days with an error of 30-60 days. ?4? Preliminary discussions on possible causes of differences between observed and simulated atmospheric visibility are described in this paper.Relative humidity plays a crucial role in visibility prediction. Low proportions of EC and OC, underestimated water-soluble ions, underestimated relative humidity, large wind speed and so on caused low simulated values of aerosol extinction coefficient in some regions.