The Numerical Forecast And Evaluation For Heavy Air Pollution In Beijing-Tianjin-Hebei

The regional air quality far from standard in our country, heavy air pollution incidents frequently occurred, especially in Beijing-Tianjin-Hebei area is particularly serious. Therefore, there is an urgent need for air pollution business forecasts. Numerical prediction is an effective way to obtain the future air quality. It can analyze the evolution characteristics of the pollution process, the source and destination of the pollutants, and simulate the effect of emergency control.China National Environmental Monitoring Centre cooperate with The Institute of Atmospheric Physics established a test system for the regional 6 pollutants and AQI forecasting, focus on heavy pollution process in Beijing-Tianjin-Hebei area. For heavy pollution, we mainly focus on the starting time, the duration, and the spatial extent of the pollution. Therefore, an evaluation method on the forecasting ability of heavy pollution in Beijing-Tianjin-Hebei area was established with using regional air quality inspection data, numerical air quality model forecast product and weather chart data. The forecasting ability of the Nested Air Quality Prediction Modeling System （NAQPMS） on stagnant, sand dust and special pollution was evaluated applying this method. In order to improve the accuracy of forecast, possible causes of meteorological conditions on the advanced forecasting, lag forecasting and missing forecasting were investigated. Results showed that prediction accuracy of three days ahead forecasting of heavy pollution can reach 57%.Forecasting ability in autumn and winter was better than in other seasons. Forecasting ability in stagnant weather was better than that in sand-dust and special conditions. The statistical analysis on AQI forecast results showed that the occurrence possibility of actual heavy pollution increased when the predicted AQI exceeded 150. If 150 were defined as the critical predicted AQI value for heavy pollution warning, the prediction accuracy can be enhanced above 70%. Weather system has an important influence on the process of heavy pollution weather forecast. The forecast deviation of the position and intensity of weather system by WRF is an important reason for the advanced and lag forecasting of stagnant pollution.The 2022 Winter Olympic Games will be held in Beijing, the air quality then will to reach the national standard requirement and the world health organization guide values. Using the latest decade data of ambient air quality of the same period of Winter Olympic Games to analyses the air quality trend* The results showed that: There are different degrees of PM_2.5 excessive phenomenon at the same time of the Winter Olympics form 2006-2015, among them, the most serious pollution is in 2014,2015 is relatively better,and february 13th-16th is easy appear heavy air pollution. We using the developed method to evaluate the simulation ability of the heavy pollution during 2006-2015 february, and to assess the risk of pollution in 2022.On this basis, we designed emission reduction experiments to ensure that there will be no heavy pollution during the Winter Olympic Games. In this paper, we describe from two aspects of meteorology and emission sources to explain the main reasons for the change of pollutant concentration at the same period of the Winter Olympics in different years. The concentration levels and simulation results compared between the two groups in february 2014 and february 2015 showed that: （l）The emission reduction scheme makes the PM_2.5 concentration during the games under 130ug/m3,except 13th-16th, other date air quality is excellent. （2）Compared to the same time of games of 2014 and 2015, meteorological caused beijing and zhangjiakou PM_2.5 concentration increased 40%-60%, SO₂ and NO₂ concentration increased 0-40%. （3） Emission reduction makes PM_2.5, SO₂ and NO₂ concentrations decreased by more than 60%in 2014, and makes PM_2.5 concentration decreased between 40%-60%.