A PLAM Index Forecast Method for Air Quality of Beijing in Summer

For a regional air pollution event in a synoptic scale, such as typical stabilized summer weather over North China, a key scientific issue is to identify the possible impacts of pollutants on mega-cities like Beijing and on the zones between the cities and their adjacent areas, from emissions by human activities, e.g., industrial and agricultural emissions as well as traffic exhaustions in the so-called capital economic belt, covering Beijing, Tianjin and a number of surrounding provinces, including Hebei and Shanxi provinces. For this special target as well as the assignment of the air quality predicting service in 2008 Beijing Olympic Games, a parameterized method is developed to predict the air quality in Beijing and its surrounding areas in summer.On the basis of the relationship between summer daily PM₁₀ in Beijing Observatory and key meteorological data for July to September during 2000-2007, analyzing the sensitive meteorological parameters which are relevant closely with high concentration of PM₁₀, an index method of PLAM (parameter linking air-quality and meteorology) is given, which is derived to forecast the stabilized weather conditions of North China for 2008 Beijing Olympic Games. For different PLAM value there is a weight given according to the wind direction of the site pointing what extent to Beijing, as well as its wind speed. So the PLAM index can also predict quantitatively the weather conditions in surrounding areas of Beijing, showing whether or not the meteorological conditions in these areas are favorable for pollutants transport to Beijing. It is found that the poor air quality days with elevated PM₁₀( > 150μg/m³) in summer are associated with higher PLAM values, featuring high temperature, high humidity, lower wind velocity and higher stability.A satisfying result of PLAM index forecast timely for the 2008 Beijing Olympic Games is achieved.PLAM parameter forecast method provided valuable 48 hours services with an interval of 12 hours for the day of opening ceremony and 24-72 hours prediction of air-quality for subsequent events during the whole Beijing Olympic Games. It is also found that the good air qualities are associated with the traffic control measures taken by the municipal government in reducing the vehicle exhaustions during Beijing Olympic Games.The forecast verifying results of PLAM index are highly correlated with daily real time PM₁₀ data collected by Beijing Weather Observatory, indicating that the PLAM index has a remarkable effect.