CAPPS模型在武汉市空气质量预报中的应用与检验

利用天气学和数理统计方法，基于2013—2017年（100°—120°E，25°—45°N）范围内405个环境空气质量评价点数据、武汉市空气质量实时监测数据以及相应时段常规气象观测资料，对武汉重污染天气过程触发机制及主要影响因素进行了分析，结果表明：（1）武汉市2013—2017年空气质量重污染过程发生频率和过程平均持续时长均呈明显下降趋势。（2）引发武汉市空气质量重污染过程的天气形势在海平面气压场表现为冷空气入侵、静稳天气两种类型，形成机制分别为风力加大导致风向上游空气质量指数AQI大值区污染物输送和扩散条件较差导致本地污染物堆积。（3）典型的武汉城区重污染过程形成的天气模型为：过程开始时静稳天气下本地污染物堆积；冷空气南下时风力加大导致外源污染物输入；冷锋过境后内外源污染物叠加；冷空气影响过后扩散条件转好，过程结束。
（4）空气质量实时变化与气压、风、温度、相对湿度等气象要素有密切的关系。在不同的天气形势下，应以气压的实时变化为基础，结合其它气象要素的特征，分析制作AQI精细化变化趋势预报。

Urban air quality in a mid-size city-PM2.5 composition,sources and identification of impact areas: From local to long range contributions

Based on data at 405 ambient air quality assessment sites, air quality data and conventionally-observed meteorological data in Wuhan city during 100°-120°E, 25°-45°N from 2013 to 2017, the trigger mechanism and main factors of urban heavy pollution processes in Wuhan are analyzed by weather and mathematical statistics methods. The result shows that:(1) The frequency and the average duration of the process of air quality heavy pollution in Wuhan are obviously decreasing. (2) The weather situation that causes the heavy pollution of air quality in Wuhan city is cold air invasion and statically stable weather. The formation mechanism is caused by the increase of wind speed, which leads to the transport of pollutants in the upper AQI area of the upstream of the wind direction, and the poor diffusion conditions lead to the accumulation of local pollutants.
(3) The typical weather model for the heavy pollution process in Wuhan city is:The accumulation of local pollutants at the beginning of the process, the increase of wind speed leading to the input of exogenous pollutants, and superposition of internal and external pollutants after cold front transit. The condition improves due to diffusion and the process is then over. (4) The relationship between air quality and meteorological elements, such as atmospheric pressure, wind, temperature, is often characterized differently depending on weather conditions. Under different weather conditions, the trend of AQI should be analyzed based on real-time variation of air pressure and the characteristics of temperature and wind.