2015年冬季湖北省PM2.5重污染传输特征及影响天气系统的数值模拟

为了研究湖北省两种污染来源的重污染天气特征及其形成机制，采用WRF/Chem零排放情景模拟方案，将2015年冬季湖北省PM2.5模拟浓度分离为外源传输量和本地累积量，基于对数值模拟结果的统计分析，确定了湖北省污染传输通道和外源传输贡献率，研究了敏感区天气系统对两种污染来源的影响作用。结果表明，外源污染物输送在湖北省内有两条主要通道，一是由南襄盆地夹道直接输送汇入江汉平原，二是沿京广线从信阳到随州、孝感、武汉至江汉平原。湖北长距离跨区域传输的潜在污染源区为河南、安徽、江苏、山东等地。2015年冬季湖北省17个地（市）平均外源贡献率为42%，而对于重污染过程，平均外源贡献率高达66%，外来源输送对湖北重污染过程贡献非常显著。对外源传输型，我国东南地区为主要敏感区，气压（气温）变化与PM2.5输送显著负（正）相关，对维持南、北两支矢量带（PM2.5输送与风场相关），推动偏南和偏东气流起到积极作用。此外，伊朗高原天气系统通过上下游效应对东亚地区大气环流起到一定影响，从而也间接影响了区域污染输送。对本地累积型，冬季风环流系统为主要影响天气系统，在弱的冬季风环流形势下，蒙古高压系统偏弱、西太平洋地区海平面气压值偏高，对应湖北本地累积污染总量贡献大。

Numerical Simulation on the Characteristics of PM2.5 Heavy Pollution and the Influence of Weather System in Hubei Province in Winter 2015

Using the WRF/Chem zero-emission scenario simulation scheme, the simulated PM2.5 concentration in Hubei Province from 2 December 2015 to 31 January 2016 was separated into regional transmission component and local accumulation component. Based on the statistical analysis of numerical simulation results, the transmission channel of pollutants and the transmission contribution rate in Hubei Province as well as the influence of weather systems in key areas on different pollution components were studied. It was found that the heavy pollution process is dominated by the northerly and the easterly winds, showing the obviously regional transport characteristics. There are two main channels for pollutant transmission. The first is from Nanyang Basin in Henan Province to Xiangyang and into Jianghan Plain in Hubei Province, and the second is from Xinyang in Henan Province to Suizhou, Xiaogan and Wuhan, and then into the east of Jianghan Plain. The potential pollution source of the long-distance regional transmission lies in Henan, Anhui, Jiangsu, Shandong Provinces etc. In the process of heavy pollution, the contribution rate of external sources is as high as 66% on average for all cities, and the contribution rate is over 75% for the cleaner cities. The regional transport component shows, that in southeast China, which is the main sensitive region, the correlation of pressure (temperature) change and PM2.5 conveying is significantly negative (positive), having a good effect in maintaining the two vector belts of south and north associated with wind field (PM2.5), and promoting the south and east airflow. In addition, the Iranian Plateau weather system has a certain influence on the atmospheric circulation in East Asia through the upstream and downstream effects, which indirectly affects the regional pollution transportation. For the local accumulation component, the winter monsoon circulation system acts as the main weather system. Under the weak winter monsoon circulation, Mongolian high pressure system is weak and the western Pacific sea level pressure is higher, making the pollution contribution of local accumulation component higher.