四川盆地空气质量气候特征及其大地形影响效应的观测模拟研究
发布时间：2018-12-12 07:47
【摘要】：利用四川盆地及其周边地区气象站点的观测数据进行了近50年来四川盆地区域内大气能见度及霾日的时空分布特征和驱动因素的一系列分析,并在此基础上利用1999-2013年的全球再分析数据(Final Operational Global analysis)分析了四川盆地及其周边地区大气结构和边界层变化特征,探索了四川盆地大地形和高气溶胶中心及其变化的关联,以及大气动力热力特性和特殊的大气边界层结构特征。最后,利用在线大气化学模式WRF-Chem模拟了2014年1月12～20日四川盆地一次持续性的重霾过程,并另外设计有无盆地地形的敏感性试验,进一步模拟探讨盆地地形的动力、热力强迫作用以及各气象因子变化对盆地霾污染物变化的作用,并定量评估了地形作用对四川盆地PM2.5影响的贡献,探讨了盆地特殊地形作用的影响机理。主要研究内容和结论如下：(1)近50年来盆地能见度分布呈现盆地低(约18.9km),且呈明显减少的变化趋势,气候倾向率约-0.91kmm.(10a)-1。大气干消光系数呈增加,人口密度及燃煤增加导致大气细粒子排放增多,霾日数急速增加,气候倾向率约9.6d.(10a)-1。其中冬季1月污染最严重,夏季7月相对清洁。高湿、弱风是导致盆地区域霾污染日趋严重的关键气象因素。(2)地形作用对盆地大气环境的影响主要表现在：1)盆地上空受地形影响形成强的下沉气流,抑制了盆地空气污染物的向上扩散,盆地内这种大气垂直结构呈现明显的季节变化特征,冬季下沉气流最强,与冬季霾污染最严重表现一致；2)高原背风坡“避风港”效应,盆地区域平均风速纬向偏差约lm.s-1,地处背风坡的弱风区,多静弱风；3)在900hpa到850hpa大气层表现为风速弱切变,湍流混合作用弱；4)盆地近地面贴地逆温与高空气流下沉增温形成脱地逆温,使得盆地内大气层结稳定。这些地形作用不利于盆地内大气气溶胶的扩散、输送,容易造成污染物的累积形成的霾天气。(3)盆地重霾期间有无地形的模拟试验表明：地形作用使得盆地内大部分地区10m风速减少约1.5m.s-1,地面2m温度升高约10℃,边界层高度降低约100～150m。地形作用使得盆地区域内PM2.5浓度偏高约150ug.m-3,地形影响贡献率约70%。地形对污染物的堆积作用表现在污染过程中,尤其是重污染过程。高空背风坡西风带下沉气流被加强,气流下沉增温促使2500m～3000m高空形成脱地逆温,同时在地形作用下使得贴地逆温被加强,是导致盆地本次重霾过程的一个关键因素。
[Abstract]:Based on the observational data of meteorological stations in and around the Sichuan Basin, a series of analyses on the spatial and temporal distribution characteristics and driving factors of atmospheric visibility and haze days in the Sichuan Basin over the past 50 years have been carried out. On this basis, the global reanalysis data (Final Operational Global analysis) from 1999 to 2013 are used to analyze the atmospheric structure and boundary layer changes in and around the Sichuan Basin, and to explore the correlation between the large topography and the center of high aerosol in Sichuan Basin. The dynamic and thermodynamic characteristics of the atmosphere and the special structure of the atmospheric boundary layer are also discussed. Finally, an online atmospheric chemistry model (WRF-Chem) is used to simulate a persistent heavy haze process in Sichuan Basin from January 12 to 20, 2014, and a sensitivity test is designed to further simulate the dynamics of the basin topography. The effects of thermal forcing and various meteorological factors on the variation of haze pollutants in the basin are evaluated quantitatively. The contribution of topographic action to PM2.5 in Sichuan basin is evaluated and the influence mechanism of the special topographic action in the basin is discussed. The main research contents and conclusions are as follows: (1) the visibility distribution in the basin is low (about 18.9km) in the last 50 years, and the climatic tendency rate is about -0.91kmm. (10a) -1. The dry extinction coefficient of the atmosphere increased, the population density and coal combustion increased the emission of fine particles, the number of haze days increased rapidly, and the climatic tendency rate was about 9.6 days (10a) -1. In winter January pollution is the most serious, summer July is relatively clean. High humidity and weak wind are the key meteorological factors leading to the increasingly serious haze pollution in the basin. (2) the influence of topographic action on the atmospheric environment of the basin is mainly as follows: 1) strong downdraft formed over the basin under the influence of topography. The upward diffusion of air pollutants in the basin is restrained, the vertical structure of the atmosphere in the basin shows obvious seasonal variation characteristics, and the downdraft is the strongest in winter, which is consistent with the most serious haze pollution in winter. 2) the "haven" effect in the leeward slope of the plateau, the zonal deviation of the mean wind speed in the basin is located in the weak wind zone of the leeward slope, and the wind is mostly static and weak; 3) in the atmosphere from 900hpa to 850hpa, the wind speed is weak shear and the turbulent mixing is weak. 4) the temperature inversion near the surface of the basin and the rising temperature of the upper air flow cause the stability of the inner atmosphere of the basin. These topographic processes are not conducive to the diffusion and transport of atmospheric aerosols in the basin. It is easy to cause the accumulation of pollutants in haze weather. (3) during heavy haze in the basin, the simulated tests show that topographic action reduces the wind speed of 10 m in most areas of the basin by 1.5 m.s-1, and increases the surface temperature by about 10 鈩，
本文编号：2374213
[Abstract]:Based on the observational data of meteorological stations in and around the Sichuan Basin, a series of analyses on the spatial and temporal distribution characteristics and driving factors of atmospheric visibility and haze days in the Sichuan Basin over the past 50 years have been carried out. On this basis, the global reanalysis data (Final Operational Global analysis) from 1999 to 2013 are used to analyze the atmospheric structure and boundary layer changes in and around the Sichuan Basin, and to explore the correlation between the large topography and the center of high aerosol in Sichuan Basin. The dynamic and thermodynamic characteristics of the atmosphere and the special structure of the atmospheric boundary layer are also discussed. Finally, an online atmospheric chemistry model (WRF-Chem) is used to simulate a persistent heavy haze process in Sichuan Basin from January 12 to 20, 2014, and a sensitivity test is designed to further simulate the dynamics of the basin topography. The effects of thermal forcing and various meteorological factors on the variation of haze pollutants in the basin are evaluated quantitatively. The contribution of topographic action to PM2.5 in Sichuan basin is evaluated and the influence mechanism of the special topographic action in the basin is discussed. The main research contents and conclusions are as follows: (1) the visibility distribution in the basin is low (about 18.9km) in the last 50 years, and the climatic tendency rate is about -0.91kmm. (10a) -1. The dry extinction coefficient of the atmosphere increased, the population density and coal combustion increased the emission of fine particles, the number of haze days increased rapidly, and the climatic tendency rate was about 9.6 days (10a) -1. In winter January pollution is the most serious, summer July is relatively clean. High humidity and weak wind are the key meteorological factors leading to the increasingly serious haze pollution in the basin. (2) the influence of topographic action on the atmospheric environment of the basin is mainly as follows: 1) strong downdraft formed over the basin under the influence of topography. The upward diffusion of air pollutants in the basin is restrained, the vertical structure of the atmosphere in the basin shows obvious seasonal variation characteristics, and the downdraft is the strongest in winter, which is consistent with the most serious haze pollution in winter. 2) the "haven" effect in the leeward slope of the plateau, the zonal deviation of the mean wind speed in the basin is located in the weak wind zone of the leeward slope, and the wind is mostly static and weak; 3) in the atmosphere from 900hpa to 850hpa, the wind speed is weak shear and the turbulent mixing is weak. 4) the temperature inversion near the surface of the basin and the rising temperature of the upper air flow cause the stability of the inner atmosphere of the basin. These topographic processes are not conducive to the diffusion and transport of atmospheric aerosols in the basin. It is easy to cause the accumulation of pollutants in haze weather. (3) during heavy haze in the basin, the simulated tests show that topographic action reduces the wind speed of 10 m in most areas of the basin by 1.5 m.s-1, and increases the surface temperature by about 10 鈩，
本文编号：2374213
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