【摘要】：利用四川盆地及其周邊地區(qū)氣象站點(diǎn)的觀測(cè)數(shù)據(jù)進(jìn)行了近50年來(lái)四川盆地區(qū)域內(nèi)大氣能見度及霾日的時(shí)空分布特征和驅(qū)動(dòng)因素的一系列分析,并在此基礎(chǔ)上利用1999-2013年的全球再分析數(shù)據(jù)(Final Operational Global analysis)分析了四川盆地及其周邊地區(qū)大氣結(jié)構(gòu)和邊界層變化特征,探索了四川盆地大地形和高氣溶膠中心及其變化的關(guān)聯(lián),以及大氣動(dòng)力熱力特性和特殊的大氣邊界層結(jié)構(gòu)特征。最后,利用在線大氣化學(xué)模式WRF-Chem模擬了2014年1月12～20日四川盆地一次持續(xù)性的重霾過(guò)程,并另外設(shè)計(jì)有無(wú)盆地地形的敏感性試驗(yàn),進(jìn)一步模擬探討盆地地形的動(dòng)力、熱力強(qiáng)迫作用以及各氣象因子變化對(duì)盆地霾污染物變化的作用,并定量評(píng)估了地形作用對(duì)四川盆地PM2.5影響的貢獻(xiàn),探討了盆地特殊地形作用的影響機(jī)理。主要研究?jī)?nèi)容和結(jié)論如下：(1)近50年來(lái)盆地能見度分布呈現(xiàn)盆地低(約18.9km),且呈明顯減少的變化趨勢(shì),氣候傾向率約-0.91kmm.(10a)-1。大氣干消光系數(shù)呈增加,人口密度及燃煤增加導(dǎo)致大氣細(xì)粒子排放增多,霾日數(shù)急速增加,氣候傾向率約9.6d.(10a)-1。其中冬季1月污染最嚴(yán)重,夏季7月相對(duì)清潔。高濕、弱風(fēng)是導(dǎo)致盆地區(qū)域霾污染日趨嚴(yán)重的關(guān)鍵氣象因素。(2)地形作用對(duì)盆地大氣環(huán)境的影響主要表現(xiàn)在：1)盆地上空受地形影響形成強(qiáng)的下沉氣流,抑制了盆地空氣污染物的向上擴(kuò)散,盆地內(nèi)這種大氣垂直結(jié)構(gòu)呈現(xiàn)明顯的季節(jié)變化特征,冬季下沉氣流最強(qiáng),與冬季霾污染最嚴(yán)重表現(xiàn)一致；2)高原背風(fēng)坡“避風(fēng)港”效應(yīng),盆地區(qū)域平均風(fēng)速緯向偏差約lm.s-1,地處背風(fēng)坡的弱風(fēng)區(qū),多靜弱風(fēng)；3)在900hpa到850hpa大氣層表現(xiàn)為風(fēng)速弱切變,湍流混合作用弱；4)盆地近地面貼地逆溫與高空氣流下沉增溫形成脫地逆溫,使得盆地內(nèi)大氣層結(jié)穩(wěn)定。這些地形作用不利于盆地內(nèi)大氣氣溶膠的擴(kuò)散、輸送,容易造成污染物的累積形成的霾天氣。(3)盆地重霾期間有無(wú)地形的模擬試驗(yàn)表明：地形作用使得盆地內(nèi)大部分地區(qū)10m風(fēng)速減少約1.5m.s-1,地面2m溫度升高約10℃,邊界層高度降低約100～150m。地形作用使得盆地區(qū)域內(nèi)PM2.5濃度偏高約150ug.m-3,地形影響貢獻(xiàn)率約70%。地形對(duì)污染物的堆積作用表現(xiàn)在污染過(guò)程中,尤其是重污染過(guò)程。高空背風(fēng)坡西風(fēng)帶下沉氣流被加強(qiáng),氣流下沉增溫促使2500m～3000m高空形成脫地逆溫,同時(shí)在地形作用下使得貼地逆溫被加強(qiáng),是導(dǎo)致盆地本次重霾過(guò)程的一個(gè)關(guān)鍵因素。
[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，

本文編號(hào)：2374213