Hu Yue, Yao Ling, Cheng Zhen, Wang Yungang
College of Environment and Civil Engineering, Chengdu University of Technology, Chengdu 610059, China.
Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
Environ Res. 2017 Nov;159:466-473. doi: 10.1016/j.envres.2017.08.018. Epub 2017 Sep 18.
Millions of premature deaths worldwide every year mostly in China and India are contributed by the poor air quality. The atmospheric visibility is a proven indicator of the ambient air quality. In this study, nine megacities were selected, including Beijing, Shanghai and Guangzhou from China, Chicago, Los Angeles (LA) and New York City (NYC) from the United States, and Mumbai, Chennai and Jaipur from India. The data of visibility, aerosol optical depth (AOD), and meteorological factors from 1973 to 2015 were collected. The temporal variations of annual and monthly percentages of bad days (visibility < 5km) and good days (visibility > 15km) were evaluated. Visibility of Chicago, LA and NYC gradually improved during the past 43 years and has reached a very good level (good day percentages: 75-88%; bad day percentages: 0 - 4%). Conversely, visibility in Mumbai, Chennai and Jaipur continued deteriorating and suffered an extremely poor visibility situation in recent years (good day percentages: 0; bad day percentages: 6-100%). Likewise, visibility in Beijing, Shanghai and Guangzhou has experienced the worsening period during the industrial development from 1970s and turned better after the 1990s. A strong seasonal pattern of bad day percentages of each year were observed in most cities, especially in the winter, which is caused by the fossil fuel combustion for heating, relatively high relative humidity, and other unfavorable meteorological conditions. The low visibility events occurred more frequently in days with low wind speeds and specific wind directions, further explaining the seasonal patterns of visibility. With population growth from the period of 2000-2010 to the period of 2011-2015, AOD and bad day percentages both increased in Mumbai, Chennai, Jaipur and Beijing while others were relatively stable. This study demonstrated that the macro-control of pollution emissions could effectively reduce air deterioration. The relationships among visibility variation, meteorological, pollutant and population factors provide valuable scientific support for public health researches, air quality managements (monitoring and forecasting), and clean energy initiatives.
全球每年数百万例过早死亡主要发生在中国和印度，这是由空气质量差导致的。大气能见度是已被证实的环境空气质量指标。在本研究中，选取了九个特大城市，包括中国的北京、上海和广州，美国的芝加哥、洛杉矶和纽约市，以及印度的孟买、钦奈和斋浦尔。收集了1973年至2015年的能见度、气溶胶光学厚度（AOD）和气象因素数据。评估了年和月中坏天（能见度<5公里）和好天（能见度>15公里）百分比的时间变化。在过去43年里，芝加哥、洛杉矶和纽约市的能见度逐渐改善，已达到非常好的水平（好天百分比：75 - 88%；坏天百分比：0 - 4%）。相反，孟买、钦奈和斋浦尔的能见度持续恶化，近年来能见度状况极差（好天百分比：0；坏天百分比：6 - 100%）。同样，北京、上海和广州的能见度在20世纪70年代工业发展期间经历了恶化期，90年代后有所好转。在大多数城市观察到每年坏天百分比有很强的季节性模式，尤其是在冬季，这是由取暖用化石燃料燃烧、相对较高的相对湿度以及其他不利气象条件造成的。低能见度事件在风速低和特定风向的日子里更频繁发生，进一步解释了能见度的季节性模式。从2000 - 2010年到2011 - 2015年，随着人口增长，孟买、钦奈、斋浦尔和北京的AOD和坏天百分比都有所增加，而其他城市相对稳定。本研究表明，对污染排放的宏观控制可以有效减少空气质量恶化。能见度变化、气象、污染物和人口因素之间的关系为公共卫生研究、空气质量管理（监测和预报）以及清洁能源倡议提供了有价值的科学支持。
