大家都在讨论这几天北方大城市的雾霾以及空气质量问题。 下面是美国NASA的一篇报道。 报道中有几句话值得注意: 1、中国目前处于近几十年来空气质量最糟糕的时期 the nation faced one of the worst periods of air quality in recent history. 2、据美国驻北京大使馆的设备测定,1月14日,PM2.5高达291。 3、按照相关算法,空气质量指数AQI达到了341,而当这个值小于50时才被认为是适合人体健康的。(不知道这个AQI与常用的API有何异同?我国发布的API没有考虑PM2.5,所以去年以来饱受争议。) 此外,大家可能会感兴趣的是,这两张遥感图像上,美国人错把天津当上海了。前两天两位姓陈的科学网博主为地理信息公开的问题吵得不可开交。不知道看到这两张图的解译结果,作何感想? 以下是原文: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ acquired January 14, 2013 download large image (7 MB, JPEG, 5000x6400) acquired January 3, 2013 download large image (8 MB, JPEG, 5000x6400) View Image Comparison View Both Images Residents of Beijing and many other cities in China were warned to stay inside in mid-January 2013 as the nation faced one of the worst periods of air quality in recent history. The Chinese government ordered factories to scale back emissions, while hospitals saw spikes of more than 20 to 30 percent in patients complaining of respiratory issues, according to news reports. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired these natural-color images of northeastern China on January 14 (top) and January 3, 2013. The top image shows extensive haze, low clouds, and fog over the region. The brightest areas tend to be clouds or fog, which have a tinge of gray or yellow from the air pollution. Other cloud-free areas have a pall of gray and brown smog that mostly blots out the cities below. In areas where the ground is visible, some of the landscape is covered with lingering snow from storms in recent weeks. (Snow is more prominent in the January 3 image.) At the time that the January 14 image was taken by satellite, ground-based sensors at the U.S. Embassy in Beijing reported PM 2.5 measurements of 291 micrograms per cubic meter of air. Fine, airborne particulate matter (PM) that is smaller than 2.5 microns (about one thirtieth the width of a human hair) is considered dangerous because it is small enough to enter the passages of the human lungs. Most PM 2.5 aerosol particles come from the burning of fossil fuels and biomass (wood fires and agricultural burning). The World Health Organization considers PM 2.5 to be safe when it is below 25. Also at the time of the image, the air quality index (AQI) in Beijing was 341. An AQI above 300 is considered hazardous to all humans, not just those with heart or lung ailments. AQI below 50 is considered good. On January 12, the peak of the current air crisis, AQI was 775 the U.S Embassy Beijing Air Quality Monitor—off the U.S. Environmental Protection Agency scale—and PM 2.5 was 886 micrograms per cubic meter. 1. Resources 2. Air Pollution in China: Real-time Air Quality Index Visual Map. Accessed January 14, 2013. 3. China Air Daily. Accessed January 14, 2013. 4. U.S Embassy Beijing Air Quality Monitor. Accessed January 14, 2013. 1. References 2. Associated Press, via Yahoo News (2013, January 14) Beijing warns residents after off-the-charts smog . Accessed January 14, 2013. 3. NASA (2010, September 22) New Map Offers a Global View of Health-Sapping Air Pollution. Accessed January 14, 2013. 4. NASA Earth Observatory (2012, March 23) Satellites Map Fine Aerosol Pollution Over China. 5. The New York Times (2013, January 14) China allows media to report alarming air pollution crisis. Accessed January 14, 2013. 6. Yahoo News (2013, January 14) China's air pollution problem slideshow. Accessed January 14, 2013. NASA image courtesy Jeff Schmaltz, LANCE MODIS Rapid Response. Caption by Mike Carlowicz. Instrument: Terra - MODIS