博文
卫星观测到的六月中旬中国的秸秆燃烧现象
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From:
http://earthobservatory.nasa.gov/IOTD/view.php?id=78256
Wheat Fires in China
In mid-June, agricultural fires and industrial pollution combined to leave a thick pall of haze over central China. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured these true-color (top) and false-color (bottom) images of the fires and haze. Both images were acquired at 10:55 a.m. local time (02:55 UTC) on June 13, 2012.
Smoke and actively burning fires (shown with red outlines) are visible in the true-color image, as well as a large burn scar. The false-color image reveals details of the burn scar that aren’t readily apparent in the true-color view. Although the burn scar looks uniform, the false-color view indicates that numerous fields with unburned vegetation (shown as green) are scattered throughout the area. The cities of Bozhou, Huaibei, and Suzhou, which appear as gray patches, were the closest cities to actively-burning fires when Terra acquired the images.
This area falls within the North China Plain, a fertile and densely-populated region that’s home to about a quarter of China's cultivated land and 35 percent of the country's agricultural yields. The area’s staple crops are wheat and maize, and the two crops are generally grown in rotation. Farmers sow winter wheat in mid-October and harvest it at the end of May. In June, farmers burn the remaining plant residue to fertilize the soil for the upcoming maize crop. About 75 percent of all fires in the North China Plain occur in June. A second peak in fire activity occurs in October after the maize harvest.
Smoke from agricultural burning contains a number of substances that pose a hazard to human health, notably black carbon and organic carbon. Fires also emit carbon monoxide and nitrogen oxides (NOx), volatile precursor gases that react to form ground-level ozone. The World Bank estimated in 2007 that about 350,00 to 400,000 people die prematurely each year in China because of outdoor air pollution.
Since the 1990s, the number of
agricultural fires in the country has decreased because the government began
enacting a series of regulations aimed at prohibiting field burning. However,
the practice remains common.
References
- BBC. (2007, July 3). China 'Buried Smog Death finding'. Accessed June 13, 2012.
- Huang, X. (2012, Jan. 5) A High-Resolution Emission Inventory of Crop Burning in Fields in China Based on MODIS Thermal Anomalies/Fire Products. Atmospheric Environment.
- Li, H. (2010). Agricultural Fire Impacts on the Air Quality of Shanghai During Summer Harvesttime. Aerosols and Air Quality Research.
- Zhang, H (2008). A Laboratory Study of Agricultural Crop Residue Combustion in China: Emission Factors and Emission Inventory. Atmospheric Environment.
农业用火和工业污染共同造成了华中的雾霾天气。Terra卫星上的MODIS于六月13日当地时间上午10：55拍摄、观测到的真彩色（上图）和伪彩色（下图）影像。
文中介绍说该区域位于华北平原， 主要作物是小麦和玉米。十月中旬播种冬小麦， 来年五月底收割。 六月农民焚烧秸秆积肥，为种植玉米做准备。华北平原约75%的用火发生在六月；十月玉米收割完后用火数量又会显著增加。自90年代以来由于政府的管理， 农业用火已有减少， 但秸秆焚烧现象仍很普遍。
几个问题。 1. 卫星影像上能观测到多大范围内的秸秆焚烧现象？2. 当时附近区域的大气环流情况如何， 污染物如何输送运移到南京, 甚至武汉？
真彩色影像中， 红色斑点为正在燃烧的火点； 烟雾和黑褐色的过火迹地清晰可见。标出的三个城市为安徽亳州、淮北 和宿州。
伪彩色影像中， 可以看到过火迹地内部还有未燃烧的植被（显绿色）。
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