File:Sichuan Haze.jpg
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摘要
描述Sichuan Haze.jpg |
English: A layer of haze filled China’s Sichuan Basin on January 23, 2014, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite acquired this natural-color image. The haze obscured many features usually visible in satellite images of the area, including Sichuan province’s largest city, Chengdu. In the eastern part of the basin the tops of a series of ridges were visible above the layer of pollution. Skies were clear in the highlands west of the basin, while tendrils of pollution snaked into valleys northeast and southeast of it.
On the day this image was acquired, measurements from ground-based sensors at the U.S. Consulate in Chengdu reported PM2.5 measurements of 267 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 PM2.5 aerosol particles come from the burning of fossil fuels and biomass (wood fires and agricultural burning). The World Health Organization considers PM2.5 to be safe when it is below 25. Haze in this region tends to worsen in the winter, when cold, heavy air traps pollutants near the surface. In this case, the haze was likely trapped in the Sichuan Basin by a temperature inversion. Normally, air is warmest near the surface of the Earth. Occasionally, a mass of warm air will move over cooler air so that the atmosphere actually warms with altitude. Since the cool air does not have the energy to rise through the warm air, vertical circulation slows and air becomes trapped near the surface. Any pollutant that enters the air gets trapped as well, and haze builds up over time. Temperature inversions often form in basins and valleys because surrounding higher-elevation land helps contain cold air. Daily images of the Sichuan Basin show that that the pollution has persisted for several days. |
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來源 | [1] |
作者 | NASA image courtesy Jeff Schmaltz, LANCE MODIS Rapid Response. Caption by Adam Voiland |
協議
Public domainPublic domainfalsefalse |
This file is in the public domain in the United States because it was solely created by NASA. NASA copyright policy states that "NASA material is not protected by copyright unless noted". (See Template:PD-USGov, NASA copyright policy page or JPL Image Use Policy.) | ||
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21 3 2009
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現時 | 2017年4月11號 (二) 06:52 | 4,400 × 3,400(3.97 MB) | NoGhost | User created page with UploadWizard |
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高 | 3,400 px |
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壓細方法 | 未壓過 |
像素構成 | RGB |
攞放方向 | 正常 |
部位數 | 3 |
橫解像度 | 72 dpi |
直解像度 | 72 dpi |
資料編排 | chunky 格式 |
用過嘅軟件 | Adobe Photoshop CS6 (Macintosh) |
檔案更動日期時間 | 2014年1月24號 (五) 11:13 |
色彩空間 | 未校啱色 |
制成數碼日期時間 | 2014年1月23號 (四) 13:12 |
Date metadata was last modified | 2014年1月24號 (五) 06:13 |
Unique ID of original document | xmp.did:1BCE92D96820681180839040F1C1E035 |