2015年4月9日 星期四

雷電打擊最多的地區

NASA Map Shows Where Lightning Strikes Most Around the World
BY DOUGLAS MAIN 4/7/15 AT 3:57 PM

太空總署的地圖顯示雷電打擊最多的地區

Lightning strikes worldwide between 1995 and 2013. Areas with the most activity appear light pink. NASA

NASA has been recording just about every lightning strike for much of the past 20 years, and it has produced a map to show where this phenomenon is most common.
It turns out that the eastern Democratic Republic of the Congo and Lake Maracaibo in northwestern Venezuela have the most lightning. Both places have a lot of precipitation and the ideal humidity and atmospheric conditions for thunderstorms to form, according to the NASA Earth Observatory.
As the map shows, lightning is much more frequent over land than water, and it is more common in the tropics, where there is more heat, and thus more energy for producing storms. Areas that are lighter in color have more lightning, and some places have as much as 150 strikes per square kilometer per year; one square kilometer is about one-third the size of New York's Central Park.
The map was produced using data collected between 1995 and 2013 by NASA’s Tropical Rainfall Measuring Mission satellite and the OrbView-1/Microlab satellite.
Lightning is formed within clouds. “As ice particles within a cloud collide and break apart, the smaller particles acquire positive charge and the larger particles acquire negative charge,” explains LiveScience, a science news site. “Updrafts of wind then push the small particles upward, until the top of the cloud is positively charged, while the bottom of the cloud is negatively charged. This separation of charge creates a huge electric potential within the cloud, and between the cloud and the ground.” Lightning is the discharge of electricity between cloud and Earth, which diffuses this difference in potential. 
Lightning strikes over Lake Maracaibo, in Venezuela, which has some of the most frequent lightning in the world.JORGE SILVA / REUTERS

Condensed from Newsweek.

jUSTIN lAI 

04/08/15  (Eng.)


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