美国英语听力80篇2 Lesson31
时间：2018-12-26 作者：英语课 分类：美国英语听力80篇
[00:06.97]An Israeli study has shown that air pollution from cities and industry can reduce rain and snowfall.
[00:17.53]It says the problem appears to be linked to the number of pollution particles in clouds.
[00:24.82]Daniel Rosenfeld of Hebrew University in Jerusalem organized the study.
[00:32.24]His findings were reported in the publication Science.
[00:36.70]Mister Rosenfeld observed air pollution over Australia, Canada and Turkey from cities and factories.
[00:46.47]He used images provided by a satellite orbiting Earth.
[00:52.35]The satellite has instruments that can measure clouds and rainfall.
[00:58.57]Raindrops form in clouds with little or no pollution when water in the air collects around dust particles.
[01:09.07]The study notes that about 1,000,000 small droplets 1 are required to form a drop of water large enough to fall to earth.
[01:20.04]Mister Rosenfeld observed the movement of the air pollution as it floated away from cities,
[01:28.89]power production centers and oil treatment centers.
[01:33.36]He found that heavily polluted clouds do not produce as much rain as cleaner clouds.
[01:40.94]He says this is because polluted clouds are made of only very small water droplets.
[01:49.58]Mister Rosenfeld says polluted clouds have too many dust particles.
[01:56.32]The large number of particles results in the formation of too many water droplets that are too small.
[02:05.26]They are not big enough to form raindrops.
[02:09.10]The smaller droplets also are slower to freeze and do not easily form ice particles for SHOW.
[02:19.10]Last year, Mister Rosenfeld found that burning trees and other plants also reduces rainfall amounts.