Water vapor in the lower atmosphere can vary in amount from a mere trace in arid regions to about 4% by volume in moist areas.

大气低层的水汽量在干燥地区（量）甚微，而在潮湿地区按体积占4%左右。

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Water vapor accounts for about 4% by volume in moist areas.

在气候潮湿地区，水汽按体积占(空气体积)4%左右。

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The precipitation area has a good relationships with low level positive vorticity, water vapor, pressure energy, moist enthalpy, potential vorticity etc.

诊断分析中发现暴雨落区和低层正涡度、水汽、压能、湿焓、位涡等有很好的对应关系。

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