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.
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。