因为冷却空气会去掉水分,而加热空气不会改变实际的湿度。当空气变冷,它不能持有尽可能多的水蒸气(低饱和蒸汽压)。当空气变暖,它可以"持有"更多的水蒸气(更高的饱和蒸汽压)。——所以当空气冷却到30 s°F,设置限制的水分(露点不能高于30年代)。然后加热到70年代,这是缺少水分。——而当夏天气团加热到80年代,90年代,超越外,气团并不改变水分(事先极限是什么…不同的位置/气团,但相当潮湿的地区如美国东部和欧洲,这是相当通常在50年代/ 60年代和70年代)。当你冷静下来时,它仍然有原来的天花板。所以72°F在夏天会有露水点在像60年代和非常高=更高的相对湿度…但在冬天,72°F将有露水点在像20多岁或30多岁或更低=低相对湿度)(露点是反映更多的* *温度最低的一天。 So if it's 30 °F outside in the daytime, but 10 °F at night... the 10 °F is the ceiling of the dew point of that air mass. Likewise, if it's 90 °F during the daytime, but 65 °F at night, the dew point is capped around 65 °F. But that's still quite moist compared to winter air masses) (Unlike a house heater, quick outdoor warmups are driven by warm fronts/warm air advection, which tend to bring in a different airmass, pulled in from more tropical regions, where the air also has more moisture evaporated into it)