Why do people often say' autumn is crisp'?

The weather in autumn is always cool, pleasant and intoxicating. Why? It turns out that when autumn comes, the warm and humid air has completed the process of transferring from the mainland to the Pacific Ocean, and the dry and cold air in the north has taken its place and started the pace of going south. Because this dry and cold air itself is very dry, it is difficult to condense into clouds. At the same time, the dry and cold air is heavier, so it will sink, and it will become hot when it sinks to the ground. The original clouds in the sky in this area will be reduced because of the heat. Therefore, in these areas controlled by cold air, the weather will become extremely sunny.

In addition, in autumn, the ground absorbs the heat of the sun during the day, because the sky is not covered by clouds at night, and the heat can be freely emitted. After the autumnal equinox, the nights are long and the days are short, the heat absorbed during the day is less than the heat emitted at night, and the ground temperature gradually decreases. At the same time, there is less and less water in the air in autumn, and people are surrounded by dry and cold air, so the water secreted by people's skin is very easy to evaporate. For these reasons, people think it's cool.

So there is what people often say, autumn is crisp. You got it?