202 1 Why is it so cold in winter?

Because? 202 1 is the colder, warmer, wetter and drier extreme weather in the "Double La Nina Year".

La Nina event refers to a large-scale cold water phenomenon with a certain intensity and duration caused by the abnormal sea surface temperature in the equatorial Middle East Pacific Ocean. The data show that after La Nina event, the probability of overall cold in winter in China is about 70%, and the probability of warm is about twice.

Reasons for the formation of the Double La Nina Year;

So how was La Nina formed? El Nino is related to the warming of sea surface temperature and the weakening of trade winds in the equatorial Middle East Pacific, while La Nina is related to the cooling of sea surface temperature and the strengthening of trade winds in the equatorial Middle East Pacific. So La Nina is actually the product of the interaction between tropical ocean and atmosphere.

The motion of the ocean surface is mainly constrained by the sea surface wind. Because of the existence of trade winds, a large amount of warm water is blown to the equatorial western Pacific Ocean and blown away in the equatorial eastern Pacific Ocean, which is mainly supplemented by cold water below the sea surface. The SST in the equatorial eastern Pacific is obviously lower than that in the western Pacific.

When the trade winds strengthen, the upwelling phenomenon of deep seawater in the equatorial eastern Pacific becomes more intense, resulting in abnormally low sea surface temperature, which makes the airflow in the equatorial eastern Pacific sink, while the upward movement of the airflow in the equatorial western Pacific intensifies, which is conducive to the strengthening of the trade winds, thus further aggravating the development of cold water in the equatorial eastern Pacific and triggering the so-called La Nina phenomenon.