Cause analysis of extremely cold weather

In view of the causes of the recent "extreme cold" weather, Guo Yanjun, a senior engineer in the Climate Monitoring Office of the National Climate Center of China Meteorological Bureau, believes that since the winter of June 5438+February last year, the La Nina event in the equatorial Middle East Pacific has continued to develop, which easily leads to the low temperature in most winters in China. At the same time, the SST in the North Pacific continues to be warmer, the Siberian high continues to be stronger, and the thermal difference between land and sea increases, which is beneficial to the strong winter winds in East Asia and brings cold air.

Guo Yanjun said, especially in the middle and late days of 65438+ 10, on the eve of the Spring Festival, the atmospheric circulation changed obviously, the Arctic oscillation took an obvious turn, and the polar cold air spread southward. At the same time, the establishment and maintenance of the blocking high in the Urals at high latitudes helped the cold air in the north to move southward and affect China. On the other hand, the Ural Mountains and the Sea of Okhotsk often have blocking high pressure. When they remain stable, it is rainy in the south of China and rainy and snowy in winter. When the Urals blocking high pressure weakens and collapses, it will often lead to a cold wave in China.

Why does the Arctic Oscillation lead to extremely cold weather? Li Xiaoquan, chief meteorologist of China Weather Network, explained: "Arctic Oscillation refers to the change of atmospheric pressure in the Arctic. Usually, the Arctic region is controlled by high altitude and strong low pressure, and the corresponding cold air will contract near the North Pole, while the corresponding temperature in mid-latitude is higher; On the contrary, when the high altitude in the Arctic is controlled by high pressure, the cold air in the polar region will be squeezed and erupt southward, and there will be strong cooling and cold wave weather in the area where the cold air mass passes. "