Why is it so cold this year?

This year is the most extreme year in recent ten years.

The reporter learned from China Meteorological Bureau that the weather and climate characteristics of China in 20 10 and 12 were slightly higher temperature and more precipitation. The national average temperature is -3.5℃, which is 0.2℃ higher than the normal period of -3.7℃. The national average precipitation is17.2mm, which is more than the normal period (8.3mm) 1. 1 times, and it is the third highest since 196 1 year. In June 5438+February, there were four cold air attacks in China, which were wide in scope, strong in intensity, with many extreme breakthroughs and heavy in impact. During the period of 65438+February, the daily cooling range of 38 stations in * * * exceeded the historical extreme value, with the daily cooling range of 17.9℃ at Liangcheng Observatory in Inner Mongolia and 18.6℃ at Fushun in Liaoning. In addition, the meteorological drought developed in North China and Huanghuai from June to February in 5438. It is foggy in Sichuan, Chongqing, Guizhou, Hunan and Fujian.

Chen Zhenlin, director of the Emergency Disaster Reduction and Public Service Department of China Meteorological Bureau, said that this year is the year with the greatest frequency, intensity and impact of extreme weather and climate events in China in the past decade, in which the number of extreme precipitation events stations in the whole year is the highest in the past decade, the number of high temperature days in summer is the highest since 196 1, and the average highest temperature in summer is the highest since1. Although the number of typhoons in the western Pacific is the least since the founding of New China (the same as 1998), the proportion of typhoons landing is the highest on record.

La Nina event affects low temperature

Chen Zhenlin said that since July 20 10, the sea surface temperature in the equatorial Middle East and Pacific Ocean has cooled for five months, and the comprehensive intensity has reached the standard of La Ni? a event, forming La Ni? a event, that is, the sea surface in the equatorial Middle East and Pacific Ocean is unusually cold in a large area. The analysis of historical events shows that La Nina event is beneficial to the strong wind in winter in China, which leads to the overall cold climate in winter and the dryness in North China and South China, which may lead to staged extreme low temperature events.

Zhou Bing, the Climate Prediction Office of the National Climate Center, said that it is not contradictory to have extremely cold weather in the context of global warming. From the situation of climate change, we can see that climate change is not only climate change, but also the gap between years. According to preliminary analysis, the climate system is generally balanced, and the alternating cold and warm conditions are still interdependent. When we are very cold, it is very warm over the Pacific Ocean and the Atlantic Ocean.

He said that the recent snowstorms in Europe, North America and China were mainly caused by the abnormal atmospheric circulation system, which was manifested in three aspects: first, a huge blocking system appeared mainly in the middle and high latitudes, which instilled air along the northwest and southeast directions; Second, the three channels of polar cold air affected North America, Europe and northern China respectively. The weather in the third section is still changing, so we see that sometimes there will be a snowstorm, and sometimes it will appear when the snowstorm stops. At present, the atmospheric circulation system is relatively stable, so the stability of blocking system is beneficial to the occurrence of cold air.

In addition, La Nina incident is the most extreme this year, and its development speed is the fastest among all La Nina incidents since 195 1. Due to the subtropical circulation stimulated by La Nina event, tropical anomalies are associated with atmospheric anomalies in the middle and high latitudes.

Chen Zhenlin said that according to the forecast of the weather in China this winter and next spring, the possibility of four consecutive low-temperature rain, snow and freezing disasters in 2008 is still low. However, due to many factors such as La Nina incident, the possibility of a very strong cooling process cannot be ruled out.

The Millennium extreme cold theory is hard to support.

This autumn, the "Millennium Extreme Cold Theory" was widely circulated around the world, but experts from China Meteorological Bureau believed that this winter was not always cold, and it was definitely not the "Millennium Extreme Cold".

Song Lianchun, director of the National Climate Center, said that the scientific basis for La Nina's "Millennium Extreme Cold" is very inadequate. He believes that it is even more "irrelevant" to link La Nina with the Gulf Stream, because they belong to different time scales. La Nina is an interannual scale, which fluctuates greatly every year. The Atlantic warm current is relatively stable, mainly showing a long-term change of more than ten years. Observations in recent decades show that the Atlantic warm current has only a weak decreasing trend. At present, there is still not enough scientific evidence to prove that La Nina is directly related to the Gulf Stream.

Secondly, La Nina's direct influence is limited to the tropical Pacific Ocean, and its influence on the weather and climate in the middle and high latitudes is indirect and complicated. Song Lianchun, for example, said that since 1986, there have been four "La Nina" incidents in Europe, only two of which were cold winters. During the La Nina incident from February 65438+ in 2007 to February 2008, the temperature in Europe was generally warmer than normal 1℃ to 4℃, and there was no cold phenomenon. Therefore, the so-called "Millennium Extreme Cold" lacks scientific basis.