Why is there a warm winter?

There are many reasons for warm winter, which are often the result of a combination of many reasons. The reasons for the warm winter are as follows:

China is in a warm period.

The temperature changes periodically. According to the statistics of meteorological data in the last hundred years, the temperature in China has a period of about 30 years. It was cold before the 1920s, warm in the 1920s-40s, cold in the 1950s-1970s, and warm after the 1980s. At present, China is still in this recovery period.

The warm winter weather in China is concentrated in the northwest, north China and northeast China, and the periodicity of these areas is more obvious.

◆ Greenhouse effect

Since the industrialization of the last century, due to the influence of human activities, the content of greenhouse gases such as carbon dioxide in the atmosphere has increased rapidly, leading to a significant increase in global temperature. The continuous warm winter in China is happening against the background of global warming. China is located at the southern end of the warmer region in eastern Siberia, and the warmer climate in China is an integral part of the warmer climate in the world.

◆ The influence of El Nino

In recent 50 years, after the occurrence of El Ni? o, the probability of high temperature in winter in China is high. Since 195 1 year, there have been 15 El Nino phenomena and 14 warm winters in China. Since 1980s, the SST in the equatorial eastern Pacific Ocean has been on the high side, and El Nino has occurred frequently, which has kept China warm for more than ten years.

◆ zonal circulation prevails and cold air activity is weak.

The prevailing zonal circulation and weak cold air in the south are the direct reasons for the warmer winter in China. Since 1986, zonal circulation has prevailed over East Asia, mostly a relatively gentle westerly airflow, with less meridional airflow in the north, few Siberian cold air brought into China, and few cold waves appeared. In the linear airflow, even if there are some weak airflow to the north, the cold air brought into China is small in quantity and strength, and the pressure range of cold air to the south is not large, which also causes the phenomenon of warm winter.

◆ The subtropical high in the western Pacific is strong.

The western Pacific subtropical high located in the southeast of China is a warm high, and its intensity directly affects the cold and warm weather in winter in China. When this high pressure is strong, it is beneficial for the warm air flow on the ocean to be transported to China, and China is prone to warm winters.

◆ The number of volcanic eruptions has decreased.

Volcanic ash produced during volcanic eruption rises into the air, producing a "parasol effect". On the one hand, the volcanic ash layer at high altitude reflects the solar radiation, on the other hand, it reduces the solar radiation reaching the surface of the earth and lowers the temperature of the earth. According to statistics, the number of strong volcanic eruptions in the warm cycle of the earth's climate is half less than that in the cold cycle. Since the 1980s, the number of large-scale volcanic eruptions in the world has obviously decreased, which is also one of the reasons for global warming.

◆ Snowfall reduction in Eurasia

The decrease of snowfall in Eurasia is not conducive to the strengthening of Siberian cold air mass, which weakens the cold air invading China. Since the mid-1980s, due to the decrease of snow in Eurasia, the Siberian cold high is weak, which is also one of the reasons for the warmer climate in China.

El Ni?o phenomenon

"El Nino" phenomenon is an abnormal warming phenomenon in the waters near the equator in the United States (4 degrees north latitude to 4 degrees south latitude and about 0/50 degrees west longitude to 90 degrees west longitude).

It turns out that the Pacific Ocean is not completely horizontal. In the Pacific Ocean in the southern hemisphere, as the strong southeast trade winds swept the northwest, the seawater was pushed from the southeast to the west. Therefore, the ocean surface near Australia is about 50 cm higher than that in South America. At the same time, the cold water in the lower ocean along the coast of South America is constantly turning up, which has delivered a lot of nutrients to marine life such as fish and waterfowl here.

It is puzzling that this normal virtuous circle will be broken every few years. The southeast wind, which has always been strong, gradually weakens and may even reverse to the west wind. The upwelling of cold water along the eastern Pacific coast will also weaken or disappear completely. Therefore, the temperature of the upper seawater in the Pacific Ocean rises rapidly and flows back to the east. This rising El Ni? o ocean current will cause the sea level in the East Pacific to rise by 20-30 cm compared with the normal sea level, and the temperature will rise by 2-5 degrees Celsius. This abnormal temperature rise in turn heats the atmosphere, leading to unpredictable climate anomalies. For example, El Ni? o caused unprecedented droughts in southern Africa, Indonesia and Australia, and brought heavy rains, floods and mudslides to Peru, Ecuador and California. El Nino caused more than 65,438+0,500 deaths and 8 billion dollars in material losses. So far, scientists have not found an accurate answer about the cause of El Nino phenomenon. Some people think that the ocean current may be warmed by the volcanic eruption in the Pacific Ocean or the heating effect of lava ejected from the crustal fracture, which in turn leads to the weakening and reversal of the trade winds. Others infer that it may be caused by the uneven annual speed of the earth's rotation. They say that the interannual speed of the earth's rotation is caused by uneven acceleration. They say that whenever the annual speed of the earth's rotation changes from acceleration to deceleration, the El Ni? o phenomenon will occur. Worryingly, El Nino phenomenon appears more and more frequently. Originally thought to come once every five years, seven years or even 10 years, it later appeared in a cycle of three to seven years. But since the 1990s, it seems to happen every two or three years.

Although the cause of El Nino phenomenon has not been ascertained, human beings have not resigned themselves to fate and done nothing. 1986 foreign scientists successfully predicted the coming of El Nino one year in advance, and actively explored the relationship between greenhouse effect and El Nino phenomenon. It can be predicted that mankind will eventually be able to solve the mystery of nature that ravages mankind and find ways to avoid its harm.