Why is the temperature especially high in coastal areas? [

Persistent high temperature and drought are caused by comprehensive factors.

Zhang Qiang, a researcher, graduated from the Department of Atmospheric Science of Nanjing University from 65438 to 0984, and is now the director of the Climate Impact Assessment Office of the National Climate Center. He believes that the extreme high temperature and dry weather in China, Chongqing, Sichuan and other places this year first occurred under the influence of global warming, which is often said to be caused by global climate change. The main reasons are as follows:

First, the SST in the western Pacific is 0.5℃ higher than in previous years, which makes the strong convective weather active. The subtropical high is located in the north and west of previous years. Especially since August, the ridge line of the subtropical high has been maintained at 27 N every day, while the average ridge line of the subtropical high in August is 26 N. At the same time, the western Pacific subtropical high is slightly west than normal. This form of subtropical high is not conducive to bringing warm and humid air from the south to the east of southwest China. On the other hand, controlled by the stability of continental high, downdraft generally exists over eastern Sichuan and Chongqing, and convection activities are restrained, resulting in less precipitation, higher temperature and severe drought in this area. This climate situation has long controlled the middle reaches of the Yangtze River in China, resulting in high temperature weather with long rainy days, which has a very prominent impact on Chongqing, Sichuan and other regions.

Second, the snowfall in the Qinghai-Tibet Plateau last winter and this spring was about 20% less than normal, and the thermal conditions were strong. As a cold source, the decrease of snow on the Qinghai-Tibet Plateau leads to obvious plateau thermal effect, reduced output water vapor and increased height field. This can be clearly seen from the "Correlation Diagram between Winter and Summer Snow Days in Qinghai-Tibet Plateau and Summer Precipitation in China" shown by Zhang Qiang, a researcher.

Third, the cold air in the north is weak this year. The cold air is relatively stable, instead of moving south to the surrounding areas of Chongqing, it has moved to the east of China, resulting in abundant rain in Beijing and Huanghuai this year.

The influence of urban heat island effect can not be ignored.

Gao Ge, a senior engineer in the Climate Impact Assessment Office of the National Climate Center, has just returned from the hardest hit area. After introducing some local situations, she pointed out that Chongqing is one of the four major stoves in China, and there has always been a saying of "nine droughts in ten years". Similar to this year's extreme high temperature and dry weather, there have been in previous years, and there have been high temperature records in history. For example, 1992 and 1994 both recorded temperatures exceeding 40℃. It's just that this year is the worst in scope and duration in 50 years.

She also believes that the major climate and environmental impact is the main cause of this disaster, and she added that "the rapid urbanization in Chongqing in recent years has intensified the urban thermal effect, which will not have a great impact on the whole climate, but the change of the underlying surface in a large area, that is, a large number of green vegetation floors are replaced by concrete, makes the heat energy generated by solar radiation unable to be quickly absorbed and diffused, and Chongqing is located in a basin with special terrain, which further aggravates this continuous high temperature. Gog also pointed out that "Chongqing's water conservancy facilities are insufficient, and there is no water conservancy irrigation project like Dujiangyan. The impact of drought caused by continuous high temperature is more prominent and serious."

The hot and dry weather will last until the end of the month.

Since the summer of this year, people in the disaster areas of Chongqing and Sichuan have faced scorching sun, brown plants, cracked land, and even draught difficulties in some areas. The party, the government and the people of the whole country are worried about the people of Chongqing and Sichuan under the heat wave. When will the persistent high temperature and drought be alleviated? The answer given by Qiao Lin, deputy director of the weather forecasting office of the Central Meteorological Observatory, is not optimistic.

Qiao Lin first introduced the weather in Chongqing, Sichuan and other areas in detail in the past month. Statistics show that from July 18 to August 18, the daily temperature in Chongqing was above 35℃, and the highest temperature in Chongqing on August 16 hit the highest value this year, breaking the historical record, reaching 43.0℃, exceeding1953 August 65438+. In addition, Fuling reached 43.5℃. Talking about the reasons, Deputy Director Qiao Lin also thinks that "the high water temperature in the western Pacific this year led to the strong subtropical high to the west and the weak cold air in the north, resulting in the decrease of precipitation and the increase of evaporation, which is the main reason for this large-scale high temperature and drought".

Regarding the weather conditions in Chongqing and Sichuan in the future, Qiao Lin said: "The Central Meteorological Observatory predicts that there will be showers or thunderstorms in eastern Tibet, western Sichuan Plateau, western Sichuan Basin and most parts of Yunnan in the next four days, and the local drought can be alleviated. However, the high temperature and drought in the eastern Sichuan Basin and most of Chongqing will continue. After August 2 1, precipitation may increase in the eastern Sichuan Basin and most of Chongqing, which can partially alleviate the drought in Sichuan Basin and Chongqing. " Qiao Lin emphasized looseness, not looseness. "By September, with the weakening of subtropical high and the enhancement and activity of cold air, the rainfall in Sichuan Basin and Chongqing will further increase and the drought will be alleviated."

According to the forecast of the Central Meteorological Observatory, the hot and dry weather in Chongqing and Sichuan will continue for some time. In the case of continuous high temperature and dry weather, the work of drought relief cannot be relaxed, and we must continue to work hard. Qiao Lin particularly reminded that we should actively do a good job in heatstroke prevention and cooling, and pay attention to avoiding the adverse effects of high temperature and drought on human body. At the same time, because bacteria are easier to reproduce in high temperature environment, special attention should be paid to the hygiene of drinking water sources.

Chain connection

■ Atmospheric circulation: generally refers to the comprehensive performance of various stable air flows in the earth's atmosphere. The reason why the air on the earth flows is because the solar radiation received by the earth's surface is uneven, which leads to the formation of different pressure zones on the earth's surface. Due to the air pressure difference caused by different air pressure levels in different places, air flows. Atmospheric circulation constitutes the basic situation of global atmospheric operation and is the driving force of global climate characteristics and large-scale weather situation. The basic factors controlling atmospheric circulation are solar radiation, friction on the earth's surface, land and sea distribution and topography. The main manifestations of atmospheric circulation are: global east-west wind belt, three-circle circulation, stable distribution of average trough, planetary high-altitude jet, great disturbance of westerly wind belt, and the distribution of world climate belt.

Basic features of climate in China: A country's climate mainly depends on its geographical location and environment. First of all, China is located in the southeast of Eurasia, the largest continent in the world, near the Pacific Ocean, the largest ocean in the world. Due to the difference of thermal properties between ocean and land and the seasonal variation of solar radiation, the seasonal variation of air pressure between ocean and land in winter and summer is caused. In summer, the mainland forms a low pressure and the ocean forms a high pressure; In winter, on the contrary, the continental air pressure is high and the ocean air pressure is low, so northwest wind prevails in winter and southeast wind prevails in summer in China. The winter wind comes from the high latitude inland, so it is cold and dry; The summer monsoon comes from the southern ocean, bringing warm and humid air to the mainland and forming precipitation. Therefore, the monsoon climate features of hot Leng Xia in winter, dry winter and rainy summer are formed. Secondly, the northwest of China is far from the ocean, and it is the hinterland of Eurasia, with obvious continental climate characteristics and large annual and daily temperature differences. In addition, due to China's vast territory and complex terrain, China's climate also has the characteristics of diverse climate types, abundant climate resources and more climate disasters.