Why does it always rain in Changsha?
According to the official statement, the geographical location and topography of Changsha make the climate in Changsha and even the whole central Hunan special. There are three main reasons that affect Changsha's climate: First, Changsha is located in the southeast of China and belongs to the world-famous monsoon climate zone. Affected by the monsoon, the seasonal changes are obvious, and Leng Xia is hot in winter; Second, Changsha is located in the third step of China's topography, far from the sea, with plain hills as the main terrain, and the continental climate characteristics of Leng Xia fever in winter are obvious; Thirdly, due to the ups and downs of geological times, the terrain in central Hunan where Changsha is located is high in the south and low in the north, especially there are five mountains in the south, Mufu Mountain in the east, Xuefeng Mountain in the west and Dongting Lake area in the north, which makes its terrain horseshoe-shaped and blocks the adjustment of the west wind in the East and South China Seas, making the characteristics of cold winter and summer inflammation particularly remarkable. Changsha's climate features are: Leng Xia is hot in winter, with four distinct seasons; Spring and autumn are short, winter and summer are long, which fully embodies the similarities and differences of subtropical continental monsoon climate types. Spring: The first climate feature is that the temperature rises rapidly and changes greatly. "Three points of water and heat in spring" is a well-known proverb in Changsha. From the average temperature of 10℃ in March to 22℃ in May, it rose by 12℃ in just two months, with an average monthly increase of 6-7℃. At the same time, the temperature not only rises rapidly, but also changes greatly. For example, the temperature in April, according to the statistics of 30 years, the lowest monthly average temperature is 13.6℃, and the highest is 2 1. 1℃, with a difference of nearly 8℃. Another example is 1969. On April 5th, the lowest temperature was 2.5℃, while on April 5th 10 of the same year, the highest temperature was 33.4℃, and the five-day temperature difference exceeded 30 degrees. Therefore, "chilly spring" is a common phenomenon in Changsha. Rapid temperature rise is beneficial to crop sowing, but large temperature difference brings adverse effects. The second feature of spring in Changsha is continuous rain and humid air. The average rainy days in Changsha from March to May (the daily rainfall is equal to or greater than 0. 1mm) are 52.8 days, accounting for more than 35% of the total rainy days in a year (15 1.2 days). It rains continuously for many years 15-20 days, so the precipitation from March to May accounts for the whole year. The cloudy days in these three months (the daily average total cloud amount is more than 80%) account for more than 365,438+0% of the total cloudy days in the whole year, and the relative humidity is between 83% and 84%, which is the season with the highest relative temperature in the whole year. In a word, Changsha's spring rain is famous all over the country. Summer: Changsha is famous for its long summer, which lasts for four and a half months and is the longest season in the whole year. It is also the highest temperature season in the whole year. From June to September, the ten-day average temperature is 25℃, and from late July to late August, the ten-day average temperature is above 29℃. According to records, the highest temperature measured at Tianxin Park observation field of Changsha Customs Meteorological Station on August 1934 is 43℃, which is the high temperature limit of Changsha. The highest temperature since 1949 is 40.6℃, which was measured on 1953 in August. This kind of situation is rare in China. The average daily temperature in Changsha is above 30℃ for 94 days, including 84 days in summer, and the average daily temperature is above 35℃ for as many as 1 month, mainly in August. Because Changsha is located in the Xiangjiang River Basin, with low terrain and relatively high temperature, it is steaming in the heat, so Changsha, Chongqing, Wuhan and Nanjing are also called the four furnaces in Changsha Basin. Another feature of Changsha in summer is uneven precipitation and uncertain droughts and floods. The rainstorm days in Changsha are mostly concentrated in May, June and July. During the 30 years from 195 1 to 1980, there was a total of 1 10 days in Changsha, of which May 23rd, June 29th and July 20th accounted for 65% of the total rainstorm. However, rainfall varies greatly from year to year. For example, the total average rainfall in late June was 69.8 mm, but 1969 was as high as 384.8 mm, and 1975 did not rain. For another example, the precipitation in early July was 4 1.4 mm, but it was 226.7 mm in 1.965, and there was no rain for five years. The result of uneven precipitation is bound to cause waterlogging or drought, but due to high temperature and abundant rainfall, summer in Changsha still provides favorable climatic conditions for crop growth. Autumn: Changsha is characterized by less rain and crisp autumn. Autumn and winter are dry seasons in Changsha. According to statistics, from late September to1mid-October, the average precipitation was only 23.6 mm, less than one third of that in spring. There have been many years in history when it has not rained for nearly 40 days, and the characteristics of autumn dryness are very obvious. In addition, although autumn in Changsha is short, there are many sunny days. According to statistics, the average number of sunny days with low cloud cover less than 2 in Changsha is *** 136.2 days, while from September to 1 1.5 days, accounting for one third of the annual total. During this period, the temperature is also suitable, from hot summer to cool autumn, but the temperature is slightly higher than that in spring, so Changsha folks have the reputation of "October Spring". The "golden autumn season" in Changsha not only presents the picturesque beauty of "all mountains are red and all forests are dyed", but also presents the harvest weather of "frost dew steaming thousands of trees, waves surrounding the wind shaking a continent" and "jellyfish everywhere see Miao Shuo, hut every family refers to wheat autumn", which reproduces the mature beauty everywhere. What is lacking is that autumn leaves in a hurry and winter is bleak. Winter: Changsha has no severe cold and little rainfall in winter. The average monthly temperature in winter is mostly above 5℃, and the coldest monthly average temperature is 10. 6℃, the highest is 8.6℃. Frost or freezing weather occurs when the temperature is lower than 0℃ in one day, and the average winter is only 19.9 days. Although extreme low temperature has occurred in rare cases, for example, the lowest temperature reached-1 1.3℃ on February 9 and1.5℃ on October 30. However, when the daily average temperature is -5℃, the annual average is only 1.3 days, and there is no severe cold period when the average temperature is less than 0℃. Although the winter precipitation in Changsha only accounts for 16% of the whole year, it is the month with the least precipitation in 65438+February, with an average monthly rainfall of 45.3 mm, which is more than that in Nanjing in the lower reaches of the Yangtze River (29.4 mm) and Guangzhou in the Pearl River Delta (24.7 mm), which is enough for the growth of overwintering crops. Because the rain is moderate and not too cold, the winter in Changsha is not bleak. Evergreen broad-leaved trees such as Cinnamomum camphora and Ligustrum lucidum are still lush, just as Tang Du Xunhe's poem "Boating on Xiangjiang River with Friends in Late Winter" said: "Where is the residual wax boating? At most, it is Xiaoxiang. " Changsha's climate, with four distinct seasons, includes both the exuberance of life and the struggle against nature. The ups and downs of the environment have cultivated Changsha people's pepper character and fighting spirit, which has lasted for thousands of years since human beings appeared in this land.