What is the temporal and spatial distribution of rain?

This special weather, rime, mainly appears in mountainous areas and lake areas. In most parts of China, rainfall occurs from February 6th to March the following year. The distribution of annual average rainy days in China is characterized by more in the south and less in the north (there is little low temperature near zero in South China because of warm winter, so there is neither hail nor rainy days); There are many wet areas and few dry areas (especially in mountainous areas). The average annual rainy days of almost all stations in China are more than 20 ~ 30 days, but the average annual rainy days of most stations in plain areas are less than 5 days.

Under normal circumstances, the onset time of rime is more than one month from early June to early February in 5438, with the characteristics of early in the north, late in the south, early in the mountains and late in the plains, while the end date is just the opposite. In mountainous areas with higher terrain, the rime starts early and ends late, and the rime period is prolonged. For example, in Guangmingding, Huangshan Mountain in southern Anhui, the rainy season generally begins in early October of 165438+ and ends in early April of the following year, lasting for five months. According to the relevant figures, the rainy weather in Jianghuai area usually occurs once every 2 ~ 3 years in Huaibei area and once every 7 ~ 8 years in Huainan area. If you are in a mountainous area, there will be a big difference between the valley and the top of the mountain. In some low-lying areas in mountainous areas, it seldom rains, while in high-altitude areas in mountainous areas, it rains almost every year.

In 1960s, there was no snowstorm in Guangzhou, and the days in Shanghai, Beijing and Harbin were only 0. 1, 0.7 and 0.5 respectively. The meteorological station with the most rainy days in China is Emei Mountain Meteorological Station, with an average of 1, 4 1.3 days (maximum year 1.67 days), followed by Jinfo Mountain with 70.2 days (maximum year 93 days) and Lvcong Slope in Badong, Hubei Province with 6 1.5 days (maximum) The rainfall in the north is less and not serious, and it is even less in arid areas. Huajialing, Huashan and Changbai Mountain Tianchi, commonly known in Gansu Province, have frequent rainy days in the north. Their annual average rainy days are 29.6 days, 19.8 days and 18.5 days respectively, and most of them are also high mountain stations.

In winter, the rainy season in the north is more frequent, the winter is cold and the spring and autumn are warm. For example, the rainy season at Tianchi weather station in Changbai Mountain is concentrated in May, with an average of 5.7 days, followed by September, with an average of 3.5 days. In winter, there is no rainy season in 65438+February-March due to the low temperature. In the south, it is colder in winter. For example, at Emei Mountain Meteorological Station, the average rainy days in June 5438+February reached 26.4 days, and there were also 24.6 days in June 5438+ 10. Even in the individual years of 65438+February, 65438+ 10 and March, there are rainy days every day.

The harm caused by rain has a lot to do with its duration. There was a snowstorm in Shanghai1957 65438+1October 15 to 16, lasting 30 hours and 09 minutes. The longest continuous rainy season in Beijing is 30 hours and 42 minutes, which occurs in 65438+March 1 ~ 20957. The longest duration of Harbin is 28 hours and 29 minutes, which occurs in June 1956, June18 ~ June 19. The longest continuous rainy season in China also occurred in Emei Mountain, from1969165438+10/5 to 65438+ 1970 on March 28th, that is, it lasted for 3 198. Followed by Hengshan Nanyue 1370 hours and 57 minutes (197612.24 ~1977 February19), the third place occurred in Xuefeng Mountain, Hunan Province (1/kloc-0)

The diameter of rime ice is usually 40 ~ 70 mm, and some hundreds of mm. The largest diameter of rime ice in China appears in Nanyue, Hengshan, reaching 1, 200 mm, followed by 7 1 1mm in Lvcongpo, Badong, and 648 mm in Xuefeng Mountain, Hunan.

The method for weather stations to observe the diameter of ice accumulated in the rime is: as the rime freezes, the conductor becomes thicker and thicker, but when the rime accumulates to a certain diameter, the "rime popsicle" will inevitably break gradually. At this time, the weather observer only needs to remove the remaining ice and let the rime freeze on the conductor again. If it is on a high mountain, it may have to be cleared several times or even a dozen times, and the process of rain will be over. According to the regulations of the meteorological department, the sum of the maximum diameters during each fragmentation is the maximum ice accumulation diameter in all glazing processes.

1962,165438+1On October 24th, an ice accretion occurred in Hengshan Mountain, Hunan Province, with the conductor weight per meter16872g, which was the champion in all records in China. Other records include: Xuefeng Mountain in Hunan 156 16g, Huangshan Mountain 12 148g, Lushan Mountain 5468g, Jinfo Mountain, etc. The last snowstorm occurred in Shangqiu County, Henan Province on March 5-9, 1966. The maximum diameter reached 160 cm, and the maximum ice accumulation diameter reached 1400 g/m, which was also extremely rare in the plain weather station in the 1960s.