Temporal and spatial distribution of rime.

Rain stops are more common in mountainous areas and lake areas. In most parts of China, the rainy season occurred from February 65438 to March the following year. The distribution characteristics of annual average rainy days in China are more in the south and less in the north (however, due to the warm winter, there are few low temperatures near zero in South China, so there are neither hail nor rainy days); There are many wet areas and few dry areas (especially in mountainous areas). Almost all the stations with an average rainy day of more than 20 ~ 30 days in China are alpine stations. However, the average annual rainy days of most stations in the plain area are below 5 days.

Rainy days mostly occur from the first ten days of 1 to the first half of February, with the characteristics of early in the north, late in the south, early in the mountains and late in the plains, but the end is the opposite. In mountainous areas with higher terrain, the rime starts early and ends late, and the rime period is slightly longer. 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 statistics, the rainy weather in the Jianghuai basin occurs once every 2-3 years along the Huaihe River and once every 7-8 years in the south of Huaihe River. However, in mountainous areas, there is a big difference between valleys and mountain tops. In some valleys in mountainous areas, there is almost no rime, while in higher mountainous areas, there is almost every year.

In 1960s, there was no snowstorm in Guangzhou, and only 0. 1, 0.7 and 0.5 days appeared in Shanghai, Beijing and Harbin on average every year. The meteorological station with the most rainy days in China is Emei Mountain Meteorological Station, with an average of 14 1.3 days (maximum year 167 days), followed by Jinfo Mountain, with 70.2 days (maximum year 93 days), and the third place is Lvcongpo, Badong, Hubei Province, with 61. There is neither much nor much rain in the north, especially in arid areas. The places with the most rainy days in the north are huajialing, Huashan and Changbai Mountain Tianchi, which are commonly known in Gansu Province, with an average of 29.6 days, 19.8 days and 18.5 days respectively, and are also high mountain stations.

In the wettest season, warm spring and autumn are most common in the northern part of winter. For example, the wettest month at Tianchi weather station in Changbai Mountain is May, with an average of 5.7 days, followed by September, with an average of 3.5 days. Due to the low temperature in winter, there is no rainy day from February to March in 65438. In the south, it is colder in winter. For example, the average rainy days in Emei Mountain Meteorological Station in June 5438+February are as high as 26.4 days, and the average rainy days in June 5438+ 10 are as high as 24.6 days. Even some years, June 5438+February, June 5438+ 10, March, have rainy days every day.

The harm degree of rime is also related to its duration. In June1957+1October1May-June 16, a snowstorm occurred in Shanghai, 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+1October 15 to1March 28, 970, that is, it lasted for 3 198 hours and 54 minutes. Followed by Hengshan Nanyue 1370 hours and 57 minutes (1976 65438+February 24th ~1977 February19) and the third Xuefeng mountain in Hunan 1 192 hours and 09 minutes.

The diameter of rime ice is generally 40-70 mm, and some are several hundred mm. The largest diameter of rime ice in China appears in Nanyue, Hengshan, reaching 1, 200mm, followed by 7 1 1mm in Lvcongpo, Badong, and 648mm 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. On the high mountain, it may take several times or even a dozen times to clear it continuously before the rime process stops. 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.

1962165438+1On October 24th, an ice accretion occurred in Nanyue, Hengshan, with the conductor weight per meter 16872g, 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. On March 5-9, a snowstorm with the maximum diameter of 160 cm and the maximum ice accumulation diameter of 1400 g/m occurred in Shangqiu County, Henan Province, which was a rare record in the plain weather station in the 1960s.