What is the time and distribution of rime?

Rainfall usually occurs from the first ten days of 1 to the first and middle days of February, lasting more than 1 month, with the characteristics of early in the north and late in the south, early in the mountains and late in the plains, but the end of the day 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, the rainy season in Guangmingding of Huangshan Mountain in southern Anhui usually starts from the first ten days of 165438+ 10 and ends in the first ten days of 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. There is almost no rainstorm in some valleys in mountainous areas, while there is rainstorm in mountainous areas almost every year.

Rain stops are more common in mountainous areas and lake areas. In most parts of China, rainfall occurred from February 65438 to March the following year. The distribution characteristics of the annual average number of rime 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 is neither hail nor rime in this area, while there are more rime days in humid areas and fewer rime days in arid areas (especially mountains). Almost all the stations with an average rainy day of 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.

The rainy season often occurs in the warmer spring and autumn seasons in the northern region where winter is cold. For example, the rainy season 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. In winter, there is no rainy day in 65438-February-March due to the low temperature. 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 diameter of rime ice is generally 40 ~ 70 mm, and some are several hundred mm. In China, the diameter of rime ice is Hengshan Nanyue 1200mm, followed by Badong Green Congpo 7 1 1mm and Xuefeng Mountain in Hunan 648 mm..

There is a clear difference between rime and surface water icing. Rime freezes in the process of falling, which can immediately attach to the exposed surface of the object without loss, forming an increasingly thick solid ice layer, thus increasing the load of the object. Severe rime will crush branches, crops, wires and houses, and hinder traffic.

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 major diameters of the cloud during each fragmentation is the major ice accumulation diameter of the cloud during the whole rainy season.