Climatic characteristics and circulation type of snowstorm in the northern Tibet in the past 31 years
YU Yan-qun, XIONG Qiu-fen, Zuoma, De Ji Baizhen
2020, 59(17):
31-37.
doi:10.14088/j.cnki.issn0439-8114.2020.17.007
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Using the daily precipitation data, weather phenomena, and snow accumulation data of observatories in northern Tibet from 1988 to 2018, the climatic characteristics of snowstorms in the northern Tibet were analyzed by methods of meteorological diagnosis and wavelet analysis. The results showed that the spatial distribution of the number of snowstorm days, snow amount, maximum snow depth and annually average snow depth in the northern Tibet in the past 31 years generally showed a trend of more in the east than in the west, mainly concentrated in the east, with a significant regional difference. The number of the snowstorm and the amount of snow in the last 31 years showed a decreasing trend. The turning year of which was 2002, it was a snowy period before 2002, and it was a period of few snowfalls after 2002. After the 2000s, the number of snowstorms decreased at a rate of 2 stops every 10 years, and the amount of snowstorms decreased at a rate of 2.4 mm per 10 years. The season distribution of the snowstorm was bimodal, with the largest peaks occurring in April and May. The number of snowstorm days showed a periodic change of 3a, 5a, and 10a. Using NCEP to analyze the height field and wind field of the data, the circulation and impact system of snowstorm weather were summarized and concluded. The circulation pattern of the regional snowstorm in north Tibet could be divided into 4 types, namely, the Indian low-pressure type, the north ridge & south trough type, stepped trough type, and Balkhash lake low trough type. The southern branch trough, tropical depression, low vortex-shear and plateau trough were the main influence systems of the snowstorm in the northern Tibet.
