| With the global warming,the frequency and intensity of extreme weather events are increasing.Heavy snowstorm is one of the extreme weather events,and it is also a common disastrous weather in winter and spring in northern China.Heilongjiang Province is located in the northeast of China,where winter is long and cold.Heavy snowstorms occur frequently,and the snow or ice is a serious threat to the safety of people’s lives and property.Based on the average daily temperature and precipitation data of 63 meteorological stations in Heilongjiang Province between 1961 and 2017,and the reanalysis data of NECP,and the monthly atmospheric circulation index,the heavy snowstorm weather and its variation characteristics and the atmospheric circulation mechanism,are comprehensively analyzed by using trend analysis,catastrophic test,variance analysis,correlation coefficient analysis and so on.The conclusions are as follows:(1)From 1961 to 2017,the snowfall and snow days in Heilongjiang province showed a significant increasing trend,both of which had a sudden change in 2004,and there were significant differences before and after the sudden change of temperature in 1987.In terms of spatial variation,the snowfall and snow days decreased from east to west,while in spatial variation,the snowfall and snow days showed a consistent trend,showing a significant increasing trend in the northeast and southwest.The increasing trend in the south and north is not obvious.From 1961 to 2017,there was no significant advance or postponement trend in the first and final days of snowfall in Heilongjiang Province.The first and final days of snowfall began to change in 1994 and 1991 respectively,and there was no significant difference before and after the sudden change of temperature in 1987.The spatial distribution of the first day of snowfall shows the characteristics of late in the west and early in the middle and north.The most obvious spatial change is in Harbin,and there is no obvious trend of advance or postponement in most other areas.The spatial distribution of snowfall throughout the day showed the spatial distribution characteristics of late in the east and west,and early in the central and northern parts.The most obvious spatial change was located in Jiamusi City,and there was no obvious trend of early or late in most other areas.(2)The surface circulation situation of heavy snow weather in Heilongjiang from1961 to 2017 is mainly divided into Mongolia cyclone type,Japan Sea low pressure type,Baikal Lake low pressure type,low pressure development type,inverted trough type,low trough type,Jianghuai cyclone type,Yellow River cyclone type and other types.Mongolia cyclone type and Sea of Japan low pressure type are the main types.From 1961 to 2017,the occurrence frequency of Mongolia cyclone type and Baikal Lake low pressure type showed a significant increasing trend,while the other surface weather systems did not significantly increase or decrease;among them,the Mongolia cyclone type had a sudden change in 2014,and the rest of the surface weather system had no abrupt characteristics.There was no significant difference in the occurrence times of each surface weather system before and after the sudden change of temperature in 1987.The statistical intensities of Mongolia cyclone,Sea of Japan low pressure,Lake Baikal low pressure,low pressure development,Jianghuai cyclone and Yellow River cyclone have no significant increasing or decreasing trend from 1961 to 2017.Among them,the intensity of Mongolia cyclone and Lake Baikal low pressure abruptly changed from 1967 to 2005,and there was no abrupt intersection in the rest of the surface weather system.There was no significant difference in the intensity of the above surface weather system before and after the sudden change of temperature in 1987.According to the snowfall area,the lowpressure snowfall areas of Mongolia cyclone and Baikal Lake are mainly located in the east,north-central,west-central and north-west of Heilongjiang,while the low-pressure and inverted trough snowfall areas in the Sea of Japan are mainly in the east and southeast.Low-pressure development and Yellow River cyclone snowfall areas are mainly located in the east and south,and low-trough snowfall areas are mainly in the south.Jianghuai cyclone and other types of snowfall are mainly located in the southeast.(3)According to the snowfall,the accumulated snowfall of Mongolia cyclone type is the most,followed by Japan Sea low pressure type,followed by Baikal Lake low pressure type,Jianghuai cyclone type,low pressure development type,inverted trough type,low trough type,Yellow River cyclone type and other types.According to the number of snow days,the cumulative snow days of Mongolia cyclone type is the most,followed by Japan Sea low pressure type,followed by Baikal Lake low pressure type,low pressure development type,inverted trough type,Jianghuai cyclone type,low trough type,Yellow River cyclone type and other types.The spatial distribution of snow days of each surface weather system is basically consistent with its snowfall area.(4)The main atmospheric circulation indexes that affect the snowfall in Heilongjiang Province are subtropical high and polar vortex.The snowfall in Heilongjiang Province has a positive correlation with the subtropical high and a negative correlation with the polar vortex.Compared with the subtropical high,the area and intensity of the polar vortex in the Northern Hemisphere,the area and intensity of the polar vortex in Asia and the intensity of the Pacific polar vortex are the key atmospheric circulation indexes that affect the heavy snowstorm in Heilongjiang Province.The main atmospheric circulation indexes that affect the snow days in Heilongjiang Province are subtropical high and polar vortex.The snow days in Heilongjiang Province has a positive correlation with the subtropical high and a negative correlation with the polar vortex.The polar vortex area in Asia is the key atmospheric circulation index affecting the snow days in Heilongjiang Province.Generally speaking,the area and intensity of the polar vortex in the Northern Hemisphere,the area and intensity of the polar vortex in Asia and the intensity of the Pacific polar vortex are the key atmospheric circulation indexes that affect the snow and snow days in Heilongjiang Province. |
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