Abstract:

Precipitation is a basic element of climate.Different precipitation types play different roles in the material and energy cycles of the land surface.As the planet warms,a climatic shift from warmdry to warmhumid has taken place in the northwest region of China,especially in Xinjiang Province.The Tianshan Mountains function as the climatic dividing line between South Xinjiang and North Xinjiang.This area is very important to the sustainable development of the economy of Xinjiang,and to the central and western regions of China,more broadly.In response to global warming,precipitation types have begun to change in the Tianshan Mountains,and tracking these changes in the number of days with different precipitation types is an important step.We gathered daily precipitation data from 35 meteorological stations in the Tianshan Mountains from 1980 to 2017.We separated three main precipitation types (rain,snow,and sleet) and identified them using a parameterization scheme which performed better than other normal schemes.The spatial distribution of days with different precipitation types in the Tianshan Mountains was interpolated using the Inverse Distance Weighted method provided by ArcGIS 10.2.The linear trend rate was used to establish the trend in the days of precipitation types.Combining the MannKendall mutation test with the moving t test method,we isolated an abrupt change in the number of days with different precipitation types.Finally,we used morlet wavelet analysis to study the periodicity of the days of different precipitation types in the Tianshan Mountains.Our results showed that the precipitation days were relatively consistent with the amount of precipitation.(1) In terms of spatial patterns,days of precipitation,and days of rainfall were more common in the north and west than in the south and east.“ Snowfall occurred on more days in the north and fewer in the south.” The increasing trend of days of precipitation in the north was more pronounced than it was in the south,as was the faster increasing trend in the west.The number of days of rainfall generally increased,while both snowfall and sleet became less common in most of the study areas.(2) Most precipitation in the Tianshan Mountains occurred during AprilSeptember,and it mainly comprised rainfall.Most snowfall occurred during NovemberMarch of the following year.All three forms of precipitation coexisted in March and April,and in October and November.Over the last 38 years,the number of days with precipitation,rain,and snowfall showed respective trends of gently increasing,significantly increasing,and decreasing.The changes in the number of days of sleet were not significant.(3) An abrupt inflection point occurred in the number of days with precipitation in the Tianshan Mountains was identified in around 1986.In addition,rainy days experienced an indistinctive mutation in 1986 and 1995; snow in 2012; and sleet in 1985 and 2004.(4) All four precipitation types experienced a fluctuating cycle change of about 10 years.Finally,the fluctuation cycles of the 18-22-year scale for precipitation,rain,and sleet were also obvious.

Key words: Tianshan Mountains')">

Tianshan Mountains, precipitation types, spatiotemporal distribution