Defining Indices for the Extreme Snowfall Events and Analyzing their Trends in Northern Xinjiang, China

抄録

 Northern Xinjiang (NX), China, located at middle latitude of Northern Hemisphere, has abundant snowfall and a long period of snow cover. To assess the impacts of climate change in this region and to provide scientific knowledge for the resources and contingency plans, analysis of the spatial and temporal variations in extreme snowfall events (ESEs) in NX was carried out based on five defined ESE indices in this study, i.e. days of heavy snowfall, maximum 1-day snowfall amounts, maximum 1-event snowfall amounts, maximum consecutive snowfall days, and frequency of heavy snowfall events. To reconstruct the snowfall dataset, the relationship between air temperature and snowfall events were compared, and it was found that daily minimum air temperature below 0℃ is the best indicator to select snowfall days. ESEs in NX were taking an increasing proportion in snow events, though snowfall days were decreasing. Consistent increasing trends in all ESE indices were found for the whole NX, while different changes in these ESE indices were found for subregions. With high increasing trends in these ESE indices in most of subregions, Daxigou-Xiaoquzi area and Qitai area were the hot spots for ESEs. Since these hotspots are likely to be influenced by airflow from the Arctic Ocean, the changes in Arctic Ocean and associated atmospheric circulation as a consequence of climate change might be the main reason for the detected increasing trends of the ESEs in NX.