The Spatial and Temporal Distribution of Rain-On-Snow Events and Their Driving Factors in China

Abstract

Rain-on-snow (ROS) events are energy exchange phenomena produced by the joint action of rainfall and snow, which can trigger secondary disasters such as snowmelt floods and avalanches. China has an extensive snow-covered area, but research on ROS events in the country is limited to short time scales and is largely focused on Northwest China. Using the observation data of snow depth, precipitation, and temperature from 191 ground-based meteorological stations, we analysed the temporal and spatial characteristics of ROS events from 1960 to 2013 and revealed the influencing factors of ROS events in China. In addition, we also classified the intensity of ROS events and explored the characteristics of ROS intensity in China. The results show that the ROS days and snow surface rainfall in China have increased significantly over the past 53 years. The ROS events in China are mainly concentrated in the southeastern part of the Qinghai-Tibet area, the northern part of the Xinjiang area, the northeastern part of Northeast China and Inner Mongolia, and in the transition zone between North China and South China. Of these areas, the Qinghai-Tibet region has the highest occurrence, with a frequency of up to 3.0 days/year. In North China and Qinghai-Tibet areas, the increase in the frequency of ROS events is the most dramatic, with the average annual increase rate reaching 0.024 days/year. The main factor impacting ROS days is snowfall in Northeast China and Inner Mongolia, rainfall days in North China, and snow cover days in Xinjiang, the Qinghai-Tibet region, and South China. ROS events in China are predominantly low intensity, with more extreme and high-intensity ROS events in South China.