午夜欧美大片免费观看,欧美激情综合五月色丁香,亚洲日本在线视频观看,午夜精品福利在线

Based on the meteorological surface observation data from 1999 to 2019, the evolution characteristics of sand-dust weather frequency in the main sand sources in East Asia (Mongolia, Xinjiang and Inner Mongolia) and the downstream areas in China are analyzed. The results show that the most severe sand-dust weather is in Mongolia, which shows an increasing trend, with the highest numbers of sand, sandstorm and strong sandstorm days in all of the regions. The frequency of sand-dust weather is reduced in China and increases rapidly in Xinjiang; moreover, it obviously reduces in Inner Mongolia and the downstream area. In Xinjiang, the frequency of dust weather is the highest, and shows an obvious increasing trend with linear tendency in the past 21 years. In Inner Mongolia, the sand blowing weather occure more frequently than other sand-dust weather, while the strong sandstorm is relatively less. In addition, all kinds of sand-dust weather are reduced. In the downstream area of China, dust and sand weather occurs frequently and decreases slightly. At the same time, sandstorms and strong sandstorms rarely occur. According to the interannual variations of sand-dust weather in China, 1999-2004 is the peak period, and 2005-2019 is obviously reduced, with 2010-2014 showing the fastest decline. The contribution of the sand sources to the total number of sanddust weather days in China has increased continuously, from 39% at the beginning of 2000 to 71% after 2015. As sand sources, Mongolia’s contribution to sand-dust weather has increased, while Inner Mongolia’s has weakened. There is a significant reduction in the number of severe dust events that can affect and spread to the downstream areas of China and other downstream countries.