Abstract:

Based on the observational data of sand-dust events at 72 meteorological stations and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data in Northeast China from 1961 to 2016, the spatiotemporal characteristics, climatic trends and abrupt change characteristics of sand-dust events in spring over Northeast China were analyzed, and the effect of atmospheric circulation on frequency of sand-dust events was investigated. The results showed that the number of  sand-dust events is greater  in the western region of northeast China than the eastern region and in plain areas than  mountainous area. The sand- dust events, blowing sand events, sandstorm events, and floating dust events in springs from 1961 to 2016 in Northeast China decrease obviously. The number of sand-dust days change abruptly around 1985. After 1985, the mean number of sand-dust days  is 3 d less than before. Sand-dust events in the Northeast China occur more frequently for the following conditions: firstly, when the geopotential height anomalies at 500 hPa abovwe the Baikal Lake and most parts of Northeast China are negative and those nearby the Balkhash Lake are positive, secondly, the occupation  area of Siberian High is larger and its location shifts eastward, and thirdly, the air pressure in the Northwest China and North China is lower than the normal conditions. However, sand-dust events in the Northeast China occur less frequently when the geopotential height anomalies at the Baikal Lake and in most parts of mainland in China are positive with the center of positive anomaly area near the Baikal Lake, the surface area of the Siberian High is smaller and its location shits  westward, and the air pressure in the most northern regions of China is higher than normal. The reduction of the polar vortex area in the northern hemisphere and in Asia and the decrease in polar vortex intensity in the past 56 years is one of the reasons for the decrease in sand-dust events during spring in Northeast China.

Key words: Northeast China, Sand-dust event, Climate change, Atmospheric circulation, Polar vortex