近60年来黄土沙漠过渡带逐日风速变化和风沙活动的时空特征

Wind is the driving force of blown sand activity and blown sand disasters. The temporal and spatial characteristics of blown sand activity can be known by studying regional wind speed change, which might provide the scientific basis to reduce blown sand disasters. In this paper, we first defined the threshold value of sand-driving wind and the strong wind, which likely control the blown sand activity. Then, based on daily wind speed data from twelve weather stations in the loess-desert transition zone between 1954 and 2011, wind speed change was analyzed by using statistical analysis software. The following results can be indicated from this study: 1) The prevailing wind leading to the blown-sand disasters came from the Northwest. And the blown sand activity mainly occurred during February to May every year. 2) The blown sand activity likely occurred more frequently during 1957~1960, 1969~1971, 1981~1983 and 1999~2000, especially during 1957~1960. 3) From 1954 to 2011, the frequency of daily mean wind speed (DMWS) greater than sand-driving wind (≥6.0m/s) and daily maximum wind speed (DMW) (≥10.0m/s) all showed a declining trend with fluctuation. From 1970 to 2011, 80% of the total stations for the frequency of DMWS (≥6.0m/s) and DMW (≥10.0m/s) had declining linear trends (significance level P<0.001). The main reason for the long-term decreasing trend was that East Asian winter and summer monsoons weakened. 4) DMWS, the frequency of DMWS (≥6.0m/s) and DMW (≥10.0m/s) display a gradual reduction from the desert to the loess area. From 1978, DMWS, Frequency of DMWS (≥6.0m/s) and DMW (≥10.0m/s) dramatically decreased in Jingtai and Xiji. Since 1984, DMWS and Frequency of DMWS (≥6.0m/s) have obviously fallen in most of the area (83%). These events are probably attributed to human activity, vegetation and ecological change.