Studies On Characteristics And Impact Factors Of The Surface Wind Speed Changes In The Northern China

The northern China is not only rich in wind energy resources, but also the main area of the dust weather occurred. Therefore, the study of near-surface wind speed trends of climate change is urgent in theory and practice. In this paper, characteristics and impact factors of near-surface wind speed changes over the past50years in the northern China are studied by using the data of daily mean wind speed, circulation indexes and the NCEP/NCAR reanalysis data. The following are main conclusions:(1)The annual mean wind speed is between lm/s and5m/s in most regions of the northern China. Northeast China-Inner Mongolia Region, Northeastern Plateau and the Northeastern Region are the high wind speed regions. From the annual variation, we can see that the wind speed is highest in spring with the second in winter. In autumn, the wind speed is the lowest. During the last50years, wind speed presents a slow decreasing tendency with a velocity of0.15m·s-1/10a over the northern China as a whole. There is large decreasing tendency in spring, while small in summer. The climate tendency of mean wind speed is above the rate of0.1m·s’-1/10a in most regions of the northern China. The wind speed is significantly decreasing trend in Junggar basin, Northeastern Plateau, the middle part of Inner Mongolia and Northeast Plain, of which the rate are above0.2m·s-1/10a.Days, of which daily mean wind speed is less than3m/s,is increasing.(2)The spatial distribution of effective days is similar to annual mean wind speed in the northern China. The effective days is the most in spring with the second in summer. In winter, the effective days is the least. The climate tendency of effective days is at the rate of-13.6d/10a over the northern China as a whole. There is large decreasing tendency in spring, while small in winter. The climate tendency of effective days is above the rate of10-20d/10a in most regions of the northern China. The effective days are significantly decreasing trend in Junggar basin, Qaidam Basin, the middle part of Inner Mongolia and Northeast Plain, of which the rate are above20d/10a.(3)East Asian winter monsoon and summer monsoon is weakening. The weakening of vortex, the strengthening of subtropical high and the plateau pressure system have correlation with the decreasing of wind speed and effective days. (4)It has been found by analysis that the atmospheric circulation showed high in north and low in south in high latitudes of East Asia at the years with more frequency of effective days. And the trough in East Asia is strengthened. When effective days is less, the atmospheric circulation in East Asia in the high latitudes showed low in west and high in east.