Study On The Characteristics Of Wind Speed Variation And Its Influence Factors In Hexi Region During The Last 40 Years

On the basis of a large number of related literature at home and abroad, combining the characteristics of the gale in Hexi area and adopting the technical route which combines the theoretical analysis with numerical simulation, the gale change characteristics and influence factors were studied, and the main results of the research were:1.Through the analysis of the average wind speed change and the cause and process of the gale combining atmospheric circulation with terrain in the Hexi corridor, it can be obtained the conclusions as follows: in the Hexi corridor, the wind speed in spring reaches the maximum throughout the year, the autumn comes second; the average wind speed has descended in the range of 1.5m/s to 3.0m/s,the change presenting decrease trend in 0.5m/s·10a.The wind direction is mainly the northwest and southeast along the corridor direction. The cause of gale is mainly influenced by cold front of winter half year, mostly in winter and spring, autumn is the least; the weather and climate are affected by the east Asian monsoon in a certain extent. The geographical conditions are the main factors which influence the acceleration and deceleration in wind moving, mainly have: transit, flow around, stop, cut, turn over the mountain.2.Applying the wavelet cycle analysis and Mann-Kendall mutation test to study the change characteristics of the gale in the Hexi corridor, it can be obtained the follow conclusions: the gale change trends become balanced in Mazongshan, Dunhuang, Jinta, Dingxin, Gaotai, Shandan, Yongchang and Wushaoling weather stations,and the linear regression coefficients are less than 0.05;the change trend of the others weather stations tend to decrease, and the linear regression coefficients are greater than 0.15.The maximum wind speed present sine-varying, the primary period is 28-29 years, the secondary period is 8-12 years;from 1982 to 1990,there had a mutation, the maximum wind speed declined sharply after the mutation. Compared the wind speed of weather stations with the observational data of wind towers, it can be obtained that the wind speed difference is equal or greater than 3.75m/s and there are significant differences between the two.3.Through the analysis of the weather stations environments and the representative areas, it can be obtained the following conclusions: there are mainly the houses which are higher than the observation points(10m) and factories around the weather stations, blocking the wind speed; in cities, the intense population increase the lowest temperature, directly reducing the temperature differences and air potential energy, leading to the reduce of the wind speed.4.Trough the linear fitting of the weather stations and wind towers, the design wind speeds of weather stations were modified, the results are in good representative.5.Applying WRF model to simulate the typical process of gale, it can be obtained the following conclusions: the gale moved from west to east, the wind speed decreased quickly when the gale passed oases and cities, etc, where the underlying surface is complicated, and mainly decreased in Jiuquan and Jinta, and near Beishan of Zhangye, the speed reduced sharply when passed Gaotai and Zhangye.