Spatial and Temporal Trends of Wind Speed on the Loess Plateau during 1957- 2009
An analysis of spatial and temporal trends of mean wind speed arid maximum wind speed during 1957 - 2009 was performed on the Loess Plateau based on the monthly observed wind speed data at 88 meteorological stations. The cumulative departure analysis, a five-year moving average and the nonparametrie methods of Mann-Kendall test, were used for data analysis. Results indicated that: 1 ) The annual mean wind speed( 1957 -2009)was 2.36 m/s on the Loess Plateau, an- nual mean wind speeds of water erosion region, wind-water erosion crisscross region and wind erosion region were respectively 2.36 m/s, 2. 17 m/s and 2.60 m/s, and the mean wind speeds respectively decreased at the rate of - 0. 0084 m ·s-1·a-1 - 0. 0094 m ·s-1·a-1 and -0. 0188 m·s-1 ·a-1 , and respectively showed a significant decreasing trend ( P 〈 0. 001 ). And on the seasonal scale, the contribution rates of spring and winter for an- nual wind speed were higher, summer and autumn were lower. For annual mean wind speeds in the three regions, the change point of the decreasing trend was in 1981, and after the 1970s, the wind speed decreased significantly. 2 ) The reason why the mean annual wind speed decreased significantly is that the decreasing of the frequency of the daily maximum wind speed with a scale ≥5. The frequency of the gale on the Loess Plateau showed a significant decreasing trend from the 1970s to the 2000s, the magni- tude of decrease is the greatest in wind erosion region, by over 10%. By the 2000s, the frequen- cy of gale in most stations on the Loess Plateau is 〈 2%. 3 ) In most parts of wind-water erosion crisscross region and the wind erosion region, the number of gale days is more but it is less in the water erosion region and the east of the Loess Plat- eau. According to the annual mean frequency of gale days in the Loess Plateau, four sub-regions can be divided. They are fewer gale region ( 〈 10 d), more gale region (10-50 d), much more gale region (50 -100 d) and frequent region ( 〉 100 d). Most parts of the Loess Plateau fall into the more gale region, and then fewer gale region and non-freguent region. From the 1970s to the 1990s, most parts of wind erosion region and wind-water erosion crisscross region belong to much more gale region. The Baotou and Zhongning stations belong to more gale region. After the year 2000, most parts of the Loess Plateau turn to the fewer gale region.
mean wind speedmaximum wind speedthe Loess Plateau
NETL
NSTL
万方数据
维普
