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利用黄土高原风蚀和风水蚀复合区30个气象站1961—2010年的观测资料,根据联合国粮农组织给出的风蚀气候因子指数(C值)的计算公式和线性趋势法、Pettitt变点检测、Morlet小波分析等方法,研究风速的空间分布、时空变化、突变特征和周期特性及其对C值的影响。结果表明:①该区多年平均风速为2.2 m.s-1,内蒙古和宁夏境内的部分地区风速较大,陕北、晋西北、陇东和青海部分地区较小。近50 a来风速整体呈显著减小趋势,1970s风速最大,2000s最小。②年尺度83%的站点风速发生了突变,区域整体突变发生于1982年,四季风速突变时间与年尺度基本一致。③近50 a风速存在3次交替变化,1961—1977年和1995—2010年偏大,而1977—1995年偏小,季节尺度上也发现了类似的现象,未来一段时间内该地区风速仍然偏小。④该区多年平均C值的空间分布格局和时空变化趋势与风速较为一致,整体也呈现出显著减小趋势。⑤C值与相对湿度和降水量呈负相关关系,与潜在蒸发量、干旱指数和风速呈正相关关系。风力增强(风速增加)和干旱加剧对于风蚀起到促进作用;温度上升及其造成的蒸发量增大也有助于风蚀的形成。
Based on the observational data from 30 weather stations in 30 weather stations in the composite wind and water erosion area of the Loess Plateau from 1961 to 2010, according to the calculation formula and linear trend method of Wind Erosion Climatic Factor Index (C value) given by the UN Food and Agriculture Organization, the Pettitt change point detection, Morlet Wavelet analysis and other methods to study the spatial distribution of wind speed, spatial and temporal changes, mutation characteristics and periodic characteristics and its impact on C values. The results show that: ① The average annual wind speed in this area is 2.2 m · s-1, while the wind speed is higher in some areas in Inner Mongolia and Ningxia, while the areas in northern Shaanxi, western Shanxi, eastern Gansu and Qinghai are smaller. In the recent 50 years, the overall wind speed showed a significant decreasing trend, with the largest wind speed in 1970s and the smallest in 2000s. (2) The site wind speed of 83% of the annual scale changed suddenly. The overall regional mutation occurred in 1982, and the time of the sudden change of the four-season wind speed was basically consistent with the annual scale. ③ There were three alternations of wind speed in the past 50 years, which were larger in 1961-1977 and 1995-2010 than in 1977-1995 and similar in seasonal scale. In the future, the wind speed in this area was still partial small. (4) The spatial distribution pattern, spatio-temporal change trend and wind speed of the average C value in the area for many years are consistent, and the overall trend also shows a significant decrease. ⑤C value has a negative correlation with relative humidity and precipitation, and has a positive correlation with potential evaporation, drought index and wind speed. Increased wind (increased wind speed) and increased drought contribute to wind erosion; rising temperatures and the resulting increase in evaporation also contribute to wind erosion.