新疆策勒绿洲——沙漠过渡带不同下垫面风场特征

Characteristics of Wind Filed over Different Underlying Surfaces in the Oasis-Desert Ecotone in Qira,Xinjiang

以新疆策勒2010年8月至2011年7月的气象数据为依据,运用数理统计方法,对策勒绿洲-沙漠过渡带流沙地、半固定沙地、固定沙地及绿洲内部4个下垫面的风况进行统计分析,为风场的时空差异特征和植被防风阻沙效益研究提供理论依据。结果表明:研究区4个下垫面主风向以WNW、W为主,所占频率分别为41. 43%、33. 74%。从流沙地、半固定沙地、固定沙地到绿洲内部,静风所占的频率依次为44. 30%、52. 44%、54. 29%和85. 39%,随着风速的增大,其所占频率依次减小,气温与风速均呈现同步变化的趋势。较高起沙风频率与起沙风月平均最大风速多出现在春、夏两季,6月频率最大,虽然最大值出现月份不同,但变化趋势相似。从绿洲外围向绿洲内部风向不同,且主风向所占频率减少,表明植被能削减风速并使风向变得更加分散。平均风速、起沙风频率从流沙地到绿洲内部逐渐减小(少)。月平均风速、气温之间呈显著相关性,且从流沙地前缘到绿洲内部相关性逐渐减弱。植被类型、植被覆盖度和地形等是影响不同下垫面风场特征的主要因素。

Based on the meteorological data in Qira County,Xinjiang from August 2010 to July 2011,the statistical analysis method was used to analyze the wind regime over four different underlying surfaces including the shifting sandy land,semi-fixed sandy land,fixed sandy land in oasis-desert ecotone and oasis in Qira. The study results could provide a theoretical basis for further studying the spatial and temporal characteristics of wind field and the effects of vegetation against wind and drifting sand. The results showed that the wind directions in the study area were dominated by WNW and W,and their frequencies were 41. 43% and 33. 74% respectively. The calm frequencies over the shifting sandy land,semi-fixed sandy land,fixed sandy land and oasis accounted for 44. 30%,52. 44%,54. 29% and 85. 39% respectively,and these frequencies were decreased gradually with the increase of wind speed. The changes of air temperature and wind speed were in a synchronous trend. The high sand-driving wind frequency and the monthly-averaged maximum wind speed occurred mostly in spring and summer,especially in June. Although the maximum values occurred in different months,the change trend was similar. From the periphery to the central area of the oasis,the wind direction and the frequency of prevailing wind direction were decreased,which indicated that the vegetation could reduce wind speed and disperse wind direction. The average wind speed and sand-driving wind frequency were gradually decreased from the shifting sandy land to the central area of the oasis. There was a significant correlation between the monthly-averaged air temperature and monthly-averaged wind speed,and the correlation was gradually decreased from the shifting sandy land to the central area of the oasis. Vegetation types,vegetation coverage and topography are the main factors affecting the variation of wind fields over the different underlying surfaces.