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黄河上游宁夏-内蒙古段穿越河东沙地、乌兰布和沙漠和库布奇沙漠,大量风沙被吹入黄河,因此,迫切需要揭示宁夏-内蒙古河段沙粒起动风速的空间分布规律,从而为该区域的风沙防治工作提供理论依据。首先,应用归一化植被指数(normalized different vegetation index,NDVI)数据集计算该河段地表植被盖度、植被迎风面积指数与粗糙度。而后,通过植被迎风面积指数计算摩阻起动风速的影响函数,研究河段摩阻起动风速的空间分布。利用实测数据检验摩阻起动风速的计算方法,表明摩阻起动风速的计算方法误差较小。研究表明,研究区内风速廓线均呈对数函数的分布规律,并利用风速廓线方程计算了研究区不同下垫面(10m高度)处的起动风速,进而得到跃移沙粒起动风速的空间分布。结果显示研究区风蚀风险最大的几个区域大多临近黄河。最后,根据当年最大NDVI值与下一年风季(3月至5月)NDVI平均值之间的关系,提出利用当年最大NDVI值对下一年风季起动风速的预测方法,该研究为黄河宁夏-内蒙古段的风蚀预报提供理论支撑。
In the upper reaches of the Yellow River, the Ningxia-Inner Mongolia section traverses the Hedong sandy land, the Ulan Buh desert and the Khukuqi desert, and a large amount of aeolian sand is blown into the Yellow River. Therefore, it is urgently necessary to reveal the spatial distribution of grit-starting wind speed in the Ningxia-Inner Mongolia reach, Aeolian sand control in this area provides a theoretical basis. First, the vegetation cover, windward area index and roughness of vegetation in this reach were calculated using the normalized different vegetation index (NDVI) dataset. Then, the influence function of the wind speed of frictional resistance was calculated by the windward area index of vegetation, and the spatial distribution of frictional starting wind speed was studied. The calculated data of the frictional starting wind speed is tested by the measured data, which shows that the calculation error of frictional starting wind speed is small. The research shows that all the wind speed profiles in the study area are logarithmically distributed, and the wind speed profile equation is used to calculate the starting wind speed at different underlying surfaces (10m height) in the study area, and then the wind speed of jumping sand grains is obtained Spatial distribution. The results show that most of the areas at risk of wind erosion in the study area are mostly close to the Yellow River. Finally, based on the relationship between the maximum NDVI value in the current year and the average NDVI of the next season (March-May), a prediction method for the wind speed of the next season using the maximum NDVI value of the year is proposed. Ningxia - Inner Mongolia section of wind erosion forecast to provide theoretical support.