Xu Xing-Kui, Wang Xiao-Tao, Zhang Feng
International Center for Climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
Huan Jing Ke Xue. 2009 Feb 15;30(2):322-7.
Data analysis from satellite and weather stations during 1982-2000 shows nonlinear relationship between vegetation cover and sand-dust events is present in most part of China. Vegetation cover ratio in summer can impact significantly on the frequency of sand-dust storms from winter to spring in the source regions of sand-dust events. It is not quite clear about the hysteresis that vegetation cover in summer influence sand-dust events during winter and spring. A quasi-geostrophic barotropic model is used under the condition of 3 magnitude of frictional coefficient to investigate the cause of the hysteresis. Wind velocity shows a greatest decline at 90% during 72 h as initial wind velocity is 10 m/s for magnitude of frictional coefficient between atmosphere and water surface, greatest decline at 100% during 18 h for magnitude of frictional coefficient between atmosphere and bare soil and a 100% reduction of wind speed during 1 h for magnitude of frictional coefficient between atmosphere and vegetation cover. Observation and simulation prove that residual root and stem from summervegetation are one of factors to influence sand-dust events happened during winter and spring. Air inhibition from residual root and stem is a most important reason for hysteresis that vegetation cover influence sand-dust events.
1982 - 2000年期间来自卫星和气象站的数据分析表明，中国大部分地区植被覆盖与沙尘事件之间存在非线性关系。夏季植被覆盖率对沙尘事件源区冬春季节沙尘暴的发生频率有显著影响。夏季植被覆盖对冬春季节沙尘事件的滞后影响尚不清楚。在摩擦系数为3的条件下，使用准地转正压模式研究这种滞后现象的成因。对于大气与水面之间的摩擦系数，当初始风速为10米/秒时，风速在72小时内最大降幅为90%；对于大气与裸土之间的摩擦系数，风速在18小时内最大降幅为100%；对于大气与植被覆盖之间的摩擦系数，风速在1小时内降低100%。观测和模拟证明，夏季植被的残根和残茎是影响冬春季节沙尘事件发生的因素之一。残根和残茎对气流的抑制作用是植被覆盖影响沙尘事件出现滞后现象的最重要原因。
