[Process study on hysteresis of vegetation cover influencing sand-dust events].
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.
Xu
Xing-Kui
XK
International Center for Climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. xkxu@mail.iap.ac.cn
Wang
Xiao-Tao
XT
Zhang
Feng
F
D000393:Air Pollutants / Q000032:analysis*; D002681:China; D004391:Dust / Q000032:analysis*; D004784:Environmental Monitoring; D010316:Particle Size; D063245:Plant Development; D012621:Seasons; D012822:Silicon Dioxide / Q000032:analysis*; D014887:Weather; D014919:Wind
D000393:Air Pollutants; D004391:Dust; D012822:Silicon Dioxide