Influence of shelterbelt combinations on characteristics of wind speed distribution in ground surface layer

In order to understand the effect of shelterbelt combinations on ground wind speeds,the characteristics of wind speed distribution was investigated by measuring wind speeds at various points in space.The study results show that the two shelterbelts combined vertically can be classified as main-belt and subsidiary-belt based on the differences in wind speed reduction.The wind velocity is 6.38～7.56m/s within 0～150m area at the leeward of main shelterbelt.The wind velocity increases to 8.06～9.23m/s in the area of 200～280m from the main-belt.Comparatively,the wind speed reduction is lower near subsidiary-belt than that near main-belt,thus the influence of subsidiary-belt on wind speed and its protective effect is limited.Furthermore,an effective protection area is formed in a shelterbelt net and the wind velocity is lower in net than that in non-protected field.The exception is that the wind velocity reaches 11.0m/s as the same as that in non-protected field around 1H range at the edge of shelterbelts.The lowest wind velocity appears in the area of 4～8H from the shelterbelts inside the net.The results demonstrate that shelterbelt net has formed an effective protection area for reducing wind velocity in the farmland.