Relationship between shelterbelt structure and mean wind reduction

Optical porosity is the important structural feature of two-dimensional (2-D) artificial fences and narrow shelterbelts, but not for 3-D, or wide shelterbelts. To determine the important features of wide shelterbelts, we measured the mean wind speed around eight natural shelterbelts of various widths W and total area densities Ad. Our results show that the product of W and Ad, but not W or Ad alone, is useful for predicting the wind sheltering around fully 3-D shelterbelts. There was a strong negative correlation (p < 0.01) between W × Ad and the minimum relative wind speed. Also, the shelter distance generally increased with increasing W × Ad.