On the basis of improving the algorithm of the mixing length in and above forest canopies, a PBL numerical model including the multi-layer, heterogeneous vegetation is developed. Simulations indicate thatdifferent treatments of mixing length can make a great difference in the wind field especially for dense forest.and results fi.om the improved mixing length scheme are in better agreement with observations than thosefrom the original scheme. It may be expected that the improved mixing length scheme can lead to more rational turbulent transfer than the original one. From the sensitivity experiments, we obtain the characteristics of both wind and temperature profiles in and above plant canopies, e.g., during the daytime, a stablethermal stratitication exists near the surface in the canopies, but a neutral or slightly unstable condition appears above plant canopies. while at night the reverse situations occur; the increase of the temperature of thedense-forest case is less than that of the sparse-forest case, the windspeed is reduced within the canopy layer and the large wind shear occurs near the treetop, etc.
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机译：materialmodell没有。 72 foer Betong：Erfarenheter fran en Experimentell och Numberisk studie（material modell no.72 for concrete-Experience from a Experimental and Numerical study）。
