林内穿透雨量模型研究

Studies on throughfall model in forest area

穿透雨量是林内有效雨量的主要组成部分 ,其量能占 90 %以上。由于林冠空间分布的不均匀性 ,难以对林内穿透雨量进行精确地测量。从林冠截留降雨的作用机理出发 ,在做出几个假设的基础上 ,用数学方法建立了林内穿透雨量模型 ,即 :当 P<U时 ,R=P- α W[1 - ( 1 - P/U) b+ 1] ( b>0 ,U>0 )当 P≥ U时 ,R=P- W其中 U=W( b+ 1 ) ,式中 b,W,U为模型参数 ,R为林内穿透雨量 ,P为大气降雨量 ,α为林分郁闭度。结合两个有实测资料的针叶树林分 ,又进一步介绍了模型参数的确定方法。同时将模型的计算结果与实测数据进行了对比 ,两者吻合性很好 ,验证效果是比较理想的。模型概念清晰 ,参数物理意义明确。在风速和雨强不太大的情况下 ,本模型适用于任何林分的穿透雨量的计算。然而 ,为了应用于无实测资料地区 ,尚须进一步研究模型参数与林分特征的关系。

Throughfall is an important part of effective rainfall in forest area. It accounts for more than 90% in quantity. The accurate measurements of throughfall is very difficult and also impossible because forest canopy is not well-distributed. This paper was based on some assumptions, a throughfall model in forest area was developed by mathematical way in terms of canopy interception mechanism. That is : If P<U, then R=P-αW[1-(1-P/U) b+1] (b>0,U>0,W>0) If P≥U, then R=P-W Where U=W(b+1). U,W and b are model parameter. α is forest canopy density. R is throughfall. P is rainfall. Further more, three parameters (U,W and b) of the model were determined according to the observation data of two coniferous tree stands. Comparison between calculation results and observation results shows that the model is perfect. The physical meanings of model parameters are clear and definite. The conceptions of model is reliable and correct . When wind speed and rain density are not very high, this model would be suitable for calculation of throughfall in forest area everywhere in order to avoid trouble of actual observation. However, it is necessary that some relationships between model parameters and canopy characteristics would be studied for further application.