植被带宽度对局地环流及温度场影响的数值研究

A NUMERICAL STUDY OF EFFECT OF WIDTH OF PLANT ZONE ON LOCAL CLIMATE

本文用一个二维模式，实施了七组数值试验，研究植被带宽度ｄ对局地气候的影响。结果指出：存在着一个最适宜的植被带宽度ｄｃ，当ｄ＝ｄｃ时，植被－裸土之间下垫面属性的非均一性激发的上升运动的强度最强。当ｄ＞ｄｃ或ｄ＜ｄｃ时，上升运动均会减弱。这是一个具有非线性的现象。此外，还分析了背景流对次级环流的影响。

The horizontal inhomogeneties of thermal and dynamic characters in the land surface induced by plant-bare soil zones whose space scale are 100-10l km can generate meso-scale circulation and change the local climate. In order to study the effect of the width of plant zone(d) on the meso-scale circulation and the local climate, seven numerical experiments (Ex1-Ex7) have been designed and performed by using a two-dimensional midel. Set d = 5, 7, 9, 11, 13, 15 km, respectively and Ug=2.5 m/s in Ex1-Ex6, where Ug denotes the basic zonal wind velocity, and set d= 9 km and Ug= 0.0 m/s in Ex7. The results are as follows:1. The effect of the width of plant zone on local temperature. A cold island over the plant-zone appears. The intensity of the cold island increases with the width. exhibiting a linear character ristic. 2.The effect of the width of plant zone on the maximum of vertical velocity. There is a most favorable value of the width dc, when d= dc, the intensities of the vertical cells, which are excited by the plant-bare soil horizontal inhomogeneties, achieve their maxima, exhibiting a nonlinear characteristic. 3. The influence of the basic flow on the vertical cells. It seems that the introduction of the basic flow into the model makes more intensive vertical cells. The investigation of the effect of the inhomogeneties induced by plant-bare soil zones on the local climate is a complicated subject.This work is an attempt in this field. Further study is needed to improve the model and experiments,and the work is just under way.