【摘要】 为了探讨我国北方（39°N,100°E）半干旱地区森林与裸地非均匀下垫面对减轻于旱的作用,本文利用二维β中尺度模式进行了夏季非均匀下垫面对边界层气候影响的数值试验。结果表明,在夏季晴朗静风、无系统扰动条件下,温、湿度为非均匀的下垫面对边界层气候起着决定性的影响。增强的对流运动有利于林区降水的增加。来自林区的湿平流对周围气候的调节可达30—50km。在林区附近裸地进行灌溉,可形成比较冷、湿的环境,有利于干旱的减轻。干燥裸地边界层内的逆湿现象是由于下垫面非均匀的湿度场与中尺度平流的共同作用的结果。更多还原

【Abstract】 Using a two-dimensional β°-mesoscale model, the numerical experiment about the influence of inhomogeneous surface on the boundary-layer climate in summer was carried out in order to explore the reduction of droughts over the inhomogeneous underlying surface, which is consisted as forest and arid/wet bare land in the semi-arid region of North China (around 39°N, 100°E). The results demonstrate that, on a clear and clam day without the disturbance of a weather system, the underlying surface characterized by the horizontal inhomogeneity of temperature and humidity plays a determining role in the conditions of the boundary-layer climate and an enhancing role in the convective precipitation under appropriate atmospheric conditions. The moist advection from the forest aera can adjust drought conditions within a range of 30-50 km horizontally inside the bare land near by the forest. Irrigation can form a colder and moister envelopment, and therfore reduce the drought. A phenomenon called humidity inversion is caused by the joint of the heterogeneous humidity Pattern and mesoscale advection over the underlying surface.更多还原