植被覆盖度对干旱气候影响的数值试验

NUMERICAL EXPERIMENTS ABOUT THE EFFECTS OF THE DEGREE OF VEGETATION COVER ON DROUGHT CLIMATE

本文用改进了的Lorenz低谱湿模式,设计与实施了六个时间积分大于七十天的数值试验。模式包含的物理过程有:太阳幅射的地面吸收,感热输送,潜热释放,水份循环,对流调整,摩擦耗散作用,地形作用,陆面热量平衡和海陆差异。试验结果表明,大范围植被覆盖度的增加,使模式降水量增多,连续无降水日数缩短。似乎说明:植被覆盖度的增加可使干旱气候得到一定程度的改善。

The variation of vegatation cover in a large range can change the physical properties on the surface, and influence evaporation from the surface into the atmosphere, because evaporation averaged for a long range on the whole globe should be equal to the corresponding precipitation, thus, it is possible that the variation of vegatation cover has some effects on the formation of precipitation in a certain region.In order to study the effects of the variation of vegatation cover on precipitation in a certain region and drought climate, by the improved lorenz’s low-order moist spectral model, six numerical experiments whose integrational times are longer than seventy model days are designed and performed. The physical processes introduced into the model are solar radiation absorbed by the surface, exchange of sensible heat, release of latent heat, hydrological cycle, convective adjustment, frictional dissipations, land surface heat budget, orographic effects, and differences between sea and land. The experimental re-sults show the increasing of the vegatation cover may increase the model precipitations, and shorten the durations in which the day’s model precipitation is less than 1.0mm. It seems that the increasing of the degree of the vegetation cover contributes to an improvement of drought climate to a certain extent.