下垫面因子影响气候形成和变化的数值试验

NUMERICAL EXPERIMENTS ON THE EFFECTS OF FACTORS OF UNDERLYING SURFACE ON CLIMATE FORMATION AND VARIATION

本文用球带范围的耦合模式，研究了地球从均一陆地地表到有海陆分布，全球陆地从平坦到真实地形，陆地从一类土壤到几类土壤并存过程中大气环流的演变和气候变化状况。发现没有海陆分布时气候要素场呈纬向带状分布，大气中流场和风场表现为三圈环流和行星风系特征。当有海陆分布后，北半球无论是高层还是低层环流形势均具有和海陆分布相一致的纬向两波结构，海陆分布是形成现代大气环流格局的根本因子。高原地形使高原上空的气压系统加强，并增强了东南亚的季风强度，引起高原地区降水增多，对大气的热源作用增强。土壤沙漠化使大陆上的气压系统加强，地面和大气温度上升，其影响程度和大陆面积有关。地形和地表类型在气候形成过程中有同等量级的作用，但它们都不会从根本上改变全球大气环流形势。气候系统内任何一个因子的变化都会对其它因子的敏感性程度产生影响。

Climate is a slowly-varying equilibrium system due to the interaction of atmosphere,ocean and land under the effect of the solar radiation.As the basic energy resource of the atmosphere motion,solar radiation is a decisive factor with important impacts on climate formation,while the factors of underlying surface,such as land-sea distribution,topography and properties of land surfaces,directly affect the spatial and temporal distributions of solar radiation,and consequently affect the features of general circulation in the earth-atmosphere system and the distributions of global climatic fields.So,local climate can not be parted from specific underlying surface conditions and geographic environment.Recently,many scientists studied the causes of the climate change and tried to predict the tendency of the climate variations by various methods.It has been found that climate fluctuation is affected by tropical sea surface temperature anomalies,the advance and retreat of the polar ice and concentration variations of aerosols and absorption gasses (such as CO2 and other trace gasses)in the atmosphere.In the past,it seems that people overemphasized and exaggerated the function of the orographic height on the climate,while paid little attention to the influences of land-sea distribution and properties of land surfaces,and the effects of each underlying surface factor on the process of the climate formation and variation have not been studied systematicaly.In this Paper,we discussed 3 problems:(1)effects of land-sea distribution on general circulation,(2) climatic effects of topography,(3) impacts of land surfaces on climatic change.A coupled general circulation model in a zonal domain belt (60°S to 60°N) is used to simulate the development of general circulation and the climate variations in summer.In the simulations the earth is assumed to change from a globe with a homogeneous surface to that with land-sea distributions,the global land is set to be flat with gradually uprising to the real topography.The results reveal that without land-sea distribution the climatic fields are zonally uniform,the wind fields in the atmosphere show the properties of planetary wind system and three-cell circulations.i.e.the Hadley,the Ferrel and the polar circulations,With land-sea distribution,in the north hemisphere in either the upper or the lower level atmosphere.the circulation status shows a zonal two-wave structure which is consistent with the land-sea distribution.So,land-sea distribution may be the fundamental factor which forms the modern general circulation pattern.The Tibetan Plateau topography intensifies the,Soil desertization strengthens the pressure system over the continent,increases the surfacial and atmospheric temperatures and the extent affected in the continental area,The topography and the types of land surfaces have the effects with a comparative order on the climate variation,but both of them can not change the fundamental pattern of the general circulation,Any factor in the climatic system will affect the sensitivity extent of other factors,Therefore,in order to simulate the paleoclimate during the geological periods,besides the plateau topography more factors should be considered,especially the variations of land-sea distribution and the types of the land surfaces.