关键词: 海陆分布, 地形, 地表类型, 大气环流, 数值试验

Abstract: 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癝 to 60癗) 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.

Key words: land-sea distribution, topography, properties of underlying surfaces, gen eral circulation, numerical experiments