运用数学形态学方法探讨我国干旱-半干旱区降水的可能分布

我国北方干旱－半干旱区长期受水资源缺乏的影响，国民经济建设受到很大的制约。因此，研究干旱－半干旱区的水资源成为人们关注的重点。本文借助数学形态学方法，探讨了我国干旱－半干旱区降水在几种气候变化条件下的可能分布，揭示出了西北地区环境最脆弱的地区是塔里木盆地南缘及其东侧的罗布泊、哈密、敦煌地区，同时也探讨了这些地区在降水增加或减少情况下的可能环境分布。

A STUDY OF PRECIPITATION DISTRIBUTIONS IN ARID ANDSEMI-ARID REGIONS OF CHINA USING MATHEMATICALMORPHOLOGICAL ANALYSIS

China is a region influenced by the East Asian Monsoon.The dry area of northwest China is located in the northwestern boundary of the summer monsoon,and is a typical area with arid and semi arid climates. Mathematical morphology is an image processing method with the dilation and the erosion.A new method of multi variables and multi values was developed to process the object images composed of multi grey image.The method is similar to the conditional mathematical morphological analysis. In this paper,using the mathematical morphological method,we studied the distributions of precipitation in the arid and semi arid regions in China.The environmental types of northwest China were estimated. The precipitation of these regions was mainly supplied by the Southeastern Monsoon and the Southwestern Monsoon.According to recent meteorological data,the pattern of precipitation is stable annually.The main annual variation in precipitation is the changes in the extent of precipitation.The trend of these changes can be revealed by simulating the changes of the precipitation distribution in response to increasing or decreasing precipitation. The incrrease of mean annual temperature reflects weakening of the winter cold current and strengths the summer monsoon.The extent of precipitation in these regions expands northwards as the annual average temperatue rises.Previous studies have shown that the temperature and precipitation often change simultaneously in the geological period;the temperature is a factor controlling the precipitation.Based on the configuration of ocean and continent and the variations in solar insolation,the structural image was designed as a 2×2 matrix.The value of each processed point was controlled by the neightbouring points in the south,east and southeast.Because the details of temperature effects are not clear;the values of the matrix were simply designed as 05. The image of dilation simulates the distribution of precipitation as increasing precipitation and temperature.The result from erosion image reflects the distribution of precipitation with decreasing precipitation and temperature.Our results suggest: (1)When temperature and precipitation decrease,the dry period in the southern margin of the Tarim basin and the triangle area of Dunhuan,Luobubo and Hami starts earlier.The aridity increases in these regions and deserts will develop and expand towards the east and the south.The precipitation in the Loess Plateau dominated by steppe will decrease,leading to a reduction in biomass. (2)When temperature and precipitation increase,the regions with low rainfall between the northwest Xinjiang and the eastern China will become smallery.Based on above estimates,if the East Asian Monsoon strengthens,these two raning regions would overlay partly and the climate in the soutern margin of the Tarim basin and the triangle area of Dunhuang,Luobubo and Hami could be moister than present.A significant change will be a westward movement of vegetation belts,gviving rist to a steppe environment in the dry areas.In the Loess Plateau,the precipitation will become higher with an expansion of the steppe forest vegetation.The climate and environment during the Holocene Optimum period might have been similar to the condition mentioned above.