Analysis Of Climatic Characteristics In Arid And Semi-arid Areas Of Northwest China

The Qinghai-Tibet Plateau is a plateau region in central Asia.The average altitude is above4000 meters.The peaks above the snow line are more than 6000-8000 meters high.The plateau covers an area of more than 2.5 million square kilometers.It is about 3000 kilometers long from east to west and 1,500 kilometers wide from north to south.The Qinghai-Tibet Plateau is known as the "Roof of the World" and the "Third Pole".Due to its unique geographic and geomorphic characteristics,the thermal and dynamic effects of the atmosphere over the Qinghai-Tibet Plateau are important factors that control global atmospheric circulation,and have an extremely important impact on the formation,development,and changes of atmospheric circulation and climate change in China,Asia,and even the world.The research area of this article is the arid and semi-arid area of northwest China,that is,the north and northeast of the Qinghai-Tibet Plateau.The latitude and longitude range of the arid area is(35°-40°N,90°-105°E),and the latitude range of the semi-arid area is(32°-38°N,105°-114°E).Aiming at the two research regions of the arid and semi-arid regions of northwest China,we first analyzed the temperature changes at different altitudes,the total ozone column changes,and the precipitation changes in these two regions.The total ozone column in each region shows a downward trend,and the temperature at different altitudes shows a trend of first decline and then rise,that is,the temperature is cooling in the upper layer for 40 years,but gradually warming in the lower layer for 40 years.The difference between the two regions is that the altitude at which the temperature is reversed is slightly different.In addition,the precipitation in the two regions shows an upward trend,and the upward trend is also slightly different.Ozone is mostly distributed in the upper stratosphere of the troposphere.It is found through analysis that the height of the troposphere in the two regions varies from 95 hpa to 100 hpa.According to the temperature reversal level and the changes in the troposphere,100 hpa temperature,150 hpa temperature,200 hpa temperature,total ozone column,and precipitation were finally selected to establish the copula model.Through the calculation of the model correlation coefficients and the final model construction results,it is found that when the correlation coefficients of the five meteorological features are simply calculated,most of the meteorological features show a relatively strong correlation.But after modeling the marginal distribution of the five meteorological features,using the copula function(also called the connection function)to analyze the dependence,it is found that the correlation between the five features is not so strong.The first-level tree structure in the two regions the correlation coefficient between variables is around 0.3,and the correlation coefficient between variables in the second-level tree structure is around 0.1.As the dimensionality of the copula function increases,this dependency relationship gradually becomes smaller,and there is basically no dependency relationship between the variables of the last level of the tree structure.This decrease in the correlation with the increase of the tree structure conforms to the correlation theory of the copula function.But the difference is that when this model is used in economics,the relationship between the first-level tree structure is relatively large in most cases.After comparing with the application of this model in the stock market,the use of the copula function model in meteorology is also Need to be further improved.The innovation of the article lies in applying the copula model commonly used in economics to the analysis of meteorological characteristics to obtain the interdependence between meteorological characteristics.