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当前全球气候变暖大背景下,气温和降雨量的交互作用引致农业气象灾害频发,给农业生产造成破坏性风险损失,因此探讨气温与降雨量之间的动态相依关系尤为重要。搜集安徽省24个气象观测站1980~2014年的气温与降雨量日数据,对原始数据进行矩平均处理,使两组数据列满足独立同分布的要求。采用非参数核估计的方法确定气温与降雨量的边缘分布。根据降雨量和气温的均匀分布散点图和频数分布直方图可知,安徽省气温和降雨量之间呈现一定程度的负相依关系,即图形中表现出气温与降雨量的上下尾之间的对称性。综上分析,选择可以刻画两个变量具有上下尾对称关系的Copula函数对气温与降雨量的相依关系进行拟合,最终在平方欧式距离最小的原则下选定二元t-Copula函数做出气温与降雨量之间的联合概率密度函数图。研究结果发现:1据安徽省气温与降雨量联合概率分布可知,当降雨量上升时,气温下降;或气温上升时,降雨量会下降,气温与降雨量之间呈现为中等负相关关系(–0.280)。2极值相关性方面,从t-Copula密度函数图和上下尾相关系数看,安徽省气温与降雨量在极值方面具有较为明显的相依关系,表现为当气温和降雨量超过正常范畴时,二者相依关系从负相关转变为正相关,此现象多出现在极端气候条件下,例如极端高温和大暴雨时气温与降雨量的正相依性。
Under the current background of global warming, the interactions between temperature and rainfall lead to frequent agrometeorological disasters and cause damaging losses to agricultural production. Therefore, it is particularly important to explore the dynamic dependence between temperature and rainfall. The daily data of temperature and rainfall in 24 meteorological stations in Anhui province from 1980 to 2014 were collected, and the average data of the raw data were averaged to make the two sets of data satisfy the independent and identically distributed requirements. Nonparametric kernel estimation method is used to determine the edge distribution of temperature and rainfall. According to the histogram of scatter plot and frequency distribution of rainfall and temperature, we can see that there is a certain degree of negative correlation between temperature and rainfall in Anhui Province, that is, the symmetry between the upper and lower tail of the temperature and rainfall in the map Sex. Based on the above analysis, the Copula function can be used to describe the dependence of temperature and rainfall on Copula function, which can characterize the upper and lower tail symmetry between the two variables. Finally, the binary t-Copula function is selected to make the temperature Joint probability density function with rainfall. The results show that: 1 According to the joint probability distribution of temperature and rainfall in Anhui Province, when the rainfall increases, the temperature decreases, or when the temperature rises, the rainfall decreases and the temperature and rainfall show a moderate negative correlation (- 0.280). 2 Extreme correlation, from the t-Copula density function and the upper and lower tail correlation coefficient, Anhui Province, temperature and rainfall in the extreme value has a more obvious relationship, the performance is when the temperature and rainfall exceeds the normal range, The relationship between the two changes from negative to positive correlation, the phenomenon occurs in extreme climatic conditions, such as extreme heat and heavy rainfall when the temperature and rainfall are positively dependent.