全球增暖和极端事件对全球温度场关联性的影响

The influence of global warming and extreme events on the correlation of the global temperature field

中文关键词:  温度场，关联矩阵，温度趋势，极端事件

英文关键词:Temperature field, Correlation matrix, Trends, Extreme event

中文摘要:

      基于NCEP/NCAR和ERA-40的逐日平均温度再分析资料构建全球温度场关联矩阵，分别讨论了温度趋势和极端温度事件对全球温度场关联性的影响。结果表明：温度趋势对全球温度场关联性的空间分布型没有太大影响，保持相对稳定，但对其强度有所改变。其中,赤道及低纬度地区关联性明显减弱，中纬度部分区域关联性有所增强；呈降温趋势的地区在去除降温趋势后关联性有所增强，而增温趋势较明显的区域与去除增温趋势后关联性减弱较明显的区域，在区域位置及形状分布上也有较好的对应关系。去除温度趋势后，全球平均关联系数（RTglobal）随时间变化的趋势没有明显改变，尤其是准周期振荡的特征依然存在，说明温度场内部关联作用的30 a准周期振荡是不受全球增暖影响的系统固有特征尺度；同时，RTglobal在大部分时段比去除温度趋势前略有减小，充分表明全球增暖总体有利于系统内部关联作用的加强；21世纪以后RTglobal的明显减小则从侧面反映了全球增暖在2000年以来的新特征。因此，全球温度变化不仅表现为要素值的趋势变化，在温度场内部相互作用的空间范围和强度变化上也有清晰的体现，后者在以往的研究中较少被提及。此外，进一步讨论了极端温度值对全球温度场关联性的影响：不同极端温度值替代方案的采用对20世纪90年代初期之前RTglobal随时间变化的趋势没有明显影响，但20世纪90年代初期之后R RTglobal与不替代极端温度值的情况相比差异明显增大。这可能与不同方案下温度场关联系数的南、北半球空间分布在90年代前后发生较大改变有关。

英文摘要:

      Based on temperature correlation matrixes constructed by NCEP/NCAR and ERA-40 reanalysis temperature data, this paper discusses the influence of the trends and extreme events on the correlation of the global temperature field. The results show that: on the whole, the trends of temperature series show little impact on the spatial temporal distribution of correlation of the global temperature field, suggesting that the 30 years quasi periodic oscillation of the correlation of the global temperature field is the inherent characteristic scale and has nothing to do with global warming. However, in case the trends of temperature series have been removed, the correlation between the regions that present cooling trend is increased, whereas the regions that present warming trend show opposite regularity. The global average correlation coefficient (RTglobal) deceased slightly after the trends of temperature series have been removed, which support the hypothesis that global warming is advantageous to increase of correlation of the global temperature field, and the significantly decrease of RTglobal after 2000 illustrates the new characteristics of global warming in the 21st century. The variation of global temperature is revealed not only in the change of trends, but also in the spatial extension and the intensity of correlation of the global temperature field. In order to study influence of the extreme events on the correlation of global temperature field, three schemes of extreme events substitution were introduced. The results indicate that RTglobal get from the three schemes show obvious difference after the 1990s, and this may be because of the change of spatial distribution of correlation coefficient of the Northern and Southern Hemisphere at that time.