不同辐射强迫对暖干复合事件强度长期趋势信号检测的影响

本文基于Copula联合概率建立表征暖干复合事件强度的指数,基于单个辐射强迫的地球系统模式大样本模拟试验的结果,使用4种场显著性检验的方法分析了不同辐射强迫下中国区域整体暖干事件强度长期趋势信号的可检测性。结果表明,4种方法得到的结论较为一致,均表明全强迫(自然外强迫和人为外强迫)下中国大部分区域复合事件的强度显著增强,不同集合成员之间的趋势较为一致,表明长期趋势主要受外强迫而非气候系统内部变率影响,其长期趋势的外强迫信号大约出现在2005年。在单个温室气体强迫的模拟试验下,复合事件强度的长期趋势更为明显,主要体现在强度更强并且长期趋势中外强迫信号出现的时间更早(约2000年)。但是在单个气溶胶强迫下,尚检测不到暖干事件强度长期趋势的外强迫信号。进一步分析表明,温度变化是暖干事件强度长期趋势变化的主要贡献因素。温室气体强迫下温度的贡献更大,尤其是在我国西部地区。

Influence of external forcing on the detection in the long-term trend of hot and dry compound events over China

Based on the Copula model, an index was constructed to measure the Severity of Compound Hot and Dry Event (SDHI). A large ensemble simulation from single radiative forcing was used to analysis the detectability of the long-term trend of the SDHI over China. Four methods used to test the field significant were compared, and the results from them were consistent. Under all forcing (natural forcing plus anthropogenic forcing), the severity of the events in most regions of China exhibit significant increasing trend, and the differences among individuals ensembles are relatively small, indicating that the long-term trend is mainly affected by the external forcing rather than the internal variability of climate system, and the external forcing signal in long-term trend of SDHI appears around 2005. The long-term trend of the SDHI is more obvious under single greenhouse gas forcing experiment, and the trend signal appeared as early as around 2000. However, the signal of trend cannot be detected in the simulation experiment under the single aerosol forcing. Further analysis shows that temperature changes dominate the long-term trend of SDHI. Under the single greenhouse gas forcing, the contribution of temperature is greater than that under all forcing experiment, especially in western China.