Comparative Analysis of the Mechanisms of Intensified Summer Warming over Europe-West Asia and Northeast Asia since the Mid-1990s through a Process-based Decomposition Method

Abstract

Previous studies have found amplified warming over Europe-West Asia and Northeast Asia in summer since the mid-1990s relative to elsewhere on the Eurasian continent, but the cause of the amplification in these two regions remains unclear. In this study, we compared the individual contributions of influential factors for amplified warming over these two regions through a quantitative diagnostic analysis based on CFRAM (climate feedback-response analysis method). The changes in surface air temperature are decomposed into the partial changes due to radiative processes (including CO₂ concentration, incident solar radiation at the top of the atmosphere, surface albedo, water vapor content, ozone concentration, and clouds) and non-radiative processes (including surface sensible heat flux, surface latent heat flux, and dynamical processes). Our results suggest that the enhanced warming over these two regions is primarily attributable to changes in the radiative processes, which contributed 0.62 and 0.98 K to the region-averaged warming over Europe-West Asia (1.00 K) and Northeast Asia (1.02 K), respectively. Among the radiative processes, the main drivers were clouds, CO₂ concentration, and water vapor content. The cloud term alone contributed to the mean amplitude of warming by 0.40 and 0.85 K in Europe-West Asia and Northeast Asia, respectively. In comparison, the non-radiative processes made a much weaker contribution due to the combined impact of surface sensible heat flux, surface latent heat flux, and dynamical processes, accounting for only 0.38 K for the warming in Europe-West Asia and 0.05 K for the warming in Northeast Asia. The resemblance between the influential factors for the amplified warming in these two separate regions implies a common dynamical origin. Thus, this validates the possibility that they originate from the Silk Road pattern.

摘 要

以前的研究发现, 自 20 世纪 90 年代中期以来, 欧洲-西亚和东北亚相对于欧亚大陆其他区域夏季增暖更为显著, 但增暖放大的原因尚不清楚. 本文基于气候反馈响应分析方法 (climate feedback–response analysis method, CFRAM), 定量诊断了不同影响因子对两个区域增暖的贡献. CFRAM 方法将地表气温变化分解为由辐射过程 (包括CO₂浓度、 大气层顶入射太阳辐射、 地表反照率、 水汽含量、 O₃浓度和云) 和非辐射过程(包括地表感热通量、 地表潜热通量和动力过程) 造成的温度变化分量. 结果表明:欧洲-西亚和东北亚的强增温主要归因于辐射过程的变化, 辐射过程对欧洲-西亚地表气温变化 (1.00K) 和东北亚地表气温变化 (1.02K) 的贡献分别为 0.62 和 0.98K. 云、 CO₂ 浓度和水汽含量是辐射过程的主要驱动因子. 其中, 云的变化对欧洲-西亚和东北亚增暖分别贡献了 0.40 和 0.85k. 由于地表感热通量、 地表潜热通量和动力过程的共同影响, 导致非辐射过程的总贡献较弱, 在欧洲-西亚和东北亚分别仅产生了 0.38 和 0.05k 的增暖. 影响地表温度变化的因子之间的相似性表明两个区域的增暖可能具有相同的动力起源. 因此, 进一步验证了欧洲-西亚和东北亚增暖均起源于丝绸之路遥相关的可能性.