Drivers of elevation-dependent warming over the Tibetan Plateau

Abstract

The response of the warming magnitude over the Tibetan Plateau (TP; elevation ≥ 3000 m) to global climate change is not spatially uniform. Rather, it enhances with elevation, referred to as elevation-dependent warming (EDW). The degree of EDW over the TP is season-dependent, with the largest amplitude of 0.21°C km −1 observed during boreal winter. Several factors have been proposed in previous studies as possible drivers of TP EDW, but the relative importance of these factors has been less studied. To quantitatively identify the major drivers of TP EDW in winter over recent decades (1979–2018), the authors applied the radiative kernels diagnostic method with several datasets. The results robustly suggest that, the surface albedo feedback associated with changes in snow cover plays the leading role in TP EDW. Observations show that the snow cover has reduced significantly over regions with high elevation during the winters of the past four decades, leading to reductions in outgoing shortwave radiation and thus EDW. 摘要 青藏高原 (海拔≥ 3000 m 地区) 对全球气候变化的变暖响应是空间不均匀的, 其增温幅度会随着海拔升高而增大, 被称为海拔依赖性增温. 青藏高原海拔依赖性增温具有季节依赖性, 在冬季最为显著, 达0.21°C km −1 . 在以往的研究中, 众多因素被认为是青藏高原海拔依赖性增温的可能驱动因素, 但关于这些因素相对重要性的研究较少. 基于多个数据集, 本文应用辐射核 (radiative kernel) 技术方法定量诊断了近几十年 (1979–2018年) 冬季不同物理过程对青藏高原海拔依赖性增温的贡献. 结果表明, 与积雪变化相关的地表反照率反馈在其中起主导作用. 观测数据分析显示, 在过去40年的冬季，高海拔地区的积雪覆盖率显著减少, 导致地表反射的短波辐射减少, 从而促进了海拔依赖性增温.