Quantifying the internal variability in multi-decadal trends of spring surface air temperature over mid-to-high latitude
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Quantifying the internal variability in multi‑decadal trends of spring surface air temperature over mid‑to‑high latitudes of Eurasia Zhaomin Ding1,3 · Renguang Wu1,2,4 Received: 5 January 2020 / Accepted: 6 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This study investigates the influences of internal climate variability (ICV) on Eurasian spring (March–May) surface air temperature (SAT) trends based on a 30-member ensemble of the Community Earth System Model version 1 (CESM1) from 1979 to 2014. The SAT trends over the mid-high latitude Eurasia vary considerably among individual simulations, indicating a large impact of ICV on SAT trends at regional scales. The leading pattern of internally generated SAT trend variability over Eurasia among the 30 SAT trends displays same sign distribution over the mid-high latitudes of Eurasia. This pattern is associated with the Northern Hemisphere annular mode (NAM) that accounts for about 1/3 of total variance of the spring sea level pressure (SLP) trends. The second pattern of internally generated SAT trend variability features a dipole structure, accompanied by prominent circulation changes over the North Atlantic and Europe. Internal dynamics account for approximately 40–70% of the observed warming over the central Eurasia and the Russian Far East. A dynamical adjustment methodology is employed to remove the effects of internal atmospheric circulation variability. Dynamical adjustment greatly reduces the spread of SAT trends within the ensemble and brings both the simulated and observed trends closer to the ensemble mean. Changes in the Barents–Kara Sea ice and Eurasian snow cover contribute to the remaining spread in SAT trends over the north coast of Russia and in the region north of the Caspian Sea, respectively. Both dynamics and thermodynamics contribute to the Barents–Kara Sea ice and Eurasian snow cover trends. Keywords Internal climate variability · Eurasian spring surface air temperature · Dynamical adjustment · Coupled climate model · Sea ice and snow impacts
1 Introduction Surface air temperature (SAT) is one of the quantities of concern in climate change. Variations in SAT have a large impact on agriculture, ecosystems, and human society (Barriopedro et al. 2011; Beniston 2004; Feudale and Shukla 2011; Stott et al. 2004). Increase in anthropogenic emissions * Renguang Wu [email protected] 1
Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
2
School of Earth Sciences, Zhejiang University, Hangzhou 310027, China
3
College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
4
Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China
of greenhouse gases has contributed to the global warming trend since the industrial revolution (Meehl et al. 2007). However, at regional scales, contributions from internal climate variability (ICV) are non-negligible or even dominate over the anthropog
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