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Obliquity-driven changes in East Asian seasonality
Global and Planetary Change ( IF 3.9 ) Pub Date : 2020-06-01 , DOI: 10.1016/j.gloplacha.2020.103161
Chi-Hua Wu , Pei-Chia Tsai

Abstract Obliquity, as a factor controlling seasonality, has been considered a modulator of paleomonsoon evolution. However, in contrast to the clearly identified contribution of precession, East Asian proxy records rarely provide a robust signal of obliquity. By investigating climate simulations with extremely low versus high obliquity, this study examined the seasonal contribution of obliquity, finding that obliquity has substantial effects on the diversity of precipitation stages over East Asia–Western North Pacific (WNP). The sensitivity of greenhouse gases (GHG) to the effects of obliquity also suggests that the contribution of obliquity could depend on GHG concentrations. When GHG forcing is weak, summer precipitation migrates following the obliquity-driven meridional insolation changes over Africa, South Asia, and East Asia. In contrast to a condition of high obliquity with a continental origin of the monsoon, summer monsoon precipitation is confined to the subtropical area including the existence of the WNP monsoon trough in low obliquity. The intrinsic dynamic mode over East Asia–WNP, characterized by a meridional dipole pattern in circulation and precipitation, disappears when obliquity is extremely high. In winter, the strength of synoptic scale (the midlevel trough, Siberian high, and Aleutian low over and around East Asia) and larger scale (midlatitude westerly jet stream and Hadley circulation) circulation is coincidently weaker when compared with that in high obliquity. Obliquity-driven changes over East Asia–WNP are also partly sensitive to GHG concentrations. Furthermore, some major obliquity-driven changes weaken and even disappear when GHG concentrations increase.

中文翻译:

东亚季节性的倾斜驱动变化

摘要 倾斜度作为控制季节性的因素,被认为是古季风演化的调节因子。然而,与明确确定的岁差贡献相反,东亚代理记录很少提供强烈的倾斜信号。通过调查倾角极低与高倾角的气候模拟,本研究检验了倾角的季节性贡献,发现倾角对东亚-西北太平洋 (WNP) 降水阶段的多样性有重大影响。温室气体 (GHG) 对倾斜影响的敏感性也表明倾斜的贡献可能取决于温室气体浓度。当温室气体强迫较弱时,夏季降水会随着非洲、南亚和东亚的倾斜驱动的经向日照变化而迁移。与季风起源于大陆的高倾角条件相反,夏季季风降水仅限于亚热带地区,包括低倾角的西北部季风槽的存在。以环流和降水中的经向偶极子模式为特征的东亚-WNP的固有动力模式在倾角极高时消失。冬季,天气尺度(东亚及周边的中层槽、西伯利亚高压和阿留申低压)和更大规模(中纬度西风急流和哈德利环流)环流的强度与高倾角相比,恰巧较弱。东亚-WNP 的倾斜驱动变化也部分对温室气体浓度敏感。此外,
更新日期:2020-06-01
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