{"title":"Roles of External Forcing and Internal Variability in Winter Precipitation Changes Over Central Asia","authors":"Mengyuan Yao, Haosu Tang, Gang Huang","doi":"10.1029/2025EF006064","DOIUrl":null,"url":null,"abstract":"<p>Winter Central Asian precipitation (WCAP) is increasingly replacing snowfall as a critical water resource under global warming. Observations show a decline in WCAP from 1891 to 1946, followed by a recovery from 1947 to the recent decade. However, the relative contributions of external forcing and internal variability to these changes remain unclear. By analyzing observations and climate model simulations, this study finds that greenhouse gas forcing favors increasing WCAP, potentially offsetting drying trends driven by anthropogenic aerosols. Internal variability, primarily the phase transition of Atlantic Multidecadal Variability (AMV), plays a dominant role in shaping WCAP trends. The AMV-induced Rossby wave train, sustained by extracting baroclinic energy from the background mean flow, triggers barotropic atmospheric circulation anomalies that modulate WCAP. The cold-to-warm AMV phase transition (1891–1946) weakened the externally forced upward precipitation trend, reducing it from 0.19 to −0.20 mm month<sup>−1</sup> decade<sup>−1</sup>. In contrast, the warm-to-cold phase transition (1947–1997) amplified the externally forced precipitation trend, increasing it from 0.28 to 0.99 mm month<sup>−1</sup> decade<sup>−1</sup>. Under the high-emission future scenario, the time of emergence of externally driven WCAP increases is projected to occur between 2030 and 2060, at least a decade earlier than the post-2060 timeline projected under the medium-emission scenario. These findings underscore the critical role of AMV in shaping WCAP variability and highlight the necessity of emission reductions to delay the time when externally driven precipitation increases exceed the region's adaptive capacity.</p>","PeriodicalId":48748,"journal":{"name":"Earths Future","volume":"13 7","pages":""},"PeriodicalIF":7.3000,"publicationDate":"2025-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025EF006064","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Earths Future","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2025EF006064","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENVIRONMENTAL SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Winter Central Asian precipitation (WCAP) is increasingly replacing snowfall as a critical water resource under global warming. Observations show a decline in WCAP from 1891 to 1946, followed by a recovery from 1947 to the recent decade. However, the relative contributions of external forcing and internal variability to these changes remain unclear. By analyzing observations and climate model simulations, this study finds that greenhouse gas forcing favors increasing WCAP, potentially offsetting drying trends driven by anthropogenic aerosols. Internal variability, primarily the phase transition of Atlantic Multidecadal Variability (AMV), plays a dominant role in shaping WCAP trends. The AMV-induced Rossby wave train, sustained by extracting baroclinic energy from the background mean flow, triggers barotropic atmospheric circulation anomalies that modulate WCAP. The cold-to-warm AMV phase transition (1891–1946) weakened the externally forced upward precipitation trend, reducing it from 0.19 to −0.20 mm month−1 decade−1. In contrast, the warm-to-cold phase transition (1947–1997) amplified the externally forced precipitation trend, increasing it from 0.28 to 0.99 mm month−1 decade−1. Under the high-emission future scenario, the time of emergence of externally driven WCAP increases is projected to occur between 2030 and 2060, at least a decade earlier than the post-2060 timeline projected under the medium-emission scenario. These findings underscore the critical role of AMV in shaping WCAP variability and highlight the necessity of emission reductions to delay the time when externally driven precipitation increases exceed the region's adaptive capacity.
在全球变暖背景下,中亚冬季降水(WCAP)正日益取代降雪成为重要的水资源来源。观测显示,1891年至1946年WCAP下降,随后从1947年到最近十年恢复。然而,外部强迫和内部变率对这些变化的相对贡献仍然不清楚。通过分析观测和气候模式模拟,本研究发现温室气体强迫有利于增加WCAP,可能抵消人为气溶胶驱动的干燥趋势。内部变率,主要是大西洋多年代际变率(AMV)的相变,在形成WCAP趋势中起主导作用。amv诱导的罗斯比波列,通过从背景平均气流中提取斜压能量来维持,触发正压大气环流异常,从而调节WCAP。冷-暖AMV相变(1891-1946)减弱了外强迫降水上升趋势,使其从0.19 mm /月减少到- 0.20 mm /月。1947-1997年暖-冷相变放大了外强迫降水趋势,使其从0.28 mm /月增加到0.99 mm /年。在未来高排放情景下,预计外部驱动的WCAP增长出现的时间在2030年至2060年之间,比中等排放情景下预测的2060年后时间提前至少10年。这些发现强调了AMV在形成WCAP变率中的关键作用,并强调了减排的必要性,以推迟外部驱动的降水增加超过该地区适应能力的时间。
期刊介绍:
Earth’s Future: A transdisciplinary open access journal, Earth’s Future focuses on the state of the Earth and the prediction of the planet’s future. By publishing peer-reviewed articles as well as editorials, essays, reviews, and commentaries, this journal will be the preeminent scholarly resource on the Anthropocene. It will also help assess the risks and opportunities associated with environmental changes and challenges.