Detection and attribution of precipitation trends associated with the poleward shift of the South Atlantic Convergence Zone using CMIP5 simulations,International Journal of Climatology

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Detection and attribution of precipitation trends associated with the poleward shift of the South Atlantic Convergence Zone using CMIP5 simulations
International Journal of Climatology ( IF 3.5 ) Pub Date : 2021-01-12 , DOI: 10.1002/joc.7007
Marcia T. Zilli _{1,

2} , Leila M. V. Carvalho _{1,

3}

Affiliation

Observational studies demonstrate a poleward shift in the South Atlantic Convergence Zone (SACZ) in recent decades with regional impacts on extreme precipitation. However, the relative contribution of anthropogenic forcing and natural variability to the observed trends is presently unknown. To evaluate the main forcings associated with the recent trends in precipitation rate consistent with the poleward shift of the SACZ, this study examines the last 40 years of the historical scenario of 20 global climate models participating in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). The relative contribution of natural variability and anthropogenic‐related forcings to precipitation in the 20^th century is assessed based on historical, natural, anthropogenic, and pre‐industrial simulations from CMIP5 models. Over the study area, precipitation trends simulated by the CMIP5 historical scenario are small, with large disagreement among models and members. Despite the small magnitude of the trends, the spatial pattern emerging is coherent with a poleward displacement of the SACZ, as indicated by a reduction (increase) in the precipitation rate over Southeastern Brazil (Southeastern South America). Even with large discrepancies among models, the attribution analysis suggests that precipitation trends could partially result from land‐use change, followed by changes in ozone concentrations, with more significant influence over Southeastern Brazil. The large uncertainty in the simulated precipitation suggests that not all mechanisms related to the position and intensity of the SACZ events are well captured by the CMIP5 models considered here.

中文翻译：

利用CMIP5模拟对与南大西洋收敛带极移有关的降水趋势进行归因

观测研究表明，近几十年来南大西洋收敛带（SACZ）发生了极向性的变化，对极端降水产生了区域性影响。但是，目前尚不清楚人为强迫和自然变异对观测趋势的相对贡献。为了评估与SACZ的极移相一致的近期降水率趋势相关的主要强迫因素，本研究考察了20种全球气候模式的历史情景的最后40年，该模式参与了耦合模型比较项目的第五阶段（ CMIP5）。自然变异和人为有关的强迫的相对贡献降水20^日基于CMIP5模型的历史，自然，人为和工业前模拟来评估世纪。在研究区域内，由CMIP5历史情景模拟的降水趋势很小，模型和成员之间的意见分歧很大。尽管趋势的幅度很小，但出现的空间格局与SACZ的极点位移是一致的，这可以从巴西东南部（南美东南部）的降水率降低（增加）来表明。即使各模型之间存在较大差异，但归因分析表明，降水趋势可能部分归因于土地利用的变化，其次是臭氧浓度的变化，对巴西东南部的影响更大。

更新日期：2021-01-12

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