Zonal Wavenumber 3 forces extreme precipitation in South America

IF 4.8 2区 地球科学 Q1 METEOROLOGY & ATMOSPHERIC SCIENCES
Valentina Ortiz-Guzmán, Martin Jucker, Steven Sherwood
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Abstract

Abstract The Southern Hemisphere climate and weather are affected by several modes of variability and climate phenomena across different time and spatial scales. An additional key component of the atmosphere dynamics that greatly influences weather is quasi-stationary Rossby waves, which attract particular interest as they are often associated with synoptic scale extreme events. In the Southern Hemisphere extratropical circulation, the most prominent quasi-stationary Rossby wave pattern is the zonal wavenumber 3 (ZW3), which has been shown to have impacts on meridional heat and momentum transport in mid to high-latitudes, and on Antarctic sea-ice extent. However, little is known about its impacts outside of polar regions. In this work, we use ERA5 reanalysis data on monthly time scales to explore the influence of phase and amplitude of ZW3 on temperature and precipitation across the Southern Hemisphere midlatitudes. Our results show significant impact in various regions for all seasons. One of the most substantial effects is observed in precipitation over southeastern Brazil during austral summer, where different phases of the ZW3 force opposite anomalies. When using ZW3 phase and amplitude as prior information, the probability of occurrence of precipitation extremes in this region increases up to three times. Additionally, we find that this ZW3 weather signature is largely independent of the zonally symmetric Southern Annular Mode (SAM); neither does it seem to be linked to El Niño Southern Oscillation (ENSO) or Indian Ocean Dipole (IOD) signal.
地带性波数 3 迫使南美洲出现极端降水
摘要 南半球的气候和天气受到不同时间和空间尺度的多种变率模式和气候现象的影响。准静止罗斯比波是大气动力学中对天气有重大影响的另一个关键组成部分,由于准静止罗斯比波常常与同步尺度的极端事件相关联,因此特别引人关注。在南半球外热带环流中,最突出的准静止罗斯比波模式是带状波数 3(ZW3),它已被证明对中高纬度经向热量和动量传输以及南极海冰范围有影响。然而,人们对其在极地以外地区的影响知之甚少。在这项研究中,我们利用ERA5再分析月度数据,探讨了ZW3的相位和振幅对南半球中纬度地区气温和降水的影响。我们的研究结果表明,ZW3 对不同地区所有季节的气温和降水都有显著影响。其中影响最大的是巴西东南部夏季的降水,ZW3 的不同相位会产生相反的异常。如果将 ZW3 的相位和振幅作为先验信息,该地区出现极端降水的概率最多会增加三倍。此外,我们发现这种 ZW3 天气特征在很大程度上独立于区带对称的南方环流模式(SAM);它似乎也与厄尔尼诺南方涛动(ENSO)或印度洋偶极子(IOD)信号无关。
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来源期刊
Journal of Climate
Journal of Climate 地学-气象与大气科学
CiteScore
9.30
自引率
14.30%
发文量
490
审稿时长
7.5 months
期刊介绍: The Journal of Climate (JCLI) (ISSN: 0894-8755; eISSN: 1520-0442) publishes research that advances basic understanding of the dynamics and physics of the climate system on large spatial scales, including variability of the atmosphere, oceans, land surface, and cryosphere; past, present, and projected future changes in the climate system; and climate simulation and prediction.
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