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Zonal Wavenumber 3 Forces Extreme Precipitation in South America.

Authors :
Ortiz-Guzmán, Valentina
Jucker, Martin
Sherwood, Steven C.
Source :
Journal of Climate. Jul2024, Vol. 37 Issue 13, p3649-3660. 12p.
Publication Year :
2024

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 the 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 a 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 the 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. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
08948755
Volume :
37
Issue :
13
Database :
Academic Search Index
Journal :
Journal of Climate
Publication Type :
Academic Journal
Accession number :
179550835
Full Text :
https://doi.org/10.1175/JCLI-D-23-0739.1