Influence of El Niño‐Southern Oscillation on baroclinic instability and storm tracks in the Southern Hemisphere

Abstract

Earth's weather and climate are strongly influenced by synoptic scale systems such as extratropical cyclones. From this point of view, investigating the mechanisms associated with cyclogenesis, such as baroclinic instability (BI), which are defined by the thermal gradient and wind shear, are extremely important. However, atmospheric teleconnection patterns such as the El Niño-Southern Oscillation (ENSO) phenomenon may affect BI in the preferred region of extratropical cyclones, known as the storm track (ST) region. Therefore, the present study shows the impact of ENSO on BI and STs in the Southern Hemisphere. BI is determined by means of the Eady growth rate method, while the STs are calculated from the kinetic energy and by means of the meridional heat transport. In general, the results show that STs calculated from the BI and the kinetic energy show seasonal variability during ENSO events. This results in Southern Hemisphere extratropical cyclones being more intense with trajectories towards lower (higher) latitudes during El Niño (La Niña) summers. In contrast, little difference is seen in El Niño and La Niña winters. For the calculation of the meridional heat transport at 500 hPa, the Climate Forecast System Reanalysis produced weaker transport relative to ERA-Interim and previous studies.

The Response of Southwest Atlantic Storm Tracks to Climate Change in the Brazilian Earth System Model

“…Using the Eulerian approach, Machado et al, 2020 [15] studied the influence of ENSO on the ST distribution in the Southern Hemisphere, and their results corroborated those Reboita et al, 2015 [14]. Machado et al, 2020 [15] concluded that during El Niño periods there is a change in ST position in relation to that in neutral periods and La Niña periods. Machado et al, 2012 [16] and Machado et al, 2015 [17] evaluated BI and STs in the SH for climate change scenarios.…”

Extreme warm events in the South Orkney Islands, Southern Ocean: Compounding influence of atmospheric rivers and föhn conditions

“…Such increases in both the warm extreme occurrences at the stations and their regional drivers are possibly linked to a latitudinal shift of the storm tracks in association with the El Niño-Southern Oscillation (ENSO) (Turner, 2004;Turner et al, 2016). Machado et al (2021) found that there has been a latitudinal migration of the storm tracks in summer in association with ENSO. The position of the storm tracks is also strongly influenced by the Southern Annular Mode (SAM; Marshall, 2003Marshall, , 2007.…”

“…Machado et al . (2021) found that there has been a latitudinal migration of the storm tracks in summer in association with ENSO. The position of the storm tracks is also strongly influenced by the Southern Annular Mode (SAM; Marshall, 2003, 2007).…”

Assessing Latent and Kinetic Energy Trend Changes in Extratropical Cyclones From 1940 to 2020: Results From ERA‐5 Reanalysis

“…Several modeling studies have discussed the sensitivity between ETCs and initial temperature/moisture fields (Grise et al., 2019; Krishbaum et al., 2018), which has contributed to some contradiction in models either under‐ or over‐estimating forced changes to mean and extreme precipitation (de Vries et al., 2023). Existing literature clearly highlights the importance and effects of increasing moisture on baroclinic eddies and ETCs, but numerous uncertainties remain in how their evolving energetics will manifest as changes to important climate system components such as the Hadley Circulation and the stratification of the extratropical troposphere (O’Gorman, 2011) or the El Nino Southern Oscillation (Machado et al., 2021). Furthermore, to the authors' knowledge, no multi‐decade analysis quantifying regional changes in moisture specifically to baroclinic eddies and ETCs has been done.…”