Recurrent Rossby waves and south-eastern Australian heatwaves

Ali, S. Mubashshir; Röthlisberger, Matthias; Parker, Tess; Kornhuber, Kai; Martius, Olivia (2022). Recurrent Rossby waves and south-eastern Australian heatwaves. Weather and climate dynamics, 3(4), pp. 1139-1156. Copernicus Publications 10.5194/wcd-3-1139-2022

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In the Northern Hemisphere, recurrence of transient synoptic-scale Rossby wave packets in the same phase over periods of days to weeks, termed RRWPs, may re-
peatedly create similar surface weather conditions. This recurrence can lead to persistent surface anomalies. Here, we first demonstrate the significance of RRWPs for persistent hot spells in the Southern Hemisphere (SH) using the ERA-
Interim (ERA-I) reanalysis dataset and then examine the role of RRWPs and blocks for heatwaves over south-eastern Australia (SEA).
A Weibull regression analysis shows that RRWPs are statistically associated with a significant increase in the duration of hot spells over several regions in the SH, including SEA. Two case studies of heatwaves in SEA in the summers of 2004 and 2009 illustrate the role of RRWPs in forming recurrent ridges (anticyclonic potential vorticity – PV – anomalies), aiding in the persistence of the heatwaves. Then, using a weather-station-based dataset to identify SEA heatwaves, we find that SEA heatwaves are more frequent than climatology during days with extreme RRWPs activity over SEA (high RSEA). On days with both high RSEA and at waves, circumglobal zonal wavenumber 4 and 5 (WN4, WN5) anomaly patterns are present in the composite mean of the upper-level PV field, with an anticyclonic PV anomaly over SEA. The Fourier decomposition of the PV and meridional wind velocity fields further reveals that the WN4 and WN5 components in the suitable phase aids in forming the ridge over SEA for days with high RSEA. In addition, we find anomalous blocking over the Indian and the South Pacific oceans duing SEA heatwaves, which may help to modulate the phase
of RRWPs.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR) > MobiLab
08 Faculty of Science > Institute of Geography > Physical Geography > Unit Impact
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Institute of Geography
08 Faculty of Science > Institute of Geography > Physical Geography

UniBE Contributor:

Ali, Syed Mubashshir, Romppainen-Martius, Olivia

Subjects:

500 Science > 550 Earth sciences & geology
900 History > 910 Geography & travel

ISSN:

2698-4016

Publisher:

Copernicus Publications

Funders:

[4] Swiss National Science Foundation ; [222] Horizon 2020

Language:

English

Submitter:

Lara Maude Zinkl

Date Deposited:

21 Feb 2023 08:21

Last Modified:

03 Mar 2023 15:13

Publisher DOI:

10.5194/wcd-3-1139-2022

BORIS DOI:

10.48350/178979

URI:

https://boris.unibe.ch/id/eprint/178979

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