A climatology of Southern Hemisphere extratropical cyclones

Jones, David A.; Simmonds, Ian

doi:10.1007/bf00209750

Cited by 227 publications

(175 citation statements)

References 17 publications

Supporting

Mentioning

154

Contrasting

Order By: Relevance

“…The cyclone trajectory and large-scale indicators were obtained through an automatic procedure using the Melbourne University tracking algorithm (Murray and Simmonds, 1991;Simmonds et al, 2003) which is a state-of-the-art method for diagnosing low-and highpressure centres on a sphere and calculating their trajectories (Jones and Simmonds, 1993;Simmonds and Keay, 2000). All the parameters and specifications used were the same as described in Pezza and Simmonds (2005), who showed that the scheme successfully reproduced Catarina's trajectory.…”

Section: Methodsmentioning

confidence: 99%

Climate perspective on the large‐scale circulation associated with the transition of the first South Atlantic hurricane

Pezza

Simmonds

Filho

2008

Intl Journal of Climatology

Self Cite

View full text Add to dashboard Cite

ABSTRACT:The landfall of Cyclone Catarina on the Brazilian coast in March 2004 became known as the first documented hurricane in the South Atlantic Ocean, promoting a new view on how large-scale features can contribute to tropical transition. The aim of this paper is to put the large-scale circulation associated with Catarina's transition in climate perspective. This is discussed in the light of a robust pattern of spatial correlations between thermodynamic and dynamic variables of importance for hurricane formation. A discussion on how transition mechanisms respond to the present-day circulation is presented. These associations help in understanding why Catarina was formed in a region previously thought to be hurricane-free.Catarina developed over a large-scale area of thermodynamically favourable air/sea temperature contrast. This aspect explains the paradox that such a rare system developed when the sea surface temperature was slightly below average. But, although thermodynamics played an important role, it is apparent that Catarina would not have formed without the key dynamic interplay triggered by a high latitude blocking. The blocking was associated with an extreme positive phase of the Southern Annular Mode (SAM) both hemispherically and locally, and the nearby area where Catarina developed is found to be more cyclonic during the positive phase of the SAM. A conceptual model is developed and a 'South Atlantic index' is introduced as a useful diagnostic of potential conditions leading to tropical transition in the area, where large-scale indices indicate trends towards more favourable atmospheric conditions for tropical cyclone formation.

show abstract

Section: Methodsmentioning

confidence: 99%

Climate perspective on the large‐scale circulation associated with the transition of the first South Atlantic hurricane

Pezza

Simmonds

Filho

2008

Intl Journal of Climatology

Self Cite

View full text Add to dashboard Cite

show abstract

“…To prevent the inclusion of smallscale or broad, shallow features associated with topography or other effects rather than genuine, migrating systems, a minimum curvature test was applied. The ability of the Murray and Simmonds scheme to identify and track systems in the observational record has been demonstrated by Jones and Simmonds (1993) and Simmonds et al (1999), to whom the reader is referred for further details of the scheme's technical aspects and performance. The specific cyclone characteristics considered are the cyclone system density, system depth or intensity, and vector flux of systems, all measured per degree latitude/longitude square.…”

Section: Model and Experiments Descriptionmentioning

confidence: 97%

Sensitivity of the southern African circulation to dipole sea‐surface temperature patterns in the south Indian Ocean

Reason

2002

Intl Journal of Climatology

135

104

View full text Add to dashboard Cite

Previous observational work suggests that when sea-surface temperature (SST) is warm (cool) in the southwest Indian Ocean and cool (warm) in the southeast Indian Ocean, increased (decreased) summer rains may occur over large areas of southeastern Africa. In this study, an atmospheric general circulation model is used to investigate the sensitivity of the regional circulation and rainfall over southern Africa to these dipole SST anomalies in the subtropical south Indian Ocean. When the model is forced with positive SST anomalies in the west and negative SST anomalies in the east, increased rainfall occurs over southeastern Africa as a result of the enhanced convergence of moister than average air over the region. Enhanced evaporation occurs over the warm pole in the southwest Indian Ocean and this moist air is advected towards southeastern Africa as a result of the low-pressure anomaly generated over this pole, which strengthens the onshore flow. Increased and more intense extra-tropical cyclones occur to the southeast of South Africa, favourable for tropical-temperate trough formation. When the SST poles are reversed in sign, decreased precipitation occurs over southeastern Africa as a result of increased low-level divergence of low-level flow and this flow being drier than average. Weaker and fewer extra-tropical cyclones occur southeast of South Africa in this case.The model results are sensitive to the proximity of the southwest Indian Ocean pole to southeastern Africa. There is also sensitivity in the model low-level wind changes and precipitation anomaly over low-latitude southern Africa (but not over South Africa to any significant extent) to the presence or absence of the SST pole over the southeast Indian Ocean. Although the model resolution does not capture the details of the local SST and topographic gradients as well as one would like, the changes in model circulation and precipitation in the experiments with different SST anomalies are consistent with previous observational and theoretical work, hence increasing confidence in the robustness of the results.

show abstract

“…While a number of such methods exist, for the purposes of this study we used the Bureau of Meteorology tracking scheme (Jones and Simmonds 1993), which is a version of the Murray and Simmonds (1991) scheme. This is one of the more widely used tracking schemes in the literature, however it does lack some of the later refinements in Simmonds et al (1999).…”

Section: The East Coast Low Databasementioning

confidence: 99%

Identifying East Coast Lows with climate hazards on the eastern seaboard

Pepler¹,

Imielska²,

Coutts-Smith³

et al. 2016

JSHESS

View full text Add to dashboard Cite

East Coast Lows are an important weather system that can produce severe wind, wave and rainfall events along the eastern seaboard of Australia. While a number of databases of these systems have been produced, this information has historically not been readily accessible to potential users outside the research sector. This paper details the development of a new product, Maps and Tables of Climate Hazards on the Eastern Seaboard (MATCHES), that bridges this gap. It combines a new database of East Coast Lows with weather impacts across the eastern seaboard. Through use of user-defined impacts thresholds and an intuitive front-end interface, this new tool provides an easy way to link East Coast Lows with their weather impacts.

show abstract

A climatology of Southern Hemisphere extratropical cyclones

Cited by 227 publications

References 17 publications

Climate perspective on the large‐scale circulation associated with the transition of the first South Atlantic hurricane

Climate perspective on the large‐scale circulation associated with the transition of the first South Atlantic hurricane

Sensitivity of the southern African circulation to dipole sea‐surface temperature patterns in the south Indian Ocean

Identifying East Coast Lows with climate hazards on the eastern seaboard

Contact Info

Product

Resources

About