Impact of Identification Method on the Inferred Characteristics and Variability of Australian East Coast Lows

Pepler, Acacia; Luca, Alejandro Di; Ji, Fei; Alexander, Lisa V.; Evans, Jason P.; Sherwood, Steven C.

doi:10.1175/mwr-d-14-00188.1

Cited by 39 publications

(59 citation statements)

References 45 publications

(72 reference statements)

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“…This approach identifies cyclones from maxima in the Laplacian of surface pressure before identifying a corresponding closed low in the pressure field and joining the individual lows into a track. This is one of the most widely used methods, and it is the method with the most skill at identifying ECLs when compared to a subjective observed data set (Pepler et al , ).…”

Section: Methodsmentioning

confidence: 99%

Australian east coast mid‐latitude cyclones in the 20th Century Reanalysis ensemble

Pepler

Fong

Alexander

2016

Intl Journal of Climatology

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Extratropical and subtropical cyclones, and their associated fronts, produce the majority of rainfall and extreme weather in the mid‐latitudes around the world. In the Southern Hemisphere in particular, where observations are sparse, we have limited knowledge of their long‐term variability and trends. While the long time period of the 20th Century Reanalysis (20CR) offers potential to assess longer‐term changes, the lack of observational data sets makes it difficult to assess its reliability. We assess the skill of the 20CR at representing mid‐latitude cyclones through a case study on the east coast of Australia. In this region, a comprehensive database has recently been developed of all severe floods between 1871 and 2012, of which >70% are associated with a coastal low‐pressure system. Through use of the full 20CR 56‐member ensemble, we are able to identify the majority of severe Australian east coast lows as early as the late 19th century, as well as recreate the cyclone tracks for some of the most severe events. The analysis shows that the full ensemble can be used for a long‐term assessment of interannual variability in cyclone frequency from at least 1911, despite large inhomogeneities in the ensemble mean pressure fields.

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Section: Methodsmentioning

confidence: 99%

Australian east coast mid‐latitude cyclones in the 20th Century Reanalysis ensemble

Pepler

Fong

Alexander

2016

Intl Journal of Climatology

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“…This is a widely used approach [e.g., Flocas et al ., ; Pinto et al ., ] and has been previously evaluated for ECLs in comparison with three other approaches in comparison to a subjective ECL database in Pepler et al . []. Of all the methods compared, this was found to have the most skill at identifying observed ECLs and was the least biased toward particular seasons or subcategories of ECLs.…”

Section: Methodsmentioning

confidence: 99%

“…(deg lat) −2 for at least 6 h (two consecutive fixes) and is located within the ECL domain (Figure ) in at least one instance, as per Pepler et al . []. A weaker intensity threshold of 0.5 hPa.…”

Section: Methodsmentioning

confidence: 99%

The influence of local sea surface temperatures on Australian east coast cyclones

et al. 2016

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Cyclones are a major cause of rainfall and extreme weather in the midlatitudes and have a preference for genesis and explosive development in areas where a warm western boundary current borders a continental landmass. While there is a growing body of work on how extratropical cyclones are influenced by the Gulf Stream and Kuroshio Current in the Northern Hemisphere, there is little understanding of similar regions in the Southern Hemisphere including the Australian east coast, where cyclones that develop close to the coast are the main cause of severe weather and coastal flooding. This paper quantifies the impact of east Australian sea surface temperatures (SSTs) on local cyclone activity and behavior, using three different sets of sea surface temperature boundary conditions during the period 2007–2008 in an ensemble of Weather Research and Forecasting Model physics parameterizations. Coastal sea surface temperatures are demonstrated to have a significant impact on the overall frequency of cyclones in this region, with warmer SSTs acting as a trigger for the intensification of weak or moderate cyclones, particularly those of a subtropical nature. However, sea surface temperatures play only a minor role in the most intense cyclones, which are dominated by atmospheric conditions.

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“…The eastern seaboard and neighboring topography tend to be poorly represented in global climate models, with higher‐resolution regional climate models improving the simulation of rainfall near areas of elevated topography [ Evans and McCabe , ; Pepler et al ., ]. This is consistent with the influence of topography on rainfall elsewhere in the world [ Tselioudis et al ., ; ter Maat et al ., ].…”

Section: Introductionmentioning

confidence: 99%

The influence of topography on midlatitude cyclones on Australia's east coast

et al. 2017

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The east coast of Australia has a relatively high frequency of midlatitude cyclones, locally known as East Coast Lows (ECLs), which can cause severe weather including widespread flooding and coastal erosion. The elevated topography close to the east coast has been hypothesized to play a role in both the genesis and impacts of cyclones in this region, but existing studies have been limited to case studies of individual events. In this paper we present the results from two 20 year simulations over the Australian region using the Weather Research and Forecasting Model and assess the results from removing all topography in the region on both mean atmospheric circulation and ECL frequency. Removing topography results in an increase in sea level pressure to the south of Australia and an increase in moisture flux convergence and rainfall near the east coast, as well as a decrease in potential vorticity to the north of the ECL region. This results in a change in the spatial distribution of cyclones, with a 37% decrease in the frequency of cyclones that develop to the south of the ECL region but a 20% increase in cyclones near the east coast. This results in little overall change in the frequency of ECLs and suggests that coarse topography is unlikely to be responsible for the difficulties in simulating coastal cyclones in global climate models.

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Impact of Identification Method on the Inferred Characteristics and Variability of Australian East Coast Lows

Cited by 39 publications

References 45 publications

Australian east coast mid‐latitude cyclones in the 20th Century Reanalysis ensemble

Australian east coast mid‐latitude cyclones in the 20th Century Reanalysis ensemble

The influence of local sea surface temperatures on Australian east coast cyclones

The influence of topography on midlatitude cyclones on Australia's east coast

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