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Showing papers in "Australian Meteorological and Oceanographic Journal in 2012"


Journal ArticleDOI
TL;DR: A new world extreme three-second average wind gust record of 113.3 m s−1, measured on Barrow Island, Australia, during the passage of tropical cyclone Olivia in April 1996, and the public and media reaction to that verification is described in this paper.
Abstract: This paper details the event, recording instrumentation, and verification of a new world extreme three-second average wind gust record of 113.3 m s–1, measured on Barrow Island, Australia, during the passage of tropical cyclone Olivia in April 1996, and the public and media reaction to that verification. This record supersedes the previous extreme of 103.3 m s–1 measured at the Mount Washington Observatory in New Hampshire, USA, in April 1934. Members of a World Meteorological Organization evaluation committee critically reviewed the data of the Olivia event, determined the Barrow Island wind measurement was valid and established the record. With the announcement of the record, interesting public reaction has occurred and is discussed, as well as the concept of more detailed classification of wind extremes. Although Olivia now holds the record for having the highest wind gust ever measured, this record doesn’t imply that Olivia is the most intense cyclone recorded. However, planners should be aware that extreme gusts well above the ‘typical’ gusts quoted on the intensity scale are possible for tropical cyclones, particularly for category 4 and 5 tropical cyclones.

10 citations




Journal ArticleDOI
TL;DR: In this paper, the authors used data up to 2011 to determine whether changes in rainfall averaged across Australia can account for the continued warming of Australian average temperature, including the very long drought that affected much of southern Australia over the twelve years up to 2010.
Abstract: Nicholls and Larsen (2011) demonstrated that daily maximum temperatures at Melbourne, Australia, tended to be higher during and following droughts than otherwise. Studies in Europe and elsewhere also have demonstrated that low soil moisture associated with a drought is a likely contributor to high temperatures (eg. Durre et al. 2000; Seneviratne at al. 2006, 2010; Fischer et al. 2007a, b; Dole et al. 2011). Temperatures averaged over Australia have been warming since the middle of the twentieth century (Fig. 1; CSIRO & Bureau of Meteorology 2012). The question arises, therefore, as to whether or not changes in drought and rainfall could be the explanation for this warming. Since droughts exacerbate daily maximum temperatures (e.g. Nicholls and Larsen 2011), does this mean that a trend towards lower rainfall might be the cause of the warming observed across Australia? Coughlan (1979) and Nicholls et al. (1996) demonstrated that Australian annual mean temperature was negatively correlated with annual mean rainfall. Power et al. (1998) demonstrated that this out-of-phase relationship occurred throughout the country, and not just in Australia-wide averages. Nicholls et al (1996) identified, using data up to 1992, that the Australia-wide average of mean daily maximum temperature appeared to be increasing relative to the temperatures expected from the rainfall–temperature relationship. Nicholls (2003) extended the Nicholls et al. (1996) study by including data up to 2002 and demonstrated that this ‘anomalous’ warming had continued up to that year. Others (eg. Cai and Cowan 2008; Karoly and Braganza 2005) have used the changing relationship between temperature and rainfall to maximise the signal-to-noise ratio by removing the fraction of the temperature variability associated with rainfall variations and changes. The residual was then the basis for an attribution study aimed at identifying the physical cause of the warming. Cai et al. (2010) also demonstrated that the warming trend (at least in the Murray–Darling Basin) could not be explained by changes in cloudiness. In this note, data up to 2011 have now been used to determine whether changes in rainfall averaged across Australia can account for the continued warming of Australian average temperature. This period includes the very long drought that affected much of southern Australia over the twelve years up to 2010. If droughts are a factor causing warming, then this extended drought may have at least contributed to the long-term warming across the country.

5 citations


Journal ArticleDOI
TL;DR: Tobin et al. as mentioned in this paper used the mean sea-level pressure (MSLP) from both Darwin and Tahiti to calculate the Troup Southern Oscillation Index (SOI) for the period January 2008 to August 2011.
Abstract: Southern Oscillation Index The Troup Southern Oscillation Index1 (SOI) for the period January 2008 to August 2011 is shown in Fig. 1, together with a five-month weighted moving average. The SOI is calculated using the mean sea-level pressure (MSLP) from both Darwin and Tahiti. Sustained departures of the SOI from neutral values (generally considered to be between +8 and –8) can reflect El Niño – Southern Oscillation (ENSO) events; sustained positive values may indicate a La Niña event, while sustained negative values may indicate an El Niño event. Commencing in autumn 2010, values of the SOI were strongly positive for most of the period between April 2010 and April 2011, with either new record monthly SOI values, or near-record values, in numerous months (Lovitt 2011, Imielska 2011, Tobin and Skinner 2012). Following the 2010– 11 La Niña event, one of the strongest on record, the 30-day SOI returned to neutral values during May 2011, and stayed within neutral to mildly positive values throughout winter 2011. Monthly SOI values for the season were +0.2 for June, +10.7 for July, and +2.1 for August. The winter MSLP values at both Darwin and Tahiti were generally above the long-term average, although the anomaly values were stronger at Tahiti, and were largely responsibly for the positive SOI values observed during the season. The monthly anomalies for June, July, and August Corresponding author address: Skie Tobin, National Climate Centre, Bureau of Meteorology, Australia, GPO Box 1289, Melbourne Vic. 3001, Australia. Email: s.tobin@bom.gov.au Southern hemisphere circulation patterns and associated anomalies for the austral winter 2011 are reviewed, with emphasis given to the Pacific Basin climate indicators and Australian rainfall and temperature patterns. Winter 2011 saw a brief period of neutral El Niño – Southern Oscillation (ENSO) conditions following the 2010–11 La Niña’s conclusion in the preceding autumn, before the equatorial Pacific was again dominated by cooling leading into the formation of the 2011–12 La Niña during spring. Most ENSO indicators were consistent with this, with values generally on the cool side of neutral, but not yet showing a consistent La Niña signal, despite the substantial volume of cooler-than-usual water present below the surface of the central and eastern equatorial Pacific by late winter. The Indian Ocean Dipole entered a positive phase from late winter 2011, with surface temperatures in the Arabian Sea generally warmer than average, while water off the coast of Sumatra was cooler than average. Averaged over Australia, winter rainfall was slightly below average. Maximum temperatures were above to very much above average across southern Australia, while minimum temperatures were below to very much below average across most of the north and above to very much above average for Tasmania, the southern half of Western Australia, and coastal areas of the southeastern mainland. For maximum temperatures, winter 2011 was in the top five warmest winters on record for South Australia and the southeastern states.

5 citations



Journal ArticleDOI
TL;DR: The nature of the recent rainfall decrease in the vicinity of Melbourne, southeastern Australia, and its impact on soil water balance and groundwater recharge was investigated in this paper, where the authors focused on the impact of rainfall decrease on groundwater recharge.
Abstract: The nature of the recent rainfall decrease in the vicinity of Melbourne, southeastern Australia, and its impact on soil water balance and groundwater recharge

3 citations





Journal ArticleDOI
TL;DR: In the early 1990s, the Australian Bureau of Meteorology (BOM) deployed two bottom pressure recorders (BPRs) on the seafloor to detect tsunamis in the Tasman Sea as mentioned in this paper.
Abstract: An essential element in the provision of tsunami warnings is the ability to detect tsunamis through changes in sea level. This is important because not all earthquakes cause tsunamis, even those occurring along subduction zones, where tsunamigenic earthquakes are most likely to occur. Furthermore, it is not currently possible to determine in real time, from seismic data alone, whether an earthquake has generated a tsunami or not. There are a number of possible instruments that can be used for observing tsunamigenerated sea-level variability, such as coastal radars (e.g. Heron et al. 2008) and satellite altimeters (Ablain et al. 2006). The two main techniques used operationally within the Australian region for the detection of tsunamis are coastally based tide gauges and open-ocean-based tsunameters. A tsunameter consists of a bottom pressure recorder (BPR) installed on the sea floor, in deep water (typically deeper than 3000 m) which communicates via an acoustic link with a moored surface buoy. The BPR records pressure at fifteensecond intervals which is then converted to a change in sea surface height, with a precision of one millimetre (Meinig et al. 2005). As part of the Australian Tsunami Warning System project, the Australian Bureau of Meteorology (the Bureau) significantly expanded its sea-level observing network, including a mix of tide gauges and tsunameters. Two tsunameters were initially deployed in the Tasman Sea. These were placed in order to detect and provide warning guidance for tsunamis caused by earthquakes on the Puysegur subduction zone, located to the southwest of New Zealand (see Fig. 1). Over the past 25 years, there have been six earthquakes in this region with magnitudes over Mw = 6.0. These earthquakes occurred in 1988 (Mw 6.7), 1989 (Mw 6.4), 1993 (Mw 7.0), 2000 (Mw 6.1), 2003 (Mw 7.2) and 2009 (Mw 7.8) (Uslu et al. 2011). For the initial deployment of the tsunameters, both were placed near a single location deemed to be ‘optimal’, with a separation of approximately 70 km (Greenslade 2007). There were a number of reasons for placing them near each other. Firstly, and predominantly, one of the tsunameters was an experimental Easy-To-Deploy Deep-ocean Assessment and