- Title
- An investigation of Indo-Pacific climate variability and tropical cyclogenesis in the Southwest Pacific
- Creator
- Magee, Andrew David
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2016
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Tropical cyclones (TCs) pose a significant risk to the nations and territories of the southwest Pacific (SWP) (0°-35°S, 135°E-120°W). Lives, economies and infrastructure are all vulnerable to the impact of TCs, exacerbated by the SWPs isolation, slow economic growth and limited adaptive capacity. While our understanding of TCs in the SWP has improved with time, knowledge gaps remain with respect to better quantifying the link between Indo-Pacific climate variability and SWP TCs. As such, this thesis investigates the role of interannual and interdecadal Indo-Pacific climate processes, including El Niño/Southern Oscillation (ENSO), ENSO Modoki, the Interdecadal Pacific Oscillation (IPO) and Indian Ocean sea surface temperature (SST) variability in spatially and temporally modulating SWP tropical cyclogenesis (TC genesis). An initial investigation of SWP TC databases confirms that the South Pacific Enhanced Archive of Tropical Cyclones (SPEArTC) is the most complete repository of TC data for the SWP and as such has been adopted for use throughout this Thesis. Further, no statistical, temporal or spatial evidence was found to discredit the inclusion of SPEArTC data from 1945 for specific applications (which was previously limited from 1970-onwards). The extension of the ‘reliable’ TC record forms an important step in quantifying the impact of interdecadal climate variability on SWP TCs. This in turn increases TC sample size and improves our certainty of any observed relationships between climate variability and SWP TC genesis. Throughout the Thesis, interannual climate variability is shown to significantly modulate the location of SWP TC genesis. For example, the well-known northeast/southwest modulation of TCs by ENSO was confirmed using the longer dataset. Importantly, new insights were also gained in terms of the IPO modulating SWP TC genesis. In particular, IPO positive (negative) epochs were found to result in the modulation of SWP TC genesis towards the northeast (southwest). The phase of the IPO was also found to have a marked impact on multidecadal climate variability, particularly on the relationship between interannual processes (ENSO and ENSO Modoki) and SWP TC genesis, acting to either amplify the effect of the individual driver (during times when modes are ‘in phase’), or dominate the modulation (during ‘out of phase’ combinations). New insights into the influence of Indian Ocean SSTs and the modulation of SWP TC genesis were also found. Anomalously warm (cool) Indian Ocean SSTs were shown to result in the migration of SWP TC genesis towards the east/northeast (south/southwest). While Indian Ocean SST variability is significantly correlated with ENSO, these modulations were also found to occur during ENSO neutral phases. Valuable insights into the combined impact of ENSO and Indian Ocean SST variability on SWP TC genesis are also uncovered, as the phase of ENSO was found to enhance the spatial modulation of individual Indian Ocean driver impacts, or create a hybrid modulation of the two. Finally, a multivariate statistical model is developed to model TC counts in the SWP, western SWP and eastern SWP regions. Using indices indicative of Indo-Pacific climate variability and dynamic/thermodynamic parameters conducive for TC genesis, the model offers a considerable improvement over climatology (up to 37%). Using the model to hindcast SWP TC counts to 1872 uncovered semicentennial oscillations, with 25-35 year cycles of above average TC counts followed by a 20-30 year cycle of below average TC counts. Identification of longer-term TC variability has significant implications for future projections of TC activity. The significant skill of these models also highlights the potential to improve existing TC forecasting tools (both statistical and dynamical forecasting schemes) currently used in the SWP region. Findings from this Thesis emphasize the importance of considering the interactions of both interannual and interdecadal climate processes derived from the Pacific and Indian Ocean regions. These insights may inform and improve quantification of timing, frequency and location of TC genesis which may be used to optimise TC outlooks for the SWP.
- Subject
- tropical Cyclone; ENSO; cyclogenesis; SPEArTC; climate; variability; Southwest Pacific; IPO; Indian Ocean dipole
- Identifier
- http://hdl.handle.net/1959.13/1321913
- Identifier
- uon:24477
- Rights
- Copyright 2016 Andrew David Magee
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 33 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 261 KB | Adobe Acrobat PDF | View Details Download |