- Title
- Development of a long-term climatology of tropical 1 cyclones and depressions for the South Pacific 2 Ocean basin
- Creator
- Yeasmin, Alea
- Date
- 2023
- Type
- Text; Thesis; PhD
- Identifier
- http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/193995
- Identifier
- vital:18314
- Abstract
- Tropical cyclones (TCs) are one of the most destructive synoptic systems that can cause enormous loss of life and property damages in the South Pacific Island nations. The impact of tropical depressions (TDs, i.e., weaker systems that do not develop into TCs) can also be staggering in the region in terms of heavy flooding and landslides, but a lack of complete records (reliable data prior to 1950) often hinders research involving TD impacts. A methodology has been developed here to detect TDs in the ERA-5 (the fifth generation European Centre for Medium-Range Weather Forecasts-ECMWF atmospheric reanalysis of the global climate) and 20CR (the Twentieth Century Reanalysis) dataset using the Okubo–Weiss–Zeta parameter (OWZP) detection scheme. The new South Pacific Enhanced Archive for Tropical Cyclones dataset (SPEArTC), the Dvorak analysis of satellite-based cloud patterns over the South Pacific Ocean basin, rainfall dataset for various stations in the South Pacific and historical archives have been utilised to validate ERA5/20CR-derived TCs and TDs. Results indicate that the OWZP method shows substantial skill in capturing the realistic climatological distribution of TCs and TDs for the South Pacific Ocean in both reanalyses dataset. The 20CR-derived TCs and TDs resemble several key characteristics of the observational records, including spatial distribution of genesis locations and track shapes. This gives us confidence that the 20CR-derived long-term records of TCs and TDs can serve as an effective tool for examining historical changes in various characteristics of TCs and TDs, particularly in the context of anthropogenic climate change. Utilizing the reconstructed proxies of TCs and TDs, their climatic connections with the El Niño Southern Oscillation (ENSO), the Interdecadal Pacific Oscillation (IPO), and the combined ENSO-IPO phases have been examined. Results show clear spatial shifts in TC activity between La Niña and El Niño phases with activity in the region 1400-1700E (1700-2200E) occurring during La Niña (El Niño) events. However, when IPO is considered synergistically with ENSO phases, we found that the combination of El Niño and the positive phase of IPO (+IPO) substantially enhances TC numbers (may be artifact influence) in both domains, noting the modulation between the two phases themselves. Similarly, La Niña and the negative phase of the IPO (-IPO) is found to enhance TC numbers in 1400-1700E. It is shown for the first time that the combined phases of El Niño and +IPO account for increased TC activity, as opposed to the combined phase of La Niña and -IPO, in the eastern sub-region. Similarly, the combined phase of La Niña and +IPO, as opposed to the combined phase of El Niño and -IPO, account for increased TC activity in the western sub-region. However, unlike TCs, the patterns of ENSO variability seem to be reversed for TDs. Changes in large-scale environmental conditions, such as environmental vertical wind shear, low-level cyclonic relative vorticity, mid-tropospheric relative humidity and sea surface temperature are linked to the various modes of variability patterns and their synergistic relationships. Results can have substantial implications, particularly on the predictability of TCs and TDs associated with the two important modes of natural variability in the South Pacific.; Doctor of Philosophy
- Publisher
- Federation University Australia
- Rights
- All metadata describing materials held in, or linked to, the repository is freely available under a CC0 licence
- Rights
- Copyright Alea Yeasmin
- Rights
- Open Access
- Subject
- Tropical Cyclones; Tropical Depressions; Climatology; South Pacific Ocean
- Full Text
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