| || || Malsale, Philip|
| || || Analysis of tropical cyclone track sinuosity in the South Pacific region using ArcGIS|
Institution: University of the South Pacific.
Award: M.A. Environmental Science
Subject: Cyclone tracks -- Oceania, Cyclones -- Tropics
Call No.: Pac QC 948 .M35 2014
Copyright:Under 10% of this thesis may be copied without the authors written permission
Abstract: Tropical cyclones (TCs) are the most destructive natural disaster in the South Pacific region. Inhabitants whose livelihoods depend on agriculture and marine resources are vulnerable to such events which can pose a threat to their fragile living environment. Patterns of TCs depend on many migratory climate drivers such as the South Pacific Convergence Zone (SPCZ), the Intertropical Convergence Zone (ITCZ), Subtropical high pressure cells and large scale circulations such as the El Niño Southern Oscillation (ENSO) and Walker circulation. These drivers in many ways present the ideal climate conditions that provide the South Pacific region with the climate it is known for. Negative impacts of TC such as flooding, storm surge and fierce winds can cause damages to the social and economic livelihoods of Pacific Island people. These impacts vary depending on the level of vulnerability of each island nation and rely on economic, social status, geographical location and size. Gathering additional information apart from TC frequency and intensity can assist in reducing related impacts and has long term benefits compared to providing aid to tropical cyclone impacted communities. Therefore, a TC database of best track was constructed with the introduction of a new metric for tropical cyclone track shape known as sinuosity values. This analysis for the South Pacific region specifically covered the Fiji Meteorological Services (FMS) Area of Responsibility (AoR) extending from the equator to latitude 25° S and longitude 160° E to 120° W from 1969-70 to 2007-08. This study has developed four sinuosity categories of tracks namely straight, slightly curved, highly curved and heavily sinuous. Analysis showed sixty eight percent of these tracks occurred in the western end of dateline and thirty two percent to the eastern end. A majority of them occurred during the months of January to February. Over the 39 year period, tracks in sinuosity category one and two peaked during 1970s and 1980s but show a declining trend thereafter while the two higher sinuous categories have increased trend in the last decade compared to the previous three decades. The same patterns were found using two case studies of the Vanuatu Area of Responsibility (AoR) and the case study of period 1990 to 2000 for FMS AoR. iv The findings of this study concluded that sinuosity values have weak correlation with ENSO indices such as the Southern Oscillation Index (SOI), Sea surface Temperature (SST – Niño 3.4) and the Coupled ENSO Index (CEI), where the latter proves to have a highest r2 value of 0.019. During El Niño years, track sinuosity values increase while during La Niña events, less sinuous tracks occur with a higher degree of dependency on the coupling of the SOI and SST. Basically, less sinuous TCs have less longevity but higher magnitude than more sinuous tracks. Moreover, the findings concluded that track sinuosity is a significant component influencing the vulnerability of Pacific Island nations to cyclone hazards. Island nations will continue to experience irregular tropical cyclone characteristics.