@mastersthesis {bnh-6247, title = {Simulation and analysis of surface wind fields during landfalling tropical cyclones}, volume = {Doctor of Philosophy}, year = {2019}, month = {06/2019}, school = {University of Queensland}, type = {Doctorate}, address = {Brisbane}, abstract = {

Tropical cyclones (TCs) are rotating atmospheric vortices characterised by high wind speeds thatpose a major threat to people and infrastructure in coastal communities. To minimise their impacts,the winds in the lowest part of the TC boundary layer (TCBL) must be adequately understood. Thisunderstanding enables engineers to make rational decisions around building design in these regionsand allows meteorologists to improve their forecasts. Of particular importance is how the TCBL ismodified when abrupt changes in surface terrain conditions occur, such as during landfall, which cansignificantly alter the physical structure of a TC. Although near-surface TC wind data has begun to becaptured through coordinated field campaigns in, for example, the USA and Australia, there is littleexplicit information on how the TCBL is modified during landfall or in the vicinity of other suddenchanges in land surface conditions. This thesis sets out to investigate this process through, 1) analysisof near-surface wind observations, and 2) numerical simulation of idealised TCs.To explore how near-surface turbulence is modified, the present study analysed observational TCwind records at measurement heights of 2.25 m, 3 m, 5 m, and 10 m collected during 11 TCs from theFlorida Coastal Monitoring Program (FCMP), StickNet, and the Surface Weather Information Relayand Logging network (SWIRLnet). These low-level records will be analysed to assess their turbulentcharacteristics and the response of these characteristics to sudden changes in land surface. Resultswere compared with traditional engineering models (AS/NZS1170.2, ESDU) predicting turbulencetransition in non-TC environments to assess their efficacy in TC environments. Results show thatturbulence statistics require about 2 km to reach equilibrium with the underlying terrain, independentof measurement height and upstream terrain. Engineering models tested were found to over predictturbulence intensities in a TC environment. A simple empirical model for estimating the transition ofturbulence intensity following a single change in terrain is proposed.Exploring more broadly how the mean TCBL structure is modified during TC landfall, this thesisalso uses hybrid real-idealised Weather Research and Forecasting (WRF) numerical simulations toinvestigate the mean TCBL response during landfall. This numerical modelling method combines anidealised spun-up TC and a real world environment to undertake a series of parametric simulationswhere idealised TCs impact coastlines with a range of terrain conditions. These tests systematicallyexplore how sudden changes in terrain (e.g. sea to different land surfaces) influence bulk stormcharacteristics (e.g. TC size, radius of maximum wind), surface wind footprints, and vertical TCwind profiles in different parts of simulated TCs. Generated TC wind profiles are also compared withobservational dropsonde data as well as one existing analytical model. Increased surface roughnessover land was found not to deflect the TC track prior to landfall, but was shown to lower TC intensity.Increased surface roughness was also found to reduce maximum surface level wind speeds by up to70\% within 12 hours after TC landfall. Modelled TCBL profiles over water follow a logarithmic windprofile up to the height of maximum wind speed, which increases with TC radius. TCBL profiles overland also exhibit a logarithmic wind profile but wind speeds decay faster particularly closer to thesurface.

}, keywords = {building resilience, cyclones, Emergency management, severe storms, Simulation modelling, strong winds}, author = {Thomas Kloetzke} } @article {bnh-4230, title = {Severe wind hazard preliminary assessment: Tropical Cyclone Debbie, Whitsunday Coast, Queensland, Australia}, year = {2017}, month = {03/2017}, institution = {James Cook University}, address = {Townsville}, abstract = {

Severe Tropical Cyclone Debbie was a category 4 system that made landfall near Airlie Beach (Figure 1) on the north Queensland coast at midday on the 28th of March, 2017. As part of a continuing effort to better characterize wind fields that impact communities during severe wind events, the Cyclone Testing Station (with collaborators from the Wind Research Laboratory at The University of Queensland) deployed SWIRLnet (Surface Weather Relay and Logging Network) weather stations to the region prior to Debbie{\textquoteright}s landfall. Six SWIRLnet towers (3.2 m high anemometers placed in the communities likely to be affected) collected data continuously prior to, during and after landfall. Three towers were deployed in the Ayr/Home Hill region, two in Bowen and one in Proserpine (Figure 2). This Preliminary Assessment Report details the initial observations from these towers, compares these with Bureau of Meteorology Automatic Weather Station observations, and makes some preliminary comment on the damage to structures in stormaffected communities.

}, url = {https://www.jcu.edu.au/__data/assets/pdf_file/0005/422951/TC-Debbie-Rapid-Assessment-Report_v8.pdf}, author = {Thomas Kloetzke and Korah Parackal and D. J. Smith and Richard Krupar III and Leblais, Alex and Humphreys, M and Spassiani, Alessio and M. S. Mason and David Roueche and David O Prevatt and David Henderson and Boughton, Geoffrey N.} } @article {bnh-4227, title = {Tropical Cyclone Debbie: damage to buildings in the Whitsunday Region}, number = {63}, year = {2017}, month = {06/2017}, institution = {James Cook University}, address = {Townsville}, abstract = {

Tropical Cyclone Debbie (TC Debbie) was classified by the Bureau of Meteorology (BoM) as a Category 4 cyclone and crossed the Queensland coast north east of Airlie Beach around midday on Tuesday 28 March 2017.

Before the event, the Cyclone Testing Station (CTS) deployed six mobile anemometers (SWIRLnet) in the area between Ayr and Proserpine. After the event, CTS teams investigated the performance of houses; larger residential structures such as apartments, strata properties and resort accommodation; commercial and public buildings; and sheds. The study area included the communities of Bowen, Proserpine, Airlie Beach, Hamilton Island, Dingo Beach, Wilson{\textquoteright}s Beach and Conway Beach. A wind field was developed using CTS and BoM anemometer data and showed that buildings within the study area experienced wind speeds lower than their relevant design wind speed.

CTS teams assessed the causes of damage to buildings from wind, wind-driven rainwater and storm surge. Inadequate tie-down details between battens and rafters or trusses, and between the roof structure and walls caused many of the structural failures in buildings constructed before the 1980s. Tie-down connections between roof structure and walls that had been inappropriately detailed also failed on some recently constructed buildings. Connections between verandah beams and posts on some buildings with larger verandahs also failed. \ 

This study confirmed the findings of previous damage investigations concerning the vulnerability of: windows with inadequate fixings, window and door furniture; poorly fixed flashings, gutters and soffit linings; large access doors that had not been strengthened so that they complied with AS/NZS4505; lightweight sheds; and fences.

Many occupants of newer buildings reported significant damage from wind-driven rain entering through windows and doors or under flashings even though there was no structural damage to the building. Many people reported that they mopped up water in front of windward wall windows during periods of maximum winds, which exposed them to risk of injury. Further research is required to improve performance of building elements that leak during high winds.

The storm tide generated during TC Debbie was lower than predicted because the cyclone crossed the coast after high tide. Lower-lying buildings in Wilson Beach were inundated to a height of up to 1.1 m causing damage to wall linings, built-in cupboards, floor coverings and contents. In some cases, wave action broke cladding elements and windows. Wave action and scour undercut footings in some buildings on Hamilton Island and Wilson Beach.\ 

The report provides recommendations to improve the performance of building structure and cladding systems including: adequate detailing for roof to wall connections; improved fixing of flashings, retrofitting options for older buildings; improvements in windows and door furniture under repeated wind loads; and revision of storm surge guidelines.

}, isbn = {978-0-9954470-4-2}, issn = {63}, url = {https://www.jcu.edu.au/__data/assets/pdf_file/0009/461178/TC-Debbie-report.pdf}, author = {Boughton, Geoffrey N. and Falck, D. J. and David Henderson and D. J. Smith and Korah Parackal and Thomas Kloetzke and M. S. Mason and Humphreys, M and Navaratnam, S and Bodhinayake, G and Simon Ingham and John Ginger} } @conference {bnh-2938, title = {Evaluating topographic influences on the near-surface wind field of Tropical Cyclone Ita (2014) using WRF-ARW}, booktitle = {AFAC16}, year = {2016}, month = {08/2016}, publisher = {Bushfire and Natural Hazards CRC}, organization = {Bushfire and Natural Hazards CRC}, address = {Brisbane}, abstract = {

Tropical Cyclone (TC) Ita (2014) was a major storm that affected coastal areas of Northeast Queensland. Topographic features along the coastline are known to modify the structure and intensity of such events. This study utilises the Advanced Research version of the Weather Research and Forecasting (WRF-ARW) model to investigate topographic influences during the landfall phase of TC Ita. While the removal of topography over the whole domain steers the modelled TC far away from the landfall point, removing topography from only a smaller area allowed an investigation of the topographic influence on near-surface wind conditions in that area. Flow over the region of removed topography exhibit smaller inland velocity gradients for winds flowing onshore and a sharper acceleration of winds as they moved offshore.

}, author = {Thomas Kloetzke and M. S. Mason and Richard Krupar III} }