Tropical cyclones pose a significant threat to islands in the tropical western Pacific. The extreme winds from these severe storms can cause extensive damage to housing, infrastructure and food production. As part of the Pacific Climate Change Science Program (PCCSP), Geoscience Australia assessed the wind hazard posed by tropical cyclones for 14 islands in the western Pacific and East Timor. The wind hazard was assessed for both the current climate and for the future climate under the A2 SRES emission scenario. Wind hazard maps were generated using Geoscience Australia's Tropical Cyclone Risk Model (TCRM) that applies a statistical-parametric process to estimate return period wind speeds. To obtain a robust estimate of wind hazard from a short historical track record, TCRM produces several thousand years worth of tracks that are statistically similar to the input track dataset. The model then applies a parametric wind profile to these tracks and fits a Generalized Extreme Value distribution to the maximum wind speeds at each location. To estimate how the hazard may change in the future, tracks of Tropical Cyclone-Like Vortices (TCLVs) detected in dynamically downscaled global climate model are used as input into TCRM. This is performed for four downscaled global climate models for two twenty year periods centered on 1990 and 2090 under the A2 SRES emission scenario. This study provides the first detailed assessment of the current wind hazard for this region, despite the fact that these counties are both highly exposed and vulnerable to these severe storms. The hazard climate projections should be treated with caution due to known deficiencies in the global climate models and poor agreement between models of the hazard projections. However, keeping these limitations in mind, the results suggest that the wind hazard will decrease north of 20º latitude in the South Pacific by 2090.

Tropical cyclones present a significant hazard to countries situated in the warm tropical waters of the western Pacific. These severe storms are the most costly and the most common natural disaster to affect this region (World Bank, 2006). The hazards posed by these severe storms include the extreme winds, storm surge inundation, salt water intrusion into ground water supplies, and flooding and landslides caused by the intense rainfall. Despite the high vulnerability of the islands in this region, there have been relatively few previous studies attempting to quantify the hazard from tropical cyclones in this region (i.e. Shorten et al. 2003, Shorten et al. 2005, Terry 2007). Understanding this hazard is also vital for informing climate change adaptation options. This study aims to address the limited understanding of the extreme wind hazard in this region. The wind hazard from tropical cyclones is evaluated for the current climate and projections were made to assess how this hazard may change in the future. The analysis is performed using a combination of historical tracks and downscaled climate models with Geoscience Australia's Tropical Cyclone Risk Model. The work was funded as part of the Pacific Climate Change Science Program (PCCSP), which forms the science component of the International Climate Change Adaptation Initiative (ICCAI), an Australian government initiative designed to meet high priority climate change adaptation needs of vulnerable countries in our region. This study assesses the wind hazard for the fifteen PCCSP partner countries which include 14 islands located in the West Pacific as well as East Timor.

The Regional Tropical Cyclone Hazard for Infrastructure Adaptation to Climate Change project aims to provide improved estimates of tropical cyclone wind hazard in current and future climates, for use in adaptation strategies such as wind speed-based building design criteria. The overarching goal is to make practical recommendations regarding the effect of climate change on tropical cyclones. This is most effectively achieved through evaluating the effect of climate change on extreme return period wind speeds (or severe wind hazard) across tropical Australia. In this manner, the combined effects of changes in frequency, intensity and spatial distribution of tropical cyclone events are integrated into a single quantity. Return period values are used widely in building design standards, and so represent an excellent way of informing adaptation decisions. Preceding components of the project evaluated the performance of existing general circulation models to simulate aspects of the climate important for tropical cyclones. Downscaling methods were applied to these models to create climatological simulations of tropical cyclones for input into Geoscience Australia's statistical-parametric tropical cyclone model. This, in turn, provided new estimates of severe wind hazard in both current and future climates, which may be used to make recommendations for adaptation strategies on a regional basis. Achieving this goal has required a close collaboration between the University of Melbourne, CSIRO Marine and Atmospheric Research (CMAR) and Geoscience Australia. Analysis of the general circulation models and downscaling was undertaken by University of Melbourne. The downscaling was achieved using CMAR's Conformal-Cubic Atmospheric Model (CCAM). This report details the approach used by Geoscience Australia to evaluate severe wind hazard using statistical models, and analyses the effect of climate change on severe wind hazard.

The cyclonic wind hazard over the Australian region is determined using synthetic tropical cyclone event sets derived from general circulation models (GCMs) to provide guidance on the potential impacts of climate change. Cyclonic wind hazard (defined as the return period wind speed) is influenced by the frequency, intensity and spatial distribution of tropical cyclones, all of which may change under future climate regimes due to influences such as warmer sea surface temperatures and changes in the global circulation. Cyclonic wind hazard is evaluated using a statistical-parametric model of tropical cyclones - the Tropical Cyclone Risk Model (TCRM) - which can be used to simulate many thousands of years of cyclone activity. TCRM is used to generate synthetic tracks which are statistically similar to the input event set - either an historical record or other synthetic event set. After applying a parametric wind field to the simulated tracks, we use the aggregated wind fields to evaluate the return period wind speeds for three IPCC AR4 scenarios, and make comparisons to the corresponding average recurrence interval wind speed estimates for current climate simulations. Results from the analysis of two GCMs are presented and contrasted with hazard estimates based on the historical record of tropical cyclones in the Australian region.

The current study has developed a national methodology for assessing the hazard that peak wind gusts pose to Australian communities. The key components of the hazard assessment model include the regional wind hazard and the hazard modification multipliers. The local effects on return period regional wind speeds were determined utilising remote sensing techniques, digital elevation data, and formulae presented in the wind loadings standard AS/NZS 1170.2 [1]. The estimation of the local wind speeds was evaluated by combining the local wind multipliers (terrain/height, shielding and topographic) for eight cardinal directions with the return period regional wind speeds (from [1]) on a 25 metre grid across the areas examined for each region. Here we seek to use the 500 year return period wind gust hazard from the Australian/New Zealand wind loadings standard (AS/NZS 1170.2) [1], which is a building design document that seeks to 'envelope' possible wind effects, as a proxy for the regional hazard. Arthur et al. [2] provide a new hazard assessment for the Australian continent, which we plan to utilise in future updates. Tanh and Letchford [3] compared current US, Australian/New Zealand, European and Japanese wind standards and reported that the treatment of topographic effects in these design standards is on the whole conservative. Holmes [4] proposed adjustments to remove the conservatism from the methods in the Australian wind loading standard to assess risk. These proposals and several other initiatives were adopted to improve various components of the model from its initial steps [5] towards a reliable nationally consistent wind hazard assessment for Australia.

A shallow vertical CO2 injection test was conducted over a 21 day period at the Ginninderra Controlled Release Facility in May 2011. The objective of this test was to determine the extent of lateral CO2 dispersion, breakthrough times and permeability of the soil present at the Ginninderra site. The facility is located in Canberra on the CSIRO agricultural Ginninderra Experiment Station. A 2.15m deep, 15cm stainless steel screened, soil gas sampling well was installed at the site and this was used as the CO2 injection well. The CO2 flow rate was 1.6 L/min (STP). CO2 soil effluxes (respiration and seepage) were measured continuously using a LICOR LI-8100A Automated Soil CO2 Flux System equipped with 5 accumulation chambers spaced 1m apart in a radial pattern from the injection well. These measurements were supplemented with CO2 flux spot measurements using a WestSystems portable fluxmeter. Breakthrough at 1m from the injection point occurred within 6 hrs of injection, 32hrs at 2m and after almost 5 days at 3m. The average steady state CO2 efflux was 85 ?mol/m2/s at 1m, 15 ?mol/m2/s at 2m and 5.0 ?mol/m2/s at 3m. The average background CO2 soil respiration efflux was 1.1 - 0.6 ?mol/m2/s. Under windy conditions, higher soil CO2 efflux could be expected due to pressure pumping but this is contrary to the observed results. Prolonged windy periods led to a reduction in the CO2 efflux, up to 30% lower than the typical steady state value.

A statistical downscaling approach is used to compare changes in environmental indicators of tropical cyclone characteristics between three greenhouse gas emissions scenarios in the Australian region, using results from models used for the IPCC 4th Assessment Report. Maximum potential intensity is shown to change linearly with global mean temperature, independent of emissions scenario, with a 2-3% increase per degree of global warming in Australia's tropical regions. Changes in vertical wind shear are more ambiguous, however the magnitude of changes in tropical cyclone genesis regions is small. The genesis potential index increases significantly in all scenarios, and appears to be driven by the increase in MPI. Results for Australia's tropical regions suggest that tropical cyclone intensity is highly likely to increase with global warming, while results for frequency are suggestive of a frequency increase, but less conclusive. Further work to assess frequency changes will allow quantification of changes in tropical cyclone hazard under climate change.

Knowledge of the degree of damage to residential structures expected from severe wind is used to study the benefits from adaptation strategies developed in response to expected changes in wind severity due to climate change, inform the insurance industry and provide emergency services with estimates of expected damage. A series of heuristic wind vulnerability curves for Australian residential structures has been developed for the National Wind Exposure project. In order to provide rigor to the heuristic curves and to enable quantitative assessment to be made of adaptation strategies, work has commenced by Geoscience Australia in collaboration with James Cook University and JDH Consulting to produce a simulation tool to quantitatively assess damage to buildings from severe wind. The simulation tool accounts for variability in wind profile, shielding, structural strength, pressure coefficients, building orientation, component self weights, debris damage and water ingress via a Monte Carlo approach. The software takes a component-based approach to modelling building vulnerability. It is based on the premise that overall building damage is strongly related to the failure of key components (i.e. connections). If these failures can be ascertained, and associated damage from debris and water penetration reliably estimated, scenarios of complete building damage can be assessed. This approach has been developed with varying degrees of rigor by researchers around the world and is best practice for the insurance industry. This project involves the integration of existing Australian work and the development of additional key components required to complete the process.

The National Wind Risk Assessment (NWRA), a collaboration between Geoscience Australia and the Dept. Climate Change and Energy Efficiency, has developed a computational framework to evaluate both the wind hazard and risk due to severe wind gusts (based on modelling techniques and application of the National Exposure Information System; NEXIS). A combination of tropical cyclone, synoptic and thunderstorm wind hazard estimates is used to provide a revised estimate of the severe wind hazard across Australia. The hazard modelling utilises both 'current-climate' information and also simulations forced by IPCC SRES climate change scenarios, employed to determine how the wind hazard will be influenced by climate change. The results from the current climate regional wind hazard assessment are compared with the hazard based on the existing understanding as specified in the Australian/New Zealand Wind Loading Standard (AS/NZS 1170.2, 2011). Regions were mapped where the design wind speed depicted in AS/NZS 1170.2 is significantly lower than the hazard analysis provided by this study. Regions requiring more immediate attention regarding the development of adaptation options are discussed in the context of the minimum design standards in the building code regulations. A national assessment of localised wind speed modifiers including topography, terrain and the built environment (shielding), has also been undertaken to inform the local wind speed hazard that causes damage to structures. The effects of the wind speed modifiers are incorporated through a statistical modification of the regional wind speed. We report on an assessment of severe impact and wind risk to residential houses across the Australian continent (quantified in terms of annualised loss). Considering future climate scenarios of regional severe wind hazard, we consider the changing nature of severe wind risk focusing on the Southeast Queensland and Tasmanian regions, and illustrate where the wind loading stan...

This report, 'Pacific Climate Change Science Program: Evaluation of severe wind hazard from tropical cyclones', will be delivered to CSIRO to form a subsection of the 'Climate Change in the Pacific' report. The latter will be launched in November 2011 and will constitute one of the main deliverables for the Pacific Climate Change Science Program (PCCSP). The PCCSP is part of the Australian Government's commitment through the International Climate Change Adaptation Initiative (ICCAI) to meet high priority climate change adaptation needs in vulnerable countries in the Asia-Pacific region. This report provides an evaluation of cyclonic wind hazard for the fifteen PCCSP partner countries located in the western Pacific with the one exception of East Timor. The wind hazard is estimated for both the current climate and for the future climate under an A2 emissions scenario. The current climate wind hazard is estimated by applying GA's Tropical Cyclone Risk Model (TCRM) to the historical track record. TCRM is a statistical-parametric model of tropical cyclone behaviour, enabling users to generate synthetic records of tropical cyclones representing many thousands of years of activity. TCRM is then applied to tracks of tropical cyclone-like vortices (TCLVs) detected in downscaled global climate models to determine how the cyclonic wind hazard may change in the future. The results indicated that the wind loading design standard in this region may significantly underestimate the wind hazard for the current climate. For the future climate projections, the analysis suggests that the wind hazard may decrease for countries close to the equator and near the Australian coastline but could increase for countries greater than 20 degrees poleward from the equator.