Kerryn Hawke

The Indian Ocean Dipole (IOD) and the El Niño Southern Oscillation (ENSO) are key modes of natural climate variability which co-occur and influence regional rainfall in Australia. This study evaluates the skill of 60 CMIP6 global climate models, including 16 pre-selected models for dynamical downscaling, in simulating the characteristics of IOD & ENSO, their inter-relationship, and their combined and independent influences on Australian rainfall. Focusing on the austral winter-spring season (JJASON) during 1950–2014, we use partial correlation & regression techniques to disentangle the influence of ENSO from the IOD-rainfall relationship and vice versa. Compared with observations, most CMIP6 models overestimate IOD & ENSO variability, frequencies of IOD & co-occurring IOD-ENSO events, and the influence of ENSO on IOD. More models reasonably capture the observed independent IOD-rainfall correlation in Southern (SA) and Southeastern (SEA) Australia than observed combined correlation, while in Eastern (EA) and Northern (NA) Australia, more models reasonably reproduce observed combined ENSO-rainfall correlation than observed independent one. A similar result emerges in regression analyses, but it is more pronounced for ENSO in EA and NA than for IOD in SA and SEA. The ranking of CMIP6 models based on four statistical skill metrics shows that each model demonstrates distinct skill variations, highlighting the importance of skill-specific analyses when evaluating relationships between IOD/ENSO and Australian rainfall. Our results emphasise the need to consider both combined and independent effects of IOD/ENSO on Australian rainfall, and our ranking of the pre-selected CMIP6 models for dynamical downscaling will be helpful to better understand biases in these regional projections for Australia.

Southwest Western Australia (SWWA), with its Mediterranean climate, has undergone a persistent drying trend since the 1970s. As such, it is often referred to as the “canary in the coal mine” of climate change. This review examines drivers of SWWA rainfall and rainfall decline, focusing on the cool season (April to October) when most rainfall occurs, and includes the influence of weather systems, modes of natural climate variability, and land‐use change. While paleo‐climate evidence shows that similar declines have occurred in the past, the current trend is at the upper end of natural climate variability, indicating an increasing influence from anthropogenic climate change. The reasons for this drying trend are complex, with research linking decreasing SWWA rainfall to a strengthening subtropical ridge and more frequent positive phases of the Southern Annular Mode resulting in fewer winter fronts reaching the region. Decreasing baroclinity has been associated with a decrease in cold front rainfall amounts and a possible shift toward increased post‐frontal showery activity. While the El Niño Southern Oscillation and Indian Ocean Dipole (IOD) have shown weak historical links to SWWA rainfall, recent trends toward more frequent positive IOD may change this association. Finally, the influence of 20th–21st century land use changes has also been identified as a contributing factor to the rainfall decline. Given the complex interplay of these drivers and the increasing influence of anthropogenic climate change on the region's rainfall, a holistic approach is becoming crucial. We provide multiple avenues for further research.

This article is categorized under: Paleoclimates and Current Trends > Modern Climate Change

South-west Western Australia (SWWA) is home to a world class grains industry that is significantly affected by periods of drought. Previous research has shown a link between the Southern Annular Mode (SAM) and rainfall in SWWA, especially during winter months. Hence, the predictability of the SAM and its relationship to SWWA rainfall can potentially improve forecasts of SWWA drought, which would provide valuable information for farmers. In this paper, focusing on the 0-month lead time forecast, we assess the bias and skill of ACCESS-S2, the Australian Bureau of Meteorology’s current operational sub-seasonal to seasonal forecasting system, in simulating seasonal rainfall for SWWA during the growing season (May–October). We then analyse the relationship between the SAM and SWWA precipitation and how well this is captured in ACCESS-S2 as well as how well ACCESS-S2 forecasts the monthly SAM index. Finally, ACCESS-S2 rainfall forecasts and the simulation of SAM are assessed for a case study of extreme drought in 2010. Our results show that forecasts tend to have greater skill in the earlier part of the season (May–July). ACCESS-S2 captures the significant inverse SAM–rainfall relationship but underestimates its strength. The model also shows overall skill in forecasting the monthly SAM index and simulating the MSLP and 850-hPa wind anomaly patterns associated with positive and negative SAM phases. However, for the 2010 drought case study, ACCESS-S2 does not indicate strong likelihoods of the upcoming dry conditions, particularly for later in the growing season, despite predicting a positive (although weaker than observed) SAM index. Although ACCESS-S2 is shown to skillfully depict the SAM–SWWA rainfall relationship and generally forecast the SAM index well, the seasonal rainfall forecasts still show limited skill. Hence it is likely that model errors unrelated to the SAM are contributing to limited skill in seasonal rainfall forecasts for SWWA, as well as the generally low seasonal-timescale predictability for the region.

Natural hazard reviews reveal increases in disaster impacts nowhere more pronounced than in coastal settlements. Despite efforts to enhance hazard resilience, the common trend remains to keep producing disaster prone places. This paper explicitly explores hazard versus multi-hazard concepts to illustrate how different conceptualizations can enhance or reduce settlement resilience. Understandings gained were combined with on-the-ground lessons from earthquake and flooding experiences to develop of a novel 'first cut' approach for analyzing key multi-hazard interconnections, and to evaluate resilience enhancing opportunities. Traditional disaster resilience efforts often consider different hazard types discretely. However, recent events in Christchurch, a New Zealand city that is part of the 100 Resilient Cities network, highlight the need to analyze the interrelated nature of different hazards, especially for enhancing lifelines system resilience. Our overview of the Christchurch case study demonstrates that seismic, hydrological, shallow-earth, and coastal hazards can be fundamentally interconnected, with catastrophic results where such interconnections go unrecognized. In response, we have begun to develop a simple approach for use by different stakeholders to support resilience planning, pre and post disaster, by: drawing attention to natural and built environment multi-hazard links in general; illustrating a 'first cut' tool for uncovering earthquake-flooding multi-hazard links in particular; and providing a basis for reviewing resilience strategy effectiveness in multi-hazard prone environments. This framework has particular application to tectonically active areas exposed to climate-change issues.

Christchurch city’s primary natural hazard exposure, arguably, is to various kinds of flooding and inundation. Recently the Canterbury Earthquake Sequence (CES) reshaped many aspects of the city’s natural and built environment, with significant changes to the flood-scape. In response to the CES impacts on the city’s waterways and drainage network, the Christchurch City Council (CCC) established the Land Drainage Recovery Programme (LDRP) to consider these impacts on flood risk, and to identify and implement responses to reduce these risks.Cited on a low-lying coastal plain in a seismically active setting, large parts of the city are subject to the effects of, and interactions between, multiple types of natural hazard, with a particular concentration of multi-hazard risk in coastal and riverside areas. This challenging circumstance gives rise to the question: How do we make decisions about flood management in a multi-hazard environment? To address this question, the Council initiated an investigation that aims to develop flood management plans for eastern Christchurch involving a range of sustainable, adaptable and resilient flood management options within a multi -hazard context. The hazards examined in this assessment included fluvial, pluvial and coastal flooding; the likely impacts of climate change on these including the impacts of sea level rise on coastal inundation, erosion and rising groundwater; and the potential cascading effects of future earthquakes (subsidence, liquefaction, lateral spread, ground shaking) and tsunami on flooding risks. The assessment approach employed involves three stages: (i) understanding the multiple hazards and multi-hazard interactions affecting the city’s exposure to flood risks in terms of spatial co-location, temporal coincidence and cascading impacts; (ii) undertaking targeted studies to address key gaps in our understanding of these multiple hazards; and (iii) developing a range of potential management options including engineering, planning and policy responses, within an adaptive planning pathways framework. Stage one has been completed, the stage two studies have largely been completed, and considerable work effort is being undertaken to address the challenges in proceeding to stage three of the study. This presentation overviews the overall approach of the project and presents the findings of the stage one analysis of multi-hazard interactions.

Completing a PhD is difficult. Add a major earthquake sequence and general stress levels become much higher. Caring for some of the nonacademic needs of doctoral scholars in this environment becomes critical to their scholarly success. Yet academic supervisors, who are in the same challenging environment, may already be stretched to capacity. How then do we increase care for doctoral scholars? While it has been shown elsewhere that supportive and interactive department cultures reduce attrition rates, little work has been done on how exactly departments might create these supportive environments: the focus is generally on the individual actions of supervisors, or the individual quality of students admitted. We suggest that a range of actors and contingencies are involved in journeying toward a more caring collective culture. We direct attention to the hybridity of an emerging caring collective', in which the assembled actors are not only students' and staff', but also bodies, technologies, objects, institutions, and other nonhuman actors including tectonic plates and earthquakes. The concept of the hybrid caring collective is useful, we argue, as a way of understanding the distributed responsibility for the care of doctoral scholars, and as a way of stepping beyond the student/supervisor blame game.

Convective storms can cause significant disruption to human activity, danger to life and damage to property and livelihood. Hazards include heavy rain and associated flash flooding, lightning and associated wild fires, hail, strong wind gusts and tornadoes. Convective storms in New Zealand occur, on average, fifteen to twenty days per year in northern and western parts of the country, while on the east coast of the South Island the average is commonly less than five occurrences per year. While thunderstorms are infrequent in New Zealand when compared to countries such as Australia and the USA, associated hazards like lightning still pose a risk to humans and so a better understanding of spatial and temporal patterns of severe convective activity is valuable to assist in decreasing associated risk factors. A twelve year ground-based lightning dataset was used as a proxy for severe convective activity in this research as, unlike AWS, radar or satellite-based lightning detection data, dataset encompasses the whole New Zealand region The main aims of this research, therefore, were to produce a spatial lightning climatology of New Zealand investigate the hypothesis that convective triggers leading to lightning activity in New Zealand are associated with different synoptic and local situations depending on time and geographic location. The purpose of this poster is to present the results of this high-resolution lightning climatological research in order to aid a better understanding of thunderstorm occurrence across New Zealand. There are different mechanisms for lightning. For example, lightning to the west of the Southern Alps in the South Island can occur under any weather situation at any time of the day or night and in any season of the year. Peak lightning occurrences are over and to the west of the seaward most mountain range, regardless of elevation. Lightning occurrence is highly influenced by topography in many places, most notably over the South Island, where the Southern Alps acts as a barrier. Applications include risk assessment, where research outcomes can be used to pinpoint the most vulnerable localities / regions for lightning hazards. This can be utilised by groups interested in weather-related risk assessment (e.g. local councils) to help mitigate injury, death, damage to property and livelihood. In addition, a detailed knowledge of where and when lightning occurs can also strengthen the advancement of nowcasting and forecasting techniques.

Convective storms can cause significant disruption to human activity, danger to life and damage to property and livelihood. Hazards include heavy rain and associated flash flooding, lightning and associated wild fires, hail, strong wind gusts and tornadoes. Convective storms in New Zealand occur, on average, fifteen to twenty days per year in northern and western parts of the country, while on the east coast of the South Island the average is commonly less than five occurrences per year. While thunderstorms are infrequent in New Zealand when compared to countries such as Australia and the USA, associated hazards like lightning still pose a risk to humans and so a better understanding of spatial and temporal patterns of severe convective activity is valuable to assist in decreasing associated risk factors. A twelve year ground-based lightning dataset was used as a proxy for severe convective activity in this research as, unlike AWS, radar or satellite-based lightning detection data, dataset encompasses the whole New Zealand The main aims of this research, therefore, were to produce a spatial lightning climatology of New Zealand investigate the hypothesis that convective triggers leading to lightning activity in New Zealand are associated with different synoptic and local situations depending on time and geographic location. The purpose of this poster is to present the results of this high-resolution lightning climatological research in order to aid a better understanding of thunderstorm occurrence across New Zealand. There are different mechanisms for lightning. For example, lightning to the west of the Southern Alps in the South Island can occur under any weather situation at any time of the day or night and in any season of the year. Peak lightning occurrences are over and to the west of the seaward most mountain range, regardless of elevation. Lightning occurrence is highly influenced by topography in many places, most notably over the South Island, where the Southern Alps acts as a barrier. Applications include risk assessment, where research outcomes can be used to pinpoint the most vulnerable localities / regions for lightning hazards. This can be utilised by groups interested in weather-related risk assessment (e.g. local councils) to help mitigate injury, death, damage to property and livelihood. In addition, a detailed knowledge of where and when lightning occurs can also strengthen the advancement of nowcasting and forecasting techniques.

Retrospective analysis of severe convective storms and associated lightning is useful for forecasting these extreme events. However, until recently it has been difficult to obtain sufficient datasets for long-term analysis. The use of lightning as a proxy for severe convection has become feasible in the past decade as global and regional lightning detection datasets have become of sufficient longevity for climatological investigation. A twelve-year (2001-2012) climatological analysis of positive and negative cloud-to-ground discharge (+/-CGD) lightning in New Zealand was completed using data from a network of sensors maintained by the New Zealand Meteorological Service. A spatio-temporal lightning analysis in relation to diurnal and seasonal scales, Kidson’s synoptic types and variability introduced by SAM and ENSO was carried out. Results show that -CGD are largely dominant, with clear inter-annual and seasonal variability and topography shaping their spatial variability. Western areas, especially the West Coast of the South Island, experience the highest +/-CGD. They primarily occur under trough situations in response to orographic triggers and can occur at any time of the day or year, although more frequently during spring and autumn months (Sep-Dec, Mar-Jun). Eastern areas are most likely to experience lightning activity during summer (Nov-Feb), have a strong diurnal pattern and are linked to interactions between post-frontal unstable southwesterly flow regimes and smaller scale sea breeze convergence mechanisms. The central North Island also has a strong diurnal pattern, with lightning most likely to occur during the afternoon in the summer months (Dec-Jan). These primarily occur during blocking synoptic conditions, where slack air gradients and strong daytime heating produce small-scale wind interactions, local convection and the production of severe convective storm cells. These results have assisted in the construction of a lightning climatology, while subsequent investigation of the atmospheric processes involved is underway using a meso-scale modeling system (WRF-ARW).