School of Earth Sciences - Research Publications

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    Seasonal dependence of rainfall extremes in and around Jakarta, Indonesia
    Lestari, S ; King, A ; Vincent, C ; Karoly, D ; Protat, A (Elsevier, 2019)
    This study investigates the interannual, seasonal, and intraseasonal variation in rainfall extremes (REs) in Jakarta and surroundings. We used datasets of daily rainfall at three sites at coastal, inland and mountainous environments during 1974–2016 (42 years), Sea Surface Temperature, 850-hPa zonal and meridional winds, and Outgoing Longwave Radiation during 1979–2016 (37 years). The results show that intensity and frequency of REs, and their relative contribution to the total rainfall, have strong relationships with the Indian Ocean Dipole and El Niño Southern Oscillation in the dry season (Jun–Nov) but weak relationships in the wet season (Dec–May) at all sites. During active Madden-Julian Oscillation (MJO) period, the daily average rainfall and the number of RE days relative to all days show strong variation between MJO phases at all sites and the MJO signature differs between the three stations. At the coastal and inland sites, there is a less marked variation of the number of RE events relative to all days with MJO phases. Compared to lower altitudes, the high-altitude station has a greater number of RE events relative to all days in the wet season and a lower intensity of REs relative to total rainfall amount in the dry season. The results of the study suggest that the REs vary in each station due to highly localised differences in responses to large-scale conditions.
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    Amplification of risks to water supply at 1.5°C and 2°C in drying climates: a case study for Melbourne, Australia
    Henley, BJ ; Peel, MC ; Nathan, R ; King, AD ; Ukkola, AM ; Karoly, DJ ; Tan, KS (IOP Publishing, 2019-08-02)
    Human-induced climate change poses a major threat to the reliable water supply in many highly populated regions. Here we combine hydrological and climate model simulations to evaluate risks to the water supply under projected shifts in the climate at the Paris Agreement warming levels. Modelling the primary surface water sources for Melbourne, Australia, we project that the risk of severe water supply shortage to the climate-dependent portion of the system increases substantially as global warming increases from 1.5 °Cto 2.0 °C. Risks are further exacerbated by increases in water demand but substantially ameliorated by supply augmentation from desalination.Wedemonstrate that reductions in precipitation, rising temperature and growth in water demand combine to substantially amplify the risk of severe water supply shortage under near-term global warming in the absence of a climate-independent supply. This risk amplification is not as apparent in assessments based on meteorological drought alone. With the diminishing opportunity of meeting the 1.5 °CParis target, our study highlights the need to accelerate greenhouse gas mitigation efforts to reduce risks to climate dependent water supply systems.
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    Reduced heat exposure by limiting global warming to 1.5 degrees C
    King, AD ; Donat, MG ; Lewis, SC ; Henley, BJ ; Mitchell, DM ; Stott, PA ; Fischer, EM ; Karoly, DJ (Springer Nature, 2018-07-01)
    The benefits of limiting global warming to the lower Paris Agreement target of 1.5 °C are substantial with respect to population exposure to heat, and should impel countries to strive towards greater emissions reductions.
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    The weather@home regional climate modelling project for Australia and New Zealand
    Black, MT ; Karoly, DJ ; Rosier, SM ; Dean, SM ; King, AD ; Massey, NR ; Sparrow, SN ; Bowery, A ; Wallom, D ; Jones, RG ; Otto, FEL ; Allen, MR (COPERNICUS GESELLSCHAFT MBH, 2016-09-15)
    Abstract. A new climate modelling project has been developed for regional climate simulation and the attribution of weather and climate extremes over Australia and New Zealand. The project, known as weather@home Australia–New Zealand, uses public volunteers' home computers to run a moderate-resolution global atmospheric model with a nested regional model over the Australasian region. By harnessing the aggregated computing power of home computers, weather@home is able to generate an unprecedented number of simulations of possible weather under various climate scenarios. This combination of large ensemble sizes with high spatial resolution allows extreme events to be examined with well-constrained estimates of sampling uncertainty. This paper provides an overview of the weather@home Australia–New Zealand project, including initial evaluation of the regional model performance. The model is seen to be capable of resolving many climate features that are important for the Australian and New Zealand regions, including the influence of El Niño–Southern Oscillation on driving natural climate variability. To date, 75 model simulations of the historical climate have been successfully integrated over the period 1985–2014 in a time-slice manner. In addition, multi-thousand member ensembles have also been generated for the years 2013, 2014 and 2015 under climate scenarios with and without the effect of human influences. All data generated by the project are freely available to the broader research community.
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    THE ROLES OF CLIMATE CHANGE AND EL NINO IN THE RECORD LOW RAINFALL IN OCTOBER 2015 IN TASMANIA, AUSTRALIA
    Karoly, DJ ; Black, MT ; Grose, MR ; King, AD (AMER METEOROLOGICAL SOC, 2016-12)
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    Spatial and temporal agreement in climate model simulations of the Interdecadal Pacific Oscillation
    Henley, BJ ; Meehl, G ; Power, SB ; Folland, CK ; King, AD ; Brown, JN ; Karoly, DJ ; Delage, F ; Gallant, AJE ; Freund, M ; Neukom, R (Institute of Physics (IoP), 2017-04-01)
    Accelerated warming and hiatus periods in the long-term rise of Global Mean Surface Temperature (GMST) have, in recent decades, been associated with the Interdecadal Pacific Oscillation (IPO). Critically, decadal climate prediction relies on the skill of state-of-the-art climate models to reliably represent these low-frequency climate variations. We undertake a systematic evaluation of the simulation of the IPO in the suite of Coupled Model Intercomparison Project 5 (CMIP5) models. We track the IPO in pre-industrial (control) and all-forcings (historical) experiments using the IPO tripole index (TPI). The TPI is explicitly aligned with the observed spatial pattern of the IPO, and circumvents assumptions about the nature of global warming. We find that many models underestimate the ratio of decadal-to-total variance in sea surface temperatures (SSTs). However, the basin-wide spatial pattern of positive and negative phases of the IPO are simulated reasonably well, with spatial pattern correlation coefficients between observations and models spanning the range 0.4–0.8. Deficiencies are mainly in the extratropical Pacific. Models that better capture the spatial pattern of the IPO also tend to more realistically simulate the ratio of decadal to total variance. Of the 13% of model centuries that have a fractional bias in the decadal-to-total TPI variance of 0.2 or less, 84% also have a spatial pattern correlation coefficient with the observed pattern exceeding 0.5. This result is highly consistent across both IPO positive and negative phases. This is evidence that the IPO is related to one or more inherent dynamical mechanisms of the climate system.
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    Limited evidence of anthropogenic influence on the 2011-12 Extreme Rainfall over Southeast Australia
    King, AD ; Lewis, SC ; Perkins, SE ; Alexander, LV ; Donat, MG ; Karoly, DJ ; Black, MT ( 2013-09-01)
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    INCREASED LIKELIHOOD OF BRISBANE, AUSTRALIA, G20 HEAT EVENT DUE TO ANTHROPOGENIC CLIMATE CHANGE
    King, AD ; Black, MT ; Karoly, DJ ; Donat, MG (AMER METEOROLOGICAL SOC, 2015-12)
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    Extraordinary heat during the 1930s US Dust Bowl and associated large-scale conditions
    Donat, MG ; King, AD ; Overpeck, JT ; Alexander, LV ; Durre, I ; Karoly, DJ (SPRINGER, 2016-01)