School of Geography, Earth and Atmospheric Sciences - Research Publications

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    Communicating the link between climate change and extreme rain events
    King, ADD ; Reid, KJJ ; Saunders, KRR (Nature Research, 2023)
    Extreme rainfall events are often linked to climate change based on simple thermodynamic arguments, but complex dynamic processes also play a role. Scientists have a responsibility to ensure they provide accurate information to the media and public.
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    Atmospheric water vapour transport in ACCESS-S2 and the potential for enhancing skill of subseasonal forecasts of precipitation
    Reid, KJ ; Hudson, D ; King, AD ; Lane, TP ; Marshall, AG (WILEY, 2024-01)
    Abstract Extended warning of above‐average and extreme precipitation is valuable to a wide range of stakeholders. However, the sporadic nature of precipitation makes it difficult to forecast skilfully beyond one week. Subseasonal forecasting is a growing area of science that aims to predict average weather conditions multiple weeks in advance using dynamical models. Building on recent work in this area, we test the hypothesis that using large‐scale horizontal moisture transport as a predictor for precipitation may increase the forecast skill of the above‐median and high‐precipitation weeks on subseasonal time‐scales. We analysed retrospective forecast (hindcast) sets from the Australian Bureau of Meteorology's latest operational subseasonal‐to‐seasonal forecasting model, ACCESS‐S2, to compare the forecast skill of precipitation using integrated water vapour transport (IVT) as a proxy, compared to using precipitation forecasts directly. We show that ACCESS‐S2 precipitation generally produces more skilful forecasts, except over some regions where IVT could be a useful additional diagnostic for warning of heavy precipitation events.
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    Tropical, Subtropical, and Extratropical Atmospheric Rivers in the Australian Region
    Reid, KJ ; King, AD ; Lane, TP ; Hudson, D (AMER METEOROLOGICAL SOC, 2022-05)
    Abstract Studies of atmospheric rivers (ARs) over Australia have, so far, only focused on northwest cloudband–type weather systems. Here we perform a comprehensive analysis of AR climatology and impacts over Australia that includes not only northwesterly systems, but easterly and extratropical ARs also. We quantify the impact of ARs on mean and extreme rainfall including assessing how the origin location of ARs can alter their precipitation outcomes. We found a strong relationship between ARs and extreme rainfall in the agriculturally significant Murray–Daring basin region. We test the hypothesis that the tropical and subtropical originating ARs we observe in Australasia differ from canonical extratropical ARs by examining the vertical structure of ARs grouped by origin location. We found that in the moisture abundant tropics and subtropics, wind speed drives the intensity of ARs, while in the extratropics, the strength of an AR is largely determined by moisture availability. Finally, we examine the modulation of AR frequency by different climate modes. We find weak (but occasionally significant) correlations between ARs frequency and El Niño–Southern Oscillation, the Indian Ocean dipole, and the southern annular mode. However, there is a stronger relationship between the phases of the Madden–Julian oscillation and tropical AR frequency, which is an avenue for potential skill in forecasting ARs on subseasonal time scales.
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    Variability of Jakarta Rain-Rate Characteristics Associated with the Madden-Julian Oscillation and Topography
    Lestari, S ; King, A ; Vincent, C ; Protat, A ; Karoly, D ; Mori, S (AMER METEOROLOGICAL SOC, 2022-08)
    Abstract Research on the interaction between the Madden–Julian oscillation (MJO) and rainfall around Jakarta is limited, although the influence of the MJO on increased rainfall is acknowledged as one of the primary causes of flooding in the region. This paper investigates the local rainfall response around Jakarta to the MJO. We used C-band Doppler radar in October–April during 2009–12 to study rain-rate characteristics at much higher resolution than previous analyses. Results show that the MJO strongly modulates rain rates over the region; however, its effect varies depending on topography. During active phases, MJO induces a high rain rate over the ocean and coast, meanwhile during suppressed phases, it generates a high rain rate mainly over the mountains. In phase 2 of the MJO we find the strongest increase in mean and extreme rain rate, which is earlier in the MJO cycle than most studies reported, based on lower-resolution data. This higher rain rate is likely due to increases in convective and stratiform activities. The MJO promotes more stratiform rain once it resides over Indonesia. In phase 5, over the northwestern coast and western part of the radar domain, the MJO might bring forward the peak of the hourly rain rate that occurs in the early morning. This is likely due to a strong westerly flow arising from MJO superimposed westerly monsoonal flow, blocked by the mountains, inducing a strong wind propagating offshore resulting in convection near the coast in the morning. Our study demonstrates the benefits of using high-resolution radar for capturing local responses to the larger-scale forcing of the MJO in Indonesia. Significance Statement Rainfall in Jakarta and its surroundings is highly variable and often heavy resulting in devastating floods. In this region, in the wet season, rainfall is influenced by large-scale climate variability including the Madden–Julian oscillation (MJO) characterized by eastward propagation of clouds near the equatorial regions on intraseasonal time scales. The MJO has been known to increase the probability of rainfall occurrence and its magnitude, but we show that the impact differs in varying topography. The frequency and intensity of rainfall increase over land areas including mountains even when MJO has not arrived in Indonesia. Meanwhile, once MJO moves through Indonesia, the frequency and magnitude of the rainfall increases over the northern coast and ocean as well as in the west of the radar domain.
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    Subdaily Rain-Rate Properties in Western Java Analyzed Using C-Band Doppler Radar
    Lestari, S ; Protat, A ; Louf, V ; King, A ; Vincent, C ; Mori, S (AMER METEOROLOGICAL SOC, 2022-09)
    Abstract Jakarta, a megacity in Indonesia, experiences recurrent floods associated with heavy rainfall. Characteristics of subdaily rainfall and the local factors influencing rainfall around Jakarta have not been thoroughly investigated, primarily because of data limitations. In this study, we examine the frequency and intensity of hourly and daily rain rate, including spatial characteristics and variations across time scales. We use 6-min C-band Doppler radar and 1-min in situ data during 2009–12 to resolve spatial rain-rate characteristics at higher resolution than previous studies. A reflectivity–rain rate (Z–R) relationship is derived (Z = 102.7R1.75) and applied to estimate hourly rain rate. Our results show that rain rate around Jakarta is spatially inhomogeneous. In the rainy season [December–February (DJF)], rain rate exhibits statistical properties markedly different from other seasons, with much higher frequency of rain, but, on average, less intense rain rate. In all seasons, there is a persistent higher hourly and daily mean rain rate found over mountainous areas, indicating the importance of local orographic effects. In contrast, for hourly rain-rate extremes, peaks are observed mostly over the coastal land and lowland areas. For the diurnal cycle of mean rain rate, a distinct afternoon peak is found developing earlier in DJF and later in the dry season. This study has implications for other analyses of mesoscale rain-rate extremes in areas of complex topography and suggests that coarse-grain products may miss major features of the rain-rate variability identified in our study. Significance Statement For many years, Jakarta and its surrounding regions have been repeatedly inundated by flooding triggered by short-duration heavy rainfall or rainfall accumulated over multiple days. Little is known about the distribution of local rainfall and how it differs between seasons. In this study, we used high-resolution C-band Doppler radar during 2009–12 to understand the characteristics of rainfall over this complex topography. The results demonstrate that the rainfall features vary spatially and seasonally. In the wet season, rainfall is more frequent but, on average, lighter relative to other seasons. In all seasons, the highest hourly and daily mean rain rate persistently occurs over the mountains, indicating the vital role of topography in generating rainfall in the region.
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    Preparing for a post-net-zero world (Comment)
    King, AD ; Peel, J ; Ziehn, T ; Bowen, KJ ; McClelland, HLO ; McMichael, C ; Nicholls, ZRJ ; Sniderman, JMK (NATURE PORTFOLIO, 2022-08-11)
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    The Link Between the Madden-Julian Oscillation and Rainfall Trends in Northwest Australia
    Borowiak, A ; King, A ; Lane, T (AMER GEOPHYSICAL UNION, 2023-04-28)
    Abstract Rainfall during the monsoon in northwest Australia has increased since the 1950s. Previous studies have explored possible causes of the rainfall increase; however, the trend has not been fully explained. Understanding the cause of this trend is important for interpreting climate projections and local water‐sensitive services. We explore the role of the Madden‐Julian Oscillation (MJO) in explaining the rainfall increase. The MJO, since 1974, has had a longer duration in phases associated with enhanced rainfall in northwest Australia (Phases 5 and 6) during the monsoon. We show that the rainfall trend in northwest Australia is identified only during MJO phases associated with enhanced rainfall, with a large change in daily rainfall distribution in these phases. The increasing occurrence of these MJO phases explains most of the rainfall increase, as opposed to an increase in daily rainfall independent of MJO phase, albeit with some sensitivity to MJO definition.
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    "Winga Is Trying to Get in": Local Observations of Climate Change in the Tiwi Islands
    Barnett, J ; Konlechner, T ; Waters, E ; Minnapinni, MW ; Jarillo, S ; Austral, B ; De Santis, J ; Head, L ; Rioli, C ; King, A (AMER GEOPHYSICAL UNION, 2023-03)
    Abstract There is a growing body of research documenting Indigenous Peoples and Local Communities' observations of changes in climate. The accuracy, efficacy, and transferability of this research depends on its motives and methods. In this paper, we report on research to produce a working knowledge of changes in climate and its impacts on local biophysical systems in the Tiwi Islands in Northern Australia. Interviews with 52 Tiwi people were combined with diverse forms of aerial data to produce a nuanced understanding of climate change in these remote islands. These data show changes in climate‐sensitive biophysical systems that would otherwise remain undetected by instruments conventionally used for monitoring climate change. These include changes in shorelines, which are causing concerns about damage to buildings that are important for Tiwi well‐being, and changes in the marine environment and wetlands, which are causing concerns about damage to natural heritage. We discuss the implications of these findings, arguing that systematic observations collected by networks of people “on Country” can provide excellent monitoring of climate change impacts, and that Indigenous people's interests in the effects of climate change overlap with those of non‐Indigenous people, as do their rights to support from the State for adaptation.
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    Characteristics of extreme rainfall in different gridded datasets over India during 1983-2015
    Bhattacharyya, S ; Sreekesh, S ; King, A (ELSEVIER SCIENCE INC, 2022-04-01)
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    Studying climate stabilization at Paris Agreement levels
    King, AD ; Sniderman, JMK ; Dittus, AJ ; Brown, JR ; Hawkins, E ; Ziehn, T (NATURE PORTFOLIO, 2021-12)