School of Geography, Earth and Atmospheric Sciences - Research Publications
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ItemSimulating Wintertime Orographic Cloud Seeding over the Snowy Mountains of Australia(American Meteorological Society, 2023-09-06)This study presents the first numerical simulations of seeded clouds over the Snowy Mountains of Australia. WRF-WxMod®, a novel glaciogenic cloud seeding model, was utilized to simulate the cloud response to winter orographic seeding under various meteorological conditions. Three cases during the 2018 seeding periods were selected for model evaluation, coinciding with an intensive ground-based measurement campaign. The campaign data were used for model validation and evaluation. Comparisons between simulations and observations demonstrate that the model realistically represents cloud structures, liquid water path, and precipitation. Sensitivity tests were performed to pinpoint key uncertainties in simulating natural and seeded clouds and precipitation processes. They also shed light on the complex interplay between various physical parameters/processes and their interaction with large-scale meteorology. Our study found that in unseeded scenarios, the warm and cold biases in different initialization datasets can heavily influence the intensity and phase of natural precipitation. Secondary ice production via Hallett-Mossop processes exerts a secondary influence. On the other hand, the seeding impacts are primarily sensitive to aerosol conditions and the natural ice nucleation process. Both factors alter the supercooled liquid water availability and the precipitation phase, consequently impacting the AgI nucleation rate. Furthermore, model sensitivities were inconsistent across cases, indicating no single model configuration optimally represents all three cases. This highlights the necessity of employing an ensemble approach for a more comprehensive and accurate assessment of the seeding impact.
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ItemAn evaluation of IMERG and ERA5 quantitative precipitation estimates over the Southern Ocean using shipborne observations(American Meteorological Society, 2023-09-19)Recent voyages of the Australian RV Investigator across the remote Southern Ocean have provided unprecedented observations of precipitation made with both an OceanRAIN maritime disdrometer and a dual-polarization C-band weather radar (OceanPOL). This present study employs these observations to evaluate the Global Precipitation Mission (GPM) Integrated MultisatellitE Retrievals (IMERG) and the ECMWF reanalysis (ERA5) precipitation products. Working at a resolution of 60 minutes and 0.25° (~25 km), light rain and drizzle are most frequently observed across the region. The IMERG product overestimated precipitation intensity when evaluated against the OceanRAIN but captured the frequency of occurrence well. Looking at the synoptic/process scale, IMERG was found to be the least accurate (overestimated intensity) under warm frontal and high latitude cyclone conditions, where multi-layer clouds were commonly present. Under post-frontal conditions, IMERG underestimates the precipitation frequency. In comparison, ERA5’s skill was more consistent across various synoptic conditions, except for high-pressure conditions where the precipitation frequency (intensity) was highly overestimated (underestimated). Using the OceanPOL radar, an area-to-area analysis (fractional skill score) finds that ERA5 has greater skill than the IMERG. There is little agreement in the phase classification between the OceanRAIN disdrometer, IMERG, and ERA5. The comparisons are complicated by the various assumptions for phase classification in the different datasets.
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ItemRegional ochre procurement in the prehistoric American Bottom(Elsevier BV, 2023-10)Ochre has been used for a variety of cultural items worldwide including its use as pigments, polishing tools, medicines, and formal lithic tools such as axes and plummets. Though ochre use in prehistoric North America was commonplace, geochemical analyses of archaeological assemblages typically have focused upon ceramics and stone tools, with ochre treated as a secondary artifact. In the American Bottom, recent limited studies have investigated ochre usage in Late Archaic (3000 – 1000 BCE) and Middle Woodland (150 BCE – 400CE) contexts with inconclusive results. However, the authors suggested that archaeological ochres found in East Central Missouri may have originated within the Meramec River Valley. In this current study, data from previous archaeological and source ochre analyses are combined with similarly dated artifacts from the Verkamp Rockshelter in the Meramec River Valley and additional archaeological samples from five sites in the region. To establish a regional assessment, neutron activation analysis (NAA) and multivariate statistical analysis was utilized to examine geochemical relationships across the region. Results identified distinct compositional differences between archaeological samples from the St. Louis region versus samples collected at Verkamp Rockshelter. Beyond this, no other correlations could be found between chemistry and collection locale. When compared to the available geological source samples from the area, the archaeological samples from the St. Louis region remain distinct, while Meramec River Valley deposits are somewhat compositionally similar to artifacts from Verkamp Rockshelter. This suggests differential acquisition between the two areas.
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ItemIncome polarisation, expenditure and the Australian urban middle class(SAGE Publications, 2023-04-17)Recent years have seen growing concern about the ‘hollowing out’ of the middle class, due to processes of polarisation. In this paper, we examine different conceptualisations of polarisation, and introduce the concept of expenditure-adjusted polarisation that considers not only income, but also various key categories of expenditure at a household level: housing, groceries and meals, transport and energy. Analysing longitudinal data from the Household, Income and Labour Dynamics in Australia Survey, we show that the Australian society is significantly more polarised, with fewer middle-income households, when the relative size of income groups in a given year is based on expenditure-adjusted income rather than pre-expenditure income. Such polarisation is particularly prominent when housing expenditure is considered and has distinctive spatial patterns. In contrast, our analysis finds no evidence of a temporal pattern of polarisation in Australia between 2005 and 2019, with no substantial change in the size of income groups over time, regardless of which income measures are used. We argue that a more nuanced conceptualisation of polarisation, and its relation to processes of ‘hollowing out’ and rising inequality, is needed to inform urban scholarship and policy.
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ItemNo Preview AvailableA case study of a West Sumatra squall line using satellite observations(American Meteorological Society, 2023-02-01)A West Sumatra squall line occurred on 10 January 2016, with a clear offshore propagation of convection. Satellite-derived products from Himawari-8 Advanced Himawari Imager and the Geostationary Cloud Algorithm Testbed Geocat are used to investigate the westward propagation of cloudiness from Sumatra to the Indian Ocean with a lifetime of 1.5 days. A convective mask based on deep convective cell detection and a cell-tracking algorithm are used to estimate the propagation speed of the cloud system. Two distinct mesoscale convective responses are identified: 1) a rapid development in South Sumatra is influenced by the convective environment over the Indian Ocean. The propagation speed is estimated to be ∼5 m s−1 within the first 200 km from the coast. This speed is consistent with density currents. In contrast, 2) the coupling to the inertia–gravity wave is only evident for the northwest of Sumatra with speeds of ∼12 m s−1. The analysis of brightness temperature from the 10.4-μm spectral band and cloud-top temperature showed that the lifetime of the squall line is approximately 30 h with a propagating distance of ∼1000 km. Retrieved cloud properties and tracking of the offshore propagation indicated that the cloud structure consisted of multiple types of cells, propagating as envelopes of convection, and revealed the influence of large-scale variability of the Indian Ocean. Filtered OLR anomalies, satellite-derived rainfall, moisture flux convergence, and background winds flow around Sumatra are used to explore the effects of Kelvin wave activity that likely influenced the lifetime of the squall line.
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ItemBritish–Irish Ice Sheet and polar front history of the Goban Spur, offshore southwest Ireland over the last 250 000 years(Wiley, 2023-01-01)Deep Sea Drilling Program (DSDP) Site 548 was cored in 1984 at a water depth of 1256 m on the Goban Spur, offshore southwest Ireland. Coring retrieved a ~100‐m‐thick Pleistocene contourite sequence. This study uses planktonic foraminiferal assemblage and benthic foraminiferal oxygen isotope analyses to establish an age model for the upper 40 m of this core. This site's multidisciplinary analyses of planktonic foraminiferal assemblages, lithic grains, facies and calcium carbonate concentration reveal a 250 000‐year record of the North Atlantic polar front variability and British–Irish Ice Sheet (BIIS) history. The sequence is characterized by alternations of ice rafted debris (IRD) laden pelagic mud facies with calcium carbonate‐rich silty sand contourite facies that track glacial/interglacial cycles. The polar front migrated southward across the area several times during glacial maxima and stadial periods, while warmer Mediterranean Outflow Water (MOW) flowed northward across the region during interglacial and interstadial periods depositing contourites. Lithic analyses reveal a complex history of IRD deposition associated with iceberg calving from the Laurentide Ice Sheet and northwest European ice sheets, mainly the BIIS. Comparison between the Goban Spur (DSDP Site 548) and the Celtic Margin (MD03‐2692) and central North Atlantic Integrated Ocean Drilling Program (IODP) Site U1308 suggests differences between the ‘non‐Laurentide Ice Sheet’ Heinrich Events (HE) 6 and 3 at the Goban Spur, with IRD from the BIIS being prominent during HE 6 and IRD from other European ice sheets north of the BIIS likely being more dominant during HE 3. The nature of lithics in IRD‐rich horizons during Terminations 3, 3A, 2 and 1 suggests significant iceberg calving episodes preceding BIIS retreat during the onset of interstadial intervals.
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ItemNo Preview AvailableMultiscale Influences on Rainfall in Northeast Australia(American Meteorological Society, 2023-09-01)This study examines the multiscale modulation of mean and extreme rainfall in Northeast (NE) Australia under different background modes of variability, which is a new aspect given the high-resolution and long-term observational datasets. Daily rainfall probability is significantly modified by the Madden–Julian oscillation (MJO), and its influence varies with the seasons and is associated with atmospheric circulation anomalies. Rainfall generally decreases during El Niño and increases during La Niña years; however, there is a notable spatial nuance to El Niño–Southern Oscillation (ENSO)-associated extreme rainfall, with some locations showing the opposite precipitation response to the typical ENSO–rainfall relationship. Despite more precipitation overall in La Niña years, the mean and extreme precipitation responses to the MJO appear to be stronger and more often statistically significant during El Niño compared to La Niña periods. The impact of ENSO on the MJO–rainfall relationship is stronger than the variation of the MJO itself with ENSO, and likely reflects a change in the MJO modulation of rain-bearing atmospheric processes. During El Niño periods, diurnal rainfall amplitude is generally stronger in the central and southern subtropical parts of the study area than during La Niña periods, while the opposite tendency occurs in the northern tropical part. The diurnal cycle of both mean and extreme precipitation is amplified during suppressed convection phases compared to enhanced convection phases of the MJO. In general, the peak time of diurnal cycle does not change with MJO regimes, but there are some notable differences in rainfall propagation between enhanced and suppressed MJO phases.
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ItemEmancipatory political ecology pedagogy in and out of the classroom(Indian Society for Ecological Economics, 2023)In this brief commentary, we reflect on two aspects of contemporary political ecology scholarship: The first is a reflexive assessment of socio-political relational positionalities as a necessary condition, not only to challenge but also to act upon socio-ecological injustices. Second, we examine the effective delivery of cross-cultural pedagogies of care that inform the development of self-reliant political ecology (PE) scholars and/or activists within the constraints of neoliberal education. We argue that both issues are relevant to position PE as an emancipatory pedagogy and praxis in a decolonizing world.
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ItemWho accesses solar PV? Energy Justice and Climate Justice in a local government rooftop solar program(Indian Society for Ecological Economics, 2023)Certain groups within society, such as the poor, the elderly, and those renting their homes, are at risk of bearing disproportionate costs from the transition to a low-carbon economy. These groups are particularly at risk of energy- and climate-related injustices linked to their ability to purchase sufficient energy (low-carbon or otherwise) or to adequately heat or cool their homes. The Solar Saver programme in Melbourne, Australia, was an early attempt by Darebin City Council, a local government, to address these issues. The programme enables seniors, low-income residents, and tenants in the City of Darebin to install solar PV in their homes at no upfront cost. The system costs are repaid interest-free over 10 years through residents’ council rates. This article assesses the success of the programme in reaching its target audience and achieving justice for participants in 2018 and 2019. We find that local councils are important and trusted delivery agents of household energy programmes. We also find that schemes like Solar Saver must be actively targeted to achieve energy- and climate-justice outcomes for residents who are at risk of energy poverty and disproportionate climate impacts.
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ItemSocial Memory in the Mekong's Changing Floodscapes: Narratives of Agrarian Communities' Adaptation(SPRINGER/PLENUM PUBLISHERS, 2022-10-04)Rural adaptation encompasses place-based perceptions, behaviors, livelihoods, and traditional ways of life associated with local environments. These perceptions, norms, and practices are disturbed by coupled environment-development externalities. This study employs the Vietnamese Mekong floodplains as an exemplary case to illustrate how floods impact agrarian communities and how they have experienced flood alterations driven by hydropower development and climate change in recent years. Drawing on thematic and narrative analyses of qualitative data (focus group discussions and interviews) collected in three agrarian communities in the Vietnamese Mekong floodplains, sources drawn from various news outlets, and academic materials, we argue that disrupted flood environments in the floodplains have triggered affective flood reminiscences, catalysing shifts to incremental and transformative adaptation to achieve resilience. We build a nuanced understanding of how social memory helps to enhance human-environment relationships in response to highly complex hydrological dynamics in the delta.