School of Earth Sciences - Research Publications
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ItemSub-synoptic scale features associated with extreme surface gusts during the South Australia Storm of September 2016-Part I: characteristics of the event(WILEY, 2019-08)Abstract Winds are one of the major meteorological contributors to deaths, damage and insured losses in Australia. A ‘freak storm’ hit the state of South Australia on 28 September 2016, causing state‐wide blackouts and leaving 1.7 million people without power. In the first part of this two‐part study, we analyse this event and find that it was indeed extreme, deepening more explosively than all but two Adelaide‐affecting extratropical cyclones over the past 37 years and exhibiting the lowest central pressure. This generated hurricane force winds, with the central South Australia site of Neptune Island recording a gust of over 120kmh−1. We show that this storm potentially contained a sting jet. Such jets are well known as a cause of major damage across Europe, and this is the first study which investigates whether a sting jet can be produced over Australia. The main deepening of the system occurred over the Great Australian Bight, so if a sting jet did form and make it to the surface, it was not the cause of the state‐wide damage. However, the cyclone did contain numerous extreme gust‐producing mesoscale features, as explored in part II of this paper (Earl and Simmons, 2018).
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ItemSub synoptic scale features of the South Australia Storm of September 2016-Part II: analysis of mechanisms driving the gusts(WILEY, 2019-09)Abstract An extreme extratropical cyclone (ETC) struck South Australia on 28 September 2016, causing state‐wide blackouts and damage. In the second part of this two‐part study, we examine the extreme surface wind producing mechanisms within the ETC. ETCs have been extensively studied in the Northern Hemisphere (particularly in western Europe), highlighting the gust‐producing mesoscale features within. Before now, no Southern Hemisphere ETC has been examined in this way. There were a number of extreme gust‐producing features within the ETC, comparable to those observed in storms over western Europe. One such feature was a convective line, which caused many of the most extreme gusts and knocked out the state power grid. However, dry slot convection also contributed to the extremes, and this feature rarely causes extreme gusts in ETCs over the UK. Thus, further analysis is warranted to examine whether this is a common extreme‐gust‐producing ETC feature over Southern Australia. The strongest winds recorded throughout the event occurred on 29 September, and these were associated with the cold conveyor belt which spiralled around the low‐pressure centre.
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ItemSpatial and Temporal Variability and Trends in 2001-2016 Global Fire Activity(AMER GEOPHYSICAL UNION, 2018-03-16)Abstract Fire regimes across the globe have great spatial and temporal variability, and these are influence by many factors including anthropogenic management, climate, and vegetation types. Here we utilize the satellite‐based “active fire” product, from Moderate Resolution Imaging Spectroradiometer (MODIS) sensors, to statistically analyze variability and trends in fire activity from the global to regional scales. We split up the regions by economic development, region/geographical land use, clusters of fire‐abundant areas, or by religious/cultural influence. Weekly cycle tests are conducted to highlight and quantify part of the anthropogenic influence on fire regime across the world. We find that there is a strong statistically significant decline in 2001–2016 active fires globally linked to an increase in net primary productivity observed in northern Africa, along with global agricultural expansion and intensification, which generally reduces fire activity. There are high levels of variability, however. The large‐scale regions exhibit either little change or decreasing in fire activity except for strong increasing trends in India and China, where rapid population increase is occurring, leading to agricultural intensification and increased crop residue burning. Variability in Canada has been linked to a warming global climate leading to a longer growing season and higher fuel loads. Areas with a strong weekly cycle give a good indication of where fire management is being applied most extensively, for example, the United States, where few areas retain a natural fire regime.
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ItemWeekly cycles of global fires-Associations with religion, wealth and culture, and insights into anthropogenic influences on global climate(AMER GEOPHYSICAL UNION, 2015-11-16)Abstract One approach to quantifying anthropogenic influences on the environment and the consequences of those is to examine weekly cycles (WCs). No long‐term natural process occurs on a WC so any such signal can be considered anthropogenic. There is much ongoing scientific debate as to whether regional‐scale WCs exist above the statistical noise level, with most significant studies claiming that anthropogenic aerosols and their interaction with solar radiation and clouds (direct/indirect effect) is the controlling factor. A major source of anthropogenic aerosol, underrepresented in the literature, is active fire (AF) from anthropogenic burning for land clearance/management. WCs in AF have not been analyzed heretofore, and these can provide a mechanism for observed regional‐scale WCs in several meteorological variables. We show that WCs in AFs are highly pronounced for many parts of the world, strongly influenced by the working week and particularly the day(s) of rest, associated with religious practices.