School of Earth Sciences - Research Publications
Permanent URI for this collection
Search Results
1 - 10 of 16
-
Item
-
Item
-
Item
-
Item
-
Item
-
ItemOn the use of composite analyses to form physical hypotheses: An example from heat wave - SST associations(NATURE PORTFOLIO, 2016-07-14)This paper highlights some caveats in using composite analyses to form physical hypotheses on the associations between environmental variables. This is illustrated using a specific example, namely the apparent links between heat waves (HWs) and sea surface temperatures (SSTs). In this case study, a composite analysis is performed to show the large-scale and regional SST conditions observed during summer HWs in Perth, southwest Australia. Composite results initially point to the importance of the subtropical South Indian Ocean, where physically coherent SST dipole anomalies appear to form a necessary condition for HWs to develop across southwest Australia. However, sensitivity tests based on pattern correlation analyses indicate that the vast majority of days when the identified SST pattern appears are overwhelmingly not associated with observed HWs, which suggests that this is definitely not a sufficient condition for HW development. Very similar findings are obtained from the analyses of 15 coupled climate model simulations. The results presented here have pertinent implications and applications for other climate case studies, and highlight the importance of applying comprehensive statistical approaches before making physical inferences on apparent climate associations.
-
ItemErratum: On the use of composite analyses to form physical hypotheses: An example from heat wave - SST associations.(Springer Science and Business Media LLC, 2016-08-24)Scientific Reports 6: Article number: 29599; published online: 14 July 2016; updated: 24 August 2016 This Article contains an error in the legend of Table 1. “Results are computed for the entire 3150 days in DJF (black values) and for the 25 HW days selected in DJF (bold italic) during 1979–2014,” should read:
-
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.
-
ItemVariability and Trends of Global Atmospheric Frontal Activity and Links with Large-Scale Modes of Variability(AMER METEOROLOGICAL SOC, 2015-04)Abstract Presented here is a global analysis of frontal activity variability derived from ERA-Interim data over the 34-yr period of January 1979–March 2013 using a state-of-the-art frontal tracking scheme. In December–February over that epoch, there is a northward shift of frontal activity in the Pacific in the Northern Hemisphere (NH). In the Southern Hemisphere (SH), the largest trends are identified in the austral summer and are manifested by a southward shift of frontal activity over the Southern Ocean. Variability of frontal behavior is found to be closely related to the main modes of atmospheric circulation, such as the North Atlantic Oscillation (NAO) for the Atlantic–European sector in the NH and the southern annular mode (SAM) in the middle and high latitudes of the SH. A signal associated with El Niño and hence emanating from the tropics is also apparent in the behavior of frontal systems over the Pacific by a reduction in the number of fronts in the middle South Pacific and intensification of frontal activity in high and low latitudes throughout the year. It is shown in general that the associations of the large-scale modes with frontal variability are much stronger than with cyclones. This indicates that the quantification of the behavior of fronts is an important component of understanding the climate system. At the very high latitudes, it is also shown here that, in the recent years of rapid sea ice reduction in the Arctic, there have been fewer summer fronts observed over the Canadian Arctic.
-
ItemSea level pressure response to the specification of eddy-resolving sea surface temperature in simulations of Australian east coast lows(Whioce Publishing Pte Ltd, 2016-02-13)Four east coast lows (ECLs) were simulated with the Weather Research and Forecast model to investigate the influence of the sea surface temperature (SST) distribution on the sea level pressure (SLP). Each ECL was simulated with two different SST datasets: the Bluelink SST field and NCEP skin temperature field. The former resolved eddies in the East Australian Current while the latter did not. The simulated SLP fields in the eddy-resolving SST runs were compared with those in the non-eddy-resolving SST runs. On time-scales of about 48 hours, higher SSTs were asso-ciated with lower SLPs. The spatial scale of the SLP response was similar to that of the ocean eddies, indicative of the rapidity and robustness of the response given the rapidly evolving conditions within the storms. On shorter time-scales, the SLP response to SST change can become substantially larger. The largest reductions in SLP in the eddy-resolving SST runs were associated with regions of deep atmospheric convection that warm the tropospheric column. These areas were shown to be related to the SST distribution with the greatest SLP reductions associated with convection over strong SST gradient regions. The landfall of a damaging convective mesoscale low pressure system on 8 June 2007 was also investigated. It was found that a region of strong SST gradients on the southern flank of a large warm ocean eddy was associated with lower pressures at the time of formation of this meso-low. In addition, the only case that simulated the low pressure at the correct time (albeit at not quite the correct location) was the eddy-resolved SST run. It was hy-pothesized that the development of this meso-low that impacted the coast around Newcastle, was enhanced because of the eddy-scale SST distribution at the time.