Using Large-scale Diagnostic Quantities to Investigate Change in East Coast Lows.

Ji, F., J.P. Evans, D. Argueso, L. Fita and A. Di Luca
Climate Dynamics, doi: 10.1007/s00382-015-2481-9, 2015.


East Coast Lows (ECLs) are intense low-pressure systems that affect the eastern seaboard of Australia. They have attracted research interest for both their destructive nature and water supplying capability. Estimating the changes in ECLs in the future has a major impact on emergency response as well as water management strategies for the coastal communities on the east coast of Australia. In this study, ECLs were identified using two large-scale diagnostic quantities: isentropic potential vorticity (IPV) and geostrophic vorticity (GV), which were calculated from outputs of historical and future regional climate simulations from the NSW/ACT regional climate modelling (NARCliM) project. The diagnostic results for the historical period were evaluated against a subjective ECL event database. Future simulations using a high emission scenario were examined to estimate changes in frequency, duration, and intensity of ECLs. The use of a relatively high resolution regional climate model makes this the first study to examine future changes in ECLs while resolving the full range of ECL sizes which can be as small as 100–200 km in diameter. The results indicate that it is likely that there will be fewer ECLs, with weaker intensity in the future. There could also be a seasonal shift in ECLs from cool months to warm months. These changes have the potential to significantly impact the water security on the east coast of Australia.

Key Figure

Figure 7. Plots summarizing changes in monthly IPV/GV indicated ECLs for 12 simulations. The boxes and whiskers shows the results from 12 simulations. The boxes shows the inter-quartile range, the middle horizontal lines shows the median and the whiskers shows the highest and the lowest values. The results from two diagnostic quantities and two future periods are shown in different colors. Red columns represent changes in IPV indicated ECLs, green columns represent changes in GV indicated ECLs. Light and dark colour columns shows the changes for 2020–2039 and 2060–2079 relative to 1990–2009, respectively

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