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Intra-seasonal drivers of extreme heat over Australia in observations and POAMA-2
Citation
Marshall, AG and Hudson, D and Wheeler, MC and Alves, O and Hendon, HH and Pook, MJ and Risbey, JS, Intra-seasonal drivers of extreme heat over Australia in observations and POAMA-2, Climate Dynamics, 43, (7-8) pp. 1915-1937. ISSN 0930-7575 (2013) [Refereed Article]
Copyright Statement
Copyright 2013 Springer-Verlag Berlin Heidelberg
DOI: doi:10.1007/s00382-013-2016-1
Abstract
We assess the occurrence and probability of extreme heat over Australia in association with the Southern Annular Mode (SAM), persistent anticyclones over the Tasman Sea, and the Madden–Julian Oscillation (MJO), which have previously been shown to be key drivers of intra-seasonal variations of Australian climate. In this study, extreme heat events are defined as occurring when weekly-mean maximum temperature anomalies exceed the 90th percentile. The observed probability of exceedance is reduced during the positive phase of the SAM and enhanced during the negative phase of the SAM over most of Australia. Persistent anticyclones over the Tasman Sea are described in terms of (1) split-flow blocking at 160°E and (2) high pressure systems located in the vicinity of the subtropical ridge (STRHs), about 10° north of the split-flow blocking region, for which we devise a simple index. Split-flow blocks and STRHs have contrasting impacts on the occurrence of extreme heat over Australia, with STRHs showing enhanced probability of upper decile heat events over southern Australia in all seasons. The observed probability of an upper decile heat event varies according to MJO phase and time of year, with the greatest impact of the MJO on extreme heat occurring over southern Australia (including the Mallee agricultural region) in spring during phases 2–3. We show that this modulation of the probability of extreme heat by the SAM, persistent anticyclones over the Tasman Sea, and the MJO is well simulated in the Bureau of Meteorology dynamical intra-seasonal/seasonal forecast model POAMA-2 at lead times of 2–3 weeks. We further show that predictability of heat extremes increases in association with the negative SAM phase, STRH and MJO, thus providing a basis for skilful intra-seasonal prediction of heat extremes.
Item Details
| Item Type: | Refereed Article |
|---|---|
| Keywords: | extreme heat, POAMA-2, SAM, MJO |
| Research Division: | Earth Sciences |
| Research Group: | Atmospheric Sciences |
| Research Field: | Meteorology |
| Objective Division: | Environment |
| Objective Group: | Atmosphere and Weather |
| Objective Field: | Atmospheric Processes and Dynamics |
| Author: | Pook, MJ (Dr Michael Pook) |
| Author: | Risbey, JS (Dr James Risbey) |
| ID Code: | 119538 |
| Year Published: | 2013 |
| Web of Science® Times Cited: | 26 |
| Deposited By: | Oceans and Cryosphere |
| Deposited On: | 2017-08-02 |
| Last Modified: | 2017-09-19 |
| Downloads: | 0 |
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