Multidecadal fluctuations of winter rainfall over southwest Western Australia simulated in the CSIRO Mark 3 coupled model

Cai, Wenju; Shi, Ge; Li, Yun

doi:10.1029/2005gl022712

Cited by 45 publications

(35 citation statements)

References 16 publications

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“…The rainfall decrease in SWWA has been studied intensely in recent years (e.g. Smith et al, 2000;Cai and Watterson, 2002;IOCI, 2002;Pitman et al, 2004;Cai et al, 2005;Cai and Cowan, 2006;Hope et al, 2006;Meneghini et al, 2007;Feng et al, 2010aFeng et al, , 2010b, as has the increasing trend in NWA (Wardle and Smith, 2004;Rotstayn et al, 2006;Shi et al, 2008aShi et al, , 2008bTaschetto and England, 2008). In contrast, relatively little is known of the cause and mechanism of the decreased NEA rainfall.…”

Section: Introductionmentioning

confidence: 99%

A possible cause of decreasing summer rainfall in northeast Australia

Li¹,

Feng²,

Li³

2011

Intl Journal of Climatology

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ABSTRACT:The NCEP/NCAR reanalysis and precipitation data from the Australian Bureau of Meteorology are used to analyse variability in rainfall during the austral summer (December-March, DJFM) in northeast Australia (NEA). NEA rainfall shows a marked decrease over the past 50 years, mainly in the austral summer. Our analysis reveals that the summer rainfall decrease in NEA is generally an interdecadal phenomenon. The declining trend has an imprint in the tropical Australian summer monsoon (TASM). Not only does TASM have a phase-to-phase influence on NEA summer rainfall at the interannual scale, it is also closely linked with interdecadal variation in NEA summer rainfall. Thus, the decrease in NEA at the interdecadal scale could be attributed to corresponding variation in TASM. Moreover, the coupled linkage between TASM and NEA summer rainfall appears to be largely independent of El Niño-Southern Oscillation. One possible reason for the interdecadal weakening trend in TASM is a sustained interdecadal warming trend in sea surface temperature (SST) over the Wharton Basin (100°-130°E, 20°-5°S). When the Wharton Basin is in a cold state, anomalous westerlies occur in the lower troposphere in the TASM region, and cyclonic circulation anomalies and rising flows occur in the low and middle troposphere over NEA, which are associated with a strong TASM situation, consequently favouring enhanced rainfall over NEA; the opposite occurs in the case of a warm Wharton Basin. SST over the Wharton Basin has shown a continuous warming trend over the past 60 years, contributing to the weakening of TASM and, consequently, a decrease in NEA summer rainfall.

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Section: Introductionmentioning

confidence: 99%

A possible cause of decreasing summer rainfall in northeast Australia

Li¹,

Feng²,

Li³

2011

Intl Journal of Climatology

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“…They suggest that the SAM affects snowlines via weakened (strengthened) zonal flow carrying a reduced (increased) number of depressions over the New Zealand region during its low (high) phases. SAM influences on rainfall in other midlatitude regions have been shown previously: for example, for southwest Western Australia by shifting the position of the maximum temperature gradient and modulating baroclinic instability (Cai et al 2005); across the Australian continent (Meneghini et al 2006); for South America via changes to the upper-level atmospheric circulation and moisture convergence (Silvestri and Vera 2003); and for South Africa via shifts in the position of the subtropical jet and associated moisture flux (Reason and Roualt 2005). This is the first study to investigate the impact of the SAM on New Zealand's interannual precipitation.…”

Section: Introductionmentioning

confidence: 99%

Interannual Extremes in New Zealand Precipitation Linked to Modes of Southern Hemisphere Climate Variability

2007

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Interannual extremes in New Zealand rainfall and their modulation by modes of Southern Hemisphere climate variability are examined in observations and a coupled climate model. North Island extreme dry (wet) years are characterized by locally increased (reduced) sea level pressure (SLP), cold (warm) sea surface temperature (SST) anomalies in the southern Tasman Sea and to the north of the island, and coinciding reduced (enhanced) evaporation upstream of the mean southwesterly airflow. During extreme dry (wet) years in South Island precipitation, an enhanced (reduced) meridional SLP gradient occurs, with circumpolar strengthened (weakened) subpolar westerlies and an easterly (westerly) anomaly in zonal wind in the subtropics. As a result, via Ekman transport, anomalously cold (warm) SST appears under the subpolar westerlies, while anomalies of the opposite sign occur farther north. The phase and magnitude of the resulting SST and evaporation anomalies cannot account for the rainfall extremes over the South Island, suggesting a purely atmospheric mode of variability as the driving factor, in this case the Southern Annular Mode (SAM). New Zealand rainfall variability is predominantly modulated by two Southern Hemisphere climate modes, namely, the El Niño-Southern Oscillation (ENSO) and the SAM, with a latitudinal gradation in influence of the respective phenomena, and a notable interaction with orographic features. While this heterogeneity is apparent both latitudinally and as a result of orographic effects, climate modes can force local rainfall anomalies with considerable variations across both islands. North Island precipitation is for the most part regulated by both local air-sea heat fluxes and circulation changes associated with the tropical ENSO mode. In contrast, for the South Island the influence of the large-scale general atmospheric circulation dominates, especially via the strength and position of the subpolar westerlies, which are modulated by the extratropical SAM.

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“…These changes have further led to intensification of the tropospheric circumpolar circulation (Thompson and Solomon, 2002;Gillett and Thompson, 2003). Among other impacts, the intensification of the tropospheric circulation has contributed to significant decrease of rainfalls in southwest Australia (Cai et al, 2005) and to dramatic warming of the Antarctic Peninsula (Marshall et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Quantitative assessment of Southern Hemisphere ozone in chemistry-climate model simulations

et al. 2010

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Abstract. Stratospheric ozone recovery in the SouthernHemisphere is expected to drive pronounced trends in atmospheric temperature and circulation from the stratosphere to the troposphere in the 21st century; therefore ozone changes need to be accounted for in future climate simulations. Many climate models do not have interactive ozone chemistry and rely on prescribed ozone fields, which may be obtained from coupled chemistry-climate model (CCM) simulations. However CCMs vary widely in their predictions of ozone evolution, complicating the selection of ozone boundary conditions for future climate simulations. In order to assess which models might be expected to better simulate future ozone evolution, and thus provide more realistic ozone boundary conditions, we assess the ability of twelve CCMs to simulate observed ozone climatology and trends and rank the models according to their errors averaged across the individual diagnostics chosen. According to our analysis no one model performs better than the others in all the diagnostics; however, combining errors in individual diagnostics into one metric of model performance allows us to objectively rank the models. The multi-model average shows better overall agreement with the observations than any individual model. Based on this analysis we conclude that the multi-model average ozone projection presents the best estimate of future ozone evolution and recommend it for use as a boundary condition in future climate simulations. Our results also demonstrate a sensitivity of the analysis to the choice of reference data set Correspondence to: A. Yu. Karpechko (alexey.karpechko@fmi.fi) for vertical ozone distribution over the Antarctic, highlighting the constraints that large observational uncertainty imposes on such model verification.

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Multidecadal fluctuations of winter rainfall over southwest Western Australia simulated in the CSIRO Mark 3 coupled model

Cited by 45 publications

References 16 publications

A possible cause of decreasing summer rainfall in northeast Australia

A possible cause of decreasing summer rainfall in northeast Australia

Interannual Extremes in New Zealand Precipitation Linked to Modes of Southern Hemisphere Climate Variability

Quantitative assessment of Southern Hemisphere ozone in chemistry-climate model simulations

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