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  • Online Resource  (24)
  • 2010-2014  (24)
  • Physics  (24)
  • 1
    Online Resource
    Online Resource
    The Association of Tropical and Extratropical Climate Modes to Atmospheric Blocking across Southeastern Australia
    American Meteorological Society ; 2013
    In:  Journal of Climate Vol. 26, No. 19 ( 2013-10-01), p. 7555-7569
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 26, No. 19 ( 2013-10-01), p. 7555-7569
    Abstract: Relationships of the Indian Ocean dipole (IOD), El Niño–Southern Oscillation (ENSO), and the southern annular mode (SAM) with atmospheric blocking are investigated using a linear framework over the austral autumn–spring (cool) seasons for southeast Australia (SEA). Positive blocking events occurring at 130°–140°E increase the likelihood of cutoff low pressure systems developing that generate significant rainfall totals across SEA. In mid to late austral autumn (April–May), blocking is coherent with negative IOD events. During this season, a negative IOD event and blocking are associated with warm sea surface temperature anomalies in the eastern tropical Indian Ocean and a blocking high pressure cell south of Australia. An anomalous cyclonic pressure center over southern Australia directs tropical moisture flux anomalies to the region. Despite this, only a small portion of a negative IOD's impact on SEA rainfall comes through blocking events. During austral winter, ENSO is coherent with blocking; anomalous tropical moisture fluxes from the western Pacific during a La Niña merge with anomalous cyclonic flows centered over SEA, delivering enhanced rainfall via cutoff lows. The low pressure cell constitutes a center of the Southern Oscillation associated with ENSO. This ENSO-blocking coherence is considerably weaker in austral spring, whereby circulation anomalies associated with blocking resemble a SAM-like pattern. As such, a large portion of the SAM's impact on SEA spring rainfall occurs in conjunction with blocking events. The relative importance of associations between the dominant climate modes and blocking in generating the drought-breaking cool season precipitation in 2010 across SEA is discussed.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-12-00781.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2013
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 2
    Online Resource
    Online Resource
    Realism of the Indian Ocean Dipole in CMIP5 Models: The Implications for Climate Projections
    American Meteorological Society ; 2013
    In:  Journal of Climate Vol. 26, No. 17 ( 2013-09-01), p. 6649-6659
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 26, No. 17 ( 2013-09-01), p. 6649-6659
    Abstract: An assessment of how well climate models simulate the Indian Ocean dipole (IOD) is undertaken using 20 coupled models that have partaken in phase 5 of the Coupled Model Intercomparison Project (CMIP5). Compared with models in phase 3 (CMIP3), no substantial improvement is evident in the simulation of the IOD pattern and/or amplitude during austral spring [September–November (SON)] . The majority of models in CMIP5 generate a larger variance of sea surface temperature (SST) in the Sumatra–Java upwelling region and an IOD amplitude that is far greater than is observed. Although the relationship between precipitation and tropical Indian Ocean SSTs is well simulated, future projections of SON rainfall changes over IOD-influenced regions are intrinsically linked to the IOD amplitude and its rainfall teleconnection in the model present-day climate. The diversity of the simulated IOD amplitudes in models in CMIP5 (and CMIP3), which tend to be overly large, results in a wide range of future modeled SON rainfall trends over IOD-influenced regions. The results herein highlight the importance of realistically simulating the present-day IOD properties and suggest that caution should be exercised in interpreting climate projections in the IOD-affected regions.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-12-00807.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2013
    detail.hit.zdb_id: 246750-1
    detail.hit.zdb_id: 2021723-7
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  • 3
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    Online Resource
    Asymmetry in ENSO Teleconnection with Regional Rainfall, Its Multidecadal Variability, and Impact
    American Meteorological Society ; 2010
    In:  Journal of Climate Vol. 23, No. 18 ( 2010-09-15), p. 4944-4955
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 23, No. 18 ( 2010-09-15), p. 4944-4955
    Abstract: An asymmetry, and its multidecadal variability, in a rainfall teleconnection with the El Niño–Southern Oscillation (ENSO) are described. Further, the breakdown of this relationship since 1980 is offered as a cause for a rainfall reduction in an ENSO-affected region, southeast Queensland (SEQ). There, austral summer rainfall has been declining since around the 1980s, but the associated process is not understood. It is demonstrated that the rainfall reduction is not simulated by the majority of current climate models forced with anthropogenic forcing factors. Examination shows that ENSO is a rainfall-generating mechanism for the region because of an asymmetry in its impact: the La Niña–rainfall relationship is statistically significant, as SEQ summer rainfall increases with La Niña amplitude; by contrast, the El Niño–induced rainfall reductions do not have a statistically significant relationship with El Niño amplitude. Since 1980, this asymmetry no longer operates, and La Niña events no longer induce a rainfall increase, leading to the observed SEQ rainfall reduction. A similar asymmetric rainfall teleconnection with ENSO Modoki exists and shares the same temporal evolutions. This breakdown is caused by an eastward shift in the Walker circulation and the convection center near Australia’s east coast, in association with a post-1980 positive phase of the interdecadal Pacific oscillation (IPO). Such a breakdown occurred before 1950, indicating that multidecadal variability alone could potentially be responsible for the recent SEQ rainfall decline. An aggregation of outputs from climate models to distill the impact of climate change suggests that the asymmetry and the breakdown may not be generated by climate change, although most models do not perform well in simulating the ENSO–rainfall teleconnection over the SEQ region.
    Type of Medium: Online Resource
    ISSN: 1520-0442 , 0894-8755
    URL: Article
    DOI: 10.1175/2010JCLI3501.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2010
    detail.hit.zdb_id: 246750-1
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  • 4
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    Online Resource
    Teleconnection Pathways of ENSO and the IOD and the Mechanisms for Impacts on Australian Rainfall
    American Meteorological Society ; 2011
    In:  Journal of Climate Vol. 24, No. 15 ( 2011-08-01), p. 3910-3923
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 24, No. 15 ( 2011-08-01), p. 3910-3923
    Abstract: Impacts of El Niño–Southern Oscillation (ENSO) and the Indian Ocean dipole (IOD) on Australian rainfall are diagnosed from the perspective of tropical and extratropical teleconnections triggered by tropical sea surface temperature (SST) variations. The tropical teleconnection is understood as the equatorially trapped, deep baroclinic response to the diabatic (convective) heating anomalies induced by the tropical SST anomalies. These diabatic heating anomalies also excite equivalent barotropic Rossby wave trains that propagate into the extratropics. The main direct tropical teleconnection during ENSO is the Southern Oscillation (SO), whose impact on Australian rainfall is argued to be mainly confined to near-tropical portions of eastern Australia. Rainfall is suppressed during El Niño because near-tropical eastern Australia directly experiences subsidence and higher surface pressure associated with the western pole of the SO. Impacts on extratropical Australian rainfall during El Niño are argued to stem primarily from the Rossby wave trains forced by convective variations in the Indian Ocean, for which the IOD is a primary source of variability. These equivalent-barotropic Rossby wave trains emanating from the Indian Ocean induce changes to the midlatitude westerlies across southern Australia, thereby affecting rainfall through changes in mean-state baroclinicity, west–east steering, and possibly orographic effects. Although the IOD does not mature until austral spring, its impact on Australian rainfall during winter is also ascribed to this mechanism. Because ENSO is largely unrelated to the IOD during austral winter, there is limited impact of ENSO on rainfall across southern latitudes of Australia in winter. A strong impact of ENSO on southern Australia rainfall in spring is ascribed to the strong covariation of ENSO and the IOD in this season. Implications of this pathway from the tropical Indian Ocean for impacts of both the IOD and ENSO on southern Australian climate are discussed with regard to the ability to make seasonal climate predictions and with regard to the role of trends in tropical SST for driving trends in Australian climate.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/2011JCLI4129.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2011
    detail.hit.zdb_id: 246750-1
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  • 5
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    Nonlinear Feedbacks Associated with the Indian Ocean Dipole and Their Response to Global Warming in the GFDL-ESM2M Coupled Climate Model
    American Meteorological Society ; 2014
    In:  Journal of Climate Vol. 27, No. 11 ( 2014-06-01), p. 3904-3919
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 27, No. 11 ( 2014-06-01), p. 3904-3919
    Abstract: A feature of the Indian Ocean dipole (IOD) is its positive skewness, with cold IOD east pole (IODE) sea surface temperature anomalies (SSTAs) exhibiting larger amplitudes than warm SSTAs. Using the coupled Geophysical Fluid Dynamics Laboratory Earth System Model with Modular Ocean Model version 4 (MOM4) component (GFDL-ESM2M), the role of nonlinear feedbacks in generating this positive skewness is investigated and their response to global warming examined. These feedbacks are a nonlinear dynamic heating process, the Bjerknes feedback, wind–evaporation–SST feedback, and SST–cloud–radiation feedback. Nonlinear dynamic heating assists IOD skewness by strongly damping warm IODE SSTAs and reinforcing cold IODE anomalies. In a warmer climate, the damping strengthens while the reinforcement weakens. The SST–thermocline relationship is part of the positive Bjerknes feedback and contributes strongly to IOD skewness as it is weak during the development of warm IODE SSTAs, but strong during the development of cold IODE SSTAs. In response to global warming, this relationship displays weaker asymmetry associated with weaker westerly winds over the central equatorial Indian Ocean. The negative SST–cloud–radiation feedback is also asymmetric with cold IODE SSTAs less damped by incoming shortwave radiation. Under global warming, the damping of cold IODE SSTAs shows little change but warm IODE SSTAs become more damped. This stronger damping is a symptom of negative IODs becoming stronger in amplitude due to the mean IODE thermocline shoaling. The wind–evaporation–SST feedback does not contribute to IOD asymmetry with cold IODE SSTAs decreasing evaporation, which in turn warms the surface. However, as this study focuses on one model, the response of these feedbacks to global warming is uncertain.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-13-00527.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2014
    detail.hit.zdb_id: 246750-1
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  • 6
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    Did Climate Change–Induced Rainfall Trends Contribute to the Australian Millennium Drought?
    American Meteorological Society ; 2014
    In:  Journal of Climate Vol. 27, No. 9 ( 2014-05-01), p. 3145-3168
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 27, No. 9 ( 2014-05-01), p. 3145-3168
    Abstract: The Australian decade-long “Millennium Drought” broke in the summer of 2010/11 and was considered the most severe drought since instrumental records began in the 1900s. A crucial question is whether climate change played a role in inducing the rainfall deficit. The climate modes in question include the Indian Ocean dipole (IOD), affecting southern Australia in winter and spring; the southern annular mode (SAM) with an opposing influence on southern Australia in winter to that in spring; and El Niño–Southern Oscillation, affecting northern and eastern Australia in most seasons and southeastern Australia in spring through its coherence with the IOD. Furthermore, the poleward edge of the Southern Hemisphere Hadley cell, which indicates the position of the subtropical dry zone, has possible implications for recent rainfall declines in autumn. Using observations and simulations from phase 5 of the Coupled Model Intercomparison Project (CMIP5), it is shown that the drought over southwest Western Australia is partly attributable to a long-term upward SAM trend, which contributed to half of the winter rainfall reduction in this region. For southeast Australia, models simulate weak trends in the pertinent climate modes. In particular, they severely underestimate the observed poleward expansion of the subtropical dry zone and associated impacts. Thus, although climate models generally suggest that Australia’s Millennium Drought was mostly due to multidecadal variability, some late-twentieth-century changes in climate modes that influence regional rainfall are partially attributable to anthropogenic greenhouse warming.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-13-00322.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2014
    detail.hit.zdb_id: 246750-1
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  • 7
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    Online Resource
    Atmospheric and Oceanic Conditions Associated with Southern Australian Heat Waves: A CMIP5 Analysis
    American Meteorological Society ; 2014
    In:  Journal of Climate Vol. 27, No. 20 ( 2014-10-15), p. 7807-7829
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 27, No. 20 ( 2014-10-15), p. 7807-7829
    Abstract: Atmospheric and oceanic conditions associated with southern Australian heat waves are examined using phase 5 of the Coupled Model Intercomparison Project (CMIP5) models. Accompanying work analyzing modeled heat wave statistics for Australia finds substantial increases in the frequency, duration, and temperature of heat waves by the end of the twenty-first century. This study assesses the ability of CMIP5 models to simulate the synoptic and oceanic conditions associated with southern Australian heat waves, and examines how the classical atmospheric setup associated with heat waves is projected to change in response to mean-state warming. To achieve this, near-surface temperature, mean sea level pressure, and sea surface temperature (SST) from the historical and high-emission simulations are analyzed. CMIP5 models are found to represent the synoptic setup associated with heat waves well, despite showing greater variation in simulating SST anomalies. The models project a weakening of the pressure couplet associated with future southern Australian heat waves, suggesting that even a non-classical synoptic setup is able to generate more frequent heat waves in a warmer world. A future poleward shift and strengthening of heat wave–inducing anticyclones is confirmed using a tracking scheme applied to model projections. Model consensus implies that while anticyclones associated with the hottest future southern Australian heat waves will be more intense and originate farther poleward, a greater proportion of heat waves occur in association with a weaker synoptic setup that, when combined with warmer mean-state temperatures, gives rise to more future heat waves.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-14-00098.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2014
    detail.hit.zdb_id: 246750-1
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  • 8
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    A New Type of the Indian Ocean Dipole since the Mid-1970s
    American Meteorological Society ; 2013
    In:  Journal of Climate Vol. 26, No. 3 ( 2013-02-01), p. 959-972
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 26, No. 3 ( 2013-02-01), p. 959-972
    Abstract: The tropical Indian Ocean dipole/zonal mode (IOD) is phase locked with the austral winter and spring seasons. This study describes three types of the IOD in terms of their peak time and duration. In particular, the authors focus on a new type that develops in May–June and matures in July–August, which is distinctively different from the canonical IOD, which may develop later and peak in September–November or persist from June to November. Such “unseasonable” IOD events are only observed since the mid-1970s, a period after which the tropical Indian Ocean has a closer relationship with the Pacific Ocean. The unseasonable IOD is an intrinsic mode of the Indian Ocean and occurs without an ensuing El Niño. A change in winds along the equator is identified as a major forcing. The wind change is in turn related to a weakening Walker circulation in the Indian Ocean sector in austral winter, which is in part forced by the rapid Indian Ocean warming. Thus, although the occurrence of the unseasonable IOD may be partially influenced by oceanic variability, the authors’ results suggest an influence from the Indian Ocean warming. This suggestion, however, awaits further investigation using fully coupled climate models.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-12-00047.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2013
    detail.hit.zdb_id: 246750-1
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  • 9
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    Indo-Pacific–Induced Wave Trains during Austral Autumn and Their Effect on Australian Rainfall
    American Meteorological Society ; 2014
    In:  Journal of Climate Vol. 27, No. 9 ( 2014-05-01), p. 3208-3221
    Details
    In: Journal of Climate, American Meteorological Society, Vol. 27, No. 9 ( 2014-05-01), p. 3208-3221
    Abstract: During austral winter and spring, the El Niño–Southern Oscillation (ENSO) and the Indian Ocean dipole (IOD), individually or in combination, induce equivalent-barotropic Rossby wave trains, affecting midlatitude Australian rainfall. In autumn, ENSO is at its annual minimum, and the IOD has usually not developed. However, there is still a strong equivalent-barotropic Rossby wave train associated with tropical Indian Ocean sea surface temperature (SST) variability, with a pressure anomaly to the south of Australia. This wave train is similar in position, but opposite in sign, to the IOD-induced wave train in winter and spring and has little effect on Australian rainfall. This study shows that the SST in the southeastern tropical Indian Ocean (SETIO) displays a high variance during austral autumn, with a strong influence on southeast and eastern Australian rainfall. However, this influence is slightly weaker than that associated with SST to the north of Australia, which shares fluctuations with SST in the SETIO region. The SST north of Australia is coherent with a convective dipole in the tropical Pacific Ocean, which is the source of a wave train to the east of Australia influencing rainfall in eastern Australia. ENSO Modoki is a contributor to the convective dipole and as a result it exerts a weak influence on eastern Australian rainfall through the connecting north Australian SST relationship. Thus, SST to the north of Australia acts as the main agent for delivering the impact of tropical Indo-Pacific variability to eastern Australia.
    Type of Medium: Online Resource
    ISSN: 0894-8755 , 1520-0442
    URL: Article
    DOI: 10.1175/JCLI-D-13-00611.1
    RVK:
    UA 4548
    Language: English
    Publisher: American Meteorological Society
    Publication Date: 2014
    detail.hit.zdb_id: 246750-1
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  • 10
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    Online Resource
    More extreme swings of the South Pacific convergence zone due to greenhouse warming
    Springer Science and Business Media LLC ; 2012
    In:  Nature Vol. 488, No. 7411 ( 2012-8), p. 365-369
    Details
    In: Nature, Springer Science and Business Media LLC, Vol. 488, No. 7411 ( 2012-8), p. 365-369
    Type of Medium: Online Resource
    ISSN: 0028-0836 , 1476-4687
    URL: Article
    DOI: 10.1038/nature11358
    RVK:
    TA 1000
    RVK:
    UA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2012
    detail.hit.zdb_id: 120714-3
    detail.hit.zdb_id: 1413423-8
    SSG: 11
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