Southern Hemisphere atmospheric circulation response to the El Chichón and Pinatubo eruptions in coupled climate models

Karpechko, Alexey Yu.; Gillett, Nathan P.; Dall'Amico, Mauro; Gray, Lesley J.

doi:10.1002/qj.683

Cited by 33 publications

(47 citation statements)

References 31 publications

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“…9b,c). These results suggest that although the forced circulation response to Pinatubo appears to be a positive annular mode pattern [as simulated by the CMIP5 models and consistent with the CMIP3 model results of Karpechko et al (2010)], this forced response may be difficult to detect in the observations in the presence of climate variability.…”

Section: Discussion Of Climate Variabilitysupporting

confidence: 57%

“…9a). While the observed negative SAM has led some studies to suggest that volcanic eruptions may force the circulation into a negative SAM state (e.g., Roscoe and Haigh 2007), other studies have suggested that the El Niño state during and immediately following the eruption may have hidden the forced positive SAM response (e.g., Karpechko et al 2010). The circulation response to El Niño is a negative SAM-like pattern (e.g., L'Heureux and Thompson 2006), and thus, this may have partially or entirely canceled the positive SAM response to the Pinatubo eruption.…”

Section: Discussion Of Climate Variabilitymentioning

confidence: 99%

“…In accordance with this, we demonstrated a robust positive SAM response to the Mount Pinatubo eruption across the CMIP5 models. Thus, it is likely that the planetary wave dynamics outlined by Perlwitz and Graf (1995) also apply to the Southern Hemisphere response [see discussion by Karpechko et al (2010)]. Furthermore, while it is possible that model biases in polar vortex strength may modify the CMIP5 models' circulation response as suggested by Ottera (2008) and Stenchikov et al (2006), such effects do not appear to dominate the CMIP5 model responses.…”

Section: Discussionmentioning

confidence: 99%

“…Robock et al (2007) found no response of the SAM in the stratosphere or troposphere to the Pinatubo eruption in the NASA GISS model and suggested that the SH response could be weaker than the NH response because of a ''more steady jet and vortex.' ' Karpechko et al (2010) analyzed the composite responses to the El Chichón and Pinatubo eruptions in the suite of models in phase 3 of the Coupled Model Intercomparison Project (CMIP3) and found a significant response projecting on the positive phase of the SAM in both the stratosphere and troposphere during austral spring and autumn following the eruptions.…”

Section: Introductionmentioning

confidence: 99%

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Robust Wind and Precipitation Responses to the Mount Pinatubo Eruption, as Simulated in the CMIP5 Models

2016

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The volcanic eruption of Mount Pinatubo in June 1991 is the largest terrestrial eruption since the beginning of the satellite era. Here, the monthly evolution of atmospheric temperature, zonal winds, and precipitation following the eruption in 14 CMIP5 models is analyzed and strong and robust stratospheric and tropospheric circulation responses are demonstrated in both hemispheres, with tropospheric anomalies maximizing in November 1991. The simulated Southern Hemisphere circulation response projects strongly onto the positive phase of the southern annular mode (SAM), while the Northern Hemisphere exhibits robust North Atlantic and North Pacific responses that differ significantly from that of the typical northern annular mode (NAM) pattern. In contrast, observations show a negative SAM following the eruption, and internal variability must be considered along with forced responses. Indeed, evidence is presented that the observed El Niño climate state during and after this eruption may oppose the eruption-forced positive SAM response, based on the El Niño-Southern Oscillation (ENSO) state and SAM response across the models. The results demonstrate that Pinatubo-like eruptions should be expected to force circulation anomalies across the globe and highlight that great care must be taken in diagnosing the forced response as it may not fall into typical seasonal averages or be guaranteed to project onto typical climate modes.

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Section: Discussion Of Climate Variabilitysupporting

confidence: 57%

Section: Discussion Of Climate Variabilitymentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Robust Wind and Precipitation Responses to the Mount Pinatubo Eruption, as Simulated in the CMIP5 Models

2016

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“…Comparatively little attention has been given to the Southern Hemisphere, or to South America specifically (although see Joseph andZeng, 2011, andWilmes et al, 2012). Some previous work has focused on the Southern Annular Mode in the ERA-40 and NCEP/NCAR reanalysis, in addition to a previous version of NASA Goddard Institute for Space Studies (GISS) Model-E (Robock et al, 2007) and in a subset of CMIP3 models (Karpechko et al, 2010) or in CMIP5 (Gillett and Fyfe, 2013).…”

Section: Volcanic Forcing On Climatementioning

confidence: 99%

The influence of volcanic eruptions on the climate of tropical South America during the last millennium in an isotope-enabled general circulation model

2016

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Abstract. Currently, little is known on how volcanic eruptions impact large-scale climate phenomena such as South American paleo-Intertropical Convergence Zone (ITCZ) position and summer monsoon behavior. In this paper, an analysis of observations and model simulations is employed to assess the influence of large volcanic eruptions on the climate of tropical South America. This problem is first considered for historically recent volcanic episodes for which more observations are available but where fewer events exist and the confounding effects of El Niño-Southern Oscillation (ENSO) lead to inconclusive interpretation of the impact of volcanic eruptions at the continental scale. Therefore, we also examine a greater number of reconstructed volcanic events for the period 850 CE to present that are incorporated into the NASA GISS ModelE2-R simulation of the last millennium.An advantage of this model is its ability to explicitly track water isotopologues throughout the hydrologic cycle and simulating the isotopic imprint following a large eruption. This effectively removes a degree of uncertainty associated with error-prone conversion of isotopic signals into climate variables, and allows for a direct comparison between GISS simulations and paleoclimate proxy records.Our analysis reveals that both precipitation and oxygen isotope variability respond with a distinct seasonal and spatial structure across tropical South America following an eruption. During austral winter, the heavy oxygen isotope in precipitation is enriched, likely due to reduced moisture convergence in the ITCZ domain and reduced rainfall over northern South America. During austral summer, however, more negative values of the precipitation isotopic composition are simulated over Amazonia, despite reductions in rainfall, suggesting that the isotopic response is not a simple function of the "amount effect". During the South American monsoon season, the amplitude of the temperature response to volcanic forcing is larger than the rather weak and spatially less coherent precipitation signal, complicating the isotopic response to changes in the hydrologic cycle.

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Reconciling the observed and modeled Southern Hemisphere circulation response to volcanic eruptions

McGraw

Barnes

Deser

2016

Geophysical Research Letters

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Confusion exists regarding the tropospheric circulation response to volcanic eruptions, with models and observations seeming to disagree on the sign of the response. The forced Southern Hemisphere circulation response to the eruptions of Pinatubo and El Chichón is shown to be a robust positive annular mode, using over 200 ensemble members from 38 climate models. It is demonstrated that the models and observations are not at odds, but rather, internal climate variability is large and can overwhelm the forced response. It is further argued that the state of the El Niño–Southern Oscillation can at least partially explain the sign of the observed anomalies and may account for the perceived discrepancy between model and observational studies. The eruptions of both El Chichón and Pinatubo occurred during El Niño events, and it is demonstrated that the Southern Annular Mode anomalies following volcanic eruptions are weaker during El Niño events compared to La Niña events.

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Southern Hemisphere atmospheric circulation response to the El Chichón and Pinatubo eruptions in coupled climate models

Cited by 33 publications

References 31 publications

Robust Wind and Precipitation Responses to the Mount Pinatubo Eruption, as Simulated in the CMIP5 Models

Robust Wind and Precipitation Responses to the Mount Pinatubo Eruption, as Simulated in the CMIP5 Models

The influence of volcanic eruptions on the climate of tropical South America during the last millennium in an isotope-enabled general circulation model

Reconciling the observed and modeled Southern Hemisphere circulation response to volcanic eruptions

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