Enhanced MJO and transition to superrotation in warm climates

Carlson, Henrik; Caballero, Rodrigo

doi:10.1002/2015ms000615

Cited by 27 publications

(40 citation statements)

References 42 publications

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“…The key results presented in this paper-that ocean warming leads to a stronger MJO that is more frequent and which traverses a larger region of the tropics-are consistent with the results of the observational and modeling studies discussed above [11][12][13][14][15]17,19]. Moreover, the proposed mechanism of MJO intensification with warming oceans, enhanced surface fluxes owing to the non-linear nature of the Clausius-Clapeyron equation, is closely related to the steeper vertical gradient in moisture noted in several earlier climate warming experiments with an intensifying MJO [15,17,38].…”

Section: Discussionsupporting

confidence: 88%

“…Moreover, the proposed mechanism of MJO intensification with warming oceans, enhanced surface fluxes owing to the non-linear nature of the Clausius-Clapeyron equation, is closely related to the steeper vertical gradient in moisture noted in several earlier climate warming experiments with an intensifying MJO [15,17,38]. The vertical and horizontal structure of the MJO in the LAM is also consistent with observations, both for the mature stage (e.g., Figures 2a,b, 3a,b, and 4a,b), and for the other stages [23].…”

Section: Discussionmentioning

confidence: 87%

“…A steeper vertical gradient in moisture-a direct result of warming oceans-led to the MJO intensification. Carlson and Caballero [17] noted enhanced MJO-like activity in aquaplanet simulations with increasing CO 2 concentrations, which led to equatorial superrotation. Song and Seo [18] compared MJO activity in 19th and 20th century coupled climate simulations, and they found a 33 percent increase in MJO amplitude between the centuries, which they attributed to increasing sea surface temperatures (SSTs) in the central and eastern Pacific.…”

Section: Introductionmentioning

confidence: 95%

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Sensitivity of the Madden Julian Oscillation to Ocean Warming in a Lagrangian Atmospheric Model

Haertel

2018

Climate

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Abstract:The Madden Julian Oscillation (MJO) is the largest contributor to intraseasonal weather variations in the tropics. It is associated with a broad region of enhanced rainfall that moves slowly eastward over the Indian and western Pacific Oceans, which has global impacts on atmospheric circulations. A number of recent observational and modeling studies have suggested that the MJO is becoming stronger as the oceans warm. In this study, the author explores the sensitivity of the MJO to ocean warming in a recently developed Lagrangian Atmospheric Model (LAM), which has been shown to simulate robust and realistic MJOs in previous work. Numerical simulations suggest that ocean warming leads to more frequent and intense MJOs that propagate more rapidly and cover a larger region of the tropics. The strengthening of the MJO is attributed to enhanced surface fluxes of moisture coming from the warmer ocean waters. While the LAM simulations have a number of limitations owing to idealized physical parameterizations and the use of prescribed sea surface temperatures, they provide additional evidence that the MJO will strengthen if the oceans continue to warm, and they also shed light on the mechanism of this strengthening.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 95%

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Sensitivity of the Madden Julian Oscillation to Ocean Warming in a Lagrangian Atmospheric Model

Haertel

2018

Climate

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“…Much of the sub-seasonal variability in the tropics is due to the MaddenJulian oscillation (MJO). As discussed elsewhere (Caballero and Huber, 2010;Arnold et al, 2014;Carlson and Caballero, 2016), warm climates show a strongly enhanced MJO in a range of climate models including the one used here. It is possible that the MJO is more muted in the LCTC simulation, perhaps because of changes in the Walker cell, but we do not investigate this issue further here.…”

Section: Climatologiesmentioning

confidence: 99%

Atmospheric circulation and hydroclimate impacts of alternative warming scenarios for the Eocene

Carlson

Caballero

2017

Clim. Past

Self Cite

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Abstract. Recent work in modelling the warm climates of the early Eocene shows that it is possible to obtain a reasonable global match between model surface temperature and proxy reconstructions, but only by using extremely high atmospheric CO 2 concentrations or more modest CO 2 levels complemented by a reduction in global cloud albedo. Understanding the mix of radiative forcing that gave rise to Eocene warmth has important implications for constraining Earth's climate sensitivity, but progress in this direction is hampered by the lack of direct proxy constraints on cloud properties. Here, we explore the potential for distinguishing among different radiative forcing scenarios via their impact on regional climate changes. We do this by comparing climate model simulations of two end-member scenarios: one in which the climate is warmed entirely by CO 2 (which we refer to as the greenhouse gas (GHG) scenario) and another in which it is warmed entirely by reduced cloud albedo (which we refer to as the "low CO 2 -thin clouds" or LCTC scenario) . The two simulations have an almost identical global-mean surface temperature and equator-to-pole temperature difference, but the LCTC scenario has ∼ 11 % greater global-mean precipitation than the GHG scenario. The LCTC scenario also has cooler midlatitude continents and warmer oceans than the GHG scenario and a tropical climate which is significantly more El Niño-like. Extremely high warm-season temperatures in the subtropics are mitigated in the LCTC scenario, while cool-season temperatures are lower at all latitudes. These changes appear large enough to motivate further, more detailed study using other climate models and a more realistic set of modelling assumptions.

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“…GCMs with various degrees of MJO simulation fidelity have been used to examine the response of the MJO to warming. While an accurate simulation of the MJO is a challenging task for many contemporary GCMs (Ahn et al, ; Jiang et al, ), many of these modeling studies have suggested an amplification of MJO variability and an increase in the frequency of the MJO in a warmer climate (Arnold et al, ; Carlson & Caballero, ; Chang et al, ; Liu, ; Liu et al, ; Song & Seo, ; Subramanian et al, ; Pritchard & Yang, ). With an atmosphere‐only GCM, Arnold et al () found MJO variability more than tripled as a response to an imposed 9°C SST increase.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Moist Processes Associated With Changes in the Propagation of the MJO With Increasing CO₂

Adames

Kim

Sobel

et al. 2017

J Adv Model Earth Syst

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The processes that lead to changes in the propagation and maintenance of the Madden‐Julian Oscillation (MJO) as a response to increasing CO 2 are examined by analyzing moist static energy budget of the MJO in a series of NASA GISS model simulations. It is found changes in MJO propagation is dominated by several key processes. Horizontal moisture advection, a key process for MJO propagation, is found to enhance predominantly due to an increase in the mean horizontal moisture gradients. The terms that determine the strength of the advecting wind anomalies, the MJO horizontal scale and the dry static stability, are found to exhibit opposing trends that largely cancel out. Furthermore, reduced sensitivity of precipitation to changes in column moisture, i.e., a lengthening in the convective moisture adjustment time scale, also opposes enhanced propagation. The dispersion relationship of Adames and Kim, which accounts for all these processes, predicts an acceleration of the MJO at a rate of ∼3.5% K −1 , which is consistent with the actual phase speed changes in the simulation. For the processes that contribute to MJO maintenance, it is found that damping by vertical MSE advection is reduced due to the increasing vertical moisture gradient. This weaker damping is nearly canceled by weaker maintenance by cloud‐radiative feedbacks, yielding the growth rate from the linear moisture mode theory nearly unchanged with the warming. Furthermore, the estimated growth rates are found to be a small, negative values, suggesting that the MJO in the simulation is a weakly damped mode.

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Enhanced MJO and transition to superrotation in warm climates

Cited by 27 publications

References 42 publications

Sensitivity of the Madden Julian Oscillation to Ocean Warming in a Lagrangian Atmospheric Model

Sensitivity of the Madden Julian Oscillation to Ocean Warming in a Lagrangian Atmospheric Model

Atmospheric circulation and hydroclimate impacts of alternative warming scenarios for the Eocene

Characterization of Moist Processes Associated With Changes in the Propagation of the MJO With Increasing CO₂

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Enhanced MJO and transition to superrotation in warm climates

Cited by 27 publications

References 42 publications

Sensitivity of the Madden Julian Oscillation to Ocean Warming in a Lagrangian Atmospheric Model

Sensitivity of the Madden Julian Oscillation to Ocean Warming in a Lagrangian Atmospheric Model

Atmospheric circulation and hydroclimate impacts of alternative warming scenarios for the Eocene

Characterization of Moist Processes Associated With Changes in the Propagation of the MJO With Increasing CO2

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Product

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Characterization of Moist Processes Associated With Changes in the Propagation of the MJO With Increasing CO₂