Fundamental Moist Modes of the Equatorial Troposphere

Raymond, David J.; Torres, David J.

doi:10.1175/1520-0469(1998)055<1771:fmmote>2.0.co;2

Cited by 34 publications

(28 citation statements)

References 42 publications

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“…Table II lists the values of parameters used in the cumulus and surface-flux parametrizations. The radiation parametrization is that presented in Raymond and Torres (1998) and Raymond (2000aRaymond ( , 2001.…”

Section: Discussionmentioning

confidence: 99%

“…The calculations with the cumulus ensemble model are now repeated with a slightly updated version of the toy cumulus parametrization of Raymond and Torres (1998) and Raymond (2000aRaymond ( , 2001. The same fixed radiativecooling and surface-flux formulations are used as in the cumulus ensemble model calculations.…”

Section: Convective-rain Parametrizationmentioning

confidence: 99%

“…The cumulus parametrization is descended from that of (Raymond and Torres, 1998) and (Raymond, 2000a(Raymond, , 2001. It is an adjustment scheme, with separate calculations made for shallow and deep convection.…”

Section: Appendix: the Cumulus Parametrizationmentioning

confidence: 99%

“…In Section 3 we modify the cumulus parametrization of (Raymond and Torres, 1998) and (Raymond, 2000a(Raymond, , 2001 to match the results of the cumulus ensemble model, and in Section 4 we explore the effects of these modifications on the power spectra of modelled synoptic and intraseasonal disturbances over tropical oceans. Results are summarized, and conclusions drawn, in Section 5.…”

Section: Introductionmentioning

confidence: 99%

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Testing a cumulus parametrization with a cumulus ensemble model in weak‐temperature‐gradient mode

Raymond

2007

Quart J Royal Meteoro Soc

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This paper prototypes a method for calibrating a cumulus parametrization against a cumulus ensemble model. The key to this technique is to run the cumulus model and the parametrization in identical 'test cells' that provide forcing typical of that seen over tropical oceans. In particular, the mean temperature profile is relaxed to a reference profile that is assumed to be characteristic of the environment of the convection. This is done by calculating the mean vertical velocity needed to balance heating due to convection, latent-heat release, and radiation with adiabatic cooling. This 'weak-temperature-gradient' vertical-velocity profile is then used to advect moisture vertically and, via mass continuity, through the sides of the test cell, entraining reference-profile air as needed.As an example, a toy cumulus parametrization used previously is altered to reproduce the dependence of rainfall rate on surface wind speed shown by the cumulus ensemble model. This alteration greatly changes the behaviour of simulated large-scale disturbances in an aquaplanet equatorial beta-plane model. In particular, increasing the slope of the curve of rainfall rate against wind speed results in the development of much greater synoptic-scale variance.

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Section: Discussionmentioning

confidence: 99%

Section: Convective-rain Parametrizationmentioning

confidence: 99%

Section: Appendix: the Cumulus Parametrizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Testing a cumulus parametrization with a cumulus ensemble model in weak‐temperature‐gradient mode

Raymond

2007

Quart J Royal Meteoro Soc

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“…Previous studies have shown that the fidelity of the MJO in global models is sensitive to the cumulus parameterization applied in these models (e.g., Raymond and Torres 1998;Wang and Schlesinger 1999;Maloney and Hartman 2001). However, there appears to be no satisfactory consensus.…”

Section: Cumulus Parameterizationmentioning

confidence: 99%

Role of the atmospheric mean state on the initiation of the Madden-Julian oscillation in a tropical channel model

et al. 2010

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Tropical channel models, defined as models that are global in the zonal direction but bounded in the meridional direction, are particularly useful for simulating the Madden-Julian oscillation (MJO) and understanding its physical and dynamical basis. Influences from the extratropics through the lateral boundaries have been found to be essential to the reproduction of the initiation of certain MJO events. This led to a hypothesis that multi-year simulations using a tropical channel model would reproduce reasonable MJO statistics under the influence of prescribed lateral boundary conditions derived from global reanalyses. Interestingly, the MJO statistics in such a multi-year simulation by a high-resolution tropical channel model are not better than those from global climate models. The error in the atmospheric mean state is found to be a possible reason for the poor MJO statistics in the simulation. Nevertheless, even with a large error in the mean state, the multi-year simulation captures two MJO events previously found to be initiated by extratropical influences. However, the model does not reproduce a third event, whose initiation is not directly influenced by the extratropics. This implies that in the absence of dynamical interactions between the MJO and the lateral boundary conditions, the error in the mean state could be sufficient to prevent the MJO initiation. To explore this third MJO event further, a series of sensitivity tests are conducted. These tests show that the simulation of this event is neither critically influenced by the cumulus parameterization employed, nor the initial conditions when the model is integrated 2 weeks prior to the MJO initiation. The model captures this event when the MJO signal is already present in the initial conditions. The use of highresolution sea surface temperature does not improve the simulation of the third MJO event. A higher-resolution nested domain covering the Indo-Pacific warm pool region and including a cloud-system resolving domain over the Indonesian Maritime Continent has little effect on the MJO initiation over the Indian Ocean. In \2 weeks the error in the simulation is comparable to the climate error. The role of the simulated MJO on the mean state is also explored. Implications and limitations of these results are discussed.

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Convective response to changes in the thermodynamic environment in idealized weak temperature gradient simulations

Sessions

Herman

Sentić

2015

J Adv Model Earth Syst

112

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We investigate the response of convection to idealized perturbations in the thermodynamic environment in simulations which parameterize the large-scale circulations using the weak temperature gradient (WTG) approximation. The perturbations include a combination of modifying the environmental moisture and atmospheric stability via imposing anomalies in reference moisture and temperature profiles. We find that changes in atmospheric stability strongly influence the character of convection by drastically modifying the vertical motion profile, whereas changes to atmospheric moisture modulate the intensity of precipitation produced by the convection, but do not qualitatively change the shape of the vertical motion profile. An important question is how does horizontal moisture advection into the domain affect convection? We test several different parameterizations of this process; these include lateral entrainment by circulations induced by enforcing WTG, a moisture relaxation which parameterizes the advection of moisture by large-scale nondivergent circulations, and control simulations in which both of these mechanisms are turned off so horizontal advection is assumed negligible compared to vertical advection. Interestingly, the most significant differences resulting from the choice of horizontal moisture advection scheme appear in environmental conditions which suppress-rather than support-the development of deep tropical convection. In this case, lateral entrainment related to WTG circulations is the only parameterization which results in extreme drying of the troposphere in environments which suppress convection. Consequently, this is the only parameterization which permits multiple equilibria-dry or precipitating steady states-in convection.

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Fundamental Moist Modes of the Equatorial Troposphere

Cited by 34 publications

References 42 publications

Testing a cumulus parametrization with a cumulus ensemble model in weak‐temperature‐gradient mode

Testing a cumulus parametrization with a cumulus ensemble model in weak‐temperature‐gradient mode

Role of the atmospheric mean state on the initiation of the Madden-Julian oscillation in a tropical channel model

Convective response to changes in the thermodynamic environment in idealized weak temperature gradient simulations

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