Representing Equilibrium and Nonequilibrium Convection in Large-Scale Models

Bechtold, Peter; Semane, N.; Lopez, Philippe; Chaboureau, Jean‐Pierre; Beljaars, Anton; Bormann, Niels

doi:10.1175/jas-d-13-0163.1

Cited by 325 publications

(353 citation statements)

References 71 publications

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“…The diurnal cycle of the present-day Earth climate can be analysed by performing a Fourier series of desired quantities. The magnitude and phase of these quantities are thus obtained (Bechtold et al 2014). This method could also be applied to long rotation periods, but we choose to analyse the day-to-night characteristics at different P rot by computing temporal averages with respect to the time of day.…”

Section: The Diurnal Contrast At the Surfacementioning

confidence: 99%

The role of sea-ice albedo in the climate of slowly rotating aquaplanets

2017

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We investigate the influence of the rotation period (Prot) on the mean climate of an aquaplanet, with a focus on the role of sea-ice albedo. We perform aquaplanet simulations with the atmospheric general circulation model ECHAM6 for various rotation periods from one Earth-day to 365 Earth-days in which case the planet is synchronously rotating. The global-mean surface temperature decreases with increasing Prot and sea ice expands equatorwards. The cooling of the mean climate with increasing Prot is caused partly by the high surface albedo of sea ice on the dayside and partly by the high albedo of the deep convective clouds over the substellar region. The cooling caused by these deep convective clouds is weak for non-synchronous rotations compared to synchronous rotation. Sensitivity simulations with the sea-ice model switched off show that the global-mean surface temperature is up to 27 K higher than in our main simulations with sea ice and thus highlight the large influence of sea ice on the climate. We present the first estimates of the influence of the rotation period on the transition of an Earth-like climate to global glaciation. Our results suggest that global glaciation of planets with synchronous rotation occurs at substantially lower incoming solar irradiation than for planets with slow but non-synchronous rotation

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Section: The Diurnal Contrast At the Surfacementioning

confidence: 99%

The role of sea-ice albedo in the climate of slowly rotating aquaplanets

2017

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“…convection to improve the diurnal cycle of rainfall over this region [Dai, 2006;Bechtold et al, 2014;Tanaka et al, 2014].…”

Section: Journal Of Advances In Modeling Earth Systems 101002/2016msmentioning

confidence: 99%

Effects of explicit convection on global land‐atmosphere coupling in the superparameterized CAM

Sun

Pritchard

2016

J Adv Model Earth Syst

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Conventional global climate models are prone to producing unrealistic land‐atmosphere coupling signals. Cumulus and convection parameterizations are natural culprits but the effect of bypassing them with explicitly resolved convection on global land‐atmosphere coupling dynamics has not been explored systematically. We apply a suite of modern land‐atmosphere coupling diagnostics to isolate the effect of cloud Superparameterization in the Community Atmosphere Model (SPCAM) v3.5, focusing on both the terrestrial segment (i.e., soil moisture and surface turbulent fluxes interaction) and atmospheric segment (i.e., surface turbulent fluxes and precipitation interaction) in the water pathway of the land‐atmosphere feedback loop. At daily timescales, SPCAM produces stronger uncoupled terrestrial signals (negative sign) over tropical rainforests in wet seasons, reduces the terrestrial coupling strength in the Central Great Plain in American, and reverses the coupling sign (from negative to positive) over India in the boreal summer season—all favorable improvements relative to reanalysis‐forced land modeling. Analysis of the triggering feedback strength (TFS) and amplification feedback strength (AFS) shows that SPCAM favorably reproduces the observed geographic patterns of these indices over North America, with the probability of afternoon precipitation enhanced by high evaporative fraction along the eastern United States and Mexico, while conventional CAM does not capture this signal. We introduce a new diagnostic called the Planetary Boundary Layer (PBL) Feedback Strength (PFS), which reveals that SPCAM exhibits a tight connection between the responses of the lifting condensation level, the PBL height, and the rainfall triggering to surface turbulent fluxes; a triggering disconnect is found in CAM.

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“…These changes led to significant improvements in the representation of the atmospheric variability in the ECMWF model. Simulations of the diurnal timing of precipitation have also benefited from comparisons between convection-resolving idealized models and global, highly parameterized models [Rio et al, 2009;Bechtold et al, 2014].…”

Section: Introductionmentioning

confidence: 99%

Radiative convective equilibrium as a framework for studying the interaction between convection and its large‐scale environment

Silvers

Stevens

Mauritsen

et al. 2016

J Adv Model Earth Syst

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An uncertain representation of convective clouds has emerged as one of the key barriers to our understanding of climate sensitivity. The large gap in resolved spatial scales between General Circulation Models (GCMs) and high resolution models has made a systematic study of convective clouds across model configurations difficult. It is shown here that the simulated atmosphere of a GCM in Radiative Convective Equilibrium (RCE) is sufficiently similar across a range of domain sizes to justify the use of RCE to study both a GCM and a high resolution model on the same domain with the goal of improved constraints on the parameterized clouds. Simulations of RCE with parameterized convection have been analyzed on domains with areas spanning more than two orders of magnitude ( ), all having the same grid spacing of . The simulated climates on different domains are qualitatively similar in their degree of convective organization, the precipitation rates, and the vertical structure of the clouds and water vapor, with the similarity increasing as the domain size increases. Sea surface temperature perturbation experiments are used to estimate the climate feedback parameter for the differently configured experiments, and the cloud radiative effect is computed to examine the role which clouds play in the response. Despite the similar climate states between the domains the feedback parameter varies by more than a factor of two; the hydrological sensitivity parameter is better behaved, varying by a factor of 1.4. The sensitivity of the climate feedback parameter to domain size is related foremost to a nonsystematic response of low‐level clouds as well as an increasingly negative longwave feedback on larger domains.

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Representing Equilibrium and Nonequilibrium Convection in Large-Scale Models

Cited by 325 publications

References 71 publications

The role of sea-ice albedo in the climate of slowly rotating aquaplanets

The role of sea-ice albedo in the climate of slowly rotating aquaplanets

Effects of explicit convection on global land‐atmosphere coupling in the superparameterized CAM

Radiative convective equilibrium as a framework for studying the interaction between convection and its large‐scale environment

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