Boundary Layer Diabatic Processes, the Virtual Effect, and Convective Self‐Aggregation

Yang, Da

doi:10.1029/2017ms001261

Cited by 61 publications

(168 citation statements)

References 32 publications

(72 reference statements)

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“…Describing extremes may be accomplished by our model, by coupling precipitation intensity and gust front speed, thereby relaxing the assumption of constant speed c 0 . Further, due to the effect of surface heat fluxes and energy conservation, the speed of spreading should decrease with radius (Grant & van den Heever, 2016, 2018Gentine et al, 2016;Romps & Jeevanjee, 2016). Here, h denotes the effective CP height, and g is the gravitational acceleration.…”

Section: Discussionmentioning

confidence: 99%

“…Observed maximal radii in fact vary by an order of magnitude, between 10 and 100 km (Black, 1978;Feng et al, 2015;Zuidema et al, 2012). This may also help to better assess models of self-organization, such as those employed in the idealized self-aggregation case (Holloway, 2017;Holloway et al, 2017;Wing & Cronin, 2016;Wing et al, 2017;Yang, 2018). This may also help to better assess models of self-organization, such as those employed in the idealized self-aggregation case (Holloway, 2017;Holloway et al, 2017;Wing & Cronin, 2016;Wing et al, 2017;Yang, 2018).…”

Section: 1029/2019gl082092mentioning

confidence: 94%

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Circling in on Convective Organization

Haerter

Böing

Henneberg

et al. 2019

Geophysical Research Letters

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Cold pools (CPs) contribute to convective organization. However, it is unclear by which mechanisms organization occurs. By using a particle method to track CP gust fronts in large eddy simulations, we characterize the basic collision modes between CPs. Our results show that CP interactions, where three expanding gust fronts force an updraft, are key at triggering new convection. Using this, we conceptualize CP dynamics into a parameter‐free mathematical model: circles expand from initially random points in space. Where two expanding circles collide, a stationary front is formed. However, where three expanding circles enclose a single point, a new expanding circle is seeded. This simple model supports three fundamental features of CP dynamics: precipitation cells constitute a spatially interacting system, CPs come in generations, and scales steadily increase throughout the diurnal cycle. Finally, this model provides a framework for how CPs act to cause convective self‐organization, clustering, and extremes.

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Section: Discussionmentioning

confidence: 99%

Section: 1029/2019gl082092mentioning

confidence: 94%

Circling in on Convective Organization

Haerter

Böing

Henneberg

et al. 2019

Geophysical Research Letters

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“…An atmosphere can spontaneously organize into a large‐scale overturning circulation in radiative‐convective equilibrium simulations (Arnold & Randall, ; Becker & Stevens, ; Bretherton et al, ; Held et al, ; Wing & Emanuel, ; Yang, , ). The atmosphere is anomalously moist over the upwelling brach of the circulation, where convection is ubiquitous; the atmosphere is anomalously dry over the downwelling branch of the circulation, where clear‐sky conditions prevail.…”

Section: Introductionmentioning

confidence: 99%

“…Because cold pools are associated with evaporation‐driven downdrafts, with most parcels originating within 1.5 km from the surface (Torri & Kuang, ), Jeevanjee and Romps () have largely eliminated cold pools, allowing convection to self‐aggregate. The other considers that convective self‐aggregation is associated with the generation of available potential energy (APE), which is the energy reservoir for circulations (Yang, ). Rain evaporation cools the buoyant part of the atmosphere (boundary layer of the convecting columns), reducing APE and, therefore, inhibiting self‐aggregation.…”

Section: Introductionmentioning

confidence: 99%

“…Rain evaporation cools the buoyant part of the atmosphere (boundary layer of the convecting columns), reducing APE and, therefore, inhibiting self‐aggregation. By focusing on the APE budget, Yang () discovered that the vapor buoyancy effect helps convection self‐aggregate and showed that enhanced vapor buoyancy could lead to self‐aggregation even without radiative feedbacks because the vapor buoyancy contributes to generate APE.…”

Section: Introductionmentioning

confidence: 99%

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Convective Heating Leads to Self‐Aggregation by Generating Available Potential Energy

Yang

2019

Geophysical Research Letters

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The moisture‐entrainment‐convection (MEC) feedback posits that a moist environment favors deep convection, which further moistens the atmosphere through its associated circulation and detrainment. The MEC feedback has been proposed to be crucial to spontaneous convective aggregation. Here we test this hypothesis by performing minimal cloud‐resolving simulations, without the buoyancy effect due to water vapor, evaporation of rain, or radiative and surface‐flux feedbacks. Convection can self‐aggregate in this minimal simulation, in which the MEC feedback is active. We then switch off this feedback by relaxing moisture to its horizontal mean over a time scale of 3 hr. Convection still self‐aggregates in this mechanism‐denial experiment, suggesting that the MEC feedback is not essential to self‐aggregation. We further show that convective heating coincides with positive temperature anomalies, generating available potential energy. Therefore, we propose that this convective heating‐overturning circulation feedback can lead to spontaneous development of large‐scale circulations.

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Modulation of the Bifurcation in Radiative-Convective Equilibrium by Gray-Zone Cloud and Turbulence Parameterizations

Shi

Fan

2021

Preprint

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If it is the author's pre-published version, changes introduced as a result of publishing processes such as copy-editing and formatting may not be reflected in this document. For a definitive version of this work, please refer to the published version.Thanks to the advances in computing power, modern numerical weather prediction (NWP) has achieved regional resolutions of  E 1 km (Lean et al., 2008;Raynaud & Bouttier, 2017;Seity et al., 2011). Global simulations at kilometer-scale resolutions are also actively achieved by the modeling community (Wedi et al., 2020). However, grid spacings of such sizes also inhibit further improvement of weather and climate models due to some phenomena, such as turbulence in the gray zone (also known as terra incognita). The gray zone refers to situations in which the model mesh cannot fully resolve turbulence and in which turbulence cannot be assumed to be mostly unresolved and in a quasi-equilibrium state (Chow et al., 2019;Wyngaard, 2004). Since such assumptions form the basis of traditional turbulence models in large-eddy simulations (LES) and NWP models, both LES-type and NWP-type turbulence models may underperform in the gray zone.

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Boundary Layer Diabatic Processes, the Virtual Effect, and Convective Self‐Aggregation

Cited by 61 publications

References 32 publications

Circling in on Convective Organization

Circling in on Convective Organization

Convective Heating Leads to Self‐Aggregation by Generating Available Potential Energy

Modulation of the Bifurcation in Radiative-Convective Equilibrium by Gray-Zone Cloud and Turbulence Parameterizations

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