Shallow Cumulus Research Articles

The interaction of moist convection and mid‐level dry air in the advance of the onset of the Indian monsoon

The advance of the onset of the Indian monsoon is here explained in terms of a balance between the low‐level monsoon flow and an overrunning intrusion of mid‐tropospheric dry air. The monsoon advances, over a period of about 6 weeks, from the south of the country to the northwest. Given that the low‐level monsoon winds are westerly or southwesterly, and the mid‐level winds northwesterly, the monsoon onset propagates upwind relative to mid‐level flow, and perpendicular to the low‐level flow, and is not directly caused by moisture flux toward the northwest. Lacking a conceptual model for the advance means that it has been hard to understand and correct known biases in weather and climate prediction models.The mid‐level northwesterlies form a wedge of dry air that is deep in the far northwest of India and over‐runs the monsoon flow. The dry layer is moistened from below by shallow cumulus and congestus clouds, so that the profile becomes much closer to moist adiabatic, and the dry layer is much shallower in the vertical, toward the southeast of India. The profiles associated with this dry air show how the most favourable environment for deep convection occurs in the south, and onset occurs here first.As the onset advances across India, the advection of moisture from the Arabian Sea becomes stronger, and the mid‐level dry air is increasingly moistened from below. This increased moistening makes the wedge of dry air shallower throughout its horizontal extent, and forces the northern limit of moist convection to move toward the northwest. Wetting of the land surface by rainfall will further reinforce the north‐westward progression, by sustaining the supply of boundary‐layer moisture and shallow cumulus. The local advance of the monsoon onset is coincident with weakening of the mid‐level northwesterlies, and therefore weakened mid‐level dry advection.

A stochastic scale‐aware parameterization of shallow cumulus convection across the convective gray zone

AbstractThe parameterization of shallow cumuli across a range of model grid resolutions of kilometre‐scales faces at least three major difficulties: (1) closure assumptions of conventional parameterization schemes are no longer valid, (2) stochastic fluctuations become substantial and increase with grid resolution, and (3) convective circulations that emerge on the model grids are under‐resolved and grid‐scale dependent. Here we develop a stochastic parameterization of shallow cumulus clouds to address the first two points, and we study how this stochastic parameterization interacts with the under‐resolved convective circulations in a convective case over the ocean. We couple a stochastic model based on a canonical ensemble of shallow cumuli to the Eddy‐Diffusivity Mass‐Flux parameterization in the icosahedral nonhydrostatic (ICON) model. The moist‐convective area fraction is perturbed by subsampling the distribution of subgrid convective states. These stochastic perturbations represent scale‐dependent fluctuations around the quasi‐equilibrium state of a shallow cumulus ensemble. The stochastic parameterization reproduces the average and higher order statistics of the shallow cumulus case adequately and converges to the reference statistics with increasing model resolution. The interaction of parameterizations with model dynamics, which is usually not considered when parameterizations are developed, causes a significant influence on convection in the gray zone. The stochastic parameterization interacts strongly with the model dynamics, which changes the regime and energetics of the convective flows compared to the deterministic simulations. As a result of this interaction, the emergence of convective circulations in combination with the stochastic parameterization can even be beneficial on the high‐resolution model grids.

Representing effects of aqueous phase reactions in shallow cumuli in global models

AbstractAqueous phase reactions are important, sometimes dominant (e.g., for SO2), pathways for the oxidation of air pollutants at the local and/or global scale. In many current chemical transport models (CTMs), the transport and aqueous reactions of chemical species are treated as split processes, and the subgrid‐scale heterogeneity between cloudy and environmental air is not considered. Here using large eddy simulation (LES) with idealized aqueous reactions mimicking the oxidation of surface‐originated SO2 by H2O2 in shallow cumuli, we show that the eddy diffusivity mass flux (EDMF) approach with a bulk plume can represent those processes quite well when entrainment/detrainment rates and eddy diffusivity are diagnosed using a conservative thermodynamic variable such as total water content. The reason is that a typical aqueous reaction such as SO2 aqueous oxidation is relatively slow compared to the in‐cloud residence time of air parcels in shallow cumuli. As a result, the surface‐originated SO2 is well correlated with and behaves like conservative thermodynamic variables that also have sources at the surface. Experiments with various reaction rate constants and relative abundances of SO2 and H2O2 indicate that when the reaction timescale approaches the in‐cloud residence time of air parcels, the errors of the bulk plume approach start to increase. Treating chemical tracer transport and aqueous reaction as split processes leads to significant errors, especially when the reaction is fast compared to the in‐cloud residence time. Overall, the EDMF approach shows large improvement over the CTM‐like treatments in matching the LES results.

Clouds at Barbados are representative of clouds across the trade wind regions in observations and climate models

Trade wind regions cover most of the tropical oceans, and the prevailing cloud type is shallow cumulus. These small clouds are parameterized by climate models, and changes in their radiative effects strongly and directly contribute to the spread in estimates of climate sensitivity. This study investigates the structure and variability of these clouds in observations and climate models. The study builds upon recent detailed model evaluations using observations from the island of Barbados. Using a dynamical regimes framework, satellite and reanalysis products are used to compare the Barbados region and the broader tropics. It is shown that clouds in the Barbados region are similar to those across the trade wind regions, implying that observational findings from the Barbados Cloud Observatory are relevant to clouds across the tropics. The same methods are applied to climate models to evaluate the simulated clouds. The models generally capture the cloud radiative effect, but underestimate cloud cover and show an array of cloud vertical structures. Some models show strong biases in the environment of the Barbados region in summer, weakening the connection between the regional biases and those across the tropics. Even bearing that limitation in mind, it is shown that covariations of cloud and environmental properties in the models are inconsistent with observations. The models tend to misrepresent sensitivity to moisture variations and inversion characteristics. These model errors are likely connected to cloud feedback in climate projections, and highlight the importance of the representation of shallow cumulus convection.

Evolution of the Shape of the Raindrop Size Distribution in Simulated Shallow Cumulus

Abstract In this paper, the evolution of the raindrop size distribution (RSD) is investigated for two isolated shallow cumulus clouds that are modeled with large-eddy simulations. For a two-moment bulk rain microphysics scheme that assumes the RSD to follow a gamma distribution, it is shown that the evolution of the rainwater content of an individual shallow cumulus cloud—in particular, its subcloud-layer rainwater amount and its surface precipitation rate—is highly sensitive to the choice of the shape parameter of the gamma distribution. To further investigate the shape of the RSD, a Lagrangian drop model is used to represent warm rain microphysics without a priori assumptions on the RSD. It is found that the shape parameter is highly variable in space and time and that existing closure equations, which are established from idealized studies of more heavily precipitating cases, are not appropriate for shallow cumulus. Although a relation of the shape parameter to the mean raindrop diameter is also found for individual shallow cumulus clouds, this relation differs already for the two clouds considered. It is therefore doubtful whether a two-moment scheme with a diagnostic parameterization of the shape parameter (i.e., a local closure in space and time) can be sufficient, especially when being applied across different cloud regimes. A three-moment bulk rain microphysics scheme is able to capture the general development of the relation of the shape parameter to the mean raindrop diameter for the two simulated clouds but misses some relevant features.

The Barbados Cloud Observatory: Anchoring Investigations of Clouds and Circulation on the Edge of the ITCZ

Abstract Clouds over the ocean, particularly throughout the tropics, are poorly understood and drive much of the uncertainty in model-based projections of climate change. In early 2010, the Max Planck Institute for Meteorology and the Caribbean Institute for Meteorology and Hydrology established the Barbados Cloud Observatory (BCO) on the windward edge of Barbados. At 13°N the BCO samples the seasonal migration of the intertropical convergence zone (ITCZ), from the well-developed winter trades dominated by shallow cumulus to the transition to deep convection as the ITCZ migrates northward during boreal summer. The BCO is also well situated to observe the remote meteorological impact of Saharan dust and biomass burning. In its first six years of operation, and through complementary intensive observing periods using the German High Altitude and Long Range Research Aircraft (HALO), the BCO has become a cornerstone of efforts to understand the relationship between cloudiness, circulation, and climate change.

Dependence of entrainment in shallow cumulus convection on vertical velocity and distance to cloud edge

AbstractThe dependence of entrainment rate on environmental conditions and cloud characteristics is investigated using large eddy simulations (LES) of the response of shallow cumulus convection to a small‐amplitude temperature perturbation that is horizontally uniform and localized in height. The simulated cumulus fields are analyzed in the framework of an ensemble of entraining plumes by tracking a large number of Lagrangian parcels embedded in the LES and grouping them into different plumes based on their detrainment heights. The results show that fractional entrainment rate per unit height of a plume is inversely proportional to the plume's vertical velocity and its distance to the cloud edge, while changes in environmental stratification and relative humidity, the plume's buoyancy, or the vertical gradient of its buoyancy due to the temperature perturbation have little effect on the plume's entrainment rate.

Recirculation and growth of raindrops in simulated shallow cumulus

AbstractThis study investigates growth processes of raindrops and the role of recirculation of raindrops for the formation of precipitation in shallow cumulus. Two related cases of fields of lightly precipitating shallow cumulus are simulated using Large‐Eddy Simulation combined with a Lagrangian drop model for raindrop growth and a cloud tracking algorithm. Statistics from the Lagrangian drop model yield that most raindrops leave the cloud laterally and then evaporate in the subsaturated cloud environmental air. Only 1%–3% of the raindrops contribute to surface precipitation. Among this subsample of raindrops that contribute to surface precipitation, two growth regimes are identified: those raindrops that are dominated by accretional growth from cloud water, and those raindrops that are dominated by selfcollection among raindrops. The mean cloud properties alone are not decisive for the growth of an individual raindrop but the in‐cloud variability is crucial. Recirculation of raindrops is found to be common in shallow cumulus, especially for those raindrops that contribute to surface precipitation. The fraction of surface precipitation that is attributed to recirculating raindrops differs from cloud to cloud but can be larger than 50%. This implies that simple conceptual models of raindrop growth that neglect the effect of recirculation disregard a substantial portion of raindrop growth in shallow cumulus.

Constraining the aerosol influence on cloud fraction

AbstractAerosol‐cloud interactions have the potential to modify many different cloud properties. There is significant uncertainty in the strength of these aerosol‐cloud interactions in analyses of observational data, partly due to the difficulty in separating aerosol effects on clouds from correlations generated by local meteorology. The relationship between aerosol and cloud fraction (CF) is particularly important to determine, due to the strong correlation of CF to other cloud properties and its large impact on radiation. It has also been one of the hardest to quantify from satellites due to the strong meteorological covariations involved. This work presents a new method to analyze the relationship between aerosol optical depth (AOD) and CF. By including information about the cloud droplet number concentration (CDNC), the impact of the meteorological covariations is significantly reduced. This method shows that much of the AOD‐CF correlation is explained by relationships other than that mediated by CDNC. By accounting for these, the strength of the global mean AOD‐CF relationship is reduced by around 80%. This suggests that the majority of the AOD‐CF relationship is due to meteorological covariations, especially in the shallow cumulus regime. Requiring CDNC to mediate the AOD‐CF relationship implies an effective anthropogenic radiative forcing from an aerosol influence on liquid CF of −0.48 W m−2 (−0.1 to −0.64 W m−2), although some uncertainty remains due to possible biases in the CDNC retrievals in broken cloud scenes.

Varied pathways for simulated tropical cyclone rapid intensification. Part II: Vertical motion and cloud populations

Differences in the vertical velocity characteristics associated with various cloud populations are evaluated for two simulated cases of tropical cyclone (TC) rapid intensification (RI) under varying wind shear. Within the radius of maximum wind (RMW), preceding RI in the low‐shear TC (hurricane Ike of 2008) increased updraught magnitudes for the top 1% of the distribution at 7 km occur, while in the high‐shear scenario (hurricane Earl of 2010) RI is led by increased updraught magnitudes of the top 1% of the distribution at 12 km. Three‐dimensional analyses of individual updraughts relative to their peak altitude enables direct quantification of processes associated with shallow cumuli, cumulus congestus, deep convection failing to penetrate the tropopause, and convective bursts (CBs). Mean profiles for each convective regime reveal positive contributions in certain variables of each updraught variety towards RI with positive diabatic heating, absolute vorticity, and moisture convergence roles.Within the RMW, CBs are shown to be the primary diabatic heating and vertical mass and vapour flux contributors in both simulations, while Ike includes secondary contributions from deep convection and congestus in addition to noteworthy diabatic heating from apparent stratiform processes that act to spin up the mid‐level vortex. Inner‐core moisture convergence has divided contributions from shallow cumuli, cumulus congestus, and CBs. CBs act to enhance potential vorticity to the greatest amount and over the deepest vertical layer at low levels. The simulation results overwhelmingly support the aggregate importance of vertically developed deep convection and its associated ice processes to the initiation and maintenance of RI.

Observational evidence for aerosol invigoration in shallow cumulus downstream of Mount Kilauea

AbstractKnowledge of how marine boundary layer (MBL) shallow cumulus clouds respond to changes in aerosol is central to understanding how MBL clouds modulate the climate system. Mount Kilauea on the island of Hawaii began erupting in 2008 injecting substantial SO2 into the marine boundary layer creating a unique natural laboratory. Examining data from approximately 600 passes of the A‐Train downstream of Mount Kilauea over a 3 year period and separating data into aerosol optical depth quartiles, we find an unambiguous increase in marine boundary cloud top height and an increase in surface wind speed as aerosol increases while the radar reflectivity does not change substantially. We conclude that increased aerosols may have caused invigoration of the MBL clouds. Additionally, we find that increases in sub 1 km cloud fraction combined with increasing aerosol explain the increased visible reflectance suggesting that evidence for the so‐called first aerosol indirect effect should be reexamined.

An objective classification of Saturn cloud features from Cassini ISS images

A k-means clustering algorithm is applied to Cassini Imaging Science Subsystem continuum and methane band images of Saturn's northern hemisphere to objectively classify regional albedo features and aid in their dynamical interpretation. The procedure is based on a technique applied previously to visible-infrared images of Earth. It provides a new perspective on giant planet cloud morphology and its relationship to the dynamics and a meteorological context for the analysis of other types of simultaneous Saturn observations. The method identifies 6 clusters that exhibit distinct morphology, vertical structure, and preferred latitudes of occurrence. These correspond to areas dominated by deep convective cells; low contrast areas, some including thinner and thicker clouds possibly associated with baroclinic instability; regions with possible isolated thin cirrus clouds; darker areas due to thinner low level clouds or clearer skies due to downwelling, or due to absorbing particles; and fields of relatively shallow cumulus clouds. The spatial associations among these cloud types suggest that dynamically, there are three distinct types of latitude bands on Saturn: deep convectively disturbed latitudes in cyclonic shear regions poleward of the eastward jets; convectively suppressed regions near and surrounding the westward jets; and baroclinically unstable latitudes near eastward jet cores and in the anti-cyclonic regions equatorward of them. These are roughly analogous to some of the features of Earth's tropics, subtropics, and midlatitudes, respectively. This classification may be more useful for dynamics purposes than the traditional belt-zone partitioning. Temporal variations of feature contrast and cluster occurrence suggest that the upper tropospheric haze in the northern hemisphere may have thickened by 2014. The results suggest that routine use of clustering may be a worthwhile complement to many different types of planetary atmospheric data analysis.

Improving Parameterization of Entrainment Rate for Shallow Convection with Aircraft Measurements and Large-Eddy Simulation

AbstractThis work examines the relationships of entrainment rate to vertical velocity, buoyancy, and turbulent dissipation rate by applying stepwise principal component regression to observational data from shallow cumulus clouds collected during the Routine Atmospheric Radiation Measurement (ARM) Aerial Facility (AAF) Clouds with Low Optical Water Depths (CLOWD) Optical Radiative Observations (RACORO) field campaign over the ARM Southern Great Plains (SGP) site near Lamont, Oklahoma. The cumulus clouds during the RACORO campaign simulated using a large-eddy simulation (LES) model are also examined with the same approach. The analysis shows that a combination of multiple variables can better represent entrainment rate in both the observations and LES than any single-variable fitting. Three commonly used parameterizations are also tested on the individual cloud scale. A new parameterization is thus presented that relates entrainment rate to vertical velocity, buoyancy, and dissipation rate; the effects of treating clouds as ensembles and humid shells surrounding cumulus clouds on the new parameterization are discussed. Physical mechanisms underlying the relationships of entrainment rate to vertical velocity, buoyancy, and dissipation rate are also explored.

How large-scale subsidence affects stratocumulus transitions

Abstract. Some climate modeling results suggest that the Hadley circulation might weaken in a future climate, causing a subsequent reduction in the large-scale subsidence velocity in the subtropics. In this study we analyze the cloud liquid water path (LWP) budget from large-eddy simulation (LES) results of three idealized stratocumulus transition cases, each with a different subsidence rate. As shown in previous studies a reduced subsidence is found to lead to a deeper stratocumulus-topped boundary layer, an enhanced cloud-top entrainment rate and a delay in the transition of stratocumulus clouds into shallow cumulus clouds during its equatorwards advection by the prevailing trade winds. The effect of a reduction of the subsidence rate can be summarized as follows. The initial deepening of the stratocumulus layer is partly counteracted by an enhanced absorption of solar radiation. After some hours the deepening of the boundary layer is accelerated by an enhancement of the entrainment rate. Because this is accompanied by a change in the cloud-base turbulent fluxes of moisture and heat, the net change in the LWP due to changes in the turbulent flux profiles is negligibly small.

Observational estimates of detrainment and entrainment in non-precipitating shallow cumulus

Abstract. Vertical transport associated with cumulus clouds is important to the redistribution of gases, particles, and energy, with subsequent consequences for many aspects of the climate system. Previous studies have suggested that detrainment from clouds can be comparable to the updraft mass flux, and thus represents an important contribution to vertical transport. In this study, we describe a new method to deduce the amounts of gross detrainment and entrainment experienced by non-precipitating cumulus clouds using aircraft observations. The method utilizes equations for three conserved variables: cloud mass, total water, and moist static energy. Optimizing these three equations leads to estimates of the mass fractions of adiabatic mixed-layer air, entrained air and detrained air that the sampled cloud has experienced. The method is applied to six flights of the CIRPAS Twin Otter during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) which took place in the Houston, Texas region during the summer of 2006 during which 176 small, non-precipitating cumuli were sampled. Using our novel method, we find that, on average, these clouds were comprised of 30 to 70 % mixed-layer air, with entrained air comprising most of the remainder. The mass fraction of detrained air was usually very small, less than 2 %, although values larger than 10 % were found in 15 % of clouds. Entrained and detrained air mass fractions both increased with altitude, consistent with some previous observational studies. The largest detrainment events were almost all associated with air that was at their level of neutral buoyancy, which has been hypothesized in previous modeling studies. This new method could be readily used with data from other previous aircraft campaigns to expand our understanding of detrainment for a variety of cloud systems.

Analysis of pressure‐strain and pressure gradient‐scalar covariances in cloud‐topped boundary layers: A large‐eddy simulation study

AbstractA detailed analysis of the pressure‐scrambling terms (i.e., the pressure‐strain and pressure gradient‐scalar covariances) in the Reynolds‐stress and scalar‐flux budgets for cloud‐topped boundary layers (CTBLs) is performed using high‐resolution large‐eddy simulation (LES). Two CTBLs are simulated — one with trade wind shallow cumuli, and the other with nocturnal marine stratocumuli. The pressure‐scrambling terms are decomposed into contributions due to turbulence‐turbulence interactions, mean velocity shear, buoyancy, and Coriolis effects. Commonly used models of these contributions, including a simple linear model most often used in geophysical applications and a more sophisticated two‐component‐limit (TCL) nonlinear model, are tested against the LES data. The decomposition of the pressure‐scrambling terms shows that the turbulence‐turbulence and buoyancy contributions are most significant for cloud‐topped boundary layers. The Coriolis contribution is negligible. The shear contribution is generally of minor importance inside the cloudy layers, but it is the leading‐order contribution near the surface. A comparison of models of the pressure‐scrambling terms with the LES data suggests that the more complex TCL model is superior to the simple linear model only for a few contributions. The linear model is able to reproduce the principal features of the pressure‐scrambling terms reasonably well. It can be applied in the second‐order turbulence modeling of cloud‐topped boundary layer flows, provided some uncertainties are tolerated.

A PDF-Based Formulation of Microphysical Variability in Cumulus Congestus Clouds*

Abstract Calculating unbiased microphysical process rates over mesoscale model grid volumes necessitates knowledge of the subgrid-scale (SGS) distribution of variables, typically represented as probability distribution functions (PDFs) of the prognostic variables. In the 2014 Journal of the Atmospheric Sciences paper by Kogan and Mechem, they employed large-eddy simulation of Rain in Cumulus over the Ocean (RICO) trade cumulus to develop PDFs and joint PDFs of cloud water, rainwater, and droplet concentration. In this paper, the approach of Kogan and Mechem is extended to deeper, precipitating cumulus congestus clouds as represented by a simulation based on conditions from the TOGA COARE field campaign. The fidelity of various PDF approximations was assessed by evaluating errors in estimating autoconversion and accretion rates. The dependence of the PDF shape on grid-mean variables is much stronger in congestus clouds than in shallow cumulus. The PDFs obtained from the TOGA COARE simulations for the calculation of accretion rates may be applied to both shallow and congestus cumulus clouds. However, applying the TOGA COARE PDFs to calculate autoconversion rates introduces unacceptably large errors in shallow cumulus clouds, thus precluding the use of a “universal” PDF formulation for both cloud types.

Cloud Regime Variability over the Azores and Its Application to Climate Model Evaluation

Abstract From its location on the subtropics–midlatitude boundary, the Azores is influenced by both the subtropical high pressure and the midlatitude baroclinic storm regimes and therefore experiences a wide range of cloud structures, from fair-weather scenes to stratocumulus sheets and deep convective systems. This work combines three types of datasets to study cloud variability in the Azores: a satellite analysis of cloud regimes, a reanalysis characterization of storminess, and a 19-month field campaign that occurred on Graciosa Island. Combined analysis of the three datasets provides a detailed picture of cloud variability and the respective dynamic influences, with emphasis on low clouds that constitute a major uncertainty source in climate model simulations. The satellite cloud regime analysis shows that the Azores cloud distribution is similar to the mean global distribution and can therefore be used to evaluate cloud simulation in global models. Regime analysis of low clouds shows that stratocumulus decks occur under the influence of the Azores high pressure system, while shallow cumulus clouds are sustained by cold-air outbreaks, as revealed by their preference for postfrontal environments and northwesterly flows. An evaluation of climate model cloud regimes from phase 5 of CMIP (CMIP5) over the Azores shows that all models severely underpredict shallow cumulus clouds, while most models also underpredict the occurrence of stratocumulus cloud decks. It is demonstrated that the regime analysis can assist in the selection of case studies representing specific climatological cloud distributions. With all the tools now in place, a methodology is suggested to better understand cloud–dynamics interactions and attempt to explain and correct climate model cloud deficiencies.

The tropical Atlantic surface wind divergence belt and its effect on clouds

Abstract. A well-defined surface wind divergence (SWD) belt with distinct cloud properties forms over the equatorial Atlantic during the boreal summer months. This belt separates the deep convective clouds of the Intertropical Convergence Zone (ITCZ) from the shallow marine stratocumulus cloud decks forming over the cold-water subtropical region of the southern branch of the Hadley cell in the Atlantic. Using the QuikSCAT-SeaWinds and Aqua-MODIS instruments, we examined the large-scale spatiotemporal variability in the SWD belt during a 6-year period (2003–2008) and the related links to cloud properties over the Atlantic Ocean. The Atlantic SWD belt was found to be most pronounced from May to August, between the Equator and 2° N latitude. A positive correlation and a strong link were observed between formation of the SWD belt and a sharp sea-surface temperature gradient on the northern border of the cold tongue, supporting Wallace's vertical-mixing mechanism. The dominant cloud type over this region was shallow cumulus. Cloud properties were shown to be strongly linked to the formation and strength of the SWD zone. The findings will help to understand the link between ocean–atmosphere dynamics and cloud properties over this region, and suggest that the SWD zone be considered a unique cloud belt of the southern branch of the Atlantic Hadley cell.

Exploring bin‐macrophysics models for moist convective transport and clouds

AbstractThis study explores a mass flux framework for moist convective transport and clouds that is formulated in terms of discretized size densities. The properties of each bin in these histograms are estimated individually, making use of a rising plume model. In this framework, the number density acts as a weight, appearing in the area fraction of the mass flux. Such “bin‐macrophysics” models have the benefit that bulk closures become redundant, and that scale‐awareness is introduced at the basis of the formulation. Large‐eddy simulation results are used to verify the design of this framework and to constrain associated constants of proportionality. The behavior of the framework is explored by means of single‐column model simulations of various idealized cases of shallow and deeper surface‐driven convection. A smoothly developing solution for a deepening marine shallow cumulus case is obtained, reproducing key aspects of transport and clouds that define this regime. Further investigation of the size statistics of the framework reveals that indirect interactions between size‐bins play a key role in the equilibration process. An “acceleration‐detrainment” layer is identified above cloud base in which the flux uptake by the largest plumes is counteracted by the detrainment by decelerating smaller plumes. This suppresses CIN, and thus acts to preserve the cloud‐subcloud coupling. The convective mass flux shows sensitivity to environmental humidity in the deeper convective cases, reproducing transitions from shallow‐to‐deep convection. Sensitivity tests are performed to assess the impact of various components of the framework.