Shallow cumulus convection: A validation of large-eddy simulation against aircraft and Landsat observations

2003 ◽  
Vol 129 (593) ◽  
pp. 2671-2696 ◽  
Author(s):  
R. A. J. Neggers ◽  
P. G. Duynkerke ◽  
S. M. A. Rodts
Keyword(s):  
Large Eddy Simulation ◽  
Cumulus Convection ◽  
Eddy Simulation ◽  
Shallow Cumulus ◽  
Large Eddy

scholarly journals A Large Eddy Simulation Intercomparison Study of Shallow Cumulus Convection

2003 ◽  
Vol 60 (10) ◽  
pp. 1201-1219 ◽  
Author(s):  
A. Pier Siebesma ◽  
Christopher S. Bretherton ◽  
Andrew Brown ◽  
Andreas Chlond ◽  
Joan Cuxart ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Cumulus Convection ◽  
Eddy Simulation ◽  
Shallow Cumulus ◽  
Large Eddy ◽  
Intercomparison Study

Large-eddy simulation of the diurnal cycle of shallow cumulus convection over land

2002 ◽  
Vol 128 (582) ◽  
pp. 1075-1093 ◽  
Author(s):  
A. R. Brown ◽  
R. T. Cederwall ◽  
A. Chlond ◽  
P.G. Duynkerke ◽  
J.-C. Golaz ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Diurnal Cycle ◽  
Cumulus Convection ◽  
Eddy Simulation ◽  
Shallow Cumulus ◽  
Large Eddy

scholarly journals A Dual Mass Flux Framework for Boundary Layer Convection. Part I: Transport

2009 ◽  
Vol 66 (6) ◽  
pp. 1465-1487 ◽  
Author(s):  
Roel A. J. Neggers ◽  
Martin Köhler ◽  
Anton C. M. Beljaars
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Mixed Layer ◽  
Mass Flux ◽  
Model Complexity ◽  
Cumulus Convection ◽  
Eddy Simulation ◽  
Shallow Cumulus ◽  
Large Eddy ◽  
Simulation Results

Abstract This study considers the question of what is the least complex bulk mass flux framework that can still conceptually reproduce the smoothly varying coupling between the shallow convective cloud layer and the subcloud mixed layer. To this end, the model complexity of the classic single bulk mass flux scheme is enhanced. Inspired by recent large-eddy simulation results, the authors argue that two relatively minor but key conceptual modifications are already sufficient to achieve this goal: (i) retaining a dry transporting updraft in the moist limit and (ii) applying continuous updraft area partitioning to this dual mass flux (DualM) framework. The dry updraft represents all internal mixed layer updrafts that terminate near the mixed layer top, whereas the moist updraft represents all updrafts that condense and rise out of the mixed layer as buoyant cumulus clouds. The continuous area partitioning between the dry and moist updraft is a function of moist convective inhibition above the mixed layer top. Updraft initialization is a function of the updraft area fraction and is therefore consistent with the updraft definition. It is argued that the model complexity thus enhanced is sufficient to allow reproduction of various phenomena involved in the cloud–subcloud coupling, namely (i) dry countergradient transport within the mixed layer that is independent of the moist updraft, (ii) soft triggering of moist convective flux throughout the boundary layer, and (iii) a smooth response to smoothly varying forcings, including the reproduction of gradual transitions to and from shallow cumulus convection. The DualM framework is evaluated by implementing in the Eddy Diffusivity Mass Flux (EDMF) boundary layer scheme of the ECMWF’s Integrated Forecasting System. Single column model experiments are evaluated against large-eddy simulation results for a range of different cases that span a broad parameter space of cloud–subcloud coupling intensities. The results illustrate that also in numerical practice the DualM framework can reproduce gradual transitions to and from shallow cumulus convection. Model behavior is further explored through experiments in which model complexity is purposely reduced, thus mimicking a single bulk updraft setup. This gives more insight into the new model-internal interactions and explains the obtained case results.

scholarly journals Explicit aerosol–cloud interactions in the Dutch Atmospheric Large-Eddy Simulation model DALES4.1-M7

2019 ◽  
Vol 12 (12) ◽  
pp. 5177-5196 ◽  
Author(s):  
Marco de Bruine ◽  
Maarten Krol ◽  
Jordi Vilà-Guerau de Arellano ◽  
Thomas Röckmann
Keyword(s):  
Large Eddy Simulation ◽  
Simulation Model ◽  
Large Eddy Simulation Model ◽  
Aerosol Cloud ◽  
Eddy Simulation ◽  
Aerosol Mass ◽  
Shallow Cumulus ◽  
Large Eddy ◽  
Microphysical Processes ◽  
Aerosol Cloud Interactions

Abstract. Large-eddy simulation (LES) models are an excellent tool to improve our understanding of aerosol–cloud interactions (ACI). We introduce a prognostic aerosol scheme with multiple aerosol species in the Dutch Atmospheric Large-Eddy Simulation model (DALES), especially focused on simulating the impact of cloud microphysical processes on the aerosol population. The numerical treatment of aerosol activation is a crucial element for simulating both cloud and aerosol characteristics. Two methods are implemented and discussed: an explicit activation scheme based on κ-Köhler theory and a more classic approach using updraught strength. Sample model simulations are based on the Rain in Shallow Cumulus over the Ocean (RICO) campaign, characterized by rapidly precipitating warm-phase shallow cumulus clouds. We find that in this pristine ocean environment virtually all aerosol mass in cloud droplets is the result of the activation process, while in-cloud scavenging is relatively inefficient. Despite the rapid formation of precipitation, most of the in-cloud aerosol mass is returned to the atmosphere by cloud evaporation. The strength of aerosol processing through subsequent cloud cycles is found to be particularly sensitive to the activation scheme and resulting cloud characteristics. However, the precipitation processes are considerably less sensitive. Scavenging by precipitation is the dominant source for in-rain aerosol mass. About half of the in-rain aerosol reaches the surface, while the rest is released by evaporation of falling precipitation. The effect of cloud microphysics on the average aerosol size depends on the balance between the evaporation of clouds and rain and ultimate removal by precipitation. Analysis of typical aerosol size associated with the different microphysical processes shows that aerosols resuspended by cloud evaporation have a radius that is only 5 % to 10 % larger than the originally activated aerosols. In contrast, aerosols released by evaporating precipitation are an order of magnitude larger.

Sign in / Sign up

Export Citation Format

Share Document