Mixed-phase clouds in a turbulent environment. Part 1: Large-eddy simulation experiments

2013 ◽  
Vol 140 (680) ◽  
pp. 855-869 ◽  
Author(s):  
A. A. Hill ◽  
P. R. Field ◽  
K. Furtado ◽  
A. Korolev ◽  
B. J. Shipway
Keyword(s):  
Large Eddy Simulation ◽  
Mixed Phase ◽  
Simulation Experiments ◽  
Turbulent Environment ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Mixed Phase Clouds

scholarly journals The Effect of Ice Nuclei Efficiency on Arctic Mixed-Phase Clouds from Large-Eddy Simulations

2017 ◽  
Vol 74 (12) ◽  
pp. 3901-3913 ◽  
Author(s):  
Shizuo Fu ◽  
Huiwen Xue
Keyword(s):  
Simulation Analysis ◽  
Mixed Phase ◽  
Ice Formation ◽  
Microphysics Scheme ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Ice Nuclei ◽  
Large Eddy ◽  
Bin Microphysics ◽  
Mixed Phase Clouds

Abstract The effects of ice nuclei (IN) efficiency on the persistent ice formation in Arctic mixed-phase clouds (AMCs) are investigated using a large-eddy simulation model, coupled to a bin microphysics scheme with a prognostic IN formulation. In the three cases where the IN efficiency is high, ice formation and IN depletion are fast. When the IN concentration is 1 and 10 g−1, IN are completely depleted and the cloud becomes purely liquid phase before the end of the 24-h simulation. When the IN concentration is 100 g−1, the IN supply is sufficient but the liquid water is completely consumed so that the cloud dissipates quickly. In the three cases when the IN efficiency is low, ice formation is negligible in the first several hours but becomes significant as the temperature is decreased through longwave cooling. Before the end of the simulation, the cloud is in mixed phase when the IN concentration is 1 and 10 g−1 but dissipates when the IN concentration is 100 g−1. In the case where two types of IN are considered, ice formation persists throughout the simulation. Analysis shows that as the more efficient IN are continuously removed through ice formation, the less efficient IN gradually nucleate more ice crystals because the longwave cooling decreases the cloud temperature. This mechanism is further illustrated with a simple model. These results indicate that a spectrum of IN efficiency is necessary to maintain the persistent ice formation in AMCs.

scholarly journals Midlatitude mixed-phase stratocumulus clouds and their interactions with aerosols: how ice processes affect microphysical, dynamic, and thermodynamic development in those clouds and interactions?

2021 ◽  
Vol 21 (22) ◽  
pp. 16843-16868
Author(s):  
Seoung Soo Lee ◽  
Kyung-Ja Ha ◽  
Manguttathil Gopalakrishnan Manoj ◽  
Mohammad Kamruzzaman ◽  
Hyungjun Kim ◽  
...  
Keyword(s):  
Water Vapor ◽  
Cloud Condensation Nuclei ◽  
Mixed Phase ◽  
Spatiotemporal Variability ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Stratocumulus Clouds ◽  
Evaporation Of Droplets ◽  
Cloud Ice ◽  
Mixed Phase Clouds

Abstract. Midlatitude mixed-phase stratocumulus clouds and their interactions with aerosols remain poorly understood. This study examines the roles of ice processes in those clouds and their interactions with aerosols using a large-eddy simulation (LES) framework. Cloud mass becomes much lower in the presence of ice processes and the Wegener–Bergeron–Findeisen (WBF) mechanism in the mixed-phase clouds compared to that in warm clouds. This is because while the WBF mechanism enhances the evaporation of droplets, the low concentration of aerosols acting as ice-nucleating particles (INPs) and cloud ice number concentration (CINC) prevent the efficient deposition of water vapor. Note that the INP concentration in this study is based on the observed spatiotemporal variability of aerosols. This results in the lower CINC compared to that with empirical dependence of the INP concentrations on temperature in a previous study. In the mixed-phase clouds, the increasing concentration of aerosols that act as cloud condensation nuclei (CCN) decreases cloud mass by increasing the evaporation of droplets through the WBF mechanism and decreasing the intensity of updrafts. In contrast to this, in the warm clouds, the absence of the WBF mechanism makes the increase in the evaporation of droplets inefficient, eventually enabling cloud mass to increase with the increasing concentration of aerosols acting as CCN. Here, the results show that when there is an increasing concentration of aerosols that act as INPs, the deposition of water vapor is more efficient than when there is the increasing concentration of aerosols acting as CCN, which in turn enables cloud mass to increase in the mixed-phase clouds.

scholarly journals Mid-latitude mixed-phase stratocumulus clouds and their interactions with aerosols: how ice processes affect microphysical, dynamic and thermodynamic development in those clouds and interactions?

2021 ◽  
Author(s):  
Seoung Soo Lee ◽  
Kyung-Ja Ha ◽  
Manguttathil Gopalakrishnan Manoj ◽  
Mohammad Kamruzzaman ◽  
Hyungjun Kim ◽  
...  
Keyword(s):  
Water Vapor ◽  
Cloud Condensation Nuclei ◽  
Mixed Phase ◽  
Eddy Simulation ◽  
Ice Nuclei ◽  
Large Eddy ◽  
Stratocumulus Clouds ◽  
Evaporation Of Droplets ◽  
Cloud Ice ◽  
Mixed Phase Clouds

Abstract. Mid-latitude mixed-phase stratocumulus clouds and their interactions with aerosols remain poorly understood. This study examines the roles of ice processes in those clouds and interactions using a large-eddy simulation (LES) framework. Cloud mass becomes much lower in the presence of ice processes and the Wegener-Bergeron-Findeisen (WBF) mechanism in the mixed-phase clouds as compared to that in warm clouds. This is because while the WBF mechanism enhances the evaporation of droplets, the low concentration of aerosols as ice nuclei (IN) and cloud ice number concentration (CINC) prevent the efficient deposition of water vapor whose mass is contributed by the evaporation. In the mixed-phase clouds, the increasing concentration of aerosols that act as cloud condensation nuclei (CCN) decreases cloud mass by increasing the evaporation of droplets through the WBF mechanism and decreasing the intensity of updrafts. In contrast to this, in the warm clouds, the absence of the WBF mechanism makes the increase in the evaporation of droplets inefficient, eventually enabling cloud mass to increase with the increasing concentration of aerosols as CCN. Here, the results show that when there is an increasing concentration of aerosols that act as IN, the deposition of water vapor is more efficient than when there is the increasing concentration of aerosols as CCN, which in turn enables cloud mass to increase in the mixed-phase clouds.

scholarly journals Cloud-Top Entrainment in Mixed-Phase Stratocumulus and Its Process-Level Representation in Large-Eddy Simulation

2020 ◽  
Vol 77 (12) ◽  
pp. 4109-4127
Author(s):  
Robert Rauterkus ◽  
Cedrick Ansorge
Keyword(s):  
Large Eddy Simulation ◽  
Horizontal Resolution ◽  
Mixed Phase ◽  
Small Scale ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Arctic Ice ◽  
First Time ◽  
Horizontal Grid ◽  
Process Level

AbstractCloud-top entrainment is a crucial process for the evolution of stratocumulus and is driven by interactions of radiation, microphysics, and turbulence on scales reaching down to less than one meter. Regardless of this fact, most large-eddy simulation studies still apply a horizontal resolution of tens of meters, not resolving these interactions sufficiently. Here, based on an extensive observational campaign, we define a weak-shear benchmark scenario for large-eddy simulation over Arctic ice and for the first time perform large-eddy simulation of mixed-phase stratocumulus with horizontal resolutions of 35, 10, and 3.5 m. Thereby, we investigate the processes contributing to cloud-top entrainment and their role for the evolution of stratocumulus with a particular focus on resolution sensitivity. First, we find that a horizontal grid spacing larger than 10 m insufficiently represents the effects of small-scale microphysical cooling and turbulent engulfment on cloud-top entrainment. Indeed, the small size of energy-containing eddies—a consequence of the intense stratification in the vicinity of the cloud-top region—violates the underlying assumptions of subgridscale models by buoyant suppression of eddies at the large-eddy simulation filter scale. Second, the decrease in cloud-top entrainment due to these insufficiently represented processes results in 15% less cloud water after 6 h of simulation and a corresponding optical thinning of the cloud. Third, we show that the applied nonequilibrium microphysics cause microphysical heating beneath the cloud top, which partly counteracts the evaporative cooling.

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