scholarly journals The importance of Aitken mode aerosol particles for cloud sustenance in the summertime high Arctic – a simulation study supported by observational data

2021 ◽  
Vol 21 (5) ◽  
pp. 3871-3897
Author(s):  
Ines Bulatovic ◽  
Adele L. Igel ◽  
Caroline Leck ◽  
Jost Heintzenberg ◽  
Ilona Riipinen ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Simulation Models ◽  
Liquid Water Content ◽  
High Arctic ◽  
Radiative Properties ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Mixed Phase Clouds ◽  
Aitken Mode ◽  
Ice Fraction

Abstract. The potential importance of Aitken mode particles (diameters ∼ 25–80 nm) for stratiform mixed-phase clouds in the summertime high Arctic (>80∘ N) has been investigated using two large-eddy simulation models. We find that, in both models, Aitken mode particles significantly affect the simulated microphysical and radiative properties of the cloud and can help sustain the cloud when accumulation mode concentrations are low (< 10–20 cm−3), even when the particles have low hygroscopicity (hygroscopicity parameter – κ=0.1). However, the influence of the Aitken mode decreases if the overall liquid water content of the cloud is low, either due to a higher ice fraction or due to low radiative cooling rates. An analysis of the simulated supersaturation (ss) statistics shows that the ss frequently reaches 0.5 % and sometimes even exceeds 1 %, which confirms that Aitken mode particles can be activated. The modelling results are in qualitative agreement with observations of the Hoppel minimum obtained from four different expeditions in the high Arctic. Our findings highlight the importance of better understanding Aitken mode particle formation, chemical properties and emissions, particularly in clean environments such as the high Arctic.

scholarly journals The importance of Aitken mode aerosol particles for cloud sustenance in the summertime high Arctic: A simulation study supported by observational data

2020 ◽  
Author(s):  
Ines Bulatovic ◽  
Adele L. Igel ◽  
Caroline Leck ◽  
Jost Heintzenberg ◽  
Ilona Riipinen ◽  
...  
Keyword(s):  
Simulation Study ◽  
Aerosol Particles ◽  
Simulation Models ◽  
High Arctic ◽  
Potential Importance ◽  
Eddy Simulation ◽  
Cloud Properties ◽  
Large Eddy ◽  
Mixed Phase Clouds ◽  
Aitken Mode

Abstract. The potential importance of Aitken mode particles (diameters ~ 25–80 nm) for stratiform mixed-phase clouds in the summertime high Arctic has been investigated using two large-eddy simulation models. We find that in both models Aitken mode particles significantly affect the simulated cloud properties and can help sustain the cloud when accumulation mode concentrations are low (

scholarly journals Supersaturation calculation in large eddy simulation models for prediction of the droplet number concentration

2012 ◽  
Vol 5 (3) ◽  
pp. 761-772 ◽  
Author(s):  
O. Thouron ◽  
J.-L. Brenguier ◽  
F. Burnet
Keyword(s):  
Cloud Condensation Nuclei ◽  
Simulation Models ◽  
Number Concentration ◽  
Eddy Simulation ◽  
Droplet Concentration ◽  
Large Eddy ◽  
Condensed Water ◽  
Les Model ◽  
Adjustment Scheme ◽  
Cloud Core

Abstract. A new parameterization scheme is described for calculation of supersaturation in LES models that specifically aims at the simulation of cloud condensation nuclei (CCN) activation and prediction of the droplet number concentration. The scheme is tested against current parameterizations in the framework of the Meso-NH LES model. It is shown that the saturation adjustment scheme, based on parameterizations of CCN activation in a convective updraft, overestimates the droplet concentration in the cloud core, while it cannot simulate cloud top supersaturation production due to mixing between cloudy and clear air. A supersaturation diagnostic scheme mitigates these artefacts by accounting for the presence of already condensed water in the cloud core, but it is too sensitive to supersaturation fluctuations at cloud top and produces spurious CCN activation during cloud top mixing. The proposed pseudo-prognostic scheme shows performance similar to the diagnostic one in the cloud core but significantly mitigates CCN activation at cloud top.

scholarly journals Assessment of Grid Anisotropy Effects on Large-Eddy-Simulation Models with Different Length Scales

AIAA Journal ◽  
2020 ◽  
Vol 58 (10) ◽  
pp. 4522-4533
Author(s):  
Jan-Erik Schumann ◽  
Siavash Toosi ◽  
Johan Larsson
Keyword(s):  
Large Eddy Simulation ◽  
Simulation Models ◽  
Length Scales ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Grid Anisotropy

Evaluation of the WRF PBL Parameterizations for Marine Boundary Layer Clouds: Cumulus and Stratocumulus

2013 ◽  
Vol 141 (7) ◽  
pp. 2265-2271 ◽  
Author(s):  
Hsin-Yuan Huang ◽  
Alex Hall ◽  
Joao Teixeira
Keyword(s):  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Marine Boundary Layer ◽  
Layer Structure ◽  
Model Performance ◽  
Simulation Models ◽  
Eddy Diffusivity ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Boundary Layer Cloud

Abstract The performance of five boundary layer parameterizations in the Weather Research and Forecasting Model is examined for marine boundary layer cloud regions running in single-column mode. Most parameterizations show a poor agreement of the vertical boundary layer structure when compared with large-eddy simulation models. These comparisons against large-eddy simulation show that a parameterization based on the eddy-diffusivity/mass-flux approach provides a better performance. The results also illustrate the key role of boundary layer parameterizations in model performance.

scholarly journals DNS and LES of the Compressible Flow Over a Delta Wing With the Symmetry-Preserving Discretization

2014 ◽  
Author(s):  
Wybe Rozema ◽  
Johan C. Kok ◽  
Roel W. C. P. Verstappen ◽  
Arthur E. P. Veldman
Keyword(s):  
Compressible Flow ◽  
Delta Wing ◽  
Region Of Interest ◽  
Simulation Models ◽  
Simulation Method ◽  
Discrete Level ◽  
Artificial Dissipation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Stability

A fourth-order accurate symmetry-preserving discretization for compressible flow is used to perform simulations of the turbulent flow over a delta wing. A symmetry-preserving discretization eliminates the non-linear convective instability by preserving conservation of kinetic energy at the discrete level. This enhances the stability of a simulation method, so that little artificial dissipation is needed for numerical stability. It is shown that simulations of the flow over a sharp-edge delta wing at Re = 50,000 with the symmetry-preserving discretization are stable without artificial dissipation in a region of interest around the delta wing. To assess the accuracy of the simulation method, results obtained on a fine computational grid are compared with results obtained on a coarser grid. Also results obtained with large-eddy simulation models and with sixth-order artificial dissipation are presented.

scholarly journals The Explicit Wake Parametrisation V1.0: a wind farm parametrisation in the mesoscale model WRF

2015 ◽  
Vol 8 (4) ◽  
pp. 3481-3522 ◽  
Author(s):  
P. J. H. Volker ◽  
J. Badger ◽  
A. N. Hahmann ◽  
S. Ott
Keyword(s):  
Large Scale ◽  
Wind Farm ◽  
Mesoscale Model ◽  
Wind Farms ◽  
Simulation Models ◽  
Offshore Wind ◽  
Offshore Wind Farms ◽  
Eddy Simulation ◽  
Large Eddy

Abstract. We describe the theoretical basis, implementation and validation of a new parametrisation that accounts for the effect of large offshore wind farms on the atmosphere and can be used in mesoscale and large-scale atmospheric models. This new parametrisation, referred to as the Explicit Wake Parametrisation (EWP), uses classical wake theory to describe the unresolved wake expansion. The EWP scheme is validated against filtered in situ measurements from two meteorological masts situated a few kilometres away from the Danish offshore wind farm Horns Rev I. The simulated velocity deficit in the wake of the wind farm compares well to that observed in the measurements and the velocity profile is qualitatively similar to that simulated with large eddy simulation models and from wind tunnel studies. At the same time, the validation process highlights the challenges in verifying such models with real observations.

scholarly journals On the application of the classic Kessler and Berry schemes in Large Eddy Simulation models with a particular emphasis on cloud autoconversion, the onset time of precipitation and droplet evaporation

1998 ◽  
Vol 16 (5) ◽  
pp. 628-637 ◽  
Author(s):  
S. Ghosh ◽  
P. R. Jonas
Keyword(s):  
Large Eddy Simulation ◽  
Onset Time ◽  
Simulation Models ◽  
Droplet Evaporation ◽  
Atmospheric Composition ◽  
Accurate Estimation ◽  
Eddy Simulation ◽  
Deep Model ◽  
Composition And Structure ◽  
Large Eddy

Abstract. Many Large Eddy Simulation (LES) models use the classic Kessler parameterisation either as it is or in a modified form to model the process of cloud water autoconversion into precipitation. The Kessler scheme, being linear, is particularly useful and is computationally straightforward to implement. However, a major limitation with this scheme lies in its inability to predict different autoconversion rates for maritime and continental clouds. In contrast, the Berry formulation overcomes this difficulty, although it is cubic. Due to their different forms, it is difficult to match the two solutions to each other. In this paper we single out the processes of cloud conversion and accretion operating in a deep model cloud and neglect the advection terms for simplicity. This facilitates exact analytical integration and we are able to derive new expressions for the time of onset of precipitation using both the Kessler and Berry formulations. We then discuss the conditions when the two schemes are equivalent. Finally, we also critically examine the process of droplet evaporation within the framework of the classic Kessler scheme. We improve the existing parameterisation with an accurate estimation of the diffusional mass transport of water vapour. We then demonstrate the overall robustness of our calculations by comparing our results with the experimental observations of Beard and Pruppacher, and find excellent agreement.Key words. Atmospheric composition and structure · Cloud physics and chemistry · Pollution · Meteorology and atmospheric dynamics · Precipitation

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
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