scholarly journals 3-D model simulations of dynamical and microphysical interactions in pyroconvective clouds under idealized conditions

2014 ◽  
Vol 14 (14) ◽  
pp. 7573-7583 ◽  
Author(s):  
P. Reutter ◽  
J. Trentmann ◽  
A. Seifert ◽  
P. Neis ◽  
H. Su ◽  
...  
Keyword(s):  
High Resolution ◽  
Cloud Condensation Nuclei ◽  
Three Dimensional ◽  
Atmospheric Model ◽  
Cloud Microphysics ◽  
Aerosol Concentration ◽  
Cloud Droplets ◽  
Cloud Development ◽  
Microphysical Processes ◽  
D Model

Abstract. Dynamical and microphysical processes in pyroconvective clouds in mid-latitude conditions are investigated using idealized three-dimensional simulations with the Active Tracer High resolution Atmospheric Model (ATHAM). A state-of-the-art two-moment microphysical scheme building upon a realistic parameterization of cloud condensation nuclei (CCN) activation has been implemented in order to study the influence of aerosol concentration on cloud development. The results show that aerosol concentration influences the formation of precipitation. For low aerosol concentrations (NCN = 200 cm−3), rain droplets are rapidly formed by autoconversion of cloud droplets. This also triggers the formation of large graupel and hail particles, resulting in an early onset of precipitation. With increasing aerosol concentration (NCN = 1000 cm−3 and NCN = 20 000 cm−3) the formation of rain droplets is delayed due to more but smaller cloud droplets. Therefore, the formation of ice crystals and snowflakes becomes more important for the eventual formation of graupel and hail, which is delayed at higher aerosol concentrations. This results in a delay of the onset of precipitation and a reduction of its intensity with increasing aerosol concentration. This study is the first detailed investigation of the interaction between cloud microphysics and the dynamics of a pyroconvective cloud using the combination of a high-resolution atmospheric model and a detailed microphysical scheme.

scholarly journals 3-D model simulations of dynamical and microphysical interactions in pyro-convective clouds under idealized conditions

2013 ◽  
Vol 13 (7) ◽  
pp. 19527-19557 ◽  
Author(s):  
P. Reutter ◽  
J. Trentmann ◽  
A. Seifert ◽  
P. Neis ◽  
H. Su ◽  
...  
Keyword(s):  
Forest Fires ◽  
Aerosol Particles ◽  
Three Dimensional ◽  
Convective Cloud ◽  
Atmospheric Model ◽  
Cloud Microphysics ◽  
Aerosol Concentration ◽  
Activation Process ◽  
Cloud Droplets ◽  
Convective Clouds

Abstract. Pyro-convective clouds, i.e. convective clouds forming over wildland fires due to high sensible heat, play an important role for the transport of aerosol particles and trace gases into the upper troposphere and lower stratosphere. Additionally, due to the emission of a large number of aerosol particles from forest fires, the microphysical structure of a pyro-convective cloud is clearly different from that of ordinary convective clouds. A crucial step in the microphysical evolution of a (pyro-) convective cloud is the activation of aerosol particles to form cloud droplets. The activation process affects the initial number and size of cloud droplets and can thus influence the evolution of the convective cloud and the formation of precipitation. Building upon a realistic parameterization of CCN activation, the model ATHAM is used to investigate the dynamical and microphysical processes of idealized three-dimensional pyro-convective clouds in mid-latitudes. A state-of-the-art two-moment microphysical scheme has been implemented in order to study the influence of the aerosol concentration on the cloud development. The results show that the aerosol concentration influences the formation of precipitation. For low aerosol concentrations (NCN=1000 cm−3), rain droplets are rapidly formed by autoconversion of cloud droplets. This also triggers the formation of large graupel and hail particles resulting in an early and strong onset of precipitation. With increasing aerosol concentration (NCN=20 000 cm−3 and NCN=60 000 cm−3) the formation of rain droplets is delayed due to more but smaller cloud droplets. Therefore, the formation of ice crystals and snowflakes becomes more important for the eventual formation of graupel and hail. However, this causes a delay of the onset of precipitation and its intensity for increasing aerosol concentration. This work shows the first detailed investigation of the interaction between cloud microphysics and dynamics of a pyro-convective cloud using the combination of a high resolution atmospheric model and a detailed microphysical scheme.

Lagrangian stochastic microphysics at unresolved scales in turbulent cloud simulations

2020 ◽  
Author(s):  
Gustavo Abade ◽  
Marta Waclawczyk ◽  
Wojciech W. Grabowski ◽  
Hanna Pawlowska
Keyword(s):  
Droplet Size ◽  
Cloud Condensation Nuclei ◽  
Droplet Size Distribution ◽  
Cloud Microphysics ◽  
Cloud Droplets ◽  
Adiabatic Cooling ◽  
Subgrid Scales ◽  
The Mean ◽  
Microphysical Processes ◽  
Droplet Size Distributions

<p>Turbulent clouds are challenging to model and simulate due to uncertainties in microphysical processes occurring at unresolved subgrid scales (SGS). These processes include the transport of cloud particles, supersaturation fluctuations, turbulent mixing, and the resulting stochastic droplet activation and growth by condensation. In this work, we apply two different Lagrangian stochastic schemes to model SGS cloud microphysics. Collision and coalescence of droplets are not considered. Cloud droplets and unactivated cloud condensation nuclei (CCN) are described by Lagrangian particles (superdroplets). The first microphysical scheme directly models the supersaturation fluctuations experienced by each Lagrangian superdroplet as it moves with the air flow. Supersaturation fluctuations are driven by turbulent fluctuations of the droplet vertical velocity through the adiabatic cooling/warming effect. The second, more elaborate scheme uses both temperature and vapor mixing ratio as stochastic attributes attached to each superdroplet. It is based on the probability density function formalism that provides a consistent Eulerian-Lagrangian formulation of scalar transport in a turbulent flow. Both stochastic microphysical schemes are tested in a synthetic turbulent-like cloud flow that mimics a stratocumulus topped boundary layer. It is shown that SGS turbulence plays a key role in broadening the droplet-size distribution towards larger sizes. Also, the feedback on water vapor of stochastically activated droplets buffers the variations of the mean supersaturation driven the resolved transport. This extends the distance over which entrained CNN are activated inside the cloud layer and produces multimodal droplet-size distributions.</p>

scholarly journals The evolution of cloud microphysics upon aerosol interaction at the summit of Mt. Tai, China

2019 ◽  
Author(s):  
Jiarong Li ◽  
Chao Zhu ◽  
Hui Chen ◽  
Defeng Zhao ◽  
Likun Xue ◽  
...  
Keyword(s):  
Climate Models ◽  
Cloud Condensation Nuclei ◽  
Liquid Water Content ◽  
Cloud Microphysics ◽  
Life Cycles ◽  
Cloud Droplets ◽  
Climate Effect ◽  
Local Climate ◽  
The North ◽  
Microphysical Properties

Abstract. The influence of aerosols, both natural and anthropogenic, remains a major area of uncertainty when predicting the properties and behaviour of clouds and their influence on climate. In an attempt to understand better the microphysical properties of cloud droplets, the aerosol-cloud interactions, and the corresponding climate effect during cloud life cycles in the North China Plain, an intensive observation took place from 17 June to 30 July 2018 at the summit of Mt. Tai. Cloud microphysical parameters were monitored simultaneously with number concentrations of cloud condensation nuclei (NCCN) at different supersaturations, PM2.5 mass concentrations, particle size distributions and meteorological parameters. Number concentrations of cloud droplets (NC), liquid water content (LWC) and effective radius of cloud droplets (reff) show large variations among 40 cloud events observed during the campaign. Perturbations of aerosols will significantly increase the NC of cloud droplets and shift cloud droplets toward smaller size ranges. Clouds in clean days are more susceptible to the change in concentrations of particle number (NP). LWC shows positive correlation with reff. As NC increases, reff changes from a trimodal distribution to a unimodal distribution. By assuming a cloud thickness of 100 m, we find that the albedo can increase 36.4 % if the cloud gets to be disturbed by aerosols. This may induce a cooling effect on the local climate system. Our results contribute more information about regional cloud microphysics and will help to reduce the uncertainties in climate models when predicting climate responses to cloud-aerosol interactions.

scholarly journals The Cloud-resolving model Radar SIMulator (CR-SIM) Version 3.3: description and applications of a virtual observatory

2020 ◽  
Vol 13 (4) ◽  
pp. 1975-1998 ◽  
Author(s):  
Mariko Oue ◽  
Aleksandra Tatarevic ◽  
Pavlos Kollias ◽  
Dié Wang ◽  
Kwangmin Yu ◽  
...  
Keyword(s):  
High Resolution ◽  
Climate Models ◽  
Model Simulation ◽  
Atmospheric Model ◽  
Cloud Microphysics ◽  
Virtual Observatory ◽  
Design Strategies ◽  
Modeling Framework ◽  
Cloud Resolving Model ◽  
Radar Simulator

Abstract. Ground-based observatories use multisensor observations to characterize cloud and precipitation properties. One of the challenges is how to design strategies to best use these observations to understand these properties and evaluate weather and climate models. This paper introduces the Cloud-resolving model Radar SIMulator (CR-SIM), which uses output from high-resolution cloud-resolving models (CRMs) to emulate multiwavelength, zenith-pointing, and scanning radar observables and multisensor (radar and lidar) products. CR-SIM allows for direct comparison between an atmospheric model simulation and remote-sensing products using a forward-modeling framework consistent with the microphysical assumptions used in the atmospheric model. CR-SIM has the flexibility to easily incorporate additional microphysical modules, such as microphysical schemes and scattering calculations, and expand the applications to simulate multisensor retrieval products. In this paper, we present several applications of CR-SIM for evaluating the representativeness of cloud microphysics and dynamics in a CRM, quantifying uncertainties in radar–lidar integrated cloud products and multi-Doppler wind retrievals, and optimizing radar sampling strategy using observing system simulation experiments. These applications demonstrate CR-SIM as a virtual observatory operator on high-resolution model output for a consistent comparison between model results and observations to aid interpretation of the differences and improve understanding of the representativeness errors due to the sampling limitations of the ground-based measurements. CR-SIM is licensed under the GNU GPL package and both the software and the user guide are publicly available to the scientific community.

scholarly journals LIMA (v1.0): a two-moment microphysical scheme driven by a multimodal population of cloud condensation and ice freezing nuclei

2015 ◽  
Vol 8 (9) ◽  
pp. 7767-7820 ◽  
Author(s):  
B. Vié ◽  
J.-P. Pinty ◽  
S. Berthet ◽  
M. Leriche
Keyword(s):  
Mesoscale Model ◽  
Cloud Condensation Nuclei ◽  
Three Dimensional ◽  
Single Equation ◽  
Ice Crystals ◽  
Growth Mode ◽  
Squall Line ◽  
Complex Nature ◽  
Cloud Droplets ◽  
Ice Clouds

Abstract. The paper describes the 2-moment microphysical scheme LIMA (Liquid Ice Multiple Aerosols), which relies on the prognostic evolution of a three-dimensional (3-D) aerosol population, and the careful description of the nucleating properties that enable cloud droplets and pristine ice crystals to form. LIMA uses the aerosol nucleating properties to form cloud droplets and pristine ice crystals. Several modes of Cloud Condensation Nuclei (CCN) and Ice Freezing Nuclei (IFN) are considered individually. A special class of partially soluble IFN is also introduced. These "aged" IFN act first as CCN and then as IFN by immersion nucleation at low temperatures. All the CCN modes are in competition with each other, as expressed by the single equation of maximum supersaturation. The IFN are insoluble aerosols that nucleate ice in several ways (condensation, deposition and immersion freezing) assuming the singular hypothesis. The scheme also includes the homogeneous freezing of cloud droplets, the Hallett–Mossop ice multiplication process and the freezing of haze at very low temperature. LIMA assumes that water vapour is in thermodynamic equilibrium with the population of cloud droplets (adjustment to saturation in warm clouds). In ice clouds, the prediction of the number concentration of the pristine ice crystals is used to compute explicit deposition and sublimation rates (leading to free under/supersaturation over ice). The formation of hydrometeors is standard. The autoconversion, accretion and self-collection processes shape the raindrop spectra. The initiation of the large crystals and aggregates category is the result of the depositional growth of large crystals beyond a critical size. Aggregation and riming are computed explicitly. Heavily rimed crystals (graupel) can experience a dry or wet growth mode. An advanced version of the scheme includes a separate hail category of particles forming and growing exclusively in the wet growth mode. The sedimentation of all particle types is included. The LIMA scheme is inserted in the cloud-resolving mesoscale model Meso-NH. The flexibility of LIMA is illustrated by two 2-D experiments. The first one highlights the sensitivity of orographic ice clouds to IFN types and IFN concentrations. Then a squall line case discusses the microstructure of a mixed-phase cloud and the impacts of pure CCN and IFN polluting plumes. The experiments show that LIMA captures the complex nature of aerosol-cloud interactions leading to different pathways for cloud and precipitation formation.

scholarly journals The effects of mineral dust particles, aerosol regeneration and ice nucleation parameterizations on clouds and precipitation

2012 ◽  
Vol 12 (19) ◽  
pp. 9303-9320 ◽  
Author(s):  
A. Teller ◽  
L. Xue ◽  
Z. Levin
Keyword(s):  
Mineral Dust ◽  
Cloud Microphysics ◽  
Ice Nucleation ◽  
Aerosol Concentration ◽  
Ice Crystals ◽  
Dust Particles ◽  
Cloud Base ◽  
Minor Effect ◽  
Total Precipitation ◽  
Cloud Droplets

Abstract. This study focuses on the effects of aerosol particles on the formation of convective clouds and precipitation in the Eastern Mediterranean Sea, with a special emphasis on the role of mineral dust particles in these processes. We used a new detailed numerical cloud microphysics scheme that has been implemented in the Weather Research and Forecast (WRF) model in order to study aerosol–cloud interaction in 3-D configuration based on 1° × 1° resolution reanalysis meteorological data. Using a number of sensitivity studies, we tested the contribution of mineral dust particles and different ice nucleation parameterizations to precipitation development. In this study we also investigated the importance of recycled (regenerated) aerosols that had been released to the atmosphere following the evaporation of cloud droplets. The results showed that increased aerosol concentration due to the presence of mineral dust enhanced the formation of ice crystals. The dynamic evolution of the cloud system sets the time periods and regions in which heavy or light precipitation occurred in the domain. The precipitation rate, the time and duration of precipitation were affected by the aerosol properties only at small spatial scales (with areas of about 20 km2). Changes of the ice nucleation scheme from ice supersaturation-dependent parameterization to a recent approach of aerosol concentration and temperature-dependent parameterization modified the ice crystals concentrations but did not affect the total precipitation in the domain. Aerosol regeneration modified the concentration of cloud droplets at cloud base by dynamic recirculation of the aerosols but also had only a minor effect on precipitation. The major conclusion from this study is that the effect of mineral dust particles on clouds and total precipitation is limited by the properties of the atmospheric dynamics and the only effect of aerosol on precipitation may come from significant increase in the concentration of accumulation mode aerosols. In addition, the presence of mineral dust had a much smaller effect on the total precipitation than on its spatial distribution.

scholarly journals Effects of model resolution and parameterizations on the simulations of clouds, precipitation, and their interactions with aerosols

2018 ◽  
Vol 18 (1) ◽  
pp. 13-29 ◽  
Author(s):  
Seoung Soo Lee ◽  
Zhanqing Li ◽  
Yuwei Zhang ◽  
Hyelim Yoo ◽  
Seungbum Kim ◽  
...  
Keyword(s):  
High Resolution ◽  
Numerical Weather Prediction ◽  
Weather Prediction ◽  
Aerosol Concentration ◽  
Cloud System ◽  
Model Resolution ◽  
Substantial Impact ◽  
Numerical Weather ◽  
Saturation Process ◽  
Microphysical Processes

Abstract. This study investigates the roles played by model resolution and microphysics parameterizations in the well-known uncertainties or errors in simulations of clouds, precipitation, and their interactions with aerosols by the numerical weather prediction (NWP) models. For this investigation, we used cloud-system-resolving model (CSRM) simulations as benchmark simulations that adopt high-resolution and full-fledged microphysical processes. These simulations were evaluated against observations, and this evaluation demonstrated that the CSRM simulations can function as benchmark simulations. Comparisons between the CSRM simulations and the simulations at the coarse resolutions that are generally adopted by current NWP models indicate that the use of coarse resolutions as in the NWP models can lower not only updrafts and other cloud variables (e.g., cloud mass, condensation, deposition, and evaporation) but also their sensitivity to increasing aerosol concentration. The parameterization of the saturation process plays an important role in the sensitivity of cloud variables to aerosol concentrations. while the parameterization of the sedimentation process has a substantial impact on how cloud variables are distributed vertically. The variation in cloud variables with resolution is much greater than what happens with varying microphysics parameterizations, which suggests that the uncertainties in the NWP simulations are associated with resolution much more than microphysics parameterizations.

scholarly journals Implementing Gas-to-Particle Partitioning of Semi-Volatile Inorganic Compounds in UCLALES-SALSA

2020 ◽  
Author(s):  
Innocent Kudzotsa ◽  
Harri Kokkola ◽  
Juha Tonttila ◽  
Tomi Raatikainen ◽  
Sami Romakkaniemi
Keyword(s):  
Inorganic Compounds ◽  
Cloud Condensation Nuclei ◽  
Three Dimensional ◽  
Cloud Droplet ◽  
Dominant Factor ◽  
Cloud Droplets ◽  
Cloud Properties ◽  
Cloud Scavenging ◽  
Scavenging Efficiency ◽  
Ccn Activity

Abstract. We investigated the effect of inorganic semi-volatile compounds (SVC) HNO3 and NH3 on the cloud condensation nuclei (CCN) activity of aerosols and the subsequent changes in cloud properties. This was done by upgrading our state-of-the-art large eddy simulator – UCLALES-SALSA, which was modified to include the treatment of the condensation and dissolution of SVCs onto pre-existing aerosols and cloud droplets. The immediate effect of these SVCs on aerosols was to shift the aerosol dry size distribution towards larger sizes as a result of their co-condensation with water vapour. Since the dry size of a CCN is the dominant factor determining its CCN activity, a marked increase in cloud droplet number concentration(similar to the Twomey effect) was noted both in zero- and three-dimensional simulations when gas-phase concentrations of VCs were increased. As the overall amount of precipitation was small in the simulated stratocumulus case, the increase in droplet concentration led to a smaller mean size and reduced drizzle. Within clouds, the smaller droplets contain a relatively higher amount of nitrate than the larger ones, and as the drizzle is mainly formed through large droplets, the ammonium nitrate in-cloud scavenging is weaker than would be estimated based on average droplet composition. The model was also able to simulate the relatively more acidic interstitial particles than cloud droplets. However, below the cloud, condensation of gases on drizzling droplets quickly increases their overall wet scavenging efficiency compared to sulphate.

scholarly journals Aerosol effects on deep convection: the propagation of aerosol perturbations through convective cloud microphysics

2019 ◽  
Vol 19 (4) ◽  
pp. 2601-2627 ◽  
Author(s):  
Max Heikenfeld ◽  
Bethan White ◽  
Laurent Labbouz ◽  
Philip Stier
Keyword(s):  
Latent Heat ◽  
Cloud Condensation Nuclei ◽  
Cloud Microphysics ◽  
Latent Heating ◽  
Microphysics Scheme ◽  
Convective Clouds ◽  
Wide Range ◽  
Microphysical Processes ◽  
Aerosol Effects ◽  
The Impact

Abstract. The impact of aerosols on ice- and mixed-phase processes in deep convective clouds remains highly uncertain, and the wide range of interacting microphysical processes is still poorly understood. To understand these processes, we analyse diagnostic output of all individual microphysical process rates for two bulk microphysics schemes in the Weather and Research Forecasting model (WRF). We investigate the response of individual processes to changes in aerosol conditions and the propagation of perturbations through the microphysics all the way to the macrophysical development of the convective clouds. We perform simulations for two different cases of idealised supercells using two double-moment bulk microphysics schemes and a bin microphysics scheme. The simulations cover a comprehensive range of values for cloud droplet number concentration (CDNC) and cloud condensation nuclei (CCN) concentration as a proxy for aerosol effects on convective clouds. We have developed a new cloud tracking algorithm to analyse the morphology and time evolution of individually tracked convective cells in the simulations and their response to the aerosol perturbations. This analysis confirms an expected decrease in warm rain formation processes due to autoconversion and accretion for more polluted conditions. There is no evidence of a significant increase in the total amount of latent heat, as changes to the individual components of the integrated latent heating in the cloud compensate each other. The latent heating from freezing and riming processes is shifted to a higher altitude in the cloud, but there is no significant change to the integrated latent heat from freezing. Different choices in the treatment of deposition and sublimation processes between the microphysics schemes lead to strong differences including feedbacks onto condensation and evaporation. These changes in the microphysical processes explain some of the response in cloud mass and the altitude of the cloud centre of gravity. However, there remain some contrasts in the development of the bulk cloud parameters between the microphysics schemes and the two simulated cases.

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