scholarly journals Modelling mixed-phase clouds with large-eddy model UCLALES-SALSA

2020 ◽  
Author(s):  
Jaakko Ahola ◽  
Hannele Korhonen ◽  
Juha Tonttila ◽  
Sami Romakkaniemi ◽  
Harri Kokkola ◽  
...  
Keyword(s):  
Liquid Layer ◽  
Cloud Model ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Ice Nuclei ◽  
Active Particles ◽  
Large Eddy ◽  
Ice Microphysics ◽  
Intercomparison Study ◽  
Mixed Phase Clouds

<p>We have extended the large-eddy model UCLALES-SALSA (Tonttila et al., 2017) to include formation of ice and mixed-phase clouds. The model has exceptionally detailed aerosol description for both aerosol number and chemical composition. We confirmed the accuracy of newly implemented ice microphysics with a comparison to a previous mixed-phase cloud model intercomparison study.</p><p>In a further simulation the model captured the typical layered structure of Arctic mixed-phase clouds: a liquid layer near cloud top and ice within and below the liquid layer. The simulation also demonstrated how larger droplets froze first. Moreover, the simulation showed realistic freezing rates of droplets within the vertical cloud structure. These characteristics were possible to capture with a heterogeneous ice nucleation scheme, where also ice nucleating particles (INP) are prognosed. Here, dust containing particles acted as INPs.</p><p>The prognostic simulation showed the importance of the self-adjustment of ice nucleation active particles. This is in good agreement with an observational study where resilient mixed-phase clouds are seen together with relatively high ice nuclei concentrations.</p><p>The implemented detailed sectional ice microphysics with prognostic aerosols is essentially important in reproducing the characteristics of mixed-phase clouds. The manuscript of this study is submitted for publication.</p>

scholarly journals Modelling mixed-phase clouds with large-eddy model UCLALES-SALSA

2020 ◽  
Author(s):  
Jaakko Ahola ◽  
Hannele Korhonen ◽  
Juha Tonttila ◽  
Sami Romakkaniemi ◽  
Harri Kokkola ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Liquid Layer ◽  
Cloud Model ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Model Intercomparison ◽  
Large Eddy ◽  
Ice Microphysics ◽  
Intercomparison Study ◽  
Mixed Phase Clouds

Abstract. The large-eddy model UCLALES-SALSA, with exceptionally detailed aerosol description for both aerosol number and chemical composition, has been extended for ice and mixed-phase clouds. Comparison to a previous mixed-phase cloud model intercomparison study confirmed the accuracy of newly implemented ice microphysics. Further simulation with a heterogeneous ice nucleation scheme, where also ice nucleating particles (INP) are a prognostic variable, captured the typical layered structure of Arctic mid-altitude mixed-phase cloud: a liquid layer near cloud top and ice within and below the liquid layer. In addition, the simulation showed realistic freezing rate of droplets within the vertical cloud structure. The represented detailed sectional ice microphysics with prognostic aerosols is crucially important in reproducing mixed-phase clouds.

scholarly journals Modelling mixed-phase clouds with the large-eddy model UCLALES–SALSA

2020 ◽  
Vol 20 (19) ◽  
pp. 11639-11654
Author(s):  
Jaakko Ahola ◽  
Hannele Korhonen ◽  
Juha Tonttila ◽  
Sami Romakkaniemi ◽  
Harri Kokkola ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Liquid Layer ◽  
Cloud Model ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Model Intercomparison ◽  
Large Eddy ◽  
Ice Microphysics ◽  
Intercomparison Study ◽  
Mixed Phase Clouds

Abstract. The large-eddy model UCLALES–SALSA, with an exceptionally detailed aerosol description for both aerosol number and chemical composition, has been extended for ice and mixed-phase clouds. Comparison to a previous mixed-phase cloud model intercomparison study confirmed the accuracy of newly implemented ice microphysics. A further simulation with a heterogeneous ice nucleation scheme, in which ice-nucleating particles (INPs) are also a prognostic variable, captured the typical layered structure of Arctic mid-altitude mixed-phase cloud: a liquid layer near cloud top and ice within and below the liquid layer. In addition, the simulation showed a realistic freezing rate of droplets within the vertical cloud structure. The represented detailed sectional ice microphysics with prognostic aerosols is crucially important in reproducing mixed-phase clouds.

scholarly journals Possible roles of ice nucleation mode and ice nuclei depletion in the extended lifetime of Arctic mixed-phase clouds

2005 ◽  
Vol 32 (18) ◽  
pp. n/a-n/a ◽  
Author(s):  
Hugh Morrison ◽  
Matthew D. Shupe ◽  
James O. Pinto ◽  
Judith A. Curry
Keyword(s):  
Ice Nucleation ◽  
Mixed Phase ◽  
Nucleation Mode ◽  
Ice Nuclei ◽  
Mixed Phase Clouds

scholarly journals The potential influence of Asian and African mineral dust on ice, mixed-phase and liquid water clouds

2010 ◽  
Vol 10 (18) ◽  
pp. 8649-8667 ◽  
Author(s):  
A. Wiacek ◽  
T. Peter ◽  
U. Lohmann
Keyword(s):  
Liquid Water ◽  
Mineral Dust ◽  
Dust Emission ◽  
Ice Nucleation ◽  
Transport Processes ◽  
Mixed Phase ◽  
Ice Clouds ◽  
Cloud Processing ◽  
Ice Nuclei ◽  
Mixed Phase Clouds

Abstract. This modelling study explores the availability of mineral dust particles as ice nuclei for interactions with ice, mixed-phase and liquid water clouds, also tracking the particles' history of cloud-processing. We performed 61 320 one-week forward trajectory calculations originating near the surface of major dust emitting regions in Africa and Asia using high-resolution meteorological analysis fields for the year 2007. Dust-bearing trajectories were assumed to be those coinciding with known dust emission seasons, without explicitly modelling dust emission and deposition processes. We found that dust emissions from Asian deserts lead to a higher potential for interactions with high ice clouds, despite being the climatologically much smaller dust emission source. This is due to Asian regions experiencing significantly more ascent than African regions, with strongest ascent in the Asian Taklimakan desert at ~25%, ~40% and 10% of trajectories ascending to 300 hPa in spring, summer and fall, respectively. The specific humidity at each trajectory's starting point was transported in a Lagrangian manner and relative humidities with respect to water and ice were calculated in 6-h steps downstream, allowing us to estimate the formation of liquid, mixed-phase and ice clouds. Downstream of the investigated dust sources, practically none of the simulated air parcels reached conditions of homogeneous ice nucleation (T≲−40 °C) along trajectories that have not experienced water saturation first. By far the largest fraction of cloud forming trajectories entered conditions of mixed-phase clouds, where mineral dust will potentially exert the biggest influence. The majority of trajectories also passed through atmospheric regions supersaturated with respect to ice but subsaturated with respect to water, where so-called "warm ice clouds" (T≳−40 °C) theoretically may form prior to supercooled water or mixed-phase clouds. The importance of "warm ice clouds" and the general influence of dust in the mixed-phase cloud region are highly uncertain due to both a considerable scatter in recent laboratory data from ice nucleation experiments, which we briefly review in this work, and due to uncertainties in sub-grid scale vertical transport processes unresolved by the present trajectory analysis. For "classical" cirrus-forming temperatures (T≲−40 °C), our results show that only mineral dust ice nuclei that underwent mixed-phase cloud-processing, most likely acquiring coatings of organic or inorganic material, are likely to be relevant. While the potential paucity of deposition ice nuclei shown in this work dimishes the possibility of deposition nucleation, the absence of liquid water droplets at T≲−40 °C makes the less explored contact freezing mechanism (involving droplet collisions with bare ice nuclei) highly inefficient. These factors together indicate the necessity of further systematic studies of immersion mode ice nucleation on mineral dust suspended in atmospherically relevant coatings.

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 The role of ice nuclei recycling in the maintenance of cloud ice in Arctic mixed-phase stratocumulus

2015 ◽  
Vol 15 (18) ◽  
pp. 10631-10643 ◽  
Author(s):  
A. Solomon ◽  
G. Feingold ◽  
M. D. Shupe
Keyword(s):  
Mixed Layer ◽  
Diurnal Cycle ◽  
Radiative Forcing ◽  
Mixed Phase ◽  
Phase Partitioning ◽  
Ice Nuclei ◽  
Large Eddy ◽  
Ice Production ◽  
Cloud Ice ◽  
Mixed Phase Clouds

Abstract. This study investigates the maintenance of cloud ice production in Arctic mixed-phase stratocumulus in large eddy simulations that include a prognostic ice nuclei (IN) formulation and a diurnal cycle. Balances derived from a mixed-layer model and phase analyses are used to provide insight into buffering mechanisms that maintain ice in these cloud systems. We find that, for the case under investigation, IN recycling through subcloud sublimation considerably prolongs ice production over a multi-day integration. This effective source of IN to the cloud dominates over mixing sources from above or below the cloud-driven mixed layer. Competing feedbacks between dynamical mixing and recycling are found to slow the rate of ice lost from the mixed layer when a diurnal cycle is simulated. The results of this study have important implications for maintaining phase partitioning of cloud ice and liquid that determine the radiative forcing of Arctic mixed-phase clouds.

scholarly journals The role of ice nuclei recycling in the maintenance of cloud ice in Arctic mixed-phase stratocumulus

2015 ◽  
Vol 15 (8) ◽  
pp. 11727-11761 ◽  
Author(s):  
A. Solomon ◽  
G. Feingold ◽  
M. D. Shupe
Keyword(s):  
Mixed Layer ◽  
Diurnal Cycle ◽  
Radiative Forcing ◽  
Mixed Phase ◽  
Phase Partitioning ◽  
Ice Nuclei ◽  
Large Eddy ◽  
Ice Production ◽  
Cloud Ice ◽  
Mixed Phase Clouds

Abstract. This study investigates the maintenance of cloud ice production in Arctic mixed phase stratocumulus in large-eddy simulations that include a prognostic ice nuclei (IN) formulation and a diurnal cycle. Balances derived from a mixed-layer model and phase analyses are used to provide insight into buffering mechanisms that maintain ice in these cloud systems. We find that for the case under investigation, IN recycling through subcloud sublimation considerably prolongs ice production over a multi-day integration. This effective source of IN to the cloud dominates over mixing sources from above or below the cloud-driven mixed layer. Competing feedbacks between dynamical mixing and recycling are found to slow the rate of ice lost from the mixed layer when a diurnal cycle is simulated. The results of this study have important implications for maintaining phase partitioning of cloud ice and liquid that determine the radiative forcing of Arctic mixed-phase clouds.

scholarly journals The effects of hygroscopicity of fossil fuel combustion aerosols on mixed-phase clouds

2012 ◽  
Vol 12 (8) ◽  
pp. 19987-20006
Author(s):  
Y. Yun ◽  
J. E. Penner ◽  
O. Popovicheva
Keyword(s):  
Fossil Fuel ◽  
Laboratory Data ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Liquid Water Path ◽  
Anthropogenic Forcing ◽  
Soot Particles ◽  
Cloud Forcing ◽  
Ice Nuclei ◽  
Mixed Phase Clouds

Abstract. Fossil fuel black carbon and organic matter (ffBC/OM) are often emitted together with sulfate, which coats the surface of these particles and changes their hygroscopicity. Observational studies show that the hygroscopicity of soot particles can modulate their ice nucleation ability. To address this, we implemented a scheme that uses 3 levels of soot hygroscopicity (hydrophobic, hydrophilic and hygroscopic) and used laboratory data to specify their ice nuclei abilities. The new scheme results in significant changes to anthropogenic forcing in mixed-phase clouds. The net forcing in off-line studies varies from 0.111 to 1.059 W m−2 depending on the ice nucleation capability of hygroscopic soot particles. The total anthropogenic cloud forcing and whole-sky forcing with the new scheme is 0.06 W m−2 and −2.45 W m−2, respectively, but could be more positive if hygroscopic soot particles are allowed to nucleate ice particles. The change in liquid water path dominates the anthropogenic forcing in mixed-phase clouds.

scholarly journals Ice nucleation and its effect on the atmospheric transport of fungal spores from the classes <i>Agaricomycetes</i>, <i>Ustilaginomycetes</i>, and <i>Eurotiomycetes</i>

2014 ◽  
Vol 14 (4) ◽  
pp. 5013-5059 ◽  
Author(s):  
D. I. Haga ◽  
S. M. Burrows ◽  
R. Iannone ◽  
M. J. Wheeler ◽  
R. Mason ◽  
...  
Keyword(s):  
Transport Model ◽  
Atmospheric Transport ◽  
Fungal Spores ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Cumulative Number ◽  
Near Surface ◽  
Ice Nuclei ◽  
Wide Range ◽  
Mixed Phase Clouds

Abstract. Ice nucleation on fungal spores may affect the frequency and properties of ice and mixed-phase clouds. We studied the ice nucleation properties of 12 different species of fungal spores chosen from three classes: Agaricomycetes, Ustilaginomycetes, and Eurotiomycetes. Agaricomycetes include many types of mushroom species and are cosmopolitan. Ustilaginomycetes are agricultural pathogens and have caused widespread damage to crops. Eurotiomycetes are found on all types of decaying material and include important human allergens. We focused on these classes since they are thought to be abundant in the atmosphere and because there is very little information on the ice nucleation ability of these classes of spores in the literature. All of the fungal spores investigated were found to cause freezing of water droplets at temperatures warmer than homogeneous freezing. The cumulative number of ice nuclei per spore was 0.001 at temperatures between −19 °C and −29 °C, 0.01 between −25.5 °C and −31 °C, and 0.1 between −26 °C and −36 °C. On average, the order of ice nucleating ability for these spores is Ustilaginomycetes > Agaricomycetes &amp;simeq; Eurotiomycetes. We show that at temperatures below −20 °C, all of the fungal spores studied here are less efficient ice nuclei compared to Asian mineral dust on a per surface area basis. We used our new freezing results together with data in the literature to compare the freezing temperatures of spores from the phyla Basidiomycota and Ascomycota, which together make up 98% of known fungal species found on Earth. The data show that within both phyla (Ascomycota and Basidiomycota) there is a wide range of freezing properties, and also that the variation within a phylum is greater than the variation between the average freezing properties of the phyla. Using a global chemistry–climate transport model, we investigated whether ice nucleation on the studied spores, followed by precipitation, can influence the atmospheric transport and global distributions of these spores in the atmosphere. Simulations show that inclusion of ice nucleation scavenging of these fungal spores in mixed-phase clouds can decrease the annual mean concentrations of fungal spores in near-surface air over the oceans and polar regions and decrease annual mean mixing ratios in the upper troposphere.

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.

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