scholarly journals Review for “The relative impact of cloud condensation nuclei and ice nucleating particle concentrations on phase-partitioning in Arctic Mixed-Phase Stratocumulus Clouds”

2018 ◽  
Author(s):  
Anonymous
Keyword(s):  
Cloud Condensation Nuclei ◽  
Mixed Phase ◽  
Relative Impact ◽  
Condensation Nuclei ◽  
Phase Partitioning ◽  
Stratocumulus Clouds

scholarly journals The relative impact of cloud condensation nuclei and ice nucleating particle concentrations on phase partitioning in Arctic mixed-phase stratocumulus clouds

2018 ◽  
Vol 18 (23) ◽  
pp. 17047-17059 ◽  
Author(s):  
Amy Solomon ◽  
Gijs de Boer ◽  
Jessie M. Creamean ◽  
Allison McComiskey ◽  
Matthew D. Shupe ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Mixed Phase ◽  
Radiative Properties ◽  
Condensation Nuclei ◽  
Phase Partitioning ◽  
Cloud Dynamics ◽  
Stratocumulus Clouds ◽  
Cloud Ice ◽  
Mixed Phase Clouds ◽  
The Impact

Abstract. This study investigates the interactions between cloud dynamics and aerosols in idealized large-eddy simulations (LES) of Arctic mixed-phase stratocumulus clouds (AMPS) observed at Oliktok Point, Alaska, in April 2015. This case was chosen because it allows the cloud to form in response to radiative cooling starting from a cloud-free state, rather than requiring the cloud ice and liquid to adjust to an initial cloudy state. Sensitivity studies are used to identify whether there are buffering feedbacks that limit the impact of aerosol perturbations. The results of this study indicate that perturbations in ice nucleating particles (INPs) dominate over cloud condensation nuclei (CCN) perturbations; i.e., an equivalent fractional decrease in CCN and INPs results in an increase in the cloud-top longwave cooling rate, even though the droplet effective radius increases and the cloud emissivity decreases. The dominant effect of ice in the simulated mixed-phase cloud is a thinning rather than a glaciation, causing the mixed-phase clouds to radiate as a grey body and the radiative properties of the cloud to be more sensitive to aerosol perturbations. It is demonstrated that allowing prognostic CCN and INPs causes a layering of the aerosols, with increased concentrations of CCN above cloud top and increased concentrations of INPs at the base of the cloud-driven mixed layer. This layering contributes to the maintenance of the cloud liquid, which drives the dynamics of the cloud system.

scholarly journals The relative impact of cloud condensation nuclei and ice nucleating particle concentrations on phase-partitioning in Arctic Mixed-Phase Stratocumulus Clouds

2018 ◽  
Author(s):  
Amy Solomon ◽  
Gijs de Boer ◽  
Jessie M. Creamean ◽  
Allison McComiskey ◽  
Matthew D. Shupe ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Mixed Phase ◽  
Radiative Properties ◽  
Condensation Nuclei ◽  
Phase Partitioning ◽  
Cloud Dynamics ◽  
Stratocumulus Clouds ◽  
Cloud Ice ◽  
Mixed Phase Clouds ◽  
The Impact

Abstract. This study investigates the interactions between cloud dynamics and aerosols in idealized large-eddy simulations of an Arctic mixed-phase stratocumulus cloud observed at Oliktok Point, Alaska in April 2015. This case was chosen because it allows the cloud to form in response to radiative cooling starting from a cloud-free state, rather than requiring the cloud ice and liquid to adjust to an initial cloudy state. Sensitivity studies are used to identify whether there are buffering feedbacks that limit the impact of aerosol perturbations. The results of this study indicate that perturbations in ice nucleating particles (INPs) dominate over cloud condensation nuclei (CCN) perturbations, i.e., an equivalent fractional decrease in CCN and INPs results in an increase in the cloud-top longwave cooling rate, even though the droplet effective radius increases and the cloud emissivity decreases. The dominant effect of ice in the simulated mixed-phase cloud is a thinning rather than a glaciation, causing the mixed-phase clouds to radiate as a grey body and the radiative properties of the cloud to be more sensitive to aerosol perturbations. It is demonstrated that allowing prognostic CCN and INP causes a layering of the aerosols, with increased concentrations of CCN above cloud top and increased concentrations of INP at the base of the cloud-driven mixed-layer. This layering contributes to the maintenance of the cloud liquid, which drives the dynamics of the cloud system.

scholarly journals Effects of Cloud Condensation Nuclei and Ice Nucleating Particles on Precipitation Processes and Supercooled Liquid in Mixed-phase Orographic Clouds

2016 ◽  
Author(s):  
Jiwen Fan ◽  
L. Ruby Leung ◽  
Daniel Rosenfeld ◽  
Paul J. DeMott
Keyword(s):  
Water Content ◽  
Sierra Nevada ◽  
Cloud Condensation Nuclei ◽  
Supercooled Water ◽  
Mixed Phase ◽  
Condensation Nuclei ◽  
Local Circulation ◽  
Orographic Clouds ◽  
Snow Precipitation ◽  
Mixed Phase Clouds

Abstract. How orographic mixed-phase clouds respond to the change of cloud condensation nuclei (CCN) and ice nucleating particles (INPs) are highly uncertain. The main snow production mechanism in warm and cold mixed-phase orographic clouds (referred to as WMOC and CMOC, respectively, distinguished here as those having cloud tops warmer and colder than −20 °C) could be very different. We quantify the CCN and INP impacts on supercooled water content, cloud phases and precipitation for a WMOC and a CMOC case with a set of sensitivity tests. It is found that deposition plays a more important role than riming for forming snow in the CMOC, while the role of riming is dominant in the WMOC case. As expected, adding CCN suppresses precipitation especially in WMOC and low INP. However, this reverses strongly for CCN > 1000 cm−3. We find a new mechanism through which CCN can invigorate mixed-phase clouds over the Sierra Nevada Mountains and drastically intensify snow precipitation when CCN concentrations are high (1000 cm−3 or higher). In this situation, more widespread shallow clouds with greater amount of cloud water form in the valley and foothills, which changes the local circulation through more latent heat release that transports more moisture to the windward slope, leading to much more invigorated mixed-phase clouds over the mountains that produce higher amounts of snow precipitation. Increasing INPs leads to decreased riming and mixed-phase fraction in the CMOC but has the opposite effects in the WMOC, as a result of liquid-limited and ice-limited conditions, respectively. However, it increases precipitation in both cases due to an increase of deposition for the CMOC but enhanced riming and deposition in the WMOC. Increasing INPs dramatically reduces supercooled water content and increases the cloud glaciation temperature, while increasing CCN has the opposite effects with much smaller significance.

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 Preconditioning of overcast-to-broken cloud transitions by riming in marine cold air outbreaks

2021 ◽  
Vol 21 (15) ◽  
pp. 12049-12067
Author(s):  
Florian Tornow ◽  
Andrew S. Ackerman ◽  
Ann M. Fridlind
Keyword(s):  
Boundary Layer ◽  
Liquid Water ◽  
Cloud Condensation Nuclei ◽  
Mixed Phase ◽  
Climate Feedback ◽  
Condensation Nuclei ◽  
Cold Air ◽  
Ice Particles ◽  
The Impact ◽  
Cold Air Outbreaks

Abstract. Marine cold air outbreaks (CAOs) commonly form overcast cloud decks that transition into broken cloud fields downwind, dramatically altering the local radiation budget. In this study, we investigate the impact of frozen hydrometeors on these transitions. We focus on a CAO case in the NW Atlantic, the location of the multi-year flight campaign ACTIVATE (Aerosol Cloud meTeorology Interactions oVer the western ATlantic Experiment). We use MERRA-2 (Modern-Era Retrospective analysis for Research and Applications, version 2) reanalysis fields to drive large eddy simulations with mixed-phase two-moment microphysics in a Lagrangian framework. We find that transitions are triggered by substantial rain (rainwater paths >25 g m−2), and only simulations that allow for aerosol depletion result in sustained breakups, as observed. Using a range of diagnostic ice nucleating particle concentrations, Ninp, we find that increasing ice progressively accelerates transitions, thus abbreviating the overcast state. Ice particles affect the cloud-topped boundary layer evolution, primarily through riming-related processes prior to substantial rain, leading to (1) a reduction in cloud liquid water, (2) early consumption of cloud condensation nuclei, and (3) early and light precipitation cooling and moistening below cloud. We refer to these three effects collectively as “preconditioning by riming”. Greater boundary layer aerosol concentrations available as cloud condensation nuclei (CCN) delay the onset of substantial rain. However, cloud breakup and low CCN concentration final stages are found to be inevitable in this case, due, primarily, to liquid water path buildup. An ice-modulated cloud transition speed suggests the possibility of a negative cloud–climate feedback. To address prevailing uncertainties in the model representation of mixed-phase processes, the magnitude of ice formation and riming impacts and, thereby, the strength of an associated negative cloud–climate feedback process, requires further observational evaluation by targeting riming hot spots with in situ imaging probes that allow for both the characterization of ice particles and abundance of supercooled droplets.

scholarly journals Cloud condensation nuclei as a modulator of ice processes in Arctic mixed-phase clouds

2011 ◽  
Vol 11 (15) ◽  
pp. 8003-8015 ◽  
Author(s):  
S. Lance ◽  
M. D. Shupe ◽  
G. Feingold ◽  
C. A. Brock ◽  
J. Cozic ◽  
...  
Keyword(s):  
Droplet Size ◽  
Indirect Effect ◽  
Cloud Condensation Nuclei ◽  
Droplet Size Distribution ◽  
Mixed Phase ◽  
Condensation Nuclei ◽  
Microphysical Properties ◽  
Ice Particles ◽  
Northern Alaska ◽  
Mixed Phase Clouds

Abstract. We propose that cloud condensation nuclei (CCN) concentrations are important for modulating ice formation of Arctic mixed-phase clouds, through modification of the droplet size distribution. Aircraft observations from the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) study in northern Alaska in April 2008 allow for identification and characterization of both aerosol and trace gas pollutants, which are then compared with cloud microphysical properties. Consistent with previous studies, we find that the concentration of precipitating ice particles (>400 μm) is correlated with the concentration of large droplets (>30 μm). We are further able to link the observed microphysical conditions to aerosol pollution, originating mainly from long range transport of biomass burning emissions. The case studies demonstrate that polluted mixed-phase clouds have narrower droplet size distributions and contain 1–2 orders of magnitude fewer precipitating ice particles than clean clouds at the same temperature. This suggests an aerosol indirect effect leading to greater cloud lifetime, greater cloud emissivity, and reduced precipitation. This result is opposite to the glaciation indirect effect, whereby polluted clouds are expected to precipitate more readily due to an increase in the concentration of particles acting as ice nuclei.

scholarly journals Effects of cloud condensation nuclei and ice nucleating particles on precipitation processes and supercooled liquid in mixed-phase orographic clouds

2017 ◽  
Vol 17 (2) ◽  
pp. 1017-1035 ◽  
Author(s):  
Jiwen Fan ◽  
L. Ruby Leung ◽  
Daniel Rosenfeld ◽  
Paul J. DeMott
Keyword(s):  
Water Content ◽  
Sierra Nevada ◽  
Cloud Condensation Nuclei ◽  
Supercooled Water ◽  
Mixed Phase ◽  
Mountain Range ◽  
Condensation Nuclei ◽  
Orographic Clouds ◽  
Snow Precipitation ◽  
Mixed Phase Clouds

Abstract. How orographic mixed-phase clouds respond to the change in cloud condensation nuclei (CCN) and ice nucleating particles (INPs) are highly uncertain. The main snow production mechanism in warm and cold mixed-phase orographic clouds (referred to as WMOCs and CMOCs, respectively, distinguished here as those having cloud tops warmer and colder than −20 °C) could be very different. We quantify the CCN and INP impacts on supercooled water content, cloud phases, and precipitation for a WMOC case and a CMOC case, with sensitivity tests using the same CCN and INP concentrations between the WMOC and CMOC cases. It was found that deposition plays a more important role than riming for forming snow in the CMOC case, while the role of riming is dominant in the WMOC case. As expected, adding CCN suppresses precipitation, especially in WMOCs and low INPs. However, this reverses strongly for CCN of 1000 cm−3 and larger. We found a new mechanism through which CCN can invigorate mixed-phase clouds over the Sierra Nevada and drastically intensify snow precipitation when CCN concentrations are high (1000 cm−3 or higher). In this situation, more widespread shallow clouds with a greater amount of cloud water form in the Central Valley and foothills west of the mountain range. The increased latent heat release associated with the formation of these clouds strengthens the local transport of moisture to the windward slope, invigorating mixed-phase clouds over the mountains, and thereby producing higher amounts of snow precipitation. Under all CCN conditions, increasing the INPs leads to decreased riming and mixed-phase fraction in the CMOC as a result of liquid-limited conditions, but has the opposite effects in the WMOC as a result of ice-limited conditions. However, precipitation in both cases is increased by increasing INPs due to an increase in deposition for the CMOC but enhanced riming and deposition in the WMOC. Increasing the INPs dramatically reduces supercooled water content and increases the cloud glaciation temperature, while increasing CCN has the opposite effect with much smaller significance.

scholarly journals Precipitation effects of giant cloud condensation nuclei artificially introduced into stratocumulus clouds

2015 ◽  
Vol 15 (1) ◽  
pp. 47-76 ◽  
Author(s):  
E. Jung ◽  
B. A. Albrecht ◽  
H. H. Jonsson ◽  
Y.-C. Chen ◽  
J. H. Seinfeld ◽  
...  
Keyword(s):  
Liquid Water ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Fold Increase ◽  
Liquid Water Content ◽  
Cloud Base ◽  
Condensation Nuclei ◽  
Liquid Water Path ◽  
Base Level ◽  
Stratocumulus Clouds

Abstract. To study the effect of giant cloud condensation nuclei (GCCN) on precipitation processes in stratocumulus clouds, 1–10 μm diameter salt particles (salt powder) were released from an aircraft while flying near cloud top on 3 August 2011 off the central coast of California. The seeded area was subsequently sampled from the aircraft that was equipped with aerosol, cloud, and precipitation probes and an upward-facing cloud radar. During post-seeding sampling, made 30–60 min after seeding, the mean cloud droplet size increased, the droplet number concentration decreased, and large drop (e.g., diameter larger than 10 μm) concentration increased. Average drizzle rates increased from about 0.05 to 0.20 mm h−1, and liquid water path decreased from about 52 to 43 g m−2. Strong radar returns associated with drizzle were observed on the post-seeding cloud-base level-leg flights and were accompanied by a substantial depletion of the cloud liquid water content. The changes were large enough to suggest that the salt particles with concentrations estimated to be 10−2 to 10−4 cm−3 resulted in a four-fold increase in the cloud base rainfall rate and depletion of the cloud water due to rainout. In contrast, a case is shown where the cloud was already precipitating (on 10 August) and the effect of adding GCCN to the cloud was insignificant.

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