scholarly journals Estimating the potential cooling effect of cirrus thinning achieved via the seeding approach

2021 ◽  
Vol 21 (13) ◽  
pp. 10609-10624
Author(s):  
Jiaojiao Liu ◽  
Xiangjun Shi
Keyword(s):  
Ice Nucleation ◽  
Cooling Effect ◽  
Low Latitude ◽  
Sensitivity Experiment ◽  
Ice Nuclei ◽  
Community Atmosphere Model ◽  
Seeding Method ◽  
Global Cooling ◽  
Solar Noon ◽  
Mixed Phase Clouds

Abstract. Cirrus thinning is a newly emerging geoengineering approach to mitigate global warming. To sufficiently exploit the potential cooling effect of cirrus thinning with the seeding approach, a flexible seeding method is used to calculate the optimal seeding number concentration, which is just enough to prevent homogeneous ice nucleation from occurring. A simulation using the Community Atmosphere Model version 5 (CAM5) with the flexible seeding method shows a global cooling effect of -1.36±0.18 W m−2, which is approximately two-thirds of that from artificially turning off homogeneous nucleation (-1.98±0.26 W m−2). However, simulations with fixed seeding ice nuclei particle number concentrations of 20 and 200 L−1 show a weak cooling effect of -0.27±0.26 W m−2 and warming effect of 0.35±0.28 W m−2, respectively. Further analysis shows that cirrus seeding leads to a significant warming effect of liquid and mixed-phase clouds, which counteracts the cooling effect of cirrus clouds. This counteraction is more prominent at low latitudes and leads to a pronounced net warming effect over some low-latitude regions. The sensitivity experiment shows that cirrus seeding carried out at latitudes with solar noon zenith angles greater than 12∘ could yield a stronger global cooling effect of −2.00 ± 0.25 W m−2. Overall, the potential cooling effect of cirrus thinning is considerable, and the flexible seeding method is essential.

scholarly journals Estimating the potential cooling effect of cirrus thinning achieved via the seeding approach

2021 ◽  
Author(s):  
Jiaojiao Liu ◽  
Xiangjun Shi
Keyword(s):  
Ice Nucleation ◽  
Cooling Effect ◽  
Low Latitude ◽  
Sensitivity Experiment ◽  
Ice Nuclei ◽  
Community Atmosphere Model ◽  
Seeding Method ◽  
Global Cooling ◽  
Solar Noon ◽  
Mixed Phase Clouds

Abstract. Cirrus thinning is a newly emerging geoengineering approach to mitigate global warming. To sufficiently exploit the potential cooling effect of cirrus thinning with the seeding approach, a flexible seeding method is used to calculate the optimal seeding number concentration, which is just enough to prevent homogeneous ice nucleation from occurring. A simulation using the Community Atmosphere Model version 5 (CAM5) with the flexible seeding method shows a global cooling effect of 1.36 ± 0.18 W m−2, which is approximately two-thirds of that from artificially turning off homogeneous nucleation (−1.98 ± 0.26 W m−2). However, simulations with fixed seeding ice nuclei particle number concentrations of 20 and 200 L−1 show a weak cooling effect of −0.27 ± 0.26 W m−2 and warming effect of 0.35 ± 0.28 W m−2, respectively. Further analysis shows that cirrus seeding leads to a significant warming effect of liquid and mixed-phase clouds, which counteracts the cooling effect of cirrus clouds. This counteraction is more prominent at low latitudes and leads to a pronounced net warm effect over some low latitude regions. The sensitivity experiment shows that cirrus seeding carried out at latitudes with solar noon zenith angles greater than 12° could yields a stronger global cooling effect of −2.00 ± 0.25 W m−2. Overall, the potential cooling effect of cirrus thinning is considerable, and the flexible seeding method is essential.

A comprehensive estimate of the global cooling effect from hindering homogeneous ice nucleation under cirrus conditions with CAM5

2020 ◽  
Author(s):  
Jiaojiao Liu ◽  
Xiangjun Shi
Keyword(s):  
Climate Modeling ◽  
Ice Nucleation ◽  
Fixed Number ◽  
Cirrus Clouds ◽  
Ice Crystals ◽  
Cooling Effect ◽  
Minimum Concentration ◽  
Community Atmosphere Model ◽  
Global Cooling ◽  
Cooling Effects

<p>The warming effect of cirrus clouds is well-known. In recent years, in order to mitigate global warming, cirrus cloud thinning as a newly emerging method of geoengineering has been studied based on climate modeling. Adding a few (~10 L<sup>–1</sup>) INPs (ice nucleating particles including ice crystals) might hinder homogeneous ice nucleation, which can produce a large number of ice crystals (~1000 L<sup>–1</sup>), and then reduce cirrus clouds. On the other hand, the cirrus clouds might increase if too much INPs were added. Therefore, the effectiveness of cirrus seeding on cooling our earth is still in debate. In this study, we developed a method (optimal seeding scheme) to calculate the minimum concentration of seeding INPs, which is just enough to prevent homogeneous nucleation from happening. Simulation with the Community Atmosphere Model version 5(CAM5) using the optimal seeding scheme shows a significant cooling effect (–1.4 W/m<sup>2</sup>), which is equal to two-thirds of the cooling potential (–2.1 W/m<sup>2</sup>) derived from the pure heterogeneous simulation (i.e., homogeneous ice nucleation is artificially switched off). Seeding fixed 20 L<sup>-1</sup> and 200 L<sup>-1</sup> concentrations of INPs show the global average radiative effect at –0.5 W m<sup>-2</sup> (cooling) and 0.1 W m<sup>-2</sup> (warming), respectively. The cooling effect of seeding fixed number concentration of INPs is not obvious, which is consistent with previous studies. Furthermore, using the optimal seeding scheme, the sensitivities of cooling effects to seeding area, ice nucleation parameterizations and homogeneous ice nucleation occurrence frequency are also investigated.</p>

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 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 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

&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;

scholarly journals Cloud icing by mineral dust and impacts to aviation safety

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Slobodan Nickovic ◽  
Bojan Cvetkovic ◽  
Slavko Petković ◽  
Vassilis Amiridis ◽  
Goran Pejanović ◽  
...  
Keyword(s):  
Mineral Dust ◽  
Weather Conditions ◽  
Ice Nucleation ◽  
Aircraft Accidents ◽  
Ice Nuclei ◽  
Loss And Damage ◽  
Cloud Ice ◽  
Convective Weather ◽  
First Time ◽  
Engine Power

AbstractIce particles in high-altitude cold clouds can obstruct aircraft functioning. Over the last 20 years, there have been more than 150 recorded cases with engine power-loss and damage caused by tiny cloud ice crystals, which are difficult to detect with aircraft radars. Herein, we examine two aircraft accidents for which icing linked to convective weather conditions has been officially reported as the most likely reason for catastrophic consequences. We analyze whether desert mineral dust, known to be very efficient ice nuclei and present along both aircraft routes, could further augment the icing process. Using numerical simulations performed by a coupled atmosphere-dust model with an included parameterization for ice nucleation triggered by dust aerosols, we show that the predicted ice particle number sharply increases at approximate locations and times of accidents where desert dust was brought by convective circulation to the upper troposphere. We propose a new icing parameter which, unlike existing icing indices, for the first time includes in its calculation the predicted dust concentration. This study opens up the opportunity to use integrated atmospheric-dust forecasts as warnings for ice formation enhanced by mineral dust presence.

scholarly journals Condensed-phase biogenic–anthropogenic interactions with implications for cold cloud formation

2017 ◽  
Vol 200 ◽  
pp. 165-194 ◽  
Author(s):  
Joseph C. Charnawskas ◽  
Peter A. Alpert ◽  
Andrew T. Lambe ◽  
Thomas Berkemeier ◽  
Rachel E. O’Brien ◽  
...  
Keyword(s):  
Freezing Temperature ◽  
Organic Aerosol ◽  
Ice Nucleation ◽  
Mixed Phase ◽  
Cloud Formation ◽  
Fossil Fuel Combustion ◽  
Soot Particles ◽  
Ice Nuclei ◽  
Deliquescence Relative Humidity ◽  
Homogeneous Freezing

Anthropogenic and biogenic gas emissions contribute to the formation of secondary organic aerosol (SOA). When present, soot particles from fossil fuel combustion can acquire a coating of SOA. We investigate SOA–soot biogenic–anthropogenic interactions and their impact on ice nucleation in relation to the particles’ organic phase state. SOA particles were generated from the OH oxidation of naphthalene, α-pinene, longifolene, or isoprene, with or without the presence of sulfate or soot particles. Corresponding particle glass transition (Tg) and full deliquescence relative humidity (FDRH) were estimated using a numerical diffusion model. Longifolene SOA particles are solid-like and all biogenic SOA sulfate mixtures exhibit a core–shell configuration (i.e.a sulfate-rich core coated with SOA). Biogenic SOA with or without sulfate formed ice at conditions expected for homogeneous ice nucleation, in agreement with respectiveTgand FDRH. α-pinene SOA coated soot particles nucleated ice above the homogeneous freezing temperature with soot acting as ice nuclei (IN). At lower temperatures the α-pinene SOA coating can be semisolid, inducing ice nucleation. Naphthalene SOA coated soot particles acted as ice nuclei above and below the homogeneous freezing limit, which can be explained by the presence of a highly viscous SOA phase. Our results suggest that biogenic SOA does not play a significant role in mixed-phase cloud formation and the presence of sulfate renders this even less likely. However, anthropogenic SOA may have an enhancing effect on cloud glaciation under mixed-phase and cirrus cloud conditions compared to biogenic SOA that dominate during pre-industrial times or in pristine areas.

scholarly journals Ice nucleation efficiency of AgI: review and new insights

2016 ◽  
Author(s):  
Claudia Marcolli ◽  
Baban Nagare ◽  
André Welti ◽  
Ulrike Lohmann
Keyword(s):  
Water Saturation ◽  
Experimental Studies ◽  
Freezing Temperature ◽  
Nucleating Agent ◽  
Companion Paper ◽  
Chem Phys ◽  
Ice Nucleation ◽  
Lattice Match ◽  
Ice Nuclei ◽  
Immersion Freezing

Abstract. AgI is one of the best investigated ice nuclei. It has relevance for the atmosphere since it is used for glaciogenic cloud seeding. Theoretical and experimental studies over the last sixty years provide a complex picture of silver iodide as ice nucleating agent with conflicting and inconsistent results. This review compares experimental ice nucleation studies in order to analyse the factors that influence the ice nucleation ability of AgI. We have performed experiments to compare contact and immersion freezing by AgI. This is one of three papers that describe and analyse contact and immersion freezing experiments with AgI. In Nagare et al. (Nagare, B., Marcolli, C., Stetzer, O., and Lohmann, U.: Comparison of measured and calculated collision efficiencies at low temperatures, Atmos. Chem. Phys., 15, 13759–13776, doi:10.5194/acp-15-13759-2015, 2015) collision efficiencies based on contact freezing experiments with AgI are determined and compared with theoretical formulations. In a companion paper, contact freezing experiments are compared with immersion freezing experiments conducted with AgI, kaolinite, and ATD as ice nuclei. The following picture emerges from this analysis: The ice nucleation ability of AgI seems to be enhanced when the AgI particle is on the surface of a droplet, which is indeed the position that a particle takes when it can freely move in a droplet. Ice nucleation by particles with surfaces exposed to air, depends on water adsorption. AgI surfaces seem to be most efficient as ice nuclei when they are exposed to relative humidity at or even above water saturation. For AgI particles that are totally immersed in water, the freezing temperature increases with increasing AgI surface area. Higher threshold freezing temperature seem to correlate with improved lattice matches as can be seen for AgI-AgCl solid solutions and 3AgI•NH4I•6H2O, which have slightly better lattice matches with ice than AgI and also higher threshold freezing temperatures. However, the effect of a good lattice match is annihilated when the surfaces have charges. Also, the ice nucleation ability seems to decrease during dissolution of AgI particles. This introduces an additional history and time dependence of ice nucleation in cloud chambers with short residence times.

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