Giant aerosols increase precipitation in marine cumulus and stratocumulus clouds

2020 ◽  
Author(s):  
Piotr Dziekan ◽  
Jorgen Jensen ◽  
Wojciech Grabowski ◽  
Hanna Pawłowska
Keyword(s):  
Cloud Model ◽  
Sea Salt ◽  
Cloud Seeding ◽  
Cloud Droplets ◽  
Sea Salt Aerosols ◽  
Stratocumulus Clouds ◽  
Bin Microphysics ◽  
The University ◽  
The Impact ◽  
Precipitation Formation

<p>Sea-salt aerosols with radii exceeding 1 μm have been observed over the oceans. Cloud droplets formed on these giant aerosols can quickly grow to drizzle sizes through condensation of water vapor. Therefore giant aerosols, although not numerous, have been speculated to increase the amount of precipitation produced in clouds. Testing this hypothesis in LES simulations has been difficult, because Eulerian microphysics models are not well suited to model growth of droplets on giant aerosols. On the contrary, Lagrangian microphysics models, which are an emerging alternative to the Eulerian bin microphysics models, can model giant aerosols in a straightforward manner.</p><p>LES simulations performed using the University of Warsaw Lagrangian Cloud Model (UWLCM) will be presented. In UWLCM, the Lagrangian super-droplet microphysics model is used. We will assess how giant aerosols affect precipitation formation in marine cumulus (setup based on the RICO campaign) and stratocumulus clouds (setup based on the research flight 2 of the DYCOMS campaign). It will be discussed how the impact of giant aerosols changes with the concentrations of giant and regular aerosols. The results are of importance also for cloud seeding experiments, in which giant sea-salt aerosols can be released into a cloud.</p>

scholarly journals Impact of Giant Sea Salt Aerosol Particles on Precipitation in Marine Cumuli and Stratocumuli: Lagrangian Cloud Model Simulations

2021 ◽  
Author(s):  
Piotr Dziekan ◽  
Jørgen B. Jensen ◽  
Wojciech W. Grabowski ◽  
Hanna Pawlowska
Keyword(s):  
Marine Boundary Layer ◽  
Cloud Model ◽  
Cloud Condensation Nuclei ◽  
Field Measurements ◽  
Breaking Waves ◽  
Cloud Microphysics ◽  
Sea Salt ◽  
Boundary Layer Clouds ◽  
Bin Microphysics ◽  
The Impact

AbstractThe impact of giant sea salt aerosols released from breaking waves on rain formation in marine boundary layer clouds is studied using large eddy simulations (LES). We perform simulations of marine cumuli and stratocumuli for various concentrations of cloud condensation nuclei (CCN) and giant CCN (GCCN). Cloud microphysics are modeled with a Lagrangian method that provides key improvements in comparison to previous LES of GCCN that used Eulerian bin microphysics. We find that GCCN significantly increase precipitation in stratocumuli. This effect is strongest for low and moderate CCN concentrations. GCCN are found to have a smaller impact on precipitation formation in cumuli. These conclusions are in agreement with field measurements. We develop a simple parameterization of the effect of GCCN on precipitation, accretion, and autoconversion rates in marine stratocumuli.

scholarly journals What Polarimetric Weather Radars Offer to Cloud Modelers: Forward Radar Operators and Microphysical/Thermodynamic Retrievals

Atmosphere ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 362 ◽  
Author(s):  
Alexander V. Ryzhkov ◽  
Jeffrey Snyder ◽  
Jacob T. Carlin ◽  
Alexander Khain ◽  
Mark Pinsky
Keyword(s):  
Cloud Model ◽  
Weather Prediction ◽  
Primary Source ◽  
Polarimetric Radar ◽  
Microphysical Process ◽  
Weather Radars ◽  
Cloud Models ◽  
Cloud Modeling ◽  
Bin Microphysics ◽  
The Impact

The utilization of polarimetric weather radars for optimizing cloud models is a next frontier of research. It is widely understood that inadequacies in microphysical parameterization schemes in numerical weather prediction (NWP) models is a primary cause of forecast uncertainties. Due to its ability to distinguish between hydrometeors with different microphysical habits and to identify “polarimetric fingerprints” of various microphysical processes, polarimetric radar emerges as a primary source of needed information. There are two approaches to leverage this information for NWP models: (1) radar microphysical and thermodynamic retrievals and (2) forward radar operators for converting the model outputs into the fields of polarimetric radar variables. In this paper, we will provide an overview of both. Polarimetric measurements can be combined with cloud models of varying complexity, including ones with bulk and spectral bin microphysics, as well as simplified Lagrangian models focused on a particular microphysical process. Combining polarimetric measurements with cloud modeling can reveal the impact of important microphysical agents such as aerosols or supercooled cloud water invisible to the radar on cloud and precipitation formation. Some pertinent results obtained from models with spectral bin microphysics, including the Hebrew University cloud model (HUCM) and 1D models of melting hail and snow coupled with the NSSL forward radar operator, are illustrated in the paper.

scholarly journals Conditions for super-adiabatic droplet growth after entrainment mixing

2016 ◽  
Vol 16 (14) ◽  
pp. 9421-9433 ◽  
Author(s):  
Fan Yang ◽  
Raymond Shaw ◽  
Huiwen Xue
Keyword(s):  
Cloud Model ◽  
Cloud Droplet ◽  
Droplet Radius ◽  
Droplet Growth ◽  
Critical Height ◽  
Growth Region ◽  
Cloud Droplets ◽  
Environmental Air ◽  
Bin Microphysics ◽  
Entrainment Mixing

Abstract. Cloud droplet response to entrainment and mixing between a cloud and its environment is considered, accounting for subsequent droplet growth during adiabatic ascent following a mixing event. The vertical profile for liquid water mixing ratio after a mixing event is derived analytically, allowing the reduction to be predicted from the mixing fraction and from the temperature and humidity for both the cloud and environment. It is derived for the limit of homogeneous mixing. The expression leads to a critical height above the mixing level: at the critical height the cloud droplet radius is the same for both mixed and unmixed parcels, and the critical height is independent of the updraft velocity and mixing fraction. Cloud droplets in a mixed parcel are larger than in an unmixed parcel above the critical height, which we refer to as the “super-adiabatic” growth region. Analytical results are confirmed with a bin microphysics cloud model. Using the model, we explore the effects of updraft velocity, aerosol source in the environmental air, and polydisperse cloud droplets. Results show that the mixed parcel is more likely to reach the super-adiabatic growth region when the environmental air is humid and clean. It is also confirmed that the analytical predictions are matched by the volume-mean cloud droplet radius for polydisperse size distributions. The findings have implications for the origin of large cloud droplets that may contribute to onset of collision–coalescence in warm clouds.

Giant Sea-Salt Aerosols and Warm Rain Formation in Marine Stratocumulus

2008 ◽  
Vol 65 (12) ◽  
pp. 3678-3694 ◽  
Author(s):  
Jørgen B. Jensen ◽  
Sunhee Lee
Keyword(s):  
Large Scale ◽  
Climate Models ◽  
Cloud Model ◽  
Sea Salt ◽  
Droplet Growth ◽  
Anthropogenic Factors ◽  
Marine Stratocumulus ◽  
Sea Salt Aerosols ◽  
Warm Rain ◽  
Rain Formation

Abstract The concentrations and sizes of smaller aerosols (radius smaller than 0.5 μm) in the marine atmosphere vary owing to natural and anthropogenic factors. The concentrations and sizes of giant and ultragiant aerosols vary primarily due to wind-speed-dependent wave breaking. In climate models the formation of warm rain from marine stratocumulus clouds is usually parameterized based on the drops that form on the smaller aerosols. The present process study, using a stochastic Monte Carlo cloud model, shows that the variability of giant sea-salt aerosols and the variability of smaller aerosol cloud condensation nuclei are equally important in determining precipitation flux in marine stratocumulus. This strongly suggests that the effects of giant sea-salt aerosols should be included in the parameterization of warm rain formation in climate and other large-scale models. The above results are based on highly detailed calculations of droplet growth in an idealized marine stratocumulus cloud; the authors believe that other marine stratus cloud conditions may change the calculated rain rates but that the conclusions regarding the relative importance of small and giant aerosols are robust.

The impact of sea-salt aerosols on particulate inorganic nitrogen deposition in the western Taiwan Strait region, China

2019 ◽  
Vol 228 ◽  
pp. 68-76 ◽  
Author(s):  
Shui-Ping Wu ◽  
Lu-Hong Dai ◽  
Heng Zhu ◽  
Ning Zhang ◽  
Jin-Pei Yan ◽  
...  
Keyword(s):  
Nitrogen Deposition ◽  
Inorganic Nitrogen ◽  
Taiwan Strait ◽  
Sea Salt ◽  
Sea Salt Aerosols ◽  
The Impact

Effect of Aerosols on Freezing Drops, Hail, and Precipitation in a Midlatitude Storm

2015 ◽  
Vol 73 (1) ◽  
pp. 109-144 ◽  
Author(s):  
Eyal Ilotoviz ◽  
Alexander P. Khain ◽  
Nir Benmoshe ◽  
Vaughan T. J. Phillips ◽  
Alexander V. Ryzhkov
Keyword(s):  
Cloud Model ◽  
Cloud Condensation Nuclei ◽  
Maximum Size ◽  
Aerosol Concentration ◽  
Time Dependent ◽  
Cloud Droplets ◽  
Surface Precipitation ◽  
Cloud Water Content ◽  
Hebrew University ◽  
Bin Microphysics

Abstract A midlatitude hail storm was simulated using a new version of the spectral bin microphysics Hebrew University Cloud Model (HUCM) with a detailed description of time-dependent melting and freezing. In addition to size distributions of drops, plate-, columnar-, and branch-type ice crystals, snow, graupel, and hail, new distributions for freezing drops as well as for liquid water mass within precipitating ice particles were implemented to describe time-dependent freezing and wet growth of hail, graupel, and freezing drops. Simulations carried out using different aerosol loadings show that an increase in aerosol loading leads to a decrease in the total mass of hail but also to a substantial increase in the maximum size of hailstones. Cumulative rain strongly increases with an increase in aerosol concentration from 100 to about 1000 cm−3. At higher cloud condensation nuclei (CCN) concentrations, the sensitivity of hailstones’ size and surface precipitation to aerosols decreases. The physical mechanism of these effects was analyzed. It was shown that the change in aerosol concentration leads to a change in the major mechanisms of hail formation and growth. The main effect of the increase in the aerosol concentration is the increase in the supercooled cloud water content. Accordingly, at high aerosol concentration, the hail grows largely by accretion of cloud droplets in the course of recycling in the cloud updraft zone. The main mechanism of hail formation in the case of low aerosol concentration is freezing of raindrops.

scholarly journals Study of the Aerosol Indirect Effect by Large-Eddy Simulation of Marine Stratocumulus

2005 ◽  
Vol 62 (11) ◽  
pp. 3909-3932 ◽  
Author(s):  
Miao-Ling Lu ◽  
John H. Seinfeld
Keyword(s):  
Indirect Effect ◽  
Large Scale ◽  
Sea Salt ◽  
Relative Reduction ◽  
Cloud Droplets ◽  
Marine Stratocumulus ◽  
Aerosol Indirect Effect ◽  
Sea Salt Aerosol ◽  
Large Eddy ◽  
The Impact

Abstract A total of 98 three-dimensional large-eddy simulations (LESs) of marine stratocumulus clouds covering both nighttime and daytime conditions were performed to explore the response of cloud optical depth (τ) to various aerosol number concentrations (Na = 50–2500 cm−3) and the covarying meteorological conditions (large-scale divergence rate and SST). The idealized First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment (FIRE) and the Atlantic Stratocumulus Transition Experiment (ASTEX) Lagrangian 1 sounding profiles were used to represent the lightly and heavily drizzling cases, respectively. The first and second aerosol indirect effects are identified. Through statistical analysis, τ is found be to both positively correlated with Na and cloud liquid water path (LWP) with a higher correlation associated with LWP, which is predominantly regulated by large-scale subsidence and SST. Clouds with high LWP occur under low SST or weak large-scale subsidence. Introduction of a small amount of giant sea salt aerosol into the simulation lowers the number of cloud droplets activated, results in larger cloud droplets, and initiates precipitation for nondrizzling polluted clouds or precedes the precipitation process for drizzling clouds. However, giant sea salt aerosol is found to have a negligible effect on τ for lightly precipitating cases, while resulting in a relative reduction of τ of 3%–77% (increasing with Na, for Na = 1000–2500 cm−3) for heavily precipitating cases, suggesting that the impact of giant sea salt is only important for moist and potentially convective clouds. Finally, a regression analysis of the simulations shows that the second indirect effect is more evident in clear than polluted cases. The second indirect effect is found to enhance (reduce) the overall aerosol indirect effect for heavily (lightly) drizzling clouds; that is, τ is larger (smaller) for the same relative change in Na than considering the Twomey (first indirect) effect alone. The aerosol indirect effect (on τ) is lessened in the daytime afternoon conditions and is dominated by the Twomey effect; however, the effect in the early morning is close but slightly smaller than that in the nocturnal run. Diurnal variations of the aerosol indirect effect should be considered to accurately assess its magnitude.

The Impact of a Potential Public/Private Initiative on a Defined Region of the South Suburban Chicago Metropolitan Area

2019 ◽  
pp. 14-32
Keyword(s):  
Supply Chain ◽  
Economic Impact ◽  
Impact Analysis ◽  
Census Data ◽  
Economic Benefits ◽  
Local Economy ◽  
Market Area ◽  
State And Local ◽  
The University ◽  
The Impact

The university is considered one of the engines of growth in a local economy or its market area, since its direct contributions consist of 1) employment of faculty and staff, 2) services to students, and supply chain links vendors, all of which define the University’s Market area. Indirect contributions consist of those agents associated with the university in terms of community and civic events. Each of these activities represent economic benefits to their host communities and can be classified as the economic impact a university has on its local economy and whose spatial market area includes each of the above agents. In addition are the critical links to the University, which can be considered part of its Demand and Supply chain. This paper contributes to the field of Public/Private Impact Analysis, which is used to substantiate the social and economic benefits of cooperating for economic resources. We use Census data on Output of Goods and Services, Labor Income on Salaries, Wages and Benefits, Indirect State and Local Taxes, Property Tax Revenue, Population, and Inter-Industry to measure economic impact (Implan, 2016).

Working at the Crossroads: A Guide for Border Crossing

2017 ◽  
Vol 4 (2) ◽  
Author(s):  
John Mckiernan-González
Keyword(s):  
American Studies ◽  
Collaborative Work ◽  
Border Crossing ◽  
Keynote Address ◽  
Cross Border ◽  
Entry Points ◽  
Academic Labor ◽  
Boyle Heights ◽  
The University ◽  
The Impact

This article discusses the impact of George J. Sánchez’s keynote address “Working at the Crossroads” in making collaborative cross-border projects more academically legitimate in American studies and associated disciplines. The keynote and his ongoing administrative labor model the power of public collaborative work to shift research narratives. “Working at the Crossroads” demonstrated how historians can be involved—as historians—in a variety of social movements, and pointed to the ways these interactions can, and maybe should, shape research trajectories. It provided a key blueprint and key examples for doing historically informed Latina/o studies scholarship with people working outside the university. Judging by the success of Sánchez’s work with Boyle Heights and East LA, projects need to establish multiple entry points, reward participants at all levels, and connect people across generations.I then discuss how I sought to emulate George Sánchez’s proposals in my own work through partnering with labor organizations, developing biographical public art projects with students, and archiving social and cultural histories. His keynote address made a back-and-forth movement between home communities and academic labor seem easy and professionally rewarding as well as politically necessary, especially in public universities. 

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