Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the southeast Pacific Ocean

Abstract. The southeast Pacific Ocean is covered by the world's largest stratocumulus cloud layer, which has a strong impact on ocean temperatures and climate in the region. The effect of anthropogenic sources of aerosol particles on the stratocumulus deck was investigated during the VOCALS field experiment. Aerosol measurements below and above cloud were made with a ultra-high sensitivity aerosol spectrometer and analytical electron microscopy. In addition to more standard in-cloud measurements, droplets were collected and evaporated using a counterflow virtual impactor (CVI), and the non-volatile residual particles were analyzed. Many flights focused on the gradient in cloud properties on an E-W track along 20° S from near the Chilean coast to remote areas offshore. Mean statistics, including their significance, from eight flights and many individual legs were compiled. Consistent with a continental source of cloud condensation nuclei, below-cloud accumulation-mode aerosol and droplet number concentration generally decreased from near shore to offshore. Single particle analysis was used to reveal types and sources of the enhanced particle number that influence droplet concentration. While a variety of particle types were found throughout the region, the dominant particles near shore were partially neutralized sulfates. Modeling and chemical analysis indicated that the predominant source of these particles in the marine boundary layer along 20° S was anthropogenic pollution from central Chilean sources, with copper smelters a relatively small contribution. Cloud droplets were smaller in regions of enhanced particles near shore. However, physically thinner clouds, and not just higher droplet number concentrations from pollution, both contributed to the smaller droplets. Satellite measurements were used to show that cloud albedo was highest 500–1000 km offshore, and actually slightly lower closer to shore due to the generally thinner clouds and lower liquid water paths there. Thus, larger scale forcings that impact cloud macrophysical properties, as well as enhanced aerosol particles, are important in determining cloud droplet size and cloud albedo. Differences in the size distribution of droplet residual particles and ambient aerosol particles were observed. By progressively excluding small droplets from the CVI sample, we were able to show that the larger drops, some of which may initiate drizzle, contain the largest aerosol particles. Geometric mean diameters of droplet residual particles were larger than those of the below-cloud and above cloud distributions. However, a wide range of particle sizes can act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show that this can occur without invoking differences in chemical composition of cloud-nucleating particles.

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Impacts of aerosol particles on the microphysical and radiative properties of stratocumulus clouds over the Southeast Pacific ocean

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-19715-2012 ◽

2012 ◽

Vol 12 (8) ◽

pp. 19715-19767 ◽

Cited By ~ 3

Author(s):

C. H. Twohy ◽

J. R. Anderson ◽

D. W. Toohey ◽

M. Andrejczuk ◽

A. Adams ◽

...

Keyword(s):

Pacific Ocean ◽

Aerosol Particles ◽

Number Concentration ◽

Radiative Properties ◽

Anthropogenic Sources ◽

Small Contribution ◽

Wide Range ◽

Southeast Pacific ◽

Stratocumulus Clouds ◽

Near Shore

Abstract. The Southeast Pacific Ocean is covered by the world's largest stratocumulus cloud layer, which has a strong impact on ocean temperatures and climate in the region. The effect of anthropogenic sources of aerosol particles such as power plants, urban pollution and smelters on the stratocumulus deck was investigated during the VOCALS field experiment. Aerosol measurements below and above cloud were made with a ultra-high sensitivity aerosol spectrometer and analytical electron microscopy. In addition to more standard in-cloud measurements, droplets were collected and evaporated using a counterflow virtual impactor (CVI), and the non-volatile residual particles were analyzed. Many flights focused on the gradient in cloud properties on an E-W track along 20° S from near the Chilean coast to remote areas offshore. Mean statistics from seven flights and many individual legs were compiled. Consistent with a continental source of cloud condensation nuclei, below-cloud accumulation-mode aerosol and droplet number concentration generally decreased from near shore to offshore. Single particle analysis was used to reveal types and sources of the enhanced particle number. While a variety of particle types were found throughout the region, the dominant particles near shore were partially neutralized sulfates. Modeling and chemical analysis indicated that the predominant source of these particles in the marine boundary layer along 20° S was anthropogenic pollution from central Chilean sources, with copper smelters a relatively small contribution. Cloud droplets were more numerous and smaller near shore, and there was less drizzle. Higher droplet number concentration and physically thinner clouds both contributed to the smaller droplets near shore. Satellite measurements were used to show that cloud albedo was highest 500–1000 km offshore, and actually lower closer to shore due to the generally thinner clouds and lower liquid water paths there. Differences in the size distribution of droplet residual particles and ambient aerosol particles were observed. By progressively excluding small droplets from the CVI sample, we were able to show that the larger drops, which initiate drizzle, contain the largest aerosol particles. Geometric mean diameters of droplet residual particles were larger than those of the below-cloud and above cloud distributions. However, a wide range of particle sizes can act as droplet nuclei in these stratocumulus clouds. A detailed LES microphysical model was used to show that this can occur without invoking differences in chemical composition of cloud-nucleating particles.

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Microphysical variability in southeast Pacific Stratocumulus clouds: synoptic conditions and radiative response

Atmospheric Chemistry and Physics ◽

10.5194/acp-10-6255-2010 ◽

2010 ◽

Vol 10 (13) ◽

pp. 6255-6269 ◽

Cited By ~ 43

Author(s):

D. Painemal ◽

P. Zuidema

Keyword(s):

Boundary Layer ◽

Cloud Droplet ◽

Static Stability ◽

Radiative Properties ◽

Free Troposphere ◽

Subtropical Anticyclone ◽

Lower Cloud ◽

Synoptic Conditions ◽

Southeast Pacific ◽

Stratocumulus Clouds

Abstract. Synoptic and satellite-derived cloud property variations for the southeast Pacific stratocumulus region associated with changes in coastal satellite-derived cloud droplet number concentrations (Nd) are explored. MAX and MIN Nd composites are defined by the top and bottom terciles of daily area-mean Nd values over the Arica Bight, the region with the largest mean oceanic Nd, for the five October months of 2001, 2005, 2006, 2007 and 2008. The ability of the satellite retrievals to capture composite differences is assessed with ship-based data. Nd and ship-based accumulation mode aerosol concentrations (Na) correlate well (r = 0.65), with a best-fit aerosol activation value dln Nddln Na of 0.56 for pixels with Nd>50 cm−3. The adiabatically-derived MODIS cloud depths also correlate well with the ship-based cloud depths (r=0.7), though are consistently higher (mean bias of almost 60 m). The MAX-Nd composite is characterized by a weaker subtropical anticyclone and weaker winds both at the surface and the lower free troposphere than the MIN-Nd composite. The MAX-Nd composite clouds over the Arica Bight are thinner than the MIN-Nd composite clouds, have lower cloud tops, lower near-coastal cloud albedos, and occur below warmer and drier free tropospheres (as deduced from radiosondes and NCEP Reanalysis). CloudSat radar reflectivities indicate little near-coastal precipitation. The co-occurrence of more boundary-layer aerosol/higher Nd within a more stable atmosphere suggests a boundary layer source for the aerosol, rather than the free troposphere. The MAX-Nd composite cloud thinning extends offshore to 80° W, with lower cloud top heights out to 95° W. At 85° W, the top-of-atmosphere shortwave fluxes are significantly higher (~50%) for the MAX-Nd composite, with thicker, lower clouds and higher cloud fractions than for the MIN-Nd composite. The change in Nd at this location is small (though positive), suggesting that the MAX-MIN Nd composite differences in radiative properties primarily reflects synoptic changes. Circulation anomalies and a one-point spatial correlation map reveal a weakening of the 850 hPa southerly winds decreases the free tropospheric cold temperature advection. The resulting increase in the static stability along 85° W is highly correlated to the increased cloud fraction, despite accompanying weaker free tropospheric subsidence.

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Another Look at the Influence of Absorbing Aerosols in Drops on Cloud Absorption: Large Aerosols

Journal of the Atmospheric Sciences ◽

10.1175/2007jas2381.1 ◽

2008 ◽

Vol 65 (2) ◽

pp. 661-669 ◽

Cited By ~ 4

Author(s):

Carynelisa Erlick ◽

Dana Schlesinger

Keyword(s):

Cross Sections ◽

Pure Water ◽

Initial Step ◽

Radiative Properties ◽

Potential Contribution ◽

Cloud Forcing ◽

Wide Range ◽

Stratocumulus Clouds ◽

Absorbing Aerosols ◽

High Absorption

Abstract Since as early as 1969, solar absorbing aerosols inside of cloud drops have been suggested to influence cloud radiative properties. The absorbing aerosols were invoked to help explain two “anomalies”: 1) the maximum visible albedo of thick stratocumulus clouds is observed to be only 0.7–0.8, rather than close to 1.0 as would be expected from pure water clouds, and 2) the total solar cloud forcing ratio is observed to be near 1.5 for a wide range of clouds, rather than near 1.0 as would be expected from pure water clouds. While subsequent studies refuting absorbing aerosols have been limited to certain aerosol and cloud drop size ranges, in this study the authors explore the potential radiative effects of supermicron dust and soot aerosols in cloud drops, which can have especially high absorption cross sections. Because of the lack of measurements and limited microphysical simulations of such supermicron absorbing aerosols, it is not suggested that the calculations will entirely resolve the two anomalies. However, because these aerosols certainly can exist in the vicinity of clouds, the authors suggest that their potential contribution to the understanding of the anomalies should be explored. This study serves as an initial step toward that goal.

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On the generation of internal waves by river plumes in subcritical initial conditions

Scientific Reports ◽

10.1038/s41598-021-81464-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

R. Mendes ◽

J. C. B. da Silva ◽

J. M. Magalhaes ◽

B. St-Denis ◽

D. Bourgault ◽

...

Keyword(s):

Numerical Modeling ◽

Internal Waves ◽

Coastal Waters ◽

Initial Conditions ◽

Spatial Scales ◽

River Plumes ◽

Wide Range ◽

Near Shore ◽

Generation Mechanisms ◽

Douro River

AbstractInternal waves (IWs) in the ocean span across a wide range of time and spatial scales and are now acknowledged as important sources of turbulence and mixing, with the largest observations having 200 m in amplitude and vertical velocities close to 0.5 m s−1. Their origin is mostly tidal, but an increasing number of non-tidal generation mechanisms have also been observed. For instance, river plumes provide horizontally propagating density fronts, which were observed to generate IWs when transitioning from supercritical to subcritical flow. In this study, satellite imagery and autonomous underwater measurements are combined with numerical modeling to investigate IW generation from an initial subcritical density front originating at the Douro River plume (western Iberian coast). These unprecedented results may have important implications in near-shore dynamics since that suggest that rivers of moderate flow may play an important role in IW generation between fresh riverine and coastal waters.

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Study of Temporal Variations of Equivalent Black Carbon in a Coastal City in Northwest Spain Using an Atmospheric Aerosol Data Management Software

Applied Sciences ◽

10.3390/app11020516 ◽

2021 ◽

Vol 11 (2) ◽

pp. 516

Author(s):

María Piñeiro-Iglesias ◽

Javier Andrade-Garda ◽

Sonia Suárez-Garaboa ◽

Soledad Muniategui-Lorenzo ◽

Purificación López-Mahía ◽

...

Keyword(s):

Data Management ◽

Black Carbon ◽

Light Absorption ◽

Atmospheric Aerosol ◽

Urban Areas ◽

Radiative Properties ◽

Anthropogenic Sources ◽

Biomass Combustion ◽

Management Support ◽

Diurnal Variability

Light-absorbing carbonaceous aerosols (including black carbon (BC)) pose serious health issues and play significant roles in atmospheric radiative properties. Two-year measurements (2015–2016) of aerosol light absorption, combined with measurements of sub-micrometric particles, were continuously conducted in A Coruña (northwest (NW) Spain) to determine their light absorption properties: absorption coefficients (σabs) and the absorption Ångström exponent (AAE). The mean and standard deviation of equivalent black carbon (eBC) during the period of study were 0.85 ± 0.83 µg m−3, which are lower than other values measured in urban areas of Spain and Europe. High eBC concentrations found in winter are associated with an increase in emissions from anthropogenic sources in combination with lower mixing layer heights and frequent stagnant conditions. The pronounced diurnal variability suggests a strong influence from local sources. AAE had an average value of 1.26 ± 0.22 which implies that both fossil fuel combustion and biomass burning influenced optical aerosol properties. This also highlights biomass combustion in suburban areas, where the use of wood for domestic heating is encouraged, as an important source of eBC. All data treatment was gathered using SCALA© as atmospheric aerosol data management support software program.

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Hawaii Experimental Acoustics Range for Shallow Water Applications

Marine Technology Society Journal ◽

10.4031/mtsj.45.3.8 ◽

2011 ◽

Vol 45 (3) ◽

pp. 69-76 ◽

Cited By ~ 2

Author(s):

Tom Fedenczuk ◽

Eva-Marie Nosal

Keyword(s):

Shallow Water ◽

Water Environment ◽

Shallow Water Acoustics ◽

Central Node ◽

Long Baseline ◽

Wide Range ◽

Shallow Water Environment ◽

Near Shore ◽

Monitoring And Surveillance ◽

Passive Acoustic

AbstractShallow water acoustics provide a means for monitoring and surveillance of near-shore environments. This paper describes the current and future capabilities of the low- to high-frequency Hawaii Experimental Acoustics Range (HEAR) that was designed to facilitate a wide range of different shallow water acoustics experiments and allow researchers from various institutions to test various array components and configurations. HEAR is a portable facility that consists of multiple hydrophones (12‐16) cabled independently to a common central node. The design allows for variable array configurations and deployments in three modes: experimental (off boats and piers), autonomous, and cabled. An application of HEAR is illustrated by the results from a deployment at Makai Research Pier, Oahu, Hawaii. In this deployment, HEAR was configured as a long-baseline range of two volumetric subarrays to study passive acoustic tracking capabilities in a shallow water environment.

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Airborne measurements of trace gas and aerosol particle emissions from biomass burning in Amazonia

Atmospheric Chemistry and Physics ◽

10.5194/acp-5-2989-2005 ◽

2005 ◽

Vol 5 (11) ◽

pp. 2989-3002 ◽

Cited By ~ 69

Author(s):

P. Guyon ◽

G. P. Frank ◽

M. Welling ◽

D. Chand ◽

P. Artaxo ◽

...

Keyword(s):

Large Scale ◽

Particle Number ◽

Aerosol Particles ◽

Secondary Growth ◽

Combustion Efficiency ◽

Vertical Transport ◽

Airborne Measurements ◽

Sampling Campaign ◽

Wide Range ◽

Emission Ratios

Abstract. As part of the LBA-SMOCC (Large-Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke, Aerosols, Clouds, Rainfall, and Climate) 2002 campaign, we studied the emission of carbon monoxide (CO), carbon dioxide (CO2), and aerosol particles from Amazonian deforestation fires using an instrumented aircraft. Emission ratios for aerosol number (CN) relative to CO (ERCN/CO) fell in the range 14-32 cm-3 ppb-1 in most of the investigated smoke plumes. Particle number emission ratios have to our knowledge not been previously measured in tropical deforestation fires, but our results are in agreement with values usually found from tropical savanna fires. The number of particles emitted per amount biomass burned was found to be dependent on the fire conditions (combustion efficiency). Variability in ERCN/CO between fires was similar to the variability caused by variations in combustion behavior within each individual fire. This was confirmed by observations of CO-to-CO2 emission ratios (ERCO/CO2), which stretched across the same wide range of values for individual fires as for all the fires observed during the sampling campaign, reflecting the fact that flaming and smoldering phases are present simultaneously in deforestation fires. Emission factors (EF) for CO and aerosol particles were computed and a correction was applied for the residual smoldering combustion (RSC) fraction of emissions that are not sampled by the aircraft, which increased the EF by a factor of 1.5-2.1. Vertical transport of smoke from the boundary layer (BL) to the cloud detrainment layer (CDL) and the free troposphere (FT) was found to be a very common phenomenon. We observed a 20% loss in particle number as a result of this vertical transport and subsequent cloud processing, attributable to in-cloud coagulation. This small loss fraction suggests that this mode of transport is very efficient in terms of particle numbers and occurs mostly via non-precipitating clouds. The detrained aerosol particles released in the CDL and FT were larger than in the unprocessed smoke, mostly due to coagulation and secondary growth, and therefore more efficient at scattering radiation and nucleating cloud droplets. This process may have significant atmospheric implications on a regional and larger scale.

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Performance of a Near Shore Oscillating Wave Surge Converter With Variable Flap Configurations in Various Sea Conditions

10.1115/omae2021-62048 ◽

2021 ◽

Author(s):

Landon Sugar ◽

Faete Filho ◽

Tarek Abdel-Salam ◽

Michael Muglia ◽

Kurabachew Duba

Keyword(s):

Wave Energy ◽

Structural Integrity ◽

Specific Reference ◽

Wave Forces ◽

Extreme Wave ◽

Wide Range ◽

Near Shore ◽

Wave States ◽

Pass Through ◽

Survival Mode

Abstract Oscillating Wave Surge Converters (OWSCs) are designed to enter survival mode during extreme wave conditions where they forego the opportunity to extract energy to preserve structural integrity. While this is a good tradeoff, it is important that OWSC technology progresses to a point where energy is constantly extracted as long as waves are present. This work addresses the need for an OWSC that can extract wave energy in a wide range of sea conditions while minimizing structural overloading by regulating the fluid-structure interaction. The OWSC being studied here was conceptually designed and patented by researchers at NREL. It consists of a flap face that resembles household blinds, where the flaps can be opened or closed to accommodate the sea conditions. The performance of this variable geometry OWSC in various, shallow wave states was studied in two numerical modeling programs. Of particular interest were the flap’s hydrodynamic coefficients and potential power generation at a specific reference site. This configuration was predicted to mitigate wave forces by allowing some of the wave energy to pass through the device, thus preserving its structural integrity.

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Environmental impact of the Midia Port - Black Sea (Romania), on the coastal sediment quality

Open Geosciences ◽

10.1515/geo-2016-0018 ◽

2016 ◽

Vol 8 (1) ◽

pp. 174-194 ◽

Cited By ~ 2

Author(s):

Irina Catianis ◽

Constantin Ungureanu ◽

Luca Magagnini ◽

Elisa Ulazzi ◽

Tiziana Campisi ◽

...

Keyword(s):

Heavy Metals ◽

Oil Spills ◽

Environmental Concern ◽

Sediment Quality ◽

Industrial Wastes ◽

Anthropogenic Sources ◽

Water Runoff ◽

Quality Of Water ◽

Wide Range ◽

The Impact

AbstractThe aim of the study was to evaluate the impact of potential pollution sources, mainly from the upstream anthropogenic sources and port-related activities. The in-vestigated area covered a wide range of anthropogenic im-pacts (e.g., industrial wastes, storm water runoff, acciden-tal oil spills, intentional discharges and shipping activities). The quality of water and Sediments was assessed us-ing Standard methods, as physical-chemical parameters, chemistry and biology (microbiology, ecotoxicology) aim-ing to figure the level of pollution and the effect of port-related activities. Seawater quality results agreed generally with environmental Standards. Though, in some samples the concentrations of sulphates (mg/1) and heavy metals (μg/1), as B, As and Se exceeded the recommended lim-its, without posing a serious environmental concern. Most of the surface sediment samples contain critical levels of hydrocarbons (C>12), (mg/kg), polycyclic aromatic hydrocarbons (ng/g) and polychlorobiphenyls (ng/g). For some heavy metals (mg/kg), exchangeable concentrations were found to be very close or above the regulations. The signifi-cance of this study is incontestable taking into account the lack of previous relevant historical data of this area. In this sense, it was possible to indicate, in general, good environmental conditions, despite the industrial and concentrated local port-related activities in the investigated area.

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Wind speed response of marine non-precipitating stratocumulus clouds over a diurnal cycle in cloud-system resolving simulations

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-5811-2016 ◽

2016 ◽

Vol 16 (9) ◽

pp. 5811-5839 ◽

Cited By ~ 11

Author(s):

Jan Kazil ◽

Graham Feingold ◽

Takanobu Yamaguchi

Keyword(s):

Boundary Layer ◽

Wind Speed ◽

Large Scale ◽

Layer Growth ◽

Radiative Properties ◽

Cloud Base ◽

Latent Heat Release ◽

Marine Stratocumulus ◽

Stratocumulus Clouds ◽

Boundary Layer Growth

Abstract. Observed and projected trends in large-scale wind speed over the oceans prompt the question: how do marine stratocumulus clouds and their radiative properties respond to changes in large-scale wind speed? Wind speed drives the surface fluxes of sensible heat, moisture, and momentum and thereby acts on cloud liquid water path (LWP) and cloud radiative properties. We present an investigation of the dynamical response of non-precipitating, overcast marine stratocumulus clouds to different wind speeds over the course of a diurnal cycle, all else equal. In cloud-system resolving simulations, we find that higher wind speed leads to faster boundary layer growth and stronger entrainment. The dynamical driver is enhanced buoyant production of turbulence kinetic energy (TKE) from latent heat release in cloud updrafts. LWP is enhanced during the night and in the morning at higher wind speed, and more strongly suppressed later in the day. Wind speed hence accentuates the diurnal LWP cycle by expanding the morning–afternoon contrast. The higher LWP at higher wind speed does not, however, enhance cloud top cooling because in clouds with LWP ⪆ 50 g m−2, longwave emissions are insensitive to LWP. This leads to the general conclusion that in sufficiently thick stratocumulus clouds, additional boundary layer growth and entrainment due to a boundary layer moistening arises by stronger production of TKE from latent heat release in cloud updrafts, rather than from enhanced longwave cooling. We find that large-scale wind modulates boundary layer decoupling. At nighttime and at low wind speed during daytime, it enhances decoupling in part by faster boundary layer growth and stronger entrainment and in part because shear from large-scale wind in the sub-cloud layer hinders vertical moisture transport between the surface and cloud base. With increasing wind speed, however, in decoupled daytime conditions, shear-driven circulation due to large-scale wind takes over from buoyancy-driven circulation in transporting moisture from the surface to cloud base and thereby reduces decoupling and helps maintain LWP. The total (shortwave + longwave) cloud radiative effect (CRE) responds to changes in LWP and cloud fraction, and higher wind speed translates to a stronger diurnally averaged total CRE. However, the sensitivity of the diurnally averaged total CRE to wind speed decreases with increasing wind speed.

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