Shipboard Measurements of Aerosol Properties in the Coupled Ocean-Atmosphere System of the Northwest Tropical Atlantic

2020 ◽  
Author(s):  
Tim Bates ◽  
Patricia Quinn
Keyword(s):  
Solar Radiation ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Lower Atmosphere ◽  
Radiation Balance ◽  
Tropical Atlantic ◽  
Shallow Convection ◽  
Condensation Nuclei ◽  
Aerosol Properties

<p>The fair-weather cumulus clouds, that cover much of the low-latitude oceans, affect the radiation balance of the planet by reflecting incoming solar radiation and absorbing outgoing longwave radiation.  These clouds also drive atmospheric circulation by mixing the lower atmosphere in a process called shallow convection.  This mixing, in turn, affects sea surface temperature and salinity by moderating the air-sea exchange of energy and moisture.  Marine boundary layer (MBL) atmospheric aerosols play a role in the processes described above by scattering and absorbing solar radiation and by serving as cloud condensation nuclei (CCN) thereby influencing cloud droplet concentrations and size; the extent, lifetime, and albedo of clouds; and the frequency and intensity of precipitation. Quantifying the role of aerosols over the Northwest Tropical Atlantic is critical to advance understanding of shallow convection and air-sea interactions.</p><p>MBL aerosol properties were measured aboard the RV Ronald H. Brown during the EUREC4A and ATOMIC field studies in January/February 2020.  Aerosols encountered during the study include background sulfate/sea spray particles and African dust/biomass burning particles.  Aerosol physical, chemical, optical and cloud condensation nuclei properties will be presented and their interaction with local and regional circulation.</p>

scholarly journals A global off-line model of size-resolved aerosol microphysics: II. Identification of key uncertainties

2005 ◽  
Vol 5 (12) ◽  
pp. 3233-3250 ◽  
Author(s):  
D. V. Spracklen ◽  
K. J. Pringle ◽  
K. S. Carslaw ◽  
M. P. Chipperfield ◽  
G. W. Mann
Keyword(s):  
Nucleation Rate ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Accommodation Coefficient ◽  
Sulfate Aerosol ◽  
Sea Salt ◽  
Condensation Nuclei ◽  
Microphysical Processes ◽  
Global Mean ◽  
Aerosol Properties

Abstract. We use the new GLOMAP model of global aerosol microphysics to investigate the sensitivity of modelled sulfate and sea salt aerosol properties to uncertainties in the driving microphysical processes and compare these uncertainties with those associated with aerosol and precursor gas emissions. Overall, we conclude that uncertainties in microphysical processes have a larger effect on global sulfate and sea salt derived condensation nuclei (CN) and cloud condensation nuclei (CCN) concentrations than uncertainties in present-day sulfur emissions. Our simulations suggest that uncertainties in predicted sulfate and sea salt CCN abundances due to poorly constrained microphysical processes are likely to be of a similar magnitude to long-term changes in sulfate and sea salt CCN due to changes in anthropogenic emissions. A microphysical treatment of the global sulfate aerosol allows the uncertainty in climate-relevant aerosol properties to be attributed to specific processes in a way that has not been possible with simpler aerosol schemes. In particular we conclude that: (1) changes in the binary H2SO4-H2O nucleation rate and condensation rate of gaseous H2SO4 cause a shift in the vertical location of the upper tropospheric CN layer by as much as 3 km, while the shape of the CN profile is essentially pre-served (2) uncertainties in the binary H2SO4-H2O nucleation rate have a relatively insignificant effect on marine boundary layer (MBL) aerosol properties; (3) emitting a fraction of anthropogenic SO2 as particulates (to represent production of sulfate particles in power plant plumes below the scale of the model grid (which is of the order of 300 km)) has the potential to change the global mean MBL sulfate-derived CN concentrations by up to 72%, and changes of up to a factor 20 can occur in polluted continental regions; (4) predicted global mean MBL sulfate and sea salt CCN concentrations change by 10 to 60% when several microphysical processes are changed within reasonable uncertainty ranges; (5) sulfate and sea salt derived CCN concentrations are particularly sensitive to primary particle emissions, with global mean MBL sulfate and sea salt CCN changing by up to 27% and local concentrations over continental regions changing by more than 100% when the percentage of anthropogenic SO2 emitted as particulates is changed from 0 to 5%; (6) large changes in sea spray flux have insignificant effects on global sulfate aerosol except when the mass accommodation coefficient of sulfuric acid on the salt particles is set unrealistically low.

scholarly journals Ultraclean Layers and Optically Thin Clouds in the Stratocumulus-to-Cumulus Transition. Part II: Depletion of Cloud Droplets and Cloud Condensation Nuclei through Collision–Coalescence

2018 ◽  
Vol 75 (5) ◽  
pp. 1653-1673 ◽  
Author(s):  
Kuan-Ting O ◽  
Robert Wood ◽  
Christopher S. Bretherton
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Liquid Water Content ◽  
Cloud Base ◽  
Condensation Nuclei ◽  
Cloud Droplets ◽  
Droplet Concentration ◽  
Cloud Thickness

In Part I, aircraft observations are used to show that ultraclean layers (UCLs) in the marine boundary layer (MBL) are a common feature of the stratocumulus-to-cumulus transition (SCT) region over the northeast Pacific. The ultraclean layers are defined as layers of either cloud or clear air in which the concentration of particles with diameter larger than 0.1 μm is below 10 cm−3. Here, idealized microphysical parcel modeling shows that in the cumulus regime, collision–coalescence can strongly deplete cloud droplet concentration in cumulus (Cu) updrafts, thereby removing cloud condensation nuclei (CCN) from the atmosphere, suggesting that collision scavenging is likely the key process causing the low particle concentration in UCLs. Furthermore, the model results suggest that the stratocumulus regime is typically not favorable for UCL formation, because condensate amounts are generally not large enough to deplete drops in the time it takes to loft air to the upper planetary boundary layer (PBL). A bulk parameterization of the coalescence-scavenging rate is derived based on in situ measurements. The fractional coalescence-scavenging rate is found to be strongly dependent upon liquid water content (LWC) and, hence, the height above cloud base, indicating that a higher cloud top and thus a greater cloud thickness in a Cu updraft is an important factor accounting for the observed sharp rise of UCL coverage in the SCT region. An important implication is that PBL height, which controls maximum cloud thickness, and therefore LWC in updrafts, could be a crucial factor constraining coalescence scavenging and thus the formation of UCLs in the MBL.

scholarly journals Remote sensing the vertical profile of cloud droplet effective radius, thermodynamic phase, and temperature

2011 ◽  
Vol 11 (18) ◽  
pp. 9485-9501 ◽  
Author(s):  
J. V. Martins ◽  
A. Marshak ◽  
L. A. Remer ◽  
D. Rosenfeld ◽  
Y. J. Kaufman ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Energy Balance ◽  
Brightness Temperature ◽  
Vertical Profile ◽  
Water Cycle ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Cloud Microphysics ◽  
Condensation Nuclei ◽  
Thermodynamic Phase

Abstract. Cloud-aerosol interaction is a key issue in the climate system, affecting the water cycle, the weather, and the total energy balance including the spatial and temporal distribution of latent heat release. Information on the vertical distribution of cloud droplet microphysics and thermodynamic phase as a function of temperature or height, can be correlated with details of the aerosol field to provide insight on how these particles are affecting cloud properties and their consequences to cloud lifetime, precipitation, water cycle, and general energy balance. Unfortunately, today's experimental methods still lack the observational tools that can characterize the true evolution of the cloud microphysical, spatial and temporal structure in the cloud droplet scale, and then link these characteristics to environmental factors and properties of the cloud condensation nuclei. Here we propose and demonstrate a new experimental approach (the cloud scanner instrument) that provides the microphysical information missed in current experiments and remote sensing options. Cloud scanner measurements can be performed from aircraft, ground, or satellite by scanning the side of the clouds from the base to the top, providing us with the unique opportunity of obtaining snapshots of the cloud droplet microphysical and thermodynamic states as a function of height and brightness temperature in clouds at several development stages. The brightness temperature profile of the cloud side can be directly associated with the thermodynamic phase of the droplets to provide information on the glaciation temperature as a function of different ambient conditions, aerosol concentration, and type. An aircraft prototype of the cloud scanner was built and flew in a field campaign in Brazil. The CLAIM-3D (3-Dimensional Cloud Aerosol Interaction Mission) satellite concept proposed here combines several techniques to simultaneously measure the vertical profile of cloud microphysics, thermodynamic phase, brightness temperature, and aerosol amount and type in the neighborhood of the clouds. The wide wavelength range, and the use of multi-angle polarization measurements proposed for this mission allow us to estimate the availability and characteristics of aerosol particles acting as cloud condensation nuclei, and their effects on the cloud microphysical structure. These results can provide unprecedented details on the response of cloud droplet microphysics to natural and anthropogenic aerosols in the size scale where the interaction really happens.

scholarly journals Technical Note: Frenkel Halsey and Hill analysis of water on clay minerals: Toward closure between cloud condensation nuclei activity and water adsorption

2019 ◽  
Author(s):  
Courtney D. Hatch ◽  
Paul R. Tumminello ◽  
Megan A. Cassingham ◽  
Ann L. Greenaway ◽  
Rebecca Meredith ◽  
...  
Keyword(s):  
Water Adsorption ◽  
Cloud Condensation Nuclei ◽  
Cloud Droplet ◽  
Technical Note ◽  
Condensation Nuclei ◽  
Adsorption Parameters ◽  
Climate Effect ◽  
Montmorillonite Clays ◽  
Activation Theory ◽  
Cloud Droplet Number Concentration

Abstract. Insoluble atmospheric aerosol, such as mineral dust, has been identified as an important contributor to the cloud droplet number concentration and indirect climate effect. However, empirically-derived Frenkel-Halsey-Hill (FHH) water adsorption parameters remain the largest source of uncertainty in assessing the effect of insoluble aerosol on climate using the FHH activation theory (FHH-AT). Furthermore, previously reported FHH water adsorption parameters for illite and montmorillonite determined from water adsorption measurements below 100 % RH do not satisfactorily agree with values determined from FHH-AT analysis of experimental cloud condensation nuclei (CCN) measurements under supersaturated conditions. The work reported here uses previously reported experimental water adsorption measurements for illite and montmorillonite clays (Hatch et al., 2012; Hatch et al., 2014) to show that improved analysis methods that account for the surface microstructure are necessary to obtain better agreement of FHH parameters between water adsorption and experimental CCN-derived FHH parameters.

Finding linkages between ocean ecosystems and natural marine aerosols in the minimally polluted North Atlantic atmosphere

2020 ◽  
Author(s):  
Patricia Quinn ◽  
Tim Bates ◽  
Eric Saltzman ◽  
Tom Bell ◽  
Mike Behrenfeld
Keyword(s):  
North Atlantic ◽  
Cloud Condensation Nuclei ◽  
Sea Spray ◽  
Marine Aerosols ◽  
Condensation Nuclei ◽  
Surface Ocean ◽  
Cloud Properties ◽  
Sea Spray Aerosol ◽  
Ocean Ecosystems ◽  
Aerosol Properties

<p>The emission of sea spray aerosol (SSA) and dimethylsulfide (DMS) from the ocean results in marine boundary layer aerosol particles that can impact Earth’s radiation balance by directly scattering solar radiation and by acting as cloud condensation nuclei (CCN), thereby altering cloud properties. The surface ocean is projected to warm by 1.3 to 2.8°C globally over the 21<sup>st</sup> century. Impacts of this warming on plankton blooms, ocean ecosystems, and ocean-to-atmosphere fluxes of aerosols and their precursor gases are highly uncertain. A fundamental understanding of linkages between surface ocean ecosystems and ocean-derived aerosols is required to address this uncertainty. One approach for improved understandings of these linkages is simultaneous measurements of relevant surface ocean and aerosol properties in an ocean region with seasonally varying plankton blooms and a minimally polluted overlying atmosphere. The western North Atlantic hosts the largest annual phytoplankton bloom in the global ocean with a large spatial and seasonal variability in plankton biomass and composition. Periods of low aerosol number concentrations associated with unpolluted air masses allow for the detection of linkages between ocean ecosystems and ocean-derived aerosol.</p><p> </p><p>Five experiments were conducted in the western North Atlantic between 2014 and 2018 with the objective of finding links between the bloom and marine aerosols. These experiments include the second Western Atlantic Climate Study (WACS-2) and four North Atlantic Aerosol and Marine Ecosystem Study (NAAMES) cruises. This series of cruises was the first time the western North Atlantic bloom was systematically sampled during every season with extensive ocean and atmosphere measurements able to assess how changes in the state of the bloom might impact ocean-derived aerosol properties. Measurements of unheated and heated number size distributions, cloud condensation nuclei (CCN) concentrations, and aerosol composition were used to identify primary and secondary aerosol components that could be related to the state of the bloom. Only periods of clean marine air, as defined by radon, particle number concentration, aerosol light absorption coefficient, and back trajectories, were included in the analysis.</p><p> </p><p>CCN concentrations at 0.1% supersaturation were best correlated (r<sup>2</sup> = 0.73) with accumulation mode nss SO<sub>4</sub><sup>=</sup>. Sea spray aerosol (SSA) was only correlated with CCN during November when bloom accumulation had not yet occurred and dimethylsulfide (DMS) concentrations were at a minimum. The fraction of CCN attributable to SSA was less than 20% during March, May/June, and September, indicating the limited contribution of SSA to the CCN population of the western North Atlantic atmosphere. The strongest link between the plankton bloom and aerosol and cloud properties appears to be due to biogenic non-seasalt SO<sub>4</sub><sup>=</sup>.</p><p> </p>

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