Entrainment of free tropospheric aerosols as a regulating mechanism for cloud condensation nuclei in the remote marine boundary layer

1995 ◽  
Vol 100 (D2) ◽  
pp. 2893 ◽  
Author(s):  
Frank Raes
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Condensation Nuclei ◽  
Tropospheric Aerosols

scholarly journals Manipulating marine stratocumulus cloud amount and albedo: a process-modelling study of aerosol-cloud-precipitation interactions in response to injection of cloud condensation nuclei

2011 ◽  
Vol 11 (1) ◽  
pp. 885-916 ◽  
Author(s):  
H. Wang ◽  
P. J. Rasch ◽  
G. Feingold
Keyword(s):  
Boundary Layer ◽  
Liquid Water ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
Cloud Amount ◽  
Number Concentration ◽  
Condensation Nuclei ◽  
Liquid Water Path ◽  
Water Path ◽  
Injection Method

Abstract. We use a cloud-system-resolving model to study marine-cloud brightening. We examine how injected aerosol particles that act as cloud condensation nuclei (CCN) are transported within the marine boundary layer and how the additional particles in clouds impact cloud microphysical processes, and feedback on dynamics. Results show that the effectiveness of cloud brightening depends strongly on meteorological and background aerosol conditions. Cloud albedo enhancement is very effective in a weakly precipitating boundary layer and in CCN-limited conditions preceded by heavy and/or persistent precipitation. The additional CCN help sustain cloud water by weakening the precipitation substantially in the former case and preventing the boundary layer from collapse in the latter. For a given amount of injected CCN, the injection method (i.e., number and distribution of sprayers) is critical to the spatial distribution of these CCN. Both the areal coverage and the number concentration of injected particles are key players but neither one always emerges as more important than the other. The same amount of injected material is much less effective in either strongly precipitating clouds or polluted clouds, and it is ineffective in a relatively dry boundary layer that supports clouds of low liquid water path. In the polluted case and "dry" case, the CCN injection increases drop number concentration but lowers supersaturation and liquid water path. As a result, the cloud experiences very weak albedo enhancement, regardless of the injection method.

scholarly journals Fast sulfur dioxide measurements correlated with cloud condensation nuclei spectra in the marine boundary layer

2011 ◽  
Vol 11 (22) ◽  
pp. 11511-11519 ◽  
Author(s):  
D. C. Thornton ◽  
A. R. Bandy ◽  
J. G. Hudson
Keyword(s):  
Boundary Layer ◽  
Sulfur Dioxide ◽  
Marine Boundary Layer ◽  
Cloud Condensation Nuclei ◽  
High Rate ◽  
Condensation Nuclei ◽  
Convective Boundary ◽  
Shallow Cumulus ◽  
First Time ◽  
Linear Correlations

Abstract. During the Rain in (shallow) Cumulus over the Ocean (RICO) project simultaneous high rate sulfur dioxide (SO2) measurements and cloud condensation nuclei (CCN) spectra were made for the first time. For research flight 14 (14 January 2005) the convective boundary layer was impacted by precipitation and ship plumes for much of the midday period but not in the late afternoon. Number densities of accumulation mode aerosols (0.14 to 0.2 μm diameter) were a factor of two greater in the later period while CCN were 35% to 80% greater for aerosols that activate at supersaturations >0.1%. Linear correlations of SO2 and CCN were found for SO2 concentrations ranging from 20 to 600 parts-per-trillion (pptv). The greatest sensitivities were for SO2 and CCN that activate at supersaturations >0.1% for both clean and polluted air. In a region unaffected by pollution SO2 was linearly correlated only with CCN at >0.2% supersaturation. These correlations imply that the smallest CCN may be activated by SO2 through heterogeneous conversion. Evidence for entrainment of CCN from the cloud layer into the CBL was found.

scholarly journals Properties of cloud condensation nuclei (CCN) in the trade wind marine boundary layer of the western North Atlantic

2016 ◽  
Vol 16 (4) ◽  
pp. 2675-2688 ◽  
Author(s):  
Thomas B. Kristensen ◽  
Thomas Müller ◽  
Konrad Kandler ◽  
Nathalie Benker ◽  
Markus Hartmann ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Long Range ◽  
North Atlantic ◽  
Particle Number ◽  
Marine Boundary Layer ◽  
Mineral Dust ◽  
Cloud Condensation Nuclei ◽  
Sea Salt ◽  
Condensation Nuclei ◽  
Accumulation Mode

Abstract. Cloud optical properties in the trade winds over the eastern Caribbean Sea have been shown to be sensitive to cloud condensation nuclei (CCN) concentrations. The objective of the current study was to investigate the CCN properties in the marine boundary layer (MBL) in the tropical western North Atlantic, in order to assess the respective roles of inorganic sulfate, organic species, long-range transported mineral dust and sea-salt particles. Measurements were carried out in June–July 2013, on the east coast of Barbados, and included CCN number concentrations, particle number size distributions and offline analysis of sampled particulate matter (PM) and sampled accumulation mode particles for an investigation of composition and mixing state with transmission electron microscopy (TEM) in combination with energy-dispersive X-ray spectroscopy (EDX). During most of the campaign, significant mass concentrations of long-range transported mineral dust was present in the PM, and influence from local island sources can be ruled out. The CCN and particle number concentrations were similar to what can be expected in pristine marine environments. The hygroscopicity parameter κ was inferred, and values in the range 0.2–0.5 were found during most of the campaign, with similar values for the Aitken and the accumulation mode. The accumulation mode particles studied with TEM were dominated by non-refractory material, and concentrations of mineral dust, sea salt and soot were too small to influence the CCN properties. It is highly likely that the CCN were dominated by a mixture of sulfate species and organic compounds.

scholarly journals Large contribution of organics to condensational growth and formation of cloud condensation nuclei (CCN) in remote marine boundary layer

2020 ◽  
Author(s):  
Guangjie Zheng ◽  
Chongai Kuang ◽  
Janek Uin ◽  
Thomas Watson ◽  
Jian Wang
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Global Climate ◽  
Biological Activities ◽  
Cloud Condensation Nuclei ◽  
Particle Growth ◽  
Large Contribution ◽  
Condensation Nuclei ◽  
Condensational Growth

Abstract. Marine low clouds strongly influence global climate, and their radiative effects are particularly susceptible to the concentration of cloud condensation nuclei (CCN). One major source of CCN is condensational growth of pre-CCN particles, and sulfate has long been considered the major condensing species in remote marine boundary layer. While some studies suggested that secondary organic species can contribute to the particle growth, its importance remains unclear. Here we present the first long-term observational evidence that organics play an important role in particle growth over remote oceans. To the contrary of traditional thinking, sulfate dominated condensational growth for only a small (∼18 %) fraction of the 62 observed growth events, even fewer than the organic-dominated events (24 %). During most (58 %) growth events, the major condensing species included both organics and sulfate. Potential precursors of the secondary organics are volatile organic compounds from ocean biological activities and those produced by the air-sea interfacial oxidation. Our results indicate that the condensation of secondary organics contributes strongly to the growth of pre-CCN particles, and thereby the CCN population over remote oceans.

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