Slide 1

Production mechanism, number concentration, size distribution, chemical composition, and optical properties of sea spray aerosols[Source: wikipedia]Wind entrains air into surface waters, leading to bubble formationBubbles rise to the top and burst producing residual particles

[Source: daily mail]Workshop, Raleigh June 4-6 2012Prof. Markus Petters1

[Petters et al., JGR, 2006]The role of marine aerosols in determining cloud albedo, precipitation, and structure

Quotes from an Andreae et al. (2009).The number size distribution of the sea salt aerosol extends well down into the submicron range and indeed commonly peaks there numerous recent studies have revealed a substantial organic presence even in remote marine air.It had long been thought that most marine sub-micron particles are primarily comprised of sulphate derived from the oxidation of dimethyl sulfide emitted from ocean surface and SO2 from long range transport of continental sources and ship emissions.

[ODowd et al. , Nature, 2004]Hygroscopicity (diameter growth factor) as a proxy for aggregate chemical compositionLow (< 0.6) measured hygroscopicities indicate substantial contribution of organic compounds

[Pringle et al., ACP, 2010, ECHAM/MESSy Atmospheric Chemistry (EMAC) model]

[Snider and Petters , ACP 2008][Wex et al., GRL, 2010]Histogram of growth factor measurementtaken over the ocean Growth factor data from DYCOMS-II(remote Pacific, 7 flights in JulyWhere is all the sea salt? Does sea-spray contribute to aerosol number? Does sea spray include a dominant organic source?

[Blanchard and Syzdek, JGR, 1988]

[Wu et al., 1992]Bottom up approach: lab studies combined with bubble spectra[Blanchard and Syzdek, JGR, 1988]

[Lewis and Schwartz, 2004]Bottom up approach: aerosol number production/bubble scatter widely do we accept such large uncertainties?Organic coatings on bubblesThe thickness of the organic coating for oceanic bubbles ranges from 0.01 m for lipids to 1 m for proteins such as glycoproteinsCoating occurs within a few seconds for bubbles < 300 mCoatings stabilize the bubble potentially through their surfactant propertiesLarge bubbles (mm size) are not completely coatedImportant for ocean optical properties

[Chalmers and Bavarian, 1991][Thorpe 1982, Yount 1979 and others]Zhang: The volume scattering function of natural bubble populations: From Finally, once generated, natural bubbles with sizes ,300 micor m are coated with a layer of organic film on a timescale of seconds, and only for a very small part of their lifetime can bubbles be considered clean (Thorpe 1982). The organic film will help stabilize microbubbles by altering buoyancy and blocking gas transfer (Yount 1979) or by providing mechanical strength (Johnson and Wangersky 1987). The thickness of the organic coating for oceanic bubbles ranges from 0.01 micor m for lipids such as fatty esters, fatty acids, and fatty alcohols to 1 micro m for proteins such as glycoproteins and proteoglycans (see Zhang 1998).

12Trying to understand production of organics in the laboratory Aerosolmeasurement

filtered air

[Bates et al., 2012, JGR in press]

Modini et al. ACP, 2010Wex, Fuentes et al., AMET/AMT, 2010Keene et al., JGR 2007Facchini et al., GRL, 2008Organic fractions from sea-spray are all over the map, but many studies show that it is difficult to emit organicsBates al. JGR, 2012To what level do we need to decompose the system? Single bubble, single plume, single whitecap, single model gridbox?

[Deane and Stokes, Nature, 2002]Field vs. Laboratory Measurements Very challenging measurement environment Difficult to isolate sea-spray from secondary aerosol and free- troposphere entrainmentDifficult to control for key variables (wind speed, sea-water composition, wind fetch, wet and dry deposition, evolution of size distribution, atmospheric turbulence ) Studies in great detail are possible, working towards mechanistic understandingPrecise control over variables (bubble size, water composition, surface layer)Main critique: experiments are not representative (bubble plume, atmospheric turbulence )

http://termserv.casaccia.enea.it/term/brivido/brivido.html

Courtesy of Jeff ReidDifferent questions may need different fociMass emissions (optical properties)Number emissions (CCN properties: size + chemical composition)Special emissions (surfactants affecting CCN properties, ice nuclei emissions)