Parameterisation of particle fluxes
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Parameterisation of particle fluxes. Gerrit de Leeuw. Aerosol. Particle fluxes are more complex than gas fluxes. Particles: Size from <10 nm to > 100 µm Chemical composition: Sea salt Inorganic salts Organics Hygroscopicity Primary marine aerosol Bubble mediated film and jet drops

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Parameterisation of particle fluxes

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Parameterisation of particle fluxes

Parameterisation of particle fluxes

Gerrit de Leeuw


Aerosol

Aerosol

Particle fluxes are more complex than gas fluxes

Particles:

  • Size from <10 nm to > 100 µm

  • Chemical composition:

    • Sea salt

    • Inorganic salts

    • Organics

    • Hygroscopicity

  • Primary marine aerosol

    • Bubble mediated film and jet drops

    • Spume drops

  • Secondary production

  • Transport of anthropogenic and natural aerosol from land

  • Chemical transformation

  • Gerrit de Leeuw


    Primary marine aerosol

    Primary marine aerosol

    • Breaking waves are the major source of sea spray aerosol

    • At intermediate wind speeds, the bubbles produced by breaking waves are the dominant source of sea spray aerosol

    • Sea spray aerosol source functions estimates vary by many orders of magnitude;

    • Sea spray aerosol concentrations vary by one order of magnitude

    • Bubble concentrations vary by approx one order of magnitude

    Gerrit de Leeuw


    Aerosol source functions

    Aerosol source functions

    (Andreas, 1998)

    Gerrit de Leeuw


    Sea salt concentrations

    Sea salt concentrations

    Concentrations of sea salt aerosol measured at various locations are very variable;

    Gong et al., 1997

    Gerrit de Leeuw


    Parameterisation of particle fluxes

    Bubbles

    Concentrations of bubbles , a major source for sea salt aerosol at lower wind speeds (<9 ms-1), are also very variable;

    Gerrit de Leeuw


    Effect of water temperature on sea salt aerosol spectra produced from bubbles

    Effect of water temperature on sea salt aerosol spectra produced from bubbles

    23oC

    15oC

    5oC

    -2oC

    Mårtensson et al., 2003

    Gerrit de Leeuw


    Aerosol source functions1

    Aerosol source functions

    “Traditional” interest is in very large particles contributing to heat and water vapour fluxes

    Currently more focus on submicron particles influencing climate and atmospheric chemistry

    Gerrit de Leeuw


    Aerosol source functions2

    Aerosol source functions

    Since Andreas (1998), several independent determinations of the sea spray source function, using different techniques, have been published:

    • Smith and Harrison (1998)

    • De Leeuw et al., 2000

    • Nilsson et al. (2001)

    • Reid et al. (2001)

    • Vignati et al. (2001)

    • Andreas et al. (2001)

    • Mårtensson et al. (2003)

    Results are converging to within one order of magnitude

    Gerrit de Leeuw


    Aerosol source functions3

    Aerosol source functions

    Other studies are underway:

    • Field campaigns:

      • RED (Pacific)

      • Mace Head (Quest, NAMBLEX)

      • UNISOURCE (Duck, NC, Oct-Nov 2004)

    • Laboratory experiments:

      • Stockholm: bubble mediated in real sea water, water temp 2-22oC

      • Galway: bubble mediated, effects of organics

    Gerrit de Leeuw


    Techniques

    Techniques

    • Whitecap cover: W=W(u10, ….) Bubble-mediated source function dF/dr=F(…..)

    • Balance equation

    • Inverse modeling

    • Coastal boundary layer

    • Profile measurements

    • Eddy covariance

      Instrumentation

    • CLASP

    Gerrit de Leeuw


    Sea spray source functions

    Sea Spray Source Functions

    • New experimental techniques:

      • Direct covariance

      • Bubbles

    • New experimental approaches

    • Modeling approaches

    Nilsson et al., 2003

    Gerrit de Leeuw


    Parameterisation of particle fluxes

    Bubble measurements:Optical, 15-500 m radiusCalibrated

    (Leifer et al., JAOTech 2003)

    Gerrit de Leeuw


    Particle flux parameterization

    Particle flux parameterization

    • Sea spray source functions are traditionally (mainly) parameterized in terms of wind speed U10

    • Significant improvement of parameterization for whitecap cover W by including both oceanic and atmospheric parameters (Lafon, 2004; Woolf 2004):

      • Wave height

      • Friction velocity

    Gerrit de Leeuw


    Particle flux parameters

    Particle flux parameters

    Sea Spray workshop (Skipton, UK, May 2004) :

    • Wind speed

    • Fetch

    • Wave conditions (height, steepness, age, ….)

    • Atmospheric stability (air-sea temperature difference)

    • Micro-meteorological parameters (friction velocity, u*; roughness length, zo)

    • Bulk sea water temperature

    • Salinity

    • Saturation

    • Viscosity

    • Surfactants

    • Role of organics

    Gerrit de Leeuw


    Particle parameterizations

    Particle parameterizations

    Combine various techniques

    • Parameterization whitecap cover

    • Detailed laboratory experiments on bubble mediated production

    • Eddy covariance

    • REA

    • Chemical characterization

      With a comprehensive set of oceanic and atmospheric parameters

      Use of satellites to produce global data sets

    Gerrit de Leeuw


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