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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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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

slide6

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

slide13

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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