Global Atmosphere Watch

The World Data Centre for Aerosols

The World Data Centre for Aerosols (WDCA) operated by the European Union's Joint Research Centre, Ispra, Italy, has recently moved to the Norwegian Institute for Air Research. It is established to archive aerosol related observations made under GAW. A wide variety of aerosol parameters have been recommended by the GAW Scientific Advisory Group for Aerosols as suitable for measurement and archiving at GAW Regional and Global stations.

Recommended aerosol parameters for frequent measurement at Regional stations:

• Multiwavelength aerosol optical depth.
  
• Mass, preferably in two size fractions (either 10 micron ambient and 1 micron dry, or 10 micron ambient and 2.5 micron ambient).
  
• Major chemical components in the above two size fractions.
  
• Light scattering coefficient (Nephelometry).
  

Additional aerosol parameters recommended for frequent measurement at Global stations:

• Scattering and hemispheric backscattering at various (3 or 4) wavelengths.
  
• Aerosol number concentration.
  
• Cloud condensation nuclei at 0.5% supersaturation.
  
• Diffuse, global and direct solar radiation. (These measurements are archived at WRDC)
  

Parameters for intermittent measurement:

• Aerosol size distribution.
  
• Detailed size fractionated chemical composition
  
• Size dependence on relative humidity
  
• CCN spectra at various supersaturations.
  
• Vertical distributions of aerosol properties.
  

Clearly, few stations can make all of these measurements, while many stations are making only one or two of these observations. At the moment, WDCA is concentrating on building up the archives of commonly available parameters, including chemical composition, aerosol optical properties, and CN concentrations

• GAWNET

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