1. The Global Atmosphere Watch Aerosol Programme
Urs Baltensperger
Laboratory of Atmospheric Chemistry Paul Scherrer Institut, CH-5232 Villigen, Switzerland
EMEP-EPA Workshop
New Orleans, USA, April, 2004

2. The Mission of GAW
Make reliable, comprehensive observations of the chemical composition and selected physical characteristics of the atmosphere on global and regional scales
Provide assessments and early warnings of atmospheric change
Predict future atmospheric states
Components: Radiation (mainly UV)       Aerosols Ozone              Precipitation chemistry Greenhouse Gases              GURME (urban environments)

3. Objective for the GAW Aerosol Programme
To determine the spatio-temporal distribution of aerosol properties related to climate forcing and air quality up to multidecadal time scales.”

4. Facilities, Bodies
The Scientific Advisory Group (Chair: Urs Baltensperger)
Still wanted: The World Calibration Centre for Aerosol Chemistry, WCCAC N.N.
The World Calibration Centre for Aerosols, Physics, WCCAP in Leipzig (Alfred Wiedensohler)
Data providers 22 Global stations 300+ Regional stations participating programmes
The World Data Centre for Aerosols, WDCA in Ispra (Julian Wilson)
Data users

5. WORLD METEOROLOGICAL ORGANIZATION
GLOBAL ATMOSPHERE WATCH’s GLOBAL NETWORK
Ny Ålesund 80 80
Alert
Point Barrow
Pallas-Sodankylä
Polar Circle
Mace Head
Zugspitze-Hohenpeissenberg 40 40
Mt Waliguan
Izana
Mauna Loa
Assekrem-Tamanrasset
Minamitorishima
Kenya
Bukit Koto Tabang
Samoa
Arembepe
Lauder
Cape Point 40 40
Amsterdam Island
Cape Grim
Ushuaia
160
120 80 40 40 80
120
160
Neumayer Station
South Pole
May 2001

6. Global regional and contributing stations
Source: GAWSIS,

7. The World Data Centre for Aerosols

8. Aerosol parameters suggested by the GAW SAG/Aerosol
Continuously: - Multiwavelength optical depth - Mass in two size fractions - Major chemical components in two size fractions - Light absorption coefficient - Light scattering scattering coefficient at various wavelengths - Hemispheric backscattering coefficient at various wavelengths - Aerosol number concentration - Cloud condensation nuclei at 0.5% supersaturation Intermittently: - Aerosol size distribution - Detailed size fractionated chemical composition - Dependence on relative humidity - CCN spectra (various supersaturations) - Vertical distribution of aerosol properties
Bold: core parameters

9. Harmonization issues
Is there a suitable instrument?
Intercomparison between instruments for the same parameter
Adaptation to ambient conditions
Integration of data (e.g. column and in situ data)

10. WMO/GAW Aerosol Measurement Procedures Guidelines and Recommenations GAW Report No can be downloaded from: (or: Google: WMO GAW -> GAW home page)

11. Data Provider Workshop I: Aerosol Optical Depth
Location, Date: Davos (Switzerland), 8-10 March 2004
Organizer: Len Barrie (WMO), Chris Wehrli (WRC), Urs Baltensperger
Sponsors: WMO/GAW, GAW-CH, WRC
Topics: - Strategies for Global Coverage and Applications - Technical Coordination for better Integration in a Global Network
Outcome: WMO Report (summer 2004)

12. Data Provider Workshop II: Aerosol in situ parameters
Location, Date: Ispra (Italy), October 2004
Organizer: Julian Wilson, Jean-Philippe Putaud, JRC Ispra
Sponsors: WMO/GAW, EU (CREATE/DAEDALUS), JRC
Goals: - bring data providers together - explore possibilities for data access between contributing partners - repeat the European Aerosol Compilation (see Putaud) on a global scale - demonstrate data usage via AEROCOM
Workshop open to any data provides, some funding available

13. The High Altitude Research Station Jungfraujoch, 3580 m asl

14. On-line access to aerosol data Example: Scattering coefficient

15. Absorption coefficient measurements with the aethalometer and the MAAP
Simultaneous scattering and absorption coefficient: identification of Saharan dust events, see Collaud et al., Atmos. Chem. Phys. Discuss. (2003)

16. Conclusions
Promising development of GAW in recent years - guide for aerosol measurements - establishment of WCCAP - first successful calibration and audit activities - agreement with EMEP on data flow harmonisation - comprehensive data sets at a couple of sites
Synergy between monitoring and research, and between different networks
Some parameters require more research
Data flow to WDCA to be enhanced
The vision: One-stop shop for data users
Highly important for ground truthing of satellite data
Capacity building a central theme

17. Thank you for your attention

18. Hygroscopic growth of the Jungfraujoch aerosol
Weingartner et al., ES&T (2002)

19. Indoor vs. ambient conditions
Nessler et al., (2003)

20. Response of scattering coefficient and particle size to hygroscopic growth
Input:
Angstrom exponent of scattering coefficient
Relative humidity
with knowledge of
size distribution (1 year)
chemical composition (ions: every 6th day, detailed chemistry: campaigns)
hygroscopic growth behavior: campaigns

21. Response of scattering coefficient and particle size to hygroscopic growth

22. Chemical composition of the Jungfraujoch aerosol
Henning et al., J. Geophys. Res. (2003)

23. Number and surface area size distributions of the Jungfraujoch aerosol; seasonal averages
Weingartner et al.,
J. Geophys. Res. (1999)

24. Setup of the Hygroscopicity Tandem DMA
Weingartner et al., ES&T (2002)