EU GeoMon

Duration: 2007-2011

Contact: Martin Gysel, martin.gysel@psi.ch

GEOmon stands for Global Earth Observation and Monitoring of the Atmosphere. It was funded under the European Commission's Sixth Framework Programme. The overall goal of this project was to sustain and analyse European ground-based observations of atmospheric composition, complementary to satellite measurements, in order to quantify and understand ongoing atmospheric changes.

Within this project we investigated of water uptake on the optical properties of atmospheric aerosol particles. For the comparison of ground-based measurements with remote sensing instruments like LIDAR, MAX-DOAS or satellite retrievals the accurate knowledge of RH dependence of the aerosol scattering coefficient is very important.

Intensive measurement campaign were conducted at

• Black forest, Germany [Fierz-Schmidhauser et al., 2010a]
• Jungfraujoch, Switzerland [Fierz-Schmidhauser et al., 2010b]
• Ny Alesund, Zeppelin station, Spitsbergen, Norway [Zieger et al., 2010]
• Mace Head, Ireland [Fierz-Schmidhauser et al., 2010c]
• Cabauw, The Netherlands [Zieger et al., 2011]
• Melpitz, Germany

Where the required data were available, closure studies, i.e., determination of the dependence of aerosol light scattering enhancement factor f(RH) on size distribution, chemistry (refractive index), and hygroscopic growth were performed, and sensitivity studies (expected error when dataset is not complete) were done. We found that the measured f(RH) agreed well with f(RH) calculated with a Mie model using measurements of the aerosol size distribution, chemical composition and hygroscopicity as input. The variability of the chemical composition has a dominant influence on the variability of f(RH), but also a mean size distribution is required to predict f(RH) well.

Journal Articles

Fierz-Schmidhauser, R., P. Zieger, G. Wehre, A. Jefferson, J. A. Ogren, U. Baltensperger, and E. Weingartner (2010a), Measurement of relative humidity dependent light scattering of aerosols, Atmospheric Measurement Techniques, 3, 39-50.

Fierz-Schmidhauser, R., P. Zieger, M. Gysel, L. Kammermann, P. F. DeCarlo, U. Baltensperger, and E. Weingartner (2010b), Measured and predicted aerosol light scattering enhancement factors at the high alpine site Jungfraujoch, Atmos. Chem. Phys., 10(5), 2319-2333.

Fierz-Schmidhauser, R., P. Zieger, A. Vaishya, C. Monahan, J. Bialek, C. D. O'Dowd, S. G. Jennings, U. Baltensperger, and E. Weingartner (2010c), Light scattering enhancement factors in the marine boundary layer (Mace Head, Ireland), J. Geophys. Res., 115, D20204, doi:20210.21029/22009JD013755.

Zieger, P., R. Fierz-Schmidhauser, M. Gysel, J. Strom, S. Henne, K. E. Yttri, U. Baltensperger, and E. Weingartner (2010), Effects of relative humidity on aerosol light scattering in the Arctic, Atmos. Chem. Phys., 10(8), 3875-3890.

Zieger, P., E. Weingartner, J. Henzing, M. Moerman, G. d. Leeuw, J. Mikkilä, M. Ehn, T. Petäjä, K. Clémer, M. v. Roozendael, S. Yilmaz, U. Frieß, H. Irie, T. Wagner, R. Shaiganfar, S. Beirle, A. Apituley, K. Wilson, and U. Baltensperger (2011), Comparison of ambient aerosol extinction coefficients obtained from in-situ, MAX-DOAS and LIDAR measurements at Cabauw, Atmos. Chem. Phys., 11, 2603-2624.

Thesis

Zieger, P. (2011), Effects of relative humidity on aerosol light scattering, ETH Zürich, Nr. 19659, Zürich.

Fierz-Schmidhauser, R. (2010), Enhancement of the light scattering coefficient of atmospheric aerosol particles by water uptake, ETH Zürich, Nr. 18784, Zürich.