10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
One Year Vertically Resolved Optical Closure Study of Aerosol Properties at a Meteorological Tower in Western Europe
Julia Perim Faria, ULRICH BUNDKE, Sebastian H. Schmitt, Thomas F. Mentel, Timothy Onasch, Andrew Freedman, Astrid Kiendler-Scharr, Andreas Petzold, Forschungszentrum Jülich
Abstract Number: 701 Working Group: Remote/Regional Atmospheric Aerosol
Abstract The way airborne aerosols impact climate, either by scattering light or by absorbing it, is well known and documented. The overall effect on the radiation budget depends on three main aerosol characteristics: optical depth, single scattering albedo and backscatter fraction (Haywood and Shine, 1995). Although the aerosol and light interaction mechanism is well understood, the quantification of the fore mentioned impact still presents major uncertainties.
In 2015 a new technology was introduced for measuring single-scattering albedo using a single equipment, the Cavity Attenuated Phase Shift Single Scattering Albedo Monitor (CAPS PMssa), developed by Aerodyne Inc. (Onasch et al., 2015). The instrument, operated in the red spectrum (630nm) has been previously assessed in a multi-instrument optical closure study in the laboratory using controlled particle generation systems and known particle compositions (Faria et al., 2016). The results obtained showed an excellent agreement with proven technology for both absorption and scattering measurement.
Following the laboratory study, the instrument set-up was taken, to a filed campaign, in August 2016, where it sampled ambient air from three different heights, 10, 50, and 120m through sampling lines strategically installed at a meteorological tower located in Jülich, Germany. The instruments used in this campaign are:
• CAPS PMSSA (Aerodyne): Extinction and Scattering Coefficient (630 nm) • CAPS PMSSA (Aerodyne): Extinction and Scattering Coefficient (450 nm) • Aurora 4000 (EcoTech): Scattering Coefficient (635, 525 and 450nm) • PSAP (Radiance Research): Absorption Coefficient (660, 530 and 467nm) • TAP (Brechtel): Absorption Coefficient (652, 528 and 467nm) • CPC (GRIMM): Particle Number • OPC (GRIMM): Particle Size Distribution (655nm) • AMS (Aerodyne): Chemical Composition.
As the results obtained for the laboratory study, the multi-instrumental optical closure study result during the long term ambient air measuring campaign also showed a good agreement. A few differences were spotted and have been deeper studied, as the Ångstrom exponent from the TAP and PSAP instruments. Regarding the CAPS PMSSA, we have observed that the scattering channel is not stable enough for a long term deployment and needs to be improved.
The chemical information was also analysed by using the data acquired by the AMS system and by the study of the Ångstrom exponent obtained from the multi-wavelength instruments.
The results obtained over the 1 years monitoring campaign have shown many interesting aspects such as the atmospheric aerosol stratification over specific meteorological conditions. It was also possible to observe seasonal trends on aerosol characteristics, such as optical and chemical parameters, size, and load, including vertical distribution.
A few interesting punctual cases were selected to be studied, as the forest fires that occurred in the Iberian Peninsula in October 2017. During week 42, higher extinction, scattering and absorption coefficients were observed. The absorption Ångstrom Exponent average was reduced from 1.52 ± 0.1647, the period before and after week 42, to 1.47 ± 0.1158 during fire period, as expected. This has also been detected and measured by the remote sensing station located in Jülich (JOYCE - Jülich Observatory for Cloud Evolution, Löhnert et al. (2015)).
References 1. Haywood, J. and Shine K. (1995) Geophysical Research Letters, 22:5, 603-606. 2. Onasch, T., et al. (2015) Aerosol Sci. Technol., 49:4, 267-279. 3. Faria, J.P., et al. (2016) 2016 European Aerosol Conf.. 4. Löhnert, U., et al. (2015) American Meteorological Society, 96:7, 1157-1174.