Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 4171-4189, 2016
https://doi.org/10.5194/acp-16-4171-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
31 Mar 2016
Diurnal cycle and multi-decadal trend of formaldehyde in the remote atmosphere near 46° N
Bruno Franco1, Eloise A. Marais2, Benoît Bovy1, Whitney Bader1, Bernard Lejeune1, Ginette Roland1, Christian Servais1, and Emmanuel Mahieu1 1Institute of Astrophysics and Geophysics, University of Liège, Liège, Belgium
2School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
Abstract. Only very few long-term records of formaldehyde (HCHO) exist that are suitable for trend analysis. Furthermore, many uncertainties remain as to its diurnal cycle, representing a large short-term variability superimposed on seasonal and inter-annual variations that should be accounted for when comparing ground-based observations to, e.g., model results. In this study, we derive a multi-decadal time series (January 1988–June 2015) of HCHO total columns from ground-based high-resolution Fourier transform infrared (FTIR) solar spectra recorded at the high-altitude station of Jungfraujoch (Swiss Alps, 46.5° N, 8.0° E, 3580 m a. s. l. ), allowing for the characterization of the mid-latitudinal atmosphere for background conditions. First we investigate the HCHO diurnal variation, peaking around noontime and mainly driven by the intra-day insolation modulation and methane (CH4) oxidation. We also characterize quantitatively the diurnal cycles by adjusting a parametric model to the observations, which links the daytime to the HCHO columns according to the monthly intra-day regimes. It is then employed to scale all the individual FTIR measurements on a given daytime in order to remove the effect of the intra-day modulation for improving the trend determination and the comparison with HCHO columns simulated by the state-of-the-art GEOS-Chem v9-02 chemical transport model. Such a parametric model will be useful to scale the Jungfraujoch HCHO columns on satellite overpass times in the framework of future calibration/validation efforts of space-borne sensors. GEOS-Chem sensitivity tests suggest then that the seasonal and inter-annual HCHO column variations above Jungfraujoch are predominantly led by the atmospheric CH4 oxidation, with a maximum contribution of 25 % from the anthropogenic non-methane volatile organic compound precursors during wintertime. Finally, trend analysis of the so-scaled 27-year FTIR time series reveals a long-term evolution of the HCHO columns in the remote troposphere to be related to the atmospheric CH4 fluctuations and the short-term OH variability: +2.9 % year−1 between 1988 and 1995, −3.7 % year−1 over 1996–2002 and +0.8 % year−1 from 2003 onwards.

Citation: Franco, B., Marais, E. A., Bovy, B., Bader, W., Lejeune, B., Roland, G., Servais, C., and Mahieu, E.: Diurnal cycle and multi-decadal trend of formaldehyde in the remote atmosphere near 46° N, Atmos. Chem. Phys., 16, 4171-4189, https://doi.org/10.5194/acp-16-4171-2016, 2016.
Publications Copernicus
Download
Short summary
The long-term evolution of HCHO in the remote troposphere is characterized using a 27-year time series of total columns from high-resolution FTIR solar spectra recorded at Jungfraujoch. A parametric model is used to remove the effect of the HCHO diurnal variations for improving the trend determination and the comparison with columns simulated by GEOS-Chem. Sensitivity tests are performed to identify the main drivers of the HCHO seasonal and inter-annual variations, as well as their contribution.
The long-term evolution of HCHO in the remote troposphere is characterized using a 27-year time...
Share