Tropospheric CH4 signals as observed by NDACC FTIR at globally distributed sites and comparison to GAW surface in situ measurements

Authors

E Sepulveda, University of La Laguna
Matthias Schneider, Karlsruhe Institute of Technology
Frank Hase, Karlsruhe Institute of Technology
Sabine Barthlott, Karlsruhe Institute of Technology
D Dubravica, Karlsruhe Institute of Technology
Omar Garcia, Izana Atmospheric Research Centre
A Gomez-Pelaez, Meteorological State Agency of Spain
Y Gonzalez, Izana Atmospheric Research Centre (IARC)Follow
J C. Guerra, University of La Laguna
M Gisi, IMK-A-SF, Karlsruhe Institute of Technology
R Kohlhepp, Institute for Meteorology and Climate Research
Susanne Dohe, Karlsruhe Institute of Technology
Thomas Blumenstock, Karlsruhe Institute of Technology
Kimberly Strong, University of Toronto
D Weaver, University of Toronto
M Palm, University of Bremen
A Sadeghi, University of Bremen
Nicholas Deutscher, University of WollongongFollow
Thorsten Warneke, University of Bremen
Justus Notholt, University of Bremen
Nicholas Jones, University of WollongongFollow
D W. T Griffith, University of WollongongFollow
D Smale, National Institute of Water and Atmospheric Research, New Zealand
G W. Brailsford, National Institute of Water and Atmospheric Research, New Zealand
John Robinson, National Institute of Water and Atmospheric Research, New Zealand
F Meinhardt, Federal Environmental Agency Germany
M Steinbacher, Swiss Federal Laboratories for Materials Science and Technology
T Aalto, Finnish Meteorological Institute
D Worthy, Environment Canada

RIS ID

87751

Publication Details

Sepulveda, E., Schneider, M., Hase, F., Barthlott, S., Dubravica, D., Garcia, O. E., Gomez-Pelaez, A., Gonzalez, Y., Guerra, J. C., Gisi, M., Kohlhepp, R., Dohe, S., Blumenstock, T., Strong, K., Weaver, D., Palm, M., Sadeghi, A., Deutscher, N. M., Warneke, T., Notholt, J., Jones, N., Griffith, D. W. T., Smale, D., Brailsford, G. W., Robinson, J., Meinhardt, F., Steinbacher, M., Aalto, T. & Worthy, D. (2014). Tropospheric CH4 signals as observed by NDACC FTIR at globally distributed sites and comparison to GAW surface in situ measurements. Atmospheric Measurement Techniques, 7 (7), 2337-2360.

Abstract

We present lower/middle tropospheric column-averaged CH4 mole fraction time series measured by nine globally distributed ground-based FTIR (Fourier transform infrared) remote sensing experiments of the Network for the Detection of Atmospheric Composition Change (NDACC). We show that these data are well representative of the tropospheric regional-scale CH4 signal, largely independent of the local surface small-scale signals, and only weakly dependent on upper tropospheric/lower stratospheric (UTLS) CH4 variations. In order to achieve the weak dependency on the UTLS, we use an a posteriori correction method. We estimate a typical precision for daily mean values of about 0.5% and a systematic error of about 2.5%. The theoretical assessments are complemented by an extensive empirical study. For this purpose, we use surface in situ CH4 measurements made within the Global Atmosphere Watch (GAW) network and compare them to the remote sensing data. We briefly discuss different filter methods for removing the local small-scale signals from the surface in situ data sets in order to obtain the in situ regional-scale signals. We find good agreement between the filtered in situ and the remote sensing data. The agreement is consistent for a variety of timescales that are interesting for CH4 source/sink research: day-to-day, monthly, and inter-annual. The comparison study confirms our theoretical estimations and proves that the NDACC FTIR measurements can provide valuable data for investigating the cycle of CH4.