Doctoral thesis defense

The last April 25th , 2014 in the Izaña Atmospheric Observatory, Eliezer Sepúlveda Hernández from the Izaña Atmospheric Research Center (IARC), belonging to the State Agency of Meteorology (AEMET), and doctoral student from La Laguna University (ULL) has defended his doctoral thesis entitled “Ground-based Remote Sensing for the Detection of Greenhouse Gases by Fourier Transform InfraRed Spectrometry: Optimization of Retrieval Strategies and its Validation”. The thesis has been developed at the Izaña Atmospheric Research Center (IARC) and has been supervised by Dr. Matthias Schneider (Karlsruhe Institute of Technology, KIT, Germany) and Dr. Juan Carlos Guerra García (ULL). This thesis has been supported by the FPU grant award by the Spanish Ministry of Education, Culture and Sport. This thesis has been submitted by compendium of publications and has obtained the “International Mention”.

The referees for the thesis defense have been the doctors: Inocencio Rafael Martín Benenzuela (ULL), Michel Grutter de La Mora (Universidad Nacional Autónoma de México) y André Butz (KIT). The thesis has obtained the maximum qualification “Sobresaliente, Cum Laude”.

Referees, supervisors and doctoral student at the Izaña Atmospheric Observatory.

The thesis work is based on the high-quality ground-based remote sensing Fourier Transform InfraRed spectrometer for the inversion of precise total column amounts and vertical profiles of different atmospheric trace gases. The thesis is focused on the optimization of the retrieval strategies for the greenhouse gases water vapour and methane. For this purpose the inversion code PROFFIT is applied. The vertical distribution of water vapour and tropospheric methane as derived from our remote sensing measurements are compared against very precise in-situ measurements. Thus, the quality of our retrieved products are documented. The first article presented in this dissertation, Schneider et al. [1], shows for the first time the capability of the international network TCCON (Total Carbon Column Observing Network) to derive the vertical distribution of tropospheric water vapour (the lower and the middle/upper troposphere can be distinguished). The second article, Sepúlveda et al. [2], presents a novel strategy for the inversion of tropospheric methane independent on the stratospheric methane contribution. This study applies NDACC (Network for the Detection of Atmospheric Composition Change) spectra for the subtropical site of Izaña. The third article, Sepúlveda et al. [3], extends the previous study to a set of nine globally distributed NDACC sites from the Arctic to the Antarctic, and thus under different contrasting atmospheric conditions. We introduced an aposteriori correction that further reduces the stratospheric methane variations (especially important for polar sites). This study demonstrates the feasibility of our proposed inversion strategy.

References:

[1] M. Schneider, E. Sepúlveda, O. García, F. Hase, and T. Blumenstock. Remote sensing of water vapour profiles in the framework of the Total Carbon Column Observing Network (TCCON). Atmos. Mes. Tech., 3:1785–1795, 2010.

[2] E. Sepúlveda, M. Schneider, F. Hase, O. E. García, A. Gómez-Peláez, S. Dohe, T. Blumenstock, and J. C. Guerra. Long-term validation of total and tropospheric column-averaged CH4 mole fractions obtained by mid-infrared ground-based FTIR spectrometry. Atmos. Mes. Tech., 5:1425–1441, 2012.

[3] E. Sepúlveda, M. Schneider, F. Hase, S. Barthlott, D. Dubravica, O. E. García, A. Gómez-Peláez, Y. González, J. C. Guerra, M. Gisi, R. Kohlhepp, S. Dohe, T. Blumenstock, K. Strong, D. Weaver, M. Palm, A. Sadeghi, N. M. Deutscher, T. Warneke, J. Notholt, N. Jones, D. W. T. Griffith, D. Smale, G. W. Brailsford, J. Robinson, F. Meinhardt, M. Steinbacher, T. Aalto, and D. Worthy. Tropospheric CH4 signals as observed by NDACC FTIR at globally distributed sites and comparison to GAW surface in-situ measurements. Atmos. Mes. Tech. Disc., 7:633–701, 2014.