Articles | Volume 6, issue 3
Atmos. Meas. Tech., 6, 661–675, 2013
Atmos. Meas. Tech., 6, 661–675, 2013

Research article 13 Mar 2013

Research article | 13 Mar 2013

Linearisation of the effects of spectral shift and stretch in DOAS analysis

S. Beirle1, H. Sihler1,2, and T. Wagner1 S. Beirle et al.
  • 1Max-Planck-Institut für Chemie, Mainz, Germany
  • 2Institut für Umweltphysik, Universität Heidelberg, Heidelberg, Germany

Abstract. Differential Optical Absorption Spectroscopy (DOAS) is a widely used method to quantify atmospheric trace gases from spectroscopic measurements. While DOAS can, in principal, be described by a linear equation system, usually nonlinearities occur, in particular as a consequence of spectral misalignments.

Here we propose to linearise the effects of a spectral shift by including a "shift spectrum", which is the first term of a Taylor expansion, as pseudo-absorber in the DOAS fit. The effects of a spectral stretch are considered as additional wavelength-dependent shifts.

Solving the DOAS equation system linearly has several advantages: the solution is unique, the algorithm is robust, and it is very fast. The latter might be particularly important for measurements with high data rates, like for upcoming satellite missions.