Observing Trace Gases in Arctic and Subarctic Stratosphere by TELIS
Xu, Jian; Schreier, Franz; Doicu, Adrian; Vogt, Peter; Birk, Manfred; Wagner, Georg; Trautmann, Thomas
The Terahertz and submillimeter Limb Sounder (TELIS) is a balloon-borne cryogenic heterodyne spectrometer developed by a consortium of European institutes, which was mounted together with the Michelson Interferometer for Passive Atmospheric Sounding - Balloon (MIPAS-B) and the mini- Differential Optical Absorption Spectroscopy (mini-DOAS) instruments on a stratospheric gondola platform. The TELIS instrument is designed to monitor the vertical distribution of stratospheric state parameters associated with ozone destruction and climate change in Arctic and subarctic areas. The broad spectral coverage of TELIS is achieved by utilizing three frequency channels: a tunable 1.8 THz channel based on a solid state local oscillator and a hot electron bolometer as mixer, a 480-650 GHz channel with the Superconducting Integrated Receiver (SIR) technology, and a highly compact 500 GHz channel developed by the German Aerospace Center (DLR), the Netherlands Institute for Space Research (SRON), and the Rutherford Appleton Laboratory (RAL), respectively. Furthermore, an extended spectral range is observed by the combination of TELIS and MIPAS-B, which can be employed for cross validation of several gas concentrations. Between 2009 and 2011 three successful scientific flights have been launched in Kiruna, Sweden and all relevant atmospheric gas species were measured by TELIS over an altitude range of 10-32.5 km.
For estimation of concentration profiles from TELIS measurements, a constrained nonlinear least squares fitting code has been developed. In this work we present recent retrieval results from latest calibrated spectra during these three flights. Emphasis is placed on O3, CO, and HCl, and error issues pertaining to the main instrumental uncertainty terms including nonlinearity in the calibration procedure, sideband ratio and pointing offset are investigated. The retrieved profiles are validated against other limb sounding instruments, e.g., the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES), the Microwave Limb Sounder (MLS), and MIPAS-B.