Remote Sensing of Stratospheric Trace Gases by TELIS

Abstract

TELIS (TErahertz and submillimeter LImb Sounder) is a balloon-borne cryogenic heterodyne spectrometer with two far infrared and submillimeter channels (1.8 THz and 480--650 GHz developed by DLR and SRON, respectively). The instrument was designed to investigate atmospheric chemistry and dynamics with a focus on the stratosphere. TELIS participated in three scientific campaigns in Kiruna, Sweden between 2009 and 2011. The recent campaign took place in 2014 over Ontario, Canada. During previous campaigns, TELIS shared a balloon gondola with MIPAS-B and mini-DOAS. The primary scientific goal of these campaigns has been to monitor the time-dependent chemistry of chlorine and bromine, and to achieve the closure of chemical families inside the polar vortex. In this work, we present retrieved profiles of ozone (O3), hydrogen chlorine (HCl), carbon monoxide (CO), and hydroxyl radical (OH) obtained by the 1.8 THz channel from the polar winter flights during 2009--2011. Furthermore, the corresponding retrieval algorithm is described. The quality of the retrieval products is analyzed in a quantitative manner including: error characterization, internal comparisons of the two different channels, and external comparisons with coincident spaceborne observations. The errors due to the instrument parameters and pressure dominate in the upper troposphere and lower stratosphere, while the errors at higher altitudes are mainly due to the spectroscopic parameters and the radiometric calibration. The comparisons with other limb sounders help us to assess the measurement capabilities of TELIS, thereby establishing the instrument as a valuable tool to study the chemical interactions in the stratosphere.