Stratospheric Bromine: Budget and partitioning from balloon-borne observations with the multi-instrument remote sensing payload MIPAS-B/TELIS/mini-DOAS

Abstract

Bromine-containing substances can decompose the ozone layer. Although the abundance of stratospheric bromine is by about two orders of magnitude smaller than that of the better-known ozone-depleting chlorine, its effect on the ozone layer is comparably hazardous. Moreover, against the background of abating levels of chlorine in the stratosphere, bromine will become more and more important due to its less regulated emissions and natural sources. The two major inorganic bromine species in the lower stratosphere are bromine oxide (BrO) and bromine nitrate (BrONO2) - the relative abundances of which are mainly controlled by fast photochemical processes. While BrO has first been observed around 20 years ago, BrONO2 has been detected by satellite limb observations in the mid-infrared spectral region only recently (in 2008). Dedicated to the simultaneous observation of BrO and BrONO2 including their diurnal variability, a balloon flight took place from Timmins (49 °N, Canada) in September 2014. The paylaod consisted of three spectrometers covering the UV-VIS, the mid-infrared and the sub-mm/microwave spectral region. These instruments complement each other ideally in measuring stratospheric substances: The MIPAS-B infra-red spectrometer of the KIT Institute of Meteorology and Climate, the far-infrared/sub-mm spectrometer TELIS of the German Aerospace Center (DLR), and the UV/vis spectrometer mini-DOAS of Heidelberg University. The remote sensing method allows for the two- and three-dimensional daytime-dependent continuous measurement of trace gases. In this way, photochemical reactions of the species involved can be studied, which is an important prerequisite for improving chemistry and climate models. The campaign was embedded in an international balloon campaign under cooperation between the French and Canadian Space Agencies CNES and CSA. The talk will outline scientific motivation, payload and measurement strategy; after that it will present results in terms of time- and height-dependent distributions of BrO and BrONO2 along with species closely linked to the bromine chemistry such as NO2 together with a comprehensive error estimation and retrieval diagnostics. Results from the balloon measurements will be put in perspective to previous observations and to 3-dimensional model calculations.