Project Details
Projekt
Probing the lower and middle stratosphere for total bromine and iodine
Subject Area
Atmospheric Science
Term
since 2021
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 490946853
The present project aims at determining the total amount of bromine (Bry) and iodine (Iy) in the lower and middle stratosphere. Continued observations of stratospheric Bry are necessary since bromine mediates about 30% of the stratospheric ozone loss, but directmeasurements of Bry have not been performed in the middle stratosphere since 2011. Moreover, our recent airborne measurements (from the NASA Global Hawk and the HALO research aircraft) of Bry in the tropical tropopause layer (TTL), extra-tropical and polar upper troposphere and lowermost stratosphere (UT/LS) indicate 2-3 ppt larger Bry than expected for today’s middle stratosphere. This expectation is based on the trend of long-lived (the halons), medium long-lived (CH3Br), and the very short-lived brominated substances (VSLS) and their inorganic products. The reason for this gap is presently not clear. Our goal is to extend the record of Bry measurements in the lower and middle stratosphere and to assess the respective trends. In particular, we want to evaluate whether the elevated Bry measured in the TTL is compatible with the recent trend in the stratosphere and what the reasons for potential discrepancies are. For Iy, our previous observations indicate that its concentrations are undetectably low but the last assessment dates back a decade. There is some renewed interest in stratospheric iodine, since the formation of higher iodine oxides has been suggested to significantly change the lower stratospheric iodine partitioning. Here, with little additional effort, we propose to assess the stratospheric Iy burden (or the respective upper limit). The measurements will be performed from a stratospheric balloon gondola (ceiling altitude 30-35 km) using established spectroscopic techniques operated in solar occultation geometry. Two balloon flights are scheduled for summer 2021 from Kiruna, Sweden, and for summer 2022 from Timmins, Canada. The ballooning operations are conducted within the framework of the EU infrastructure HEMERA.
DFG Programme
Research Grants
