Detecting Multi-decadal Changes in the Brewer-Dobson Circulation from In-situ Trace Gas Measurements and Idealized Modeling

E. Ray¹, F.L. Moore^2,3, B.D. Hall³, E.J. Hintsa^2,3, G.S. Dutton^2,3, H. Garny⁴, S.C. Wofsy⁵, J. Pittman⁶, B. Daube⁶, B. Baier³, J. Li^2,3, C. Sweeney³, J. Elkins³ and A.E. Andrews³

¹NOAA Chemical Sciences Laboratory (CSL), Boulder, CO 80305; 303-579-2958, E-mail: eric.ray@noaa.gov
²Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO 80309
³NOAA Global Monitoring Laboratory (GML), Boulder, CO 80305
⁴German Aerospace Center (DLR), Institute of Atmospheric Physics, Oberpfaffenhofen-Wessling, Germany
⁵Harvard University, School of Engineering and Applied Sciences, Cambridge, MA 02138
⁶Harvard University, Cambridge, MA 02138

We utilize in situ stratospheric measurements of trace gases from two recent high altitude aircraft campaigns, DCOTTS and SABRE, as well as from StratoCore to compare mean ages and long-lived trace gas relationships in the NH stratosphere to those from ER-2 and balloon campaigns in the 1990s.  The ER-2 and balloon data from nearly three decades ago have been a primary reference for in situ-based estimates of mean age in the lower stratosphere, but very few measurements have been made in this region since then.  We use an updated technique to consistently calculate mean ages from simultaneous in situ measurements of SF₆, CO₂, N₂O and CH₄, allowing us to compare mean ages and their relationship with N₂O between the 1990s and 2020s.  The mesospheric loss of SF₆ and subsequent old age biases are largely accounted for based on newly developed theory and modeling work.  We then use an idealized model of the stratosphere to explore Brewer-Dobson circulation changes that are consistent with the observations.

Figure 1. Mean age vs. normalized N₂O based on in situ measurements from aircraft and balloon platforms in the 1990s and the 2020s.  The mean ages are based on a new optimization technique using simultaneous measurements of SF₆, CO₂ and CH₄.