Constraining the Stratospheric Sulfate Budget in Global Models: Insights from in Situ OCS Measurements During 2023 SABRE and Comparison with Satellite, Balloon and Surface Data

In situ carbonyl sulfide (OCS) measurements from the Stratospheric Aerosol processes, Budget and Radiative Effects (SABRE) 2023 airborne campaign are used to evaluate the sulfate budget in the Arctic stratosphere during boreal winter. The strong correspondence between these measurements and remote retrievals from the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer provide robust validation of the satellite's capability to monitor stratospheric OCS globally. We demonstrate how trends in the tropical tropopause layer and National Oceanic and Atmospheric Administration OCS surface data reveal a post-2016 similar to 8% global decline in OCS abundance, which is absent from many global climate models. New simulations with a revised planetary boundary layer OCS abundance show improved agreement with remote retrievals and in situ data across multiple stratospheric layers, but remaining model biases highlight the need for additional in situ OCS observations. The revised representation reduces the stratospheric sulfate burden, resulting in an increased shortwave solar flux at the tropical tropopause by as much as 0.3 Wm-2 locally, with implications for stratospheric circulation, radiative forcing, and climate feedbacks.