Constraints on the Loss of Hydroperoxymethyl Thioformate (HPMTF) to Marine Clouds Using Aircraft Observations

DMS oxidized by OH can go on to form a stable intermediate, hydroperoxymethyl thioformate (HPMTF), which is both globally ubiquitous and efficiently lost to multiphase processes in the marine atmosphere. Recent work has shown that clouds act as a significant and irreversible loss path for HPMTF, sequestering sulfur and greatly reducing the production of long-lived, climate-relevant species (e.g., SO₂ and OCS).

Until recently, there have been few observational constraints on the role of clouds in the spatiotemporal distribution of HPMTF and other soluble molecules in the MBL. Using a steady-state approximation, we determine a reactive uptake and first-order aqueous loss rate constant of HPMTF to cloud droplets of 1.2 (0.9–1.9) × 10^–2 and 1.4 (0.4–2.2) × 10^–1 s^–1, respectively. The results suggest that hydrolysis and ozonolysis are significant within cloud droplets, and their competition likely impacts the distribution of sulfate and organic acids in the marine environment.