Airborne measurements of organic bromine compounds in the Pacific tropical tropopause layer

Abstract

Very short-lived brominated substances (VSLBr) are an important source of stratospheric bromine, an effective ozone destruction catalyst. However, the accurate estimation of the organic and inorganic partitioning of bromine and the input to the stratosphere remains uncertain. Here, we report near-tropopause measurements of organic brominated substances found over the tropical Pacific during the NASA Airborne Tropical Tropopause Experiment campaigns. We combine aircraft observations and a chemistry−climate model to quantify the total bromine loading injected to the stratosphere. Surprisingly, despite differences in vertical transport between the Eastern and Western Pacific, VSLBr (organic + inorganic) contribute approximately similar amounts of bromine [∼6 (4−9) parts per thousand] to the stratospheric input at the tropical tropopause. These levels of bromine cause substantial ozone depletion in the lower stratosphere, and any increases in future abundances (e.g., as a result of aquaculture) will lead to larger depletions.

BrO and inferred Br<sub><i>y</i></sub> profiles over the western Pacific: relevance of inorganic bromine sources and a Br<sub><i>y</i></sub> minimum in the aged tropical tropopause layer

“…Finally, CAM-Chem shows good agreement with the Br y from the box model in this work below 340 K and above 360 K. However, between 340 and 360 K the model predicts systematically lower Br y than inferred. Navarro et al (2015) have shown that the CAMChem VSLS are consistent with CONTRAST observations. The PGI injection of VSLS, which are important for predict- Figure 9.…”

An observationally constrained evaluation of the oxidative capacity in the tropical western Pacific troposphere

“…However, the lifetime of CH 2 Br 2 based on CONTRAST observations rises to ~200 days at 10 km and exceeds 400 days above 14 km, due to the falloff of [OH 24 HR ] (Figure ). Since convection driven by the TWP warm pool often detrains above 10 km, significant injection of CH 2 Br 2 to the lowermost stratosphere is expected, as was observed during the NASA Airborne Tropical Tropopause Experiment campaign [ Navarro et al ., ].…”

The increasing threat to stratospheric ozone from dichloromethane

“…Historically, VSLS have been thought to play a minor role in stratospheric ozone depletion due to their relatively short atmospheric lifetimes (typically <6 months) and therefore low atmospheric concentrations. However, substantial levels of both natural and anthropogenic VSLS have been detected in the lower stratosphere15161718 and numerical model simulations suggest a significant contribution of VSLS to ozone loss in this region192021. Long-term measurements of CH 2 Cl 2 reveal that its tropospheric abundance has increased rapidly in recent years15212223.…”