Source and product gas partitioning of VSL bromocarbons and their impact on stratospheric bromine injection

RAFAEL PEDRO FERNÁNDEZ; ROSS SALAWITCH; DOUGLAS E. KINNISON; JEAN-FRANCOISE LAMARQUE; ALFONSO SAIZ-LOPEZ

Lancaster

Workshop; Chemistry Climate Modelling Initiative (CCMI-2014); 2014

Stratosphere-Troposphere Processes and their Role in Climate (SPARC)

Before being injected to the stratosphere, very short-lived (VSL) bromocarbons produced by ocean biology, together with their degradation inorganic products, are transported to the tropical tropopause layer (TTL). The partitioning between the source gas (SG) and product gas (PG) species within the TTL will depend on the interaction of several processes such as the geographical distribution of sources, the strength of convection and the photochemical lifetime of each species. In order to determine the impact of each process on the stratospheric bromine injection due to VSL sources, we have included a state-of-the-art tropospheric and stratospheric halogen chemistry scheme into the CAM-Chem chemistry climate model. Different sensitivities studies had been performed aimed to understand the different partitioning of inorganic bromine species during day and night, the contribution of heterogeneous recycling processes over sea-salt aerosols and ice particles, the ratio R = PG/SG for each species and the efficiency of washout/ice-uptake. Our model results suggest a tropical annual average stratospheric bromine injection due to VSL sources to be 5 pptv, with the inorganic contribution (PG ~3 pptv) surpassing the carbon-bonded portion (SG ~2 pptv). During events of strong convective transport, such as the fast uplifting of the Western Pacific warm pool, the model predicts a predominant SG injection due to the shorter transport times. In those areas, large amounts of inorganic bromine produced by sea-salt recycling within the marine boundary layer are also rapidly transported to the TTL before being removed by washout, increasing the local stratospheric bromine injection to ~7.5 pptv.