The Tropical Ocean tRoposphere Exchange of Reactive halogen species and Oxygenated VOCs (TORERO) field campaign will deploy the NSF/NCAR Gulfstream V research aircraft over the tropical and subtropical Eastern Pacific Ocean in early 2012 to investigate the release of reactive halogen species (RHS) from biologically active coastal waters and open ocean upwelling regions (termed oxygen minimum zones, OMZs). Observations and modeling studies corroborate the global presence of RHS and oxygenated volatile organic compounds (OVOC) in the free troposphere (FT), yet important gaps remain in our understanding of remote ocean sources, and the effects on atmospheric chemistry, and potentially climate. TORERO will investigate three hypotheses: (1) OVOC and RHS released from the remote ocean impact atmospheric composition in the FT as a result of deep convective transport; (2) the ocean sources of VOC precursors, and the abundance of OVOC and halogen oxide radicals varies between open ocean areas with biologic activity, coastal upwelling and the ocean deserts, and (3) reactive gases released from the ocean are relevant to chemistry and potentially climate through ozone destruction, methane oxidation, and aerosol formation.
TORERO research will support two graduate students and a postdoctoral scholar in an environment where interaction with Hispanic culture is part of the daily routine during the field phase in Ecuador and Chile. University researchers will be provided with access to a unique aircraft facility, several unique instruments, and a network of scientists from federal laboratories (NCAR, NOAA). TORERO results will be made available for use by the scientific community. The project will benefit society by advancing understanding of ocean-atmosphere interactions to improve predictive capabilities and better prepare for climate change.
Oceans cover 70% of the Earth surface, and emissions of halogens and organic carbon species over tropical oceans modify tropospheric ozone and aerosols. However, atmospheric models remain largely untested for lack of vertically resolved measurements of bromine monoxide (BrO), iodine monoxide5 (IO), and small oxygenated hydrocarbons (e.g., glyoxal, methyl ethyl ketone, butanal) in the tropical troposphere. Such measurements are particularly relevant at tropical latitudes. About 75% of the global chemical removal of greenhouse gases like methane and ozone occurs at tropical latitudes, and climate sensitivities to changes in ozone are particularly large. Furthermore, the oxidation of atmospheric mercury is accelerated at the cold temperatures typical of the upper tropical free troposphere. The Tropical Ocean tRoposphere Exchange of Reactive halogen species and Oxygenated hydrocarbons (TORERO) project has demonstrated that bromine and iodine chemistry are active, and relevant for ozone lifetimes in the tropical free troposphere (Figure 1, Dix et al., 2013). We have measured the first vertical profiles of BrO, glyoxal, and other oxygenated VOC in the tropical free troposphere (Fig. 2, Volkamer et al., 2015). Our results suggest that the impact of halogens on tropospheric ozone and the oxidation of atmospheric mercury is currently underestimated. If the elevated BrO found in this study applies more broadly a reassessment of halogen chemistry in the UTLS is needed. Furthermore, the formation of short-lived oxygenated hydrocarbons at the air-sea interface (Figure 3, Zhou et al., 2014; Coburn et al., 2014) and in the tropical FT (Volkamer et al., 2015) is a smoking gun for other OVOC species that have significant potential to modify tropospheric HOx and NOx , O3 and aerosols. Our understanding of the chemical processes involving halogens and organic carbon species in the tropics seems incomplete.
