Bromoform in the tropical boundary layer of the Maritime Continent during OP3: the contrast between coast and rainforest
1Dept. of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, UK
2National Centre for Atmospheric Science, NCAS, UK
3Met Office, Exeter, UK
4Malaysian Meteorological Department, Ketua Stesen GAW Lembah Danum, Jabatan Meteorologi Malaysia Cawangan Sabah, Lapangan Terbang Wakuba Tawau, Peti Surat 60109, 91011 Tawau, Sabah, Malaysia
5Global Satria Life Sciences Lab, TB 12188, Taman Megajaya Phase 3, 91000 Tawau, Sabah, Malaysia
Abstract. We report measurements of bromoform made by gas chromatography during the OP3 campaign in 2008. Measurements were made simultaneously for a few days at the World Meteorological Organization (WMO) Global Atmospheric Watch (GAW) site in the Danum Valley, a rainforest location in Sabah, Borneo, and at a nearby coastal site at Kunak. Background values at Kunak were higher than those measured in the rainforest (2–5 ppt compared with 1 ppt) and excursions away from the background were very much higher, reaching 10s of ppt. Measurements of C2Cl4, an industrial tracer, showed no significant difference in background at the two sites. The data are consistent with a strong, local coastal source of bromoform in eastern Sabah. Modelling using two different models can reproduce many of the observed features. The bromoform data are consistent with a lower global source (190 Gg Br yr−1) than indicated by our recent measurements on Cape Verde (O'Brien et al., 2009) and point to the difficulty for short-lived species of extrapolating local measurements to a global source.