Bromoform in the tropical boundary layer of the Maritime Continent during OP3
We report measurements of bromoform made by gas chromatography during the OP3 campaign in 2008. Mea- surements were made simultaneously for a few days at the World Meteorological Organization (WMO) Global Atmo- sphericWatch (GAW) site in the Danum Valley, a rainforest location in Sabah, Borneo, and at a nearby coastal site at Ku- nak. 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 10 s of ppt. Measurements of C2Cl4, an industrial tracer, showed no significant difference in back- ground at the two sites. Modelling using two different mod- els can reproduce a number of the observed features. The data are consistent with a strong, local coastal source of bro- moform in eastern Sabah and can be used to infer the strength of the source of bromoform in South East Asia. However, they provide only a very weak constraint on global emis- sions. The global model results highlight the difficulty for short-lived species of extrapolating limited duration, local measurements to a global source.