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Pyle J.A.,University of Cambridge | Pyle J.A.,National Center for Atmospheric Science | Ashfold M.J.,University of Cambridge | Harris N.R.P.,University of Cambridge | And 13 more authors.
Atmospheric Chemistry and Physics | Year: 2011

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 10 s of ppt. Measurements of C2Cl4, an industrial tracer, showed no significant difference in background at the two sites. Modelling using two different models can reproduce a number of the observed features. The data are consistent with a strong, local coastal source of bromoform 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 emissions. The global model results highlight the difficulty for short-lived species of extrapolating limited duration, local measurements to a global source. © 2011 Author(s). Source


Robinson A.D.,University of Cambridge | Harris N.R.P.,University of Cambridge | Ashfold M.J.,University of Cambridge | Ashfold M.J.,University of Nottingham Malaysia Campus | And 16 more authors.
Atmospheric Chemistry and Physics | Year: 2014

Short-lived halocarbons are believed to have important sources in the tropics, where rapid vertical transport could provide a significant source to the stratosphere. In this study, quasi-continuous measurements of short-lived halocarbons are reported for two tropical sites in Sabah (Malaysian Borneo), one coastal and one inland (rainforest). We present the observations for C 2Cl4, CHBr3, CH2Br 2* (actually ∼80% CH2Br2 and ∼20% CHBrCl2) and CH3I from November 2008 to January 2010 made using our μDirac gas chromatographs with electron capture detection (GC-ECD). We focus on the first 15 months of observations, showing over one annual cycle for each compound and therefore adding significantly to the few limited-duration observational studies that have been conducted thus far in southeast Asia. The main feature in the C2Cl4 behaviour at both sites is its annual cycle, with the winter months being influenced by northerly flow with higher concentrations, typical of the Northern Hemisphere, and with the summer months influenced by southerly flow and lower concentrations representative of the Southern Hemisphere. No such clear annual cycle is seen for CHBr3, CH2Br2* or CH3I. The baseline values for CHBr3 and CH2Br2* are similar at the coastal (overall median: CHBr3 1.7 ppt, CH 2Br2* 1.4 ppt) and inland sites (CHBr3 1.6 ppt, CH2Br2* 1.1 ppt), but periods with elevated values are seen at the coast (overall 95th percentile: CHBr3 4.4 ppt, CH2Br2ast 1.9 ppt), presumably resulting from the stronger influence of coastal emissions. Overall median bromine values from [CHBr3 × 3] + [CH2Br2* × 2] are 8.0 ppt at the coast and 6.8 ppt inland. The median values reported here are largely consistent with other limited tropical data and imply that southeast Asia generally is not, as has been suggested, a hot spot for emissions of these compounds. These baseline values are consistent with the most recent emissions found for southeast Asia using the p-TOMCAT (Toulouse Off-line Model of Chemistry And Transport) model. CH3I, which is only observed at the coastal site, is the shortest-lived compound measured in this study, and the observed atmospheric variations reflect this, with high variability throughout the study period. © Author(s) 2014. Source


Pyle J.A.,National Center for Atmospheric Science | Pyle J.A.,University of Cambridge | Warwick N.J.,National Center for Atmospheric Science | Warwick N.J.,University of Cambridge | And 52 more authors.
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2011

We present results fromtheOP3 campaign in Sabah during 2008 that allowus to study the impact of localemission changes over Borneo on atmospheric composition at the regional andwider scale. OP3 constituentdata provide an important constraint onmodel performance. Treatment of boundary layer processes is highlighted as an important area of model uncertainty.Model studies of land-use change confirm earlierwork, indicating that further changes to intensive oil palm agriculture in South EastAsia, and the tropics ingeneral, could have important impacts on air quality, with the biggest factor being the concomitantchanges in NO x emissions. With the model scenarios used here, local increases in ozone of around 50per cent could occur. We also report measurements of short-lived brominated compounds aroundSabah suggesting that oceanic (and, especially, coastal) emission sources dominate locally. The concentrationof bromine in short-lived halocarbons measured at the surface during OP3 amounted to about7 ppt, setting an upper limit on the amount of these species that can reach the lower stratosphere. © 2011 The Royal Society. Source

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