Atmospheric sulfur cycling in the southeastern Pacific – longitudinal distribution, vertical profile, and diel variability observed during VOCALS-REx

摘要: Abstract. Dimethylsulfide (DMS) emitted from the ocean is a biogenic precursor gas for sulfur dioxide (SO 2 ) and non-sea-salt sulfate aerosols 4 2− ). During VAMOS-Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) in 2008, multiple instrumented platforms were deployed Southeastern Pacific (SEP) off coast of Chile Peru to study linkage between stratocumulus clouds. We present here observations NOAA Ship Ronald H. Brown NSF/NCAR C-130 aircraft along ~20° S (70° W) remote marine atmosphere (85° W). While SO concentrations distinctly elevated above background levels coastal boundary layer (MBL) due anthropogenic influence (~800 80 pptv, respectively), their rapidly decreased west 78° W (~100 25 pptv). In region, entrainment free troposphere (FT) increased MBL burden at rate 0.05 ± 0.02 μmoles m −2 day −1 diluted 0.5 0.3 , while sea-to-air DMS flux (3.8 0.4 remained predominant source mass MBL. In-cloud oxidation was found be most important mechanism removal situ production. Surface concentration displayed pronounced diel variability, increasing first few hours after sunset decaying rest day. theorize that increase nighttime recoupling mixed down cloud-processed air, decoupling sporadic precipitation scavenging responsible daytime decline .