Abstract
Abstract. This special section of Atmospheric Chemistry and Physics gives an overview of scientific results, collected during a West Pacific ship expedition in October 2009 with the Research Vessel (R/V) Sonne. The cruise focussed on chemical interactions between the ocean surface and the atmosphere above the tropical West Pacific and was planned within the national research project TransBrom (www.geomar.de/~transbrom). TransBrom aimed to particularly investigate very short lived bromine compounds in the ocean and their transport to and relevance for the stratosphere. For this purpose, chemical and biological parameters were analysed in the ocean and in the atmosphere, accompanied by a high frequency of meteorological measurements, to derive new insights into the multidisciplinary research field. This introduction paper presents the scientific goals and the meteorological and oceanographic background. The main research findings of the TransBrom Sonne expedition are highlighted.
Highlights
The ship cruise comprised a meridional cross-section through the tropical West Pacific from the northern midlatitudes to the southern subtropics
The tropical West Pacific was chosen, because of the following scientific reasons: (1) the tropical West Pacific is thought to be an active source region for natural halocarbons (Yokouchi et al, 1999; Quack and Wallace, 2003; Butler et al, 2007); (2) only few marine halocarbon measurements exist in this ocean basin until now; (3) the atmosphere over the tropical West Pacific is convectively active throughout the year (Gettelman et al, 2002; Liu et al, 2007), enclosing the main gate in the “Tropical Tropopause Layer” (TTL) for trace gases entering the stratosphere (Bonazzola and Haynes, 2004; Fueglistaler et al, 2005; Krüger et al, 2008; Montzka et al, 2011)
During October 2009 the tropical convection and precipitation were enhanced over the central part of the tropical West Pacific, which is typical for a strengthening El Niño (Climate Diagnostics Bulletin, 2009)
Summary
The ship cruise comprised a meridional cross-section through the tropical West Pacific from the northern midlatitudes to the southern subtropics. Regular sea water and air sampling were carried out to analyse halocarbon distributions and sources, including different phytoplankton species (Quack et al, 2011) From these measurements halocarbon fluxes were derived for bromoform, dibromomethane and methyl iodide. The following acronyms stands for: GC-MS (Gas Chromatography-Mass Spectrometry), FPD (Flame Photometric Detector), ECD (Electron Capture Detector), FID (Flame Ionization Detector), HPLC (High Pressure Liquid Chromatography), PSICAM (Point-Source Integrating-Cavity Absorption Meter), FRRF (Fast Repetition Rate Fluorometer), RAMSES (Hyper spectral radiometer), NDIR (Non-Dispersive Infrared Detector), CFIR (Continuous Flow Isotopic Ratio), MAX-DOAS (Multi-Axis Differential Optical Absorption Spectroscopy), FTIR (Fourier Transform Infrared Spectroscopy), RSMAS (Rosenstiel School of Marine and Atmospheric Science), GUF (Goethe University Frankfurt), IMAU (Institute for Marine and Atmospheric research Utrecht), Univ HD (University Heidelberg), Univ B (University Bremen), UEA, (University of East Anglia), NUI (National University of Ireland), JC Univ (James Cook University). The 3D-Var analysis of the operational National Centre for Environmental Prediction – Global Data Assimilation System (NCEP-GDAS) is based on T382/L64 (∼ 35 km) resolution (NCEP Technical Procedures Bulletin, 2005), used with an average grid of 1◦ × 1◦ and 6-hourly data output
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