The North Atlantic Marine Boundary Layer Experiment(NAMBLEX). Overview of the campaign held at Mace Head, Ireland, in summer 2002

Abstract

Abstract. The North Atlantic Marine Boundary Layer Experiment (NAMBLEX), involving over 50 scientists from 12 institutions, took place at Mace Head, Ireland (53.32 • N, 9.90 • W), between 23 July and 4 September 2002. A wide range of state-of-the-art instrumentation enabled detailed measurements of the boundary layer structure and atmospheric composition in the gas and aerosol phase to be made, providing one of the most comprehensive in situ studies of Correspondence to: D. E. Heard (dwayneh@chem.leeds.ac.uk) the marine boundary layer to date. This overview paper describes the aims of the NAMBLEX project in the context of previous field campaigns in the Marine Boundary Layer (MBL), the overall layout of the site, a summary of the instrumentation deployed, the temporal coverage of the measurement data, and the numerical models used to interpret the field data. Measurements of some trace species were made for the first time during the campaign, which was characterised by predominantly clean air of marine origin, but more polluted air with higher levels of NO x originating from continental regions was also experienced. ThisPublished by Copernicus GmbH on behalf of the European Geosciences Union. paper provides a summary of the meteorological measurements and Planetary Boundary Layer (PBL) structure measurements, presents time series of some of the longer-lived trace species (O 3 , CO, H 2 , DMS, CH 4 , NMHC, NO x , NO y , PAN) and summarises measurements of other species that are described in more detail in other papers within this special issue, namely oxygenated VOCs, HCHO, peroxides, organohalogenated species, a range of shorter lived halogen species (I 2 , OIO, IO, BrO), NO 3 radicals, photolysis frequencies, the free radicals OH, HO 2 and (HO 2 + RO 2 ), as well as a summary of the aerosol measurements. NAMBLEX was supported by measurements made in the vicinity of Mace Head using the NERC Dornier-228 aircraft. Using ECMWF windfields, calculations were made of the air-mass trajectories arriving at Mace Head during NAMBLEX, and were analysed together with both meteorological and trace-gas measurements. In this paper a chemical climatology for the duration of the campaign is presented to interpret the distribution of air-mass origins and emission sources, and to provide a convenient framework of air-mass classification that is used by other papers in this issue for the interpretation of observed variability in levels of trace gases and aerosols.

Measurements and modelling of molecular iodine emissions, transport and photodestruction in the coastal region around Roscoff

“…However, the semi-polluted NO x regime at Roscoff is, as noted by Mahajan et al (2009), rather different from that for previous I 2 measurements at cleaner background sites, most notably at the Mace Head Atmospheric Research Station (Galway, Ireland) where typical NO 2 concentrations (Heard et al, 2006) are below the minimum NO 2 levels observed during RHaMBLe and thus little recycling of I 2 via IONO 2 chemistry is expected.…”

“…The BBCRDS system used for this study is based on an instrument previously used to measure I 2 at Mace Head (Ireland) during the 2002 NAMBLEX campaign Heard et al, 2006) as described in detail by Bitter et al (2005). In the intervening years, the instrument's performance has been enhanced significantly by upgrading several key components, notably a new laser system that yields pulsed broadband light with a factor of two wider bandwidth at green wavelengths, a new clocked CCD camera and improved analysis software/spectral fitting routines.…”

Iodine monoxide at a clean marine coastal site: observations of high frequency variations and inhomogeneous distributions

“…1). The research station has been the subject of extensive halogen studies in the past (e.g., Alicke et al, 1999;Saiz-Lopez et al, 2006a) and is described extensively in Heard et al (2006).…”

Atmospheric Conditions during the Arctic Clouds in Summer Experiment (ACSE): Contrasting Open Water and Sea Ice Surfaces during Melt and Freeze-Up Seasons

“…3h) peaks at lower values compared to the other classes. A near-surface RH w around 85% is typical for marine boundary layers (e.g., Heard et al 2006), resulting from a balance between the surface flux over open water, precipitation, and entrainment of dry air near PBL top.…”