SOS

Seasonal Oxidant Study

Four intensive experiments will be held at the Cape Verde Atmospheric Observatory this year in February, May, August, and November to investigate the seasonal changes in atmospheric oxidants. This is a SOLAS and NSF funded project.

In addition to the core measurements made routinely at the site the following atmospheric measurements will also be made:-

Measurement	Technique	Institute	Period of measurement
OH, HO2	FAGE	Stewart Vaughan and Trevor Ingham, University of Leeds	4 x 3 week campaigns Feb-March, May, August-September, November 2009
IO, BrO, NO3	LP-DOAS	Hilke Oetjen, University of Leeds	Continuously between Feb-Nov 2009
HO2, RO2	PERCA	Karun Arunasalam, University of Leicester	4 x 3 week campaigns Feb-March, May, August-September, November 2009
Photolysis rates	Radiometers	Michael, Roland Leigh, University of Leicester	Continuously between Feb-Nov 2009
	MAX-DOAS	Michael, Roland Leigh, University of Leicester	Continuously between Feb-Nov 2009
	Ozone Sondes	Roberto Sommariva, Roland Von Glasow, University of East Anglia	May 2009
Dihalogens, HOCl/HOBr	Mass Spectrometry	Mike Lawler, Eric Saltzman, University of California, Irvine	May 2009

The major scientific objectives are:-

Determine the seasonal cycle of OH and HO2 in the tropical Atlantic Boundary layer based on surface measurements made at the Observatory.
Perform an initial analysis of the budgets of OH, HO2, and compare to those derived from supporting trace gas data, and with other modelling studies within the SOLAS programme.
To quantify the fast photochemical budget of the oxidative chemistry in the tropical marine boundary layer using observed correlations and comparisons of measured and model-predicted behaviour.
To quantify the roles of oxygenated species on photochemistry and the radical budget in the remote marine atmosphere.
To assess the controlling features of tropical MBL reactive sink (and source) terms for ozone, methane, and oVOCs.
To investigate the spatial distribution of glyoxal over the lower layer of the atmosphere.

Aerosol Sampling during May-June Campaign
A second HV-sampler will be shipped to Sao Vicente for TSP sampling. This sampler will also probably be available for the August campaign. For the May/June campaign sampling will begin on the 18th May and will end on the 10th June. During the intensive campaign daily samples will be collected with the DIGITEL DHA-80 (PM 10 high volume 720 m³ per day) and also at the same time size segregated PM (50 nm-140nm-420nm-1.2µm-3.5µm-10µm) using the BERNER impactor. Theoretically it is possible to remove the PM10 inlet and use the sampler as a TSP sampler but this hasn't been confirmed because it is not clear how good the collection effieceny will be for coarse mode PM >10 µm.
The physical measurements are running automatically in parallel, size distribution (12 nm - 10 µm) and number concentration every 15 minutes.

Campaign dates