Chemical And Physical Structure Of The Lower Atmosphere Of The Tropical Eastern North Atlantic

Lead Research Organisation: University of York
Department Name: Chemistry


The chemical processes which occur in the lowermost atmosphere over the oceans have a profound effect on the global environment. There are many aspects of the marine atmosphere that we are yet to fully understand; particularly how the ocean and atmosphere interact with one another and which trace species are exchanged between them. It has been proposed that the release of halogen (Cl, Br, I) containing compounds from the surface ocean to the atmosphere can have a major impact on the destruction of low level ozone and the formation of fine particles, both entitles with climate forcing properties. Many of the species which may be released from the sea surface are highly reactive however and may exist in the atmosphere on timescales of the order of minutes. It is possible therefore that distinct concentration gradients may exist in the lower most atmosphere for certain compounds, and this may strongly impact on the environmental influence of such ocean - atmosphere fluxes. In this project we propose to measure the chemical profile of the remote marine boundary layer from 30 m above the sea surface upwards, and into the free troposphere as high as 4500 m. The chemical profiles will be determined in conjunction with other experiments making observations of ocean and atmospheric properties on a research vessel and at an atmospheric observatory. The chemical profiles obtained from an aircraft will subsequently place these point observations in a wider spatial context.
Description This project centered around the Cape Verde Atmospheric Observatory in the tropical Atlantic. A year-round data set of co-located surface trace gas measurements made in conjunction with low-level aircraft observations, showed that the mean daily observed ozone loss is approx 50 per cent greater than that simulated by a global chemistry model using a classical photochemistry scheme that excludes halogen chemistry. The results show that halogen chemistry has a significant and extensive influence on photochemical ozone loss in the tropical Atlantic Ocean boundary layer. The omission of halogen sources and their chemistry in atmospheric models may lead to significant errors in calculations of global ozone budgets, tropospheric oxidizing capacity and methane oxidation rates, both historically and in the future.
Exploitation Route The results of this work has lead to further funding for the Cape Verde Observatory which is now a WMO Global Atmospheric Watch Station. The data is publicly available and can be used in future global chemistry transport model parametrizations.
Sectors Environment