Seasonal Oxidant Observations in the Tropical North Atlantic Atmosphere

Lead Research Organisation: University of York
Department Name: Chemistry


The tropical marine boundary layer acts as an engine room for the self cleansing of the Earths atmosphere, - a result of high solar radiation and an abundance of water vapour and ozone. It is in these regions that the effects of certain greenhouse gases may be acutely influenced, since the oxidation chemistry occurring is potent in controlling the lifetime and hence future concentrations of gases such as methane and ozone. Atmospheric observations in tropical regions are however sparse and for the dominant atmospheric oxidant OH almost non-existent. A measurement of OH alone however is of only limited use, - the key to improving and testing our understanding is to subsequently compare those concentrations measured locally with concentrations calculated from first principles when all other trace species which form and react with OH are accounted for. This requires a formidable array of analytical instrumentation to measure species such as ozone, nitrogen oxides, organic and halogen compounds and aerosols. To attempt to understand OH over a seasonal cycle, which is of by far the most value to global and climate models, is feasible only where long time series observations of other gases can also be made. Within this proposal we identify that to obtain year-round measurements of OH, and its partner species HO2, in conjunction with a highly instrumented atmospheric observatory located within the tropical marine boundary layer would be a unique and world leading experiment. Our experiment places a laser induced fluorescence instrument capable of high sensitivity HO/HO2 measurements at the SOLAS Cape Verde atmospheric Observatory. To support nearly one year of radical observations starting in 2008, we propose that the detailed trace gas time series at the Observatory be extended by a further 9 months to end of Apr 2009. Numerous links and users of the potential dataset can be identified already in the global atmospheric modelling communities.


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Carpenter LJ (2012) Ocean-atmosphere trace gas exchange. in Chemical Society reviews

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Lawler M (2011) HOCl and Cl<sub>2</sub> observations in marine air in Atmospheric Chemistry and Physics

Description This project has determined the seasonal cycle of the two most important free radicals in the atmosphere (OH and HO2 ) in the tropical Atlantic marine boundary layer based on surface measurements made at the Observatory, and compared them with models. These are the first seasonal studies of HOx in clean marine background air.
The project extended the SOLAS Cape Verde Observatory time series of continuous atmospheric measurements such that observations were made over three full annual cycles and ran to the end of the SOLAS thematic programme.
Exploitation Route Observations of OH and HO2 in the tropical background air are vital to constrain/evaluate models of the troposphere.

The long term running of the CVAO provides a data context for shorter term studies in the vicinity, and data is used by atmospheric modellers to study photochemistry and trends in the background troposphere.
Sectors Chemicals,Environment

Description The funding provided allowed us to extend the running of the Cape Verde Atmospheric Observatory (CVAO) for a further 2 years, and thus to bridge to National Capability funding from NCAS, which is now awarded as an annual contract. The CVAO is now a global WMO/GAW station, Thus, experimental infrastructure enabled in this research now contributes to UK Government obligations under the United Nations Framework Convention on Climate Change (UNFCCC) and informs it of long-term atmospheric change.
First Year Of Impact 2009
Sector Chemicals,Environment
Impact Types Policy & public services

Description Chapter 1 Lead Author for 2014 WMO/UNEP Scientific Assessment of Stratospheric Ozone Depletion
Geographic Reach Multiple continents/international 
Policy Influence Type Citation in other policy documents
Impact The periodic "state-of-the-science" assessments have guided policymakers as they strengthened the original provisions of the Montreal Protocol on Substances That Deplete the Ozone Layer .
Description Chapter 6 Lead author for 2018 WMO/UNEP Scientific Assessment of Ozone Depletion
Geographic Reach Multiple continents/international 
Policy Influence Type Citation in other policy documents
Impact The 2018 WMO/UNEP Scientific Assessment of Ozone Depletion forms part of the quadrennial assessments of ozone depletion by the Scientific Assessment Panel of the Montreal Protocol. These assessments inform decisions taken by governments for the protection of ozone and climate under the Montreal Protocol.
Description National Capability
Amount £1,600,000 (GBP)
Funding ID Annual contracts awarded to cover costs (incl. salary of staff) of Cape Verde Atmospheric Observatory 
Organisation National Centre for Atmospheric Science (NCAS) 
Sector Charity/Non Profit
Country United Kingdom
Start 06/2009 
Title Data arising from the Cape Verde Atmospheric Observatory 
Description In 2005 we set up the Cape Verde Atmospheric Observatory which is now a global WMO/GAW station. Data is routinely submitted to databases including BADC and WDCGG. 
Type Of Material Database/Collection of data 
Year Produced 2006 
Provided To Others? Yes  
Impact Many (around 20 so far) publications have arisen from the data. Staff are included on WMO/GAW expert groups to advise on VOC and NOx atmospheric measurements and QA/QC. Data is used by atmospheric modelling groups worldwide. 
Description Lecture on History of Atmospheric Chemical Composition at NERC ES4 spring school for Postgraduates 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Around 20-30 PhD atmospheric science students from across the UK attend the ES4 spring school. Many do not have a chemistry background, and this lecture stimulates them to think more about the consequences and impacts of atmospheric chemistry.

Greater awareness of atmospheric chemistry
Year(s) Of Engagement Activity 2013,2014
Description Schools talk (Bootham School, York) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact Around 70 pupils attended this talk on Climate, atmosphere chemistry and ocean interactions, which sparked discussion afterwards. The talk was part of the York Geographical Association series of talks.

Bootham school subsequently asked me to host one of their 6 form students for a day to shadow our research group and find out more about University chemistry research. The student went on to choose Chemistry for their degree.
Year(s) Of Engagement Activity 2011
Description Talk at national/regional A-level Chemistry events "Science Live A level" at Birmingham, Manchester and London 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact designed for A-level Biology, Chemistry or Physics students to hear scientists who are working at the cutting edge of their specialisms and how science can lead to an interesting career.
Year(s) Of Engagement Activity 2019