Project highlights
- A complete laboratory re-evaluation of the infrared spectroscopy of carbonyl sulfide (COS)
- Production of a new COS linelist to improve remote-sensing observations of COS
- The opportunity to work with COS satellite data and its applications
Overview
Earth has a number of natural climate-regulating mechanisms, including the biospheric uptake of carbon by vegetation and the abundance of stratospheric sulfate aerosols (SSA). The former directly removes some carbon dioxide (CO2) emissions from the atmosphere, while the latter have a cooling effect on climate. Both mechanisms are intrinsically linked to the trace gas carbonyl sulfide (COS).
COS is the most abundant sulfur-containing molecule in the atmosphere. The dominant source is biogenic activity in the oceans, while the sinks are due to uptake by vegetation (by the same initial pathway as CO2) and destruction in the stratosphere (SSA formation). Despite this importance, its atmospheric sources and sinks are not well quantified. There is a growing recognition that COS can be used as a climate diagnostic, and that a better understanding of its atmospheric variations will lead to a deeper understanding of CO2 uptake and SSA formation, and the responses of these to our changing climate.
Observations of COS are made from a number of satellite instruments using different infrared bands: the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS; limb) which utilises the strongest ν3 band at 2062 cm-1, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS; limb) instrument which utilises the weaker ν1 band at 858 cm-1, and the Infrared Atmospheric Sounding Interferometer (IASI; nadir) instruments which utilise the ν3 band. Additionally, ground measurements as part of the Network for the Detection of Atmospheric Composition Change (NDACC) utilise the ν3 band, as does the balloon-borne JPL MkIV interferometer which also uses the weaker ν1+ν3 and 2ν3 bands for the lowest altitudes.
HITRAN contains a COS linelist that has been utilised for all these remote-sensing observations. In order to improve these observations, we require reference COS spectroscopy that is accurate and robust. The HITRAN linelist has a number of deficiencies that urgently need to be resolved. Uncertainties in the line intensities can vary from 5% to 20%; this needs to be reduced to under 1%. This work will be the first detailed laboratory study of COS lineshape parameters and their temperature dependences. They will directly improve the observational data products.
CENTA Flagship
This is a CENTA Flagship Project
Case funding
This project is suitable for CASE funding
Host
University of LeicesterTheme
- Climate and Environmental Sustainability
Supervisors
Project investigator
- Dr Jeremy Harrison (University of Leicester & NCEO, email: [email protected])
Co-investigators
- Dr Gang Li (PTB)
- Prof John Remedios (University of Leicester & NCEO)
How to apply
- Each host has a slightly different application process.
Find out how to apply for this studentship. - All applications must include the CENTA application form. Choose your application route
Methodology
The candidate will perform a re-evaluation of the infrared spectroscopy of COS. This will involve new measurements at the NCEO SPectroscopy for ENvironmental SEnsing Research (SPENSER) laboratory at Space Park Leicester. There is also the opportunity to visit the PTB in Braunschweig, Germany, which has additional laboratory facilities for the characterisation of gas samples to metrological accuracy. Infrared spectra will be recorded for both pure and air-broadened COS over a range of temperatures and pressures. These will be analysed to produce a robust COS linelist that will provide a more accurate basis for COS retrievals from remote-sensing observations.
With collaborators, the candidate will investigate how the new spectroscopy improves ACE-FTS, MIPAS, and IASI retrievals. The new spectroscopy will be implemented within the NCEO-Leicester IASI COS retrieval scheme, and there will be the opportunity to work with other scientists in the NCEO that utilise these data for carbon cycle science.
Training and skills
DRs will be awarded CENTA Training Credits (CTCs) for participation in CENTA-provided and ‘free choice’ external training. One CTC can be earned per 3 hours training, and DRs must accrue 100 CTCs across the three and a half years of their PhD.
This studentship provides an exciting opportunity to work with cutting-edge spectroscopy measurements, satellite observations and atmospheric radiative transfer techniques in a challenging area of atmospheric science. This project covers a range of topics: atmospheric spectroscopy; remote sensing; retrieval techniques; atmospheric chemistry; data visualisation & analysis. The National Centre for Earth Observation (NCEO) will provide additional training opportunities via its Researchers’ Forum and regular conferences/workshops, and enable the student to interact with scientists working in Earth Observation on a national level. There will also be the opportunity to attend and present at international conferences.
Partners and collaboration
The candidate will be based at the Space Park Leicester facility and work within the National Centre for Earth Observation (NCEO). The NCEO (www.nceo.ac.uk) is a distributed NERC centre providing the UK with national capability in EO science. The candidate will be exposed to a wide range of research techniques in a multi-disciplinary research environment.
This project has been developed in collaboration with the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig, Germany. The successful applicant will have the opportunity to visit the PTB to perform spectroscopic measurements. The PTB has additional laboratory facilities for the characterisation of gas samples to metrological accuracy.
Further details
Dr Jeremy Harrison is the NCEO’s spectroscopy leader and capability leader in atmospheric radiative transfer. Based in the Earth Observation Science (EOS) group at the University of Leicester, his expertise lies in atmospheric spectroscopy, atmospheric radiative transfer, and the remote sensing of trace gases.
Interested applicants are invited to contact Dr Jeremy Harrison ([email protected]). Note that all potential applicants are strongly advised to make contact before applying.
To apply to this project:
- You must include a CENTA studentship application form, downloadable from: CENTA Studentship Application Form 2025.
- You must include a CV with the names of at least two referees (preferably three) who can comment on your academic abilities.
- Please submit your application and complete the host institution application process via: CENTA PhD Studentships | Postgraduate research | University of Leicester. Please scroll to the bottom of the page and click on the “Apply Now” button. The “How to apply” tab at the bottom of the page gives instructions on how to submit your completed CENTA Studentship Application Form 2025, your CV and your other supporting documents to your University of Leicester application. Please quote CENTA 2025-L6 when completing the application form.
Applications must be submitted by 23:59 GMT on Wednesday 8th January 2025.
Possible timeline
Year 1
Literature review; learn how to operate a Bruker IFS 125HR Fourier transform spectrometer; begin laboratory measurements of OCS over a range of pressures and temperatures.
Year 2
Finish laboratory measurements; learn and apply the multispectrum fitting technique to the recorded spectra; produce a final COS linelist.
Year 3
Interact with retrieval scientists (IASI, MIPAS, ACE) to produce new retrieved COS concentrations; determine how the new spectroscopic data improves the retrieved data; investigate implications of new data on atmospheric radiative transfer.
Further reading
Glatthor et al.: Global carbonyl sulfide (OCS) measured by MIPAS/Envisat during 2002–2012, Atmos. Chem. Phys., 17, 2631–2652, https://doi.org/10.5194/acp-17-2631-2017, 2017.
Ma et al.: Inverse modelling of carbonyl sulfide: implementation, evaluation and implications for the global budget, Atmos. Chem. Phys., 21, 3507–3529, https://doi.org/10.5194/acp-21-3507-2021, 2021.
Sung et al.: Line strength measurements of carbonyl sulfide (16O12C32S) in the 2v3, v1+2v2+v3, and 4v2+v3 bands, JQSRT, 110, 2082-2101, https://doi.org/10.1016/j.jqsrt.2009.05.013, 2009.
Whelan et al.: Reviews and syntheses: Carbonyl sulfide as a multi-scale tracer for carbon and water cycles, Biogeosciences, 15, 3625–3657, https://doi.org/10.5194/bg-15-3625-2018, 2018.