The elusive BVOC: mapping atmospheric isoprene from space
Dr J Harrison
Dr M Barkley
No more applications being accepted
Funded PhD Project (European/UK Students Only)
It is well established that terrestrial vegetation emits a diverse range of reactive biogenic volatile organic compounds (BVOCs) into the atmosphere, which serve important roles in the biosphere, influencing global atmospheric chemistry and affecting climate. The most important BVOC is isoprene, whose annual emissions of ~500 Tg C / yr comprise nearly half the total global BVOC budget.
Isoprene is a precursor for tropospheric ozone, which is the third most important greenhouse gas and a surface air pollutant that affects the human respiratory system and agricultural crop yields. Tropospheric ozone is also the dominant source of the hydroxyl radical (OH), which initiates tropospheric oxidation chemistry, and is an important chemical sink of other greenhouse gases (e.g., methane). Isoprene is also a precursor for secondary organic aerosols (SOA) that affect air quality, cloud properties, and influence direct radiative forcing.
Accurate knowledge of isoprene emissions is therefore critical for understanding and predicting the atmospheric distributions of tropospheric ozone and SOA. Satellite observations of atmospheric isoprene would provide an unprecedented opportunity to conduct detailed studies of the biosphere-atmosphere exchange of terrestrial ecosystems, and through inversion of the retrieved measurements, would enable continuous top-down monitoring of global isoprene emissions over multiple years. Over large, remote, and often high isoprene emitting regions such as the tropics, satellites offer the only means of observing ecosystem dynamics.
This project offers an exciting opportunity to obtain the first spaceborne measurements of isoprene from the Infrared Atmospheric Sounding Interferometer (IASI) instruments through the development and application of an optimal estimation retrieval algorithm which utilises a new high resolution IR absorption cross-section dataset. The IASI isoprene retrievals will be critically assessed over different ecosystems, through direct and indirect comparisons with campaign field data and atmospheric model outputs, provided by world-leading groups and teams.
The student will use data from the series of IASI nadir-sounding spectrometers on EUMETSAT’s Metop-A (launched 2006), MetOp-B (launched 2012) and MetOp-C (scheduled for launch in November 2018) satellites, each offering twice daily global coverage through a swath width of 2200 km, with a 12 km sub-satellite pixel footprint, and delivering thousands of radiance observations per day. To retrieve isoprene from IASI radiances the student will adapt an existing retrieval code (ULIRS) with a proven credibility in determining trace gas measurements from IASI spectra. The aim is to retrieve weekly-to-monthly observations of column-integrated isoprene at horizontal resolutions of less than 5°×5° over multiple years (2007 to present). The IASI isoprene measurements will be critically evaluated against a wealth of in-situ observations, and compared with estimates from chemical transport models (CTMs) such as GEOS-Chem. The creation of this global dataset will provide invaluable data for improving both BVOC emission and CTMs
This project offers the chance to interact and collaborate with world-leading scientists who regularly measure isoprene on field campaigns using in situ techniques. The student will also collaborate with modellers 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 student will therefore be exposed to a wide range of research techniques in a multi-disciplinary research environment.
Entry requirements Applicants are required to hold/or expect to obtain a UK Bachelor Degree 2:1 or better in a relevant subject. The University of Leicester English language requirements apply where applicable.
How to apply Please refer to the CENTA Studentship application information on our website for details of how to apply.
As part of the application process you will need to:
• Complete a CENTA Funding form – to be uploaded to your PhD application
• Complete and submit your PhD application online. Indicate project CENTA2-PHY3-HARR in the funding section.
• Complete an online project selection form Apply for CENTA2-PHY3-HARR
This studentship is one of a number of fully funded studentships available to the best UK and EU candidates available as part of the NERC DTP CENTA consortium. The award will provide tuition fees as the UK/EU rate and a stipend at the RCUK rates for a period of 3.5 years.
For more details of the CENTA consortium please see the CENTA website: www.centa.org.uk.
Applicants must meet requirements for both academic qualifications and residential eligibility: http://www.nerc.ac.uk/skills/postgrad/