Alan Hewitt

Ph.D Thesis available here

Ph.D. Abstract

Investigating land air carbon fluxes using a Lagrangian model and satellite retrieved carbon dioxide.

The existing generation of satellite instruments (such as SCIAMACHY and AIRS) have allowed the retrieval of atmospheric mixing ratios of carbon dioxide. This data can be used to investigate carbon fluxes between the terrestrial biosphere and the atmosphere, either alone or complemented by the high precision but low density network of surface measurement sites.

A methodology has been developed to investigate regional scale carbon budgets, based on the UK Met Office Lagrangian trajectory model NAME (Numerical Atmospheric-dispersion Modelling Environment). The model provides information about the origin of air masses sampled by the satellite instrument and also residence time information over various parts of the land surface.

The method was used in forward mode, where existing surface flux information (e.g. CarbonTracker data) were combined with the background CO2 mixing ratio to obtain an atmospheric concentration. Comparing the modelled and satellite observed CO2 fields allowed testing of carbon flux inventories.

The model was also run in inverse mode, where the change in carbon mass between the satellite retrieved concentration and the background concentration was combined with the residence times from the NAME model. With the assumption that the region investigated consists of homogeneous carbon flux ecoregions, flux values were assigned to the ecoregions which provide the best match with the observed mass exchange between foreground and background satellite measurements.

Both methods have been tested using synthetic CO2 fields and real SCIAMACHY/FSI retrieved CO2 over the North American region, allowing this method to be compared with CO2 fields and carbon fluxes from top-down and bottom-up networks. An assessment was also made on the suitability of SCIAMACHY/FSI for the purpose of forward and inverse modelling of carbon fluxes.

Contact me

My alternative email address: ajh67leicester at yahoo.co.uk

Publications

Journal Publications

Hewitt A. J., Doss N., Zobov N. F., Polyansky O. L., Tennyson J., 2005, “Deuterated water: partition functions and equilibrium constants”, MNRAS, 365, 1123-1126.

M. P. Barkley, P. S. Monks, A. J. Hewitt, T. Machida, A. Desai, N. Vinnichenko, T. Nakazawa, M. Yu Arshinov, N. Fedoseev, T. Watai, 2007, “Assessing the near surface sensitivity of SCIAMACHY atmospheric CO2 retrieved using (FSI) WFM-DOAS”, Atmos. Chem. Phys., 7, 3597 – 3619.

Proceedings

Alan Hewitt, Michael Barkley, Paul Monks, 2006, “Assessment of the near surface sensitivity of the Full Spectrum Initiation (FSI)-WFM-DOAS retrieval of carbon dioxide columns.”, ACVE-3.

Book Chapter

M. P. Barkley, A. J. Hewitt and P. S. Monks (Heiko Balzter - Editor), “Chapter 11: Investigating regional scale processes using remotely sensed atmospheric CO2 column concentrations from SCIAMACHY” of the book “Environmental Change in Siberia: Earth Observation, Field Studies and Modelling.”, 2010, Springer.

Conference/Workshop Presentations

Oral Presentations:

12/2006: 3rd Workshop on the Atmospheric Chemistry of ENVISAT (ACVE-3) Frascati, Italy

Oral presentation – “Assessment of the near surface sensitivity of the Full Spectrum Initiation (FSI)-WFM-DOAS retrieval of CO2 columns.”

Poster Presentations

04/2009: European Geosciences Union, Vienna, Austria

“A new method to investigate regional scale carbon budgets from satellite measured carbon dioxide.”

04/2008: European Geosciences Union, Vienna, Austria

“Investigating CO2 fluxes over North America using SCIAMACHY retrievals.”

09/2007: Royal Meterological Society Conference, Edinburgh, UK

“Inversion of SCIAMACHY retrieved CO2 columns.”

03/2007: The Ninth Great British Research and R&D show, House of Commons, London

“Measuring atmospheric carbon dioxide from space.”

08/2006: 3rd ENVISAT summer school, Frascati, Italy

“Investigating CO2 fluxes through data assimilation.”

07/2006: UK GRAD Midland regional hub, University of Warwick

“Measuring carbon dioxide from space.”

06/2006: Festival of postgraduate research (FPGR), University of Leicester

“Measuring carbon dioxide from space.”

Links to related work

Alan Hewitt Homepage (other) - University of Leicester - Carbon Dioxide research group

Education

  • Ph.D. Atmospheric Physics, University of Leicester, 2010
  • M.Sci Astrophysics, University College London, 2004
  • Other

  • I have taken part in the “Ninth Great British Research and R&D show” at the House of Commons in March 2007.
  • I have taken part in the “Environment YES” Young Entrepreneurs Scheme in October 2006.
  • I have attended the “Third Envisat Summer School” at ESRIN in August 2006.
  • I have attended the “NCAS Summer School” in the isle of Arran in September 2006.
  • I have taken part in the “Festival of Postgraduate Research” at the University of Leicester in June 2006, where my poster was highly commended.
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