IGS: Current and Recent Graduate Research
Christopher Allen
Atmospheric mechanisms of mineral aerosol emission and transport over the central Sahara desert
Supervisor(s):
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Academic Profile
Christopher is a DPhil student in the Climate Systems and Policy research cluster (physical climate and biogeochemical processes).
Christopher graduated with a first class degree in geography from the University of Oxford in 2009. In his second and third years he specialised in climate variability and Quaternary science. His undergraduate dissertation, which won the university's H.O. Beckit prize for best physical geography dissertation, sought to understand why some climate models are able to correctly simulate El Niño Southern Oscillation teleconnections to southern Africa, while others are much less successful. As well as a general interest in African climate, Christopher has a specific interest in the processes of dust storm generation, and in the meteorological impacts of dust storms over the continent and wider regions. He is also broadly interested in oceanography and ocean-climate interaction.
In January 2011 Christopher was appointed to a Research Assistantship on the Fennec project at the University of Oxford. The project, led by Professor Richard Washington, is an international collaboration that aims to produce a comprehensive understanding of the Saharan climate system.
As part of the project Christopher has done fieldwork in Mauritania, Morocco and Mali. In Mauritania, together with Dr Sebastian Engelstaedter, he trained staff from the Mauritanian meteorological service on the installation and operation of several meteorological instruments for the Fennec ground campaign. Christopher took part in both the Fennec pilot and Fennec main campaigns, accruing roughly 45 hours of flying time over the Sahara as a mission scientist / observer on board the NERC-Met Office BAE 146 atmospheric research aircraft.
Awards
- 2007-2009 - Academic Scholarship, Hertford College Oxford
- 2009 - H.O. Beckit Memorial Prize for best physical geography dissertation
- 2011 - Nominated for the AXA Doctoral Fellowship by the University of Oxford
- 2011-2015 - Natural Environment Research Council PhD studentship
Current Research
Prior to the Fennec campaign there was little high quality observational data on the atmosphere of the Sahara desert. Nonetheless it was clear that the Sahara played an important regional and perhaps global role in the climate system. It has been known for some time for example that the Saharan heat low is one control on the West African Monsoon.
In boreal summer, the central Sahara is also the dustiest place on Earth. The processes that control this dust emission are not fully understood; in particular, their relative importance is unclear. A major aim of Christopher's research is to partition the atmospheric dust burden between different emission processes such as density currents, low level jets, dry cyclones and others. The research will be undertaken with a combination of Fennec station, radiosonde, satellite, model and aircraft data.
Once entrained, mineral aerosol may be transported vertically, advected horizontally or remain locally suspended. But dust is not a passive constituent of the atmosphere. It itself can influence atmospheric circulation, for instance through absorbing solar radiation, emitting long wave radiation and through influencing cloud lifetimes. Further understanding the interaction between atmospheric dynamics and dust is important not just for our knowledge of Saharan climate, but for the atmosphere as a whole.
Past Research Projects
- 2009 - Why is it difficult to attribute recent changes in tropical cyclone activity to global warming?
- 2008-2009 - Coupled climate model simulations of El Niño Southern Oscillation teleconnections over southern Africa
- 2008 - Conflict or corroboration? Palaeoceanographic evidence for changes in North Atlantic deep water formation during the late Pleistocene and the last deglaciation