Monday, 18 February 2013

Vacancy: Arctic PhD Studentship in Vertical Atmospheric Coupling


The British Antarctic Survey intends to target two of its NERC quota (algorithm) awards for 2013 specifically at Arctic research. This is one of five research topics offered spanning the wide range of activities currently undertaken within our Polar Science for Planet Earth Programme. The funding will go to the two projects with the best applicants.

Exploring northern hemisphere gravity wave breaking with atmospheric radar: mesospheric circulation, vertical coupling of the atmosphere and the role of geomagnetic activity (Arctic Project 4)

The project will be co-supervised by British Antarctic Survey and Lancaster University.

Gravity waves (atmospheric buoyancy waves) are a highly important means of transporting energy from the lower to the upper atmosphere and so potentially very important for understanding climate variability, yet due to their scale sizes they are not resolved in global circulation models. In the troposphere gravity waves are generated by sources such as air-flow over the mountains or large convective storms and can be commonly spotted as ripples in the clouds. Breaking of waves in the mesosphere (~50-90 km altitude) drives the pole-to pole circulation that links the cold summer mesopause and the strong down-welling that occurs in the polar vortex in the winter hemisphere. This downward motion is a potentially important part of the process by which solar activity can influence regional climate, via the transport of ozone-destroying chemical species following geomagnetic activity. WACCM (Whole Atmosphere Coupled Community Model) simulations have suggested that a change in the altitude of gravity wave breaking effects the peak meridional circulation, the vertical transport of important chemical constituents and their mixing ratios. Gravity waves that penetrate into the thermosphere influence the density of ionosphere and may have an upward impact on geomagnetic storms and the resultant space weather effects. Other sources of gravity waves in middle and upper atmosphere in the Polar Regions are the polar vortex itself and the geomagnetic activity.

This PhD project will use archive and new data from the European Incoherent Scatter (EISCAT) Radars in northern Norway to characterise the occurrence and properties of polar mesosphere winter echoes (PMWE); strong coherent radar signals that are strongly related to atmospheric turbulence and the presence of charged fine dust. The ‘polar’ and ‘winter’ terms are historical misnomers as these echoes are observed all year around and at both at polar and mid-latitudes. Recent work has shown that turbulence is the dominant mechanism behind PMWE and it is highly characteristic of gravity wave breaking. The atmosphere above the EISCAT radars is a perfect laboratory for this study: it is a hot-spot for gravity wave generation, close to the polar vortex and the auroral zone.

The successful candidate will analyse data from the EISCAT radars and compile a catalogue of PMWE using the observations to determine the altitude and temporal variation of gravity wave breaking. They will establish the sensitivity of the local mean neutral wind flow to changes in the altitude of the turbulent region using several different types of atmospheric radar in collaboration with national and international partners. The student will help to plan and take part in experiment campaigns, developing novel experiments to make new observations. They will use radar at multi-frequencies to probe the turbulent structure and establish whether any differences are due to dust charging or gravity wave vertical wavelength. A combination of auroral and meteorological observations will be used to study the roles played by the unstable polar vortex and auroral activity on the mean wind flow and gravity wave turbulence.

Closing date: 28th February 2013.

For more information and application details, please refer to the original announcement.

Photo: British Antarctic Survey Headquarters, Cambridge, UK; Wikimedia Commons (source).

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