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SCENARIO: Trapped lee waves as a source of low-level drag on the atmosphere


   Department of Meteorology

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  Dr MA Teixeira, Prof Suzanne Gray, Dr Annelize van Niekerk, Dr Simon Vosper  No more applications being accepted  Competition Funded PhD Project (Students Worldwide)

Reading United Kingdom Applied Mathematics Astrophysics Data Analysis Environmental Biology Fluid Mechanics Meteorology Mathematics

About the Project

Atmospheric models used for numerical weather prediction and climate modelling have large uncertainties in their representation of small-scale processes that contribute to uncertainties in the large-scale movement of air, termed the atmospheric circulation. Indeed, the latest report from the Intergovernmental Panel on Climate Change (IPCC) emphasizes that uncertainties in circulation changes under global warming scenarios, deduced from atmospheric models, are very large. One particular process which both contributes significantly to the atmospheric circulation and is not fully represented in atmospheric models is the drag (i.e. frictional) force produced by small-scale mountains. In this project you will investigate the importance of this missing process using theory, high-resolution numerical model simulations and observations.

When the atmosphere flows over mountains, internal atmospheric waves (known as orographic gravity waves) are generated that exert a drag force on the atmosphere, acting to decelerate the large-scale circulation both locally and remotely. A large proportion of this drag is caused by mountains at horizontal scales that are either partially or totally unrepresented in models typically used for weather forecasting or climate and seasonal projection, so their influence on the circulation is accounted for through approximations called parameterizations. Existing parametrizations focus on the drag produced by vertically propagating orographic gravity waves, which typically acts within wave breaking regions at high altitudes, sometimes reaching as high as the stratosphere (the atmospheric layer above about 10 km altitude) or even above. However, other orographic gravity waves, known as trapped lee waves, are also known to exert a drag on the atmosphere. These trapped lee waves have even smaller horizontal scales and propagate horizontally at lower levels (being made visible by cloud alignments), but are not parametrized in most weather and climate models.

This project aims to clarify the contribution of trapped lee waves to low-level drag exerted on the atmosphere using theory, numerical simulations and observations.

Miguel Teixeira talks about this project on YouTube: https://youtu.be/vo3iUzstY2s

Training opportunities:

This project will provide skills in numerical and mathematical modelling and data analysis. It will offer opportunities to attend postgraduate modules and summer schools (e.g., Summer School on Fluid Dynamics of Sustainability and the Environment). The student will have CASE support for an internship at the Met Office (Exeter), where two of the co-supervisors are based. This will not only allow experience of work with models used operationally for atmospheric forecasts, but also contact with a professional environment. It will also provide additional opportunities for training, via training courses, workshops and seminars.

Student profile:

Applicants should hold or expect to gain a minimum of a 2:1 Bachelor Degree, Masters Degree with Merit, or equivalent in physics, mathematics or a closely related environmental or physical science. Good computational skills are essential. Experience in numerical modelling, applied mathematics and data processing would be preferred but are not essential. The student should be enthusiastic, eager to learn, and have a keen interest in physical and mathematical aspects of atmospheric dynamics.

To apply, please follow the instructions at https://research.reading.ac.uk/scenario/apply/


Funding Notes

This project is potentially funded by the Scenario NERC Doctoral Training Partnership, subject to a competition to identify the strongest applicants.

The project has CASE funding from the Met Office.

Due to UKRI rules, the DTP can only fund a very limited number of international students. We will only consider applications from international students with an outstanding academic background placing them in the top 10% of their cohort.

References

Teixeira, M.A.C., Miranda, P.M.A. (2017) Drag associated with 3D trapped lee waves over an axisymmetric obstacle in two-layer atmospheres , Quarterly Journal of the Royal Meteorological Society, 143, 3244-3258. doi: 10.1002/qj.3177

Vosper, S.B., Ross, A.N., Renfrew, I.A., Sheridan, P., Elvidge, A.D., Grubisic, V. (2018) Current Challenges in Orographic Flow Dynamics: Turbulent Exchange Due to Low-Level Gravity-Wave Processes, Atmosphere, 9, 361. doi: 10.3390/atmos9090361
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