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
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.
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/