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Modelling the influence of solar activity on climate. PhD in Physics and Astronomy (NERC GW4+ DTP)

  • Full or part time
  • Application Deadline
    Monday, January 06, 2020
  • Competition Funded PhD Project (European/UK Students Only)
    Competition Funded PhD Project (European/UK Students Only)

Project Description

Lead Supervisor
Dr James Manners, Department of Physics and Astronomy, College of Engineering, Mathematics and Physical Sciences, University of Exeter

Additional Supervisors
Prof Chris Budd, Department of Mathematical Sciences, University of Bath
Prof Nathan Mayne, Department of Physics and Astronomy, College of Engineering, Mathematics and Physical Sciences, University of Exeter

Location: University of Exeter, Streatham Campus, Exeter, EX4 4QJ

This project is one of a number that are in competition for funding from the NERC GW4+ Doctoral Training Partnership (GW4+ DTP). The partnership aims to provide a broad training in the Earth, Environmental and Life sciences, designed to train tomorrow’s leaders in scientific research, business, technology and policy-making. For further details about the programme please see http://nercgw4plus.ac.uk/

Project Background

The Earth’s climate is ultimately driven by the Sun but the effects of variations over the 11-year solar cycle and longer-term changes in solar output are not well modelled by today’s climate and decadal forecasting models. Solar variations are largest in the ultra-violet to X-ray spectral regions which are absorbed in the upper atmosphere from the stratosphere to the lower thermosphere. Accurate modelling of the upper atmosphere is crucial to understanding the “top-down” mechanisms that link these variations to their effect on surface climate. This project will build on work to extend the Met Office Weather and Climate model into the mesosphere and lower thermosphere, with the addition of physical processes to represent photochemistry and energetic particles. Coupling this extended climate model to an interactive ocean model will allow pioneering studies into the effects of solar variability on regional climate.

Project Aims and Methods

Phase 1: Model development
This work will build on an existing collaboration to extend the upper boundary of the Met Office Unified Model from the mesopause (at around 85km) to the lower thermosphere (around 150km). In particular, the mesosphere-lower-thermosphere (MLT) region is where the majority of far- and extreme-ultraviolet light is absorbed leading to processes that drive the large rise in temperature of the thermosphere. The aims of this project will be to develop and validate an accurate treatment of the photolysis and chemistry of the MLT region using the “Socrates” radiative transfer code, and the UKCA (United Kingdom Chemistry and Aerosols) scheme.

Phase 2: Coupled climate model investigations
A number of possible mechanisms exist for the influence of solar variations on the upper atmosphere to be transported to the lower troposphere, principally affecting regional rather than global climate [1]. Perhaps the largest effect is the modulation of ozone absorption which peaks in the stratosphere causing variations in stratospheric temperature that in turn alter the pressure and temperature at the surface. Experiments with the standard Met Office climate model have shown that, through this mechanism, low solar activity can drive cold winters in northern Europe and the US [2, 3]. The solar cycle has a significant effect on photochemical activity in the stratosphere, mesosphere and lower thermosphere which can lead to changes in the amount of ozone and knock-on effects on surface climate [4]. The solar cycle also influences energetic particle precipitation (EPP) through changes in geomagnetic activity. EPP leads to the production of reactive odd nitrogen (NOX) which can then be transported to the stratosphere leading to reductions in ozone [5]. Investigation of these mechanisms requires a model that extends from the surface to the upper atmosphere and also allows the ocean to respond by coupling to an ocean model. Previous studies have shown the tropospheric response to the solar cycle may be muted by fixing the sea surface temperature [6].

The aims of this phase will be to perform coupled ocean-atmosphere climate runs with the new extended model. Different solar forcing may be applied and the resulting effects analysed to investigate the “top-down” mechanisms that emerge from the model.

In this project expertise in radiative transfer modelling will come from Manners, in upper atmosphere processes and related numerical calculations from Jackson and Budd and in idealised model development from Mayne. All four will be closely involved in all aspects of the project supervision, through regular face to face and Skype meetings. The project will start with the plan as described above, but as with all research this plan will develop as the project continues. We will have weekly meetings with the student in which they will be expected to lead creatively on the evolution of the project.

Funding Notes

For eligible students, the studentship will provide funding of fees and a stipend which is currently £15,009 per annum for 2019-20. The studentships comprises:

- A stipend for 3.5 years (currently £15,009 p.a. for 2019/20) in line with UK Research and Innovation rates
- Payment of university tuition fees;
- A research budget of £11,000 for an international conference, lab, field and research expenses;
- A training budget of £3,250 for specialist training courses and expenses.
- Travel and accommodation is covered for all compulsory DTP cohort events
- No course fees for courses run by the DTP

References

References / Background reading list

[1] Lockwood (2012): Solar influence on global and regional climates, DOI: 10.1007/s10712-012-9181-3

[2] Ineson et al (2011): Solar forcing of winter climate variability in the Northern Hemisphere, DOI: 10.1038/ngeo1282

[3] Ineson et al (2015): Regional climate impacts of a possible future grand solar minimum, DOI: 10.1038/ncomms8535

[4] Merkel et al (2011): The impact of solar spectral irradiance variability on middle atmospheric ozone, DOI: 10.1029/2011GL047561

[5] Randall et al (2015): Simulation of energetic particle precipitation effects during the 2003–2004 Arctic winter, DOI: 10.1002/2015JA021196

[6] Marsh et al (2007): Modelling the whole atmosphere response to solar cycle changes in radiative and geomagnetic forcing, DOI: 10.1029/2006JD008306

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