Overview

The upper atmosphere of the earth is a complex, vertically coupled system.  The uppermost layers of the atmosphere, including the mesosphere, thermosphere, ionosphere and the overlying magnetosphere play an important role in the coupling of energy and momentum to and from the lower atmospheric layers of the stratosphere and troposphere.  Understanding this vertical coupling is a vital component of our efforts to understand and predict the climate system, and to distinguish properly between anthropogenic and solar driven changes in climate.  Atmospheric gravity waves (AGWs) are a key phenomenon in mediating the transfer of energy and momentum between the upper and lower layers of the atmosphere.  The parameterisation of the momentum flux in AGWs, and its dependence on solar activity is a major source of uncertainty in the current suite of global atmospheric circulation models.  Here we will produce a long-term, near-global evaluation of AGW amplitude, occurrence and propagation for ingestion into new generations of such global models, improving our knowledge of the whole coupled atmosphere system as a step towards improving our understanding of the influence of near-Earth “space weather” on our climate. 

We will exploit a variety of techniques to characterise the flux of AGWs over a long time period, to reveal seasonal, local time and solar cycle effects, and over an extensive latitude range, through the exploitation of ground backscatter from both the poleward pointing radar main beam, and through the equatorward pointing rear lobe.  The data gathered will include new data from the recently-constructed NERC European low latitude SuperDARN radar constructed at Leicester University and the British Antarctic Survey radar systems in the Southern hemisphere, as well as radars from international collaborators.

 

(A) modelled high frequency radiowave ray paths through an AGW, showing the focussing and defocussing on the ground. (b) An example of typical corresponding SuperDARN ground scatter power, modulated by an AGW.

Methodology

SuperDARN radars have a long heritage of the observation of AGWs, ranging from signatures at very high latitudes, down to mid-latitudes.  The propagation of AGWs through the SuperDARN radar fields of view has a number of effects in the radar data, including the modulation of the power received from radio waves reflected from the ground, and modulation of the skip distance (the closest range from which such ground scatter is recorded).  These features, when coupled with modelling of the propagation of radio waves through the ionosphere, can reveal the amplitude, occurrence and propagation characteristics of AGWs. A statistical evaluation of these wave characteristics, as determined by the ~30 radars of the SuperDARN network over more than 20 years of operations will allow the most complete characterisation of the AGW fluxes to date. This will produce an unparalleled dataset of AGW fluxes for use in coupled atmospheric models.

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10 day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to CENTA research themes. 

The project will build upon 20 years of experience within the Radio and Space Plasma Physics (RSPP) group in the design, operation, and exploitation of ionospheric radars. Training in relevant plasma and atmospheric physics and radar techniques will be provided as well as training in computer programming, raytracing simulations and the data analysis required.  The student will gain a great deal of expertise in research methods, data management, analytical thinking and computer programming. All students contribute regularly to group meetings through presentation of their work. 

Timeline

Year 1: The student will familiarise themselves with the operation and analysis of SuperDARN data, and develop and validate the tools for an automated parameterisation of AGW occurrence in SuperDARN ground scatter.

Year 2: The student will perform a major statistical study of AGW occurrence, quantifying the local time, solar cycle and geographic variability of the AGW phenomena.  This will include detailed multi-instrument case studies to ensure an accurate parameterisation, and case studies to cover intervals of particular geophysical interest (for example intervals of significant solar disturbance.

Year 3: The student will liaise with the atmospheric modelling community to maximise the utility of the AGW database, and explore the implications for whole atmosphere modelling and climate.

Partners and collaboration (including CASE)

As the PI institute of SuperDARN, Leicester also has access to all SuperDARN data and strong links with the PI institutes of the >30 constituent radars around the world.  During the course of the project we will liaise with the UK Met office and the atmospheric modelling community to determine the most appropriate format for our AGW parameterisation.  The project will be supervised by Professors Milan and Yeoman, who have over 20 years experience of the analysis of SuperDARN radar data.

Further Details

Prof. Tim Yeoman

Radio and Space Plasma Physics Group

Department of Physics and Astronomy

University of Leicester

University Road, Leicester

LE1 7RH

Tel: +44 116 2523564

Email: yxo@le.ac.uk