Aim: To build robust 3D models of both local and global atmospheric turbulence, in order to i) routinely characterise the atmospheres of small transiting exoplanets and ii) improve satellite communication by supporting the transition from traditional radio waves to faster, cheaper and more secure Free Space Optical Communication (FSOC). Ground-based astronomy and FSOC are both currently limited by the Earth's turbulent atmosphere. By pioneering new concepts in atmospheric characterisation and correction, I will: 1. enable astronomical observations from ground-based telescopes to be comparable to, and potentially better than, space telescopes 2. enable regular, robust and sustained FSOC links between the ground and orbiting satellites. These innovative techniques have multiple applications, including: 1. learning about small Earth-like exoplanets orbiting distant stars 2. retrieving data from space science satellites used for Earth observation, inter-planetary and deep space missions. There are many reasons to study exoplanets. These range from trying to understand how solar systems form and evolve, to the search for extra-terrestrial life. The former will allow us to explore the vast diversity of worlds that exist and to discover the physical universe on a whole new level. The latter being incredibly exciting with implications for the whole of humanity. Simply detecting an exoplanet is not enough, we must also characterise these planets in order to ascertain what they are like. There are several ways to characterise exoplanets. One of the most powerful and certainly the most productive is the transit method. As a planet passes in front of a star it blocks some of the light. This reduction in intensity is observable by telescopes and is used to deduce the presence of an exoplanet orbiting a distant star and a wealth of information about it. The amount of light absorbed or emitted by the planet in several wavelengths gives us a detailed impression of the temperature distribution, dynamics, composition and weather systems of the exoplanet's atmosphere. Several large transits surveys such as TESS and NGTS and the radial-velocity surveys of HARPS and HARPS-N, together with future space satellites such as CHEOPS and PLATO, will provide abundant interesting targets which will require precise follow-up. The extra precision attainable by using the large collecting areas and the accessibility of multiple ground-based telescopes would allow the routine and targeted characterisation of the atmospheres of distant small exoplanets. However, this is beyond current capabilities. The Earth's atmosphere causes intensity fluctuations, called scintillation, which can be seen as twinkling by the naked eye. This twinkling limits the sensitivity of ground-based observations to that of exoplanets many times larger than the Earth. In addition to astronomy, the recently expanding field of FSOC has very similar problems. The large bandwidth of using optical wavelengths, as opposed to conventional radio communication, will enable 10-100 times more data to be retrieved from space science satellites used for Earth observation, inter-planetary and deep space missions. This increase in transmission rates is analogous to moving from traditional copper cables to fibre optics. In addition, by transitioning to optical wavelengths, we can meet demands for higher capacity data transmissions that societies around the world have become accustomed to. Through a combination of characterising the Earth's atmospheric turbulence using novel instrumentation, with a numerical global turbulence forecast model, which I am developing, I will assess the implications of the Earth's atmosphere on astronomy and FSOC and develop new correction mechanisms, including tomographic scintillation correction. It is only with the combination of these themes can we truly unlock the full potential of ground-based telescopes.

At the start of 2022, a little studied Pacific Island volcano, Hunga Tonga-Hunga Ha apai, erupted with an energy ~1000x greater than the atomic bomb dropped on Hiroshima. This eruption created waves that reverberated around the Earth and sent up a volcanic plume that reached ~55 km, half-way to space. Although this eruption was devastating for Tonga, mercifully, from a global perspective, it was short in duration and did not occur in a densely populated area or one of vital food production, transport, or energy transmission. Had it done so there would have been major impacts on climate and society. Volcanologists study past volcanic events so that we can understand their return periods and impacts and help prepare society for the next 'big one'. Large eruptions loft enormous quantities of ash and gas into the atmosphere, these plumes undergo regional and global distribution and can travel thousands of kilometres from their source. In most surface environments the fine-grained volcanic fallout is rapidly washed away. Ice sheets are the exception to this, and by drilling into the ice and extracting core scientists can identify the sulfur-rich layers and ash deposited by these past eruptions. Although ice cores provide the undisputed best archive of past volcanism, interpreting this record is not straightforward and our current techniques tell us little about where the source volcano was located and what its climate impact might have been. Even in records that span the last 2500 years, we only know the location of 7 of the 25 largest volcanic eruptions. This project will develop novel ice core chemical analyses to extract detailed information on the source, style, and environmental impacts of past volcanism. It will take advantage of two recent breakthroughs in ice core research. The first is high time resolution chemical analysis of volcanic sulfur which provide critical information about the height the volcanic plume reached in the atmosphere and the proximity of the eruptive source to the ice sheet. The second is ash particle chemistry which can help pinpoint the volcanic source and setting. During the first phase of this fellowship, we validated these techniques for well-known eruptions where we already have good information on the eruptive source, style and climatic impacts. We set up new protocols to analyse tiny fragments of ash (many of which are smaller in diameter than a human hair) and developed a computer model that can predict the sulfur chemistry for different eruption styles, allowing us to infer the source and climate impact directly from the ice core fingerprint. In the final phase of this project, we will apply our new techniques to unravel the source and climate impacts of the greatest eruptions in the ice core archive. Many of these are mystery eruptions, where we know there was a massive sulfur emission, but we don't yet know the exact volcanic source. Understanding the source of these massive mystery eruptions is one of the outstanding challenges in volcanology and paleoclimate, and our techniques will undoubtedly provide fascinating insights into these exceptional events and stimulate new interactions between volcanologists, climatologists, and historians. This project will provide critical new information about volcanism on Earth. To ensure maximum impact we will embed these findings in global volcanic hazard databases which will be used by scientists, governments, and industry (e.g., aviation and insurance) to quantify the magnitude, frequency and style of past eruptions and improve forecasts of future volcanic events. Our work will provide fundamental insights the climate impacts of past eruptions and will also help scientists and policy makers to target volcano monitoring in regions of the globe that are prone to large volcanic events. Ultimately, with this knowledge we will be better prepared for the next 'big one' and this will help limit the loss of life and reduce the economic losses.

To design complex products, engineers need to consider and optimise many different attributes. In aerospace, optimisation mainly considers both structural (e.g. displacements, accelerations) and fluid (e.g. pressures acting on a body) attributes. One of the main factors which can impact performance is product shape, which affects a number of disciplines. When changing the shape of the design the options are to change the analysis model (i.e. a mesh) or the geometry model which represents the design. The preferred option is to optimise the geometry model as the result is integrated with the wider design enterprise (e.g. it can also be used for manufacturing considerations). This is particularly true if the geometry model is a feature based CAD model (e.g. Catia V5 or Siemens NX). In a feature based CAD system, the object shape is modified using the parameters which define the features that make up the model itself. One challenge is that the variables which define the shape of the design and control how it can change, may not actually be well suited for the disciplines driving the optimisation. This means that regardless of how much effort the optimiser puts in, it will not be possible to reach a truly optimum design. This three year project will ensure the parameterisation is suited to optimisation by investigating robust methodologies to automatically insert new features into the CAD model, for which the associated parameters will be new optimisation variables. This will rely on robust and efficient new methods for computing multi-disciplinary sensitivities. The project benefits from collaboration with a major UK industrial partner (Airbus) and developers of key analysis software (DLR). They will assist in researching a new capability with the overall aim of "delivering a step change in the configuration, time to market and performance of new designs." The following objectives have been set: 1. Implement strategies for improving CAD parameterisations for multi-disciplinary optimisation by automatically inserting features into the model based on sensitivity. 2. Investigate efficient and robust methodologies for computing aero-structural sensitivities. This will see a novel approach to the calculation of the sensitivities. 3. Develop strategies for coupling and coherently meshing solid and fluid models. This is a key piece of research required in any aero-structural analysis. 4. Combine aero-structural sensitivities with CAD parameterisation strategies, in an automated optimisation framework, for a range of test cases. This is where the benefits of the work will be demonstrated to industry. 5. Quantify the decrease in time to market and increase in performance due to this research. Application areas for this research include the design of products which require the optimisation of complex shapes. It will be particularly relevant in industries where feature based CAD systems underpin the design process, and where the physics of the problem may identify the need for shape features which may not be apparent when the CAD models are being setup. An example may be where the surface sensitivities suggest the need for a winglet, but where the parameterisation of a basic wing does not include the parameters to allow such a feature to form. Benefits include: 1. the ability to discover new, optimum, configurations. This is a route to innovative design solutions which will help to keep the UK as a world leader in the design and manufacture of complex products; 2. improved product performance due to the improved optimisation variables (CAD parameters) created based on the requirements of the physics of the problem. For air travel this will result in more environmentally friendly aircraft and lower travel prices; 3. reduced development times due to an automated and efficient optimisation processes, leading to new, better performing, products being available sooner;

Noise and emissions (carbon dioxide and nitrogen oxides) from jet engines are a major issue, with public expectations of quieter and cleaner skies, despite the rapid growth in commercial air transportation. Research on aircraft noise is of major importance to many stakeholders in the UK. London Heathrow enforces some of the most stringent noise regulations of any of the world's major city airports. Also Rolls-Royce, one of the UK's premier engineering companies, currently has a 30% share of the civil-engine market, making it the world's second largest supplier of civil aircraft engines. In addition to the economic benefits, reducing aircraft noise and emissions also benefits society, improving the quality of life, and in some instances the health, of people living and working near airports. One of the principal aims in the ACARE (Advisory Council for Aeronautics Research in Europe) 2020 vision is a 50% reduction in perceived average noise levels. Notwithstanding the significant investment in aircraft noise research in Europe and the U.S. during the last two decades, this vision will still require considerable technological advances to make airplanes substantially quieter. The key application of the majority of research in aeroacoustics is aircraft noise. Spectral broadening refers to the scattering of tonal sound fields by turbulence, whereby the interaction of the sound with a random, time-varying, turbulent flow results in power lost from the tone and distributed into a broadband field around the tone frequency. When the proportion of scattered power is small relative to the power that remains in the tone, this is termed "weak scattering". However, spectral broadening can lead to the disappearance of the tone itself, replaced by a broadband hump: this is termed "strong scattering". The advent of the high-bypass-ratio turbofan engine led to a significant step-change reduction in noise from jet engines, principally due to lower levels of jet noise. A consequence of this reduction in jet noise was that, relative to other sources, fan, core and turbine noise became more important noise sources. In turbofan engines, spectral broadening occurs due to the aft radiated sound propagating through the exhaust jet shear layers. This affects the radiation of turbine tones, and to a lesser extent fan tones. It is likely that in order to generate another step-change reduction in aircraft engine noise, radical changes to the engine's design will be required. Currently advanced open-rotor contra-rotating propeller concepts are being reappraised due to the significant fuel efficiency savings they can provide. However open-rotors generate a multitude of tones, and historically they have been perceived as being noisier compared to turbofan engines. Open-rotor noise testing conducted in free-jet wind-tunnels can be affected by the presence of the wind-tunnel jet shear layers through which the sound propagates because open-rotors generate highly protrusive tonal sound fields. The shear layers cause spectral broadening of the tones. The development of robust, validated prediction methods (theoretical and computational) will be a key output from this research. The capability to predict strong scattering is the key aim; currently there are no prediction methods available to predict strong scattering of tones from turbofan and open-rotor aircraft engines. The acquisition of a model-scale experimental database of measurements of spectral broadening obtained in the laboratory will be the other key output from this research. There is currently no such database available; the data will be used for validation purposes, as well as to improve our understanding of the scattering phenomenon. In summary, the research project will be the first comprehensive study on spectral broadening in aeroacoustics, with key applications directly linked to noise emissions from both turbofan and open-rotor aircraft engines.

BACKGROUND In the last fifty years aviation has experienced very rapid development, with air traffic recording an almost 9% yearly growth rate in the first half of the period (approximately 2.5 times the average GDP growth rate) and approximately 5% yearly growth rate in the second half of the period. According to the most recent estimates, aviation climatic impact amounts to 2-8% of the global radiative forcing associated with climate change. As a result of the expected increase in air traffic in the next decades, the relative importance of air traffic on climate change is expected to increase significantly. THE NEED FOR COSIC AND AIMS One of aviation's largest effects is likely to be that due to contrails and their spreading into cirrus. This could be considerably larger than the effects of increased CO2 emissions but this contrail-cirrus remains unquantified. Previous estimates of combined aviation induced cloudiness suggest that spreading contrails could be important. However, these studies rely on correlating air traffic with cirrus coverage and have large uncertainties and methodological problems. The ultimate aim of this proposal is, for the first time, to build a physically based parameterisation of contrail-cirrus - to determine its role in climate change, testing whether it has a larger role than line-shaped contrails. To achieve this ultimate goal, observations of contrail properties and their spreading will be made with FAAM (research aircraft) flights and satellite observations. Then a hierarchy of models will be used to develop a contrail-cirrus cloud parameterisation within the Met Office Unified Model, working closely with both the Met Office and the Deutsches Zentrum für Luft- und Raumfahrt (DLR) partners, and constraining the developed parameterisations by the observations made by University of Manchester and Met Office researchers during the aircraft campaign. WORKPLAN WP1 will perform an aircraft campaign making 6 'case study' observations of spreading contrail during 2009 in an area out of the flight corridor to the southwest of the UK . We will use a novel 'figure of eight' flight pattern to make and monitor our own contrail and, in particular, track its evolution into cirrus. We will measure its radiative forcing by flying cross sections above and below and by monitoring from space using the GERB and SEVIRI geostationary instruments. We will make use of state-of-the-art observations made by the Met Office and University of Manchester groups. We will also rely on ice supersaturation forecasts supplied by the University of Reading group using European Centre forecasts. WP2 will use idealised modelling data supplied by DLR and the detailed observations made during WP1 to simulate specific case studies observed during the aircraft campaign. Particular attention will be made to the later stages of contrail lifecycle. WP3 will again make use of idealised DLR data and our own (and others) case-study data to build a prognostic contrail-cirrus scheme for the Met Office Unified Model. WP4 will employ the Unified Model with this parameterisation to predict the radiative forcing and climate impact from contrail-cirrus, comparing its climate impact to that estimated for line-shaped contrails.