Prof. Giles Harrison is Professor of Atmospheric Physics at the Department of Meteorology of the University of Reading.
His research work focuses on atmospheric electricity, a topic at the intersection of aerosol and cloud physics, solar-climate and internal climate interactions, scientific sensor development and the retrieval of quantitative data from historical sources.
His research includes development of new instruments and methods, particularly for exploiting meteorological balloon technologies, and generated some of the first airborne measurements in UK airspace of Icelandic volcanic ash from Eyjafjallajökull, during the April 2010 flight ban.
He has authored or co-authored about 275 articles and papers including a book on atmospheric measurements.
Prof. Harrison holds doctorates from Imperial College London (PhD 1992) and the University of Cambridge (ScD 2014).
He received the Appleton medal of the Institute of Physics in 2016.
Professor Harrison chairs the Royal Meteorological Society’s Special Interest Group on atmospheric electricity and serves on the Editorial Board of Environmental Research Letters.
“Electrical aspects of rain generation”
Droplets even in non-thunderstorm clouds naturally carry electric charge. Recent work has shown that charges can modify the droplet growth rates. This can increase the rate at which rain droplets are formed. This research project seeks to evaluate the importance and significance of charge in affecting the cloud droplet size distribution, and with it the efficacy of modifying the in-cloud charge as an artificial influence on rainfall generation. The project follows a 3-way approach. Firstly, the team is developing an accurate computer model which can describe how large numbers of cloud drops can interact under the effect of electric forces.
Secondly, they are characterizing and measuring the local electrical properties of clouds through state-of-the-art balloon-borne sensors as well as surface measurements. Thirdly, they are deploying UAVs to demonstrate charge delivery and in-situ measurement of electrical properties of the cloud. The UK team includes theoretical meteorologist Prof Maarten Ambaum and experimental scientist Dr Keri Nicoll. They will investigate the electrical properties of clouds through a combination of theoretical and experimental work, firstly through modelling the growth of charged drops to raindrops, and secondly by measuring and modifying the charges present in clouds using balloons and aircraft. An innovative aspect is that the internal electrical properties of the clouds will be investigated using Unmanned Aerial Vehicles (UAVs) adapted to deliver charge into the clouds. A promising attribute of an electrical seeding approach is that it will leave no local environmental residues or pollution from delivery platform propulsion, as the UAVs are electrically powered.
Professor Harrison’s team is employing a combination of surface, balloon and UAV measurements, and supercomputing to fully represent the effect of turbulence on droplet growth.
In terms of the project’s experimentation, site surveys have been conducted in the UAE and the necessary measurement equipment procured, assembled and tested for its local deployment. For the theoretical aspects of the project, the UK team has developed computer codes to represent droplet growth in order to test electrical modifications of interaction between drops with associated visualization software.
Following the original project plan, the modelling and measurement capabilities are being developed in tandem to provide a theoretical understanding of droplet growth in clouds occurring with and without appreciable droplet charging. As part of the further development of the modeling strand, Professor Harrison’s team will be conducting actual “production runs” that will depict the effect of charge on rainfall formation. The bespoke UAVs will be tested and deployed as envisaged in the project proposal.
In terms of theoretical droplet modelling, and the preparation of instrumentation and measurement equipment, the project has been progressing satisfactorily.
In 2019, the first strand has delivered a novel modeling strategy which allows the team to concentrate computational resources on the precise interaction of the drops rather than calculations of the turbulence in the cloud. This work will be presented at the EGU conference in Vienna in April 2019 and is currently being prepared as a scientific publication.
For the measurement strand, Prof. Harrison’s team has been collecting data from a bespoke instrumented site at Al Ain airport. This has allowed to build a picture of some local rainfall events, in particular the moistening of air layers below the cloud in rainfall events in the UAE.
For the UAV strand, the team has been developing bespoke UAVs that allow deployment of highly sensitive electrical equipment in preparation for testing and deployment next year as planned.
Plans for aircraft work in the final year – leading to the in-cloud experimental work - have begun. The team has added a characterization of fog events, as well as the development and deployment of the flare logger, both as agreed with the UAEREP Strategic Direction Committee. In addition, a field measurement site will be set up in the UAE to provide background data on electrical characteristics of the atmosphere including dust present, which will also inform the numerical
For more information on the project please visit : https://uaeelecrain.wordpress.com/