Giles Harrison

Giles Harrison is a Professor of Atmospheric Physics in the Department of Meteorology at the University of Reading, where he has served as Head of Department several times. He is a Visiting Professor at the Universities of Bath and Oxford. His research work continues over 250 years of UK studies in atmospheric electricity, in its modern form an interdisciplinary 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.

YouTube Encyclopedic

1/3
Views:
1 261
1 685
376

Transcription

One of the remarkable things about the atmosphere is that there's a current flowing all the way from the top of the atmosphere to the ground. This is generated globally by thunderstorms and the current flows around the entire planet. Here at the University of Reading we have some sampling plates which allows us to measure it. From measurements made in the 1920s on a ship called the Carnegie it was found that this current varied over the day like this No matter where you were on the planet, there was a minimum at about 3am UT and a maximum at about 7pm UT If you think about about that happening every day this means there is a sort of heartbeat of atmospheric electricity which is running through every day as a result of the Carnegie curve. We're interested in whether this curve was actually present in clouds themselves, in other words, was there an effect of the current on the clouds through which they passed. To do that we need to go somewhere where there's very little in the way of other influences on the clouds. We went to the poles, because in the northern hemisphere and the southern hemisphere measurements are routinely made of the bases of clouds using lasers. They fire the light into the sky and measure how long it takes for the light to come back and work out the height of the cloud. We took the hourly measurements of cloud base height for these two sites and compared them with the Carnegie curve and we found that there was a variation that was very similar. This illustrates for the first time that there are changes in the clouds which we can associate with the Carnegie curve variations and the electrical currents that are flowing.

Education

He was educated at Marling School Stroud, and St Catharine's College, Cambridge. He holds doctorates from Imperial College London (PhD 1992), and the University of Cambridge (ScD 2014).^[1]

Research activity

A major part of Harrison’s work has focused on the charging of atmospheric particles and droplets and the effect of charge on their behaviour, for which he has pioneered new instruments and methods. This has included applying early atmospheric electrical data for reconstruction of past air pollution^[2] and in investigating the electrical effect of solar changes^[3] on the Earth’s and other atmospheres.^[4] His experimental work has clearly demonstrated the widespread presence of atmospheric charge in regions well away from thunderstorms, particularly at horizontal edges of layer clouds. Motivated by the need to increase in situ atmospheric measurements of these phenomena using sensitive balloon-carried instrumentation,^[5] Harrison and his co-workers have provided some unique atmospheric measurements. These include turbulence data able to be applied beyond Earth to Titan’s atmosphere,^[6] the first published airborne measurements of the Icelandic volcanic ash from Eyjafjallajökull,^[7] which were undertaken in UK airspace at government request during the April 2010 flight ban,^[8] direct evidence for unexpected enhancement of ionisation in the lower atmosphere during a solar storm,^[9] and observations of charge made opportunistically within a dust layer transported to the UK by the remnants of Hurricane Ophelia.^[10] Analysis, with co-workers, of historical weather and atmospheric electricity data from Shetland during the 1960s nuclear weapons tests, has associated this additional ionisation with increased rainfall.^[11]

Other work

Beyond atmospheric electricity and atmospheric measurements, Harrison conceived and led the National Eclipse Weather Experiment.^[12] This Citizen Science project associated with the 2015 solar eclipse involved up to 3500 pupils and teachers nationally,^[13] promoted through the BBC’s Stargazing Live.^[14] He subsequently edited a themed journal issue,^[15] bringing together new findings in “eclipse meteorology”. He also contributed to the successful campaign of the Cloud Appreciation Society to persuade the World Meteorological Organization to classify the first new cloud since 1951, asperitas, through convening an international team which suggested a mechanism for its formation.^[16]

Publications

He has authored or co-authored about 300 papers,^[17] co-edited Planetary Atmospheric Electricity ^[18] and his successful postgraduate textbook on meteorological measurements^[19] is now available in Chinese.