Scientists at the University of Reading have discovered how to increase early warnings for fog, from around half an hour to up to two hours before it happens, by detecting changes in the atmospheric electric field.
Inland fog forms in the UK when relative humidity is high, temperatures are low and the wind is very light. Building on research that showed the role of electric charge in cloud and fog formation, scientists in the University of Reading’s department of meteorology explored two decades of weather records from the Reading University Atmospheric Observatory.
The research, now published in the Quarterly Journal of the Royal Meteorological Society, found links between a range of conditions and the observation of ‘a foggy day’ in official daily records, crucially finding a link between the air’s electric field changing and the onset of fog several hours later.
Prof. Giles Harrison, a co-author of the new study, said, “More than 160 years ago, the great Victorian scientist Lord Kelvin said he expected the atmospheric electrometer would be used as ‘a weather glass’. It has taken some time but, for fog at least, we can see that Lord Kelvin was right.”
It is hoped that the extra-early notice will help transportation planners and emergency services change schedules or issue travel advice to smooth out the many disruptions caused by fog. By using such measurements in quickfire weather alerts, known as ‘nowcasts’, forecasters could give operators of services such as airports more warning that fog is on the way.
Caleb Miller, lead researcher from the University of Reading, said, “Fog can cause disruption to airports and make driving conditions dangerous by decreasing visibility, but it is also still incredibly difficult to forecast ahead of time. Up to now, forecasters have struggled to predict precisely when and where fog may form. Our work has shown that, by observing the electrical properties of the air, which begin to change before the fog forms, we have a tool that’s able to give predictions of fog over two hours in advance, which improves on previous methods in the same situations.”
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