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Power stations behind surprising snowfalls – University of Reading

In the week the Met Office is expected to issues this winter's weather forecast, new research has revealed that humans could be playing a part in causing a different and potentially hazardous kind of snowfall.

Dr Curtis Wood from the University of Reading's Department of Meteorology (along with Prof. Giles Harrison) has concluded that emissions from industrial smoke could be the cause for sudden and probably hazardous snowfalls in their vicinities.

Snow is usually associated with low pressure systems and weather fronts and generally falls over a wide area of the country. The settled weather that brings freezing fog conditions in winter does not provide the right atmospheric environment for normal snowfalls. However, early evidence from studies of snowfalls close to smoke-stack releases in Didcot and Hereford, found that snow occurred during freezing fog conditions.

During the winter of 2006, a covering of snow fell across South-East (SE) Didcot and Central and SE Hereford, during freezing fog conditions. The proximity of these unusual weather events to active power stations, Dr Wood conjectures, could be the explanation for these examples of weather modification.

Dr Wood explains: "What was unusual about all these new snow events is that they happened in weather conditions not associated with snowfall. There were no weather fronts or clouds and they occurred in a local area of a few hundred metres, and within a mile of probable sources such as power plants.

"It is thought impossible for atmospheric ice to form near to freezing point if the air is pristine. Therefore it would appear likely that the smoke stacks provided the catalyst needed to turn liquid water into ice causing these snowfalls. Interestingly, due to the slightly warmer conditions, these new snowfalls occur as needles and not the flakes we normally see."

Studying snowfall from fog is important because of the local changes associated with it and the potential hazard it produces. Since this type of snow cannot be forecast, a hazard might arise from, for example, inadequate gritting of roads. People are also likely to get caught out by not wearing appropriate clothes or footwear.

Dr Wood added: "Another worrying effect of these anthropogenic snowfall events is that they add fuel to the fire regarding inaccurate weather forecasting. The exciting future work will be to find more cases and carry out chemical composition tests. These will tell us which metals were present at the nuclei of the falling snow and that will provide us with yet more evidence in the pathway from power station smoke to snow on the ground."

"If we can prove that power station emissions are behind this new type of snowfall, forecasters, knowing the wind direction on the predicted day of freezing fog, could potentially predict these local weather events. Any reports of snow during freezing fog conditions would be extremely useful for our ongoing research."

Dr Wood has also started preliminary research of other snowfalls that occurred during similar conditions last winter, in Hereford again and also in Gloucester and Reading. He is also examining records of similar snowfalls abroad.Please visit

>Dr Wood's website for more details

Ends

For all media enquiries please contact Alex Brannen, University of Reading Media Relations Manager on 0118 378 7338 / 07834 006243 or by email on a.brannen@reading.ac.uk

Notes to editors:

Reference: "Anthropogenic snowfall events in the UK: examples of urban weather modification?" Curtis R. Wood and R. Giles Harrison, Department of Meteorology, University of Reading, UK, October 2009 Weather© Royal Meteorological Society

The Department of Meteorology at the University of Reading is internationally renowned for its excellent teaching and research in atmospheric, oceanic and climate science. Established in 1965, it is the only UK university which offers a full range of undergraduate and postgraduate courses in meteorology.

In 2006 Meteorology at Reading was awarded the Queen's Anniversary Prize for Higher and Further Education. In the 2008 Research Assessment Exercise, 75% of the Department's research was graded as world leading or internationally excellent.