10 August 2016

A Lancaster undergraduate’s dissertation on how rainfall patterns are changing, challenges conventional wisdom and lands him a coveted prize.

Ethan Wallace is fascinated by weather and water - so he jumped at the chance to research how extreme rainfall events have changed over the past 40 years for his final year dissertation at the Lancaster Environment Centre.

“Hydrology and meteorology are my favourite subjects. I love the real world applications: I can learn something about clouds in a lecture, and look out of the window and see it happening right in front of me,” said Ethan, who has now graduated with First Class honours in Physical Geography.

For his dissertation, Ethan tracked rainfall data from two long running weather stations - one at Hazelrigg just behind the Lancaster University’s campus, and another at Dolydd in west Wales. He assumed that climate change would mean we are suffering more frequent and intense downpours.

But when he looked at his results he found that extreme downpours - in the top two percentiles - were actually decreasing in intensity. It was only the most extreme events - the top 0.5 percent, that were actually getting worse.

Surprising results

“At first I thought I had done it wrong. It was not what I expected,”  said Ethan. “We always hear that with global warming and climate change, extreme events and their intensity are increasing. But this didn’t fit that trend.”

So he checked and rechecked to make sure his results were both accurate and statistically significant.

After talking over his results with co-supervisors Dr Wlodek Tych and Dr Nick Chappell, he decided to try to find what was causing these unexpected rainfall patterns.

One of the tools he used was the Captain Toolbox, a Computer aided programme for time series analysis and identification of noisy system, co-authored and largely developed by Wlodek.

“It was incredible to use Captain Toolbox and have one of the designers sitting next to me working on it also,” said Ethan. 

So he looked at the North Atlantic Oscillation (NAO) - the difference in atmospheric pressure at sea level between the Icelandic low and Azores high - to see if the NAO correlated with the rainfall patterns he had found. Again his results surprised him.

“If the NAO was high you would expect there to be more extreme rainfall, but my results showed the opposite. Basically it was telling us that the NAO isn’t driving this rainfall - even though a lot of the scientific literature recently has been saying that the changes are due to the NAO.”

Winning prizes

Ethan’s dissertation setting out his results won two Lancaster Environment Centre’s prize including the first Keith Beven Hydrology undergraduate dissertation Prize, awarded in honour of the world’s top hydrologist, who was a Professor in the Environment Centre at Lancaster before his retirement.

“It was amazing to be receiving a prize from one of the world’s most cited hydrologists. Both Keith Beven and Nick Chappell are literally at the forefront of global hydrology. It also helps having the Centre for Ecology and Hydrology based at Lancaster.”

Wlodeck, Ethan’s dissertation supervisor, praised Ethan’s hard work, energy, and passion for science. He believes that undergraduate dissertation projects, which all students undertake, are a great learning opportunity.

“We are able to encourage the students to think and work independently, while working with scientists of international standing on topics which are within their current research focus.  This builds their skills and interests as well as their professional confidence.”

“Brilliant” interdisciplinary teaching

Ethan is equally appreciative of the quality of the teaching at Lancaster. “The lecturing at Lancaster is brilliant. I have never had a lecturer that I didn’t like or who wasn’t helpful. They make lectures really fun and, if there  is something you don’t understand, they will help you out of hours”.

He enjoyed the interdisciplinary approach at the Lancaster Environment Centre, enabling him to study law and history relevant to his subject alongside the natural sciences, which meant he never got bored. 

Ethan is now working with Wlodek Tych and Nick Chappell doing further research on the Dolydd data, to see if the local weather systems can explain his results. They hope to submit a paper to either Nature or Science, two of the world’s top scientific journals. Ethan then hopes to stay at Lancaster University for a PhD.

His dissertation has been entered for the prestigious British Hydrological Society dissertation prize.

Find out more about studying at Lancaster Environment Centre.