Worldwide weather events cause ripples in the UK

Hannah and her team want to share their science with GCSE and A Level students to show potential climatologists and meteorologists that studying Physics could help their future careers. The Physics in Action website and its linked animation, Weather and Climate Science is Physics in Action, demonstrate how Physics plays an important part in solving real-world problems related to weather forecasting.

Our David Richards Tutorial Fellow in Physics and Associate Professor in Physical Climate collaborated with colleagues in Reading University and the Met Office on research that will improve the Met Office’s weather predictions. While acknowledging that such things are very uncertain, the three-year NERC (Natural Environment Research Council)-funded project aimed to do this by building a better understanding of the physics of extreme weather events, which can have impacts far beyond their immediate location and reach as far as other countries, including the UK.

While such intense weather conditions are quite rare in the UK, they are common in other regions, including the USA. The ramifications of these events can be extensive, reaching as far as the UK from the US. Hannah and her team were interested particularly in very large and energetic thunderstorm systems. These systems are vastly different from the small, individual thunderstorms that happen typically in the UK that bring heavy rain but, at about 10 kilometres wide, are relatively small. The systems that form often in the USA comprise many individual thunderstorms that organise themselves into enormous systems and feed off each other. They enable each other structurally to persist for a long time, so you can have systems that are hundreds of kilometres wide and can live for up to 12 hours, bringing huge amounts of very severe rainfall.

These systems are quite difficult to represent in a weather-forecast computer model. The team wanted to improve their understanding of some of the physics of the system – what properties of the atmosphere can predict when and where the thunderstorm systems form and how they affect the rest of the atmosphere, so that they could encode this into their computer model. One of the reasons this is important here in the UK is that these systems are so big and energetic that they affect the weather around the whole world. They cause what Hannah describes as ripples on the jet stream, which can affect the weather in the UK. As part of the project, the team worked out can predict whether these systems will form. They worked out the impact that the systems have in terms of how they change the rest of the atmosphere, and encoded it into the model, from which they have seen that the accuracy of forecasting has got better.

Hannah and her team worked very closely with the Met Office on this project. From the start, all the development was done using the Met Office’s model. Project team members from the Met Office ran a pre-operational trial using their standardised testing suite, so that they could see if, in that very realistic setup, there was an improvement.

The whole project was formulated in such a way that acknowledged that these things are very unpredictable. It is uncertain if the systems will form – or not – so, if they do, the impact they will have is unclear. Hannah and her colleagues wrote all the code in a very probability-oriented way. From there, they discovered that without the changes they had made, the model would be very confident about an incorrect prediction. After implementing the changes, the model acknowledged the uncertainty due to these extreme thunderstorm systems, and in terms of the prediction, it became more accurate. So, by putting in the cause of the uncertainty, its confidence was attuned and became more realistic and reliable. Ultimately, it helps the weather prediction models to be less overconfident.

The team wanted to share these findings with young people who are interested in future careers in this field. The project included an element of public outreach, which led to the development of the Physics in Action website. Aimed at GCSE students who are considering their A Level choices, this resource shows how Physics plays an important part in solving real-world problems related to weather forecasting. The website and its linked animation, Weather and Climate Science is Physics in Action, will help students to explore their options and the subjects that will provide a good foundation for careers in this area.

Many students who are interested in environmental issues may believe that Physics is not for them, and discount it in favour of other subjects such as Geography or Chemistry. Physics in Action demonstrates the value of Physics and Maths A Levels to potential climatologists and meteorologists and shows why they should consider them for A Levels and beyond. Researchers and scientists in Oxford University’s Department of Physics who want to communicate their work to students will continue to develop the website, adding articles to share their science and signposting students to further information on these topics, including the Met Office’s resources. We hope that students and their teachers will find it useful.