The United Kingdom is one of those places that have been studying their weather and rainfall patterns for ages, with huge numbers of rain gauges scattered all across the country. Using this wealth of information, researchers from Germany have found that as the global climate warms the time of year when the UK will receive it’s heaviest rainfall is set to shift.
The research found that between 2061 and 2100 the south-east of the country is likely to experiences its extreme rainfall in autumn rather than in late summer, while the north-east of the country will see its heaviest rainfalls a month earlier than currently.
Problematically, these changes shift the heavy rainfalls over into times when the water catchments are already at their maximum capacity, increasing the risk of flooding in the regions.
“In late autumn, the river catchments in the north-west reach their maximum capacity of water, as do the eastern catchments in winter,” said lead author of the study, Anne Schindler. “This is the time of the year when on average the most floods occur. Therefore, you can conclude that risk increases when the timing of the near field capacity and the probability for most extreme rainfall coincides.”
Schindler continued: “There are different mechanisms that influence extreme precipitation in the two regions we’ve highlighted. Extreme precipitation in the north-west is strongly influenced by westerly airflow and in the south-east the highest precipitation events are influenced by easterly flows from the North Sea.
“The shifts we have projected could be caused among other factors by changes in these large-scale circulation systems; however, this needs further investigation. For instance, we know there are deficits in the representation of rainfall in climate models and we do not know how the peak times vary from year to year without any man-made climate change.”
The researchers studied the possible changes by using 12 climate model simulations for the periods 2021 – 2060 and 2061 – 2100. They also found that the range of extreme rainfall throughout the year was expected to grow with the warming, but made it clear they were not as confident of this as they were their original discovery.