Summit County Citizens Voice

A NASA satellite image shows a snow-covered UK in January 2010.

Modeling study suggests significant seasonal shifts in rainfall patterns

By Summit Voice

SUMMIT COUNTY — Shifts in large-scale atmospheric circulation patterns driven by global warming could lead to an increased risk of damaging floods in parts of the UK, according to a modeling study by German researchers.

The research suggests a season shift in rainfall trends, with heavier precipitation in late autumn in the south-eastern regions of the country. In the the northwest, the heaviest rainfalls will be a little earlier — in November, rather than December.

These shifts will coincide with times of the year when river catchments in those regions are at their maximum water capacity, meaning there would be an increased risk of flooding.

“In late autumn, the river catchments in the north-west reach their maximum capacity of water, as do the eastern catchments in winter,” said researcher 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.”

The researchers, from the University of Giessen and GEOMAR Helmholtz Centre for Ocean Research Kiel, investigated the future changes using 12 climate model simulations for the periods 2021-2060 and 2061-2100, each forced with the Intergovernmental Panel on Climate Change’s (IPCC) A1B scenario.

They also investigated whether the range of extreme rainfall throughout the year was set to get even greater with warming and did observe a projected increase in western regions of the UK; however, they make it clear that this finding is not robust and would need closer examination.

“There are different mechanisms that influence extreme precipitation in the two regions we’ve highlighted,” Schindler said. “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 UK has a long history of monitoring rainfall and has a large number of rain gauges scattered across the country, providing a wealth of information and making it an ideal place to study.

The study was published Nov. 21 in  in IOP Publishing’s journal Environmental Research Letters.

Filed under: climate and weather, Environment, global warming Tagged: | climate change, Environment, extreme weather, flooding, global warming, UK, United Kingdom