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Last Updated: Friday, 15 February 2008, 10:04 GMT
Study into intense rain patterns
Flooded street
Rainfall study hopes to predict future floods
Intense rain has been revealed as a normal pattern of weather in the UK by a new study.

Scientists at the University of East Anglia (UEA) have found that winter rain became more intense in the UK during the last 100 years.

Similar increases in heavy rainfall are also evident in spring and, to a lesser extent, autumn.

A reduction in heavy summer downpours ended during the 1990s, and the UK has returned to more typical intense rain.

Authors of the study said their results would boost other work currently being carried out on flood risk and the impact of extreme weather.

The study aims to help improve predictions of floods by using environmental science to investigate the physical processes involved.

Extensive records

Using data from more than 600 rain gauges around the UK, from as far back as 1900 to as recently as 2006 the university's Climatic Research Unit classified every day's measured precipitation into one of 10 categories of rainfall intensity, from drizzle to a downpour.

They then analysed how the amount of precipitation in each category has changed over time.

In winter, for example, the amount of precipitation falling in the heaviest category has increased over the last 40 years in all regions of the UK.

Their classification took into account the typical differences in rainfall between summer and winter and across different regions of the country.

In parts of East Anglia, for example, heavy rain meant at least 20mm falling on a single summer day, while in winter, 10mm in a day was sufficient to reach the heaviest category.

In the north-west Highlands of Scotland, rain or snow falls of at least 30mm in summer and even 60mm in winter were the minimum required to count towards the heaviest category.

This new, more extensive study, using up-to-date records, supports the existence of a long-term increase in winter precipitation intensity that is very widespread across the UK.

In the late 1960s, about 7% of the UK's winter precipitation came from heavy rain or snow events, while in the last 10 years that figure has been about 12%.

"So far it is not clear what causes these trends and variations," explained Dr Maraun.

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