Heavy rainfall on the increase

Feb 14, 2008

Scientists at the University of East Anglia (UEA) have found that winter precipitation – such as rain and snow - became more intense in the UK during the last 100 years.

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

A previously reported reduction in heavy summer rainfall appears to have ended during the 1990s, with observations for the last decade indicating a return to more typical amounts of intense rainfall in summer.

The results will inform other work currently being carried out on flood risk and the impact of extreme weather events. As surface run-off depends on rainfall intensity and frequency, changes in intense rainfall events will impact strongly on floods.

The UEA study was funded by the Natural Environment Research Council (NERC) as part of the Flood Risk from Extreme Events (FREE) programme, which aims to improve predictions of floods minutes-to-weeks and seasons-to-decades ahead, by using environmental science to investigate the physical processes involved in generating extreme flooding events.

Using data from more than 600 rain gauges around the UK, from as far back as 1900 to as recently as 2006, Douglas Maraun, Tim Osborn and Nathan Gillett, of 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.

The work, published this week in the International Journal of Climatology, updates and extends previous studies by Dr Osborn and colleagues, using five-times as many rain gauges and looking at measurements over a longer time period.

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. For some locations 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 seven per cent 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 per cent.

Until the late 1990s, most areas of the UK had seen a decreasing contribution of extreme rainfall during the summer. The updated measurements indicate that this trend towards lighter summer rainfall reversed during the last decade, but it is too early to tell whether this new trend will continue into the future.

“So far it is not clear what causes these trends and variations. In the next stage of our study, we will be looking at possible physical mechanisms and whether man-made global warming is contributing,” explained Dr Maraun.

Source: University of East Anglia

Explore further: US delays decision on Keystone pipeline project

add to favorites email to friend print save as pdf

Related Stories

Warm US West, cold East: A 4,000-year pattern

Apr 16, 2014

Last winter's curvy jet stream pattern brought mild temperatures to western North America and harsh cold to the East. A University of Utah-led study shows that pattern became more pronounced 4,000 years ago, ...

Drying climate leads to push for water law reform

Mar 28, 2014

Despite the Water Corporation's heavy investment in desalination, groundwater replenishment and changes to groundwater management, important water law reforms are required to respond to pressure from climate change and population ...

Mongol Empire rode wave of mild climate, says study

Mar 10, 2014

Researchers studying the rings of ancient trees in mountainous central Mongolia think they may have gotten at the mystery of how small bands of nomadic Mongol horsemen united to conquer much of the world ...

Peat bog restoration work holds back water

Feb 18, 2014

Restoration of peat bogs on Exmoor has resulted in a third less water leaving the moorland during heavy rainfall compared with three years ago, a new study involving the University of Exeter shows.

Recommended for you

US delays decision on Keystone pipeline project

Apr 18, 2014

The United States announced Friday a fresh delay on a final decision regarding a controversial Canada to US oil pipeline, saying more time was needed to carry out a review.

New research on Earth's carbon budget

Apr 18, 2014

(Phys.org) —Results from a research project involving scientists from the Desert Research Institute have generated new findings surrounding some of the unknowns of changes in climate and the degree to which ...

User comments : 0

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...