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Last Update: 2007-07-06   Source: Star Projects
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Weather Detectives

The research to make forecasts more accurate is becoming increasingly important as catastrophic weather events rise in frequency. European scientists are working toprovide Europeans with earlier weather alerts.

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In August, 2002, a week long of heavy rain sent water surging through the rivers of Germany, Russia, Austria and the Czech Republic. Thousands of people had to be evacuated and at least 90 people died. In Dresden, Eastern Germany, the level of the river Elbe rose to more than 9 metres, breaking all existing records since the 16th century.

The European Centre for Medium Range Weather Forecasting (ECMWF) in Reading, England, uses the technique “ensemble forecasting” to improve accuracy in their forecasting. Rather than a forecast being based on one simulation, 50 simulations are run, each with slightly different initial conditions. A forecast where all simulations agree is one in which much confidence can be placed. Variations in the forecast means uncertainty, but if severe weather is predicted in 20 out of the 50 forecasts then it is still valuable as a warning of the risk of a dangerous weather event.

There are always uncertainties in the initial observational data. A tiny difference in the data can sometimes dramatically alter the entire forecast. It could mean the difference between a mild day with a bit of westerly wind and a severe weather event.

The influencing factors in forecasting stretch beyond continents and political borders. The plan is to link world weather centres to achieve global forecasting. This is being realised through the SIMDAT Project, which gives users access to data from across the world. At the ECMWF relevant data sets are collected and stored on their network, ready for retrieval.

Another project assures for the efficient transfer of the vast amounts of information (hundreds of gigabytes) required for global forecasting. Geant2 is a high speed information network using optical fibres. It provides a fast delivery mechanism for the meteorological world.

In Dresden dikes provide protection for part of the outer city, but the inner city requires a stronger defence. The Dresden Flood Protection Task Force plans to use the old city wall as a base to a sandstone construction, which will protect the inner city up to a water level of 9 metres. If the Elbe rises even higher mobile barriers will be put into use. However, this takes time to build and an early warning system remains a vital part in preparation against flooding. Just a few kilometres away in the narrow river valley, in which Bad Schandau is located, flood barriers are not an option. Here an early warning is the one and only defence.

Experts say that the frequency and severity of extreme weather events are on the rise. The ability for society to adapt to climate change is becoming ever more reliant on forecasting. Along with the SIMDAT Project and the Geant2 network, the European Weather Centre can enable meteorologists to provide Europeans with accurate warnings of the extreme weather ahead.



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