Clear view of the clouds will bring better weather forecasts
Accurately forecasting rain will be easier thanks to new insights into clouds from the University of Leeds, UCL (University College London) and others. Details of a new model for predicting cloud and rain-formation are published today in the Proceedings of the Royal Society (10 August 2005).
Existing forecasting models – including ones used by the UKs Meteorological Office - assume rain droplets fall through still air within a cloud. However, there is turbulence within clouds that can speed up droplet settling and increase the likelihood of rain.
The international team developed a new mathematical model and showed for the first time how pockets of whirling air (tiny eddies) encourage collisions between very small droplets (about 1/1000 of a cm) and slightly larger droplets within a cloud. The collisions lead to the rapid growth of the larger drops – larger than a critical size of 20 microns ( 1 micron is a millionth of a metre). This size is necessary for rain to form, fall out of the clouds and, when conditions are right, reach the ground.
The models results were checked against earlier measurements from aircraft flying through different types of clouds. The cloud measurements showed the model was more accurate than existing ones, which often underestimate rainfall.
Leeds earth and environment research fellow Dr Sat Ghosh: "When your plane comes in to land you can see patterns formed by whirling air and sometimes feel the turbulence as you descend through a cloud. As cloud droplets descend through the smallest whirls of turbulence they speed up, causing them to collide with each other and the drops to grow, eventually getting big enough to fall as rain."
Lord Julian Hunt from the UCL department of space and climate physics (and ex-Chief Executive of the UK Met Office) said: " With this theory it is possible to explain how dust in the atmosphere, for example over urban areas or over deserts, can cause the initiation of very small droplets so that big drops do not form. This can reduce the average rain fall, but can trigger exceptionally heavy rain in very deep clouds. This may have happened recently in Mumbai and Romania.’’
Further work which will help improve weather forecasting, including the way ice crystals, water droplets and particles interact is planned.
Dr Sat Ghosh | alfa
The most recent press releases about innovation >>>
Die letzten 5 Focus-News des innovations-reports im Überblick:
Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers
Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...
Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.
At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...
3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects
A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...