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Cloud modelling and ICAPS

Throughout the ages virtually every aspect of our existence has been at the mercy of the weather. Much of civilisation is based around a basic understanding of seasons and climates and this understanding has been an important factor in everything from agriculture to transport. As anyone who has ever seen a weather forecast will know, accurately predicting the weather is a tricky business; however this could all be about to change. Image of storm clouds gathering

One of the key areas of weather forecasting is understanding cloud formation; a better understanding of how the airborne molecules that make up clouds interact is crucial to our understanding and subsequent ability to understand weather and climate change, it is for this reason that cloud modelling studies have been receiving so much interest in the last few years. A lot is already known about clouds; however there are still uncertainties mainly to do with the physical changes that occur in clouds. Cloud particles are often liquid, but also often solid; and their chemical and physical properties depend to a large extent on their phase. For this reason it is crucial to accurately understand the physical properties of clouds.

Ground based modelling studies have in the past given us a rough idea of these properties, however the main thing stopping them from becoming more accurate is gravity. In the laboratory a number of clever ways have been found to make measurements, but all must make a compromise between: number of particles studied, length of experiment, and degree of contact of particles with surfaces, meaning one of these values must be guessed at and not measured; and as a consequence the measured values that depend on this guessed value are automatically less accurate.In an earth based laboratory you must either do experiments very quickly, or find a way of stabilising the cloud particle population. This is because the lifetime of the larger particles that make up part of clouds is relatively short due to gravitational sedimentation. As well as stopping sedimentation, the microgravity of space eliminates the presence of convection currents and ventilation effects as well as the effects of gravity on Brownian diffusion, simplifying the cloud models and allowing far more accurate data to be gained from these studies than is possible on earth.

Satellitle image of cloud over the United States For this reason, there has been an increasing overlap between the fields of meteorology and microgravity as people start to realise the potential of this unique environment as a way of studying aerosol and cloud processes; this has led to the development of projects such as APERO (Atmospheric Particles affecting Earth Radiative budget and stratospheric Ozone). With the development of the ‘Investigation on Interactions in Cosmic and Atmospheric Particle Systems’ (ICAPS) facility on board the International space station, it is expected that research that was previously held back by gravity will finally have the chance to develop on board the ISS.

Anything that could increase our understanding of the earths climate and the properties of airborne particles and cloud formation could have a huge impact on our day to day lives, in everything from pollution control to global warming and the flood and droughts that bring famine and suffering to the peoples of many countries around the world. It is ironic to think that research carried out in space where weather as we know it does not occur, could actually hold the key to accurate forecasting.