Atmospheric dust from Sahara vertically aligned due to electric fields, may need to adjust climate models for this effect on aerosols

Unexpected discovery could impact on future climate models

February 10, 2009 (PhysOrg.com) -- Astronomers have made an unexpected find using a polarimeter (an instrument used to measure the wave properties of light) funded by the Science and Technology Facilities Council (STFC), that has the potential to affect future climate models.

University of Hertfordshire astronomers were making observations of the stars in search of new planets after mounting the 'PlanetPol' (polarimeter they designed and constructed to take extremely sensitive readings) on the William Herschel Telescope (part of the Isaac Newton Group of Telescopes) in La Palma in the Canary Islands, when their measurements became affected by a layer of dust.

The presence of the dust itself, which satellite images and modelling of the dust's movement show had originated from the Sahara and the Sahel, was not a surprise, but its behaviour was. Scientists normally assume that aerosols, including mineral dust, have random orientation in the atmosphere, but the team members say the polarizing affect the dust was having on the light could only be the result of dust particles being vertically aligned.

Furthermore, electric fields that are now thought to be responsible for this phenomenon are likely to affect the transport of dust over long distances. For the first time this might explain why large Saharan dust grains can travel as far as the UK instead of falling to the ground long before.

This could impact on climate theories because atmospheric dust is a significant source of uncertainty for scientists trying to model the climate. 'If it's proven the dust is affected by electric fields, elements of current climate models may have to be re-worked with this new information, to remain accurate', explains Joseph Ulanowski, Centre for Atmospheric and Instrumentation Research (CAIR) at the University of Hertfordshire.

Climate models are extremely complex and involve many other influences, so further research will now be carried out to see how significant a find this dust phenomenon is. CAIR will now join a Met Office-led campaign in the Middle East in the spring 2009 which presents an opportunity to investigate this further.

Professor James Hough, Director of Astronomy Research at the University of Hertfordshire said, 'It's been fascinating to see how we have been able to use astronomical observations to learn far more about dust in the Earth's atmosphere, especially as we first considered the Saharan dust event to be a real nuisance and of no value to us at all.'

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