Dust Radiation, Electrification and Alignment in the Middle East (DREAME)

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Mineral dusts in the atmosphere, originating primarily from dry regions like the Sahara desert, have significant influence on climate. Because of this they need to be accurately represented in climate and weather prediction models. Recent observations of atmospheric Saharan dust by UK scientists provide strong evidence for the existence in mineral dust layers of particles that are predominantly vertically aligned. This alignment is thought to be due to atmospheric electricity associated with the dust layers. Computer modelling indicates that the alignment can significantly change the properties of the dust layers, including the amount of light they transmit, absorb and reflect. This has been termed a 'Venetian blind effect' from the way the tilted particles influence the amount of transmitted light and heat. Change in this and other properties can have significant impact on measurements of dust clouds from satellites, and possibly also on dust movement through the atmosphere. The proposed project will answer urgent questions concerning the precise origin, magnitude, extent and impact of this phenomenon by the use of a variety of measurements from the ground, balloons and aircraft, carried out in the Middle East. The project will result in improved understanding of dust and has the potential to solve a long-standing enigma concerning the movement of dust clouds on the continental scale. The proposal takes advantage of a major opportunity offered by the UK Met Office MEVEX flight campaign, to carry out this project at little additional cost. Therefore it provides excellent value for money.