Falcon investigates pollution outflow from the city of Dakar into desert dust layers

The DLR performs measurements of desert dust from the Sahara until mid of February 2008. This work is part of the Saharan Mineral Dust Experiment SAMUM, funded by the Deutsche Forschungsgemeinschaft. The measurements use the DLR research aircraft Falcon which operates from the Cape Verde Islands. On 29 January, the scientists from the Institute of Atmospheric Physics of DLR conducted a very successful research flight focusing on the entrainment of urban pollution from the city of Dakar into desert dust layers above the city. Dakar is the capital of Senegal with an area of 550 km² and a population of more than 2.5 million residents. The Falcon traversed Dakar at high altitude to measure vertical profiles of aerosol particles and water vapour in the urban plume by means of an airborne lidar system (the WALES demonstrator instrument). In a second flight sequence, the Falcon crossed the area of Dakar at very low altitude below 1 km above ground to sample the polluted air with all instruments operated on board of the aircraft. After stopover and refuelling at Dakar International Airport the team on board of the aircraft studied the mixing and processing of urban pollution and desert dust during atmospheric transport out on the Atlantic Ocean. During the entire study, Dakar was covered by a dense dust layer of 1.5 km thickness. The experiment provides important information on the impact of large cities on Earth’s climate. The Dakar case study will serve as a master copy for future experiments on climate effects of potential megacities in arid environments.