Saharan Mineral Dust Experiment (SAMUM) 2006: Vertical Profiles of Dust Particle Properties from Airborne in situ and Lidar Observations

Kurzfassung

The Saharan Mineral Dust Experiment (SAMUM) is an initiative of several German universities and research establishments. Its goal is the characterisation of optical, physical, chemical, and radiative properties of Saharan dust close to a source region. The SAMUM intensive field phase was carried out in May/June 2006 in Southern Morocco. The DLR Falcon research aircraft was operating from Casablanca. The DLR Falcon was equipped with an extensive set of aerosol physico-chemical instruments for size, volatility, and absorption measurements, impactor sampling for chemical analyses and with a nadir-looking high spectral resolution lidar (HSRL). In total eight mission flights were conducted from the Atlantic coast across the Atlas Mountains to the border of the Saharan desert where the ground sites Ouarzazate and Zagora were located, and from Morocco to Portugal. Three large-scale dust events were probed which extended from southern Morocco to Portugal. Vertical (0 - 10 km) and horizontal (Saharan border to southern Portugal) dust plume structures, aerosol optical depth as well as particle microphysical and optical properties were studied for all cases. The upper boundary of the dust layers was found at altitudes between 4 and 6 km above sea level and coincided with the top of the well-mixed boundary layer. The internal structure of the dust layers varied from well mixed to stratified. Figure 1 shows averaged vertical profiles of aerosol number concentrations measured during SAMUM. Note the sharp upper boundary of the dust layers. Figure 2 shows an example for a dust size distribution measured at 3870 m above sea level close to the top of the dust layer. Extinction coefficients calculated from the size distribution and measured with the HSRL agree within 15%. Presented results will cover profiles of dust size distributions and dust optical properties. Expected heating rates and their impact on atmospheric stability will be discussed. This work was supported by the Deutsche Forschungsgemeinschaft DFG, the European Space Agency ESA and the European Fleet for Airborne research EUFAR.