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North Africa is the world’s largest source of dust, a large part of which is transported across the Atlantic to the Caribbean and beyond where it can impact radiation and clouds. Many aspects of this transport and its climate effects remain speculative. The Saharan Aerosol Long-Range Transport and Aerosol–Cloud-Interaction Experiment (SALTRACE; www.pa.op.dlr.de/saltrace) linked ground-based and airborne measurements with remote sensing and modeling techniques to address these issues in a program that took place in 2013/14. Specific objectives were to 1) characterize the chemical, microphysical, and optical properties of dust in the Caribbean, 2) quantify the impact of physical and chemical changes (“aging”) on the radiation budget and cloud microphysical processes, 3) investigate the meteorological context of transatlantic dust transport, and 4) assess the roles of removal processes during transport. SALTRACE was a German-led initiative involving scientists from Europe, Cabo Verde, the Caribbean, and the United States. The Falcon research aircraft of the Deutsches Zentrum für Luft- und Raumfahrt (DLR), equipped with a comprehensive aerosol and wind lidar payload, played a central role. Several major dust outbreaks were studied with 86 h of flight time under different conditions, making it by far the most extensive investigation on long-range transported dust ever made. This article presents an overview of SALTRACE and highlights selected results including data from transatlantic flights in coherent air masses separated by more than 4,000-km distance that enabled measurements of transport effects on dust properties. SALTRACE will improve our knowledge on the role of mineral dust in the climate system and provide data for studies on dust interactions with clouds, radiation, and health.

Abstract:A special in situ PEM fuel cell has been developed to allow X-ray absorption measurements during real fuel cell operation. and electronic (atomic XAFS) structure of the anode catalyst, are monitored as a function of the current. In hydrogen, the NPt-Ru coordination number increases much slower than the NPt-Pt with increasing current, indicating a more reluctant reduction of the surface Pt atoms near the hydrous Ru oxide islands. In methanol, both O[H] and CO adsorption are separately visible with the ∆µ technique and reveal a drop in CO and an increase in OH coverage in the range of 65-90 mA/cm 2 . With increasing OH coverage, the Pt-O coordination number and the AXAFS intensity increase. The data allow the direct observation of the preignition and ignition regions for OH formation and CO oxidation, during the methanol fuel cell operation. It can be concluded that both a bifunctional mechanism and an electronic ligand effect are active in CO oxidation from a PtRu surface in a PEM fuel cell.