1. Experimental Studies Division; Air Quality Research, Meteorological Service of Canada; Downsview, Ontario Canada
2. National Ultraviolet Monitoring Center, Department of Physics and Astronomy; University of Georgia; Athens Georgia USA
3. Goddard Earth Sciences and Technology Center; University of Maryland Baltimore County; Baltimore Maryland USA
4. NASA Goddard Space Flight Center; Greenbelt Maryland USA
5. Finnish Meteorological Institute; Helsinki Finland