[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