1. Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0314, United States
2. Department of Civil & Environmental Engineering, Stanford University, Stanford, California 94305, United States
3. Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, United States
4. Centre National de Recherches Météorologiques−Groupe d'étude de l′Atmosphère Météorologique (GAME), Toulouse, France