1. Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, IN 47906 , USA.
2. Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA.
3. Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO 80307, USA.
4. Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada.
5. International Arctic Research Center and Department of Atmospheric Sciences, University of Alaska Fairbanks, Fairbanks, AK 99775, USA.