1. International Center for Climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
2. School of Engineering, University of St. Thomas, 2115 Summit Avenue, St. Paul, MN, USA.
3. Energy and Resources Group, University of California, Berkeley, 310 Barrows Hall, Berkeley, CA 94720, USA.
4. National Center for Atmospheric Research, Post Office Box 3000, Boulder, CO 80307, USA.