1 International Center for Climate and Environment Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China. chenglij@mail.iap.ac.cn.
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.