1. Key Laboratory for Atmospheric Chemistry, Centre for Atmosphere Watch and Services; Chinese Academy of Meteorological Sciences, China Meteorological Administration; Beijing; China
2. Institute for Arctic and Alpine Research; University of Colorado; Boulder; Colorado; USA
3. Global Monitoring Division, Earth System Research Laboratory; National Oceanic and Atmospheric Administration; Boulder; Colorado; USA
4. Center for Global Environmental Research; National Institute for Environmental Studies; Tsukuba; Japan
5. School for Environmental Sciences; Peking University; Beijing; China