Qing Liang1,2, Susan E Strahan3,2, Eric L Fleming3,4. 1. NASA Goddard Space Flight Center, Atmospheric Chemistry and Dynamics Laboratory, Greenbelt, MD, USA. qing.liang-1@nasa.gov. 2. Universities Space Research Association, GESTAR, Columbia, MD, USA. 3. NASA Goddard Space Flight Center, Atmospheric Chemistry and Dynamics Laboratory, Greenbelt, MD, USA. 4. Science Systems and Applications, Inc., Lanham, MD, USA.