Tianfeng Chai is an Associate Research Scientist at CICS-MD and the Department of Atmospheric & Oceanic Science, University of Maryland, College Park, Maryland, USA. He got his master and bachelor degrees from Tsinghua University in Beijing, majoring in Fluid Mechanics, Engineering Mechanics, and Environmental Engineering. He earned his Ph.D. at the University of Iowa, with his dissertation of "Four-Dimensional Variational Data Assimilation Using Lidar Data" focusing on atmospheric boundary flow. He then worked with Dr. Greg Carmichael to develop chemical transport model adjoints and computational framework for data assimilation applications before moving to working on the NOAA National Air Quality Forecast Capability (NAQFC) project in 2007. He currently works on the inverse modeling problems using HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory Model) to support several projects at NOAA Air Resources Laboratory.