Hui Liu is a Visiting Associate Research Scientist who joined ESSIC in October 2017. Before that, he was a Project Scientist at the National Center for Atmospheric Research from 2003 to 2017 and a Research Associate at Florida State University from 1998 to 2003. His work focuses on improving assimilation of GPS radio occultation data in the tropical lower troposphere, including developments of physics-based quality control and dynamic errors of the radio occultation data. Dr. Liu got his Ph.D. from the Chinese Academy of Sciences in Beijing in 1993 and moved to U.S. in 1998. He is currently working on the CICS-MD task supporting NOAA COSMIC2 data, products and algorithms with Xiaolei Zou.