Xiaolei Zou is a Research Professor at ESSIC, University of Maryland. Dr. Zou, a Fellow of the American Meteorological Society, has research interests in atmospheric data assimilation, hurricanes, and climate changes. In collaboration with Drs. E. Kalnay, J. Derber, J. Sela, and M. Navon, Dr. Zou developed a four-dimensional variational data assimilation (4D-Var) system for the NMC (now NCEP) medium-range global forecast model during 1989-1993. She then developed a full-physics regional 4D-Var system for the PSU/NCAR mesoscale model (known as MM5) during 1993-1997 while she worked at NCAR as a Scientist I/II. With the help of her postdoc and a graduate student, she had also developed another regional 4D-Var system with adjoint of an explicit moist physicsfor the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS). Dr. Zou pioneered the assimilation of space-based Global Positioing System (GPS) radio occultation (RO) and surface rainfall and rain-affected radiance observations using the above-mentioned three 4D-Var systems. Other meteorological observations she investigated for data assimilation include the Total Ozone Mapping Spectrometer (TOMS) ozone, the ground-based GPS Total Precipitable Water (TPW) and zenith angle, targeted dropsondes, the National Centers for Environmental Prediction (NCEP) multi-sensor hourly rainfall, the Special Sensor Microwave Imager (SSM/I) brightness, the Atmospheric Infrared Sounder (AIRS) radiances, airborne Doppler radar data for hurricanes, the Advanced Microwave Sounding Unit (AMSU-A), Microwave Humidity Sounder (MHS), the Advanced Technology Microwave Sounder (ATMS), and the Cross-track Infrared Sounder (CrIS). In the past five years, her research was expanded to satellite data calibration, validation and assimilation for both numerical weather prediction (NWP), and climate trend study. By working closely with her graduate students and postdocs, innovative algorithms were developed for global radio frequency interference (RFI) detection for low-frequency microwave radiances, such as the Advanced Microwave Scanning Radiometer for EOS (AMSR-E), WindSat polarimetric radiometer and the Advanced Microwave Scanning Radiometer 2 (AMSR2), as well as for striping noise mitigation for ATMS and MHS radiances. A recent study by her and her colleagues found that meteorological satellite measurements of atmospheric temperature could be underestimating the long-term global warming trend by more than 40% due to clouds, which could explain much of the puzzling gap between conventional-based surface temperature and satellite-based temperature climate data records (CDRs). Another finding was that the upper troposphere might have a larger decadal warming trend than those in the low and middle troposphere based on their 30-year atmospheric physical temperature retrieval derived by a climate-applicable one-dimensional variational data assimilation (1D-Var) approach assimilating MSU/AMSU-A combined observations. Dr. Zou has published over 110 papers in refereed scientific journals on these topics.