Title: Evaluation of WRF 3/4D-Var and En3/4D-Var data assimilation methods for the antarctic applications

Authors: Qingnong Xiao, Chengsi Liu, Kekuan Chu (College of Marine Science, University of South Florida, St. Petersburg, FL)
Bill Kuo (National Center for Atmospheric Research, Boulder, CO)
David Bromwich (Byrd Polar Research Center and Atmospheric Sciences
Program, Dept. of Geography, The Ohio State University, Columbus, OH)

Data assimilation over Antarctica and the Southern Ocean faces exceptional challenges, among which the scarcity of traditional meteorological observations is the major one. However, the demanding for improved analysis and forecasting in the region increases after the International Polar Year (IPY, 2007-2008). Data assimilation technique becomes more important in order to extract the limited information in Antarctica for the atmospheric analysis. In this research, we examine the performance of WRF 3/4 dimensional variational (3/4D-Var) and the ensemble-based 3/4 dimensional variational (En3/4D-Var) data assimilation techniques in Antarctic applications. The technical details for the WRF En3/4D-Var are formulated and incorporated into WRF variational data assimilation system. We conducted two cases studies and evaluated the performances of these date assimilation techniques over a full month of October 2007 (in the IPY period). The observations collected for the study are conventional observations, Automatic Weather Station (AWS) data, GPS (Global Positioning System) refractivity and some satellite-retrieved products. WRF 3D-Var and En3D-Var assimilate one-time observational data, and WRF 4D-Var and En4D-Var assimilate observations in a 6-hour window. The domain configuration is exactly the same as the Antarctica Mesoscale Prediction System (AMPS), which has a mother domain with a resolution of 45 km and a 15-km nested domain covering all of Antarctica and the parts of the Southern Ocean. Numerical experiments indicate that each data assimilation method has its advantage and disadvantage. Based on their performance, some conclusions and insights will be summarized in our presentation.

GMAO Head: Michele Rienecker Global Modeling and Assimilation Office NASA Goddard Space Flight Center

Curator: Nikki Privé Last Updated: May 27 2011