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Evaluation of High-Resolution Surface Analyses and Forecasts with Ensemble Data Assimilation in Regions of Complex Terrain
Zhaoxia PuAssociate ProfessorDepartment of Atmospheric SciencesUniversity of Utah, Salt Lake City
Despite of the importance of accurate, high-resolution atmospheric surface analyses and short-range forecasts, they remain quite difficult to produce in current research and operational practice. In this talk, I will first present recent results in the examination of errors in near-surface temperature and wind from an advanced research version of the weather research and forecasting (WRF) numerical simulations. Then, the abilities of the ensemble Kalman filter assimilation of near-surface atmospheric observations are discussed in a framework of observing system simulation experiments (OSSEs). Finally, results of data assimilation and numerical prediction experiments over the Intermountain West region with the WRF model, its 3DVAR systems, as well as an EnKF system developed by NCAR Data Assimilation Research Testbed (DART/WRF) will be presented and discussed.
It is found that: over complex terrain, forecasts not only suffer from the model’s inability to reproduce accurate atmospheric conditions in the lower atmosphere but also struggle with representative issues due to mismatches between model versus actual terrain. In addition, surface forecasts at finer resolutions do not always outperform those at coarser resolutions. Increasing the vertical resolution may not help predict the near-surface variables, although it does improve the forecasts of the structure of mesoscale weather phenomena. Results from the OSSEs indicate that the EnKF clearly performs better than 3DVAR in terms of the assimilation of near surface observations. However, the real data assimilation experiments show mixed results in some cases, implying the complexity of producing the analyses and forecasts over complex terrain and potential developments in possible future studies.
Thursday, 16 May 2013, 3:30 PMRefreshments 3:15 PMNCAR-Foothills Laboratory3450 Mitchell LaneBldg 2 Main Auditorium, Room 1022