Navy Global Environmental Model (NAVGEM)
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Monday, 3 February 2014: 5:15 PM
Room C201 (The Georgia World Congress Center )
The Navy Global Environmental Model (NAVGEM) is a high-resolution global weather prediction system representing a significant milestone in the Navy numerical weather prediction (NWP) system development introducing a semi-Lagrangian/semi-implicit (SL/SI) dynamical core with advanced moisture and ozone physical parameterization schemes. The SL/ SI method enables high-resolution needed for modern NWP system while still meets the operational scheduling requirement The development represents the most significant Navy global numerical weather prediction advancement over the past 20 years. The SL method is to find the trajectory of the fluid motion that starts at the previous time step and ends up at the NAVGEM grid point location. The SL integration removes the Courant-Friedrichs-Lewy (CFL) limitation required in the Navy Operational Global Atmospheric Prediction System (NOGAPS) using the conventional Eulerian integration of the dynamical equations. The remaining issue of high-speed gravity waves in the wind divergence is mitigated by incorporating a SI method into the SL integration, where the terms responsible for the high-speed gravity waves are treated in an implicit manner so that small time steps are not needed.
Replacing the existing NOGAPS introduced in 1982, NAVGEM allows for higher model resolutions without the need for small time steps (currently 50 vertical levels in place of the 42 levels in NOGAPS and an increase of horizontal resolution from 42 kilometers to 37 kilometers) to include cloud liquid water, cloud ice water, and ozone as fully predicted constituents. NAVGEM contains new moisture, solar radiation and longwave-radiation parameterizations and upgrades to the data assimilation component to complete the 180-hour forecast in the allotted operation window.
NAVGEM was delivered to the Navy Fleet Numerical Meteorology and Oceanography Center (FNMOC) on September 30, 2012, and made its official operation in March 2013. Performance of NAVGEM and future development will be presented.