Thursday, 15 January 2004: 8:30 AM
The Navy Operational Global Atmospheric Prediction System: Current status and testing of convective momentum transport in the Emanuel cumulus parameterization
The Navy Operational Global Atmospheric Prediction System (NOGAPS) is the U. S. Department of Defense's high-resolution global weather prediction system, which is used for operational medium range weather prediction, forcing for operational mesoscale and oceanographic models, and numerical weather prediction research. Recent changes to the forecast model component of the system include an increase in horizontal resolution to a triangular truncation of 239 waves, an increase in vertical resolution to 30 levels, a new cloud scheme, and modifications to the Emanuel cumulus parameterization, which increase parcel buoyancy, include effects of ice, and increase the convective momentum transport. Data assimilation results will be presented which document the increase in forecast skill of the various changes, especially in the tropics. In particular, results will be presented that demonstrate that the increase in convective momentum transport resulted in (1) improved tropical lower level winds, (2) improved tropical cyclone track forecasts, (3) reduction in the number of false alarms for tropical cyclones, and (4) a reduction in the central pressure deficits for tropical cyclones. Additionally, sensitivity tests will be presented showing the impact of the parameters controlling the convective momentum transport in the Emanuel cumulus parameterization.