Stratospheric Forecasting with NOGAPS-ALPHA
NAVAL RESEARCH LAB WASHINGTON DC
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A new high-altitude version of the Navy Operational Global Atmospheric Prediction System NOGAPS is described and used to hindcast the unusual 2002 Antarctic stratospheric major warming. The new version, called NOGAPS-Advanced Level Physics with High Altitude NOGAPS-ALPHA or NOGAPS-alpha includes modifications to multiple components of the operational version, including the radiation scheme, gravity wave drag, vertical coordinate, and meteorological initialization. It also has a raised model top from 1.0 to 0.005 hPa and radiatively active prognostic ozone with parameterized photochemistry. A detailed comparison of the major warming period September 2002 is done with operational NOGAPS NOGAPS-op, operational ECMWF, and NOGAPS-alpha stratospheric forecasts. We examine the synoptic evolution of the middle stratospheric polar vortex as well as wave propagation diagnostics. The NOGAPS-op forecasts showed weaker wave activity compared to the analysis, which resulted in poorer predictions of the split stratospheric vortex. The situation improved in NOGAPS-alpha forecasts initialized with NOGAPS operational analyses, with stronger wave amplitudes and better forecasting of the split vortex. More significant improvements were found when NOGAPS-alpha was initialized with the ECMWF analyses, prompting plans for a NOGAPS reanalysis of this period.
- Atmospheric Physics