The Effects of the Horizontal Resolution of the Boundary Forcing Sea Surface Temperature Field on the FSU Spectral Model
2006
Hickel, Brent D.
This study examines the effects of higher wavenumbers in the boundary forcing sea surface temperature field (SST) on the output from an atmospheric model. The model is the FSU global spectral model employing triangular truncation at 170 wavenumbers for a horizontal resolution of .7 deg latitude by .7 deg longitude. Boundary forcing is provided by a fine scale SST, a smoothed version of that SST and a combination field where a region bounded by 200 deg N to 55 deg N by 120 deg E to 150 deg E from the fine scale SST is patched into the smoothed SST field. The results indicate that inclusion of higher wavenumbers in the boundary forcing SST significantly impacts the behavior of the atmospheric model. The areas downstream from regions of strong spatial gradient in the SST field, such as the Kuroshio and Gulf Stream have the largest differences. Geopotential height differences at 500 mb between the fine and smoothed SST model runs are as high as 230 meters. Pacific typhoon intensity is better modeled using the high resolution SST. The boundary forcing becomes increasingly important as the model integration progresses. The effects of the initial atmospheric conditions are tested and are clearly smaller than the impact of the fine scale SST. It is conjectured that medium range, 5-14 day forecasts will be greatly improved if the best resolution observed SST is used. We conclude that coupled ocean-atmosphere models will be negatively impacted if a low resolution ocean model is coupled to a higher resolution atmospheric model
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