Abstract:

    The Advanced Regional Prediction Systems (ARPS) forecast model is extended up to the stratopause and over the entire hemisphere to simulate gravity waves during 24 January 2005. With a 15-km (0.4-km) horizontal (vertical) resolution, the simulation produces realistic gravity wave features related to geostrophic adjustment of tropospheric jet and topographical flow over the Greenland terrain, when a near-surface high pressure system is present over the North Atlantic. In the stratosphere, wave signatures appear near the region of strongest flow in the polar vortex, where negative vertical flux of horizontal momentum is pronounced. Flux divergence associated with horizontal flow acceleration of 12-120 m s-1 day-1 coincides with areas of depleted stratospheric wind speed, suggesting strong interactions between gravity waves and the polar vortex. Simulated temperature wave perturbations compare favorably with radiance perturbation from NASA AIRS observations. Coarser simulation using 50-km horizontal resolution produces gravity waves of significantly weaker amplitudes.

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