S222 Thermally Forced Gravity Wave Disturbances over the Amazon Using Realistic Background States

Sunday, 12 January 2020
Angela Mary O'Flanagan, St. Cloud State Univ., St. Cloud, MN; and C. C. Epifanio, C. Schumacher, and H. Bai

Heavy precipitation occurs over the Amazon basin, but is disconnected from coastal convection. Observed wind profiles across the Amazon also resemble a theoretical gravity wave structure forced by an idealized background state and diurnal heating. The hypothesis of this work is that gravity waves forced by heating at the coast could impact the inland convection. In this study, wave responses are simulated in a simple 2-D model forced by ERA5 background flow. ERA5 shows a nocturnal low-level jet whose inland extension is maximized during March, April, and May. This jet acts as part of the realistic background flow for the model. Additionally, an oscillating heat source is needed to force the model. ERA5 boundary layer heating flux acts as realistic diurnal heating at the coast, giving the required forcing component. The 2-D linear and nonlinear model is forced by the realistic background state and diurnal heating at the coast. The resulting steady state wave response will be analyzed and compared to the output of simple theoretical solutions. The thermally forced wave solutions are expected to show evidence of the low-level jet and stability changes related to the timing of convection in the central Amazon.
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