New Approaches to the Parameterization of Gravity-Wave and Flow-Blocking Drag due to Unresolved Mesoscale Orography Guided by Mesoscale Model Predictability Research
NAVAL RESEARCH LAB WASHINGTON DC SPACE SCIENCE DIV
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When surface flow impinges on orography with horizontal scales of 1-500 km, a variety of mesoscale dynamical responses can result, including gravity waves, upstream blocking, flow splitting and lee vortices. These dynamics produce important drag forces on the larger scale atmosphere. Because global numerical weather and climate prediction NWCP models under-resolve orography at these scales, all credible NWCP systems must include parameterizations of these missing orographic mesoscale drag OMD forces. Recent evidence from mesoscale model simulations clearly indicates that OMD forces cannot be described as a purely deterministic response to upstream forcing, but instead can exhibit a range of values, time histories and states. Our long-term goals are a to build these new OMD dynamics delineated from mesoscale models into a new class of OMD parameterizations, b to embed those new parameterizations within Navy NWCP systems, and c to investigate whether improved time-mean OMD and new explicit OMD variability can improve NCWP skill in Navy global NWCP systems across a range of scales.
- Physical and Dynamic Oceanography