2.6 Dynamics and Predictability of Deep Propagating Atmospheric Gravity Waves

Tuesday, 6 August 2013: 11:45 AM
Multnomah (DoubleTree by Hilton Portland)
James D. Doyle, NRL, Monterey, CA; and D. C. Fritts, R. B. Smith, and S. D. Eckermann

An overview will be provided of the first field campaign that attempts to follow deeply propagating gravity waves (GWs) from their tropospheric sources to their mesospheric breakdown. The DEEP propagating gravity WAVE experiment over New Zealand (DEEPWAVE-NZ) is a comprehensive, airborne and ground-based measurement and modeling program focused on providing a new understanding of GW dynamics and impacts from the troposphere through the mesosphere and lower thermosphere (MLT). This program will employ the new NSF/NCAR GV (NGV) research aircraft from a base in New Zealand in a 6-week field measurement campaign in June-July 2014. The NGV will be equipped with new lidar and airglow instruments for the DEEPWAVE measurement program, providing temperatures and vertical winds spanning altitudes from immediately above the NGV flight altitude (~13 km) to ~100 km. The region near New Zealand is chosen since all the relevant GW sources occur strongly here, and upper-level winds in austral winter permit GWs to propagate to very high altitudes. Given large-amplitude GWs that propagate routinely into the MLT, the New Zealand region offers an ideal natural laboratory for studying these important GW dynamics and effects impacting weather and climate over a much deeper atmospheric layer than previous campaigns have attempted (0-100 km altitude). The logistics of making measurements in the vicinity of New Zealand are potentially easier than from the Andes and Drake Passage region.

A suite of GW-focused modeling and predictability tools will be used to guide NGV flight planning to GW events of greatest scientific significance. These models will also drive scientific interpretation of the GW measurements, together providing answers to the key science questions posed by DEEPWAVE about GW dynamics, morphology, predictability and impacts from 0-100 km. Preliminary results will be presented from high-resolution and adjoint models applied over areas featuring deep wave propagation. The high-resolution models highlight the role of lateral shear from the jet stream that refracts vertically propagating gravity waves generated by regions of high terrain, such as New Zealand and the southern Andes. The predictability links between the lower tropospheric fronts, cyclones, and jets, and GWs that vertically propagate upward through the stratosphere are quantified using a nonhydrostatic adjoint model. Results indicate that the forecast cross-mountain winds and gravity wave launching are very sensitive to the model initial state and in particular to synoptic-scale and mesoscale characteristics of mid-latitude cyclones and fronts.

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