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Abstract Dong et al. (2020,https://doi.org/10.1029/2019JD030691) employed a new compressible model to examine gravity wave (GW) self‐acceleration dynamics, instabilities, secondary gravity wave (SGW) generation, and mean forcing for GW packets localized in two dimensions (2D). This paper extends the exploration of self‐acceleration dynamics to a GW packet localized in three dimensions (3D) propagating into tidal winds in the mesosphere and thermosphere. As in the 2D packet responses, 3D GW self‐acceleration dynamics are found to be significant and include 3D GW phase distortions, stalled GW vertical propagation, local instabilities, and SGW and acoustic wave generation. Additional 3D responses described here include refraction by tidal winds, localized 3D instabilities, asymmetric SGW propagation, reduced SGW and acoustic wave responses at higher altitudes relative to 2D responses, and forcing of transient, large‐scale, 3D mean responses that may have implications for chemical and microphysical processes operating on longer time scales.
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Modeling Responses of Polar Mesospheric Clouds to Gravity Wave and Instability Dynamics and Induced Large‐Scale Motions
Abstract A gravity wave (GW) model that includes influences of temperature variations and large‐scale advection on polar mesospheric cloud (PMC) brightness having variable dependence on particle radius is developed. This Complex Geometry Compressible Atmosphere Model for PMCs (CGCAM‐PMC) is described and applied here for three‐dimensional (3‐D) GW packets undergoing self‐acceleration (SA) dynamics, breaking, momentum deposition, and secondary GW (SGW) generation below and at PMC altitudes. Results reveal that GW packets exhibiting strong SA and instability dynamics can induce significant PMC advection and large‐scale transport, and cause partial or total PMC sublimation. Responses modeled include PMC signatures of GW propagation and SA dynamics, “voids” having diameters of ∼500–1,200 km, and “fronts” with horizontal extents of ∼400–800 km. A number of these features closely resemble PMC imaging by the Cloud Imaging and Particle Size (CIPS) instrument aboard the Aeronomy of Ice in the Mesosphere (AIM) satellite. Specifically, initial CGCAM‐PMC results closely approximate various CIPS images of large voids surrounded by smaller void(s) for which dynamical explanations have not been offered to date. In these cases, the GW and instabilities dynamics of the initial GW packet are responsible for formation of the large void. The smaller void(s) at the trailing edge of a large void is (are) linked to the lower‐ or higher‐altitude SGW generation and primary mean‐flow forcing. We expect an important benefit of such modeling to be the ability to infer local forcing of the mesosphere and lower thermosphere (MLT) over significant depths when CGCAM‐PMC modeling is able to reasonably replicate PMC responses.
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- PAR ID:
- 10374381
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 126
- Issue:
- 13
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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