2020 Workshop:GW multistep vertical coupling

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Gravity wave multi-step vertical coupling from the troposphere to the thermosphere/ionosphere

Location, Date/Time and Duration

2 hours

Conveners

Sharon Vadas
Erich Becker

Workshop Categories

Altitudes: IT - Latitudes: global - Other:

Format of the Workshop

Short 5 Slide Presentations

Estimated attendance

30

Requested Specific Days

Any day except monday

Special technology requests

Justification

One of the challenges the aeronomy community has encountered recently is explaining GOCE and CHAMP satellite measurements from z=250-250 km. These recent observations have shown that there is a very strong gravity wave (GW) hotspot over the Southern Andes during the southern hemisphere winter, even though the mountain waves dissipate below the turbopause (at z~107 km) because they have near zero horizontal phase speeds. This mystery has led researchers to examine multi-step vertical coupling via wave mean flow interactions and other processes as a major mechanism which transforms primary GWs into secondary and higher-order GWs that propagate to the highest altitudes of the thermosphere. The generation of secondary and higher order GWs often shows alternating signs for the directions of the momentum flux and deposition, indicating that GW momentum flux is not transferred directly from the troposphere to the thermosphere. Because the GWs in the thermosphere generally have very large horizontal phase speeds, many cannot propagate in the lower and middle atmosphere where the sound speed is smaller, thus precluding the usual approach of applying a parameterization of primary GWs launched in the troposphere to account for GWs in the mid to upper thermospere. We believe that in order to better-understand the GW activity in the thermosphere/ionosphere (TI), models need to take into account multi step vertical coupling processes.

Description

In this workshop, we explore the multi-step vertical coupling connecting gravity waves (GWs) from the lower to upper atmosphere. In this process, GWs are generated throughout the atmosphere due to spatially and temporally localized wave mean flow interaction and other processes. Studies can be at low, middle or high latitudes, and can be based on models, observationss, or a combination of both. Examples of the GWs from primary sources we include here are the generation of GWs from 1) orographic forcing, moist convection, fronts, and jets in the troposphere, and 2) the polar vortex in the middle atmosphere. We emphasize the effects of these sources on the thermosphere/ionosphere (TI) via the generation of secondary and higher-order GWs (multi-step vertical coupling).

Workshop Summary

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