Forcing mechanisms of the quarterdiurnal tide

Abstract

Abstract. We used a nonlinear mechanistic global circulation model to analyze the migrating quarterdiurnal tide (QDT) in the middle atmosphere with focus on its possible forcing mechanisms. These are absorption of solar radiation by ozone and water vapor, nonlinear tidal interactions, and gravity wave-tide interactions. We show a climatology of the QDT amplitudes, and we examined the contribution of the different forcing mechanisms on the QDT amplitude. To this end, we first extracted the QDT in the model tendency terms. Then, we separately removed the QDT contribution in different tendency terms. We find that the solar forcing mechanism is the most important one for the QDT, but also the nonlinear and gravity wave forcing mechanism play a role in certain seasons, latitudes and altitudes. Furthermore, destructive interference between the individual forcing mechanisms are observed. Therefore, tidal amplitudes partly become even larger in simulations with removed nonlinear or gravity wave forcing mechanism.

High‐Order Solar Migrating Tides Quench at SSW Onsets

“…Most of the tidal literature is devoted to data analyses, modeling, and interpretation of S1, S2, and S3. Recently, S4 has received some attention in terms of ground-based observations (e.g., Guharay et al, 2018;Jacobi et al, 2017;Smith et al, 2004), space-based observations (e.g., Azeem et al, 2016;Liu et al, 2015;Xu et al, 2012) and modeling (e.g., Geissler et al, 2019;Smith et al, 2004). The ground-based observations have the advantage of high temporal resolution, but cannot distinguish between migrating and nonmigrating tidal components from single-station measurements.…”