Implementation of Sub-Grid Scale Temperature Perturbations Induced by Non-Orographic Gravity Waves in WACCM6

Abstract

Atmospheric gravity waves can play a significant role on atmospheric chemistry through temperature fluctuations. A recent modeling study introduced a method to implement subgrid-scale orographic gravity-wave-induced temperature perturbations in the Whole Atmosphere Community Climate Model (WACCM). The model with a wave-induced temperature parameterization was able to reproduce for example, the influence of mountain wave events on atmospheric chemistry, as highlighted in previous literature. Here we extend the subgrid-scale wave-induced temperature parameterization to also include non-orographic gravity waves arising from frontal activity and convection. We explore the impact of these waves on middle atmosphere chemistry, particularly focusing on reactions that are strongly sensitive to temperature. The non-orographic gravity waves increase the variability of chemical reaction rates, especially in the lower mesosphere. As an example, we show that this, in turn, leads to increases in the daytime ozone variability. To demonstrate another impact, we briefly investigate the role of non-orographic gravity waves in cirrus cloud formation in this model. Consistent with findings from the previous study focusing on orographic gravity waves, non-orographic waves also enhance homogeneous nucleation and increase cirrus clouds. The updated method used enables the global chemistry-climate model to account for both orographic and non-orographic gravity-wave-induced subgrid-scale dynamical perturbations in a consistent manner.