Gravity Waves

The SPARC Gravity Wave Activity in recent years has placed a focus on the role of gravity waves in driving the general circulation of the stratosphere. While planetary-scale Rossby wave-driving clearly dominates the stratospheric circulation, small biases in the zonal-mean zonal winds can have very signifcant effects on Rossby wave propagation. Parameterized gravity wave (GW) drag in climate models is a primary tool used to reduce zonal-mean wind biases, and hence small-scale GWs can have larger impacts by helping to shape the propagation pathways of the more dominant Rossby waves.  In the tropical stratosphere, GWs also play a dominant role in driving the quasi-biennial oscillation. This gives small-scale GWs an important role in regional climate patterns by shaping teleconnection pathways.

GWs have additional roles in long-range weather forecasting through their influence on planetary wave propagation and sudden stratospheric warmings.  Improving the realism of these processes in global models requires realistic GW drag forces and their changes over the broad range of timescales for weather and climate applications.

Current high resolution global models can resolve GWs, at least partly. In relation to this, new issues regarding high resolution global models have emerged. Scale-aware parameterizations are needed, those that scale down parameterized GW forces as resolution improves, in order to avoid double counting the GW effect. However, resolvability of GWs and GW drag in models with different dynamical cores (e.g. spectral models versus grid models) is itself a complex and interesting issue and another area of active research.

Current activities

A new project called “WAVE-GAP – Watching Atmospheric Variability Evolve in the Global Absence of satellite Platforms” has been launched in autumn 2025. This project was selected for funding as an International Team by the International Space Science Institute, and aims at addressing the forthcoming gap in high-resolution stratospheric satellite coverage.