Contrasting the gravity wave forcing between nudged and free-running models and reanalysis

Abstract. Internal gravity waves contribute to energy and momentum budgets across atmospheric layers. Hence, incorporating their dynamics through parameterization schemes is essential for Earth system models. However, any constraints on the parameterized gravity wave effects, especially on global spatial and climatological temporal scales, are practically non-existent. Here, we compare the recently published resolved gravity wave drag estimates and effects from the current generation high-resolution reanalysis with the climatology and dynamics in three different Earth system model simulations. The results show that except for differences in the mean value of gravity wave drag between the datasets, the parameterized drag in the models and the resolved drag in the reanalysis show very similar characteristics in terms of distribution and extremity. Despite this, we report pronounced differences in dynamical impacts of gravity waves between the reanalysis and the models in the lower stratosphere, where the parameterized gravity wave drag has a strong correlation with the Rossby wave forcing in the models. However, in ERA5 reanalysis we could not find any link between lower stratospheric resolved gravity and Rossby wave dynamics. This result indicates that the dynamical effects of gravity waves that we know from Earth system models can be different if gravity waves are resolved, which can have far-reaching implications for the gravity wave parameterization development and climate modeling and prompts further validation using alternative datasets in future work.