Ocean-Atmosphere Coupling in Earth System Models: Formulation and Algorithms
DescriptionIn this talk, we address the ocean-atmosphere coupling problem from the point of view of domain decomposition methods. We show that present coupling methods used in realistic ocean-atmosphere coupled models can be written in the formalism of Schwarz iterative algorithms, and correspond to methods that are not pushed to convergence, which may lead to imperfect coupling. We discuss the objective of achieving a mathematically and physically consistent ocean-atmosphere coupling and we show that using improved coupling algorithms (like Schwarz methods) can impact the solution of a realistic climate model (IPSL-CM) quite significantly (Marti et al., 2021). In particular it is shown that traditional "parallel" coupling algorithm used in IPSL-CM can have large error after sunrise and before sunset, which means that there is room for improvement in the representation of the diurnal cycle. This error is significantly reduced when using a sequential algorithm but at the expanse of a loss of parallelism. Those findings are confirmed and substantiated in a simplified context using the single-column version of EC-Earth which allows to focus on the role of parametrizations in the coupling. Finally, we conclude by summarizing some challenges in the numerical formulation of climate models.
TimeMonday, June 2614:00 - 14:30 CEST
Climate, Weather and Earth Sciences