Model Hierarchies for Understanding Atmospheric Circulation

Abstract

In this review, we highlight the complementary relationship between simple and comprehensive models in addressing key scientific questions to describe Earth's atmospheric circulation. The systematic representation of models in steps, or hierarchies, connects our understanding from idealized systems to comprehensive models and ultimately the observed atmosphere. We define three interconnected principles that can be used to characterize the model hierarchies of the atmosphere. We explore the rich diversity within the governing equations in the dynamical hierarchy, the ability to isolate and understand atmospheric processes in the process hierarchy, and the importance of the physical domain and resolution in the hierarchy of scale. We center our discussion on the large‐scale circulation of the atmosphere and its interaction with clouds and convection, focusing on areas where simple models have had a significant impact. Our confidence in climate model projections of the future is based on our efforts to ground the climate predictions in fundamental physical understanding. This understanding is, in part, possible due to the hierarchies of idealized models that afford the simplicity required for understanding complex systems.

The Future of Midlatitude Cyclones

“…& Current results from idealized simulations are not easily comparable with the output from complex climate simulations. A recent review paper [171] has analyzed in depth what we can learn from using models of different complexity. In the specific context of ETCs, the consideration of the "hierarchy of processes" seems to be the most relevant.…”

Aquaplanet Simulations of Tropical Cyclones

“…The BEarth-Like Aquaplanets^section reviews TC-permitting simulation results in this configuration. This series of model configurations was outlined in the review of Jeevanjee et al [36•] as a possible Belegant tropical model hierarchy.^Hierarchical modelling of the atmosphere, with an emphasis on larger scales, has also been recently reviewed by [37]. Model hierarchies often prove to be useful when they are used across a range of scientific questions [38], so while we review TC research here, there are a broader range of fundamental questions of tropical climate that the same configurations can be used to address (BOutlook^).…”

Hierarchical Modeling of Solar System Planets with Isca

“…In this paper we describe the use of Isca to construct models of varying complexity for three Solar System planets, Earth, Mars, and Jupiter. Hierarchical modeling of Earth's atmosphere and climate is a well established field, with notable contributions and endorsements by Schneider and Dickinson [73] and Hoskins [74]; reinforced by Held [75]; discussed by Vallis [76]; and reviewed by Maher et al [10]. Hierarchical modeling is, in our view, even more important if we wish to understand and simulate (not always the same thing) planets other than our own, for the reasons discussed in the Introduction.…”

“…There will, however, be no single level of complexity that is appropriate even for a given planet, especially if we are to both understand and compare to observations. Thus, we propose that, as has been implemented to some degree already for Earth (for a discussion, see [10]), a hierarchical approach will be useful. In such an approach, we may use a rather simple class of models that can be applied with minimal changes across a range of planetary atmosphere to understand the basic behavior as various parameters (e.g., rotation rate) are changed, building up in complexity if we wish to study a particular planet in more detail.…”