Scale-Awareness in an Eddy Energy Constrained Mesoscale Eddy Parameterization

• Published in: Journal of Advances in Modeling Earth Systems
• Main Authors: Mak, Julian, Maddison, James R., Marshall, David P., Ruan, Xi, Wang, Yan, Yeow, Liiyung
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Southern Ocean
• Online Access: https://repository.hkust.edu.hk/ir/Record/1783.1-133000; https://doi.org/10.1029/2023MS003886; http://lbdiscover.ust.hk/uresolver?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rfr_id=info:sid/HKUST:SPI&rft.genre=article&rft.issn=&rft.volume=15&rft.issue=12&rft.date=2023&rft.spage=&rft.aulast=Mak&rft.aufirst=Julian&rft.atitle=Scale-Awareness+in+an+Eddy+Energy+Constrained+Mesoscale+Eddy+Parameterization&rft.title=Journal+of+Advances+in+Modeling+Earth+Systems

There is an increasing interest in mesoscale eddy parameterizations that are scale-aware, normally interpreted to mean that a parameterization does not require parameter recalibration as the model resolution changes. Here we examine whether Gent–McWilliams (GM) based version of GEOMETRIC, a mesoscale eddy parameterization that is constrained by a parameterized eddy energy budget, is scale-aware in its energetics. It is generally known that GM-based schemes severely damp out explicit eddies, so the parameterized component would be expected to dominate across resolutions, and we might expect a negative answer to the question of energetic scale-awareness. A consideration of why GM-based schemes damp out explicit eddies leads a suggestion for what we term a splitting procedure: a definition of a “large-scale” field is sought, and the eddy-induced velocity from the GM-scheme is computed from and acts only on the large-scale field, allowing explicit and parameterized components to co-exist. Within the context of an idealized re-entrant channel model of the Southern Ocean, evidence is provided that the GM-based version of GEOMETRIC is scale-aware in the energetics as long as we employ a splitting procedure. The splitting procedure also leads to an improved representation of mean states without detrimental effects on the explicit eddy motions.