Unstructured global to coastal wave modeling for the Energy Exascale Earth System Model using WAVEWATCH III version 6.07

Steven R Brus,Phillip J Wolfram,Luke P Van Roekel,Jessica D Meixner

doi:10.5194/gmd-14-2917-2021

Abstract

Abstract. Wind-wave processes have generally been excluded from coupled Earth system models due to the high computational expense of spectral wave models, which resolve a frequency and direction spectrum of waves across space and time. Existing uniform-resolution wave modeling approaches used in Earth system models cannot appropriately represent wave climates from global to coastal ocean scales, largely because of tradeoffs between coastal resolution and computational costs. To resolve this challenge, we introduce a global unstructured mesh capability for the WAVEWATCH III (WW3) model that is suitable for coupling within the US Department of Energy's Energy Exascale Earth System Model (E3SM). The new unstructured WW3 global wave modeling approach can provide the accuracy of higher global resolutions in coastal areas at the relative cost of lower uniform global resolutions. This new capability enables simulation of waves at physically relevant scales as needed for coastal applications.

Highlights

Wind-generated waves play an important interfacial role in the global coupled climate system
The purpose of this paper is to report on progress toward this goal, starting with an assessment of the accuracy and performance of the WAVEWATCH III (WW3) model (Tolman, 1991) using global to coastal unstructured meshes, which are compared to a single structured grid
Our results demonstrate the accuracy and efficiency advantages of global unstructured meshes compared to a single structured grid

Summary

Introduction

Wind-generated waves play an important interfacial role in the global coupled climate system. They mediate multiphase interactions between the ocean, atmosphere, and sea ice (Cavaleri et al, 2012) and influence the land surface in coastal zones (Mariotti and Fagherazzi, 2010). Wave processes drive air–sea momentum transfer (Donelan et al, 2012), enhance ocean mixing via Langmuir turbulence (Belcher et al, 2012), and modulate ocean surface albedo (Frouin et al, 2001). Ocean currents interact with waves via Doppler shifting, which has an effect on wave heights (Ardhuin et al, 2017). Waves drive unstable currents at the ice edge, leading to mesoscale eddy generation (Dai et al, 2019)

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Conclusion