A Particle-in-Cell wave model for efficient sea-state and swell
estimates in Earth System Models - PiCLES
Abstract
Ocean surface waves have been demonstrated to be an important component
of coupled Earth System Models (ESMs), influencing atmosphere-ocean
momentum transfer, ice floe breakage, CFC, carbon and energy uptake, and
mixed-layer depth.
Modest errors in sea state properties do not strongly affect the impacts
of these parameterizations. The minimal data and accuracy needed
contrast sharply with the computational costs of spectral wave models in
next-generation ESMs. We establish an alternative, cost-efficient wave
modeling framework for air-sea and ice-ocean interactions that enables
the routine use of sea state-dependent air-sea coupling in ESMs.
In contrast to spectral models, the Particle-in-Cell for Efficient Swell
(PiCLES) wave model is constructed for coupled atmosphere-ocean-sea ice
modeling. Combining Lagrangian wave growth solutions with the
Particle-In-Cell method leads to a model that periodically projects onto
any convenient grid and scales in an embarrassingly parallel manner. The
set of equations solves for the growth and propagation of a parametric
wave spectrum’s peak wavenumber and total wave energy, which reduces the
state vector size by a factor of 50-200 compared to spectral models. We
estimate PiCLES’s computational costs about 1-4 orders of magnitude
faster than established wave models with sufficient accuracy for ESMs
– rivaling that of spectral models in the open ocean. We evaluate
PiCLES against WAVEWATCH III in efficiency and accuracy and discuss the
advantages of future performance and planned extensions of its
capability in ESMs.