CATKE: a turbulent-kinetic-energy-based parameterization for ocean microturbulence with dynamic convective adjustment

We describe CATKE, a parameterization for ocean microturbulence with scales between 1 and 100 meters. CATKE is a one-equation model that predicts diffusive turbulent vertical fluxes a prognostic turbulent kinetic energy (TKE) and a diagnostic mixing length that features a dynamic model for convective adjustment (CA). With its convective mixing length, CATKE predicts not just the depth range where microturbulence acts but also the timescale over which mixing occurs, an important aspect of turbulent convection not captured by convective adjustment schemes. As a result, CATKE can describe the competition between convection and other processes such as baroclinic restractification or biogeochemical production-destruction. We estimate CATKE's free parameters with a posteriori calibration to eighteen large eddy simulations of the ocean surface boundary layer, and validate CATKE against twelve additional large eddy simulations with stronger and weaker forcing than used during calibration. We find that a CATKE-parameterized single column model accurately predicts the depth structure of buoyancy and momentum at vertical resolutions between 2 and 16 meters and with time steps of 10-20 minutes. We propose directions for future model development, and future efforts to recalibrate CATKE's parameters against more comprehensive and realistic datasets.Comment: submitted to J. Adv. Model. Earth Sy., 24 pages, 8 figure

Supervised Calibration and Uncertainty Quantification of Subgrid Closure Parameters using Ensemble Kalman Inversion

Data-driven approaches are increasingly being used to identify and remove structural biases in dynamical models for real-world systems. However, because model updates alter the dependency of a model on its free parameters, evidence about structural biases is often muddied by the variable influences of inadequately-tuned parameters on the model solution. We elaborate a framework for model development that combines calibration, sensitivity analysis, and uncertainty quantification of free parameters to shed light on where structural biases are likely to exist in a model, and where the model may be unnecessarily complex. The approach is useful for general applications because it is easy to implement, derivative-free, robust against model instabilities, and computationally inexpensive, requiring a modest number of model evaluations. A diffusive closure for turbulence penetrated by air-sea fluxes of the ocean surface, presently called the “Convective Turbulent Kinetic Parameterization," is developed as a testbed for and proof-of-concept for the approach. Modifications to the traditional Ensemble Kalman Inversion [1] algorithm are devised to improve convergence during the calibration phase of this process. Further, the Calibrate Emulate Sample [2] framework for uncertainty quantification is validated with modifications.M.Eng

CliMA/Oceananigans.jl: v0.88.0

Oceananigans v0.88.0 Diff since v0.87.4 Merged pull requests: (0.88.0) MPI communication and computation overlap in the HydrostaticFreeSurfaceModel and NonhydrostaticModel (#3125) (@simone-silvestri) Linear time interpolation in FieldTimeSeries (#3236) (@simone-silvestri) Fill metrics for halo regions for OrthogonalSphericalShellGrid (#3239) (@navidcy) Fix docstring for RectilinearGrid grid metrics (#3255) (@navidcy) Cubed sphere tracer advection script (#3266) (@glwagner) Remove some type instabilities (#3271) (@navidcy) Closed issues: Overlapping computation and MPI halo communication (#615) Abstraction for configuring kernels (#3067) Offsetting kernel indices (#3068) Velocity profile of channel flow case has difference with log-law (#3195) OrthogonalSphericalShellGrid metrics and coordinates are missing values in halo points (#3198) Advection of tracer with prescribed or constant velocities over a ConformalCubedSphereGrid (#3204) Should grid be a positional argument to model constructors? (#3250) RectilinearGrid metrics are described wrong in the docstring (#3252) GPU illegal memory access (#3267) Does Oceananigans support coastal modelling? (#3269

CliMA/Oceananigans.jl: v0.87.4

Oceananigans v0.87.4 Diff since v0.87.3 Merged pull requests: Deal with x ⇆ y, λ ⇆ φ, etc when filling halos for metrics/coords in ConformalCubedSphereGrid (#3256) (@navidcy) Rename return_metrics -> coordinates (#3257) (@navidcy) Update dependencies and use Julia 1.9.3 for CI (#3258) (@navidcy) (0.87.4) Add missing with_advective_forcing method (#3259) (@glwagner) Closed issues: Evolving perturbations vs total fields in Nonhydrostatic model (#3251) Rename return_metrics since it returns coordinates, not metrics (#3253) Metrics across ConformalCubedSphereGrid panels (#3254