Speaker
Description
Density is an essential parameter in ocean models and so is vital for understanding ocean dynamics. However, primitive equations cannot describe the flow of density. Instead, density is modeled as a nonlinear function of temperature, salinity, and pressure. The quantities stored in ocean models represent average quantities over a grid cell. Averaging nonlinear functions leads to errors. Thus, the density calculated by the model is not the same as the true average density. Jean-Michel Brankart proposed a stochastic correction to this error, which he used in the hydrostatic equation to compute the pressure gradient force [1]. His correction samples the difficult to evaluate equation of state several times, and thus is computationally expensive.
This work proposes (1) a novel way to correct the density errors incurred by averaging the nonlinear equation of state and (2) a new application of the correction. We found an analytic expression for a correction to the error. Our method requires only one evaluation of a nonlinear function and thus provides great computational savings over previous methods. We propose to use our correction in the computation of the pressure gradient force and in the computation of isopycnal slopes in the Gent-McWilliams parameterization of eddy-induced transport. Free parameters in our correction are assessed using model output from a high resolution (0.1 degree) eddy resolving Community Earth Systems Model 2 (CESM2) ocean model run [2]. These data constitute a 33-year time series of over 70 three-dimensional fields, saved every five days for a total of 2,400 files.
| Do you need an official invitation letter? | No |
|---|
