3.4. solver

Parameters for the core LETKF solver, diagnostic output, and covariance inflation.

Parameters

save_diag:

type: boolean, default: true

Whether a diagnostic file is saved at the end of the UMD-LETKF run.

This file contains diagnostic information such as the number of observations used per grid cell, maximum horizontal localization radius, etc. See LETKF Solver Diagnostics

diag_file:

type: string, default: “diag.solver.nc”

The file name of the diagnostic output.

Only used if save_diag is set to true.

Example

solver:
  save_diag: true
  diag_file: "diag.solver.nc"

3.4.1. inflation

Covariance inflation methods for increasing the ensemble spread. This section is optional. If not provided the default of “no inflation” will be used.

Note

The RTPS and RTPP methods cannot be enabled simultaneously.

Parameters

mul:

type: float, default: 1.0

The amount of Multiplicative inflation to apply.

Valid parameters are greater than or equal to 1.0. Value of 1.0 indicates multiplicative inflation is off.

rtpp:

type: float, default: 0.0

The percentage of Relaxation to Prior Perturbations (RTPP) to apply.

Valid parameters are between 0.0 and 1.0. Value of 0.0 indicates RTPS is off, 1.0 indicates the analysis ensemble perturbations are relaxed 100% back toward the background perturbation. Unless you know what you are doing, you are better off using Relaxation to Prior Spread (RTPS). Cannot be used if RTPS is enabled

rtps:

type: float, default: 0.0

The percentage of Relaxation to Prior Spread (RTPS) to apply.

Valid parameters are between 0.0 and 1.0. A value of 0.0 indicates RTPS is off, 1.0 indicates analysis spread is relaxed 100% back toward the background spread. Values between 0.5 and 0.8 are often good choices. You could in theory use values greater than 1.0 to result in analysis spread that is larger than background spread, but I have no idea why you would want to do this. Cannot be used if RTPP is enabled.

Example

solver:
  inflation:
    rtps: 0.6
    rtpp: 0.0
    mul:  1.0