Using Log Diagnostics

The log diagnostics subsystem parses a full JEDI variational DA log and extracts structured diagnostics including configuration metadata, observation counts, Jo evolution, cost‑function convergence, departures, and chi‑squared consistency information. These diagnostics complement the increment, spectra, and observation‑space tools by providing insight into the internal behavior of the variational minimization. For a high‑level description, see Diagnostics Overview.

Running the CLI Tool

The log diagnostics tool does not use a YAML configuration. It is invoked directly from the command line:

ufsda-jedi-log jedi.log

To write the full human‑readable report to a file:

ufsda-jedi-log jedi.log --output report.txt

The tool scans the entire JEDI log file and extracts structured diagnostic fields, producing a formatted text report and optional plots.

Chi‑Squared Consistency Check

The log parser extracts Jo, Jb, and total cost values at each iteration and computes the chi‑squared consistency metric:

\[\chi^2 = \frac{\mathrm{Jo}}{p}\]

where \(p\) is the number of assimilated observations. Values near unity indicate consistency between observation errors, background errors, and the resulting analysis increments.

Outputs

When --output is used, the following files are produced:

  • report.txt — formatted human‑readable diagnostic report

  • jo_evolution.png — Jo evolution across outer iterations

  • cost_convergence.png — total cost, Jb, and Jo convergence

These outputs provide a structured view of the variational minimization and help diagnose issues related to observation errors, background errors, and convergence behavior.

Example Report (Excerpt)

Below is a shortened excerpt of the generated report.txt:

================================================================================
  JEDI Variational DA - Diagnostic Report
================================================================================

  1. CONFIGURATION SUMMARY
  ------------------------
  Cost Type          : 3D-Var
  Analysis Time      : 2024-02-24T00:00:00Z
  Window Length      : PT6H
  Outer Resolution   : C96
  Inner Resolution   : C48
  Ensemble Members   : 2

  2. OBSERVATION COUNTS
  ----------------------
  Obs Type                Total Obs   Assimilated   Assim%
  conventional_ps          116,459       107,491     92.3%
  gnssro_cosmic2           363,132       227,802     62.7%
  ATMS N20                 245,124       167,540     68.3%

  3. Jo/n EVOLUTION
  ------------------
  ATMS N20   0.186 -> 0.154 -> 0.126

  4. COST FUNCTION CONVERGENCE
  -----------------------------
  Outer 0: J = 149,138 → 136,351
  Outer 1: J = 136,732 → 121,229

  5. CHI-SQUARED CONSISTENCY
  ---------------------------
  ATMS N20   Jo/P = 0.126   (overestimated)