Observation Diagnostics Overview

The observation diagnostics subsystem processes IODA files and generates a comprehensive suite of observation‑space diagnostics, including statistics, histograms, QC summaries, and ATMS‑specific channel and scan‑position diagnostics. These tools quantify how well the background and analysis fields fit the observations and complement the increment and spectral diagnostics. For the mathematical formulation and example figures, see Diagnostics Overview.

Subsystem Components

The observation diagnostics subsystem consists of the following components:

  • ObsDiagnostic — core engine for computing O–B and O–A departures, bias, RMS, normalized RMS, and QC‑filtered statistics

  • IODA loaders — readers for satellite and conventional observation files

  • Scalar histograms — e.g., temperature, humidity, pressure

  • Vector histograms — e.g., wind components (u, v)

  • ATMS diagnostics — channel‑wise extended RMS statistics and scan‑position bias checks

  • QC summaries — counts and statistics for QC‑passed and QC‑failed observations

  • Plotting utilities — generation of extended RMS, histogram, and scan‑position figures

Workflow

A typical observation‑diagnostic workflow consists of:

  1. Load IODA file Read observation values, metadata, and QC flags.

  2. Load H(x) files Load background and analysis model equivalents for computing O–B and O–A departures.

  3. Compute statistics Compute bias, RMS, normalized RMS, bias‑corrected RMS, and QC‑filtered statistics for each variable and channel.

  4. Generate plots Produce histograms, extended RMS figures, scan‑position diagnostics, and QC summaries.

  5. Save outputs Write statistics tables and figures to the output directory.