NOAA Unified Forecast System (UFS) Replay Overlap

Brightness Temperature (TB)

Brightness temperature (TB) is the temperature a blackbody would need to have to emit the same amount of microwave or infrared radiation as measured by a satellite or radiometer. It’s not a direct temperature reading but rather a way to interpret the intensity of radiation from Earth's surface or atmosphere in temperature units (Kelvin), based on the sensor’s specific frequency band.

How Brightness Temperature Is Used to Verify Data Assimilation Accuracy

1. Comparison with Model Outputs

• Numerical weather models simulate the atmosphere and can generate simulated brightness temperatures using radiative transfer models.
• These are compared to observed brightness temperatures from instruments like AMSU, AIRS, or AHI.
• The difference between them is called the Observation Minus Background (O–B) or Observation Minus Analysis (O–A).

2. Bias and Error Detection

• Systematic differences (biases) in O–B or O–A statistics can reveal model errors or deficiencies in data assimilation.
• Random differences help estimate the uncertainty or quality of the assimilation.

3. Assimilation Tuning

• By analyzing TB discrepancies over time and regions, assimilation systems can be adjusted for better radiance bias correction, error modeling, and quality control.