Forecasting Contrail Formation
Inside the AFGWC Computer Model
What is the AFGWC Program?
The Air Force Global Weather Central (AFGWC) utilizes a specialized computer program to analyze atmospheric conditions. Its primary goal is to identify and forecast the tops and bottoms of layers in the atmosphere where contrails are expected to form.
The Core Assumption: A Humidity Profile
To make predictions, the program doesn't measure humidity everywhere. Instead, it relies on a built-in model that assumes specific relative humidity (RH) values for different atmospheric layers. The chart below visualizes this simplified profile.
Assumed Relative Humidity vs. Atmospheric Layer
This stepped chart shows the sharp, discrete changes in assumed humidity that the model uses to calculate contrail layers.
Key Operational Parameters
Beyond the core humidity model, the program operates with several key constraints and a defined scope.
2
Layers Retained
Due to operational considerations, only the two most likely contrail layers are retained for each grid point.
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Geographic Scope
Predictions are made for the entire Northern Hemisphere and the Tropics.
Assumed Layers & Humidity
Stratosphere
Vicinity of Tropopause
Upper Troposphere