Duff moisture code

Essentially, it's a measure of how dry the middle layer of forest floor fuels are, which is critical for predicting the likelihood of sustained, deeper burning fires.

The duff moisture code is heavily influenced by several key weather parameters:

• Temperature: Higher temperatures reduce the moisture content of the duff layer, leading to a higher duff moisture code. Warm air increases evaporation and draws moisture from the duff.
• Relative humidity: Lower relative humidity pulls moisture from the duff layer, increasing the duff moisture code. Dry air accelerates the drying process.
• Precipitation: Significant rainfall is needed to penetrate and moisten the duff layer. Light showers have minimal impact. The duration and intensity of rainfall are key.
• Time since last significant rain: Unlike the fine fuel moisture code, the duff moisture code responds more slowly to rainfall. It reflects the cumulative effect of drying over several days.
• Shade and forest cover: Dense forest cover can moderate the drying effect of sunlight and wind, but prolonged dry periods will still affect the duff moisture code.

The duff moisture code is a crucial component of fire weather index systems. It provides a measure of the potential for deeper, smoldering fires that can persist for extended periods and reignite after surface fires have been extinguished. A high duff moisture code indicates a greater risk of these persistent, deeper fires, which are harder to detect and control, while a low duff moisture code suggests a lower risk.