Which index measures long-term dryness or drought in the Fire Weather Index system?

• A. Fine Fuel Moisture Code
• B. Drought Code
• C. Duff Moisture Code
• D. Initial Spread Index

Answer: (B)

Long-term dryness in the Fire Weather Index system is captured by the Drought Code, which measures the moisture of the deep litter and duff layers and reflects drying over weeks. It increases during extended dry spells and only slowly lessens after rainfall, making it a reliable indicator of drought conditions and the potential for persistent, intense fires. The other components respond on shorter time scales or serve different purposes: the Fine Fuel Moisture Code tracks surface fuels that dry and wet quickly; the Duff Moisture Code measures mid-layer duff with a shorter lag than the Drought Code; and the Initial Spread Index relates to how fast a fire would spread given wind and slope, based on surface fuels.