CPFM CPFM Weather & Atmospheric Conditions 1 — Questions and Answers
Question 1: What wind speed range is generally considered acceptable for conducting prescribed burns?
- 0–2 mph
- 5–15 mph (Correct answer)
- 20–25 mph
- 30+ mph
Correct answer: 5–15 mph
Wind speeds of 5–15 mph are generally acceptable for prescribed burns as they provide adequate smoke dispersal without causing excessive spotting.
Question 2: What atmospheric condition traps smoke near the ground by placing warm air above cooler air?
- Convective column
- Temperature inversion (Correct answer)
- Adiabatic lapse rate
- Thermal updraft
Correct answer: Temperature inversion
A temperature inversion reverses the normal atmospheric temperature gradient, preventing vertical mixing and trapping smoke near the surface.
Question 3: What relative humidity level is typically considered the minimum threshold for safe prescribed burning?
- 10%
- 15%
- 25–30% (Correct answer)
- 50%
Correct answer: 25–30%
Relative humidity below 25–30% significantly increases fire behavior unpredictability and the risk of losing control of a prescribed burn.
Question 4: What does the Haines Index measure in relation to prescribed fire?
- Fuel moisture content
- Potential for large fire growth (Correct answer)
- Wind direction variability
- Smoke dispersal capacity
Correct answer: Potential for large fire growth
The Haines Index combines lower atmospheric stability and moisture levels to indicate the potential for large, erratic fire development.
Question 5: Which weather phenomenon poses the greatest risk of causing spotting (fires starting outside the burn unit) during a prescribed burn?
- Fog
- Stable air mass
- Gusty, erratic winds (Correct answer)
- High relative humidity
Correct answer: Gusty, erratic winds
Gusty, erratic winds can carry burning embers unpredictably far beyond control lines, igniting spot fires outside the intended burn area.
Question 6: During clear, sunny conditions, at what time of day is atmospheric instability typically greatest?
- Early morning (6–8 AM)
- Late morning (9–11 AM)
- Early afternoon (1–3 PM) (Correct answer)
- Evening (6–8 PM)
Correct answer: Early afternoon (1–3 PM)
Solar heating peaks in the early afternoon, creating maximum surface temperatures and strongest convective mixing, which produces the greatest atmospheric instability.
CPFM CPFM Weather & Atmospheric Conditions 1
What wind speed range is generally considered acceptable for conducting prescribed burns?