What measurement can be used to determine the stability of the atmosphere?

• A. Actual lapse rate
• B. Relative humidity
• C. Dew point
• D. Wind speed

Answer: (A)

Stability is determined by how temperature changes with height. The key measurement is the environmental lapse rate—the actual rate at which air temperature decreases as you go up. By comparing this rate to the adiabatic lapse rates (dry and moist), you can predict how a lifted air parcel will behave. If the environmental lapse rate is steeper than the dry adiabatic rate, a parcel will become warmer than its surroundings as it rises and keep rising, which means the atmosphere is unstable. If it’s gentler than the moist adiabatic rate, the parcel tends to cool relative to its surroundings and will tend to stop rising, indicating stability. Neutral conditions occur when the environmental lapse rate matches the dry adiabatic rate. In practice, weather soundings provide the environmental lapse rate, letting you assess stability. Relative humidity and dew point indicate moisture content, and wind speed describes motion, but neither alone directly measures how temperature changes with height to indicate stability.