Which of these is a sign that a temperature inversion may be developing?

• A. Dust or smoke rises dramatically
• B. Dust or smoke rises only slightly and tends to hang in the air
• C. No movement of dust or smoke is observed
• D. The air remains perfectly still and clear

Answer: (B)

A temperature inversion creates a stable layer near the surface that resists vertical mixing. As this stability begins, dust or smoke from ground level tends to rise only a little and then stay suspended in the air, hanging around instead of dispersing upward. This slow or minimal vertical movement is a telltale sign that an inversion may be developing because the cooler, denser air at the ground is trapped beneath warmer air, limiting upward motion. In contrast, dust or smoke rising dramatically points to convection and a more unstable atmosphere, while no movement or perfectly still air aren’t specific indicators of an inversion developing. So, the sign described—dust or smoke rising only slightly and tending to hang in the air—is the best indicator.