Atmospheric Science – Precise definition of temperature inversion Which statement best defines a temperature inversion, a key concept in meteorology and air-quality studies?

Introduction / Context:
A temperature inversion is fundamental in weather forecasting and environmental engineering because it traps pollutants, suppresses convection, and influences fog and cloud formation. Knowing the exact definition helps interpret radiosonde soundings and stability indices.

Given Data / Assumptions:

• Normal tropospheric lapse rate implies temperature decreases with altitude.
• We are classifying vertical temperature structures over a short vertical interval.
• Humidity variations alone do not define an inversion.

Concept / Approach:
A temperature inversion exists when the vertical temperature gradient becomes positive over some layer: dT/dz > 0. Causes include nocturnal radiational cooling of the ground, frontal overrunning (warm air above cooler air), and subsidence warming aloft. Inversions enhance static stability and reduce vertical mixing, often intensifying pollution episodes.

Step-by-Step Solution:
Recall the norm: temperature decreases with altitude (negative lapse rate).Identify inversion condition: temperature increases with height over a finite layer.Exclude definitions centered on humidity or isothermal layers; these do not meet inversion criteria.Select the option clearly stating “temperature increases with height.”

Verification / Alternative check:
Skew-T/Log-P soundings show inversions as right-tilting temperature traces with height. These correlate with reduced mixing depths and trapped aerosols.

Why Other Options Are Wrong:

• Normal decrease with height: describes a non-inverted, typical tropospheric profile.
• Humidity increase alone: moisture is not the defining parameter for inversion.
• Isothermal layer: indicates zero lapse rate, not a reversal.

Common Pitfalls:
Confusing isothermal layers with inversions; both suppress mixing, but only inversions have temperature increasing with height. Also, do not equate any stable layer with an inversion without checking the sign of the temperature gradient.

Final Answer:
A layer in which air temperature increases with height, reversing the normal decrease with altitude