Thermodynamics and Meteorology – Terminology In physical geography and atmospheric science, the term for the rate of change of temperature per unit distance (for example, with height or across a horizontal distance) is called:

Introduction / Context:
Understanding how temperature varies in space is fundamental to thermodynamics, meteorology, oceanography, and even engineering heat transfer. The technical term that captures the “rate of change of temperature with distance” is widely used to explain phenomena such as lapse rates in the atmosphere, fronts, and heat flow in solids.

Given Data / Assumptions:

• The question asks for the rate of change of temperature with respect to distance.
• We are dealing with a spatial change (not simply a difference between two points).
• The answer should be a standard scientific term used across disciplines.

Concept / Approach:
In mathematics and physics, a “gradient” expresses how a quantity changes per unit distance. Therefore, the rate at which temperature changes in space is termed the temperature gradient. This can be vertical (common in meteorology) or horizontal (important for analyzing fronts). The concept generalizes to 3D vector form, indicating both magnitude and direction of greatest increase of temperature.

Step-by-Step Solution:

Verification / Alternative check:
In heat conduction, Fourier’s law uses the temperature gradient to compute heat flux: q = -k * grad(T). In meteorology, vertical temperature gradient underpins stability analysis and lapse rates, confirming the terminology’s correctness.

Why Other Options Are Wrong:

• Temperature difference: A simple subtraction between two points; not a rate per unit distance.
• Isotherm: A line joining points of equal temperature on a map, not a rate.
• None of the above: Incorrect because “temperature gradient” is the standard term.

Common Pitfalls:
Confusing “difference” (a scalar change) with “gradient” (change per unit distance, often a vector). Also, isotherms depict patterns but do not express the rate of change directly.

Final Answer:
temperature gradient