What defines 'diurnal' variations in meteorology?

Diurnal variations in meteorology refer specifically to the changes that occur over a 24-hour period, primarily due to the cycle of day and night. These variations are typically observed in meteorological elements such as temperature, humidity, and wind patterns, which fluctuate as the sun rises and sets. For example, temperatures generally peak in the late afternoon when solar heating is at its maximum and decrease during the night as heat radiates away from the Earth's surface.

Understanding diurnal variations is essential for weather forecasting and for predicting local climatic conditions, as it helps meteorologists gauge how atmospheric parameters will change in response to daily solar radiation. The other choices describe variations related to time scales that do not specifically align with the diurnal cycle; they either cover longer periods or different contexts.