What does humidity measure in the atmosphere?

Humidity measures the amount of moisture present in the atmosphere. It quantifies the concentration of water vapor in the air, which is essential for understanding various weather phenomena. The measurement of humidity can be expressed in several ways, including absolute humidity, relative humidity, and specific humidity, each providing insight into the moisture content of the air relative to the temperature and pressure conditions.

While cloud cover, air pressure variations, and temperature fluctuations are all important atmospheric factors that can influence weather patterns, they do not directly measure moisture content in the atmosphere. Therefore, the correct choice specifically identifies the role of humidity as directly related to the presence of moisture, which is crucial for processes like precipitation, evaporation, and overall climate conditions. Understanding humidity is vital for forecasting weather and assessing comfort levels in different environments.