The Water Cycle • Water in liquid, solid, and gaseous states is constantly being recycled though the water cycle.
Humidity • As water evaporates from lakes, oceans, and plants, it becomes water vapor, or moister in the air. • Water vapor is invisible • The amount of water vapor in the air is called humidity.
Humidity • The air’s ability to hold water vapor changes as the temperature of the air changes. • As temperature of the air increases, the air’s ability to hold water vapor also increases.
Relative Humidity • Relative humidity is the amount of water vapor in the air compared with the maximum amount of water vapor that the air can hold at a certain temperature. • Relative humidity is given in percents. • When air holds all of the water that it can hold at a given temperature, it is said to be saturated. • Saturated air has a relative humidity of 100%.
Relative Humidity • Water vapor and temperature affect relative humidity. • The more water vapor in the air, the higher the relative humidity. • Relative humidity decreases as the temperature rises and increases as temperature drops. • A psychrometer is an instrument that is used to measure relative humidity.