Final answer:
The term for the ratio of water vapor in the air to the amount needed for saturation at a given temperature is called relative humidity. This measure is critical for meteorologists to predict weather, as it influences the formation of fog, dew, and the efficacy of evaporation in daily tasks.
Step-by-step explanation:
Understanding Relative Humidity
Relative humidity is a key term used by meteorologists to determine the amount of water vapor in the air relative to the maximum amount that the air can hold at a given temperature. When relative humidity reaches 100%, the air has reached saturation and evaporation is inhibited. This level of humidity is crucial in weather prediction as it can affect the likelihood of precipitation, fog, and dew formation. For instance, relative humidity increases in the evening as temperatures drop, which can lead to the dew point where condensation occurs if water droplets are suspended in the air. Additionally, understanding relative humidity is practical for everyday life, such as knowing that using a blow dryer with hot air is more effective for drying hair because warm air can hold more water vapor than cold air, thus improving evaporation.
The temperature at which air containing a certain amount of water vapor reaches 100% relative humidity is known as the dew point. This concept is important because it helps to forecast weather conditions such as fog or frost, which occur when the air temperature falls to the dew point and water vapor condenses into liquid droplets or ice crystals.