What happens to the temperature spread between air temperature and dew point as relative humidity increases?

As relative humidity increases, the temperature spread between air temperature and dew point decreases. This relationship occurs because relative humidity is a measure of how close the air is to being saturated with moisture.

When relative humidity is low, the air can hold more moisture, leading to a larger difference between the temperature and dew point. However, as relative humidity approaches 100%, the air is nearly saturated, meaning the temperature and dew point are closer together. In extreme cases, when the air reaches full saturation, the temperature and dew point are equal, resulting in a spread of zero.

Therefore, the correct answer highlights the direct relationship between increasing relative humidity and the decreasing temperature spread between air temperature and dew point.