Final answer:
Specific humidity measures the actual amount of water vapor in the air, while relative humidity is the ratio of current absolute humidity to the maximum possible at a given temperature, shown as a percentage. The capacity of air to hold water vapor increases with temperature, affecting relative humidity. Relative humidity can be calculated using vapor density and saturation vapor density values, and the dew point is determined when air reaches 100% relative humidity.
Step-by-step explanation:
Specific humidity is a measure of the actual amount of water vapor in the air, regardless of the air's temperature. It is usually expressed in grams of water vapor per kilogram of dry air. On the other hand, relative humidity is the ratio of the current absolute humidity to the highest possible absolute humidity at a given temperature, expressed as a percentage. This tells us how close the air is to being saturated with water vapor and is heavily dependent on temperature.
The capacity of air to hold water vapor increases with temperature. Therefore, if the temperature rises and the specific humidity remains constant, the relative humidity will decrease because warmer air can hold more water vapor before reaching saturation. Conversely, if the temperature drops, the relative humidity will increase, potentially reaching the dew point, where the air is fully saturated, water vapor starts to condense, and dew forms.
To calculate relative humidity, you can use the following formula: percent relative humidity = (vapor density/saturation vapor density) × 100. For example, if the vapor density is 9.40 g/m³ and the saturation vapor density is 23.0 g/m³, then the relative humidity is (9.40 / 23.0) × 100 = 40.87%.
The dew point is the temperature at which the air can no longer hold all of its water vapor, and some of it condenses. If you have a specific humidity value, you can find the dew point by looking at a table that shows the saturation vapor densities at various temperatures and identifying the temperature at which the specific humidity equals the saturation vapor density. For instance, if the specific humidity is 9.40 g/m³, this corresponds to a dew point of 10.0°C, since that is the temperature at which 9.40 g/m³ would be the saturation vapor density.