What we 'feel' outside is the actual amount of moisture (absolute humidity) in the air. Warm air can possess more water vapor (moisture) than cold air, so with the same amount of absolute/specific humidity, air will have a HIGHER relative humidity if the air is cooler, and a LOWER relative humidity if the air is warmer. In other words, it is a measure of the actual amount of water vapor in the air compared to the total amount of vapor that can exist in the air at its current temperature. Relative humidity (RH) (expressed as a percent) also measures water vapor, but RELATIVE to the temperature of the air. Absolute and specific humidity are quite similar in concept. SPECIFIC HUMIDITY refers to the weight (amount) of water vapor contained in a unit weight (amount) of air (expressed as grams of water vapor per kilogram of air). For example, a maximum of about 30 grams of water vapor can exist in a cubic meter volume of air with a temperature in the middle 80s. The higher the amount of water vapor, the higher the absolute humidity. ABSOLUTE HUMIDITY:Ībsolute humidity (expressed as grams of water vapor per cubic meter volume of air) is a measure of the actual amount of water vapor (moisture) in the air, regardless of the air's temperature. Most of the water vapor in the atmosphere is contained within the first 10,000 feet or so above the earth's surface. A major source of water vapor in Kentucky is the Gulf of Mexico. Winds in the atmosphere then transport the water vapor from one place to another. A lot or a little water vapor can be present in the air. Liquid water evaporates from oceans, lakes, rivers, plants, the ground, and fallen rain. A primary way water vapor increases in the atmosphere is through evaporation. It can exist as a liquid, solid (ice), and gas (water vapor). A Discussion of Water Vapor, Humidity, and Dewpoint, and Relationship to Precipitation

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