STUDY_SHEET_2_CHAPTER_6-8_GENS_320.pdf - CHAPTER 6 Humidity...

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CHAPTER 6 Humidity is a measure of moisture, or water vapor in the air. Equation %( RH) = AC / MC (x 100%) AC = actual moisture MC= Max moisture in the air Specific Humidity: refers to the mass of water vapor (in grams) per mass of air (in kilograms) at any specified temperature. Because it is measured in mass, specific humidity is not affected by changes in temperature or pressure, such as when an air parcel rises to higher elevations. Specific humidity stays constant despite volume changes. Temperature of the atmosphere: The temperature of the atmosphere decreases with increasing altitude at an average rate of about 6.5 degrees C/km (or 3.5 degrees F/1000 ft) up to about 16 km (10 Miles). This region is called the Troposphere. Stability refers to the tendency of an air parcel, with its water-vapor cargo, either to remain in place or to change vertical position by ascending (rising) or descending (falling). Radiosondes balloons make such temperature measurements between the air parcel and the surrounding air Lapse rate: The temperature of the air in the troposphere decreases with altitude, and the rate of this temperature decrease with height is called the lapse rate. Normal lapse rate is 6.5 degrees C / km or (3.5 F/ 1000ft.). Adiabatic: means occurring without a loss or gain of heat. The warming and cooling rate for a parcel of expanding or compressing air Dry Adiabatic Rate: (DAR) is the rate at which dry air cools by expansion (if ascending) or heats by compression (if descending). DAR is 10 degrees C per 1000 m (5.5 F per 1000 ft). Moist Adiabatic Rate: (MAR) is the average rate at which ascending air that is moist (saturated) cools by expansion. The average MAR is 6 degrees C per 1000 m (3.3 F per 1000 ft.). In saturated air parcel, latent heat of condensation is liberated as sensible heat, which reduces the adiabatic rate of cooling. Water Vapor: A concentration of invisible gas made from water. They become visible only when they transform into larger liquid or solid particles, such as cloud droplets and ice crystals. Condensation: The changing of water vapor into liquid water. Evaporation: The process of liquid water becoming water vapor. Latent means hidden
Latent heat vaporization: The amount of heat necessary to change one kilogram of a liquid into a gas. Phase change Latent heat of fusion: The amount of heat necessary to change one kilogram of a solid into a liquid at the same temperature. Aerosols: Tiny suspended solid particles (dust, smoke, etc.) or liquid droplets that enter the atmosphere from either natural or human sources, such as the burning of fossil fuels. Pollutants: Any gaseous, chemical, or organic matter that contaminates the atmosphere, soil, or water. Air density: The ratio of the mass of a substance to the volume occupied by it. Air density is usually expressed as g/cm3or kg/m3.

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