Chapter 4: Atmospheric Humidity
Terms in this set (24)
The mass of water vapor in a given volume of air. It represents the density of water vapor in the air.
Actual Vapor Pressure
The pressure exerted by the water vapor molecules in a given volume of air. See Vapor pressure.
What the air temperature "feels like" for various combinations of air temperature and relative humidity.
The process by which water vapor becomes a liquid.
A process that occurs in subfreezing air when water vapor changes directly to ice without becoming a liquid first.
Dew point (dew-point temperature)
The temperature to which air must be cooled (at constant pressure and constant water vapor content) for saturation to occur.
The process by which a liquid changes into a gas.
The temperature at which the air becomes saturated with respect to ice when cooled at constant pressure and constant water vapor content.
An instrument designed to measure the air's water vapor content. The sensing part of the instrument can be hair (hair hygrometer), a plate coated with carbon (electrical hygrometer), or an infrared sensor (infrared hygrometer). See Hygrometer.
Heat Index (HI)
An index that combines air temperature and relative humidity to determine an apparent temperature—how hot it actually feels.
A physical condition induced by a person's overexposure to high air temperatures, especially when accompanied by high humidity.
A general term that refers to the air's water vapor content. (See Relative humidity.)
A model that illustrates the movement and exchange of water among the earth, atmosphere, and oceans.
An instrument designed to measure the air's water vapor content. The sensing part of the instrument can be hair (hair hygrometer), a plate coated with carbon (electrical hygrometer), or an infrared sensor (infrared hygrometer).
The ratio of the mass of water vapor in a given volume of air to the mass of dry air.
Any form of water particles—liquid or solid—that falls from the atmosphere and reaches the ground.
An instrument used to measure the water vapor content of the air. It consists of two thermometers (dry bulb and wet bulb). After whirling the instrument, the dew point and relative humidity can be obtained with the aid of tables.
The ratio of the amount of water vapor in the air compared to the amount required for saturation (at a particular temperature and pressure). The ratio of the air's actual vapor pressure to its saturation vapor pressure.
Saturation (of air)
An atmospheric condition whereby the level of water vapor is the maximum possible at the existing temperature and pressure.
Saturation vapor pressure
The maximum amount of water vapor necessary to keep moist air in equilibrium with a surface of pure water or ice. It represents the maximum amount of water vapor that the air can hold at any given temperature and pressure. (See Equilibrium vapor pressure.)
The ratio of the mass of water vapor in a given parcel to the total mass of air in the parcel.
The process whereby ice changes directly into water vapor without melting.
A condition whereby the atmosphere contains more water vapor than is needed to produce saturation with respect to a flat surface of pure water or ice, and the relative humidity is greater than 100 percent.
The lowest temperature that can be obtained by evaporating water into the air.