"ENVIRONMENTAL LAPSE RATE",
"The rate of decrease in air temperature with altitude. It is most often measured with a radiosonde.",
"WINDWARD SIDE",
"The side of an object facing into the wind.",
"SATURATED ADIABATS",
"Lines on a tephigram (or other thermodynamic chart) that show the saturated adiabatic lapse rate for rising and descending air.",
"PARCEL OF AIR",
"A fictional small volume of air used to show the behaviour of air.",
"CLOUD STREETS",
"Lines or rows of cumuliform clouds.",
"LIFTING CONDENSATION LEVEL (LCL)",
"The altitude where a rising parcel of air becomes saturated as it cools at the dry adiabatic lapse rate.",
"SUBSIDENCE INVERSION",
"A temperature inversion produced by adiabatic warming of a layer of sinking air. It frequently occurs in sinking air associated with an anticyclone.",
"TERMINAL VELOCITY",
"The constant speed obtained by a falling object when the upward drag on the object balances the downward force of gravity.",
"BILLOW CLOUDS",
"Also called Kelvin–Helmholtz wave clouds. Broad, nearly parallel lines of wavelike clouds oriented at right angles to the wind.",
"LEVEL OF FREE CONVECTION",
"The level in the atmosphere where a lifted air parcel becomes warmer than its surroundings in a conditionally unstable atmosphere.",
"SUBSIDENCE",
"The slow sinking of air, usually associated with high-pressure areas.",
"CONDENSATION LEVEL",
"The level above the surface marking the base of a cumuliform cloud.",
"OROGRAPHIC UPLIFT",
"Air rising over a topographic barrier (mountains or hills).",
"SUBSIDENCE INVERSIONS",
"A temperature inversion produced by adiabatic warming of a layer of sinking air. It frequently occurs in sinking air associated with an anticyclone.",
"BUOYANT FORCE",
"An upward force exerted on an air parcel when there are differences in air density, most often created when there is a difference in air temperature between the parcel and the surrounding air.",
"STABLE AIR",
"See Absolutely stable atmosphere. An atmospheric condition that exists when the environmental lapse rate is less than the saturated adiabatic lapse rate. This results in a lifted parcel of air being colder than the air around it.",
"ABSOLUTELY STABLE ATMOSPHERE",
"An atmospheric condition that exists when the environmental lapse rate is less than the saturated adiabatic lapse rate. This results in a lifted parcel of air being colder than the air around it.",
"ENTRAINMENT",
"To transfer air to an organized air current from the surrounding atmosphere.",
"LEEWARD SIDE",
"The side of an object facing away from the wind.",
"STABLE",
"See Absolutely stable atmosphere. An atmospheric condition that exists when the environmental lapse rate is less than the saturated adiabatic lapse rate. This results in a lifted parcel of air being colder than the air around it.",
"ABSOLUTELY UNSTABLE",
"An atmospheric condition that exists when the environmental lapse rate is greater than the dry adiabatic lapse rate. This results in a lifted parcel of air being warmer than the air around it.",
"LIFTING CONDENSATION LEVEL",
"The altitude where a rising parcel of air becomes saturated as it cools at the dry adiabatic lapse rate.",
"SOUNDING",
"An upper-air observation, such as a radiosonde (weather balloon) observation. It is also a vertical profile of an atmospheric variable, such as temperature or wind.",
"RAIN SHADOW",
"The region on the downwind (lee) side of a mountain where the precipitation is noticeably less than on the upwind (windward) side.",
"ADIABATIC PROCESS",
"A process that takes place without a transfer of heat between the system (such as an air parcel) and its surroundings. In an adiabatic process, compression always results in warming, and expansion results in cooling.",
"RADIOSONDE",
"A balloon-borne instrument that measures and transmits pressure, temperature, and humidity to a ground-based receiving station to produce a sounding.",
"UNSTABLE AIR",
"See Absolutely unstable atmosphere. An atmospheric condition that exists when the environmental lapse rate is greater than the dry adiabatic lapse rate. This results in a lifted parcel of air being warmer than the air around it.",
"CONDITIONALLY UNSTABLE ATMOSPHERE",
"Also called conditional instability. An atmospheric condition that exists when the environmental lapse rate is less than the dry adiabatic lapse rate but greater than the saturated adiabatic lapse rate.",
"ROTOR CLOUDS",
"A turbulent cumuliform type of cloud that forms on the downwind side of large mountain ranges. The air in the cloud rotates about an axis parallel to the range.",
"ABSOLUTELY UNSTABLE ATMOSPHERE",
"An atmospheric condition that exists when the environmental lapse rate is greater than the dry adiabatic lapse rate. This results in a lifted parcel of air being warmer than the air around it.",
"ABSOLUTELY STABLE",
"An atmospheric condition that exists when the environmental lapse rate is less than the saturated adiabatic lapse rate. This results in a lifted parcel of air being colder than the air around it.",
"DRY ADIABATIC LAPSE RATE",
"The rate at which an unsaturated air parcel cools as it rises and warms as it descends. It is 9.8C° per 1000 m change in altitude.",
"SATURATED ADIABATIC LAPSE RATE",
"In saturated air parcels, it is the rate of cooling with increasing altitude in rising air and warming with decreasing altitude in descending air. The rate varies with temperature and pressure but it is always less than the dry adiabatic lapse rate since latent heat release partly offsets the adiabatic cooling. A typical value is 6C°⁢K/m.",
"NEUTRAL STABILITY",
"A type of atmospheric stability where a rising parcel of air has the same temperature as its surroundings. Analyzing stability involves comparing rising air characteristics with the environmental lapse rate, dry adiabatic lapse rate, and saturated adiabatic lapse rate.",
"CONDITIONALLY UNSTABLE",
"Also called conditional instability. An atmospheric condition that exists when the environmental lapse rate is less than the dry adiabatic lapse rate but greater than the saturated adiabatic lapse rate.",
"CONVECTIVE INSTABILITY",
"A type of atmospheric instability caused by a rising air layer that consists of cold, dry air above warm nearly saturated air. When the layer rises, the warm, moist air becomes saturated; this releases latent heat and makes the layer unstable.",
"DRY ADIABATIC",
"Lines of constant potential temperature on an adiabatic chart (e.g., a tephigram) that show the dry adiabatic lapse rate for rising or descending air.",
"POTENTIAL TEMPERATURE",
"The temperature of a parcel of air that is lowered adiabatically (according to the dry adiabatic lapse rate) from its original position to a pressure of 1000 hPa."