Ag Earth Science – Chapter 18.1 18.1 Vocabulary
precipitation • Any form of water that falls from a cloud
latent heat • The energy absorbed or released during a change in state
evaporation • The process of converting a liquid to a gas
condensation • The change of state from a gas to a liquid
sublimation • The conversion of a solid directly to a gas without passing through the liquid stage
deposition • The process by which water vapor is changed directly to a solid without passing through the liquid state
humidity • A general term referring to water vapor in the air but not to a liquid droplets of fog, cloud, or rain
saturated • The state of air that contains the maximum quality of water vapor that it can hold at any given temperature and pressure.
relative humidity • The ratio of the air’s water-vapor content to its water-vapor capacity
dew point • The temperature to which air has to be cooled in order to reach saturation
hygrometer • An instrument designed to measure relative humidity
Water in the Atmosphere • When it comes to understanding atmospheric processes, water vapor is the most important gas in the atmosphere • Precipitation– any form of water that falls from a cloud (rain, sleet, hail, snow, etc..)
Water Changes in State • Solid to Liquid • The process of changing state requires that the energy is transferred in the form of heat • Latent heat – “hidden” heat. The energy absorbed or released during a change in state
Water Changes in State • Liquid to Gas • Evaporation– the process of changing a liquid to a gas • Condensation– the process where water vapor changes to a liquid
Water Changes in State • Solid to a Gas • Sublimation– conversion of a solid directly to a gas without passing through the liquid state • Deposition– conversion of a vapor directly to a solid
Humidity • Humidity – the amount of water vapor in the air • Saturation • Saturated- The state of air that contains the maximum quality of water vapor that it can hold at any given temperature and pressure. • When saturated, warm air contains more water vapor than saturated cold air
Humidity • Relative Humidity • Relative humidity is a ratio of the air’s actual water-vapor content compared with the amount of air can hold at that temperature and pressure. • To summarize, when the water-vapor content of air remains constant, lowering air temperature causes an increase in relative humidity, and raising air temperature causes a decrease in relative humidity.
Humidity • Dew Point • The temperature to which a parcel of air would need to be cooled to reach saturation
Humidity • Measuring Humidity • Hygrometer- A tool that measures humidity
Ag Earth Science – Chapter 18.2 18.2 Vocabulary
dry adiabatic rate • The rate of adiabatic cooling or warming in unsaturated air
wet adiabatic rate • The rate of adiabatic temperature change in saturated air
orographic lifting • Mountains acting as barriers to the flow of air, forcing the air to ascend
front • The boundary between two adjoining air masses having contrasting characteristics
temperature inversion • A layer of limited depth in the atmosphere of limited depth where the temperature increases rather than decreases with height
condensation nuclei • Tiny bits of particulate matter that serve as surfaces on which water vapors condenses
Air Compression and Expansion • Adiabatic Temperature Changes • When air is allowed to expand, it cools, and when it is compressed, it warms
Air Compression and Expansion • Expansion and Cooling • As you travel from earth’s surface upward through the atmosphere, the atmospheric pressure decreases. • Ascending air = cools and Descending air = warms
Air Compression and Expansion • Expansion and Cooling • Dry adiabatic rate – the rate of cooling or heating of dry air (fast) • Wet adiabatic rate – The rate of cooling or heating of saturated air (slow)
Processes That Lift Air • Four mechanisms that can cause air to rise are orographic lifting, frontal wedging, convergence, and localized convective lifting.
Processes That Lift Air • Orographic Lifting • Elevated terrains, such as mountains, that act as barriers to air flow (forcing air to ascend)
Processes That Lift Air • Frontal Wedging • Cooler, denser air acts as a barrier over which the warmer, less dense air rises • Front– boundary between two different air masses (example – cold/warm air masses)
Processes That Lift Air • Convergence • The collision of contrasting air masses that causes the air to rise
Processes That Lift Air • Localized Convective Lifting • The process that produces rising thermals (localized)
Stability • Stable air tends to remain in its original position, while unstable air tends to rise. • Air stability is determined by measuring the temperature of the atmosphere at various heights.
Stability • Air is stable when the temperature decreases gradually with increasing altitude • Temperature inversion – air temperature actually increases with height
Condensation • Condensation happens when water vapor in the air changes to a liquid (fog, dew, clouds) • For any form of condensation to occur, the air must be saturated • Condensation nuclei - Tiny bits of particulate matter that serve as surfaces on which water vapors condenses
Ag Earth Science – Chapter 18.3 18.3 Vocabulary
cirrus • 1 of 3 basic cloud forms. Very high clouds that are thin, delicate ice-crystal clouds that have veil-like patches or thin, wispy fibers
cumulus • 1 of 3 basic cloud forms. They are billowy individual clouds with flat bases.
stratus • 1 of 3 basic cloud forms. They are sheets or layers that cover much or all of the sky.
Bergeron process • A theory that relates the formation of precipitation to supercooled clouds, freezing nuclei, and the different saturation levels of ice and liquid water.