Download Chapter 18: Moisture, Clouds and Precipitation Name

Chapter 18: Moisture, Clouds and Precipitation
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18.1 Water in the Atmosphere
I. Water’s Changes of State
A. ___________________is any form of water that falls from a cloud.
B. When it comes to understanding atmospheric processes, _________________ is the most important
gas in the atmosphere.
C. Solid to Liquid
1. The process of changing state, such as melting ice, requires that ___________________ be
transferred in the form of _________________
2. _____________________is the energy absorbed or released during a change in state.
D. Liquid to Gas
1. ______________________is the process of changing a liquid to a gas.
2. ______________________is where a gas, like water vapor, changes to a liquid, like water.
E. Solid to Gas
1. ________________________ is the conversion of a solid directly to a gas without passing
through the liquid state.
2. ______________________ is the conversion of a vapor directly to a solid.
II. Humidity
A. ______________________is a general term for the amount of water vapor in air.
B. Saturation
1. Air is ______________________when it contains the maximum quantity of water vapor that it
can hold at any given ____________________ and _____________________.
2. When saturated, ___________ air contains more water vapor than ___________ saturated air.
C. Relative Humidity
1. _______________________ is a ratio of the air’s
actual water-vapor content compared with
the amount of water vapor air can hold at that
______________________________________
2. When the water-vapor content of air remains
constant, lowering air temperature causes an
____________________ in relative humidity,
and raising air temperature causes a decrease
in relative humidity.
D. ______Point: the temperature a parcel of air would
need to be cooled to reach ___________________
E. Measuring Humidity
1. A ____________________ is an instrument to measure relative humidity.
2. A ___________________is a hygrometer with dry- and wet-bulb thermometers. ___________
of water from the wet bulb makes air temperature appear _____________ than the dry bulb’s
measurement. The two temperatures are ______________ to determine the relative humidity.
18.2 Cloud Formation
I. Air Compression and Expansion
A. _________________ Temperature Changes: When air is allowed to expand, it ________, and when it is
compressed, it ________________.
B. Expansion and Cooling
1. ______________________ is the rate of cooling or heating that applies only to unsaturated air.
2. ______________________ is the rate of adiabatic temperature change in saturated air.
II. Processes That Lift Air: Four mechanisms that can cause air to rise are orographic _______________,
frontal ______________, convergence, and localized _____________________ lifting.
A. Orographic Lifting
1. Occurs when mountains act as ___________ to the flow of air, forcing the air to ascend.
2. The air cools adiabatically; ___________ and ____________________ may result.
B. Frontal ___________________
1. A _______________ is the boundary between two adjoining air masses having
contrasting characteristics.
C. _____________________: when air flows together and rises.
D. Localized Convective Lifting
a. Occurs where unequal surface heating causes pockets of air to ____________ because
of their buoyancy.
III. Stability:
A. ________________Differences: Stable air tends to remain in its original position, while unstable air
tends to ________.
B. Stability Measurements:
1. Air stability is determined by measuring the ____________________ of the atmosphere at
various _______________________.
2. The rate of change of air temperature with _________________is called the environmental
lapse rate.
C. Degrees of Stability: A ________________________ occurs in a layer of limited depth in the
atmosphere where the temperature increases rather than decreases with height.
D. Stability and Daily Weather: When stable air is forced above the Earth’s surface, the clouds that form
are _________________ and have little ________________ thickness compared to their
__________________ dimension.
IV. Condensation: For any form of condensation to occur, the air must be _________________.
A. Types of Surfaces:
1. Generally, there must be a _________________ for water vapor to condense on.
2. ____________________________ are tiny bits of particulate matter that serve as surfaces on
which water vapor condenses when condensation occurs in the air.
18.3 Cloud Types and Precipitation
I. Types of Cloud
A. Clouds are classified on the basis of their ___________ and _______________
1. ___________________ (cirrus = curl of hair) are clouds that are high, white, and thin.
2. Cumulus (cumulus = a pile) are clouds that consist of _______________________ cloud masses.
3. Stratus (stratus = a layer) are clouds best described as _____________________ that cover
much or all of the sky.
B. High Clouds
1. _________________ clouds are high, white, and thin.
2. _________________clouds are flat layers of clouds.
3. _________________clouds consist of fluffy masses.
C. Middle Clouds
1. _____________________ clouds are composed of rounded masses that differ from
cirrocumulus clouds in that altocumulus clouds are ___________ and ________________
2. _____________________clouds create a uniform white to gray sheet covering the sky with the
sun or moon visible as a bright spot.
D. Low Clouds
1. Stratus clouds are best described as ___________ or _______________ that cover much or all
of the sky.
2. __________________________clouds have a scalloped bottom that appears as long parallel
rolls or broken rounded patches.
3. ____________________ clouds are the main precipitation makers.
E. Clouds of Vertical Development
1. Some clouds do not fit into any one of the three height categories mentioned. Such clouds have
their ______________ in the low height range but often extend upward into the
_________________________________ altitudes.
II. Fog: a cloud with its base at or very near the ground.
A. Fog Caused by __________________: As the air cools, it becomes _______________ and drains into
low areas such as river valleys, where thick fog accumulations may occur.
B. Fog Caused by ___________________: • When ____________ air moves over _______________water,
enough moisture may evaporate from the water surface to produce saturation.
III. How Precipitation Forms: cloud droplets must grow in volume by roughly ______________________ times.
A. Cold Cloud Precipitation
1. The ____________________________ is a theory that relates the formation of precipitation to
supercooled clouds, freezing nuclei, and the different saturation levels of ice and liquid water.
2. __________________________ is the condition of water droplets that remain in the liquid
state at temperatures well below _________.
3. __________________________ is the condition of air that is more concentrated than is
normally possible under given temperature and pressure conditions.
B. Warm Precipitation Forms
1. The ________________________ process is a theory of raindrop
formation in warm clouds
(above 0oC) in which large cloud droplets collide and join
together with smaller droplets to
form a raindrop.
IV. Forms of Precipitation: The type of precipitation that reaches Earth’s surface
depends on the temperature profile in the
___________________________________ of the atmosphere.
A. Rain and Snow
1. In meteorology, the term ______________ means drops of water that fall from a cloud and
have a diameter of at least ____________
2. At very low temperatures (when the moisture content of air is low) light fluffy _________ made
up of individual _______________ ice crystals forms.
3. ________________is the fall of clear-to-translucent ice.
4. ________________ is produced in cumulonimbus clouds.
5. ____________________Hailstones begin as small ice pellets that grow by collecting
supercooled water droplets as they fall through
a cloud.