ATMO 201 EXAM 2 (CH 5 - 7) QUESTIONS &
ANSWERS
parcel of air - Answer -An imaginary small body of air a few meters wide that is used to
explain the behavior of air.
adiabatic process - Answer -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.
dry adiabatic rate - Answer -The rate of change of temperature in a rising or
descending unsaturated air parcel. The rate of adiabatic cooling or warming is about
10C per 1000m.
moist adiabatic rate - Answer -The rate of change of temperature in a rising or
descending saturated air parcel. The rate of cooling or warming varies but a common
value of 6C per 1000.
environmental lapse rate - Answer -the rate of decrease of air temperature with
elevation. It is most often measured with a radiosonde.
absolutely stable atmosphere - Answer -An atmospheric condition that exists when the
environmental lapse rate is less than the moist adiabatic rate. This results in a lifted
parcel of air being colder than the air around it.
subsidence inversion - Answer -A temperature inversion produced by compressional
warming—the adiabatic warming of a layer of sinking air.
neutral stability - Answer -An atmospheric condition that exists in dry air when the
environmental lapse rate equals the dry adiabatic rate. In saturated air the
environmental lapse rate equals the moist adiabatic rate.
absolutely unstable atmosphere - Answer -An atmospheric condition that exists when
the environmental lapse rate is greater than the dry adiabatic rate. This results in a lifted
parcel of air being warmer than the air around it.
conditionally unstable atmosphere - Answer -An atmospheric condition that exists when
the environmental lapse rate is less than the dry adiabatic rate but greater than the
moist adiabatic rate.
condensation level - Answer -The level above the surface marking the base of a
cummuli-form cloud
, convective instability - Answer -The state of an unsaturated layer of air where the upper
part is dry and the lower part is humid and the entire layer is lifted to a point where it
becomes saturated and unstable.
entertainment - Answer -The mixing of environmental air into a pre-existing air current
or cloud so that the environmental air becomes part of the current or cloud.
orographic uplift - Answer -The lifting of air over a topographic barrier. Clouds that form
in this lifting process are called orographic clouds.
rain shadow - Answer -The region on the leeside of a mountain where the precipitation
is noticeably less than on the windward side.
rotor clouds - Answer -A turbulent cummuliform type of cloud that appears to slowly
spin about a horizontal axis behind the leading edge of a thunderstorm's gust front.
The addition/subtraction of heat from air without external heating/cooling. - Answer -
What is an adiabatic process?
Moist adiabatic rates are usually slower because condensation in the rising air adds
latent heat. - Answer -Why are moist and dry adiabatic rates of cooling different?
When the rising air is very cold; not much moisture in the air (dry) - Answer -Under
what conditions would the moist adiabatic rate of cooling be almost equal to the dry
adiabatic rate?
The environmental lapse rate is the actual decrease of temperature with altitude, while
the dry adiabatic lapse rate is the rate at which air temperature would drop with altitude
due to expansion. - Answer -Explain the difference between environmental lapse rate
and dry adiabatic rate.
a radiosonde - Answer -How would one normally obtain the environmental lapse rate?
The atmosphere is stable when the environmental lapse rate is small. Consequently,
the atmosphere tends to become more stable as the air aloft warms or the surface air
cools. - Answer -What is a stable atmosphere and how can it form?
Clouds in a stable atmosphere tend to spread out horizontally, resulting in cirrostratus,
altostratus, nimbostratus or stratus forming in the stable air. Clouds are more likely to
grow vertically in an unstable/conditionally unstable atmosphere, as the warm air parcel
from the ground tends to keep rising upwards. - Answer -Describe the general
characteristics of clouds associated with stable and unstable atmospheres.
Any process that creates a steeper lapse rate will cause the air to become less stable.
This could be warming near the surface or cooling aloft or both. - Answer -List and
explain several processes by which a stable atmosphere can be made unstable.
ANSWERS
parcel of air - Answer -An imaginary small body of air a few meters wide that is used to
explain the behavior of air.
adiabatic process - Answer -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.
dry adiabatic rate - Answer -The rate of change of temperature in a rising or
descending unsaturated air parcel. The rate of adiabatic cooling or warming is about
10C per 1000m.
moist adiabatic rate - Answer -The rate of change of temperature in a rising or
descending saturated air parcel. The rate of cooling or warming varies but a common
value of 6C per 1000.
environmental lapse rate - Answer -the rate of decrease of air temperature with
elevation. It is most often measured with a radiosonde.
absolutely stable atmosphere - Answer -An atmospheric condition that exists when the
environmental lapse rate is less than the moist adiabatic rate. This results in a lifted
parcel of air being colder than the air around it.
subsidence inversion - Answer -A temperature inversion produced by compressional
warming—the adiabatic warming of a layer of sinking air.
neutral stability - Answer -An atmospheric condition that exists in dry air when the
environmental lapse rate equals the dry adiabatic rate. In saturated air the
environmental lapse rate equals the moist adiabatic rate.
absolutely unstable atmosphere - Answer -An atmospheric condition that exists when
the environmental lapse rate is greater than the dry adiabatic rate. This results in a lifted
parcel of air being warmer than the air around it.
conditionally unstable atmosphere - Answer -An atmospheric condition that exists when
the environmental lapse rate is less than the dry adiabatic rate but greater than the
moist adiabatic rate.
condensation level - Answer -The level above the surface marking the base of a
cummuli-form cloud
, convective instability - Answer -The state of an unsaturated layer of air where the upper
part is dry and the lower part is humid and the entire layer is lifted to a point where it
becomes saturated and unstable.
entertainment - Answer -The mixing of environmental air into a pre-existing air current
or cloud so that the environmental air becomes part of the current or cloud.
orographic uplift - Answer -The lifting of air over a topographic barrier. Clouds that form
in this lifting process are called orographic clouds.
rain shadow - Answer -The region on the leeside of a mountain where the precipitation
is noticeably less than on the windward side.
rotor clouds - Answer -A turbulent cummuliform type of cloud that appears to slowly
spin about a horizontal axis behind the leading edge of a thunderstorm's gust front.
The addition/subtraction of heat from air without external heating/cooling. - Answer -
What is an adiabatic process?
Moist adiabatic rates are usually slower because condensation in the rising air adds
latent heat. - Answer -Why are moist and dry adiabatic rates of cooling different?
When the rising air is very cold; not much moisture in the air (dry) - Answer -Under
what conditions would the moist adiabatic rate of cooling be almost equal to the dry
adiabatic rate?
The environmental lapse rate is the actual decrease of temperature with altitude, while
the dry adiabatic lapse rate is the rate at which air temperature would drop with altitude
due to expansion. - Answer -Explain the difference between environmental lapse rate
and dry adiabatic rate.
a radiosonde - Answer -How would one normally obtain the environmental lapse rate?
The atmosphere is stable when the environmental lapse rate is small. Consequently,
the atmosphere tends to become more stable as the air aloft warms or the surface air
cools. - Answer -What is a stable atmosphere and how can it form?
Clouds in a stable atmosphere tend to spread out horizontally, resulting in cirrostratus,
altostratus, nimbostratus or stratus forming in the stable air. Clouds are more likely to
grow vertically in an unstable/conditionally unstable atmosphere, as the warm air parcel
from the ground tends to keep rising upwards. - Answer -Describe the general
characteristics of clouds associated with stable and unstable atmospheres.
Any process that creates a steeper lapse rate will cause the air to become less stable.
This could be warming near the surface or cooling aloft or both. - Answer -List and
explain several processes by which a stable atmosphere can be made unstable.
