Chapter 5: Clouds and Stability
An example of orographic clouds would be:
clouds forming on the windward slope of a mountain
The dry adiabatic rate is the rate at which
temperature changes in a rising or descending parcel of unsaturated air
If unsaturated stable air is lifted to a level where it becomes saturated and unstable, this type of instability is called:
conditional instability
In a rising thermal, the dew-point temperature
decreases at a slower rate than the parcel temperature
The rate at which the actual air temperature changes with increasing height above the surface is referred to as the
environmental lapse rate
orographic uplift
forced lifting along a topographic layer
parcel of air
small volume of air
Most thunderstorms do not extend very far into the stratosphere because the air in the stratosphere is
stable
A conditionally unstable atmosphere is ____ with respect to unsaturated air and ____ with respect to saturated air.
stable, unstable
If you observe large raindrops hitting the ground, you could probably say that the cloud overhead was ____ and had ____ updrafts.
thick, strong
absolutely stable atmosphere
when the rising air is colder and heavier than the air around it- when the environmental lapse rate is less than moist adiabatic rate (6C)
When the environmental lapse rate decreases more rapidly with height than the dry adiabatic rate, the atmosphere is
absolutely unstable
Which of the following is not a way of producing clouds?
air motions caused by subsidence
Which of the following sets of conditions would produce a cumulus cloud with the lowest base?
air temperature 90°F, dew point temperature 60°F
The temperature of a rising air parcel
always cools due to expansion
What would be the height of the base of a cumulus cloud when the surface air temperature is 45°C and the dew point is 25°C?
2500
condensation level
the elevation where the could first forms
If an air parcel is given a small push upward and it continues to move upward on its own accord, the atmosphere is said to be
unstable
rain shadow
warmer air, leeward side of mountain, less precipitation
absolutely unstable atmosphere
when rising air is warmer and less dense; environmental lapse rate is greater than the dry adiabatic rate
If a parcel of unsaturated air with a temperature of 30°C rises from the surface to an altitude of 1000 m, the unsaturated parcel temperature at this altitude would be about:
10°C colder than at the surface
Which of the following environmental lapse rates would represent the most unstable atmosphere in a layer of unsaturated air?
11°C per 1000 m
If the environmental lapse rate is 5°C per 1000 m and the temperature at the earth's surface is 25°C, then the air temperature at 2000 m above the ground is
15 C
Suppose the surface air temperature is 66°F. If the base of a cumulus congestus cloud directly above you is 2000 feet, what would be the approximate temperature at an altitude of 5000 feet above you inside the cloud?
46 F
Why do cumulonimbus clouds (thunderstorms) often have flat tops?
Cumulonimbus clouds can grow to such a height that they encounter the bottom of the stratosphere, which is extremely stable with rising temperatures with altitude (inversion). The rising cumulonimbus cannot enter the stratosphere and hence spread out
How does atmospheric stability influence the formation of lake effect snowstorms?
Lake effect storms form when cold, stable air passes over a warm, moist surface. The heat added from below causes the lapse rate to increase (become less stable) while the mositure added from below becomes the source of the eventual precipitation.
Which of the following conditions would be described as the most stable?
an inversion
dry adiabatic rate
as long as the air remains unsaturated (relative humidity is less than 100), the rate remains constant at 10 C per 1000 m
The vertical motion of air caused by sun heating the ground is called:
convection
Which set of conditions, working together, will make the atmosphere the most stable?
cool the surface and warm the air aloft
Which cloud type below would most likely form in an unstable atmosphere?
cumulonimbus
In a conditionally unstable atmosphere, the environmental lapse rate will be ____ than the moist adiabatic rate and ____ than the dry adiabatic rate.
greater, less
neutral stability
if the environmental lapse rate is exactly equal to the dry adiabatic rate, rising or sinking unsaturated air will cool or warm at the same rate as the air around it
subsidence inversion
inversions that form as air slowly sinks over a large area
moist adiabatic rate
is the rising air cools to dew point, it reaches 100 percent humidity. cloud forms and latent heat is released. 6C per 1000m.
The reason that rising saturated air cools at a lesser rate than rising unsaturated air is
latent heat is released by rising saturated air
convective instability
lifting a stable layer with a dry top and moist surface, potential instability
Which condition below could make a layer of air more unstable?
mix the air in the layer, life the entire air layer, cool the upper part of the layer
entrainent
mixing of cooling air into a rising cloud, increases the rate at which the rising cloud cool
The rate at which the temperature changes inside a rising (or descending) parcel of saturated air is called the
moist adiabatic lapse rate
environmental lapse rate
rate at which the air temperature will be changing around us if we were to climb up in the atmosphere
What two sets of conditions, working together, will make the atmosphere the most unstable?
warm the surface and cool the air aloft
conditionally unstable, potential
when rising air is unsaturated, the atmosphere is stable because the parcel is colder than its surroundings; saturated air rising is saturated, the atmosphere is unstable because the parcel is warmer than its surroundings; occurs when environmental lapse rate is between the moist and dry rate
List and explain several processes by which a stable atmosphere can be made unstable.
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.
Why are moist and dry adiabatic rates of cooling different?
Dry adiabatic rate is roughly 10 C/km while the moist adiabatic rate is usually slower (around 6 C/Km) as condensation in the rising air adds latent heat
adiabatic process
IF A PARCEL OF AIR EXPANDS AND COOLS, OR COMPRESSES AND WARMS, WITH NO INTERCHANGE OF HEAT WITH ITS SURROUNDINGS. as long as the air remains unsaturated (relative humidity is less than 100), the rate remains constant at 10 C per 1000 m
Explain the difference between environmental lapse rate and dry adiabatic rate
The environmental lapse rate is the actual decrease of temperature with altitude. This is often meaured by instrumented balloon. The dry adiabatic lapse rate is the rate at which air temperature would drop with altitude due to expansion.
If an air parcel is given a small push upward and it falls back to its original position, the atmosphere is said to be
stable
Which cloud type would most likely form in absolutely stable air?
stratus
Which cloud would most likely produce drizzle?
stratus
What is the adiabatic process?
the addition/ subtraction of heat form air without external heating/ cooling
The difference between the moist and dry adiabatic rates is due to
the fact that latent heat is released by a rising parcel of saturated air
