Chapter 25 Questions:
What is the name of the cold, dry air mass that affects the northern United States in the winter?
A continental polar air mass.
How do clouds form?
A parcel of air cools, the air becomes saturated, and condensation of cloud drops begins.
Explain how a convection cycle is generated.
Air is warmed near the ground, rises, and cools, becomes denser than the surrounding air, then sinks back to the ground again.
The density of air is generally given as mass per unit volume − for example, kilograms per cubic meter (kg/m3). Compare the following two dry air parcels at the same elevation: air parcel 1 has a temperature of 48 ∘F; and air parcel 2 has a temperature of 89 ∘F. Which air mass is more dense?
Air parcel 1
Why does relative humidity increase at night?
Air temperature decreases at night, this decreases the maximum capacity for water vapor in air and increases the relative humidity.
What is the eye of a hurricane?
Area of low pressure
Which of the following clouds appears at highest altitude? Stratus, Nimbostratus, Altocumulus, and Cirrus
Cirrus
What does the image below demonstrate? (Fog on Bridge)
Condensation
What is the difference between humidity and relative humidity?
Humidity is the amount of water in the air; relative humidity is what percent of the maximum capacity of water is in the air.
As air temperature decreases, does relative humidity increase, decrease, or stay the same?
Increase
Does a rain shadow occur on the windward or the leeward side of a mountain range? Explain.
Leeward, the rising air on the windward side expands, cools, reaches saturation, and produces rain, leaving dry air to descend on the leeward side.
Which of the following is not involved in weather forecasting?
Local climate.
What is the name for a front that occurs when a cold front and warm front merge?
Occluded
What happens to relative humidity when temperature increases?
Relative humidity decreases
As air temperature increases, what happens to relative humidity?
Relative humidity decreases.
What happens to relative humidity when air temperature decreases?
Relative humidity increases
What happens to the relative humidity of a rising air parcel at the lifting condensation level?
Relative humidity increases to 100% and the air parcel is saturated.
When dew point is high, what happens to relative humidity?
Relative humidity increases.
What produces the cumulus clouds we see in the sky?
Rising air currents.
The sky is overcast, and it is raining. What type of cloud is above you: nimbostratus or cumulonimbus?
The clouds are nimbostratus.
Briefly describe how thunder and lightning develop.
Water drops interact with each other and air to separate electric charges. The electric charges flow together producing lightning. Lightning heats and expands the air creating thunder.
Under what conditions does orographic precipitation occur?
Wind blows air up a slope where it expands, cools, becomes saturated, and condenses to form rain.
A thunderstorm cloud grows upward as it is fed by updrafts of rising warm air. The cloud droplets within the cloud grow larger and heavier until they eventually begin to fall as rain. The falling rain creates
a cold downdraft, which, when coupled with the rising updraft, makes up a storm cell within the cloud.
Which air parcel will have the greater temperature change as it rises in the atmosphere:
a dry air parcel
Atmospheric processes do not always involve significant exchanges of heat. When heat transfer is zero, or nearly zero, we call the atmospheric process
adiabatic.
In order for clouds to form, _______.
air must first be lifted
A front is a contact zone between two different air masses. When two opposing front types (warm/cold) overtake one another and merge, it produces _______.
an occluded front
Which produces precipitation: a rising moist air mass, a descending moist air mass, or both?
both, a rising moist air mass and a descending moist air mass
On a weather map, areas of high pressure (H on a map) are where air tends to sink. This air tends to produce _______.
clear skies and fair weather
An air mass that is heated from contact with surface "hot spots" becomes warmer than the air surrounding it. This can result in
convectional lifting.
What cloud form is associated with thunderstorms?
cumulonimbus
When air rises and moves to a region of lower pressure, the air
expands.
When air contains as much water vapor as it can possibly hold, the air
is saturated.
Compared to cold air, warm air is able to "hold" more water vapor because _______.
it has a higher saturation vapor pressure
The three basic ingredients for thunderstorm formation are _______.
moisture, rising unstable air, and a lifting mechanism that provides a nudge
As rising air cools, its ability to hold water vapor decreases and the relative humidity
of the rising air increases.
What happens to pressure and temperature of an air parcel aloft as it descends in the atmosphere?
pressure and temperature increase
Name ways in which thermal energy in air can be decreased.
radiation to space and evaporation of raindrops, conduction to cold ground, expansion of the air
Heat can be subtracted from air by
radiation to space, by evaporation of rain falling through dry air, or by contact with cold surfaces.
Condensation is more likely to occur in cool air because _______.
slower moving water vapor molecules come in contact, leading to increased saturation and relative humidity
Name ways in which thermal energy in air can be increased.
solar radiation, moisture condensation, conduction from warm ground, compression of the air
What factors are responsible for condensation?
the ambient temperature at or below the dew point; cloud condensation nuclei
Precipitation such as rain, sleet, and snow, comes from clouds. But not all clouds produce precipitation. Water droplets fall out of clouds when
the droplets become large enough to resist updrafts, the upward movement of air.
Hurricanes gain energy from
the heat released by the condensation of water
A temperature inversion occurs when
the upper regions of the atmosphere are warm and the lower regions are cool.
