Meteorology Test #2
Billow clouds form along the top of a cloud layer when changes in wind speed and direction reach a critical value, and an inversion caps the cloud-forming layers.
True
On an isobaric weather chart, the spacing of the height contours indicates the magnitude of the pressure gradient force.
True
Pressure can be defined as force per unit area.
True
The atmospheric layer that is influenced by friction is called the friction layer, or planetary boundary layer.
True
Winds blow slightly inward
around surface low pressure centers in the Southern Hemisphere only
The pressure gradient force is directed from higher pressure toward lower pressure
at all places on Earth
Which of the following instruments measures pressure?
barometer
"Barometer" literally means an instrument that measures
bars
Conditional instability occurs whenever the environmental lapse rate is ____ the moist adiabatic rate and the dry adiabatic rate.
between
In an aneroid barometer, a general rule is that the higher the reading, the more likely ____ weather will occur, and the lower the reading, the better the chances are for ____ weather.
clear; inclement
The wind around a surface low pressure center in the Southern Hemisphere blows
clockwise and inward toward the center
The wind around a surface high pressure center in the Northern Hemisphere blows
clockwise and outward from the center
Lines connecting points of equal pressure are called
isobars
Which process below will change a moist layer of stable air into a deck of low stratocumulus clouds?
mixing
When cloud elements become arranged in rows they are called cloud
streets
A geostrophic wind is a wind that results from a balance between the ____ force and the ____ force
Coriolis; pressure gradient
100 pascals equals 10 millibar.
False
Centers of high atmospheric pressure are called cyclones.
False
Centripetal force describes an apparent force due to the rotation of Earth.
False
Cumulus clouds are a common phenomenon over cool water surfaces.
False
Environmental lapse rate and dry adiabatic rate are different expressions for the same phenomenon.
False
Over ocean regions, hot surface air is accompanied by surface low pressure.
False
Sinking air sometimes cools adiabatically
False
The environmental lapse rate is almost always the same as the adiabatic rate.
False
The flow of air around a high, or anticyclone is called stress flow.
False
The pressure gradient force is non-existent at the equator.
False
Meridional wind-flow patterns go
from either north-to-south or south-to-north
When the environmental lapse rate exceeds the dry adiabatic rate, the lapse rate is called
superadiabatic
The dry adiabatic rate is the rate at which
temperature changes in a rising or descending parcel of unsaturated air
In an air parcel the average speed of the molecules is directly related to the air ___ , and the molecules colliding against the parcel walls determine the air ____ inside.
temperature;pressure
In the tropics, pressure rises and falls in a regular pattern ____ a day.
twice
On a 500 millibar chart, ____ are drawn to represent horizontal changes in altitude which correspond to horizontal changes in pressure.
contour lines
The elevation where clouds form is called ____ level
condensation
The potential instability brought about by the lifting of a stable layer whose surface is humid and whose top is "dry" is called
convective instability
Because lows are also known as cyclones, the flow of air around them is often called
cyclonic flow
Atmospheric air pressure always ____ with height.
decreases
In a rising unsaturated thermal, the dew-point temperature
decreases at a slower rate than the parcel temperature
The best time of day for a farmer to burn agricultural debris for least polluted conditions is
during the afternoon
If, at your home in the Northern Hemisphere, the surface wind is blowing from the northwest, the region of lowest pressure will be to the ____ of your home.
east
The process of a rising, churning cloud mixing with cooler air is called
entrainment
An afternoon sky full of cumulus humilis clouds with little vertical growth indicates ____ weather.
fair
An example of orographic clouds would be clouds
forming on the windward slope of a mountain
Surface winds blow across isobars at an angle and the pressure gradient force is balanced by the _____ force and the Coriolis force.
frictional
If you were to take a trip during the summer from Ohio to Nevada, you would most likely observe that afternoon cumulus clouds ____ as you travel west.
have higher cloud bases
Lenticular clouds form on the ____ side of mountains
leeward
Rain shadows form on the ____ side of mountains
leeward
This level in the atmosphere where the rising air becomes warmer than the surrounding air is called the
level of free convection
On an upper-level chart cold air aloft is generally associated with ____ pressure.
low
When air is stable and close to saturation stratocumulus clouds can be produced by a process called
mixing
Pressure changes
more rapidly in the vertical direction than in the horizontal
Because of friction, surface winds move ____ winds aloft with the same pressure gradient.
more slowly than
Altocumulus castellanus appearing in the sky indicates that the mid-level of the troposphere is becoming
more unstable
Forced lifting along a topographic barrier is called ____.
orographic uplift
The unit of pressure designated by the International System (SI) of measurement is the ____.
pascal
The atmospheric layer that is influenced by friction is called the friction layer or the ______ layer.
planetary boundary
The contour lines drawn on a 500 mb chart are lines of constant
pressure
The amount of pressure change that occurs over a given horizontal distance is called the
pressure gradient
The force that would cause a stationary parcel of air to begin to move horizontally is called the
pressure gradient force
The largest amount of latent heat gets released in a ____ parcel of ____ saturated air.
rising; warm
We can generally expect the air to be _____ above areas of surface low pressure and ____ above areas of surface high pressure.
rising;sinking
Conditional instability depends on the condition of
saturation
If you live in the Northern Hemisphere and a region of surface low pressure is directly west of you, the surface wind direction at your home would probably be _____ either or _____.
south;southeast
Air which resists vertical displacements is considered to be
stable
A conditionally unstable atmosphere is ___ with respect to unsaturated air and ____ with respect to saturated air.
stable;unstable
A rapid change in pressure over a relatively short distance is called a ____ pressure gradient.
steep
Vertical mixing of air tends to ____ the environmental lapse rate
steepen
On a sunny day, an aneroid barometer would indicate "____" weather when carried to the top of a hill or mountain.
stormy
Inversions that form as air slowly sinks over a large area are called ____ inversions.
subsidence
Unlike the dry adiabatic rate, the moist adiabatic rate is not constant, but varies greatly with ___ and, hence, with moisture content.
temperature
If two air parcels at sea level have the same size but different temperatures, the colder parcel of air will have
the same pressure but higher density than the warm parcel
At Earth's surface, a parcel of air has ____ the air surrounding it
the same temperature and pressure as
A hot "bubble" of air is called a(n)
thermal
Warming and cooling of air creates density oscillations known as _____ that show up as small pressure changes near Earth's surface.
thermal tides
The vertical pressure gradient force is directed
upward
Zonal flow wind-flow patterns are associated with
west-to-east flows.
Which condition would be described as the most stable?
an inversion
An air parcel in an unstable atmosphere has ____ force acting on it.
an upward-directed
The friction layer usually extends upward to an altitude near ____ above the surface.
1,000 m
Dry adiabatic cooling and warming rates are approximately ____ of change in elevation.
10 degrees Celsius for every 1000 m
Because water is 13.6 times less dense than mercury, an atmospheric pressure of 76 cm (30 in.) of mercury would be equivalent to 1034 cm (408 in.) of water. Therefore, a water barometer resting on the ground near sea level would have to be read from a ladder over ____ tall.
10 m (33 ft)
When rising air cools to its dew-point temperature, its relative humidity typically is ____ percent.
100
Suppose the surface air temperature is 66°F. If the base of a cumulus congestus cloud directly above you is 2,000 feet, what would be the approximate temperature at an altitude of 5,000 feet above you inside the cloud? (Hint: the dry adiabatic rate is 5.5°F per 1,000 feet, the moist adiabatic rate is 3.0°F per 1,000 feet.)
46°F
The Coriolis force acts at a ____ degree angle to the wind.
90
The ____ force is an apparent force created by Earth's rotation.
Coriolis
The rate at which the actual air temperature changes with increasing height above the surface is referred to as the ____ rate.
Environmental lapse
A hot "bubble" of air that breaks away from the warm surface and rises, expanding and cooling as it ascends, is known as a low pressure riser.
False
It takes a larger column of cold, more-dense air to exert the same surface pressure as a taller column of warm, less-dense air.
False
Surface pressure is unaffected by the relationship between upper-level divergence and surface convergence.
False
_____ act as lids on vertical air motion. When they exists near the ground, stratus clouds, fog, haze, and pollutants are all kept close to the surface.
Inversions
The rate at which the temperature changes inside a rising (or descending) parcel of saturated air is called the ____ rate.
Moist adiabatic
At Earth's surface, a rising saturated air parcel cools at the
Moist adiabatic rate
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
Most thunderstorms do not extend very far into the stratosphere because the air in the stratosphere is
Stable
Inversions that form as air slowly sinks over a large area are called ____ inversions.
Subsidence
A knowledge of air stability is important because it determines
The vertical motion of air
Surface winds that blow over the ocean are closer to being geostrophic than those that blow over land.
True
The situation where rising air becomes warmer than the surrounding air is called the level of free convection.
True
Under certain conditions, a layer of altostratus may change into altocumulus.
True
Usually when a cumulonimbus cloud begins to dissipate, the bottom half of the cloud dissipates first
True
When a deep stable layer begins a short distance above the cloud base, only cumulus humilis are able to form.
True
Just above cumulus clouds, you would expect to find
a stable layer
A surface low pressure center is generally associated with ____ on an upper level isobaric chart.
a trough
An example of orographic clouds would be
clouds that form on the upwind slope of a mountain
A pascal (Pa) is the force of ____ acting on a surface area of ____.
1 Newton; 1 square meter
If rising air cools to its dew-point temperature, the relative humidity becomes ____.
100%
What is considered standard sea-level atmospheric pressure in millibars?
101.25 mb
Which environmental lapse rate represents the most unstable atmosphere in a layer of unsaturated air?
11°C per 1,000 m
If the environmental lapse rate is 5°C per 1,000 m and the temperature at Earth's surface is 25°C, then the air temperature at 2,000 m above the ground is
15°C
In a sky filled with scattered cumulus humilis clouds, rising motions are found ____ the clouds and sinking motions are found ____ the clouds
under; between
The magnitude of the Coriolis force varies with ____ and ____.
wind speed; latitude
A station at an altitude of 900 m (about 3,000 feet) above sea level measures an air pressure of 930 mb. Under normal conditions, which of the values below do you think would be the most realistic sea level pressure for this station?
1,020 mb
On rare occasions when the environmental lapse rate exceeds about ____ (the autoconvective lapse rate), convection becomes spontaneous, resulting in the automatic overturning of the air
3.4 degrees Celsius per 100 m
If the environmental lapse rate is less than the moist adiabatic rate, the atmosphere is
absolutely stable
Which cloud type below would most likely form in an unstable atmosphere?
cumulonimbus
A ridge on an upper-level isobaric chart indicates
higher-than-average heights
Isobaric surfaces are ____ in warm, less-dense air and ____in cold, more-dense air.
higher; lower
The unit of pressure most commonly found on a surface weather map is
millibars or hectopascals
On an upper-level chart the wind tends to be
parallel to the isobars or contours.
On an isobaric surface,
pressure is constant
In middle latitudes, when an area of high pressure approaches a city, surface pressure usually ____. When it moves away, pressure usually ____.
rises; falls
Convective instability is associated with the development of
severe storms, such as thunderstorms and tornadoes
Upper-level winds in the middle latitudes of both hemispheres generally blow from ____.
the west
What transfers heat upward into the atmosphere?
thermals
There is always a strong pressure gradient force directed _________.
upward
A rising parcel of air that does not exchange heat with its surroundings is an example of
An adiabatic process
A stratocumulus layer changing to a sky dotted with growing cumulus clouds often occurs as surface heating decreases later in the night during the summer.
False
If the rising air cools to its saturation point, the moisture will evaporate.
False
If you (in the Northern Hemisphere) stand with the wind aloft to your back, lower pressure will be to your right and higher pressure to your left.
False
Instruments that detect and measure pressure changes are called anemometers.
False
One millibar equals 10 pascals.
False
Station pressure and sea-level pressure can never be the same value.
False
Subsidence has no effect on atmospheric stability.
False
Subsidence inversions are just as common on Earth's surface as they are aloft.
False
The Coriolis force is the force that causes the wind to blow.
False
The atmosphere is absolutely unstable when a lifted parcel of air is colder and heavier than the air surrounding it.
False
The atmosphere is always unstable when the environmental lapse rate is less than the moist adiabatic rate.
False
The combination of warming the surface and warming the air aloft creates the greatest atmospheric stability.
False
The environmental lapse rate decreases due to cold advection at higher altitudes and daytime solar heating.
False
When the changes in wind speed and direction reach a critical value and an inversion caps the cloud-forming layers, wavelike clouds called cloud streets may form along the top of the cloud layer.
False
When the upward-directed pressure gradient force is nearly exactly balanced by the downward force of gravity, the air is said to be in centripetal equilibrium.
False
Which condition below is necessary for a layer of altostratus clouds to change into altocumulus?
The top part of the cloud deck cools while the bottom part warms.
A change in velocity of an object over a period of time is called acceleration.
True
A conditionally unstable atmosphere exists when a parcel of air can be lifted to a level where it becomes saturated, a cloud forms, and the rising parcel becomes warmer than the air surrounding it.
True
A layer of altostratus can change into one of altocumulus, if the top of the original cloud deck cools while the bottom warms.
True
A wind that blows at a constant speed parallel to curved isobars above the level of frictional influence is termed a gradient wind.
True
After being corrected for temperature, gravity, and instrument error, the barometer reading taken at a particular location and elevation is termed station pressure.
True
Air pressure decreases with height more rapidly in cold air than in warm air.
True
Cirrostratus, altostratus, nimbostratus, and stratus clouds are associated with stable atmospheric conditions.
True
Clouds help regulate Earth's energy balance by reflecting and scattering solar radiation and by absorbing Earth's infrared energy.
True
Convective instability associated with severe thunderstorms and tornadoes can be brought on by lifting a stable air layer whose surface is humid and whose top is dry.
True
Flights from San Francisco to New York City take, on average, about 30 to 45 minutes less than the return flights.
True
Forced atmospheric lifting along a topographic barrier is called orographic uplift.
True
High atmospheric pressure is normally associated with warm air aloft
True
Hydrostatic equilibrium does not exist in violent thunderstorms and tornadoes, where the air shows appreciable vertical acceleration.
True
In middle latitudes, surface pressure changes are primarily the result of large high- and low-pressure areas that move toward or away from a region.
True
In the Northern Hemisphere, the average height of contour lines on an upper-level isobaric chart tend to decrease northward.
True
In the tropics, daily (diurnal) fluctuations of pressure appears to be due primarily to the absorption of solar energy by ozone in the upper atmosphere and by water vapor in the lower atmosphere.
True
It is possible for a layer of air to be convectively unstable and absolutely stable at the same time.
True
Lines connecting points of equal pressure on a map are called isobars.
True
The altimeter and barograph are two types of aneroid barometers.
True
The angle at which surface winds cross isobars depends upon surface friction, wind speed, and the height above the surface.
True
The angle at which surface winds cross isobars is to a large degree dependent on the roughness of the terrain.
True
The elevation above the surface where the cloud first forms is called the condensation level.
True
The pressure gradient force has a direct effect on horizontal wind movements.
True
The rate at which the air temperature surrounding us decreases as we climb upward into the atmosphere is referred to as the environmental lapse rate.
True
The region on the leeward side of a mountain where precipitation is noticeably less is called a rain shadow.
True
The safest place to build an airport in a mountainous region is along a deep valley.
True
The temperature of rising air at a given level inside a cumulus cloud is normally warmer than the air around the cloud.
True
The up and down motions in layered clouds produce globular elements that give the clouds lumpy appearances.
True
Tightly packed isobars on a weather map indicate high winds.
True
When a parcel of air expands and cools, or compresses and warms, with no interchange of heat with its outside surroundings, this situation is called an adiabatic process.
True
When there is an extremely small amount of moisture in the air, the moist adiabatic rate of cooling would be almost equal to the dry adiabatic rate.
True
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
The stability of the atmosphere above the condensation level plays a major role in determining the vertical growth of a cumulus cloud. When a deep conditionally unstable layer exists above the cloud base, ____ are likely to grow.
cumulus congestus
A(n) ____ process is a process in which an air parcel expands and cools, or compresses and warms, with no interchange of heat with its surroundings.
adiabatic
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
To correctly monitor horizontal changes in air pressure, the most important correction for a mercury barometer is the correction for
altitude
Altocumulus clouds that show vertical development and produce tower-like extensions are called
altocumulus castellanus
The most common type of home barometer is called the _____ barometer.
aneroid
Another term for isobaric chart is
constant pressure chart
If upper-level divergence exceeds surface convergence, the air pressure at the center of the surface low will
decrease
The surface pressures at the bases of warm and cold columns of air are equal. Air pressure in the warm column of air will ____ with increasing height ____ in the cold column.
decrease; more slowly than
Suppose that the winds aloft are geostrophic and blowing from the north. Low pressure is located to the
east
Which of the following produces the strongest Coriolis force?
fast winds; high latitude
The winds aloft in the middle latitudes of the Southern Hemisphere generally blow
from west to east
Absolute instability results when the environmental lapse rate is ____ the ____ adiabatic rate
greater than; dry
In a conditionally unstable atmosphere, the environmental lapse rate will be ____ the moist adiabatic rate and ____ the dry adiabatic rate.
greater than; less than
Horizontal pressure variations cause air to move from areas of _____ pressure to areas of ____ pressure.
high;low
If Earth did not rotate, the wind would blow directly from regions of ____ pressure toward regions of ____ pressure.
high;low
On an upper-level chart, normally we find warm air associated with _____ pressure, and cold air associated with ____ pressure.
high;low
Warm air aloft is associated with constant pressure surfaces that are found at ____ altitudes than normal and ____ normal atmospheric pressure aloft.
higher; higher than
Which pressure unit is most commonly used in aviation?
inches of mercury
Suppose a parcel of air has a given temperature, pressure, and density. If the parcel's size remains the same while its temperature increases, then the air pressure inside the parcel will
increase
Net convergence of air would cause surface pressure to ____ and net divergence would cause surface pressure to ____.
increase; decrease
The difference between "moist" and "dry" adiabatic rates is due to the fact that
latent heat is released by a rising parcel of saturated air
According to Newton's second law, an object will always accelerate in the direction of the total force acting on it. Therefore, to determine in which direction the wind will blow, we must identify and examine all of the forces that affect the horizontal movement of air. These forces are the ____ force, the ____ force, and the Coriolis force.
pressure gradient; frictional
The Coriolis force deflects winds to the ____ in the Northern Hemisphere and to the ____ in the Southern Hemisphere.
right;left
If the atmosphere is conditionally unstable, the condition necessary to bring on instability is called
saturation
The dry adiabatic rate is ____ greater than the moist adiabatic rate.
Always
An inversion represents an extremely stable atmosphere because air that rises into the inversion will eventually become ____ and ____ dense than the surrounding air
colder; more
