EAPS Chapters 5-8

To compare air pressures from place to place on the Earth's surface, a reduction-to-sea-level adjustment is made. Consequently, on a surface weather map the assumption is made that for purposes of pressure analysis all stations are located at an altitude of _____ m above sea level.

0

Air pressure at sea level is approximately 14.7 pounds per square inch or approximately _____ kilograms per square centimeter.

1

According to the Standard Atmosphere, on average 25% of the atmosphere's mass (25% of pressure) is found above an altitude of approximately _____ km., or, stating it another way, 75% of the atmosphere's mass is found below that altitude.

10

If unsaturated (clear) air ascends 1000 m in the atmosphere, it will expand and its temperature will lower about ______ Celsius degrees. (The information in Chapter 5 of the text may also be helpful.)

10

In the United States, meteorologists currently use the millibar (mb) unit as the standard unit of air pressure (equal to a hectoPascal). Standard sea-level air pressure is _____ mb.

1013.25

Air pressure is reported in a variety of units. The air pressure unit most commonly reported to the public is based on the height of a column of mercury which exerts at its base the same pressure as the atmosphere at that place. This pressure measurement technique is adequate for many purposes because the height of the mercury column is directly proportional to air pressure. The average (standard) sea-level atmospheric pressure is ______ inches of mercury. This is equivalent to 76 cm or 760 mm of mercury.

29.92

As a general rule-of-thumb, on average, 10 inches of snow will melt down to 1 inch of liquid water. Therefore, a 32-inch snowfall will produce approximately ______ inches of liquid.

3.2

Because air pressure is determined by the weight of the overlying air, knowing air pressure values at sea level and at different altitudes makes it possible to determine the amount of atmosphere (by mass) that is above and below a particular altitude. For example, average sealevel air pressure is approximately 1000 mb. At the altitude where the pressure is 500 mb, half of the mass of an atmospheric column would be below and half above. From the Standard Atmosphere Table, this occurs at an average altitude of about _____ km above sea level.

5.5

Acid rain (or snow) occurs when the pH of the precipitation is less than

5.6

Remote sensing of precipitation amounts over the vast areas of tropical oceans is possible with data from the ______ satellite.

TRMM

By employing this sea-level correction, surface weather maps are thus constant _____ maps.

altitude

A pressure-sensitive altimeter used in aircraft to measure altitude is a(n) _____ barometer.

aneroid

The gradient wind describes in simplest terms the circulation around centers of high and low pressure at altitudes above about 1000 m (3300 ft). Viewed from above the Northern Hemisphere, air flows _____ around a high-pressure center.

clockwise

The pressure gradient force arises from a change in air pressure with distance. This force accelerates air away from regions of higher air pressure and toward regions of lower air pressure. The pressure gradient force is strongest where isobars are

closest together

The atmosphere is a continuous fluid. As surface winds spiral out of the center of a High, more air arrives by descending from above. The descending air, in turn, is replaced by air flowing into the system at higher altitudes. As Figure 8.18 illustrates, a High (anticyclone) exhibits horizontal divergence of surface winds and horizontal _____ of upper air winds.

convergence

Ascending, unsaturated air _____ at the rate of 9.8 degrees Celsius per 1000 m.

cools

Air that is saturated with water vapor has a relative humidity of 100 %. If that air is heated without adding or removing water vapor, the relative humidity

decreases

The ideal gas law is a relationship between

density, pressure, and temp

If the container in the preceding question is warmed about 10 Celsius degrees (18 Fahrenheit degrees) and left at the new temperature until the air above the water surface again becomes saturated with water vapor, the concentration of water vapor will be about ______ what it was at the lower temperature.

double

A force is a push or pull on an object; it has both magnitude and direction. Your weight, for example, is a force. The magnitude is read from a weight scale and the direction of that force is always _____ because it is the force of attraction between your mass and the mass of Earth.

downward

Lee-wave clouds form ______ of a mountain range.

downwind

Fluid friction arising from large irregular motions within the atmosphere is _____ viscosity.

eddy

Unstable air ______ vertical motion, convection, and cloud development.

enhances

Avogadro's Law states that equal volumes of gases (or gas mixtures) measured under the same conditions of temperature and pressure contain _____ number of molecules.

equal

When a volume of gas expands due to decreasing surrounding pressure, the volume undergoes

expansional cooling

Surface air pressure will _____ in regions where less air converges at the surface than ascends

fall

If air is cooled until it reaches saturation at a temperature that is below 0 °C (32 °F), the air temperature has reached the

frost point

Where isobars are curved, the centripetal force interacts with the horizontal pressure gradient force and the Coriolis Effect to produce winds that follow the same curved paths as the isobars. This is known as the _____ wind.

gradient

Hydrostatic equilibrium is the balance between the upward vertical pressure gradient force and the downward force of _____. Imbalances lead to convective motions.

gravity

For a weather radar operating in the reflectivity mode, the strongest echoes are produced by

hail

As long as there is no addition or removal of water vapor, the relative humidity of unsaturated (clear) air rises as the air temperature falls. Hence, on a clear, calm day, the relative humidity is ______ near sunrise, the coldest time of day.

highest

Cloud droplets can cool to temperatures well below 0 °C (32 °F) without freezing. When these so-called supercooled droplets coexist with ice crystals in the same cloud, the ______ grow in size. This is the basis of the Bergeron-Findeisen process that is responsible for the formation of most precipitation.

ice crystals

The Coriolis Effect varies with wind speed. If there is no air motion relative to the Earth's surface (calm conditions), there is no Coriolis Effect. As wind speed increases, the Coriolis Effect

increases

The deflection of horizontally moving air due to the effect of the Earth's rotation is greatest at the poles where the Earth's surface makes one complete 360-degree spin around the rotational axis in 24 hours. The deflection is totally absent at the equator because the Earth's rotation does not cause any turning of the Earth's surface around a vertical axis at that location. Hence, the Coriolis effect is zero at the equator and _____ as latitude increases.

increases

The combined effects of the horizontal forces described in this chapter causes Northern Hemisphere surface winds in Lows (cyclones) to spiral counterclockwise and _____ as viewed from above.

inward

Saturated (cloudy) air expands and cools as it ascends in the atmosphere (just as unsaturated air). As cloudy air rises, water vapor continually condenses as water droplets (or deposits as ice crystals) and latent heat is released to the atmosphere. Hence, ascending saturated (cloudy) air cools at a ______ rate than does ascending unsaturated (clear) air. (See also Chapter 5.)

lower

Water vapor molecules have less mass than air "molecules". As a result, surface air pressure in a humid air mass would be _____ than that in a dry air mass if their temperatures and other characteristics are the same.

lower

The scales of atmospheric circulations from smallest to largest are:

micro, meso, synoptic, planetary

In the atmosphere, cloud condensation nuclei are ______ abundant than ice-forming nuclei.

more

The surface pressure in a High can get higher over time if horizontal convergence in the system is _____ than horizontal divergence.

more

With an increase in altitude, air pressure decreases _____ rapidly in cold air than in warm air.

more

Because Earth is rotating, horizontal winds everywhere except at the equator are deflected to the right or left relative to Earth's surface. This so-called Coriolis Effect arises because the air is moving over a surface which itself is continually turning because of Earth's rotation. In the Northern Hemisphere, the Coriolis Effect causes wind blowing toward the west to turn toward the

northwest

The figure displaying the evolution of straight, balanced, horizontal flow shows the influence of the Coriolis Effect on air subjected to a horizontal pressure gradient force when neighboring isobars are straight and parallel in the Northern Hemisphere. At altitudes above the friction layer, the Coriolis balances the horizontal pressure gradient force and the air flows along a path that is _____ to the isobars. This is called the geostrophic wind.

parallel

Bands of light gray shading that indicate large water vapor content flows into hurricanes, thunderstorms and winter storms seen in water vapor imagery are called

plumes

Water in solid or liquid form that falls from clouds to the Earth's surface is known as

precipitation

Overnight radiational cooling of clear air may cause temperatures to reach saturation with stable conditions to form ______ fog.

radiation

Which one of the following particles has the greatest terminal velocity in still air?

rain drop

The sense of the Earth's rotation is counterclockwise as viewed from above the North Pole and clockwise as viewed from above the South Pole. This reversal in the sense of the Earth's rotation means that the deflection due to the Earth's rotation reverses between the Northern and Southern Hemispheres. Hence, air moving horizontally in the Northern Hemisphere turns to the _____ relative to the Earth's surface, whereas in the Southern Hemisphere, moving air turns toward the opposite direction.

right

If unsaturated air descends 1000 meters, it will compress and its temperature will ______ about 10 Celsius degrees.

rise

A sealed container with liquid water in the bottom was left standing at a constant temperature until the air above the water surface became saturated with water vapor. The resulting pressure exerted by the water vapor is known as the ______ vapor pressure. The resulting vapor pressure value is unique to that particular temperature.

saturation

Air is ______ if air parcels tend to remain at the same altitude or, if displaced vertically, tend to return to their original altitude. The other condition occurs if, once displaced vertically, air parcels continue to move away from their original altitude.

stable

Referring back to Chapter 2's figure of the atmosphere's average vertical temperature profile, the stratosphere is

stable

Water is continually cycled from one reservoir to another in the global hydrologic cycle. The process whereby liquid water vaporizes into the atmosphere is known as evaporation and the process whereby ice or snow vaporizes into the atmosphere without first becoming liquid is known as

sublimation

The water vapor in air exerts a pressure, called vapor pressure, as though it were the only gaseous constituent present. That is, water vapor exerts a pressure that is not affected by the pressures exerted by other gases present. This is described in Dalton's law which states that a mixture of gases exerts a total pressure that is the ______ of the pressures exerted by each constituent gas.

sum

Freezing rain (or drizzle) occurs when falling water drops are ______; thus, drops partially freeze when they strike cold surfaces.

supercooled

Where there is an abundance of hygroscopic nuclei in the atmosphere, clouds are likely to develop at relative humidities ______ 100%.

under

At least some of the water (in the liquid or solid form) falling from a cloud vaporizes as it passes through ______ air below the cloud base. If the water completely vaporizes before reaching the Earth's surface, the shaft of falling liquid or ice particles is known as virga.

unsaturated

If cumulus clouds (puffy clouds that build vertically) continue to develop to great altitudes, the atmosphere is

unstable

The water droplets and ice crystals that make up clouds are always falling relative to the air, yet the clouds themselves may not be falling relative to the Earth's surface. This happens because clouds are most likely to be located where ______ prevail.

updrafts

As a general rule, the heaviest precipitation falls on the ______ slopes of a mountain range.

windward