Atmospheric Moisture

Which term describes the process by which water vapor changes to the liquid state?

condensation

When water changes directly from gas to solid without occurring as a liquid, which process is taking place?

deposition

When water changes from one state to another, which process releases more heat energy?

deposition

On a clear, sunny winter day with an outside temperature of -10ºC, you hang your freshly laundered clothes outside. In the morning when you hung them out, the wet clothes quickly froze, but went to being completely dry by afternoon. What change of state has occurred in the water?

sublimation

After mowing the lawn on a hot, hazy, humid day, you get a large glass from the kitchen and fill it with ice and water. Immediately, drops of liquid water form on the outside of the glass. Which change in the state of water are you observing on your glass?

condensation

Which statement most accurately reflects the relationship between dew-point temperature and moisture in Earth’s atmosphere?

A high dew-point temperature indicates moist air.

At sea level pressure, which best expresses the relationship between temperature and saturation mixing ratio?

The warmer the air, the higher the saturation mixing ratio.

Which source provides the greatest amount of moisture to Earth’s atmosphere?

oceans

Which meteorological parameter is expressed as the ratio between the air’s actual water vapor content and the amount of water vapor required for saturation at that temperature?

relative humidity

At 20ºC (68ºF), the saturation mixing ratio is 14 g/kg. At your home weather station you measure a temperature of 20ºC (68ºF) and 10.5 g/kg of water in the air. What is the relative humidity?

75 percent

Which process occurs when a dew-point temperature that is above freezing is reached at a certain locality?

condensation

What condition is required for cloud formation in the atmosphere?

A rising parcel of air reaches its dew-point temperature.

When a parcel of air moves upward in the atmosphere, what is the result?

The air in the parcel expands and is cooled adiabatically.

Adiabatic temperature changes result from which of the following conditions in the atmosphere?

when atmospheric temperature change occurs without an accompanying increase or decrease in heat

Which is the most precise cause for the adiabatic cooling of a rising parcel of air in the atmosphere?

a decrease in atmospheric pressure

An unsaturated parcel of air in Boulder, Colorado, rises from a surface temperature of 24ºC and an elevation of 1655 m to an elevation of 4155 m without reaching the dew-point temperature. What is the temperature of the parcel at this elevation?

-1ºC

Which is not a mechanism that causes air masses to rise?

sublimation

Which mechanism causing air masses to ascend is significant in the creation of midlatitude hurricanes and cyclones?

convergence

In the winter, when warm, tropical air from the Gulf of Mexico moves northwestward, cities like Denver that are situated along the eastern side of the Rocky Mountains tend to get prodigious amounts of snow. What is the cause of these storms?

orogenic lifting

In the Pacific Northwest, western Washington state receives enough annual precipitation to be classified as rain forest, while eastern Washington is extremely dry. How do such extreme conditions exist in the same state?

Eastern Washington exists as a rainshadow desert behind the Cascade range.

Which parameter determines the elevation of the cloud base in a thundercloud?

dew point

When the environmental lapse rate in the atmosphere is greater than both the wet and dry adiabatic rates, what atmospheric condition exists?

absolute instability

In the atmosphere, the environmental lapse rate is 8ºC/1000 m. Up to 6000 m, the dry adiabatic rate is greater than the environmental lapse rate. Above this point, the wet adiabatic rate is less than the environmental lapse rate. What prediction might the local meteorologist on television make about the atmospheric stability in this situation?

The meteorologist would recognize the conditional instability of the atmosphere and issue a thunderstorm warning.

Which source of energy most directly fuels instability in Earth’s atmosphere?

heat released during condensation of water vapor

Absolute stability of Earth’s atmosphere exists when which condition is met?

The environmental lapse rate is less than the wet adiabatic rate.

Which type of air exemplifies the least stable atmospheric conditions?

warm, moist air

How would you describe the stability of the atmosphere if you noted a dry adiabatic rate of 10ºC/1000 meters, a wet adiabatic rate of 6.5ºC/1000 meters, and an environmental lapse rate of 7.8ºC/1000 meters?

Conditional instability occurs

Denver, Colorado, is situated at the foot of the Rocky Mountains. During the winters, the air can have a brown or orange appearance, known locally as the "brown cloud." It is not so common in the summer. What is the atmospheric cause of the "brown cloud"?

increased air temperature at higher altitudes

Which factor is most significant in the formation of clouds in the atmosphere?

ascent of parcels of air

In addition to shape, clouds are classified by which parameter?

altitude

Contrails produced by jet aircraft engines are most similar to which cloud type?

cirrus

Lightning, thunder, hail, and occasionally tornadoes are associated with which cloud type?

cumulonimbus

Which situation produces the flat base of cumulus clouds?

Rising air reaches the dew-point temperature.

At which altitude would you expect to observe the formation of cirrostratus clouds?

high altitudes with bases above 6000 m

While you are watching the television weather report to prepare for your geology field trip tomorrow afternoon, the weather reporter predicts the development of nimbostratus clouds. What equipment should you bring in addition to your hand lens and hammer?

a raincoat

Which type of fog is produced when air is lifted over a topographic barrier?

upslope fog

Which type of fog is produced when you breathe out on a cold winter morning and you can "see your breath"?

steam fog

Which fog types are produced by evaporation rather than cooling?

steam and frontal fogs

Advection fogs form when warm air blows over a cooler surface. Which U.S. city would be most likely to experience an advection fog?

Biloxi, MS

Living in St. Louis, Missouri, along the Mississippi River, you might be accustomed to the occurrence of fog on your morning commute to school or work during the winter. What type of fog would you expect to find forming in St. Louis?

valley fog

In the middle latitudes during the summer, cirrus clouds are composed of which form of water?

ice crystals

In which cloud type might you expect to find a co-existing mixture of ice crystals and supercooled water?

cumulonimbus

In which cloud type could you observe the activity of both the Bergeron process and the collision-coalescence process on a summer day in the middle latitudes?

cumulonimbus

Precipitation in the middle latitudes can be induced by the Bergeron process year round, as long as which condition exists in the atmosphere?

as long as ice crystals can form in the upper parts of cumulonimbus clouds

On a winter morning you wake to find the trees, sidewalks, roads, and cars in your neighborhood covered with a layer of ice. Since the possibility of snow was forecast, what was the cause of the ice glaze?

Water became supercooled and froze on contact.

To be classified as rain, water droplets that fall from a cloud must be of what minimum diameter?

0.5 mm

Most rainfall originates in which types of clouds?

cumulonimbus and nimbostratus

Dendrites, needles, and sector plates are representative of which type of precipitation?

snow

In addition to poor visibility and heavy snowfall, blizzard conditions are characterized by which additional parameter?

wind speeds greater than 56 kph (35 mph)

Delicate frostlike accumulations of ice form as supercooled cloud or fog droplets encounter objects and freeze on contact. What do we call this type of precipitation?

rime

In cross section, concentric layering can be observed in hailstones. How does this type of layering develop?

Hailstones can move up and down in cumulonimbus clouds and with each upward trip, another layer of ice is added.

In analyzing the layers in a hailstone, you find that some layers are milky white and others are clear. What is the explanation for the color variation in the layers?

The milky white layers are produced by the rapid freezing of tiny droplets on the hailstone that trap air, while the clear layers form when larger droplets collide with it.