Lecture 10: Clouds and Air Masses

Question 1

______ are an aggregation of tiny moisture droplets and ice crystals that are suspended in air and are great enough in volume and concentration to be visible.

Answer 1

Clouds

Question 2

Condensation requires ______, microscopic particles that always are present in the atmosphere.

Answer 2

cloud-condensation nuclei

Question 3

True or False: Common nuclei are particles such as ash, dust, and soot. Salts can also function as nuclei and moisture may condense on salt particles at relative humidities below 100%

Answer 3

True

Question 4

What 3 factors do we need to form a cloud?

Answer 4

Air parcel to rise
Then to cool
Increase in relative humidity to 100%

Question 5

What is the description of stratus clouds.

Answer 5

Uniform, featureless, grey clouds that look like high fog.

Question 6

What is the description of stratocummulus clouds.

Answer 6

Soft, grey, globular cloud masses in lines, groups, or waves.

Question 7

What is the description of nimbostratus clouds?

Answer 7

Grey, dark, low clouds with drizzling rain.

Question 8

What is the description of altostratus clouds?

Answer 8

Thin to thick clouds, with no halos. Sun’s outline just visible through clouds on a grey day.

Question 9

What is the description of altocummulus clouds?

Answer 9

Clouds like patches of cotton balls, dappled, and arranged in lines or groups.

Question 10

What is the description of cirrus clouds?

Answer 10

“Mares’ tails” clouds—wispy, feathery, with delicate fibres, streaks, or plumes.

Question 11

What is the description of cirrocumulus clouds?

Answer 11

Clouds like veils, formed from fused sheets of ice crystals, having a milky look, with Sun and Moon halos.

Question 12

What is the description of cirrocumulus clouds?

Answer 12

Dappled clouds in small white flakes or tufts. Occur in lines or groups, sometimes in ripples, forming a “mackerel sky.”

Question 13

What is the description of cumulus clouds?

Answer 13

Sharply outlined, puffy, billowy, flat-based clouds with swelling tops. Associated with fair weather.

Question 14

What is the description of cumulonimbus clouds?

Answer 14

Dense, heavy, massive clouds associated with dark thunderstorms, hard showers, and great vertical development, with towering, cirrus-topped plume blown into anvil-shaped head.

Question 15

_____is a cloud layer on the ground, with visibility restricted to less than 1 km.

Answer 15

Fog

Question 16

True or False: The presence of fog tells us that the air temperature and the dew-point temperature at ground level are nearly identical, indicating saturated conditions

Answer 16

True

Question 17

When radiative cooling of a surface chills the air layer directly above that surface to the dew-point temperature, creating saturated conditions, a ______ forms

Answer 17

radiation fog

Question 18

____ is a fog that consists of supercooled water droplets that turn into rime frost on contact with freezing objects.

Answer 18

Rime fog

Question 19

_____ fog forms when the air becomes full of ice crystals that formed by sublimation. Happens at extremely low temperatures.

Answer 19

Ice crystal fog

Question 20

When air in one place migrates to another place where conditions are right for saturation, an ________ fog forms.

Answer 20

advection fog

Question 21

What is an example of advection fog?

Answer 21

when warm, moist air moves over cooler ocean currents, lake surfaces, or snow masses, the layer of migrating air directly above the surface becomes chilled to the dew point and fog develops

Question 22

____ forms when moist air flows to higher elevations along a hill or mountain

Answer 22

Upslope fog

Question 23

_____ occurs when cool air is denser than warm air, andit settles in low-lying areas, producing a fog in the chilled, saturated layer near the ground in the valley

Answer 23

Valley fog

Question 24

_____ forms when cold air lies over the warm water of a lake, an ocean surface, or even a swimming pool.

Answer 24

Evaporation fog

Question 25

_____ is the scientific study of the atmosphere

Answer 25

Meteorology

Question 26

_____ is a distinctive, homogeneous body of air that has taken on the moisture and temperature characteristics of its source region.

Answer 26

Air mass

Question 27

What are the 5 types of air masses affecting North America?

Answer 27

Maritime polar (mP), Maritime tropical (mT), continental arctic (cA), continental polar (cP), continental tropical; only summer (cT)

Question 28

What are the characteristics of mP?

Answer 28

Cool, humid, unstable all year

Question 29

What are the characteristics of cP?

Answer 29

Cool, dry, moderately stable

Question 30

What are the characteristics of mT?

Answer 30

Warm, humid, normally unstable

Question 31

What are the characteristics of cT?

Answer 31

Hot, relatively low humidity, stable aloft, unstable at surface, turbulent in summer

Question 32

What are the characteristics of cA?

Answer 32

very cold, very dry, very stable

Question 33

True or False: Continental polar (cP) air masses form only in the Northern Hemisphere and are most developed in winter and cold-weather conditions.

Answer 33

True

Question 34

Air flowing from different directions into the same low-pressure area is converging, displacing air upward in ______. Associated with the ITCZ

Answer 34

Convergent lifting

International tradewind convergent zone

Question 35

_______ is air passing over warm surfaces gains buoyancy and lifts, initiating adiabatic processes.

Answer 35

Convectional lifting

Question 36

____ is the uplift of a migrating air mass as it is forced to move upward over a mountain range—a topographic barrier. The lifted air cools adiabatically as it moves upslope; clouds may form and produce increased precipitation. Usually seen in southern BC.

Answer 36

Orographic lifting

Question 37

_____ is when air is forced to rise at the boundary between two adjacent air masses (cold and warm front)

Answer 37

Frontal lifting

Question 38

_____ occurs when air masses move away from their source regions their properties change, they may cool or warm, loss or gain moisture depending upon the character of the areas over which they travel.

Answer 38

Modification