Lecture 10: Clouds and Air Masses Flashcards
______ 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.
Clouds
Condensation requires ______, microscopic particles that always are present in the atmosphere.
cloud-condensation nuclei
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%
True
What 3 factors do we need to form a cloud?
Air parcel to rise
Then to cool
Increase in relative humidity to 100%
What is the description of stratus clouds.
Uniform, featureless, grey clouds that look like high fog.
What is the description of stratocummulus clouds.
Soft, grey, globular cloud masses in lines, groups, or waves.
What is the description of nimbostratus clouds?
Grey, dark, low clouds with drizzling rain.
What is the description of altostratus clouds?
Thin to thick clouds, with no halos. Sun’s outline just visible through clouds on a grey day.
What is the description of altocummulus clouds?
Clouds like patches of cotton balls, dappled, and arranged in lines or groups.
What is the description of cirrus clouds?
“Mares’ tails” clouds—wispy, feathery, with delicate fibres, streaks, or plumes.
What is the description of cirrocumulus clouds?
Clouds like veils, formed from fused sheets of ice crystals, having a milky look, with Sun and Moon halos.
What is the description of cirrocumulus clouds?
Dappled clouds in small white flakes or tufts. Occur in lines or groups, sometimes in ripples, forming a “mackerel sky.”
What is the description of cumulus clouds?
Sharply outlined, puffy, billowy, flat-based clouds with swelling tops. Associated with fair weather.
What is the description of cumulonimbus clouds?
Dense, heavy, massive clouds associated with dark thunderstorms, hard showers, and great vertical development, with towering, cirrus-topped plume blown into anvil-shaped head.
_____is a cloud layer on the ground, with visibility restricted to less than 1 km.
Fog
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
True
When radiative cooling of a surface chills the air layer directly above that surface to the dew-point temperature, creating saturated conditions, a ______ forms
radiation fog
____ is a fog that consists of supercooled water droplets that turn into rime frost on contact with freezing objects.
Rime fog
_____ fog forms when the air becomes full of ice crystals that formed by sublimation. Happens at extremely low temperatures.
Ice crystal fog
When air in one place migrates to another place where conditions are right for saturation, an ________ fog forms.
advection fog
What is an example of advection fog?
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
____ forms when moist air flows to higher elevations along a hill or mountain
Upslope fog
_____ 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
Valley fog
_____ forms when cold air lies over the warm water of a lake, an ocean surface, or even a swimming pool.
Evaporation fog
_____ is the scientific study of the atmosphere
Meteorology
_____ is a distinctive, homogeneous body of air that has taken on the moisture and temperature characteristics of its source region.
Air mass
What are the 5 types of air masses affecting North America?
Maritime polar (mP), Maritime tropical (mT), continental arctic (cA), continental polar (cP), continental tropical; only summer (cT)
What are the characteristics of mP?
Cool, humid, unstable all year
What are the characteristics of cP?
Cool, dry, moderately stable
What are the characteristics of mT?
Warm, humid, normally unstable
What are the characteristics of cT?
Hot, relatively low humidity, stable aloft, unstable at surface, turbulent in summer
What are the characteristics of cA?
very cold, very dry, very stable
True or False: Continental polar (cP) air masses form only in the Northern Hemisphere and are most developed in winter and cold-weather conditions.
True
Air flowing from different directions into the same low-pressure area is converging, displacing air upward in ______. Associated with the ITCZ
Convergent lifting
International tradewind convergent zone
_______ is air passing over warm surfaces gains buoyancy and lifts, initiating adiabatic processes.
Convectional lifting
____ 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.
Orographic lifting
_____ is when air is forced to rise at the boundary between two adjacent air masses (cold and warm front)
Frontal lifting
_____ 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.
Modification
