Weather

Question 1

Define weather:

Answer 1

Weather is the short-term, day-to-day condition of the atmosphere. Weather is a “snapshot” of atmospheric conditions

Question 2

Define Climate:

Answer 2

Climate is the long-term average (e.g., over decades) of weather conditions and extremes in a region. Minimum 30 years.

Question 3

What is the difference between weather and climate?

Answer 3

weather is a short term view, and climate is a long term view.

Question 4

What are some elements contributing to weather?

Answer 4

-Temperature
-Air pressure
-Wind speed and direction
-Relative humidity
-Seasonal factors such as insolation and –Sun angle

Question 5

Define an Air Mass:

Answer 5

Air mass is a distinctive body of air within a homogeneous mix of temperature, humidity, and stability, and it initially reflects the characteristics of its source region

Question 6

True or False: An air mass can be later impacted or modified by other areas/surfaces, over which it passes.

Answer 6

True.

Question 7

True or False: the interaction of air masses depicts weather patterns.

Answer 7

True

Question 8

How can air masses be qualified?

Answer 8

The moisture and temperature characteristics of their source regions

Question 9

What are the two moisture qualifications of an air mass?

Answer 9

M-Maritime (wet)
C-Continental (dry)

Question 10

What are the temperature qualifications of an air mass?

Answer 10

“A” for arctic, “P” for polar, “T” for tropical, “E” for equatorial, and “AA” for Antarctic.

Question 11

What does cP mean?

Answer 11

cP: continental polar.

Question 12

Give a snapshot of what air masses look like over NA in winter:

Answer 12

-mP (cool, humid, unstable all year),
-cA (very cold, very dry, stable, plays a large role in bringing the cold weather in the winter),
-cP (cold, dry, stable, and high pressure), mT (warm, humid, stable to conditionally unstable).

Question 13

Give a snapshot of what air masses look like over NA in summer:

Answer 13

-mP (cool, humid, unstable all year),
-cP (cool, dry, stable),
-mT (warm, humid, stable to conditionally unstable),
-cT (hot, low relative humidity AKA dry, stable aloft, unstable at surface, turbulent in summer)

Question 14

What is a cP?

Answer 14

continental polar (cP) air masses form only in the northern hemisphere and are most developed in winter and under cold-weather conditions. Very common over Canada in the winter, huge influence on the weather in the Canadian prairies.

Question 15

What is a mP?

Answer 15

Maritime polar (mP) air masses in the Northern Hemisphere exist over the northern oceans. Within mP air masses, cool, moist, unstable conditions prevail throughout the year.
-The Aleutian and Icelandic subpolar low-pressure cells reside within these mP air masses, also has significant influence on Canadian weather

Question 16

What are the two mT air masses?

Answer 16

Two maritime tropical (mT) air masses—the mT Gulf/Atlantic and the mT Pacific—influence North America.

Question 17

What’re the differences between the two mT air masses?

Answer 17

-The mT Gulf/Atlantic (east) air mass is active from late spring to early fall, migration of subsolar point north. Quite moist compared to the mT Pacific air masses.
-The mT Pacific (west) is generally lower in moisture content and available energy than the mT Gulf/Atlantic air mass.

Question 18

How can air masses be modified?

Answer 18

Modified depending on where they move to.As air masses migrate from source regions, their temperature and moisture characteristics modify and slowly take on the characteristics of the surface over which they pass.

Question 19

Give an example of an air mass modification:

Answer 19

A typical example is the lake-effect snow belt of the Great Lakes. As these air masses move over bodies of water, they will take on the characteristics of the warm moist lake.

Question 20

What is a Lake-Effect Snowfall an example of?

Answer 20

A lake-effect snowfall is an example of convection due to surface heating.

Question 21

What happens during a Lake-Effect Snowfall?

Answer 21

Cool air that passes over a warm water body gets heated by the water (sensible heat transfer) and it gets moistened by evaporation. Sensible heat, energy transfer into the air mass, evaporation and moisture injected in that air, moistened through evaporation, if it absorbs too much, it becomes unstable.

Question 22

Where would we find Lake-Effect Snowbelts?

Answer 22

Lake effect snowfalls often happen south of the Great Lakes in eastern North America, because the lakes are usually not covered by ice, even in the winter. Very large snowfalls can be created by this process.

Question 23

What are the Four Atmospheric Lifting Mechanisms?

Answer 23

-Convergent lifting
-Convectional lifting
-Orographic lifting
-Frontal lifting (cold and warm fronts)

Question 24

Explain what an atmospheric lifting mechanism is:

Answer 24

To form precipitation, air masses must lift and rise in altitude to reach the dew-point temperature, condenses, and form clouds.

Question 25

True or False: rising air cools, which is essential for cloud formation.

Answer 25

True

Question 26

What is Convergent Lifting?

Answer 26

Convergent uplift occurs in low pressure systems at the surface. The pressure pattern around a cyclone causes air to move toward the center of the system, where it then rises into the upper atmosphere.

Question 27

What happens during convergent lifting?

Answer 27

The air cools adiabatically, and if there is enough moisture in the air cloud will form, and perhaps precipitation. Cools adiabatically until we get condensation, as we get condensation we get the influences of latent heat.

Question 28

What is Convectional Lifting?

Answer 28

The air above the warmer surfaces is heated and rises. Warmer surfaces produce convectional lifting due to local heating.

Question 29

What is Orographic Lifting?

Answer 29

Oro means ‘mountain’. Orographic lifting occurs when air is forced to ascend upslope as it is pushed against a mountain. Air cools adiabatically. With enough uplift and moisture, we will get condensation and precipitation.

Question 30

What happens during rain shadow?

Answer 30

Orographic precipitation on the windward side of the mountains results in forests and big rivers. On the leeward side of the mountains, the air is much drier, and sinking...creating a warm but dry landscape, sinking air.

Question 31

How do the prairies experience orographic lifting?

Answer 31

Grasslands in Canadian Prairies, the dryness in the prairies is due to orographic lifting.

Question 32

Explain Frontal Lifting:

Answer 32

A front is the transition zone between two air masses of different densities. Since density differences are most often caused by temperature differences, fronts usually separate air masses with contrasting temperatures.

Question 33

___________: The leading edge of an advancing cold air mass is a cold front, named based on the air behind it.

Answer 33

Cold Front

Question 34

What happens in a cold front?

Answer 34

Cold air forces warm air aloft, less dense, therefore it will ride on top of the cold air.

Question 35

_________: The leading edge of an advancing warm air mass is a warm front. The warm air slides up and over the cold air, causing clouds to form and get progressively higher above the surface as we move away from the front.

Answer 35

Warm Front

Question 36

______________: Occurs when a warm front gets sandwiched between two colder air masses. On a model, the warm (red) front has rounded edges, where the cold (blue) front has jagged teeth.

Answer 36

Occluded Front

Question 37

What is an Extratropical Cyclone?

Answer 37

At the surface air is converging towards this low, as dictated by the pressure gradient force. Important for driving weather patterns in North America. Convergent winds spiraling due to Coriolis and pressure gradient.

Question 38

What is an extratropical cyclone called in the midlatitudes?

Answer 38

Midlatitude Cyclone

Question 39

How do we find fronts?

Answer 39

Where these air masses collide, we find fronts.

Question 40

How wide can Extratropical cyclones and fronts be?

Answer 40

which can be 1600kms wide, dominate and drive weather patterns in mid- to high latitudes.

Question 41

What is the cycle of a Midlatitude Cyclones (4)?

Answer 41

-Cyclogenesis (Birth) -Open Stage -Occluded Stage -Dissolving Stage (Death)

Question 42

What happens in the step of Cyclogenesis?

Answer 42

Cyclogenesis: convergence of cold and warm air masses, low pressure system forms. Air converging and moving into one another. cP pushing into mP air.

Question 43

What happens in the Open Stage step?

Answer 43

Open Stage: warm air moves north; cold air moves south. Counterclockwise spiraling. -Note: on average cold fronts travel faster than warm fronts (~40km/h vs. 16 – 24km/h).

Question 44

What happens in the Occluded stage?

Answer 44

Occluded stage: the cold front overtakes warm front, cold front moves faster than the warm front. As it moves, it develops. It sandwiches the warm air above.

Question 45

What happens during the Dissolving Stage?

Answer 45

Dissolving stage: the cold air mass completely cuts off the lifting mechanism for the cyclone. Warm air that was sandwich cuts off the uplift, it has nowhere to go, we get the death of that midlatitude cyclone.

Question 46

True or False: Because the polar front migrates north and south with the seasons, and because midlatitude cyclones tend to form along the polar front, the average west to east tracks of the cyclones also migrates north and south with the seasons.

Answer 46

True.