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Geography > Week five > Flashcards

Week five Flashcards

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U.S. Geography flashcards World Geography flashcards
1
Q

Pressure Gradient Force (PGF)

A

Areas of high and low pressure occur because of uneven heating of the Earth’s surface

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2
Q

Implication: Convection loops

A
  • Created by unequal heating and cooling of the surface
  • Pressure gradient controls horizontal air movement
  • Air temperature controls vertical air movement
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3
Q

Coriolis effect

A
  • Is an apparent force caused by the Earth’s rotation
  • Object in motion on the surface always appear to be deflected to the right in the N Hemisphere
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4
Q

Coriolis “force”

A

Coriolis force is always perpendicular to the wind

As wind speed increases, Coriolis force increases to reach a maximum
magnitude when its equal to the pressure gradient force

C.F=PGF then wind blows parallel to the isobars with low pressure to the
left if you are in the Northern hemisphere

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5
Q

Geostrophic Wind

A

With no friction, upper atmospheric winds are geostrophic
- In other words, upper level winds run parallel to the isobars, with low pressure to the left when you are unfacing the wind in the Northern hemisphere

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6
Q

Friction Force

A

Friction from the surface slows wind speed and combines with the other forces to influence wind direction

The effect of friction extends to about 500m above the surface.

It explains the difference between surface winds and upper level winds.

Frictions slows down wind.
C.F<PGF so the wind does not blow parallel to the isobars

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7
Q

A low pressure centre

A

A low-pressure area, low or depression, is a region where the atmospheric pressure is lower than that of surrounding locations.

(see flash card)

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8
Q

A high pressure centre

A

Is a region where the atmospheric pressure is higher than that of surrounding locations.

(see flash card)

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8
Q

A high pressure centre

A

Is a region where the atmospheric pressure is higher than that of surrounding locations.

(see flash card)

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9
Q

Cyclones and anti-cyclones

A

Cyclones spin in opposite directions in the Northern and Southern Hemispheres due to the Coriolis effect

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10
Q

Example: Sea and land breeze

A

See breeze: afternoon wind that beings cool air off the water towards the land

Land breeze: nighttime wind that brings cooler air from land towards the water

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11
Q

Global surface patterns
1. Equatorial Low-Pressure Trough

A
  • High insolation warms equatorial air; air rises and
    produces a zone of low pressure
  • air from both hemispheres flows toward the surface
    low and moves aloft as part of the Hadley cell (and
    is then drawn poleward by the pressure gradient)
  • this area of convergence is known as the
    intertropical convergence zone (ITCZ)
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12
Q
  1. Subtropical High-Pressure Belts
A
  • air in descending part of Hadley cell is heated by
    compression and becomes drier
  • the surface air diverging from the subtropical highs
    generate Earth’s principle surface winds:
  • Mid-latitude westerlies
  • Tropical trade winds
  • Like the ITCZ, the high-pressure cells “follow” the
    Sun, migrating by 5-10° in latitude
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13
Q
  1. Sub-polar Low-Pressure Cells
A
  • dominant in the winter, weaker in the summer
  • the contrast between cold, dry air masses and warm,
    moist air masses forms the polar front
  • low-pressure cyclones are created by cooling and
    condensation of warm air forced aloft
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14
Q
  1. Polar High-Pressure Cells
A
  • Weak high-pressure cells with little energy
  • Winds move away from the polar region in an
    anti-cyclonic direction producing the polar easterlies
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15
Q

Upper Atmospheric Circulation

A

Two important facts explain upper level winds:
* Pressure decreases less rapidly with height in warmer air
* Differential heating causes air to flow poleward

Therefore, the pressure gradient is greater at altitude and winds tend to be stronger.

16
Q

Jet streams

A

Jet streams are narrow, high speed upper level air flows.

The jet stream is a river of fast moving
air in the upper atmosphere. It steers storms and moves
weather patterns across the globe.

17
Q

Jet streams and climate change

A

Jet stream is driven partly by the temperature differential between the
Arctic and the mid-latitudes.

If the temperature differential is large then the jet stream speeds up (zonal flow).

If the temperature differential reduces because of a warming Arctic then the jet stream weakens (trough/ridge) flow.

When the jet stream goes up (ridge) we see warm and dry weather. When the jet stream takes dip (trough) we see cooler and wetter weather.

18
Q

Rossby waves

A

The undulations of the upper-level westerly winds

Seen from space, Rossby waves have about half the rotational speed of Earth.

19
Q

Water Cycle and Precipitation

A

Hydrologic cycle
- Movement of water among the great global reservoirs

20
Q

States of water

A
  • A change of state from solid to liquid or liquid to gas absorbs latent heat from the surroundings
    • That means atent heat is released when clouds from (condensation) and absorbed when water evaporates from the plant’s surface

Condensation releases energy

21
Q

Humidity

A
  • The measure of the water vapour in the air
    • The maximum quantity of moisture that air can hold increases with the air temperature

Relative humidity = Actual water vapour X 100 / Maximum water vapour possible at that air temperature

22
Q

Relative Humidity

A
  • Imagine temperatures increasing over the day. The relative humidity would decline even if the amount of water vapour In the air stayed the same. This is because warmer air cab hold more water
    When it is 100% it means that air cannot hold more water particles
23
Q

Dew point temperature

A

The temperature at which a mass of air holds its maximum capacity of water vapour.

24
Q

What do we use coasters?

A
  • When cooling air reaches the dew point temperature condensation begins, forming dew or frost.
  • End up with frost under 0 degrees
25
Q

Example: Dew point and humidity

A

Relative humidity is often lower during the day

  • T <Td and Td > 0 degrees C then dew formation
  • T<Td, and Td<0 degrees C then frozen dew formations
26
Q

Adiabatic Process

A
  • An adiabatic process is a change in temperature within a gas that occurs only as a result of a change in pressure.
  • This is important in studying weather and the motion of air because atmospheric pressure decreases with altitude.
  • If you lift a parcel of air away from the surface, the pressure on the parcel decreases
  • In an adiabatic process, there is no exchange of heat with the surrounding environment.
27
Q

Vertical air motion

A
  • Imagine there is an area of low pressure or convergence at the surface, causing air to rise
  • Will it warm and contract or be cold and expand
28
Q

Fog

A

A cloud layer close to the surface, formed when the air and dew point temperatures are nearly identical

29
Q

Radiation fog

A

This forms when a surface cools the air directly above, often form at night.

A valley fog, in which cold air descends down a valley, is like a
radiation fog.

30
Q

Advection fog

A

This forms when air migrates to a place where the conditions allow saturation to occur. This happens along some coastlines and is called a sea
fog. (where?)

31
Q

Forms of precipitation

A

Once we have lifted air and generated a cloud, precipitation is possible.

Outside of the tropics, almost all precipitation begins as snow or ice.

The precipitation form on the surface depends on the temperature profile or the environmental lapse rate

32
Q

Atmospheric Stability

A

Stability is the tendency of an air parcel, either to remain in place or change vertical position

Stable = resists vertical movement, returns to starting place if disturbed

Unstable = continues to rise until reaching an altitude where air has similar density

33
Q

Absolute instability:

A
  • Air parcel is warmer than the surrounding environment
  • ELR>DALR>MALR
  • Clouds with vertical development form (cumuliform)
  • It is associated with thunderstorms and precipitation
34
Q

Absolute stability:

A

Air parcel is cooler than the surrounding environment
- ELR<MALR<DALR
- Clouds with poor vertical development may form (stratiform)
- It is associated with calm weather

35
Q

Making it rain

A

A parcel of air may be rise through convergence (a low), convection (local heating) a collision of air masses, or a physical barrier

Geography (8 decks)

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