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Geography Grade 12 > Climate And Weather > Flashcards

Climate And Weather Flashcards

(60 cards)

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1
Q

Weather

A

Day to day atmospheric conditions

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2
Q

Climate

A

Average weather conditions over the long term

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3
Q

Meteorology

A

The scientific study of weather and climate

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4
Q

Mid-latitude cyclones

A

Low pressure systems assossiated with the meeting of warm and cold air.

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5
Q

Polar front

A

The boundary between warm and cold air masses at 60 degrees latitude

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6
Q

Warm front

A

Where warm air rises gradually above heavier cold air

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7
Q

Cold front

A

Where cold air wedges in under light warm air causing it to rise sharply

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8
Q

Occluded front

A

Where the cold front overtakes the warm front and the warm air is isolated from the ground

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9
Q

Cyclogenesis

A

The development of cyclonic circulation

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10
Q

Dissipate

A

Lose energy, fade away

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11
Q

Tropical cyclone

A

An intense low pressure system associated with extreme weather

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12
Q

Latent heat

A

The heat energy released when water vapour condenses into water droplets

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13
Q

Vortex

A

A rotating, whirling movement of air

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14
Q

Eye wall

A

The band of cloud surrounding the eye of a tropical cyclone

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15
Q

Storm surge

A

The offshore abnormal rise in water level caused by the strong winds of a tropical cyclone that results in coastal flooding.

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16
Q

Other names for mid-latitude cyclones? (3)

A

Frontal depressions, extratropical cyclones, temperate cyclones

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17
Q

Origin of mid-latitude cyclones

A

Form at 60N and S at the polar fronts where warm air from the subtropics meets cold air from the poles

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18
Q

Circulation of mid-latitude cyclones?

A

In the southern hemisphere, air rotates clockwise around the centre of the low pressure system. Air also converges and rises.

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19
Q

Diameter of mid-latitude cyclones?

A

From 1000 to 4000km wide

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20
Q

Movement of mid-latitude cyclones?

A

In Rossby waves from west to east within the westerly wind belt (30 to 60 latitude), travel at speeds of 60 to 90 km/hr.

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21
Q

Season of mid-latitude cyclones?

A

Occur all year round, but mostly influence our weather in winter, when cold fronts bring rain to SW Cape.
In summer they migrate south with the shifting of the suns rays and have little effect on SA’s weather.

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22
Q

What is a “family of fronts”?

A

When fronts follow closely after one another.
Occur in groups of 3 or 4.
The oldest is furthest South east.

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23
Q

Where is the worst weather in a mid-latitude cyclone experienced?

A

Closest to the centre of the low pressure.

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24
Q

How long do mind-latitude cyclones last?

A

2 to 5 days.
Even up to 14 days.

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25
Stages of mid-latitude cyclones?
Initial stage Mature stage Occluded stage Dissipating stage
26
Initial stage
Forms at the polar front: Warm, moist tropical air MEETS cold, dry polar air. These two air masses move in opposite directions. The disturbance due to the rotary movement, causes a low pressure to form at the wavepoint.
27
Mature stage
Cold and warm fronts develop. Air circulates clockwise (SH) around and is drawn into the low pressure centre and rises. Warm front: the warm air rises gradually over the cold air ahead of it. Cold front: the cold air wedges in under the warm air, forcing it to rise sharply.
28
Occluded stage
The cold front moves faster than the warm front and catches up with it, causing the warm sector air to rise. Warm air is now isolated from the ground and the low pressure centre is completely surrounded by cold air. This produces an occluded front.
29
Dissipating stage
The separation of the cyclone from the warm air eventually leads to the storm’s decay and dissipation, as only cold air remains on the surface.
30
Temperature of cold front
Decrease rapidly Move from warm to cold sector
31
Wind direction of cold front
Backs from NW to colder SW/W winds Due to clockwise rotation of the air in the southern hemisphere
32
Wind speed
Increases, gusty Strong uplift as cold air forces warm air to rise
33
Air pressure of cold front
Decreases Closer to the centre of low pressure
34
Relative humidity of cold front
Decreases, then increases when it rains Increases as colder temperature means saturation point is reached sooner.
35
Cloud cover of cold front
Increases to 8/8 Mostly cumulonimbus clouds The cloud air forces the warm air to rise sharply, so condensation occurs to great heights
36
Precipitation of cold front?
Heavy rain: Cumulonimbus clouds cause heavy rain - thunderstorms (thunder and lightning; may also have hail, if an active cold front). Rain can occur along the entire line of the front (500-600 km), known as a line squall Or Soft drizzle: Soft, penetrating drizzle if the cold front is not too steep and the warm sector is stable
37
What can result in snow on the Cape Fold mountains?
If the South Atlantic high pressure ridges in behind the frontal system, very cold winds from the south can result in snow on the Cape Fold mountains.
38
Impact of midlatitude cyclone weather systems on people, their activities and the environment?
Trees uprooted, buildings damaged, roofs ripped off homes, power lines down (no electricity), flooding, people displaced, evacuations, motor vehicle accidents, economic impact (damage to crops, yields lower), damage to infrastructure.
39
What are Tropical cyclones also referred to as? (4)
Hurricanes (US), Typhoon (SEA), cyclones, Willy-Willies (Aus)
40
What are tropical cyclones?
Intense low pressures Destructive storms Cause considerable loss of life Cause damage to property + vegetation
41
How are the names given to tropical cyclones?
• The FIRST LETTER of the name indicates how many cyclones were in the area. • They are named in alphabetical order • Eline would be the fifth cyclone in the region for the season
42
During which season do tropical cyclones occur?
• During late summer or autumn. • Warm tropical ocean temperature will be at least 26.5°C.
43
Factors necessary for tropical cyclones to form?
• Sea temperature at least 26.5°C (Heat is needed for convection) •High humidity (Latent heat released during condensation) •Unstable air (Makes condensation possible) •Little surface friction (Ocean surface - unhindered air movement) •Light variable winds (Important for development of vortex) •Air pressure below 950 hPa (Enhances convergence and rise of air) •Air divergence in upper levels (Stimulates circulation)
44
Where do tropical cyclones form?
• In tropical regions. • Over tropical oceans. • Further than 5° of the Equator. Why? Needs Coriolis force for spinning winds - no Coriolis force at the Equator
45
In what direction do tropical cyclones move?
• From EAST to WEST, in a direction AWAY from the equator. • Turn east at 30°
46
Description of tropical cyclone?
Intense low pressure systems accompanied by heavy rain, storm surges and high winds, which are extremely destructive
47
Season of tropical cyclone?
Occur during late summer and early autumn
48
Origin of tropical cyclone?
Form between 5 and 10 N and S, over warm, tropical oceans with temperatures of 26,5 C+ Not found near equator-need Coriolus force to form Warm, moist tropical air rises, providing energy for the system as latent heat is released during condensation (die out over land) - occur mostly on the east coasts of continents (warmer oceans).
49
Circulation of tropical cyclone?
Clockwise into the centre of the low pressure system ( SH). Air also rises and converges
50
Movement/path of tropical cyclone?
Westward towards higher latitudes, then they curve back eastwards at 20-30 latitude (direction + speed are unpredictable)
51
How are tropical cyclones named?
Named alphabetically in each region and each season. Also given alternating male and female names.
52
Stages of development of tropical cyclones? (4)
Formative stage (tropical depression) Immature stage (tropical storm) Mature stage (tropical cyclone) Dissipating stage (degenerating)
53
Conditions as storm approaches?
• Hurricane force winds from south in SH • Air pressure decreases • Very heavy rainfall
54
Conditions in eye of tropical cyclone?
• No wind • No clouds • No rain • Temperature increases • Lowest air pressure
55
Conditions as storm moves away in tropical cyclone?
• Wind changes to north in the SH • Storm to hurricane force winds • Air pressure increases • Heavy rainfall
56
If a hurricane is likely in your area, you should?
Listen to the radio or TV for information. Secure your home, close storm shutters and secure outdoor objects or bring them indoors. Turn off utilities if instructed to do so. Otherwise, turn the refrigerator thermostat to its coldest setting and keep its door closed. Turn off propane tanks. Avoid using the phone, except for serious emergencies, it clogs networks. Moor your boat if time permits. Ensure a supply of water for sanitary purposes such as cleaning and flushing toilets. Fill the bathtub and other larger containers with water. Find out how to keep food safe during and after an emergency. Stockpile non-perishable foods that don’t need cooking. There won’t be power. Fill the car up with fuel. Ready to evacuate when necessary.
57
Which people are most at risk during a hurricane and should evacuate? -Where should they go?
If you live in a mobile home/temporary structure (particularly hazardous-no matter how well fastened to ground) If you live in high-rise buildings (hurricane winds stronger at higher elevations) If you live on the coast, on a floodplain, near a river, on an island waterway. -Move to higher ground (inland) to avoid flooding
58
If unable to evacuate and you don’t have a wind-safe room, what should you do?
Stay indoors and away from windows and glass doors. Close all interior doors, secure and brace external doors. Keep curtains and blinds closed. Don’t be fooled if there’s a lull-could be eye of the storm-winds will pick up again. Take refuge in a small, interior room, closet or hallway on the lowest level. Lie on the floor under a table or another sturdy object. Avoid elevators.
59
Strategies to help prepare for + manage the effects of tropical cyclones?
●Good weather forecasts. ●Keep the public informed by tracking storm by means of satellites, radar etc. ●Early warning systems. ●Medical and rescue services on the alert. ●Build houses of strong materials. ●Evacuation routes and procedures must be known. ●Avoid crossing strongly flowing rivers. ●Stay indoors while the storm moves over.
60
How to recognise tropical cyclones on synoptic weather maps?
●The TC symbol in the middle ●A low pressure cell ●Circular isobar patterns ●Isobars close to each other ●On east coast ●Name of the cyclone ●Clockwise rotation ●Date - late summer/autumn ●Weather stations show: - overcast clouds (100%) - rain/thunderstorms - strong winds

Geography Grade 12 (2 decks)

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