Grade 11 Term 1 🌍 Flashcards
Learn precipitation symbols on worksheet or on p.82.
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What weather is common along the ITCZ (in terms of precipitation)?
A lot of convection rain, therefore there is often dense cloud cover of cumulonimbus clouds.
What weather is associated with a low pressure cell?
Unstable weather: rain, cumulonimbus clouds, high temperatures and high dew point temperatures.
What would a weather station look like if there is a 5 knot wind blowing from south to north?
⚫️
L
What wether is associated with a high pressure cell?
Stable weather: clear skies, no precipitation, cool to warm temperatures
What is a wind named after?
The direction it comes from.
What does it mean when isobars are close together on a synoptic weather map?
There is a strong pressure gradient (a strong wind).
Where are temperature and dew point temperature shown on a station model?
Left. Above and below the precipitation symbol.
In what 5 ways can you work out the season depicted?
Look in notes for more information.
The date
Temperatures and rainfall (east coast in Summer and west coast in Winter)
Position of anti-cyclones (HP): further South in Summer, Kalahari High often over interior in Winter
Cold fronts: associated with winter
What weather is associated with a cold front?
A wind shift from south, to south-westerly to westerly.
Cumulonimbus clouds
Unstable weather, can include brief thunderstorms
What is a cold front that has caught up to a warm front called?
An occluded front.
(Looks like: dome, spike, dome etc.)
Drawing of it is in notes.
When will the mid-latitude cyclones be further south?
Summer
When will there be a coastal low along Southern Africa’s coastline?
Summer
What is ‘an out of shape’ low pressure cell/ high pressure cell called?
LP- trough
HP- ridge
What are the names of the cells in the tri-cellular model (in order of equator to poles)?
Hadley cell, Ferrel cell, Polar cell
What does this stand for: PFJS
Polar front jet stream
What does this stand for: STJS
Sub-tropical jet stream
What does this stand for: ITCZ
Inter-tropical convergence zone
What are world pressure belts?
Warm air expands and rises in convection currents creating a low pressure at the surface where air converges. At a high pressure, cold air sinks and diverges.
What is tri-cellular circulation?
This is vertical movement of the Hadley, Ferrel and Polar Cells
What are surface winds?
Easterly and westerly winds. Wind blows from a high pressure to a low pressure along a pressure gradient force and is deflected (to the left in the Southern Hemisphere and to the right in the Northern Hemisphere) due to Coriolis Force.
What are the world’s 3 climatic zones and where are they found?
Tropical zone: 0-30*
Temperate zone: 30-60*
Polar zone: 60+
(=degrees)
What happens to sunlight at high latitudes
Heat strikes at a low, oblique angle so heat is spread over a larger area
Where is the Tropic of Cancer/ Capricorn?
23,5* N/ S
How long does the earth take to revolve around the sun once?
365,25 days
What 2 main factors affect the seasons?
Latitude and the tilt of the earth’s axis
What is the tilt of the earth’s axis?
23,5*
What is the longest day called?
Summer solstice
What do you call a day with the same length day and night?
Equinox
When are the solstices?
21 June and 21 December
When are the equinoxes?
21 March and 21 September
Note: learn ocean currents on p.53
Also in notes but less clear there.
“Test yourself” in notes
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In what directions do gyres move?
Clockwise in Northern Hemisphere
Anti-clockwise in Southern Hemisphere
What 2 sets of winds are involved in forming ocean currents?
Trade winds and Westerly Winds
Where are trade winds found?
Between 30N and 30S
From which directions do the trade winds blowing?
North east in N. Hemisphere
South east in S. Hemisphere
From which directions do Westerlies blow?
South west in N. Hemisphere
North west in S. Hemisphere
What is Coriolis Force?
The force that causes the deflection of winds due to the rotation of the earth.
What are the Horse Latitudes?
Area without Coriolis force.
Between 30N and 30S
State Ferrel’s law
Winds are deflected to their left in the Southern Hemisphere and their right in the Northern Hemisphere.
Where are the doldrums?
Won’t be in Rhenish tests
Between 5N and 5S
Note: images of surface winds are in “The atmosphere” notes (light blue)
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What is the Inter-tropical Convergence Zone?
A belt of low pressure which circles the Earth generally near the equator where the trade winds converge. Characterized by convective activity.
Along what does air flow?
Along a pressure gradient force (from HP to LP)
What 3 factors control wind?
Pressure differences, the Coriolis effect and friction
What is geostrophic flow?
The theoretical wind that would result from the exact balance between Coriolis force and PGF.
What does PGF stand for?
Pressure gradient force
In what way does geostrophic wind blow?
Parallel to the isobars (clockwise around low pressure cells and anticlockwise around high pressure cells in the Southern Hemisphere)
What is another name for an anticyclone and which way will wind blow there in the Southern Hemisphere?
High pressure cell (not if it’s a trough though?)
Anticlockwise
What does secondary circulation involve?
Upper air circulation (in upper atmosphere)
What are the 3 types of pressure belts?
ITCZ (1) Subtropical high (2) Subpolar low (2)
Note: look at synoptic weather maps in “Synoptic weather maps” worksheet (light purple). Not in the key cards but very important info
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What are isobars?
Lines on a map joining all places with the same atmospheric pressure.
What does hPa stand for?
Hectopascal
What is a mid-latitude cyclone?
A cell of low pressure that forms at the polar front.
In what way do pressure gradient winds blow?
Across isobars (HP to LP)
In which way do onshore winds blow?
Sea to land. Moist air masses.
What is a Föhn wind?
A warm, dry wind that descends the leeward side of a mountain.
What is a Föhn wind called in North America?
Snow-eater/ Chinook
What is a Föhn wind called in South Africa?
Berg wind
What is a Föhn wind called in the Andes of Argentina?
Zonda
What is a Föhn wind called in Australia?
Brick fielder
What is a Föhn wind called in the Sahara?
Sirocco
What do DALR and WALR stand for and what are they?
Dry Adiabatic Lapse Rate (1*C/ 100m)
Wet Adiabatic Lapse Rate (0,5*C/ 100m)
Name 3 effects of a Föhn wind
Dry up plants and farmlands
Cause forest fires
Melt snow➡️ avalanches
What is a monsoon?
A seasonal wind that blows in tropical regions (because of the seasonal reversal of atmospheric pressure) that brings rainfall in Summer.
Where in South East Asia does a high pressure form during Winter?
Over the Siberian Plateau, North of the Himalayan mountains
Name 3 benefits of the summer monsoon in India
Relief from the hot weather
Rain for crops
Flushes pollution from rivers
Name 4 negative features of the summer monsoon in India
Destruction of infrastructure
Destruction of property
Topsoil and crops washed away
Death
Give another name for an onshore breeze/ wind.
Sea breeze
Give another name for an offshore breeze/ wind.
Land breeze
What is an El Niño/ La Niña?
An irregularly occurring series of climatic changes affecting the equatorial Pacific region.
What happens of northern Peru and Ecuador every few years, typically in late December?
Unusually warm, nutrient-poor water appears.
What are the effects of El Niño?
Reversal of wind patterns across the Pacific
Drought in Australasia (Australia and South-East Asia)
Unseasonal heavy rain in South America
Warmer Central and East Pacific Ocean
Rising air and rain over Central Pacific
Warm temperatures in central and eastern Pacific
What are the normal conditions over the Pacific?
The tropical easterlies (trade winds) blow westward across the Pacific Ocean, dragging warm water towards Australia and South-East Asia.
Look at diagrams of normal conditions, El Niño and La Niña.
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What causes an El Niño?
A change in air pressure causes tropical easterlies (trade winds) to weaken
What are the characteristics of a La Niña?
Tropical easterlies are stronger than normal
Upwelling of cold water is increased
Heavy rainfall on the eastern side of Australia and South-East Asia and the west Pacific Ocean
Drier conditions over west coast of South America
How does an El Niño affect Africa?
Warm, dry air causing drought conditions over western and central Africa.
Sometimes heavy downpours, floods and mudslides in East Africa
How does a La Niña affect Africa?
Cool, wet conditions. Heavy rain and storms over Africa.
Good rains are welcomed by farmers. Heavy rains can cause floods
What is a cold front?
The leading edge of an approaching cold air mass
How do polar fronts develop?
Cold and hot air meet between the Polar cell and the Ferrel cell and mid-latitude cyclones form
What is an isohyet?
A line joining places of equal rainfall.
Define insolation.
Direct solar radiation falling on a unit area of the Earth’s surface
Define pressure gradient
Flow from high pressure to low pressure
