WEATHER MAPS

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Weather Climate
Weather Maps
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Weather and Climate

• Weather is the state of the atmosphere at any
  one place or time. This includes humidity,
  temperature, sunshine hours, cloud cover,
  precipitation (any moisture reaching the earths
  surface). This includes rain, sleet, snow, hail,
  dew and frost.
• Song
• http//www.youtube.com/watch?vc3MKsTLnTKc

• Climate is the average or long term weather
  conditions of a region. It is the result of years
  of research into data.

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Weather or Climate
Weather
Climate

• Hot and dry conditions, together with strong
  winds, led to Bushfires near Wagga.
• At this time of year Darwin usually experiences
  hot and wet weather.
• The maximum temperature in Moscow today is -23oC
• On Monday night a southerly change arrived about
  1030pm

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Weather or Climate
Weather
Climate

• Tully in Queensland is Australias wettest town.
• September was chosen for the 2000 Olympics
  because that month usually has the best weather.
• On New Years Day the temperature in Sydney was
  45oC
• Sydney receives more rain per year than London

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Bureau of Meteorology

• http//www.bom.gov.au/
• http//www.aus-emaps.com/severe_weather.php

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Atmospheric pressure

• Atmospheric pressure or barometric pressure is
  the pressure exerted by the weight of the air on
  the earths surface.
• Atmospheric pressure is measured in hectopascals
  (hPa).
• Atmospheric pressure is mapped to form isobars.
• http//www.juicygeography.co.uk/animations.htmdow
  nloads/flash/highpressure.swf

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Isobars

• Are lines on a synoptic chart joining places of
  equal atmospheric pressure.
• To estimate atmospheric pressure you need to
  refer to the two nearest isobars. e.g. if point
  A is situated half way between 1020 hPa and
  1024 hPa, A would be gt 1020 but lt 1024 hPa.

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Atmospheric Pressure readings
How do they get the land and sea readings?
What do all these dots form when they are linked?
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Isobars
How do you work out which are high pressure cells
and which are low pressure cells?
An isobar is a line on a map joining places of
equal atmospheric pressure
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Synoptic Charts

• Synoptic charts or weather maps provide a
  snapshot of the weather experienced at a
  particular place at a certain time.
• They show information relating to air pressure,
  air masses and fronts, cloud cover, wind speed,
  wind direction and rainfall.
• This information allows us to make predictions
  relating to temperature, humidity, ocean
  conditions and the likely weather for the next
  few days.

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Synoptic Charts
Synoptic Charts
What does the shading refer to?
What is the wind speed and direction?
What is this feature?
What is the air pressure?
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Pressure cells - are defined by the patterns
formed by isobars.

• Are these high pressure cell s or
  a low pressure cells?
• How can you tell?

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High pressure cells (anticyclones)

• occur where atmospheric pressure increases
  towards the centre of the system. High pressure
  systems are characterised by light winds, clear
  skies, dry weather and a high diurnal (daily)
  temperature range.
• A ridge is an extension of high pressure from a
  high pressure system.
• http//www.bom.gov.au/weather/national/charts/syno
  ptic.shtml

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High pressure cells

• Why does the air descend?
• Why does the air moves outwards?

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Typical weather associated with High pressure

• light winds
• clear skies, dry weather
• higher diurnal (daily) temperature range i.e. hot
  days (sun rays maximum effect)
• cool nights (because of lack of cloud cover).
• Frosts are likely in winter.

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Highs can bring rain from onshore warm waters
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Low pressure cells (cyclones or depressions)

• occur where atmospheric pressure decreases
  towards the centre of the system.
• Low pressure systems are associated with
  stronger winds, cloudy skies, rain
• a lower diurnal temperature range.
• A trough is an extension of low pressure from a
  low pressure system.

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Low pressure cells
Ascending air

• Why does the air rise?
• Why does the air moves inwards?

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Typical weather associated with Low pressure

• strong winds, cloudy skies, rain and a lower
  diurnal (daily) temperature range i.e. mild
  temperatures (sun does not have maximum effect
  because of cloud cover, heat trapped in at
  night).
• Frosts are unlikely.

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• http//www.bom.gov.au/lam/Students_Teachers/pressu
  re.shtml
• http//www.bom.gov.au/lam/Students_Teachers/Worksh
  eet23.shtml

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Tropical cyclones (T.C.)

• Are a very intense low pressure system. They
  generate very strong winds, produce rough seas
  and heavy rains
• Wide spread damage occurs if they make landfall
  (contact with land).

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A cross section of a Tropical Cyclone
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Cyclone Larry 2006
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What is wind?

• Wind is the movement of air masses (common bodies
  of air) from high pressure areas (highs) to low
  pressure areas (lows). The effect of this
  movement of air is to rebalance the pressure in
  the atmosphere.
• Note that
• the greater the difference between the high and
  the low pressure, the greater the wind speed will
  be, and
• the closer together the isobars are on the
  weather map, the stronger the winds will be.

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Wind speed

• is determined by the closeness of the isobars.
  The closer the isobars the stronger the winds.
• A steep pressure gradient exists where isobars
  are close together.
• If isobars are far apart a place will generally
  experience light winds. This is called a slight
  pressure gradient.

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Note the closeness of the isobars
Note the spaced isobars

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Reading Wind Direction on a Weather Map

• Not where its going too
• x

Sydney
Easterly v (Remember that we name our wind
direction on where the wind came from)
N
Close up of a map
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How to Read Wind Speed on a Weather map
To work out the wind speed of an area, all you
need to do is match up the wind speed symbol
found on the map with the symbol found in the key
A
The wind speed at point A is 5 km/hr
Legend- Wind Speed
30 km/hr
5 km/hr
10 km/hr
Calm
20 km/hr
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Wind direction

• Wind is named according to the direction the wind
  is coming from, e.g. south southerly.
• Wind direction is largely determined by the
  location of pressure systems. 

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Wind direction
Remember we always refer to where the wind is
coming from!
Where has the wind come from?
1
2
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Wind Direction Anticyclones (High Pressure
cells)

• In the southern hemisphere winds blow outwards in
  an anticlockwise direction from areas of high
  pressure.

ANTICYCLONE ANTICLOCKWISE WINDS.
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Wind blows outwards in an anticlockwise direction
in areas of high pressure.
ANTICYCLONE ANTICLOCKWISE WINDS.
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Wind Direction Depressions (Low pressure cells)

• In the southern hemisphere winds associated with
  low pressure systems blow in a clockwise
  direction towards the centre of the system. 

LOW T. C. CYCLONE CLOCKWISE WINDS.
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Winds blow towards the centre of a low pressure
system and in a clockwise direction
LOW P. C. CYCLONE CLOCKWISE WINDS.
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Wind indicators

• Wind indicators show wind speed and direction.
• The feather indicates wind speed
• The shaft indicates the direction from which the
  wind is coming
• The black dot is the place that is experiencing
  the windy conditions

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Identifying wind direction

• First - Identify the type of pressure system.
• Southern Hemisphere
• LOW clockwise
• HIGH anticlockwise.
• (the reverse is true in the northern hemisphere)
• Wind, generally speaking, moves across the
  isobars

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FRONTS

• A front is the leading edge of change. They are
  the border zone between warm and cold air. There
  are two types of fronts
• Warm fronts occur when warm air is pushed into a
  cold air mass. These are very rare in Australia.
  They result in drizzle and light rain over a few
  days.

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A warm front
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Cold fronts are far more common in Australia and
occur when cold air is pushed into a warm air
mass. This forces the warm air to rise causing a
number of changes(a) Decrease in temperature
cold air replaces warm air.(b) Change in wind
direction and sometimes speed.(c) Build up of
cumulonimbus or rain bearing clouds.(d) Increase
in humidity corresponding to a build up of
clouds.(e) Probability of rain.
Make up an acronym to remember these changes.
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A cold front
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Temperature and humidity

• are related to the wind. Winds pick up the
  characteristics of where they form sea or land
  these are called source regions
• Remember
• Winds off the land are generally hotter and
  drier.
• Winds off the sea tend to be cooler and wetter
  (greater moisture greater humidity).

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Humidity

• Humidity is the amount of water vapour in the
  atmosphere
• A high humidity means there is a lot of water
  vapour, and a low humidity means a little.
• The humidity level varies with temperature. The
  warmer air is, the more moisture the air can hold
  as vapour. The colder the air is, the less
  moisture the air can hold.
• Humidity is measured as a percentage, relative to
  the saturation point where the air can hold no
  more water vapour (i.e. 100 percent humidity).

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Types of rainfall Convection
http//www.youtube.com/watch?vRkgThul2El8 http//
www.bbc.co.uk/schools/gcsebitesize/geography/weath
er/elementsofweatherrev6.shtml
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Types of rainfall Orographic
http//www.youtube.com/watch?vBVykQfRC_aI http//
www.bbc.co.uk/schools/gcsebitesize/geography/weath
er/elementsofweatherrev6.shtml http//www.radioblo
gclub.com/open/51998/elevation_u2/U2_-_Elevation
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Orographic Rainfall
The air mass is forced to rise as it hits the
mountain and condenses into clouds
The air mass, now drier, flows down the leeward
side of the mountains
Warm moist air approaches a mountain barrier
Orographic rainfall occurs on the windward side
of the mountains
The dry air mass becomes warmer, with little
chance of rain. Deserts are often found on the
leeward side of large mountain ranges
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Types of rainfall Frontal
http//www.youtube.com/watch?vD88dYNFyBq8 http//
www.bbc.co.uk/schools/gcsebitesize/geography/weath
er/elementsofweatherrev6.shtml
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Flash video on types of rainfall

• Show Weather Rainfall wmv
• http//blip.tv/scripts/flash/blipplayer.swf?autoSt
  artfalsefilehttp//blip.tv/file/get/Gatm-Rainfa
  ll922.flv?source3

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Seasons

• are determined by the location of various
  pressure systems.
• Remember 
• Summer Lows over Northern Australia and Highs
  over Southern Australia.
• Winter Highs over Northern Australia and Lows
  over Southern Australia.

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Summer weather map

Where are the different cells located?
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Winter weather map


Where are the different cells located?
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Clear skies allow the suns rays to have maximum
effect. Daytime temperatures are usually high.
At night, clear skies allow heat to be lost
causing temperatures to fall. In winter frosts
are likely.
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Why Do Climates Vary?
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Factors Affecting The Climate

• What makes a certain place hot, cold, wet, dry,
  windy?

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Your Ideas

• On the A4 paper provided and working in pairs
• Quickly sketch as many ideas as you can as what
  might cause temperature and rainfall to be
  different at various places.
• You have 3 minutes

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World Pattern of Climate

• The climate of a particular place on the earths
  surface depends on 5 main factors.
• Latitude
• radiation from the sun is stronger and more
  direct at the equator. Places at the equator are
  therefore generally hotter than the places near
  the poles. Also seasonal differences are more
  obvious away from the equator.

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Latitudehttp//people.cas.sc.edu/carbone/modules/
mods4car/ccontrol/controls/latitude.html

• The suns rays are concentrated at the equator
  but spread out at the poles.

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Altitude (elevation)

• The air is generally thinner and therefore colder
  higher up in the mountains than it is at sea
  level. Also precipitation (rainfall and snowfall)
  is generally affected by mountain ranges as moist
  air will be forced to rise over the mountains
  (orographic rainfall). This will cause the air to
  cool and then condense into cloud.

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Distance from the sea

• The ocean acts as a stabilising influence on
  temperatures as the sea heats and cools more
  slowly than the land. Thus diurnal (daily) and
  annual (yearly) ranges of temperature are smaller
  near the coast and greater in inland areas. This
  means that inland areas generally have hotter
  summers and colder winters than coastal areas.
  Also moist air near the coast may result in more
  rainfall in coastal areas than places inland.

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Distance from the Sea

• In the summer, the sun heats the land quickly but
  it takes longer to heat up the water which is
  large and deep.
• http//people.cas.sc.edu/carbone/modules/mods4car/
  ccontrol/controls/landwater1.html
• However, the water stores heat for longer and so
  in winter, the temperature of the sea is warmer
  relative to the land and so keeps coastal places
  warmer.

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Ocean Currents

• Cold ocean currents cool the air and generally
  cause dry conditions along the coastline. Warm
  ocean currents will warm the air and cause
  warmer, wetter conditions.
• http//people.cas.sc.edu/carbone/modules/mods4car/
  ccontrol/controls/ocean.html

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Prevailing Winds

• These are the winds that blow most often.
• Winds can affect temperature and precipitation.
• Winds blowing over tropical oceans bring warm and
  wet weather.
• Winds blowing from the poles and over land bring
  cold and dry weather.

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Factors Affecting Temperature
Add the Title
Latitude Length of Day Night
Seasonal Differences Elevation
Draw up this table using a full page
Draw simple annotated sketches describing each
factor
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Mt Cotopaxi Ecuador's second highest mountain
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Factors Affecting Temperature and Rainfall
Mountain Barriers Distance From The Sea
Ocean Currents Prevailing Winds
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Worldwide Climate stats

• http//www.worldreviewer.com/world-weather/

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The Seasons

• Seasons are created by the combination of the
  earths tilt and its orbit around the sun.
• The distance between the earth and sun is about
  149 million kms. The earth rotates around the sun
  in an elliptical, or oval shaped path and takes
  about 365 days or 1 year to complete an orbit.

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• The earth also rotates in an anti-clockwise
  direction about its north-south axis, an
  imaginary line that runs between the poles. It
  takes 24 hours for the earth to spin around once,
  and this rotation creates day and night. When one
  half of the world is in darkness, the other is in
  daylight.

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• The earth is also tilted about 23.5 degrees on
  its axis. So, depending on the time of year,
  certain latitudes of the earth incline toward the
  sun more than others. Throughout the year
  different areas, particularly those that are far
  from the equator, receive more or less solar
  radiation. If the earth did not tilt, we would
  not have seasons.
• Seasons animations http//www.school-portal.co.uk/
  GroupDownloadFile.asp?GroupId12426ResourceID404
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• http//www.schoolsobservatory.org.uk/astro/textb/p
  hys/seasonsanim.htm

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• During summer in the Northern Hemisphere the
  longest day (the summer solstice) occurs when the
  sun is directly over the tropic of Cancer. As the
  earth continues its year long orbit the North
  Pole tilts away from the sun, and the South Pole
  tilts towards the sun.

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• The equinox is when the sun is directly over the
  equator. The Northern Hemisphere winter solstice
  (the shortest day) occurs when the sun is over
  the Tropic of Capricorn.

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World Sunlight Map

• http//www.die.net/earth/

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Interactive Game
http//www.games4geog.com/cg/climatkeyterms.swf