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WEATHER MAPS

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Title: WEATHER MAPS


1
Weather Climate
Weather Maps
2
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.

3
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

4
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

5
Bureau of Meteorology
  • http//www.bom.gov.au/
  • http//www.aus-emaps.com/severe_weather.php

6
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

7
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.

8
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9
Atmospheric Pressure readings
How do they get the land and sea readings?
What do all these dots form when they are linked?
10
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
11
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.

12
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?
13
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?

14
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

15
High pressure cells
  • Why does the air descend?
  • Why does the air moves outwards?

16
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.

17
Highs can bring rain from onshore warm waters
18
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.

19
Low pressure cells
Ascending air
  • Why does the air rise?
  • Why does the air moves inwards?

20
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.

21
  • http//www.bom.gov.au/lam/Students_Teachers/pressu
    re.shtml
  • http//www.bom.gov.au/lam/Students_Teachers/Worksh
    eet23.shtml

22
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).

23
A cross section of a Tropical Cyclone
24
Cyclone Larry 2006
25
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.

26
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.

27
Note the closeness of the isobars
Note the spaced isobars

28
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
29
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
30
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. 

31
Wind direction
Remember we always refer to where the wind is
coming from!
Where has the wind come from?
1
2
32
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.
33
Wind blows outwards in an anticlockwise direction
in areas of high pressure.
ANTICYCLONE ANTICLOCKWISE WINDS.
34
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.
35
Winds blow towards the centre of a low pressure
system and in a clockwise direction
LOW P. C. CYCLONE CLOCKWISE WINDS.
36
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

37
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

38
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.

39
A warm front
40
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.
41
A cold front
42
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43
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).

44
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).

45
Types of rainfall Convection
http//www.youtube.com/watch?vRkgThul2El8 http//
www.bbc.co.uk/schools/gcsebitesize/geography/weath
er/elementsofweatherrev6.shtml
46
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
47
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
48
Types of rainfall Frontal
http//www.youtube.com/watch?vD88dYNFyBq8 http//
www.bbc.co.uk/schools/gcsebitesize/geography/weath
er/elementsofweatherrev6.shtml
49
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

50
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.

51
Summer weather map

Where are the different cells located?
52
Winter weather map


Where are the different cells located?
53
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.
54
Why Do Climates Vary?
55
Factors Affecting The Climate
  • What makes a certain place hot, cold, wet, dry,
    windy?

56
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

57
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.

58
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.

59
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60
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.

61
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.

62
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.

63
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

64
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65
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.

66
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
67
Mt Cotopaxi Ecuador's second highest mountain
68
Factors Affecting Temperature and Rainfall
Mountain Barriers Distance From The Sea
Ocean Currents Prevailing Winds
69
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70
Worldwide Climate stats
  • http//www.worldreviewer.com/world-weather/

71
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.

72
  • 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.

73
  • 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
    23
  • http//www.schoolsobservatory.org.uk/astro/textb/p
    hys/seasonsanim.htm

74
  • 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.

75
  • 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.

76
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77
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78
World Sunlight Map
  • http//www.die.net/earth/

79
Interactive Game
http//www.games4geog.com/cg/climatkeyterms.swf
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