Title: WEATHER MAPS
1Weather Climate
Weather Maps
2Weather 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.
3Weather 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
4Weather 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
5Bureau of Meteorology
- http//www.bom.gov.au/
- http//www.aus-emaps.com/severe_weather.php
6Atmospheric 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
7Isobars
- 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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9Atmospheric Pressure readings
How do they get the land and sea readings?
What do all these dots form when they are linked?
10Isobars
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
11Synoptic 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.
12Synoptic 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?
13Pressure cells - are defined by the patterns
formed by isobars.
- Are these high pressure cell s or
a low pressure cells? - How can you tell?
14High 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
15High pressure cells
- Why does the air descend?
- Why does the air moves outwards?
16Typical 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
18Low 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.
19Low pressure cells
Ascending air
- Why does the air rise?
- Why does the air moves inwards?
20Typical 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
22Tropical 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).
23A cross section of a Tropical Cyclone
24 Cyclone Larry 2006
25What 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.
26Wind 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.
27Note the closeness of the isobars
Note the spaced isobars
28Reading 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
29How 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
30Wind 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.
31Wind direction
Remember we always refer to where the wind is
coming from!
Where has the wind come from?
1
2
32Wind Direction Anticyclones (High Pressure
cells)
- In the southern hemisphere winds blow outwards in
an anticlockwise direction from areas of high
pressure.
ANTICYCLONE ANTICLOCKWISE WINDS.
33Wind blows outwards in an anticlockwise direction
in areas of high pressure.
ANTICYCLONE ANTICLOCKWISE WINDS.
34Wind 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.
35Winds blow towards the centre of a low pressure
system and in a clockwise direction
LOW P. C. CYCLONE CLOCKWISE WINDS.
36Wind 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
37Identifying 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
38FRONTS
- 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.
39A warm front
40Cold 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.
41A cold front
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43Temperature 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).
44Humidity
- 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).
45Types of rainfall Convection
http//www.youtube.com/watch?vRkgThul2El8 http//
www.bbc.co.uk/schools/gcsebitesize/geography/weath
er/elementsofweatherrev6.shtml
46Types 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
47Orographic 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
48Types of rainfall Frontal
http//www.youtube.com/watch?vD88dYNFyBq8 http//
www.bbc.co.uk/schools/gcsebitesize/geography/weath
er/elementsofweatherrev6.shtml
49Flash 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
50Seasons
- 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.
51Summer weather map
Where are the different cells located?
52Winter weather map
Where are the different cells located?
53Clear 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.
54Why Do Climates Vary?
55Factors Affecting The Climate
- What makes a certain place hot, cold, wet, dry,
windy?
56Your 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
57World 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.
58Latitudehttp//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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60Altitude (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.
61Distance 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.
62Distance 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.
63Ocean 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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65Prevailing 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.
66Factors 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
67Mt Cotopaxi Ecuador's second highest mountain
68Factors Affecting Temperature and Rainfall
Mountain Barriers Distance From The Sea
Ocean Currents Prevailing Winds
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70Worldwide Climate stats
- http//www.worldreviewer.com/world-weather/
71The 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.
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78World Sunlight Map
79Interactive Game
http//www.games4geog.com/cg/climatkeyterms.swf