Developed by María Jesús Campos Fernández, Social Studies, History and Geography teacher in a bilingual section in Madrid (Spain)

1. María Jesús Campos
learningfromgeography.wikispaces.com

2. Weather
It’s
the state of the atmosphere in a certain place at a
specific time.
It is studied by Meteorology.
Meteorological phenomena combine in the
atmosphere to give rise to weather.

4. Atmospheric
Pressure and
Wind
Precipitation
Temperature
Air Masses
Weather

5. 

The sun’s energy
heats up some
parts of the Earth
more than
others.
Temperature is
how warm the air
is thanks to solar
radiation.

7. Latitude
Factors that
modify
temperature
Altitude
Proximity to
oceans

8. LATITUDE: HOW LATITUDE MODIFIES TEMPERATURE?


Because of the tilt of the Earth, solar radiation
hits the Earth directly on the Equator and at a
less angle on the Poles.
Thus, temperatures close to the Equator are
much higher than in the Poles.

9. 


These differences in
temperature create a restless
movement of air and water in
great swirling currents to
distribute heat energy from
the sun across the planet.
When air in one region is
warmer than the surrounding
air, it becomes less dense and
begins to rise, drawing more
air underneath.
Elsewhere, cooler denser air
sinks, pushing air outward to
flow along the surface and
complete the cycle.

11. ALTITUDE: HOW ALTITUDE MODIFIES TEMPERATURE?

At higher altitudes the air is thinner and loses
heat. Every 1000 metres temperature falls 6ºC.

12. PROXIMITY TO OCEANS: HOW DOES IT MODIFY
TEMPERATURE?

Water stores more heat than continents so
temperatures are often mild in coastal areas.

13. 

Temperature is
measured with a
thermometer and
expressed in
degrees
centigrade (ºC)
An isotherm is a
line that connects
points of equal
temperature at a
given date or time
on a map.

15. 


Warm area: The
highest temperatures
(over 20ºC) are
registered between
the Tropics.
Cold area: The
lowest temperatures
(less than (0º) are
registered close to
the Poles.
Temperate area:
zone in between in
which temperatures
go from 0ºC to 20ºC.

16. Atmospheric
Pressure and
Wind
Precipitation
Temperature
Air Masses
Weather

17. 

It is the weight of air
on the Earth’s
surface. The average
atmospheric
pressure at sea level
is 1013 millibars
(mb).
Air pressure
depends on the
density of the
air, that is on how
close together the
molecules of the air
are.

18. Factors that
modify
atmospheric
pressure
Temperature
Altitude

19. HOW DOES TEMPERATURE MODIFY ATMOSPHERIC
PRESSURE?




In cold air, the molecules
are more closely packed
together than in warm
air, so cold air is more
dense than warm air.
Thus, hot air weighs less
than cold air.
Since warm air is less
dense and creates less
air pressure, it will rise.
As cold air is denser and
creates greater air
pressure, it will sink.

20. 


When warm air
rises, cooler air will
often move in to
replace it. So wind
often moves from
areas where it’s colder
to areas where it’s
warmer.
When warm air rises it
originates a low
pressure area or
depression.
As warm air is rising it
takes with him water
vapour that cools and
condenses originating
clouds. That’s why
usually, depressions
are accompanied by
precipitation.

21. 
As cold air is heavier it sinks originating high
pressure areas or anticyclones. It is a drier air
so it usually brings dry weather.

24. HOW DOES ALTITUDE MODIFY ATMOSPHERIC
PRESSURE?

Air lower in the
atmosphere is more
dense than air
above, so air pressure
down low is greater
than air pressure
higher up.

25. Atmospheric
Pressure and
Wind
Precipitation
Temperature
Air Masses
Weather

26. 
In the lower layers of
the atmosphere, air
separates into air
masses which differ in
temperature and
humidity:




Close to the poles
there are cold air
masses.
Close to the Equator
there are warm air
masses.
Continental air masses
are dry.
Maritime air masses
are moist.

28. 


The boundaries
that separate air
masses are called
fronts.
Weather in the
fronts is usually
unstable.
There are:


Cold fronts
Warm fronts

29. 


A cold front appears
when a cooler mass of
air replaces at ground
level a warmer mass of
air.
As a cold front moves
into an area, the heavier
cool air pushes under
the lighter warm air that
is replacing. The warm
air becomes cooler as it
rises. If the rising is
humid enough, the
water vapor it contains
will condense into
clouds an precipitation
may fall.
As the cold front
moves, warm, moist
unstable air is usually
replaced by cold, dry
stable air.

30. 


A warm front
appears when a
warmer mass of air
moves over a cooler
mass of air.
Warm air at the
surface pushes
above the cool air
mass, making
clouds and storms.
Warm fronts bring
stormy weather.
A warm front
typically replaces
cool dry air with
warm moist air.

31. Atmospheric
Pressure and
Wind
Precipitation
Temperature
Air Masses
Weather

32. 

It is the movement of air masses.
Wind circulates between areas with different
pressures. It always circulate from the high
pressure area to the low pressure area.

33. 

The greater the
difference between
the high and low
pressure or the
shorter the distance
between the high and
low pressure
areas, the faster the
wind will blow.
Wind also blows faster
if there’s nothing in its
way, so winds are
usually stronger over
oceans or flat ground.

34. 


Although wind blows
from areas of high
pressure to areas of
low pressure, it doesn’t
blow in a straight. This
is because the Earth is
rotating.
In the northern
hemisphere, the spin of
the Earth causes the
winds to curve to the
right (to the left in the
southern hemisphere).
This is called the
coriolis effect.
So in the northern
hemisphere, winds
blow clockwise around
an area of high
pressure and counterclockwise around low
pressure.

35. TYPES OF WINDS:




Trade winds: they
always blow form the
Tropics to the Equator.
Seasonal winds: like
the monsoons which
carry heavy rain from
the Indian Ocean to the
continent in
summer, and from the
land back to the ocean
in winter.
Sea breezes: wind
blows from the land to
the sea during the day
and the other way
down during the night.
Local winds: cierzo
(Aragon), levante
(Comunidad
Valenciana, Andalucía)

36. 
Is the amount of water
that falls in a place.

It can fall as rain, snow
or hail.

It is caused by the
condensation of water
vapour on the
atmosphere. When water
vapour condenses, it
transforms into water
drops. When drops get
so heavy that the
atmosphere can not hold
them, they fall to the
ground attracted by
gravity.

37. 

Precipitation is
measured with a
rain gauge or
pluviometer and
expressed in
millimetres (mm)
An isohyet is a line
that connects points
with the same
amount of
precipitation at
given date or time
on a map.

39. Developed by María Jesús Campos
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