Weather is the state of the atmosphere at any point in time.
The elements of
Wind: speed and direction
Sun: intensity of sun and duration
Temperature: how hot or cold
Visibility: Mist or fog
Air Pressure: High pressure
brings stable weather. Low
pressure brings changeable
amount or type of
Water vapour is formed by the sun
warming the ocean, which causes
water to evaporate to give a gas
Once the water vapour has mixed with the
air, the air rises and cools, which causes the
water vapour to condense again into small
clouds of small water droplets.
Rain is formed after these two steps.
If temperatures are below freezing or
cold, it can be seen as sleet or snow. It can also condense as fog.
You can prove water vapour exists by
feeling some water vapour mixed through
air and wind. This way you can know that
water vapour's telling you you are miles
Climate is the average weather expected in a place
based on 30 years of data.
Weather can be dangerous: heavy winds can
cause hurricanes, droughts, etc.
The troposphere reaches up to 10km.
In the stratosphere, there is no rain because the amount
of water in the stratosphere is lower than in the
atmosphere, which means the condensation of the water
vapour that creates rain doesn't occur in that kind of
What causes the weather?
The sun heats the Earth but not
evenly, because the Earth is round
so the top and bottom don't warm
up much. Therefore during
December, the southern
hemisphere is tilted towards the
sun. When tilted towards the sun,
the hemisphere tilted towards the
sun receives a larger amount of the
sun's incoming rays. So when tilted
away, a smaller part of the rays
reflects upon the Earth, leaving it
with less thermal energy.
Places get warm because of the sun. It heats the earth, and the
earth in turn warms the air. The sun also causes wind. Thats
because the warm air raises, so chilly air rushes in from somewhere
else to take its place. Rushing air is called wind. During winter, there
is not much sun, so the weather can be chilly.
Water vapour is the second main cause of the weather. It is the
water that has been evaporated after the sun warms the
There are 3 main ways in which air is forced to rise / rain occurs.
Wind is moving air.
When the wind meets
the line of high hills or
mountains, there is
only one way to go
(windward, up). The air
rises and cools and we
get rain. The prevailing
wind is from the south
west, so a lot of relief
rainfall on the high land
along the west coast is
where our relief rainfall
The air rises because the
ground heats it. It rises as
currents of warm air. We
call these convection
currents, so we call the rain
convenctional rainfall. In
the UK we get convectional
rainfall inland in the
summer, where the ground
gets hottest, away from the
cooling effect of the sea.
When a warm air mass
meets a cold one, the
warm air is forced to
rise. The rising air
cools, the vapour
condenses. So we get
rain = frontal rainfall. It
can fall anywhere,
since air masses can
Clouds are condensed water droplets. They come in
various shapes, sizes and help inform us of what the
weather is likely to do.
Fluffy clouds = cumulolus
Wispy clouds = cirrolus
Layered clouds = stratolus
High clouds = alto
Dark clouds = nimbolus
Air pressure is a
measure of how heavy
the air is. Low pressure
means that air is rising
and it cools and
condenses to give rain
pressure means that
the air is sinking, it is
heavy and the result is
weather that changes
little from day to day.
Low pressure is a sign of unsettled weather,
the lower the pressure the stormier it will
be. High pressure brings clear skies, which
means very hot weather in the summer and
very cold weather in winter.
Polar Maritime = cold, wet
Arctic = cold, wet
Polar contintental = cold, dry
Tropical Maritime = hot, wet
tropical continental = hot, dry
If one of these sits over us, then
we have an anticyclone. High
pressure area in winter is a polar
continental, in summer it is the tropical continental.
But in reality our weather comes from the west and the
polar maritime and tropical maritime air masses fight to
pass over the UK.