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geography ppt for weather and climate with detailed descriptions..
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The Weather
Observing and recording
Powerpoint Presentation © Pitsford Hall weather stationNorthamptonshire Grammar SchoolAbridged version without video clips
What is weather?
Weather describes the state of the atmosphere at any particular time.
Weather can be described in terms of temperature, precipitation (snow, rain & hail), wind speed and direction, visibility and cloud amounts.
What is Climate?
Climate describes the average weather of a particular part of the world at different times of the year
In Britain we would expect cool summers and mild winters with moderate rainfall throughout the year
The Weather Station
A weather station makes continuous measurements of different aspects of the weather.
Weather stations use standard instruments so that their readings can be compared.
HOWEVER…
You can make weather measurements with equipment a lot cheaper and simpler than the kit shown on the previous slide which is an official Met Office station. Please see www.metlink.org for more information.
Temperature
Temperature is recorded using thermometers housed inside a Stevenson screen
Weather stations record both air temperature and the temperature of the ground
Temperature: The Stevenson Screen
Why is the screen painted white?
Why is it raised on legs above the ground?
Why has it got louvred sides?
Precipitation
Rainfall, snow, hail and fog.
Rainfall is measured in a raingauge.
Some raingauges record rainfall automatically whilst others are emptied everyday by an observer
Wind
The direction and strength of the wind are both measured
A wind vane measures direction
An anemometer records strength
Wind strength can also be measured using the Beaufort Scale
The Beaufort Scale
Pressure
Pressure is the weight of the atmosphere
When air rises pressure falls
When air sinks pressure increases
Pressure controls the type of weather
Barometers and barographs record pressure
Recording pressure
Sunshine
A note is made of the number of hours of bright sunshine each day
Sunshine is traditionally measured using a Campbell-Stokes sunshine recorder
Cloud
The amount of the sky obscured by cloud
Different types of clouds
Sometimes even the speed and direction in which the clouds are moving are recorded using a nephoscope
Cloud Types - Cumulonimbus
Cloud Types - Cumulus
Cloud Types - Stratus
Cloud Types - Cirrus
Britain’s Weather
The Seasons
Temperature
In summer it gets warmer the further south you go
In winter it gets warmer the further west you go
In Britain temperature is affected by latitude and the sea
Temperature: Latitude
Temperature: Summer & Winter
In winter the northern hemisphere is tilted away from the sun so the sun’s rays are weaker
In summer the northern hemisphere is tilted towards the sun so the sun’s rays are stronger
Temperature: Summer & Winter
During the course of the year the Earth tilts towards and away from the sun
The mid-points of this cycle are called the equinoxes (spring and autumn)
Temperature: The Sea
The North Atlantic Drift is a warm ocean current originating in the Caribbean
It moves across the Atlantic keeping the west of Britain warmer than the east in winter
Winter in Canada & Britain
Rainfall
In Britain it rains the most in the west and in mountainous areas
Rain is brought across Britain from weather systems called depressions
In summer showers result from convection on warm days
How it rains
The surface is heated by the sun
Air rises
Air expands and cools
Air condenses
Water droplets grow to form raindrops
Air can rise in different ways
Relief rainfall
Cyclonic Rainfall
Depressions are areas of low pressure formed when cold and warm air meet
The warm air rises above the cold air to form a front
There are two types of fronts depending on the way in which the air masses are moving.
Cyclonic Rainfall: Fronts
Warm fronts form where warm air moves towards cold air
Cold fronts form where cold air moves towards warm air
As air rises at fronts both are responsible for rain
Convectional rainfall
Common on hot summer days inland
Hot air rises quickly and condenses to form cumulonimbus
Water freezes at the top of the cloud forming hail
Associated with lightning
Fair Weather
Fair weather is produced by high pressure
High pressure forms anticyclones
Air sinks and prevents the formation of rain clouds
Anticyclones cause heatwaves in summer and frosty/foggy mornings in winter
Forecasting the Weather
Modern forecasts use computers to simulate the likely weather based on careful observations from 100s of weather stations round the world
Satellite images and radar give a better picture of the weather over a wide area
A Satellite Image
A Radar Image
Cyclonic rainfall moving in from the west
The brighter the colour, the heavier the rainfall
Mountains intensify the rain such as over the Scottish Highlands
The Weather Map
Weather maps summarise the weather over a wide area using symbols
What symbols are used for: pressure, wind direction & strength, cloud cover and rainfall?
Weather
This Powerpoint presentation was produced specially for the Department of Geography & Geology at Northamptonshire Grammar School
May 2005
© M J Lewis