National 4 Geography @ Gairloch High School

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Lesson 1 - How do we gather and present data on weather & climate?

Lesson 2 - Why do local climates in Scotland vary?

Lesson 3 - How can a synoptic chart be used to interpret weather conditions?

Revision Task

Lesson 4 - What is a depression and what impact does it have?�Lesson 5 - What is an anticyclone and what impact does it have?

Lesson 6 - Why does the UK have such changeable weather?

Revision Task

Practice Questions

Guided Revision

Page 2

Date: Lesson 1 - How do we gather and present data about weather & climate?

What is the difference between weather and climate?

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Weather reflects short-term conditions of the atmosphere while climate is the �average daily weather for an extended period of time at a certain location.

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The UK has a dedicated national weather service called the Met Office. It works to �understand past, current and future weather and climate conditions so that it can�give advice to those that need reliable information about the weather.

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As we learn about the weather we’ll be studying the �science behind what we see on the weather forecast

and in the news. This is called meteorology.

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How is data about the weather gathered?

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The weather is made up of a number of different�elements.

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• Temperature is a measure of how much heat �energy the atmosphere has.. It is measured using a thermometer, either digitally or manually. It is usually reported in degrees celsius (^oC)
• Precipitation includes all forms of rain, hail, snow and sleet. This is collected in rain gauges and measured daily to record the amount of precipitation that has fallen. The amount of precipitation that has fallen is recorded in mm. The Met Office also use radar stations across the UK, which scan the sky for rain every 5 minutes and can measure where it is and how heavy it is.
• Cloud Cover refers to how much of the sky is covered by cloud. Traditionally, this was measured by eye and recorded in oktas. One okta is one eighth of the sky. A sky that was around half filled with clouds would be described as 4 oktas of cloud. As this relies on human interpretation is can be quite inaccurate! Lasers can be used to measure how much cloud there is and also how high the base of the clouds is.
• Wind Speed describes how quickly the wind is moving. This is measured using an anemometer and is reported in km/h or knots.
• Wind Direction is where the wind is coming from - not the direction it’s going in! It is reported using the compass directions - for example a westerly wind is coming from the west. It is measured using a wind vane, which aligns itself with the direction of the wind. The prevailing wind direction is the usual wind direction of a place.
• Air pressure refers to the weight of the air pressing down on the earth’s surface. It is measured by a barometer and is recorded in millibars. It is usually reported as high air pressure or low air pressure. Understanding air pressure can help to predict what may happen to the weather in the next hours or days.

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For the purpose of the National 4&5 Geography course, we will focus on these weather elements. Other elements include humidity, visibility, thunder and sunshine.

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How can we present information about the weather?

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Information about the weather is presented differently depending on the audience. For example:

• Weather reports given during news programmes present information using clear graphics. For example, they report the temperature using colours and will show rainfall on a map.

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Page 3

Lesson 1 - How do we gather and present data about weather & climate?

• The Maritime weather forecast is used by those who work or live at sea. It focuses on the wind speed and direction because it will have an impact on the wave height. Abbreviations are used for different parts of the UK and to summarise the weather conditions.
• Scientists communicate the weather using station symbols. This allows a lot of information to be included in one small symbol, so that an overall picture of weather conditions can be quickly worked out.

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What are station symbols and how can we interpret them?

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This is an example of a station symbol. Five weather elements are measured at a � weather station and reported on a map.

Temperature is reported in degrees celsius. The wind direction is shown by the� direction of the “tail”. It points to show the direction the wind is coming from. � The wind speed is shown with small ticks on the tail. A long line is equal to ten� knots and a smaller one is five knots. The total wind speed can be calculated by � adding these together. The cloud cover is shown inside the circle. The amount of� the circle which is filled in corresponds to the oktas of cloud cover. Finally, if� there is precipitation this is shown using a symbol at the base of the station� symbol.

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For example, in Lerwick the temperature is� currently 6 ^oC. The wind direction is coming� from the south-west. The wind speed is forty� knots. The cloud cover is four oktas. The � precipitation is rain showers. �

Things to remember:

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• If there is no precipitation, it’s important to say that “there is no precipitation.”
• The sky could be obscured by thick fog, meaning that the cloud cover above can’t be recorded.
• Read carefully to spot minus temperatures and make sure to record them accurately.
• Calm conditions (no wind) will have no wind direction.

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Page 4

Lesson 1 - How do we gather and present data about weather & climate?

Task 1

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What is weather? ……………………………………………………………………………………………………………

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What is climate? ………………………………………………………………………………………………………………

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Task 2

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1. Use the devices in the classroom to record the current weather conditions. Include the correct units.

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Air temperature: ………………… Wind speed: …………………

Precipitation: ………………… Wind direction: …………………

Cloud cover: ………………… Air pressure: …………………

• Draw a station symbol for the current weather conditions.

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Task 3

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Complete the table.

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Station symbol:

Page 5

Lesson 1 - How do we gather and present data about weather & climate?

Task 5

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Draw station symbols on the map to show the following:

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Task 6

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What is the weather in Ballycastle?

• Temperature ……………………………………………………
• Rainfall ……………………………………………………
• Cloud cover ……………………………………………………
• Wind direction ……………………………………………………
• Wind speed ……………………………………………………

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What is the weather in Lerwick?

• Temperature ……………………………………………………
• Rainfall ……………………………………………………
• Cloud cover ……………………………………………………
• Wind direction ……………………………………………………
• Wind speed ……………………………………………………

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Page 6

Date: Lesson 2 - Why do local climates vary in the UK?

What is the UK’s climate like?

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The UK’s climate varies depending on�location. A summary of this can be �seen on the map.

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• The west is wetter than the east
• The north is colder than the south

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There are also more local changes

• Places at high altitude (height �above sea level) are colder
• Places that are close to the sea�are warmer

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How does latitude affect climate?

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Latitude is the distance, in degrees, from�the equator. Gairloch is at latitude �57.728^oN.

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When energy from the sun arrives on earth�it spreads out on the earth’s surface. Due �to the curvature of the earth, it has to �spread out more at higher latitudes (e.g the �Poles) and the energy is less concentrated.

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Even though the UK covers just a few �degrees of latitude, the latitude can have an �effect. Places in the south of England have a�higher overall mean (average) temperature�than those in the north of Scotland.

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How does altitude affect climate?

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Altitude is the height of land above sea �level. Places which are at higher altitude �(e.g. mountains or villages and towns�in upland areas) have colder �temperatures than those at sea level.

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The temperature drops, on average, �1^oc for every 100m gained in altitude.

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Places at higher altitudes also have �higher wind speeds. This can reduce �the temperature and introduce wind �chill.

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Page 7

Lesson 2 - Why do local climates vary in the UK?

How does aspect affect climate?

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The aspect is the way a place, slope or building faces.�In the Northern Hemisphere, the sun rises in the �east and sets in the west. Throughout the day, it �moves through the sky to the south. This means �that places which face south get the warmth of the �sun throughout the day. Places that face north, or �are shaded by high buildings or mountains, may �never get the warmth of the sun and so are cooler.

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The aspect is used to build efficient and warm�houses. Maximising the windows on the south side�and minimising them on the north side will help�them to gain warmth from the sun, rather than �having to use heating. In Gairloch, the GALE

centre is an example of a building which has�been designed to maximise solar gains.

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How does distance from the sea affect climate?

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The oceans and seas heat up slowly in summer and�cool slowly in winter. This means they have a more�‘steady’ temperature than the land.

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Shieldaig and Achnasheen are both on the same�latitude and are only 30k m from each other. �Shieldaig, which is beside the sea, has a temperature �range of 10^oc. Achnasheen, which is inland, has a temperature range of 12^oc. This is because the sea acts as a thermal reservoir meaning that Shieldaig stays warmer in the winter.

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The North Atlantic Drift also changes the climate of places in the west compared to those in the east. It is an ocean current which brings warm water from the Gulf of Mexico towards the UK. It mainly influences the climate on the west, making it warmer (milder) in the winter. Without the North Atlantic Drift, Scotland’s temperature would be closer to northern Canada.

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Page 8

Lesson 2 - Why do local climates vary in the UK?

Task 1

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Use a map to find out the name of the cities (marked with circles) in each of these sections of the UK.

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Wetter & colder - ……………………………… Drier & colder - ………………………………

Wetter & warmer - ……………………………… Drier & warmer - ………………………………

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Task 2

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List the four factors which influence the UK’s climate.

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Task 3

Wick (latitude 58.4^oN) is further north than Dover (latitude 51.1^oN). Why does Wick have a colder climate than Dover? …………………………………………………………………………………………………………………………

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Task 4

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Think about your own house.

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1. Which room has a window which gets the sun early in the morning? This room will face east.
2. Which room has a window which gets a good view of the sunset? This room will face west.
3. Is your house built to maximise solar gains? Does it have:
1. Most of its windows facing south
2. Few windows facing north
3. The living room facing south (this is because it’s a room people spend a lot of time)
4. The kitchen facing north (this is because it is usually warmed by cooking and needs less heating)

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Task 6

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Which side of this mountain would be in the sun, and which would be in the shade?

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Page 9

Lesson 2 - Why do local climates vary in the UK?

Task 7

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Places close to the sea, like Shieldaig, are colder in the summer. This is because ……………………………………�………………………………………………………………………………………………………………………………… But in the winter, places close to the sea are warmer. This is because ………………………………………………�……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

Task 8

Use the data below to draw a graph of the average maximum temperatures in Hopedale and Stornoway.

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Page 10

Date: Lesson 3 - How can a synoptic chart be used to interpret weather conditions?

What is a synoptic chart?

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We learned in Lesson 1 that scientists use station symbols to present information about the weather as it’s recorded at stations around the UK. In order for forecasts to be made, that information is used to create synoptic charts. The word synoptic means a “summary of the whole” and they show the weather conditions over a large area.

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How can weather be interpreted using a synoptic chart?

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To interpret weather, we use five weather elements that we learned about in lesson 1.

• Temperature can be determined by referring to the fronts. Areas far from any fronts will have mild air. Areas behind warm fronts will have warm air. Areas behind cold fronts will have cold air.
• Wind speed can be determined by looking at the isobars. Wind is created when air moves from areas of high pressure to areas of low pressure. This means that in places where it changes quickly from high to low pressure there are high wind speeds. This can be seen in places where the isobars are close together. Where the isobars are far apart, the wind speeds are low.
• Cloud cover can be understood by studying the fronts. Fronts are places where two types of air meet (for example, a cold sector of air and a warm sector of air). At both warm and cold fronts, warm air is pushed upwards and condenses, creating clouds. Therefore, cloud cover is heaviest at fronts.
• Precipitation is caused when water droplets in clouds become too large and heavy and fall to the earth. This means that wherever there is heavy cloud, there is usually precipitation which follows. Precipitation can also occur in sectors of warm air where evaporation is happening over land or sea.
• Wind direction can be determined by examining areas of low or high pressure. In the northern hemisphere, air moves anticlockwise around areas of low pressure and clockwise around areas of high pressure.

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Isobars are lines of equal pressure.

Warm fronts show the front of a section of warm air.

Cold fronts show the front of a section of cold air.

High and low pressure are marked with H or L.

Page 11

Lesson 3 - How can a synoptic chart be used to interpret weather conditions?

What are fronts?

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Fronts mark the�front of a section

of warm or cold

air.

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When warm and �cold air meet, the�warm air always�rises. This creates�clouds and rain

as water vapour

condenses into

liquid water.

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Sectors of air move around the globe as the pressure�changes. In the UK, the sectors of air and fronts �usually move from west to east.

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A worked example of how to interpret weather �from a synoptic chart.

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In Lesson 1, you used the station symbols for �Ballycastle and Lerwick to describe the weather �conditions. With a synoptic chart you can now�explain the weather conditions.

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• Temperature: The weather in Ballycastle is 4^oC�warmer than Lerwick because it is in the warm�sector of air.
• Wind speed: The wind speed is 25 knots higher�in Ballycastle because the isobars are closer �together, which means air is rushing quickly �from high to low pressure.
• Cloud cover: Ballycastle has 7 oktas more cloud �cover than Lerwick. This is because it is under a �cold front, where warm air rising causes water �vapour to condense to form huge �cumulonimbus clouds. Lerwick is far from any fronts, so there is not much cloud.
• Precipitation: Ballycastle has heavy rain, which is caused by being �underneath a cold front. Here, condensing warm air rising causes water �droplets in the clouds to become heavy and fall as rain.
• Wind direction: the weather system shown is an area of low pressure. �This means that the air moves around it in an anticlockwise direction. This �has caused Ballycastle to have a wind direction from the north-west whilst �in Lerwick the wind is coming from the south-east.

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Whenever you are tackling a weather question using station symbols or a synoptic chart, make sure you refer to all five weather elements.

Page 12

Lesson 3 - How can a synoptic chart be used to interpret weather conditions?

The tasks on this page all refer to the synoptic chart.

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Task 1

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What is the weather in Cape Wrath?�

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What is the weather in Banbury?�………………………………………………………………

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Task 2

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Using the synoptic chart:

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1. Shade the area of warm air red
2. Shade the area of cold air blue
3. Draw heavy clouds where they occur
4. Draw light clouds where they occur
5. Is this an area of high or low pressure? ………………………
6. Draw arrows between the isobars to show the wind direction.
7. Draw a star in an area where the wind speed will be high.
8. Draw a square in an area where the wind speed will be low.

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Task 3

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Why is Cape Wrath windier than Banbury? ………………………………………………………………………………

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Why is Banbury warmer than Cape Wrath? ………………………………………………………………………………

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Why is it snowing in Cape Wrath but there is no rain or snow in Banbury? ……………………………………………

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How can weather be interpreted using a synoptic chart?

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To interpret weather, we use five weather elements that we learned about in lesson 1.

• Temperature can be determined by referring to the fronts. Areas far from any fronts will have mild air. Areas behind warm fronts will have warm air. Areas behind cold fronts will have cold air.
• Wind speed can be determined by looking at the isobars. Wind is created when air moves from areas of high pressure to areas of low pressure. This means that in places where it changes quickly from high to low pressure there are high wind speeds. This can be seen in places where the isobars are close together. Where the isobars are far apart, the wind speeds are low.
• Cloud cover can be understood by studying the fronts. Fronts are places where two types of air meet (for example, a cold sector of air and a warm sector of air). At both warm and cold fronts, warm air is pushed upwards and condenses, creating clouds. Therefore, cloud cover is heaviest at fronts.
• Precipitation is caused when water droplets in clouds become too large and heavy and fall to the earth. This means that wherever there is heavy cloud, there is usually precipitation which follows. Precipitation can also occur in sectors of warm air where evaporation is happening over land or sea.
• Wind direction can be determined by examining areas of low or high pressure. In the northern hemisphere, air moves anticlockwise around areas of low pressure and clockwise around areas of high pressure.

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Page 13

Lesson 3 - How can a synoptic chart be used to interpret weather conditions?

Task 4 - Practice Question

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Why is the weather different in �Belfast and in Stockholm?�

For this answer you should say:

• What the weather is
• Why it is different�

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Page 14

Revision Tasks

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Task 1

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What is the difference between weather and climate? …………………………………………………………………

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What is the scientific study of weather called? …………………………………………………………………………

Task 2

Match the weather element, how it’s measured and the units.

Temperature Rain Gauge & Radar Oktas

Cloud Cover Wind Vane Millimeters

Precipitation Anemometer Millibars

Wind Direction Thermometer Degrees Celsius

Air Pressure Barometer Knots

Wind Speed Eye & Lasers Compass Directions

Task 3 - Practice Question

Draw a weather station circle to �show the weather conditions described.

[National 5 2019 - 4 marks]

Task 4

Describe the differences in the weather between Glasgow, Manchester�and London. ………………………………………………………………………

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Page 15

Task 5

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Use the synoptic chart to answer�these questions.

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1. What does a warm front look �like?

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• What does a cold front look �like?��
• What is an isobar? �…………………………………

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• Explain why the weather in Belfast is cold. ………………………………………………………………………

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• Is this a low or high pressure weather system? How do you know?

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• What will the precipitation and cloud cover be in London? Explain how you know this.

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• “The wind direction in Belfast will be north-easterly”. Is this statement true or false? Explain your answer. ………………………………………………………………………………………………………………

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Page 16

Date: Lesson 4 - What is a depression and what impact does it have?

As we have learned about the weather so far we’ve looked at how it’s measured, recorded and reported. In this lesson and the next, we will focus on forecasting the weather, which means to predict how the weather will change over time.

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What is a weather depression?

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A weather depression is an area of low pressure which moves over time. It brings wet, windy weather and when it’s severe, is called a storm.

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How can I identify a weather depression on a synoptic chart?

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All of the synoptic charts you have looked at so far feature depressions. �You can spot a depression by identifying:

• An area of low pressure
• Isobars that are close together
• A warm front and a cold front which meet in the area of low pressure

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How do weather depressions move?

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Weather depressions move over areas. As they do, they bring different weather conditions. In the UK, most of our weather depressions move in from the south-west as they originate in the Atlantic Ocean. As they travel east over cities in the UK, they will cause the weather to change.

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Although at 6am it may have seemed a clever idea to plan a �BBQ for the evening, with weather forecasting we can make �sensible decisions. The temperature will have dropped, it will be �raining heavily and the BBQ sounds like a miserable idea!

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At 6am, Bristol is in an area of mild air. There are few clouds and the wind is coming from the south-west.

By midday, the depression has now moved. Bristol is in the warm sector of air and the wind is coming from the west. There are drizzly rain showers.

At 6pm, the depression has moved east again. Bristol is underneath the cold front, so it has heavy rain and lots of cloud cover. The temperature has also dropped and it is now colder.

Page 17

Lesson 4 - What is a depression and what impact does it have?

A worked example of a depressions question

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By putting together your understanding�of weather elements, synoptic charts and�depressions you can now forecast the�weather and make predictions about how�it will change in the future.

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Explain the changes which will take �place in the weather in Glasgow over the �next 24 hours.

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Due to the approach of the warm � front, cloud cover will increase with � nimbostratus clouds and steady rain. � The wind speed will be stronger as � the isobars are closer together. � Glasgow will then be in the warm � sector of a depression, so � temperatures will rise. Due to the � cold front arriving and bringing huge � cumulonimbus clouds, there will be � heavy rainfall. Temperatures will � drop as the cold front passes over. � The wind direction will become � more westerly. As the cold front � begins to move away and air pressure � rises, the sky will become clear and � rain will stop.

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You can also be asked about the impact�of a depression on an activity.

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The Glasgow and Clyde Children’s 5km cross-country run is due to take place at 9am on 15th April 2021. Should it go ahead or be postponed? Give reasons for your answer.

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• Consider the specific activity as it may not be impacted by every weather element. For example, the 5km run is likely to need to consider the temperature, rainfall and wind speed. The cloud cover is irrelevant, as a run could take place safely with clear or cloudy skies.
• Suggest reasons why the event would be affected. Rather �than simply stating “The cold front will move overhead, �lowering the temperature” you need to explain why this is �a problem. “Runners could become cold quickly and get �hypothermia. This is especially the case for children who �will lose heat quickly.”
• Give more than one impact for each weather element. For �example, “rain could make paths become slippery and �unsafe. It will also mean that organisers supervising the �event will be miserable and less likely to volunteer for future events!”

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Synoptic Chart, 1400 hours, 14 April 2021

Page 18

Lesson 4 - What is a depression and what impact does it have?

Task 1

Which of the five weather elements are important to consider for the following events or activities? Explain your answers.

1. A kayaking session around the coast - Temperature Cloud cover Wind speed

Wind direction Precipitation

• A fireworks display Temperature Cloud cover Wind speed

Wind direction Precipitation

• A sailing race Temperature Cloud cover Wind speed

Wind direction Precipitation

• An outdoor wedding with a marquee Temperature Cloud cover Wind speed

Wind direction Precipitation

• A holiday in a caravan to the seaside Temperature Cloud cover Wind speed

Wind direction Precipitation

• A long car journey Temperature Cloud cover Wind speed

Wind direction Precipitation

Task 2

Complete the paragraph choosing the correct word.

�A depression is a high or low pressure weather system.

It brings wet and windy calm and dry weather.

It can be identified on a synoptic chart by looking for a warm isobar front and a cold isobar front.

The isobars will be close together and the numbers showing air pressure temperature will be low (e.g. 960mb).

Depressions which arrive in the UK usually come from the north south east west.

They come from the Atlantic Ocean Pacific Ocean Indian Ocean.

This means that they bring a lot of rain sun snow.

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Page 19

Lesson 4 - What is a depression and what impact does it have?

Task 3 - Practice Question

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�Why is there going to be:

• Heavy showers starting?

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• Winds getting lighter?

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• Temperatures dropping?

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Task 4

The city of Dublin has planned an Easter parade. The weather forecast is shown on the synoptic chart. Do you think they should have the parade, or should �they cancel it? Give a reason for your answer.

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Page 20

Date: Lesson 5 - What is an anticyclone and what impact does it have?

What is an anticyclone?

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A anticyclone is an area of high pressure. It brings stable, unchangeable weather with low winds, cloudless skies and no rainfall.

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How can I identify an anticyclone on a synoptic chart?

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Anticyclones can be spotted by identifying:

• An area of high pressure
• Isobars that are far apart
• No fronts

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Anticyclones have a number of effects:

• Air is sinking due to high pressure. Usually, �it’s air rising that produces clouds and �precipitation. Therefore, in an anticyclone �there are clear skies and it is dry.
• There are low wind speeds, because the�isobars are far apart and air is not rushing �from high to low pressure.
• In the northern hemisphere, wind moves �clockwise around an area of high pressure.

Other effects depend on the time of year:

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Winter anticyclone - anticyclones that occur during winter create very low temperatures, frost and will sometimes bring fog. The clear skies allow heat radiating from the earth to escape into the upper atmosphere, which lowers the temperature at the surface. Frost can form on the ground due to the low temperatures. In the early morning, there may be fog. This is because moisture in the air is held close to the surface by the sinking air, rather than being able to move up and spread out in the atmosphere or distributed by winds.

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Summer anticyclone - anticyclones that occur during the summer create very high temperatures and can generate thunderstorms. As there are clear skies, there are no clouds to give shade to the surface of the earth and they are exposed to the sun’s energy throughout the day. This increases the temperature. Evaporation occurs at the surface but, due to the high pressure and sinking air, it cannot move up and spread out in the atmosphere. This can cause intense thunderstorms to occur in �the early �evening.

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Winter anticyclone

Summer anticyclone

Page 21

Lesson 5 - What is an anticyclone and what impact does it have?

Anticyclones at any time of year can cause problems associated with high pressure.

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• There is a greater risk of wildfire due to the lack of rainfall. Wildfires can be caused naturally and by the misuse of campfires and lighters.
• The high pressure keeps air pollution at a low level. This can build up in cities and cause health problems for those with breathing difficulties (e.g. Asthma)
• Reservoir and river levels drop. This can impact the ability to produce hydroelectric power.

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What are the consequences of an anticyclone in summer?

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Anticyclones in the summer bring long periods of hot and dry weather. These can have a number of consequences on people, the economy and the environment.

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• The elderly and very young can suffer from heatstroke, resulting in increased demand on medical services
• The risk of sunburn increases, which contributes to a longer term risk of skin cancer.
• Water restrictions are put in place. These limit the availability to homes and businesses. In some places, hosepipe bans are introduced which prevent people from using water to wash cars and water gardens.
• Rail services can be disrupted as the metal tracks become at risk of buckling.
• Crops suffer drought, which costs farmers millions in lost income.
• Heavy rain during thunderstorms lands on dry ground. This means that it will run over the surface and could cause flooding.

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What are the consequences of an anticyclone in winter?

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• Travel by road, particularly in the morning, can become dangerous if roads are icy. Journey times will increase due to a need to drive slower and the presence of collisions on the road.
• Fog reduces visibility. This can cause delays to air travel as planes cannot take off or land.
• A risk of ice causes councils to spend more on gritting services. They have to employ people to grit pavements and roads and also buy enough gritting salt.

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A worked example of an anticyclones question

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Give reasons for the weather conditions at Bathgate �on 28th December 2014.

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The synoptic chart shows that Bathgate is experiencing�a winter anticyclone. The temperature is -2^oC because�there is a lack of cloud and it’s during the winter, which �allows heat to escape and lowers the temperature. The�wind speed is low (5 knots) which is because the isobars�are spaced far apart. The wind direction is westerly�because winds blow clockwise around an area of high�pressure. There is only 1 okta of cloud cover because �the sinking air means that clouds cannot form. This also �means that the weather is dry - there is no precipitation�because there are no fronts nearby.

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Always check the date of a synoptic chart to correctly�identify an anticyclone in winter or summer.

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Page 22

Date: Lesson 5 - What is an anticyclone and what impact does it have?

Task 1

Circle or underline the correct words.

Liverpool is experiencing high low pressure.

This weather system is called a depression anticyclone.

The isobars are far apart close together.

The skies will be cloudy clear.

Cagliari is experiencing high low pressure.

This weather system is called a depression anticyclone.

The isobars are far apart close together.

The skies will be cloudy clear.

Task 2

Complete the table to describe the weather conditions in a summer and winter anticyclone.

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Task 3

1. Why is there fog during a winter anticyclone?……………………………………………………………………

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• Why do thunderstorms form when there’s an anticyclone in the summer? …………………………………

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Page 23

Date: Lesson 5 - What is an anticyclone and what impact does it have?

Task 4

Look at the synoptic chart on page 22 and the weather station symbols for �Liverpool and Cagliari.

Describe (say what the weather is like) and explain (say why it is like that) the weather in Liverpool and Cagliari. …………………………………………………………………………………………………………………………

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Task 5

Referring to the consequences of anticyclones in either summer or winter, write down:

1. What is one way that a winter anticyclone can cause problems for people?

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• What is one way that a summer anticyclone can cause problems for the environment?

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• What is one way that a winter anticyclone can cause problems for the economy? …………………………………………………………………………………………………………………………

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Page 24

Date: Lesson 6 - Why does the UK have such changeable weather?

Why does the UK have such changeable weather?

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People in the UK are always talking about the weather. That’s because our weather is really changeable. We can go from having dry and calm high pressure one day to a series of low pressure storms the next day. That’s partly to do with air masses.

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What is an air mass?

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An air mass is a large volume of air which travels from one place to another. The weather that an air mass brings depends on where it originates from. For example, if an air mass comes from the poles, it will be cold.

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What are the five UK air masses?

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The UK is the meeting point for five major air masses. Throughout the year, they compete with each other to dominate the UK’s weather. It is this competition that results in our weather changing from one air mass to another regularly.

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In other parts of the world, air masses are much more predictable. In India, a warm and dry air mass dominates for long periods bring a dry season. Then, a warm and wet air mass moves in and brings a wet season. In the UK we can have every season in one day!

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Air masses are given names depending on where they come from:

• Tropical air masses originate from the south. They bring warm air.
• Polar air masses originate from the east and west. They bring cold air.
• Arctic air masses originate from the north. They bring very cold air.
• Continental air masses originate over land. This means they are dry.
• Maritime air masses originate over water. This means they are wet.

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Air masses are different to depressions and anticyclones. They don’t depend on air pressure and can actually be composed of high or low pressure air. We can, though, sometimes recognise the presence of air masses on synoptic charts - for example if a cold front has moved in from the north it probably brings an Arctic Maritime mass with it.

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Page 25

Lesson 6 - Why does the UK have such changeable weather?

Tropical Maritime (mT)

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This air mass originates over the Atlantic Ocean so is saturated with water which has evaporated from the sea. This brings wet weather.

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It travels to the UK from the south which has warmer climates. This means it also tends to bring relatively warm weather. Once rain has fallen on the west, this air mass can bring drier weather to places on the east coast.

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Tropical Continental (cT)

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This air mass originates over the European Continent so is very dry as there is no water to be evaporated. This brings dry weather and can cause droughts.

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It travels to the UK from the south which has warmer climates. This means it also tends to bring relatively warm weather.

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Polar Maritime (mP)

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This air mass originates over the north Atlantic Ocean so is saturated with water which has evaporated from the sea. This brings wet weather.

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It travels to the UK from the north which has colder climates. This means it also tends to bring relatively cold weather. The weather when a Polar Maritime air mass is overhead is changeable, with heavy rain and sunny intervals particularly common in the north and west.

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Polar Continental (cP)

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This air mass originates over Scandinavia and Northern Russia and is quite dry, although this depends on the time it spends over the North Sea.

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In winter, it brings relatively cold weather. It is responsible for some of the UK’s lowest recorded temperatures. It can bring snow to the east, but there is rarely enough moisture left in the air by the time it reaches the west.

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Arctic Maritime (mA)

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This air mass originates over the Arctic and is dry as the cold seas have less evaporation.

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It brings very cold weather, especially to the north. If it’s spent longer at sea it �can also bring widespread snow.

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Identifying an air masses exam question

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When working on practice questions for a National 5 exam, you need to be �aware of when to talk about air masses and when not to!

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If the question gives a prompt (e.g. a picture) of air masses or mentions air �masses in the question, then you should refer to them. If a question has a �synoptic chart, you should not refer to them.

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Page 26

Lesson 6 - Why does the UK have such changeable weather?

Task 1

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Complete the table to show the major characteristics of the UK’s air masses.

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Task 2

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Watch the Met Office clip on Air Masses.

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1. Other than being hot and dry, what other impacts can a tropical continental air mass from the Sahara bring to the UK? ………………………………………………………………………………………………………
2. The polar continental air mass can come from two directions. What are these? ……………………………

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• As polar maritime air moves across the Atlantic Ocean it is heated by the sea below. This causes air to rise and condense. What does this create? ………………………………………………………………………
• What is the most common air mass to be present over the UK? ………………………………………………
• Which type of air mass, continental or maritime, changes the most as it moves? …………………………
• What is the cause of some of the UK’s most severe weather? …………………………………………………

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Task 3 - For each picture, identify the air mass represented.

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Page 27

Lesson 6 - Why does the UK have such changeable weather?

Task 4

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For each of these situations, explain which air mass is likely to have been responsible.

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1. McColls sells out of all ice cream. …………………………………………………………………………………

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• The council needs to buy more grit for the roads around Gairloch. …………………………………………

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• The CalMac workers, wrapped in many coats, have to clear the flooded deck of the Loch Seaforth.

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• London suffers its worst flooding in years as the Thames barrier has to be closed. ………………………

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• Aberdeen city schools are closed due to snow. …………………………………………………………………

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Task 5 - Practice Question�

What are four problems there could be if a tropical continental air mass was over the UK for a long period of time? ……………………………………………………………………………………………………………………………

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Page 28

Revision Tasks

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Task 1

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1. Draw a station symbol for weather Set X and Set Y.

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• Which set of weather information, X or Y, is correct for Bristol? �Explain your answer. ……………………………………………………

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Task 2

The synoptic chart shows the weather conditions in �Europe on July 8th 2020. Mr McCormack is taking his�young family to Blackpool for a one week holiday.

Do you think this is a good idea? Explain why you think �this. ……………………………………………………………�…………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

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Guided Revision

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Guided Revision

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Guided Revision