The Restless Atmosphere Weather The Atmosphere • The atmosphere is a blanket of gases surrounding the earth. • It is made up of a mixture of different gases. The Earth’s Atmosphere The Earth’s Atmosphere Solar Energy – Energy from the Sun • The sun provides us with heat and light. • However, not all of the sun’s energy reaches our planet. – 50% of the sun’s energy reaches planet earth. – 25% is deflected back into space by dust and clouds in the atmosphere. – 25% is absorbed as it passes through the atmosphere. Latitude • Latitude means distance North or South of the equator. • It is measured in degrees. • In general, the further a place is away from the equator, the colder it will be. • There are 3 reasons for this. Latitude 1. We know the sun’s energy is absorbed as it passes through the atmosphere. Well, at the poles the atmosphere is thicker than at the equator. Therefore, less heat gets through to the polar regions. 2. At the equator the sun shines directly overhead. This means the heat is concentrated on a small area and so this area becomes hot. 3. At the poles the sun’s energy is slanted and it is spread over the curved surface of the earth. This means it has to heat up a larger area and so this area does not heat up as much. In summary, less heat gets through to the poles. It has to heat up a large area. Lots of heat gets through to the equator. It has to heat up a smaller area. How Latitude influences Temperature Wind • Wind is moving air. • Air moves from High pressure areas to Low Pressure areas. Winds and Air Pressure • Air moves from High Pressure areas to Low Pressure areas. • Some places on the earth have high pressure and some have low pressure. But why? • Warm air rises leaving areas of low pressure. • Cold air descends creating areas of high pressure. High Pressure and Low Pressure Winds and Air Pressure High and Low Pressure Areas • If we apply this principle to the earth we see that some places on the earth’s surface will have high pressure and other areas will have low pressure. • These areas of different pressure create wind. Global Wind Patterns Global Wind Patterns • We now know that winds travel from HP areas to LP areas. • This creates a regular pattern of the different winds on the earth. Global Winds and the Coriolis Effect • The earth is spinning on its axis. • Because of this the winds are deflected at an angle. • They are deflected to the right in the Northern hemisphere, and to the left in the southern hemisphere. • This is called the Coriolis Effect. Ocean Currents Air Masses • An air mass is a body of air with its own temperature, pressure, and humidity level. • Air masses can effect the weather of the countries they pass over. • Many different air masses meet over Ireland so our weather changes a lot. There are 4 different air masses which effect Ireland’s weather. • • • • 1. Polar Air Masses 2. Continental Air Masses 3. Tropical Air Masses 4. Maritime Air Masses Fronts • When two air masses meet they do not mix very well because of their different temperature, pressure and humidity. • Where the two air masses meet is called a Front. • We will look at two types of Fronts, a Cold Front and a Warm Front. Cold Fronts • • • • A Cold Front occurs when cold air moves in towards warm air. The cold air forces the light warm air to rise. As the warm air rises it cools and condensation occurs. Clouds are formed and this leads to heavy rainfall. Warm Fronts • • • • A Warm Front develops when warm air moves in towards cold air. The warm light air rises up over the cold air. As it rises it cools and condensation occurs. Clouds are formed and this leads to rainfall. Depressions • A Depression is an area of Low Atmospheric Pressure. • Depressions are also known as Cyclones. • Depression often pass over Ireland. • Depressions bring wet and windy weather. This is why we receive lots of rain. Anticyclones • An anticyclone is an area of high pressure. • Anticyclones bring clear sunny weather. • There are few clouds and a gentle breeze. The Water Cycle • • • Water is a Renewable Resource. When rain falls, the water is recycled and eventually goes back to the clouds to fall as rain again. This is called the water cycle. • There are 4 stages in the Water Cycle. 1. 2. 3. 4. Evaporation Condensation Precipitation Run-Off Clouds • Clouds are made when water vapour condenses into tiny droplets. • There are many different types of clouds. • The most common types of clouds are; 1. 2. 3. Cirrus Clouds Cumulus Clouds Stratus Clouds Rainfall • Precipitation means hail, rain, sleet or snow. • Rain is the most common type of precipitation. • Rain occurs when warm air is forced to rise. As the warm air rises it cools. Cold air cannot hold as much water vapour as warm air, so condensation occurs. Clouds are formed and rain occurs. • There are 3 different types of rain, because there are 3 different reasons why warm air is forced to rise. 1. 2. 3. Relief rainfall Frontal (cyclonic) rainfall Convectional rainfall Relief Rainfall • Relief rainfall occurs when; - Warm moist air moves in from the sea. - It hits a mountain range at the coast and is forced to rise. - It cools as it rises. - Condensation occurs, clouds form and it starts to rain. Frontal Rainfall • Frontal rainfall occurs when; – Warm and cold air masses meet at a Front – The warm air mass moves up over the cold air mass. – The warm air cools and condensation takes place. – Stratus clouds form and rain occurs. Convectional Rainfall • Convectional rain occurs when; – The sun shines on the land and heats up the air above it. – The heated air rises quickly. – As it rises it cools and condensation occurs. – Cumulus clouds are formed and heavy rain occurs. The Weather • When we talk about the weather we usually talk about the following things. 1. 2. 3. 4. 5. 6. 7. Temperature Precipitation (rain etc) Sunshine Wind speed Wind direction Atmospheric pressure Humidity All of these different aspects of the weather can be measured. There are different weather instruments to measure each thing. These instruments are usually in a weather station. Temperature • Temperature is measured using a Thermometer. • It is measured in degrees Celsius (°C). • Lines on a weather map showing areas of equal temperature are called Isotherms. Temperature • You need to know how to calculate the; 1. Mean Temperature 2. Temperature Range Mean Temperature: Add all the monthly temperatures, then divide by 12. Temperature Range: Take the lowest temperature away from the highest temperature. Mon Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Mean Monthly Temp 10 13 15 17 18 21 23 28 21 15 12 11 Precipitation • Precipitation is measured using a Rain Gauge. • It is measured in millimetres. • Lines on a map showing areas of equal precipitation are called Isohyets. Sunshine • Sunshine is measured using a Campbell Stokes sunshine recorder. • Sunshine is measured in Hours per day. • Lines on a weather map showing areas of equal sunshine are called Isohels. Wind • We can measure 3 things about the wind. • Wind Speed – Using an Anemometer. • Wind Direction – Using a Wind Vane. • Wind Strength – Using the Beaufort Scale The Beaufort Scale • The Beaufort Scale describes the effect the wind has on the landscape. • Wind strength is divided into 12 forces. • The Beaufort Scale was invented by an Irishman. Atmospheric Pressure • Atmospheric pressure is measured using a Barometer. • It is measured in millibars. • Lines on a weather map showing areas of equal pressure are called Isobars. A Barograph can also be used to measure atmospheric pressure Humidity • Humidity is measured using a Hygrometer. • A common type of hygrometer is a wet and dry bulb thermometer. • It is expressed as a %. 100% is the maximum. The Greenhouse Effect • The Greenhouse Effect occurs naturally. • When the sun shines it heats up the earth. • Some of the heat gets trapped in gases in the atmosphere. • It is a positive thing because without the Greenhouse effect the earth would be too cold for us to live on. Global Warming • Carbon dioxide and methane are Greenhouse gases in the atmosphere. • The amount of these gases has increased a lot in recent years. • Therefore, more of the sun’s heat is being trapped in the atmosphere. • This is making the earth warmer. This is called Global Warming. The Greenhouse Effect and Global Warming Causes of Global Warming • There are a number of reasons why Global Warming is taking place. 1. There is a big increase in the amount of Carbon dioxide in the atmosphere. 2. People are burning more fossil fuels, oil, coal, gas. 3. Tropical rainforests are being cut down. Trees absorb C02 and so less trees means more C02 in the atmosphere. 4. There are more CFC’s in the atmosphere. These are bad gases which trap lots of the sun’s heat. The Effects of Global Warming • Global warming will create many problems for people in the near future. These include; 1. 2. 3. The Polar ice caps will melt causing sea level to rise. Low lying countries or regions may be flooded. Some parts of the world will become drier. It will be more difficult for farmers to grow crops. This may lead to drought and desertification. 4. However, it may also bring some positive things. Some countries that are now cold may become warmer, allowing more crops to be grown. Solutions to Global Warming • If we want to stop the problem of global warming there are a number of things we need to do. These include; 1. 2. Stop using fossil fuels such as coal and oil. Use more renewable energy sources such as wind, wave and solar power. Reduce Deforestation - Plant more forests and stop cutting down the forests we have. Encourage energy conservation - Save energy at home by using less electric items and walk / cycle instead of using cars or buses. 3. 4. Revision Questions • • • • • • • • • • • • • Name 3 gases in the atmosphere. Why does all of the energy from the sun not reach planet earth? What does Latitude mean? How does Latitude influence the temperature of a place? What is wind and why does it occur? What is the Coriolis Effect? Name two Cold Ocean Currents and two Warm Ocean Currents. List 4 air masses that effect Ireland’s weather? What effect do each of these air masses have on Ireland’s weather? Explain with diagrams the difference between a Cold and a Warm Front. What is a Depression and what type of weather does it bring? What is an Anticyclone and what type of weather does it bring? Draw and label a diagram of The Water Cycle. Revision Questions • • • • • • • List 3 types of clouds. List 3 types of rainfall and use diagrams to show how they are different. List 7 things you can measure about the weather and draw the instrument used to measure each thing. What is the Greenhouse Effect and why is it happening? What is Global Warming and why is it happening? What effects is Global Warming having on our planet? What can we do to solve the problem of Global Warming?