Unit 9. Atmosphere. Natural Science 1º ESO Antonio Jesús Moreno Quintero. Colegio Guadalete. Attendis.

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1 9. Atmosphere Unit 9. Atmosphere. 1

2 1. The Earth s atmosphere. Atmosphere: envelope of gases and particles which surrounds the Earth. Evolution of the atmosphere 1 st state: hydrogen and helium. It was lost because these gases are so light that the Earth gravity was not able to retain them, and took away to the outer space. 2 nd state: volcanic eruptions released gases such as carbon dioxide (CO 2 ), hydrochloric acid (HCl), Sulphur dioxide (SO 2 ), and nitrogen (N 2 ). When the Earth was cooling down, the water vapor was condensing and precipitating as torrential rains for centuries, forming the oceans, where living things appeared. 3 rd state: photosynthetic living things appeared and start to release oxygen toward the atmosphere. This oxygen reacted with all the other gases, changing them and the whole atmosphere to the actual composition. Composition: Nitrogen (N 2 ) 78% Oxygen (O 2 )21% Argon (Ar) 0 93% Carbon dioxide (0 04%) Other gases (0 03%): water vapor, ozone, etc. 2

3 Structure: Unit 9. Atmosphere. Troposphere: lowest layer of the atmosphere (0 to 12 Km). The thinnest and the densest, because contains about 80% of the atmosphere gases. Most of the meteorological phenomena take place in this layer, because it contains almost all the water vapor of the atmosphere. Stratosphere: lies between 12 and 50 Km. It contains about 19% of the air. The Ozone layer is in this layer, and shields against UV solar radiation. Mesosphere: from 50 to 80 km height. Although it is not very dense, it has enough particles to produce friction and destroy meteorites, protecting us and becoming into shooting stars. Thermosphere: form 80 to 600 km height. Absorbs gamma rays and X rays from the sun, protecting us against these powerful and harmful radiations. This absorption is linked to the phenomenon of auroras. Exosphere: the outermost layer, it extends for thousands of kilometers, with a very few particles in this layer. Artificial satellites orbit in this layer. 3

4 2. The Greenhouse Effect. The greenhouse effect is a natural effect that keeps the Earth warm. The sunrays arrive to the Earth and cross the atmosphere and arrive to the Earth s surface, heating it. The Earth s surface reflects these rays, and they would run away towards outer space if the greenhouse gases didn t catch them. The main greenhouse gases are: CO 2, Ch 4, H 2 O, and NO 2 These gases rebound the sunrays to the Earth surface again, and this effect makes the Earth to be warm during the day and during the night too. Without greenhouse effect the average temperature on the Earth would be -18ºC. Unequal warming of the planet. The temperature on the Erath varies with latitude, because on the Equator sunrays hit the Earth perpendicular, meanwhile towards the North and South Poles the sunrays hit the Earth more and more tilted. The reason of the seasons is how tilted are the sunrays hitting the Earth, not how far the Earth is from the Sun. 4

5 3. Atmosphere and life The physical and chemical characteristics of the atmosphere make our planet habitable. The processes that are involved in making the Earth habitable for life are: a) Protection against radiation: different layers of the atmosphere absorb x-rays, gamma rays and ultraviolet rays, shielding us. b) Natural greenhouse effect maintains average temperatures in values that let water to be in liquid state, making life possible. Air circulations compensate difference in irradiation from equator and poles. c) Source of nutrients: oxygen for respiration and carbon dioxide for photosynthesis. 4. Weather phenomena. Atmospheric phenomena due to water vapor precipitation Rain (lluvia) Rain occurs when the water droplets in a cloud join together. When they are big enough, gravity makes them fall. Drizzle (llovizna) Water droplets are smaller than 0 5 mm and seem to be floating in the air. Snow (nieve) It is a type of precipitation formed of tiny ice crystals which groups in snowflakes. It happens when temperatures inside the clouds are lower than 0 ºC. Sleet (aguanieve) Mixture of snow and rain because close to the Earth, air is warm and melts partially snowflakes. 5

6 Hail (granizo) Hail occurs when there are strong rising air currents inside the cloud which deep freeze the water droplets (-50 C). Atmospheric phenomena caused by the wind Hurricanes are violent tropical storms that form in Hurricane (huracán) the tropics over the ocean. They occupy great surfaces (can be bigger than 500 km in diameter) and last over a week. Whirlwinds or dust storms (torbellinos o tormentas de arena) They occur on sunny days in dry open spaces. The air rises in a spiral and collects sand and dust particles. They only last a few minutes and can reach 40 Km/h. Thunderstorm (tormenta eléctrica) They are characterized by thunder and lightning and they are usually accompanied by heavy rain and strong wind. Tornado (tornado) Tornadoes have an inverted cone shape. These winds can reach speeds of 500 km/h and demolish everything in their path. They last from seconds to over an hour. 6

7 5. Climate and temperature Climate: atmospheric phenomena in a specific region along a long period of time. Climate is determined by latitude and distance to the sea. It is characterized by temperature and amount of rainfall. Weather is the conditions of temperature, humidity, wind in a small region along a short period of time. Instruments for measuring atmospheric data: Thermometer (Termómetro) it measures air temperature at a given time, and the highest and lowest temperature daily. Barometer (Barómetro) it measures atmospheric pressure expressed in milibars. 7

8 Rain gauge or pluviometer (pluviómetro) it measures the amount of rain or snow, expressed in L/m 2 Hygrometer (Higrómetro) It measures humidity and express it in %. Weather vane it shows the direction of the wind expressed as the name of the compass point from which the wind blows, It measures strength of the wind expressed in Anemometer Km/h. 6. The atmosphere environmental problems. The Increase of the Greenhouse Effect The burning of fossil fuels releases a great amount of CO 2, which is one of the most important greenhouse gasses. It is stored in the atmosphere, producing an increase of the greenhouse effect in the whole planet, retaining more energy from the Sun, and producing Global Warming, 8

9 which will produce a rising in the sea level and other weather changes. Unit 9. Atmosphere. Ozone Layer Damage. CFCs are gases which destroy ozone in the stratosphere. It was used very much in the 20 th century in air conditioning, fridges, deodorants, and so on. In 1978 was forbidden, but gases released continuing destroying ozone layer and producing ozone holes. It could produce skin illnesses because more UV rays are reaching the Earth s surface in some regions. Acid rain Sulphur and nitrogen oxides released by factories react in clouds producing sulphuric and nitric acids, which fall in rain acidifying lakes and soils, damaging or killing living things. Pollution Suspended particles released by factories and vehicles are accumulated in cities and industrial areas producing respiratory diseases. 9