Atmosphere - Part 2. High and Low Pressure Systems

Transcription

1 Atmosphere - Part 2 High and Low Pressure Systems

2 High Pressure vs. Low Pressure H regions : cool air sinks, increasing the air density, thus resulting in an area of high pressure L regions: warm air rises, decreasing air density, thus resulting in an area of low pressure

3 High Pressure vs. Low Pressure Air masses move both horizontally (parallel to the Earth s surface) and vertically Air masses always move from areas of high pressure to areas of low pressure

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5 Anticyclones Anticyclone: an area of atmospheric circulation surrounding a high-pressure centre. Northern hemisphere: spins clockwise Southern hemisphere: spins counter clockwise The direction of the anticyclone is determined by the Coriolis effect

6 Anticyclones more settled weather, clearer skies, and in summer, sunny warm days. Winter high pressure systems bring the same calm conditions but this often leads to frosts as there are few clouds to trap the heat at night

7 Depressions / Cyclones Depression /cyclone: an area of atmospheric circulation surrounding a low-pressure centre. a tropical storm characterised by violent winds revolving around an area of low pressure. Northern hemisphere: spins counter-clockwise Southern hemisphere: spins clockwise

8 Depressions Strong depressions that develop over warm waters in tropical oceans, have different names depending on regions: cyclones, hurricanes or typhoons. Violent storms (very strong winds and heavy rain) Floods, landslides, etc. Shatter windows and rip roofs off buildings etc.

9 Depressions / Cyclones Windy weather Cloudy conditions Periods of rain, and in winter, snow Unsettled, changeable weather

10 Anticyclone Depression/Cyclone Centre High Pressure Low Pressure Northern Hemisphere Air Spin Clockwise Counter-Clockwise Southern Hemisphere Air Spin Counter-Clockwise Clockwise Air Movement Going Down Going Up

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13 Is this happening in northern hemisphere or southern hemisphere? ANSWER: Northern because the anticyclone is turning clockwise. Fig. 12:

14 Atmosphere - Part 3 The Greenhouse Effect

15 The Greenhouse Effect The greenhouse effect is a natural process that allows the Earth to retain some of the heat it receives from the Sun

16 The Earth s Atmosphere How is it supposed to work? The presence of gases in the atmosphere like carbon dioxide (CO2), methane (CH4) and nitrogen oxides (N₂O) help to regulate the temperature of our planet when they are not in excess from human activity. The greenhouse effect is when the gases in our atmosphere help to trap some of the sun s rays (solar radiation) by reflecting the heat energy back towards the earth. We want this to happen! It is only bad when the greenhouse gases are in excess.

17 The Greenhouse Effect

18 Greenhouse Gases - What are They? Water Vapour (H₂0) Carbon dioxide (CO₂) Methane (CH₄) Nitrous Oxide (N₂O) These gases absorb and release infrared radiation from the sun.

19 The Greenhouse Effect

20 The Intensification of the Greenhouse Effect There is more and more carbon dioxide present in our atmosphere, than ever before.

21 Increases in Carbon Dioxide Burning of fossil fuels Clearing of farmland, deforestation and burning of forests

22 Increases in CH₄ & N₂O Thankfully, methane and nitrous oxides are not as abundant as carbon dioxide emissions Methane causes a greenhouse effect 21 times greater than carbon dioxide. Main source comes from farming cows release methane when they pass gas (fart)! Nitrous oxide comes primarily from applying nitrogen-rich fertilizer to farms crops

23 Greenhouse Gas CO 2 (carbon dioxide) Factors of Natural Origin Volcanic eruptions, forest fires and cellular respiration. Factors due to Human Activity Combustion of oils, natural gas and coal. Cutting trees for farmland or urban expansion. CH 4 (methane) Digestion in wild animals, decomposing plants, digestion in farm animals. Manure storage /management, rice farming, household waste, and natural gas. NO x (nitrous oxides) Bacteria in the soil and oceans. Applying nitrogen rich fertilizers and certain chemical processes.

24 Climate and Weather

25 What is the difference between climate and weather? The difference between weather and climate is a measure of time. Weather is what conditions of the atmosphere are over a short period of time Climate is how the atmosphere "behaves" over relatively long periods of time

26 Climate Change Climate change is the abnormal modification of climatic conditions on Earth, caused by human activity We see changes in patterns of precipitation, wind and other aspects of climate Areas which used to be cold, are warming up. Permafrost is melting, Glaciers are melting, Pack ice is melting, summers are warmer, etc. Not necessarily good or bad, just different.

27 Review 1.Do air particles exert more or less pressure as the temperature rises? Explain. 2.Explain the concept of convection. 3.A flight from LA to Sydney took 14 hours the return trip took 12 hours. Why? 4.Is the Greenhouse effect a recent phenomenon caused by us? Explain.