Transcript Lecture 1
Weather and the Environment When two Englishmen meet the first thing they talk about is the weather Dr Johnson David Leadley P567 Weather and Climate Weather / meteorology – study of atmosphere and atmospheric processes, daily variation Climate / climatology – seasonal average of weather at some location Climate change – long term variation in climate … and the environment Environment – conditions for life or growth Sustainability – ability of the environment to function indefinitely, despite stresses imposed by human society Non-sustainable Human behaviour • Using non-renewable resources as if supplies were unlimited eg. fossile fuels • Using renewable resources faster than they can be replenished eg. fresh water • Polluting the environment as if its capacity were unlimited eg. CFCs, CO2, acid rain • Increasing population, despite Earth’s finite ability to support us Earth from the Space Shuttle “For the first time in my life I saw the horizon as a curved line. It was accentuated by a thin seam of dark blue light – our atmosphere. I was terrified by its fragile appearance.” Ulf Merbold, astronaut Composition of the Atmosphere (1) Permanent Gases Percent Chemical composition (by volume of dry air) Nitrogen N2 78 Oxygen O2 21 Argon Ar 0.93 Neon Ne 0.002 Helium He 0.0005 Hydrogen H2 0.00005 Xenon Xe 0.000009 Gas Composition of the Atmosphere (2) Variable Gases Chemical composition Percent ppm (by volume of dry air) (parts per million) Water vapour H2O 0 to 4 ------- Carbon dioxide CO2 0.035 350 Methane CH4 0.00017 1.7 Nitrous oxide N2O 0.00003 0.3 O3 0.000004 0.04 Particulate matter ------- 0.000001 0.01 Chlorofluorocarbons (CFCs) ------- Substance Ozone 0.00000001 0.0001 Origin of the atmosphere a) Earth formed 4.6 billion years ago, without atmosphere b) Outgassing from volcanoes of N2, CO2, H2O, H2, Cl2, SO2, CH4 , but not oxygen c) Water condensed in oceans, H2 escaped, acid rain weathered rocks. CO2 at 100 times present level – larger greenhouse effect kept the atmosphere warmer and compensated for a 30% weaker Sun d) Emergence of life in oceans produced O2 and sequestered CO2 in rocks e) Once O2 was present O3 could be formed, giving UV protection and allowing life to expand its range Atmospheric Oxygen Albedo from various surfaces Surface Albedo (%) Surface Albedo (%) Snow 79-95 Dark Soil 5-15 Ice 30-40 Grassy Field 10-30 Thick Clouds 60-90 Forest 5-15 Thin Clouds 30-50 Water 10 (avg.) Wet Sand 20-30 Venus 78 Dry Sand 35-45 Mars 17 Concrete 17-27 Moon 7 Tarmac 5-10 Earth 30 Planetary temperature profiles Atmospheric profile of Venus At surface Ts=740 K ps=92 bar Atmospheres of Gas Giants Titan’s Atmosphere Nitrogen 90-97 % Hydrocarbons Methane 2-10 % Acetylene 2.2 ppm Ethylene 10.1 ppm Ethane 13 ppm Propane 0.7 ppm Nitriles Hydrogen cyanide 160 ppb Cyanoacetylene 1.5 ppb Summary of Lecture 1 • Introduction to Earth’s atmosphere – origin – composition – structure – comparison with other planets • Stefan’s law 4R T R S 1 2 4 s 2