NAS 125: Meteorology

1. NAS 125: Meteorology The Atmosphere

2. North African dust, part 1 • For years, scientists had suspected that much of the red iron- and clay-rich soils on islands throughout the Caribbean and in Bermuda originated in North Africa, but were blown West by the Northeast trade winds. • They also suspected that dust from North Africa fertilized the tropical rain forests of the Amazon basin. • The transatlantic transport of African dust was confirmed by satellite data. The Atmosphere

3. The Atmosphere

4. North African dust, part 2 • North African dust lowers North American air quality, primarily over the southeastern United States. • It may contribute to development of red tides in the Gulf of Mexico, and may threaten coral reefs in the Caribbean. • Winds whipped up by winter disturbances over North Africa pick up dust from the soil surface and transport it as high as 3,000 m. The Atmosphere

5. North African dust, part 3 • The Northeast trade winds pick up the finer particles and transport them across the Atlantic to the Caribbean, Central America, and the southeastern U.S. • Florida receives more than half of the North African dust transported to the United States. • The transatlantic crossing takes one to two weeks, with most of the transport occurring from June to October – with a peak in July. • African droughts may increase dust transport. The Atmosphere

6. North African dust, part 4 • North African dust is part of the reason for reddish haze and colorful sunsets over the Southeast. • It may shelter pathogens and transport them across the Atlantic. • Even without pathogens, dust may trigger allergic and respiratory reactions. • North African dust may supply nutrients to the Gulf of Mexico, which has the unfortunate effect of making algae blooms and red tides more likely. • Algae and phytoplankton growth may harm Caribbean corals. The Atmosphere

7. Environmental spheres • Earth’s surface is a complex interface where four spheres meet, overlap, and interact. These spheres provide important organizing concepts for the systematic study of Earth’s environments: • Lithosphere (the solid, inorganic portion) • Hydrosphere (water in all its forms) Biosphere (life and the places where it can exist) • Biosphere (life and the places where it can exist) • Atmosphere (the gaseous envelope that surrounds Earth) The Atmosphere

8. Importance of weather • Weather affects virtually all aspects of our lives, from recreation to economic activities: • Effects on energy and food prices affect all aspects of the economy. • Adverse weather can kill or lead to increased incidence of disease. • Weather can disrupt transportation networks. • Weather can affect recreational activities. • Weather is variable. The Atmosphere

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11. The Atmosphere • The Earth is unique because of the composition of its atmosphere, which makes life possible. • It supplies the oxygen that all but a handful of organisms need to survive. • It supplies the carbon dioxide that photosynthetic plants and animals use to make the carbon-based compounds required for living things. • It maintains the water supply for life. • It moderates the climate against temperature extremes. • It protects Earth from the Sun’s ultraviolet radiation. The Atmosphere

12. Extent of atmosphere, part 1 • The atmosphere extends outward to 10,000 kilometers. • Most of its mass is concentrated at low elevations. • More than half of the atmosphere’s mass is concentrated in the lowest 5,500 m. • More than 99 percent of the atmosphere’s mass is concentrated below 32 km. • Atmosphere fills empty spaces in rocks and soil, such as caves and crevices. The Atmosphere

13. Extent of atmosphere, part 2 • Gases are dissolved in the waters of the Earth as well as in the bodily and cellular fluids of living organisms. The Atmosphere

14. Weather • Weather is the instantaneous state of the atmosphere at a given place and time. • Weather may be described in terms of variables such as temperature, humidity, cloudiness, precipitation, and wind speed and direction. • Weather varies continuously from place to place and time to time. • “If you don’t like the weather, wait a minute.” • Meteorology is the study of the atmosphere and the processes that cause weather. The Atmosphere

15. Climate, part 1 • Climate refers to the pattern or average of weather conditions over a long period, encompassing mean characteristics, variability, and extremes. • By international convention, climate variables are averaged over a 30-year period beginning with the first year of a decade (e.g., 1971-2000). The averaging period is shifted forward 10 years with the beginning of a new decade. • These 30-year averages (normals) of monthly temperature and precipitation variables are used to describe climate. • Seasonal variables, length of growing season, percent of possible sunshine, and number of days with dense fog among other important variables. The Atmosphere

16. Climate, part 2 • Climate is probably the most important environmental control, affecting agriculture, water supply, heating and cooling requirements for buildings, weathering and erosion processes, and much, much more. • Climatology is the study of climate, its controls, and its spatial and temporal variability. The Atmosphere

17. Evolution of the atmosphere • The origins of the atmosphere began with the Earth’s genesis about 4.6 billion years ago. • Evidence for the evolution of the atmosphere can be found in meteorites, rocks, and fossils. • Primeval phase • The primeval phase covers the origins of the Earth, its atmosphere, and the early development of the atmosphere. The Atmosphere

18. Nebular hypothesis, part 1 • About 5 or 6 billion years ago, the solar nebula, a disc-shaped interstellar cloud – mainly consisting of hydrogen, helium, oxygen, nitrogen, silicon, calcium, aluminum, sodium, potassium, magnesium, carbon, sulfur, iron and some heavy metals – rotated through our region of the Milky Way. The Atmosphere

19. Nebular hypothesis, part 2 • Gravity forced more matter to concentrate near the center of the disc, as it did so, pressure and temperature inside the proto-sun would increase until self-sustaining fusion reactions started. • The spin of the solar nebula induced eddies in the gas and dust. • Planetismal bodies formed from matter concentrating in the center of the eddies. The Atmosphere

20. Nebular hypothesis, part 3 • Moons formed around the protoplanets in secondary eddies. • Protoplanets gained additional moons by capturing asteroids. • The 9 or 10 protoplanets grew larger by sweeping up more material from the cloud of gas and dust. The Atmosphere

21. Nebular hypothesis, part 4 • Initially, the composition of the protoplanets was similar, although heavier elements were more abundant among the inner planets than the outer ones. • Heavier elements concentrated near the protoplanets’ cores. The Atmosphere

22. Nebular hypothesis, part 5 • The four inner planets (Mercury, Venus, Earth and Mars) lost more of their light elements (hydrogen and helium) than the larger, cooler gaseous planets that were farther from the Sun. • Solar wind swept the inner part of the solar system of lighter material. The Atmosphere

23. Earth ‘garden’ • Earth would gain much of its elements compounds from the gas cloud it condensed from. • More would come in from the rain of comets and asteroids in the Earth’s early history – this rain of organic compounds may have planted the seed for the development of life as well as the atmosphere. The Atmosphere

24. Early Earth, part 1 • The early Earth would have been hot as a result of gravitational compaction, radioactivity and asteroid impacts. • The core and mantle formed by about 4.5 billion years ago. • A thin primeval atmosphere would have been established by about 4.4 billion years ago. • The early atmosphere was probably composed of molecular hydrogen (H2), helium (He), methane (CH4), and ammonia (NH3). The Atmosphere

25. The Atmosphere

26. Early Earth, part 2 • Heat in the inner Earth drives volcanic and tectonic processes; volcanic outgassing was probably the primary source of atmospheric gases. • About 85 percent of outgassing took place within the first million years of the Earth’s existence. • Outgassing produced an atmosphere that was primarily carbon dioxide (CO2), nitrogen (N2), and water vapor (H2O), with trace amounts of methane, ammonia, sulfur dioxide (SO2), and hydrochloric acid (HCl). The Atmosphere

27. Early Earth, part 3 • Radioactive decay of potassium-40 added argon (Ar), an inert gas, to the atmosphere. • Dissociation of water vapor by ultraviolet radiation added free oxygen (O2) to the atmosphere. • Much of the molecular hydrogen, a light gas, escaped to space because the Earth’s gravity was not strong enough to retain it in the atmosphere. • Some of the oxygen combined with other elements. The Atmosphere

28. Early Earth, part 4 • Some scientists believe that, between 4.5 and 2.5 billion years ago, the Sun was 30 percent fainter than it is today, but the CO2-rich atmosphere was both 10 to 20 times denser than it is today, and it was a potent greenhouse environment. • Surface temperatures ranged as high as 85 C and 110 C. The Atmosphere

29. Early Earth, part 5 • By about 4 billion years ago, the Earth cooled enough to allow a stable crust to form and chemical compounds such as water to remain stable. • Atmospheric water vapor condensed to form clouds, and torrential rains filled the ocean basins such that the oceans covered 95 percent of the planet. • Carbon dioxide gas dissolved into the surface waters, forming carbonic acid, an important agent for the chemical weathering of rock at or near the surface of the Earth. The Atmosphere

30. Early Earth, part 6 • Early life transformed the atmosphere. • By about 2.5 billion years ago, cyanobacteria (blue-green algae) filled the primitive oceans. They manufactured their own organic nutrients from carbon dioxide and water in a chemical reaction, photosynthesis, powered by the energy of sunlight. • Oxygen (O2) is a by-product of photosynthesis. • As life became more abundant, the atmosphere became depleted in carbon dioxide and enriched in oxygen. The Atmosphere

31. Early Earth, part 7 • Early life (continued): • Little change in atmospheric oxygen occurred for about 500 million years, however, as the oxygen first combined with minerals in ocean sediments. • As the surface sediments became saturated with respect to their ability to bind oxygen, oxygen concentrations in the atmosphere began to rise. • Nitrogen, a product of outgassing, became the most abundant atmospheric gas. • As oxygen levels rose, an ozone (O3) layer formed that protected life from the Sun’s ultraviolet radiation. The Atmosphere

32. Early Earth, part 8 • Carbon dioxide levels have fluctuated considerably, leading to extended periods of greenhouse warming as well as extended ice ages. • Carbon dioxide vented by outgassing during period of extended volcanic activity 120 to 100 million years ago led to extended warm period, with temperatures as much as 10 C warmer than today. • During Pleistocence ice ages (1.7 million years ago to 10,500 years ago) carbon dioxide levels decreased as glaciers advanced and increased as glaciers retreated. The Atmosphere

33. Modern atmosphere, part 1 • The principal gases of atmosphere have a uniform vertical distribution in the lowest 80 km. This portion of the atmosphere is called the homosphere. • Above 80 km, the composition of the atmosphere is stratified such that the concentration of heavier gases decreases more rapidly than that of the lighter gases. This portion is called the heterosphere. The Atmosphere

34. Gases of the Atmosphere • Basic composition of the atmosphere: • Nitrogen – 78% • Oxygen – 21% • Argon – nearly 1% • Neon, helium, methane, krypton, hydrogen, water vapor, carbon dioxide, ozone, carbon monoxide, sulfur dioxide, nitrogen oxides, and various hydrocarbons – trace amounts The Atmosphere

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36. Other planets • Earth’s nitrogen/oxygen dominated atmosphere is strikingly different from the carbon dioxide-rich atmosphere of Venus and Mars. • The Venutian atmosphere is 100 times more dense than that of Earth, with a surface temperature of about 460 C. • The Martian atmosphere is much thinner than Earth, with surface temperatures ranging from about -60 C at the equator to less than –120 C at the poles. The Atmosphere

37. Role of H2O, CO2, and ozone • While occuring in trace amounts, water vapor (H2O), carbon dioxide (CO2), and ozone (O3) are essential for life. • Water vapor determines the humidity of the atmosphere, is the source of all clouds and precipitation, and is intimately involved in the storage, movement, and release of heat energy. • Water vapor and atmospheric CO2 significantly affect the climate because they can absorb infrared radiation, keeping the lower atmosphere warm enough for life. • Ozone shields life from harmful effects of ultraviolet light. The Atmosphere

38. Aerosols, part 1 • Aerosols are minute liquid and solid particles found in the atmosphere. • They are typically invisible, but larger aggregates, such as water or ice droplets in clouds, can be seen. • Most are found at lower levels in the atmosphere. • They come from both natural and human-made sources. The Atmosphere

39. Aerosols, part 2 • Aerosols affect the weather and climate in two ways: • Many are hygroscopic (absorb water), and water vapor collects around them, which contributes to cloud formation; • Aerosols can either absorb or reflect sunlight, thus decreasing the amount of solar energy that reaches Earth’s surface. The Atmosphere

40. Discovery science • Discovery science describes natural structures and processes as accurately as possible through careful observation and analysis of data. • Data are recorded observations which can be either quantitative or qualitative. • Discovery science may lead to important conclusions via inductive reasoning, in which scientists derive generalizations based on a large number of specific observations. The Atmosphere

41. Hypothesis-based science • Hypothesis-based science is a process of inquiry that asks specific questions • Usually involves the proposing and testing of hypothetical explanations, or hypotheses, via the scientific method. The Atmosphere

42. Discovery of the ozone hole, part 1 • Scientists of the British Antarctic Survey first noticed a decline in the amount of stratospheric ozone during the (Southern Hemisphere) spring of 1985. • A region almost as large as North America was affected. • Record searches revealed evidence of ozone depletion in each of the previous eight years. The Atmosphere

43. Discovery of the ozone hole, part 2 • The BAS findings were initially dismissed as the result of instrument error. • Others argued that the ozone hole was real, but a normal phenomenon produced by the polar atmospheric circulation. • A third group argued that the ozone hole was caused by pollution. The Atmosphere

44. Discovery of the ozone hole, part 3 • A massive field study was launched in 1987 to settle the matter. • The scientists used satellites, aircraft, and balloons equipped with special instruments to collect atmospheric data. • The first finding was that the ozone hole was real. • The second finding was that high levels of chlorine monoxide (ClO) were present, a chemical that is known from laboratory studies to damage ozone. • Chlorine monoxide is a by-product of chlorofluorocarbons. The Atmosphere

45. Steps in the scientific method • The scientific method is a formal set of rules for forming and testing hypotheses. • Steps in the scientific method: • Observation • Question • Hypothesis • Prediction • Test The Atmosphere

46. Hypotheses • A hypothesis is an informed guess about the way a process works that enables a scientist to predict what will happen in different situations. • Hypotheses • Are possible explanations • Are based on past experience • Are valuable only if testable and falsifiable • Can be proven wrong, but can never be proven right The Atmosphere

47. Theory • A system of statements and ideas that explains a group of related facts or phenomena. • Hypotheses developed from a theory consistently resist scientists’ efforts to disprove them. The Atmosphere

48. Experiment • A way of testing a hypothesis or of searching for some unknown effect. • Proper experimental design is essential for the success of any experiment and must take into account the following: • The population of interest • Statistics to be used to analyze the data • Statistically representative samples of the population • Experimental treatment(s) and control(s) The Atmosphere

49. Atmospheric models, part 1 • Models are often used in the effort to better understand weather and climate processes. • A scientific model is an approximation or simulation of a real-world system. • A system is an entity that has components that function and interact in an orderly and predictable manner that can be described by fundamental physical principles. • The Earth-atmosphere system is comprised of the Earth’s surface features, plus that of the atmosphere. The Atmosphere

50. Atmospheric models, part 2 • Models include only the essential elements (or elements perceived to be essential) of a system. • Construction of a model often helps scientists determine which elements are essential or not. • The simplicity of a model can help scientists gain important insights into how a system works. • Models can also be used to predict how a system might respond to changes. The Atmosphere