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Chapter 8 Weather

Chapter 8 Weather. Air Masses: Definition Air mass modification Major air masses influencing conterminous USA Atmospheric Lifting Mechanisms  Convergence: low pressure Convection: heating Orographic: frontal: warm and cold front Midlatitude Cyclonic Systems  .

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Chapter 8 Weather

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  1. Chapter 8 Weather • Air Masses: Definition Air mass modification Major air masses influencing conterminous USA • Atmospheric Lifting Mechanisms  Convergence: low pressure Convection: heating Orographic: frontal: warm and cold front • Midlatitude Cyclonic Systems  

  2. Air Masses Figure 8.2

  3. Atmospheric Lifting Mechanisms  Figure 8.6

  4. Dry and Moist Adiabatic Rise Figure 8.7

  5. Orographic Precipitation Figure 8.9

  6. Cold Front Figure 8.11

  7. Warm Front Figure 8.13

  8. Midlatitude Cyclone • Involves two air masses: mP and mT, they meet in the midlatitude, so the name. • Involves two atmospheric rising mechanisms: frontal (cold and warm) and low pressure • Cold front in moves faster and eventually catches the warm front (Occlusion) Figure 8.14

  9. Average and Actual Storm Tracks Figure 8.16

  10. Violent Weather • Thunderstorms: Upper Draft: Convective rise ( cumulus clods) by heat, thus more common in warm low latitude region. Down Draft:  caused by rain/hail, very dangerous for airplane • Tornadoes Topography conducive to Tornadoes: smooth surface to roll the air Mesocyclone (~10km in diameter) to pick up the rolling air and turn it vertical. • Tropical Cyclones: Tropical thunder storms, Easterly waves in trade wind or ITCZ Sea surface temperature has to be 26oC

  11. Thunderstorms Figure 8.19

  12. MesocycloneandTornado Figure 8.22

  13. Tornadoes Figure 8.24

  14. Easterly Wave Figure 8.25

  15. Tropical Cyclones Figure 8.26

  16. Hurricanes Gilbert and Catarina Figure 8.26

  17. Chapter 9 Water Resources • The Hydrologic Cycle   • Soil-Water-Budget Concept   • Groundwater Resources  

  18. Hydrologic Cycle Model The flow of water linked the atmosphere, ocean, land, and living things through exchanges of energy and matter. Round and round as it goes, the rivers never stop flowing and the oceans never overflow. Figure 9.1

  19. The Soil-Water Balance Equation P: Precipitation which can in various forms such as rain, snow, hail, a complete list in Table 9.1. AET: Actual evapotranspiration (evaporation + transpiration) R: Runoff water ΔS: change in soil water PET: The amount of water that would evaporate and transpire under optimum moisture condition, i.e. no shortage of water supply. AET <= PET Figure 9.3

  20. Types of Soil Moisture A block of soil is made up of three components, air, water, soil. The sum of the volume of air and water make up the total pore space in the soil. Volume Metric Soil Water = Vwater/(Vwater+Vair+Vsoil) Porosity=(Vwater+Vair)/(Vwater+Vair+Vsoil) Figure 9.8

  21. Soil-Moisture Availability Figure 9.9

  22. Surface Water Profile Root zone Zone of Aeration: Part of the pore space is filled with air. Capillary fringe layer Water table Ground water Zone of saturation All pore space is filled with water Capillary rise: liquid water rises through fine linear space

  23. Groundwater Characteristics Aquifer: a rock layer that is permeable to groundwater flow adequate for wells and springs. Confined: bounded above and below with impermeable layers, thus high water pressure and easy to extract. Unconfined: permeable layer on top and impermeable layers below, thus easily recharged from above, but need pump to draw water. Figure 9.17

  24. Groundwater Characteristics Figure 9.17

  25. Two Problems • Overdrawn. Due to demand for agricultural, industrial and urban use, groundwater table is decreasing . • Pollution: groundwater is recharged with surface water. Pollution of ground water will lead to pollution of groundwater, including, septic tank outflows, land fills, pestcides, herbcides, fertilizers, industrial waste injections etc. • point sources • non-point sources Figures FS 9.2.1a, 9.2.3

  26. Water Withdrawal by Sector Figure 9.21

  27. Chapter 10 Climate Climate is weather over time, including both mean and variation Climatic Classification Criteria Factors influencing Climate

  28. Factors Controlling Climate The ultimate controller on climate is energy and water. Any factors influencing these two impact the climate. They include: Latitude: insolation Land and Water: Marine and continental climate due to differences in heat capacity. Geographic Position and Prevailing Winds: Places at the windward side of a continent with prevailing winds carrying maritime air mass have maritime climate. Mountains and highlands: Mountains and highlands may prevent maritime air mass to reach inland. They force orographic rise and sequence moisture out of the air. Ocean Currents: Warm currents (e.g. Gulf stream) warms air and cool currents chills the air. Pressure and Wind Systems: The pressure “belts” and its seasonal shifting (e.g. ITCZ) influence precipitation.

  29. Climate Classification Classification criteria: temperature and precipitation and moisture efficiency for desert areas. • Tropical • Mesothermal • Microthermal • Polar • Highland • Desert

  30. Generalized Climate Regions Figure 10.4

  31. Chapter 11 Dynamic Planet   • Uniformitarianism: An assumption that the same physical processes active in the environment today have been operating throughout geologic time. • Geologic time scale: Eons, Eras, Periods, Epochs • Radioactive dating: half time • Seismic tomography • Magnetic reversal • Continental drift • Sea floor spreading

  32. Geologic Time Scale Earth age: 4.6 billion years condensed and congealed from a nebula of dust, gas and icy comets. Scales of Geologic Time Eons: Eras: Periods: Epochs: Zoic: life Protero-: former, anterior Phanero-: visible to the naked eye flowering plants Paleo-: old Meso-: middle Ceno-: recent Figure 11.1

  33. Earth’s Structure and Internal Energy   • Earth’s Core : Inner Core Outer Core  • Earth’s Mantle: Lower Mantle Upper Mantle Asthenosphere Uppermost Mantle   • Crust  

  34. How Scientists Know the Deep  Structure? Scientists cannot dig that deep. The deepest hole scientists ever dug is 12.23km (20 years of effort!) Scientists infer the deep Earth structure indirectly through seismic tomography. The rate of transmittance of seismic waves depends on the density of the structural material. Rigid matter transmits the seismic waves faster. Plastic zones simply do not transmit certain seismic waves. Some seismic waves are reflected when density changes, whereas others are refracted (or bent) as they travel through Earth.

  35. Earth’s Magnetism • At least 90% of Earth’s Magnetism is generated by fluid outer core. • Magnetic North is at 83o N, 114oW in 2005. Magnetic north pole migrates. It moved 1100 km in the past century. • Magnetic reversal: Magnetic polarity sometimes fades to zero and returns to full strength with magnetic poles reversed. It happened 9 times in the past 4 million years. The transition period between reversal is relatively short (1,000 ~10,000 years) • Current records indicates that magnetic fields decay over the last 150 years. We may be within 1000 years of magnetic reversal.

  36. Isostatic Adjustment Continental crust is lightest, “floating” on denser layers. When there is heavier loads, such as mountains, glaciers, , the crust “sink” deeper (like a boat loaded with cargo). Unloading these cargos will results in isostatic rebound as shown here. GPS can be used to study the rate of isostatic rebound. A group of scientists from UAF found that southern Alaska is rebounding much faster than they thought because of melting of glaciers Figure 11.4

  37. The Geologic Cycle Figure 11.5

  38. Eight natural elements make up 99% of Earth’s crust! Oxygen and Silicon make up 74.3%. There are more Oxygen in the crust (47%) than in the atmosphere (21%) !

  39. Crustal Movements: Sea Floor Spreading A remarkable feature of the sea floor: An interconnected worldwide mountain chain, forming a ridge ~64,000 km in length and ~1,000 km in width. Figure 11.13

  40. Magnetic Reversals Evidence of sea floor spreading: 1. The magnetic particles orient themselves in line with the magnetic fields when the lava appeared and its orientation is frozen in the rocks. 2. Radioactive dating: the farther away from the ridge, the older the age of the rocks. Figure 11.14

  41. Relative Age of the Oceanic Crust The oldest sea floor rock is 208 MBP (quite young compared to 4.6 Billion years of Earth). Figure 11.15

  42. Continents Adrift 7 major plates: Three kinds of plate boundaries: Convergent Divergent Transformative Figure 11.16

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