Chapter 8 Weather
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Transcript of Chapter 8 Weather
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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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Air Masses
Figure 8.2
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Atmospheric Lifting Mechanisms
Figure 8.6
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Dry and Moist Adiabatic Rise
Figure 8.7
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Orographic Precipitation
Figure 8.9
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Cold Front
Figure 8.11
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Warm Front
Figure 8.13
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Midlatitude Cyclone
Figure 8.14
1. Involves two air masses: mP and mT, they meet in the midlatitude, so the name.
2. Involves two atmospheric rising mechanisms: frontal (cold and warm) and low pressure
3. Cold front in moves faster and eventually catches the warm front (Occlusion)
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Average and Actual Storm Tracks
Figure 8.16
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Violent WeatherThunderstorms:
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
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Thunderstorms
Figure 8.19
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Mesocyclone andTornado
Figure 8.22
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Tornadoes
Figure 8.24
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Easterly Wave
Figure 8.25
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Tropical Cyclones
Figure 8.26
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Hurricanes Gilbert and Catarina
Figure 8.26
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The Hydrologic Cycle
Soil-Water-Budget Concept
Groundwater Resources
Chapter 9 Water Resources
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Hydrologic Cycle Model
Figure 9.1Round and round as it goes, the rivers never stop flowing and the oceans never overflow.
The flow of water linked the atmosphere, ocean, land, and living things through exchanges of energy and matter.
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The Soil-Water Balance Equation
Figure 9.3
SRAETP
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 waterΔS: 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
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Types of Soil Moisture
Figure 9.8
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)
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Soil-Moisture Availability
Figure 9.9
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Surface Water Profile
Root zone
Capillary fringe layer
Ground water
Zone of Aeration:Part of the pore space is filled with air.
Water table
Zone of saturationAll pore space is filled with water
Capillary rise: liquid water rises through fine linear space
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Groundwater Characteristics
Figure 9.17
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.
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Groundwater Characteristics
Figure 9.17
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Figures FS 9.2.1a, 9.2.3
Two Problems
1. Overdrawn. Due to demand for agricultural, industrial and urban use, groundwater table is decreasing .
2. 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
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Water Withdrawal by Sector
Figure 9.21
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Climate is weather over time, including both mean and variation
Climatic Classification Criteria
Factors influencing Climate
Chapter 10 Climate
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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.
Factors Controlling ClimateThe ultimate controller on climate is energy and water. Any factors influencing these two impact the climate. They include:
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Classification criteria: temperature and precipitation and moisture efficiency for desert areas.
Tropical
Mesothermal
Microthermal
Polar
Highland
Desert
Climate Classification
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Generalized Climate Regions
Figure 10.4
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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
Chapter 11 Dynamic Planet
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Geologic Time Scale
Figure 11.1
Earth age: 4.6 billion years condensed and congealed from a nebula of dust, gas and icy comets.
Scales of Geologic TimeEons: Eras: Periods: Epochs:
Zoic: lifeProtero-: former, anteriorPhanero-: visible to the naked eye flowering plantsPaleo-: oldMeso-: middleCeno-: recent
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Earth’s Core :
Inner Core
Outer Core
Earth’s Mantle:
Lower Mantle
Upper Mantle
Asthenosphere
Uppermost Mantle
Crust
Earth’s Structure and Internal Energy
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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.
How Scientists Know the Deep Structure?
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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.
Earth’s Magnetism
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Isostatic Adjustment
Figure 11.4
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
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The Geologic Cycle
Figure 11.5
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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%) !
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Crustal Movements: Sea Floor Spreading
Figure 11.13
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.
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Magnetic Reversals
Figure 11.14
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.
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Relative Age of the Oceanic Crust
Figure 11.15
The oldest sea floor rock is 208 MBP (quite young compared to 4.6 Billion years of Earth).
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Continents Adrift
Figure 11.16
7 major plates:
Three kinds of plate boundaries:ConvergentDivergent Transformative