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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
Air Masses
Figure 8.2
Atmospheric Lifting Mechanisms
Figure 8.6
Dry and Moist Adiabatic Rise
Figure 8.7
Orographic Precipitation
Figure 8.9
Cold Front
Figure 8.11
Warm Front
Figure 8.13
Midlatitude Cyclone
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)
Figure 8.14
Average and Actual Storm Tracks
Figure 8.16
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
Thunderstorms
Figure 8.19
Mesocyclone and
Tornado
Figure 8.22
Tornadoes
Figure 8.24
Easterly
Wave
Figure 8.25
Tropical Cyclones
Figure 8.26
Hurricanes Gilbert and Catarina
Figure 8.26
Chapter 9 Water Resources
The Hydrologic Cycle
Soil-Water-Budget Concept
Groundwater Resources
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
The Soil-Water Balance Equation
P  AET  R  S
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
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
Soil-Moisture Availability
Figure 9.9
Surface Water Profile
Zone of
Aeration:
Part of the
pore space is
filled with air.
Root zone
Capillary fringe layer
Water table
Zone of saturation
All pore space is
filled with water
Ground water
Capillary rise: liquid water rises through fine linear space
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
Groundwater Characteristics
Figure 9.17
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
Figures FS 9.2.1a, 9.2.3
Water Withdrawal by Sector
Figure 9.21
Chapter 10 Climate
Climate is weather over time, including
both mean and variation
Climatic Classification Criteria
Factors influencing Climate
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.
Climate Classification
Classification criteria: temperature and
precipitation and moisture efficiency for
desert areas.
Tropical
Mesothermal
Microthermal
Polar
Highland
Desert
Generalized Climate Regions
Figure 10.4
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
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
Earth’s Structure and Internal Energy
Earth’s Core :
Inner Core
Outer Core
Earth’s Mantle:
Lower Mantle
Upper Mantle
Asthenosphere
Uppermost Mantle
Crust
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.
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.
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
The Geologic Cycle
Figure 11.5
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%) !
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
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
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
Continents Adrift
7 major plates:
Three kinds of plate boundaries:
Convergent
Divergent
Transformative
Figure 11.16