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368 Cards in this Set
- Front
- Back
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What is the impact of pressure and wind on the landscape?
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Atmospheric pressure indirectly affects the landscape
Changes manifest primarily by changes in wind and temperature Wind has visible component to its activity Severe storm winds can drastically affect the landscape |
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The Nature of Atmospheric Pressure
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Gas molecules are not strongly bound to one another but are continuously in motion
The atmosphere exerts pressure on every surface it touches (force exerted on every surface the gas touches) Pressure is approx 14lbs per square inch near sea level |
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Atmospheric Pressure
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Force exerted by gas molecules
The force exerted by air molecules on all objects the air is in contact with |
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Factors Influencing Atmospheric Pressure
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Pressure is influenced by temperature, density, and dynamic
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Density and Pressure Relationships
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At higher density, particles are closer and collide more frequently, increasing pressure
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Temperature and Pressure Relationships
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Warmer particles move faster and collide more frequently, increasing pressure
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Dynamic Influences on Air Pressure
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Dynamic high
Thermal high Dynamic low Thermal low Dynamic influences work in tandem with influences from density to affect air pressure |
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Dynamic High
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Strongly descending air
Strongly descending air is usually associated with high pressure at the surface |
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Thermal High
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Very cold surface conditions
Very cold surface conditions are often associated with high pressure at the surface |
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Dynamic Low
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Strongly ascending air
Strongly rising air is usually associated with low pressure at the surface |
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Thermal Low
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Very warm surface conditions
Very warm surface conditions are often associated with relatively low pressure at the surface |
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Mapping Pressure with Isobars
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Pressure measured with a barometer
Typical units are milibars or inches of mercury Contour pressure values reduced to sea level Shows highs and lows, ridges and troughs Barometers Millibar |
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Barometer
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Instrument used to measure atmospheric pressure
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Millibar
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The most common unit of measure for atmospheric pressure
An expression of force per surface area |
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Isobars
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Show areas of high pressure and low pressure
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Ridge
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An elongated area of relatively high pressure
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Trough
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An elongated area of relatively low pressure
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Pressure Decreases with Altitude
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Pressure Gradient
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As with other types of isolines, the relative closeness of isobars indicates the horizontal rate of pressure change.
Represents the “steepness” of the pressure “slope” (or more correctly, the abruptness of the pressure change over a distance), a characteristic that has a direct influence on wind |
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Wind
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Vertical and horizontal atmospheric motions are called ___
Horizontal air movement |
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Origination of Wind
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Uneven heating of Earth’s surface creates temperature and pressure gradients
Direction of wind results from pressure gradient Winds blow from high pressure to low pressure |
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Pressure Gradient Force
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Characterized by wind moving from high to low pressure
Winds blow at right angles to isobars |
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The Coriolis Effect
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Turns wind to the right in the Northern Hemisphere, left in Southern Hemisphere
Only affects wind direction, not speed, though faster winds turn more |
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Geostrophic Wind
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wind that moves parallel to the isobars as a result of the balance between the pressure gradient and the Coriolis effect
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Friction
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wind is slowed by Earth’s surface due to friction, does not affect upper levels
Slows the wind and turns it towards lower pressure |
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Force Balances
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geostrophic and frictional balances
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Geostrophic Balance
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represents a balance between the pressure gradient force and the Coriolis effect
Winds blow parallel to isobars |
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Frictional Balance
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winds blow slightly towards low pressure and slightly away from high pressure
Winds slowed by friction weaken Coriolis, so pressure gradient force is stronger and turns the winds |
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Wind patterns around high and low pressure systems are anticyclonic and cyclonic, respectively
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Close isobar spacing indicates faster winds
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Winds increase rapidly with height, pressure decreases rapidly with height
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Anticyclone
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high pressure systems
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What are the four patterns of anticyclonic circulation?
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1. In the upper atmosphere of the Northern Hemisphere, the winds move clockwise in a geostrophic manner parallel to the isobars.
2. In the friction layer (lower altitudes) of the Northern Hemisphere, there is a divergent clockwise flow, with the air spiraling out away from the center of the anticyclone. 3. In the upper atmosphere of the Southern Hemisphere, there is a counterclockwise, geostrophic flow parallel to the isobars. 4. In the friction layer of the Southern Hemisphere, the pattern is a mirror image of the Northern Hemisphere, with air diverging in a counterclockwise pattern. |
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Cyclones
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low pressure systems
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Vertical Motions
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surface convergence and low pressure indicate rising motion
Surface divergence and high pressure indicate sinking motion Rising motion results in clouds and storms Sinking motion results in sunny skies |
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Wind Speed
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light pressure gradients (isobars close together) indicate faster wind speeds
Wind speeds are gentle on average |
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Vertical Variations in Pressure & Wind
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atmospheric pressure decreases rapidly with height
Winds aloft are much faster than at the surface Jet streams |
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The General Circulation of the Atmosphere
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atmosphere is in constant motion
Major semi permanent conditions of wind and pressure general circulation Principal mechanism for longitudinal and latitudinal heat transfer Second only to insolation as a determination for global climate The global atmospheric circulation |
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Hypothetical Pattern of A NonRotating Earth
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if earth were a nonrotating sphere with a uniform surface, we could expect a very simple global atmospheric circulation pattern
Strong solar heating at equator Little heating at poles Thermal low pressure forms over equator Thermal high forms over poles Ascending air over equator Descending air over poles Winds blow equatorward at surface, poleward aloft |
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The Hadley Cells
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two complete vertical convective circulation cells between the equator, where warm air rises in the ITCZ, and 25° to 30° of latitude, where much of the air subsides into the subtropical highs.
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Observed General Circulation
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addition of Earth’s rotation increases complexity of circulation
One semipermanent convective cell near the equator (Hadley Cell) Three latitudinal wind belts per hemisphere |
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Subtropical Highs
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persistent zones of high pressure near 30° latitude in both hemispheres
Result from descending air in Hadley cells Subsidence is common over these regions Regions of world’s major deserts No wind, horse latitudes |
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Trade Winds
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diverge from subtropical highs
Exist between 25°N and 25°S latitude Easterly winds: southeasterly in Southern Hemisphere, northeasterly in Northern Hemisphere Most reliable of winds “Winds of commerce” Heavily laden with moisture Do not produce rain unless forced to rise If they rise, they produce tremendous precipitation and storm conditions |
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Intertropical Convergence Zone (ITCZ)
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region of convergence of the trade winds
Constant rising motion and storminess in this region Position seasonally shifts (more over land than water) Doldrums |
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Westerlies
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form on poleward sides of subtropical highs
Wind system of the midlatitudes Two cores of high winds jet streams Rossby waves |
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Polar Highs
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thermal highs that develop over poles due to extensive cold conditions
Winds are anticyclonic; strong subsidence Arctic desert |
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Polar Easterlies
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Regions north of 60°N and south of 60°S
Winds blow easterly Cold and dry |
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Polar Front
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low pressure area between polar high and westerlies
Air mass conflict between warm westerlies and cold polar easterlies Rising motion and precipitation Polar jet stream position typically coincident with the polar front |
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The Seven (7) Components of the General Circulation
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1. Intertropical Convergence Zone (ITCZ)
2. Trade Winds 3. Subtropical Highs 4. Westerlies 5. Polar Front (Subpolar lows) 6. Polar Easterlies 7. Polar Highs |
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Most dramatic differences in surface and aloft winds is in tropics
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Antitrade winds
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tropical upperatmosphere westerly winds at the top of the Hadley cells that blow toward the northeast in the Northern Hemisphere and toward the southeast in the Southern Hemisphere.
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Seasonal Modifications in the General Circulation
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seven general circulation components shift seasonally
Components shift northward during Northern Hemisphere summer Components shift southward during Southern Hemisphere summer |
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Monsoons
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seasonal wind shift of up to 180°
Winds onshore during summer Winds offshore during winter Develop due to shifts in positions of ITCZ and unequal heating of land and water |
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Localized Wind Systems
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localized wind systems affect wind direction locally on diurnal time scales
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Sea Breezes
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water heats more slowly than land during the day
Thermal low over land, thermal high over sea Wind blows from sea to land |
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Land Breezes
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at night, land cools faster
Thermal high over land, thermal low over sea Wind blows from land to sea |
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Valley Breeze
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mountain top during the day heats faster than valley, creating a thermal low at mountain top
Upslope winds out of valley |
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Mountain Breeze
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mountain top cools faster at night, creating thermal high at mountain top
Winds blow from mountain to valley, downslope |
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Katabatic Winds
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cold winds that originate from cold upland areas, bora winds
Winds descend quickly down mountain, can be destructive |
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Foehn/Chinook Winds
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high pressure on windward side of mountain, low pressure on leeward side
Warm downslope winds Santa Ana winds |
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El Nino-Southern Oscillation
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warming of waters in the eastern equatorial Pacific
Associated with numerous changes in weather patterns worldwide Typically occurs on time scales of 3 to 7 years for about 18 months |
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Circulation Patterns - Walker Circulation
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General circuit of air flow in the southern tropical Pacific Ocean; warm air rises in the western side of the basin (in the updrafts of the ITCZ), flows aloft to the east where it descends into the subtropical high off the west coast of South America; the air then flows back to the west in the surface trade winds.
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ENSO
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Linked atmospheric and oceanic phenomenon of pressure and water temperature. Southern Oscillation refers to a periodic seesaw of atmospheric pressure in
the tropical southern Pacific Ocean basin. |
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El Nino
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a warming of eastern equatorial Pacific water and subsequent switching of the high and low air pressure patterns
Associated with varied weather patterns in different locations globally Periodic atmospheric and oceanic phenomenon of the tropical Pacific that typically involves the weakening or reversal of the trade winds and the warming of surface water off the west coast of South America. |
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La Nina
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atmospheric and oceanic phenomenon associated with cooler than usual water off the west coast of South America. Sometimes described as the opposite of El Niño.
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Causes of El Nino
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other Multiyear Atmospheric and Oceanic Cycles
Pacific Decadal Oscillation (PDO) North Atlantic Oscillation (NAO) Arctic Oscillation (AO) |
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The Impact of Atmospheric Moisture on the Landscape
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formation of fog, haze, clouds, and precipitation
Short term impacts of precipitation—floods Longer term impacts of the absence of precipitation—drought Geologic term impacts (i.e., caves) on Earth’s surface |
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The Hydrologic Cycle
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series of storage areas interconnected by various transfer processes, in which there is a ceaseless interchange of moisture in terms of its geographical location and its physical state.
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Chemistry of Water
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two hydrogen and one oxygen molecule (H2O)
Covalent bonds Electrical polarity of water molecule Hydrogen bonds |
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Important Properties of Water
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exists as a liquid at most points on Earth’s surface
Expands when it freezes; less dense than liquid water; ice floats in water Hydrogen bonding creates surface tension, a “skin” of molecules giving water a stickiness quality Capillarity Good solvent High specific heat |
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Liquidity
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One of the most striking properties of water is that it is liquid at the temperatures found at most places on Earth’s surface. The liquidity of water greatly enhances its versatility as an active agent in the atmosphere, lithosphere, and biosphere.
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Ice Expansion
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Because water expands as it approaches freezing, ice is less dense than liquid water. As a result, ice floats on and near the surface of water. If it were denser than water, ice would sink to the bottom of lakes and oceans, where melt- ing would be virtually impossible, and eventually many water bodies would become ice choked. In fact, because freshwater becomes less dense as it approaches its freezing point, water that is ready to freeze rises to the tops of lakes, and hence all lakes freeze from the top down.
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Surface Tension
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Because of electrical polarity, liquid water molecules tend to stick together—a thin “skin” of molecules forms on the surface of liquid water causing it to “bead.”
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Capillarity
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The action by which water can climb upward in restricted confinement as a result of its high surface tension, and thus the abil- ity of its molecules to stick closely together.
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Solvent Ability
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Water can dissolve almost any substance and it is sometimes referred to as the “universal solvent.”
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Specific Heat
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The amount of energy required to raise the temperature of 1 gram of a substance by 1°C. Also called specific heat capacity.
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Phase Changes of Water
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water typically exists in three states
Solid: ice Liquid: liquid water Gas: water vapor Latent heat is required to convert water to its different phases |
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Condensation
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gas to liquid
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Evaporation
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liquid to gas
Warmer temperatures evaporate more water Windiness increases evaporation Evapotranspiration |
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Freezing
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liquid to solid
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Melting
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solid to liquid
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Sublimation
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solid to gas and gas to solid
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Latent Heat
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Energy stored or released when a substance changes state.
For example, evaporation is a cooling process because latent heat is stored and condensation is a warming process because latent heat is released. |
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Phase Change Processes
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condensation: gas to liquid
Evaporation: liquid to gas Freezing: liquid to solid Melting: solid to liquid Sublimation: solid to gas and gas to solid Latent heat required for each process Latent heat as a source of atmospheric energy |
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Latent Heat of Melting
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The energy required to melt ice
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Latent Heat of Fusion
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The energy released as water freezes
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Latent Heat of Vaporization
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The energy required to convert liquid water to water vapor
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Latent Heat of Condensation
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Heat released when water vapor condenses back to liquid form.
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Latent Heat of Evaporation
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Energy stored when liquid water evaporates to form water vapor.
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Water Vapor
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a colorless, odorless, tasteless, invisible gas that mixes freely with the other gases of the atmo- sphere.
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Evapotranspiration
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The transfer of moisture to the atmosphere by
transpiration from plants and evaporation from soil and plants. |
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Potential Evapotranspiration
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This is the amount of evapotranspiration that would occur if the ground at the location in question were sopping wet all the time.
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Measures of Humidity
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humidity—amount of water vapor in the air
Vapor pressure—contribution of water vapor to total atmospheric pressure Relative humidity—how close the air is to saturation Saturation represents the maximum amount of water vapor the air can hold Saturation depends on temperature Saturation vapor pressure |
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Humidity
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amount of water vapor in the air
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Absolute Humidity
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one measure of the actual water vapor content of air, expressed as the mass of water vapor in a given volume of air, usually as grams of water per cubic meter of air.
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Water Vapor Capacity
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The maximum possible absolute humidity
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Specific Humidity
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A direct measure of water-vapor content expressed as the mass of water vapor in a given mass of air (grams of vapor/kilograms of air).
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Vapor Pressure
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contribution of water vapor to total atmospheric pressure
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Saturation Vapor Pressure
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The maximum possible vapor pressure (the water vapor capacity) at a given temperature
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Relative Humidity
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how close the air is to saturation
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Temperature Relative Humidity Relationship
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temperature and relative humidity are inversely related
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Dew Point Temperature / Dew Point
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the temperature at which saturation occurs in the air.
It is dependent upon the amount of water vapor present. High dew points indicate abundant atmospheric moisture. Dew points can be only equal or less than air temperatures. If saturation is reached and air temperatures cool further, water vapor is removed from the air through condensation. |
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Sensible Temperature
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refers to the temperature as it feels to a person’s body. It involves not only the actual air temperature but also other atmospheric conditions, particularly rela- tive humidity and wind, that influence our perception of warmth and cold.
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Frost Point
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when air reaches saturation at temperatures below freezing
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Condensation
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conversion of vapor to liquid water
Surface tension makes it nearly impossible to grow pure water droplets Supersaturated air Need particle to grow droplet around, a cloud condensation nuclei Liquid water can persist at temperatures colder than 0°C without a nuclei—supercooled |
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Condensation Process
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Saturation alone is not enough to cause condensation, however. Surface tension makes it virtually impossible to grow liquid droplets of pure water from a vapor phase. Be- cause surface tension inhibits an increase in surface area, it is very difficult for additional water molecules to enter or form a droplet. (On the other hand, molecules can easily leave a small droplet by evaporation, thereby decreasing its area.) Thus, it is necessary to have a surface on which con- densation can take place. If no such surface is available, no condensation occurs.
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Supersaturated
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has a relative humidity greater than 100 percent
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Condensation Nuclei
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Tiny atmospheric particles of dust, bacteria,
smoke, and salt that serve as collection centers for water molecules. |
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Supercooled Water
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Water that persists in liquid form at temperatures below freezing.
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Adiabatic Processes
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dry adiabatic lapse rate: 10°C/1000m (5.5°F/1000ft)
Lifting condensation level (LCL) Saturated adiabatic lapse rate: ~6°C/1000m (3.3°F/1000ft) Parcel lapse rates versus environmental lapse rate |
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Dry Adiabatic Lapse Rate
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10°C/1000m (5.5°F/1000ft)
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Lifting Condensation Level (LCL)
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The altitude at which rising air cools sufficiently to reach 100 percent relative humidity at the dew point temperature, and condensation begins.
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Saturated Adiabatic Lapse Rate
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~6°C/1000m (3.3°F/1000ft)
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Clouds
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Visible accumulation of tiny liquid water droplets or ice crystals
suspended in the atmosphere. |
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Classifying Clouds
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classification (3 primary cloud forms)
Cirrus clouds Stratus clouds Cumulus clouds |
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Cloud Forms
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1. Cirriform clouds (Latin cirrus, “a lock of hair”) are thin and wispy and composed of ice crystals rather than water droplets.
2. Stratiform clouds (Latin stratus, “spread out”) appear as grayish sheets that cover most or all of the sky, rarely broken up into individual cloud units. 3. Cumuliform clouds (Latin cumulus, “mass” or “pile”) are massive and rounded, usually with a flat base and limited horizontal extent but often billowing upward to great heights. |
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Cloud Types
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high clouds (over 6 km)
Middle clouds (from 2 to 6 km) Low clouds (less than 2 km) Clouds of vertical development |
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Cirriform Clouds
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are thin and wispy and composed of ice crystals rather than water droplets.
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Stratiform Clouds
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appear as grayish sheets that cover most or all of the sky, rarely broken up into individual cloud units.
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Cumuliform Clouds
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are massive and rounded, usually with a flat base and limited horizontal extent but often billowing upward to great heights.
Tall cumulus cloud associated with rain, thunderstorms, and other kinds of severe weather such as tornadoes and hurricanes. |
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Cloud Families
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High
Middle Low Vertical |
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High Clouds
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clouds over 6km
generally found above 6 kilometers (20,000 feet). Because of the small amount of water vapor and low temperature at such altitudes, these clouds are thin, white, and composed of ice crystals. Included in this family are cirrus, cirrocumulus, and cirrostratus. These high clouds often are harbingers of an approaching weather system or storm. |
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Middle Clouds
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clouds from 2 to 6 km
normally occur between about 2 and 6 kilometers (6500 and 20,000 feet). They may be either stratiform or cumuliform and are composed of liquid water. Included types are altocumulus and altostratus. The puffy altocumulus clouds usually indicate settled weather conditions, whereas the lengthy altostratus are often associated with changing weather. |
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Low Clouds
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clouds less than 2km
Low clouds usually are below 2 kilometers (6500 feet). They sometimes occur as individual clouds but more often appear as a general overcast. Low cloud types include stratus, stratocumulus, and nimbostratus. These low clouds often are widespread and are associated with somber skies and drizzly rain. |
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Clouds of Vertical Development
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Grow upward from low bases to heights of over 15 km occasionally
A fourth family, clouds of vertical development, grows upward from low bases to heights of as much as 15 kilometers (60,000 feet). Their horizontal spread is usually very restricted. They indicate very active vertical movements in the air. The relevant types are cumulus, which usually indicate fair weather, and cumulonimbus, which are storm clouds. |
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Fog
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A cloud whose base is at or very near ground level.
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Radiation Fog
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results when the ground loses heat through radiation, usually at night. The heat radiated away from the ground passes through the lowest layer of air and into higher areas. The air closest to the ground cools as heat flows conductively from it to the relatively cool ground, and fog condenses in the cooled air at the dew point, often collecting in low areas.
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Advection Fog
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develops when warm, moist air moves horizontally over a cold surface, such as snow- covered ground or a cold ocean current. Air moving from sea to land is the most common source of advection fogs.
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Unslope Fog or Orographic Fog
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is created by adiabatic cooling when humid air climbs a topographic slope.
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Evaporation Fog
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results when water vapor is added to cold air that is already near saturation.
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Dew
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The condensation of beads of water on relatively cold surfaces.
usually originates from terrestrial radiation leaving and surface cooling Moisture condensation on surfaces that have been cooled to saturation Will appear as water droplets |
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Frost
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occurs when air temperature lowers to saturation point, when the saturation point is below 0°C (32°F)
Will appear as large numbers of small white crystals |
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Stable Air
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Air that rises only if forced.
parcel is negatively buoyant, will not rise without an external force |
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Unstable Air
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Air that rises without being forced.
parcel is positively buoyant, will rise without an external force |
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Precipitation
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originates from clouds
Condensation insufficient to form raindrops |
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Collision/Coalescence
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tiny cloud drops collide and merge to form larger drops
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Ice Crystal Formation
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Bergeron process
Ice crystals and supercooled droplets coexist in cold clouds Ice crystals attract vapor, supercooled drops evaporate to replenish the vapor Ice crystals fall as snow or rain |
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Forms of Precipitation
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rain: liquid water
Snow: cloud ice crystals Sleet: snow melted and frozen again before hitting land, ice pellets Glaze (Freezing Rain): water falls as liquid, freezes to surfaces Hail: strong updrafts are required |
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Rain
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liquid water
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Snow
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cloud ice crystals
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Sleet
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snow melted and frozen again before hitting land, ice pellets
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Glaze or Freezing Rain
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water falls as liquid, freezes to surface
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Hail
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Strong updrafts are required
Rounded or irregular pellets or lumps of ice produced in cumulonimbus clouds as a result of active turbulence and vertical air currents. Small ice particles grow by collecting moisture from supercooled cloud droplets. |
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Convective Lifting
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Air lifting with showery precipitation resulting from
convection. |
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Orographic Lifting
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Uplift that occurs when air is forced to rise over top- ographic barriers.
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Rain shadow
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Area of low rainfall on the leeward side of a mountain
range or topographic barrier. |
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Frontal Lifting
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The forced lifting of air along a front.
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Convergent Lifting
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Air lifting as a result of wind convergence.
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Isohyet
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A line joining points of equal numerical value of precipitation.
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What regions have high precipitation?
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tropics
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What regions have low precipitation?
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deserts and Poles
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Precipitation Variability
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Interannual Variability of Precipitation
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Acid Rain
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Sources of Acid Precipitation
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Principle Acids
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Measuring Acidity
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Damage from Acid Precipitation
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Distribution of Acid Rain in the US
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Air Masses
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An extensive body of air that has relatively uniform properties
in the horizontal dimension and moves as an entity. |
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Properties of an Air Mass
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large (diameter > 1600 km), Uniform horizontal properties, Recognizable entity; travel as one
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Origin of Air Masses
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remains over a uniform land or sea surface long enough to acquire its uniform characteristics
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Air Mass Classification
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two letter classification system
Lowercase letter indicates moisture content c —continental, dry m—maritime, humid Uppercase letter indicates source region P—polar source region T—tropical source region A—arctic source region E—equatorial source region |
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North American Air Masses
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Continental Polar (cP)
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Arctic (A)
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Maritime Polar (mP)
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Maritime Tropical (mT)
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Continental Tropical (cT)
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Equatorial (E)
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Fronts
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clash over midlatitudes between polar and tropical air masses
A sharp zone of discontinuity between unlike air masses. |
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Four Primary Frontal Types
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cold front
warm front stationary front occluded front |
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Cold Fronts
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cold air advancing
protruding “nose” of cold air faster than warm fronts lift warm air ahead of cold fronts identified by blue line with triangles pointing in direction of frontal motion |
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Warm Fronts
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warm air advancing
gentle slope of warm air rising above cool air slow cloud formation and precipitation indicated by red line with semicircles pointing in the direction of warm air motion |
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Stationary Fronts
|
no advance of air masses
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Occluded Fronts
|
cold air overtakes warm air
Cold front catches warm front, removing the energy of the storm (which is the warm air) Occlusions mark the end of the cyclone’s life Marked as a purple line with alternating triangles and half circles in direction of advancing cold air |
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|
Atmospheric Disturbances
|
storms
Midlatitude disturbances—i.e., midlatitude cyclones Tropical disturbances— easterly waves and hurricanes Localized severe weather—thunderstorms and tornadoes |
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|
Midlatitude Disturbances
|
i.e., mitlatitude cyclones
|
|
|
Midlatitude Cyclones
|
exist between 35–70° latitude
Roughly 1600 km in size Central pressure near 990 to 1000 mb Converging counterclockwise circulation in Northern Hemisphere Circulation creates fronts Westward tilt with increasing elevation in Northern Hemisphere |
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|
Tropical Disturbances
|
.
|
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Tropical Cyclones
|
A storm most significantly affecting the tropics and
subtropics; an intense low-pressure center that is essentially circular in shape. When wind speed reaches 119 km/hr (74 mph; 64 knots), they are called hurricanes in North America and the Caribbean. |
|
|
Hurricanes
|
A tropical cyclone with wind speeds of 119 km/hr (74 mph;
64 knots) or greater affecting North or Central America. |
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Easterly Waves
|
A long but weak migratory low-pressure trough in the
tropics. oriented N–S Little cyclonic circulation Convergence behind wave, divergence ahead of wave Can intensify to tropical cyclones |
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Thunderstorms
|
A relatively violent convective storm accompanied by thunder and lightning.
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Tornadoes
|
A localized cyclonic low-pressure cell surrounded by a whirling cylinder of violent wind; characterized by a funnel cloud extending below a cumulonimbus cloud.
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Weather Changes Behind Front
|
temperature
Winds Pressure |
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Cyclone Movement
|
steered by jet stream
System has a cyclonic wind circulation Cold front advances faster than center of the storm |
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Life Cycle of a Cyclone
|
cyclogenesis to occlusion
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Cyclogenesis
|
the birth of cyclones
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Midlatitude Cyclone Occurrence and Distribution
|
typically 6–15 cyclones exist worldwide
More numerous and better developed in winter than in summer Move more equatorward during summer |
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|
Midlatitude Anticyclones
|
anticyclones—high pressure systems
Subsiding, diverging winds at the surface Flow is clockwise around an anticyclone Move slightly slower than cyclones |
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|
Relationships of Cyclones and Anticyclones
|
occur independently, but have a functional relationship
Anticyclone follows a cyclone Anticyclones typically reside behind cyclone’s cold front |
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Categories of Tropical Disturbances
|
.
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Tropical Depression
|
.
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What are some characteristics of hurricanes?
|
prominent low pressure center, winds spiral inward
Steep pressure gradient and strong winds Warm moist air enters storm to form rain and release latent heat Eye wall and eye Anticyclonic winds aloft, divergence aloft |
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|
Origin of a Hurricane
|
over warm water
A few degrees N or S of equator No significant wind shear Hurricane season Hurricane movement Irregular tracks within the flow of the trade winds Typically begin moving east–west, some curve poleward |
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|
Eye of a Hurricane
|
The nonstormy center of a tropical cyclone,
which has a diameter of 16 to 40 kilometers (10 to 25 miles) and is a singular area of calmness in the maelstrom that whirls around it. |
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Hurricane Movement
|
.
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Hurricane Tracks
|
.
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Hurricane Life Span
|
.
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Damage and Destruction of Hurricanes
|
high winds, torrential rain, and isolated tornadoes
Primary destruction— storm surge flooding SaffirSimpson scale |
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Storm Surges
|
A surge of wind-driven water as much as 8 meters (25 feet) above normal tide level, which occurs when a hurricane advances onto a shoreline.
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|
Saffir-Simpson Scale
|
Classification system of hurricane strength with category 1 the weakest and category 5 the strongest.
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|
Thunderstorms
|
violent convective storms
Accompanied by thunder and lightning Atmospheric conditions prone to thunderstorm formation |
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|
Thunderstorm Formation Stages
|
cumulus stage
Mature stage Dissipating stage |
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|
Cumulus Stage
|
.
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Mature Stage
|
.
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Dissipating Stage
|
.
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Lightning
|
electric discharge in thunderstorms
Separation of charges due to ice particles in a cloud Positive charges on Earth’s surface Thunder |
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|
Lightning Types
|
cloud to ground
Cloud to cloud Within cloud |
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Cloud to Ground
|
.
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Cloud to Cloud
|
.
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Within Cloud
|
.
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Thunder
|
The sound that results from the shock wave produced by the instantaneous expansion of air that is abruptly heated by a lightning bolt.
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|
Tornadoes
|
deep low pressure vortex, typically less than 400 meters in diameter
Fast winds, sometimes in excess of 300 mph Originate above ground, water vapor condenses into funnel cloud Contains vapor and debris |
|
|
Funnel Clouds
|
Funnel-shaped cloud extending down from a cumulo- nimbus cloud; a tornado is formed when the funnel cloud touches the surface.
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|
Tornado Formation
|
vertical wind shear creates rotation with horizontal axis
Horizontal rotation tilted into vertical by thunderstorm updraft Mesocyclone and tornado development |
|
|
Supercell Thunderstorm
|
.
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|
Mesocyclone
|
Cyclonic circulation of air within a severe thunderstorm;
diameter of about 10 kilometers (6 miles). |
|
|
Strength of a Tornado
|
.
|
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|
Enhanced Fujita Scale (EF Scale)
|
Classification scale of tornado strength, with
EF-0 being the weakest tornadoes and EF-5 being the most powerful. |
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|
Tornado Classification
|
.
|
|
|
Tornado "Hot Spots"
|
.
|
|
|
Waterspout
|
A funnel cloud in contact with the ocean or a large lake;
similar to a weak tornado over water. |
|
|
Storm Watch
|
Weather advisory issued when conditions are favorable
for strong thunderstorms or tornadoes. |
|
|
Storm Warning
|
Weather advisory issued when a severe thunderstorm
or tornado has been observed in an area; people should seek safety immediately. |
|
|
Climate Classification
|
need a consistent climate classification scheme to understand numerous climate regions
Earliest known scheme was by the ancient Greeks 2200 years ago Classified three major climate regions |
|
|
Early Classification Schemes
|
.
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|
Temperate Zone
|
.
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Torrid Zone
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.
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Frigid Zone
|
.
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|
The Koppen Climate Classification System
|
Köppen climate classification system
Based on a database of annual and monthly average temperature and precipitation Four of five major groups classified by temperature Fifth group classified by precipitation Subdivided the five groups further based on temperature and precipitation relationships Climographs The modified Köppen classification system |
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|
The Modified Koppen Climate Classification System
|
.
|
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|
Koppen Letter Code System
|
Three letters; first describes group, second describes precipitation, third describes temperature
|
|
|
Climographs
|
Chart showing the average monthly
temperature and precipitation for a weather station. |
|
|
The Value of a Climograph
|
.
|
|
|
World Distribution of Major Climate Types
|
weather records. How do we explain their locations?
|
|
|
Tropical Humid Climates (Group A)
|
molded by the tropical latitudinal regions
Winterless climates; little temperature change Moisture is prevalent Precipitation influenced by ITCZ |
|
|
Tropical Wet Climate (Af)
|
equatorial
Monotonous climate Daily temperature range exceeds annual range High humidity Rainfall multiple times a day High solar angle year round; ITCZ influences rainfall |
|
|
Tropical Savannah Climate (Aw)
|
lies north and south of Af climates
Seasonal alteration of wet and dry periods due to position changes of ITCZ Smallest rainfall amounts of tropical regions |
|
|
Tropical Monsoonal Climate (Am)
|
regions with prominent monsoonal wind pattern
Extensive rainfall during highSun season Cherrapunji, India averages 425 inches Cloud cover reduces temperatures slightly in summer versus spring |
|
|
Dry climates (Group B)
|
over about 30% of land area worldwide
Lack of uplift or lack of moisture Typical in subtropics Marine deserts |
|
|
Subtropical Desert Climate (BWh)
|
lie near subtropical highs
Precipitation is scarce (rare) and unreliable (highly variable) Precipitation that does form is short lived and intense Hot temperatures Large diurnal range of temperature |
|
|
Subtropical Steppe Climate (BSh)
|
typically surrounds BWh climates
Separate desert climate from humid climate Extremes are muted in steppe regions Cooler temperatures More rainfall Seasonal concentration of rainfall |
|
|
Midlatitude Desert Climate (BWk)
|
Desert climate characterized by warm sum- mers but cold winters.
far removed from oceanic influence Meager and erratic precipitation Most precipitation occurs in summer Cold winters, overall cooler temperatures Greater annual temperature range |
|
|
Midlatitude Steppe Climate (BSk)
|
occupies transitions between desert and humid climates
Greater precipitation than midlatitude deserts Less temperature extremes than midlatitude deserts |
|
|
Mild Midlatitude Climates (Group C)
|
transition between warmer tropical climates and colder severe midlatitude climates
Hot summers, mild winters Highly variable precipitation amounts |
|
|
Mediterranean Climate (Csa, Csb)
|
Mild midlatitude climate characterized by dry
summers and wet winters. modest annual precipitation in winter, summer is virtually rainless Mild winters and hot summers Clear skies especially in summer Most is Csa (hot summers); Csb climates have mild summers and are more coastal |
|
|
Humid Subtropical Climate (Cfa, Cwa)
|
Mild midlatitude climate characterized by
hot summers and precipitation throughout the year. warm to hot summers; high humidity (Cfa days are hot and sultry) Precipitation reaches summer maximum, some drop off for winter Winter temperatures in Cfa regions are mild; typically cooler than mediterranean climates |
|
|
Marine West Coast Climate (Cfb, Cfc)
|
Mild midlatitude climate characterized by
mild temperatures and precipitation throughout the year. influenced by onshore flow from midlatitude westerlies Occurs when no topographic boundaries inhibit flow of maritime air inland Frequently cloudy with precipitation Temperate climate Wettest of the midlatitudes |
|
|
Severe Midlatitude Climates (Group D)
|
nly in Northern Hemisphere
Continentality—remoteness from oceans Four recognizable seasons; long, cold winter and short summer Subdivided into two types based on temperature |
|
|
Humid Continental Climate (Dfa, Dfb, Dwa, Dwb)
|
Severe midlatitude climate characterized by
hot summers, cold winters, and precipitation throughout the year. dominated by westerlies and associated frequent weather changes Warm summers, cold winters Generally low precipitation; higher amounts near coasts Winter precipitation associated with cyclones; summer with convection |
|
|
Subarctic Climate (Dfc, Dfd, Dwc, Dwd)
|
Severe midlatitude climate found in high latitude
continental interiors, characterized by very cold winters and an extreme annual temperature range. winters are long, dark, and bitterly cold Summers are short; spring and fall pass quickly Coldest temperatures; little precipitation Largest annual temperature ranges (i.e., 90°F to 98°F in Verhoyansk, Siberia) |
|
|
Polar Climates (Group E)
|
receive little insolation
No average temperature above 50°F Extremely dry, but classified as non arid |
|
|
Tundra Climate (ET)
|
Polar climate in which no month of the year has an
average temperature above 10°C (50°F). southern boundary the “treeline” Northern boundary border of any plant cover Long, dark winters Brief, cool summers Little precipitation Winters not as severely cold as subarctic climate region |
|
|
Ice Cap Climate (EF)
|
Polar climate characterized by temperatures below freezing throughout the year.
mainly Greenland and most of Antarctica Permanent cover of ice and snow Ice plateaus; high latitude with high altitude Very limited precipitation, essentially polar deserts |
|
|
Highland Climate (Group H)
|
High mountain climate where altitude is dominant
control. Designated H in Köppen system. nearly infinite variations from place to place Altitude more significant than latitude in highlands Exposure (whether a slope is windward or leeward) High diurnal temperature variations due to thin, dry air |
|
|
Global Climate Change
|
changes in climate on long time scales
Weather is “noise”, climate is longterm signal Episodic events (i.e., El Niño and the Pacific Decadal Oscillation: PDO) versus longterm global climate change Numerous time scales to consider (i.e., temperature) 70 million years, clear global cooling trend 150,000 years, temperature fluctuated 10,000 years, sharp warm up 150 years, warming trend relative to last 1000 years |
|
|
Paleoclimatology
|
proxy measures of climate (i.e., ice cores, tree rings)
Oxygen isotope analysis Lighter versus heavier isotopes High 18O/ 16O ratio, glaciation |
|
|
Dendrochronology
|
study of past climate through tree ring analysis
|
|
|
Oxygen Isotope Analysis
|
.
|
|
|
Oceanic Sediments
|
.
|
|
|
Coral Reefs
|
ratio of 18O/ 16O in coral reefs
Height of old reefs Ice cores Ratio of 18O/ 16O serves as a thermometer Provide direct atmospheric composition measurements Pollen data Radiocarbon dating |
|
|
Ice Cores
|
.
|
|
|
Pollen Data
|
.
|
|
|
Causes of LongTerm Climate Change
|
atmospheric aerosols
Large quantities of aerosols can block insolation and lower temperature Result from volcanic eruptions or asteroid impacts (years, decades?) Anthropogenic impacts |
|
|
Climate Change Causes (cont.)
|
solar output fluctuations
Sunspot activity related to solar output (years) Variations in EarthSun relations Shape of Earth’s orbit Inclination of Earth’s axis Precession of Earth’s axis Milankovitch cycles (tens of thousands of years) Greenhouse gas concentrations Greenhouse gas concentrations related to temperature Evidence of CO2 increase being anthropogenic Feedback mechanisms Positive feedback mechanisms Water vapor feedback Roles of the oceans Absorb large amounts of carbon Methane hydrates Heat transfer from low latitudes to high latitudes Climate models General circulation models (GCMs) Numerous assumptions Accuracy of the models |
|
|
Atmospheric Aerosols
|
.
|
|
|
Solar Output Fluctuations
|
.
|
|
|
Variations in Earth Sun Relations
|
.
|
|
|
Eccentricity of Orbit
|
.
|
|
|
Milankovitch Cycles
|
Combination of long-term astronomical cycles
involving Earth’s inclination, precession, and eccentricity of orbit; believed at least partially responsible for major periods of glaciation and deglaciation. . |
|
|
Greenhouse Gasses Concentration
|
.
|
|
|
Feedback Mechanisms
|
.
|
|
|
Albedos
|
The reflectivity of a surface. The fraction of total solar radiation that is reflected back, unchanged, into space.
|
|
|
Positive Feedback Mechanism
|
.
|
|
|
Water Vapor Feedback
|
.
|
|
|
Roles of the Ocean
|
.
|
|
|
Methane Hydrates
|
.
|
|
|
Climate Models
|
.
|
|
|
General Circulation Models (GCMs)
|
.
|
|
|
Evidence Of Current Global Warming
|
of 9 warmest years on record occurred since 2000 (since 1880)
Global temperature increasing at 0.13 °C per decade Ocean temperatures increasing to depths of 9800 feet Sea level rise Temperatures in Arctic increasing at twice global rate Sea ice in Arctic decreasing by 7.4 percent per decade Ice caps and glacier melt leading to sea level rise Temperatures on top of a permafrost layer have increased by 5.4 °F Number of intense tropical cyclones increased since 1970 Amount of water vapor in atmosphere increased Changes in precipitation amounts Concentrations of carbon dioxide correlated with temperature Carbon dioxide concentrations correlate with increased anthropogenic greenhouse gases (CO2 increase also correlated with the end of the last ice age: see new study published in late February) Carbon dioxide increasing at a rate faster than observed in last 800,000 years NJ climate variability 18952012 |
|
|
Consequences Of Global Warming
|
projected climate in the upcoming century
Climate will warm at about 0.4 °F per decade Changes will be greater than those observed during 20th century Estimated increase of temperature from 3.3 °F to 7.2 °F Sea level rise Stronger tropical cyclones Increased precipitation |
|
|
Potential Climate Change Impacts
|
managing climate change
Knowledge: Develop a better understanding of the details of future climate change. Mitigation: Reduce emissions of carbon dioxide and other greenhouse gases. Adaptation: Increase the resilience of society to climate change. Leadership: Raise public awareness of the challenges posed by climate change and the need to mitigate and adapt. |
|
|
Summary
|
The tropical humid climates exist at tropical latitudes and are characterized by warm, constant temperatures and rainfall
Dry climates exist near the subtropics and are characterized by hot, dry conditions Mild midlatitude climates constitute a transition between warmer tropical climates and cold severe midlatitude climates Mild midlatitude climates typically have long and hot summers and mild winters, and have modest precipitation Severe midlatitude climates only occur in the Northern Hemisphere Severe midlatitude climates have long, cold winters and short summers, and have large annual temperature ranges Polar climates receive little insolation and are permanently cold and dry Highland climates depend on elevation of mountainous terrain for their climate characteristics Creative paleoclimatology methods are used to understand the Earth’s past climate There are multiple factors that influence longterm climate change Global warming is related to the increase in carbon dioxide release by humans |
|
|
The Structure of the Earth
|
understanding of Earth’s structure based on minute fraction of total depth (less than 8 miles)
Good deal of information inferred by geophysical means Four regions of Earth’s interior |
|
|
Earth's Hot Interior
|
.
|
|
|
Four Regions of Earth's Interior
|
crust
Mantle Outer Core Inner core |
|
|
Crust
|
depth of 5 km below ocean to near 20 km below land
Less than 1% of the Earth’s volume, 0.4% of Earth’s mass Moho discontinuity |
|
|
Mohorovicic (Moho) Discontinuity
|
The boundary between Earth’s crust and
mantle. |
|
|
Mantle
|
extends to depth of 2900 km (1800 miles)
Largest of four shells Makes up 84% of total volume, 67% of total mass Three sublayers Lithosphere Asthenosphere Rigid rocks—lower mantle |
|
|
Three Sublayers of the Mantle
|
lithosphere
athenosphere rigid rocks |
|
|
Lithosphere
|
Tectonic plates consisting of the crust and upper rigid mantle. Also used as a general term for the entire solid Earth (one of the Earth “spheres”).
|
|
|
Athenosphere
|
Plastic layer of the upper mantle that underlies the lithosphere. Its rock is dense, but very hot and therefore weak and eas-
ily deformed. |
|
|
Rigid Rocks
|
lower mantle
|
|
|
Outer Core
|
molten, extends to depth of 5000 km
|
|
|
Inner Core
|
dense mass with radius of about 1450 km
Primarily made of iron/nickel or iron/silicate Two zones combined make up 15% of the Earth’s volume and 32% of the Earth’s mass Magnetic field of Earth controlled by outer core Magnetic poles not the same as the axial poles |
|
|
Earth's Magnetic Field
|
.
|
|
|
Plate Tectonics and the Structure of Earth
|
.
|
|
|
"Continental Drift"
|
.
|
|
|
Plate Tectonics
|
.
|
|
|
The Composition of Earth
|
.
|
|
|
Minerals
|
naturally formed compounds and elements of Earth
|
|
|
Characteristics of Minerals
|
solid
Found in nature Inorganic Specific chemical composition Contains atoms that arrange in patterns to form crystals |
|
|
Important Crustal Minerals
|
silicates—combine oxygen and silicon, the most common elements in the lithosphere
Oxides—elements that are combined with oxygen Sulfides—combination of sulfur and another element (i.e., pyrite, Figure 133) Sulfates—contain sulfur and oxygen Carbonates—lightcolored minerals that are composed of a combination of carbon, oxygen and an element (i.e., limestone) Halides—derived from word “salt”, salty minerals Native elements—gold and silver |
|
|
Silicates
|
combine oxygen and silicon, the most common elements in the lithosphere
|
|
|
Oxides
|
elements that are combined with oxygen
|
|
|
Sulfides
|
combination of sulfur and another element (i.e., pyrite, Figure 133)
|
|
|
Sulfates
|
contain sulfur and oxygen
|
|
|
Carbonates
|
lightcolored minerals that are composed of a combination of carbon, oxygen and an element (i.e., limestone)
|
|
|
Halides
|
derived from word “salt”, salty minerals
|
|
|
Native Elements
|
gold and silver
|
|
|
Rocks
|
composed of many minerals
Fewer than 20 minerals make up 95% of the composition of crustal rocks |
|
|
Outcrop
|
Surface exposure of bedrock.
|
|
|
Bedrock
|
.
|
|
|
Reoglith
|
A layer of broken and partly decomposed rock particles that covers bedrock.
|
|
|
Petrology
|
characteristics of different rocks
|
|
|
Three Major Rock Groups or Classes
|
.
|
|
|
Igneous Rocks
|
igneous—“fiery inception”
Magma—molten rock beneath Earth’s surface Lava—molten rock when it flows onto Earth’s surface Pyroclastics Classification of igneous rocks is based on mineral composition and texture Texture based on how rocks cool Those formed by cooling and solidification of molten rock |
|
|
Magma
|
molten rock beneath Earth’s surface
|
|
|
Lava
|
molten rock when it flows onto Earth’s surface
|
|
|
Pyroclastics
|
Solid rock fragments thrown into the air by volcanic explosions.
|
|
|
Two Types of Igneous Rocks
|
Plutonic (Intrusive) Rocks
Volcanic (Extrusive) Rocks |
|
|
Plutonic (Intrusive) Rocks
|
hose that form within the Earth
Rocks cool beneath Earth’s surface Surrounding rocks insulate the magma intrusion, slowing cooling Individual minerals in a plutonic rock can grow to large size Granite |
|
|
Granite
|
the most common and well-known plutonic (intrusive) rock; coarse-grained rock consisting of both dark- and light-colored minerals; forms from felsic (relatively high silica content) magma.
|
|
|
Volcanic (Extrusive) Rocks
|
form on Earth’s surface
Cool rapidly Generally do not show individual mineral crystals, but can if the crystals are formed from shattered rock that was explosively ejected Basalt |
|
|
Basalt
|
Fine-grained, dark (usually black) volcanic rock; forms from mafic (relatively low silica content) lava.
|
|
|
Sedimentary Rocks
|
external processes cause rock disintegration
Material transported by water as sediment Over long periods, large amounts of sediment build to large thicknesses Exert enormous pressure, which causes particles in sediment to interlock Chemical cementation takes place Forms sedimentary rock Strata—horizontal layers of sedimentary rock; sometimes tilted into vertical by Earth processes Two primary types: clastic and chemical/organic ___ rocks Form as a result of transport of mineral material by water |
|
|
Sediment
|
Small particles of rock debris or organic material deposited by water, wind, or ice.
|
|
|
Strata
|
horizontal layers of sedimentary rock; sometimes tilted into vertical by Earth processes
Distinct layers of sediment or layers in sedimentary rock. |
|
|
Stratification
|
.
|
|
|
Bedding Planes
|
Flat surfaces separating one sedimentary layer from the next.
|
|
|
Clastic (Detrital) Sedimentary Rocks
|
composed of fragments of preexisting rocks
Also known as detrital rocks Shale is an example Conglomerate; composed of pebblesized fragments |
|
|
Chemical and Organic Sedimentary Rocks
|
formed by precipitation of soluble materials or complicated chemical reactions
Limestone and coal are examples Organic sedimentary rocks such as coal form from remains of dead plants and animals |
|
|
Metamorphic Rocks
|
rocks which were originally igneous or sedimentary and have been drastically changed by heat and pressure
Causes a “cooking” of rocks Rearranges the crystal structure of the original rock Contact metamorphism: rock contacts magma and is rearranged Regional metamorphism: large volumes of rock are subjected to heat and pressure over long time scales Limestone becomes marble; sandstone becomes quartzite, shale becomes slate Two primary types, schist and gneiss |
|
|
Contact Metamorphism
|
rock contacts magma and is rearranged
|
|
|
Regional Metamorphism
|
large volumes of rock are subjected to heat and pressure over long time scales
|
|
|
Hydrothermal Metamorphism
|
Metamorphism associated with hot,
mineral-rich solutions circulating around preexisting rock. |
|
|
Foliated Metamorphic Rocks
|
.
|
|
|
Nonfoliated Metamorphic Rocks
|
.
|
|
|
Schist
|
metamorphic rocks with narrow foliations
|
|
|
Gneiss
|
road, banded foliations
|
|
|
The Rock Cycle
|
processes where rocks can transition from igneous rocks to sedimentary rocks to metamorphic rocks
The transition cycle through the different rock types |
|
|
Continental and Ocean Floor Rocks
|
sedimentary rocks make up 75% of the continents
Sedimentary cover is not thick Continental crust: sial (silicon and aluminum) Ocean floor crust: sima (silicon and magnesium) Ocean lithosphere is more dense than continental lithosphere Ocean crust can be subducted into the asthenosphere Continental and ocean floor rocks possess different characteristics, which are important in geophysical processes |
|
|
Isotasy
|
recognition of differences between oceanic crust, continental crust, and mantle
The recognition of the differences between continental crust, oceanic crust, and mantle |
|
|
The Study of Landforms
|
topography—surface configuration of Earth
Landform—individual topographic feature of any size Elements of landform study Structure Process Slope Drainage Relief |
|
|
Topography
|
surface configuration of Earth
|
|
|
Landform
|
individual topographic feature of any size
Landforms are characterized by structure, process, slope, and drainage |
|
|
Geomorphology
|
The study of the characteristics, origin, and development of landforms.
|
|
|
Elements of Landform Study
|
structure
Process Slope Drainage Relief |
|
|
Structure
|
.
|
|
|
Process
|
.
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|
|
Glaciation
|
.
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|
|
Slope
|
.
|
|
|
Drainage
|
.
|
|
|
Relief
|
The difference in elevation between the highest and lowest points in an area; the vertical variation from mountaintop to valley bottom.
|
|
|
Some Critical Concepts
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internal and External Geomorphic Processes
Internal: originate from within Earth, increase relief of land surface External: originate from sources above the lithosphere, such as the atmosphere or oceans; decrease relief of land surface |
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Internal and External Geomorphic Processes
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internal and external geomorphic processes are responsible for the relief of Earth
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Internal Processes
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Geomorphic processes originating
below the surface; include volcanism, folding, and faulting. |
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External (Denudation) Processes
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Destructive processes that serve to
denude or wear down the landscape. Includes weathering, mass wasting, and erosion. |
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Uniformitarianism
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The present is the key to the past”
Processes which shaped the landscape of the past are the same that will shape the future Uniformitarianism allows us to use geologic time to infer what happened in the past based on the present |
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Catastrophism
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the theory that changes in the earth's crust during geological history have resulted chiefly from sudden violent and unusual events. Often contrasted with uniformitarianism.
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Geologic Time
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past periods of time over which geologic processes operate
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Scale and Pattern
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An Example of Scale
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an example of scale—five perspectives Horseshoe Park
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Pattern and Processes in Geomorphology
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The Pursuit of Pattern
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major landform assemblages of the world
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What are some of the impacts of storms on the landscape?
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Storm conditions can result in widespread damage through flooding and wind damage. Can provide diversity in vegetative cover, increase lake and pond size, sculpt coastlines, etc.
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