weather and climate - it's all geography · 10/22/2013 1 monday, october 07, 2013 geography...
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Monday, October 07, 2013
Geography 02:
Weather & Climate
Weather and Climate
►Weather
Day-to-day variations in temperature and precipitation
►Climate
Statistical summary of weather conditions through time
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Solar Energy
►Radiant energy from sun
►Powers circulation of atmosphere and oceans and supports life on Earth
►Varies across Earth’s surface
Insolation
►Amount of energy intercepted by Earth
► 2 factors
Intensity of solar radiation
Angle of incidence
Duration of sunlight
Varies by season
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Intensity of Solar Radiation
Angle of incidence
Varies daily & seasonally
Axial tilt = 23.5 degrees
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Length of Day
►Total heat received by a place is dependent upon the number of hours of sunlight and its intensity
►Equator
►Higher latitudes
Seasonal Variation in Radiation
►Varies because of angle of incidence, day length, distance from sun
►Equator
►High latitudes
►Temperature
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Heat Transfer
►Responsible for movement of energy from place to place on Earth
►Radiation (radiant energy) Energy
Electromagnetic waves
Radiate
Examples
2 wavelengths: Short (sun) and long (Earth)
Greenhouse Effect
►Short vs. long waves
►Greenhouse gases
Critical to heat exchange
Water vapor, carbon dioxide, ozone, methane
►Increased greenhouse gases = increased global warming
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Latent Heat Exchange
►Transfers energy from low to high latitudes
►Causes precipitation
►Two types Sensible
►Detectable by touch
Latent ►“In storage” in water
and water vapor
►Latent heat exchange
Heat Exchange & Atmospheric Circulation
►Convection Upward movement of fluids caused by heating
“Boiling water”
Atmosphere
►Advection Horizontal
movement of air
Monsoons
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Precipitation
►“Normal” precipitation
►Condensation Conversion of water from vapor to liquid state
►ALL air holds water Dependent on temperature
►Saturation vapor pressure Maximum water vapor air can hold at a
particular temperature
Relative Humidity
►Water content of air
► Percent of water air could hold at a given temperature
► Fluctuates hourly as temperature changes
► Saturation point = condensation
►Condensation = clouds
Temperature Relative Humidity
86 degrees F 50% if holds half water vapor possible
71 degrees F 75%
60 degrees F 100%
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Convectional Precipitation
Warm, humid air rises, expanding and cooling
Saturation point is reached
Clouds form
Adiabatic cooling ►Decrease in temperature that results from
expansion of rising air
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Orographic Precipitation
►Wind forces air up and over mountains
►Rain on windward side
►Desert on leeward side: Rain shadow
►Examples
Cascades & Sierras
Rockies
Exception: Appalachians
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Frontal Precipitation
►Air forced up a boundary between cold and warm air masses
►Air mass Region of air with similar characteristics
►Cold front Cold air mass moves towards warm air mass
Typical weather
►Warm front Warm air mass moves towards cooler air mass
Typical weather
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Pressure and Winds
► Air density
Warm air = less dense
► Pressure gradient
Difference in pressure between two places
► Coriolis Effect
Indirect, curving path of wind caused by rotation of the Earth
Strongest in polar regions
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Coriolis Effect
Global Circulation ► 4 zones
Intertropical convergence zone (ITCZ)
► Convectional precipitation
► Trade winds
Subtropical high-pressure zones
► Areas of dry, bright sunshine, little precipitation
Midlatitude low-pressure zones
► Polar front
►Westerlies
Polar high-pressure zones
► Dense air, high pressure
► Little precipitation
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Ocean Circulation Patterns ►Wind creates waves
and currents
►Gyres
Wind-driven circular flows
►El Niño
Occasional shifts in ocean circulation
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Storms
►Cyclones Large low-pressure areas
Winds ►Counterclockwise in Northern Hemisphere
►Clockwise in Southern Hemisphere
►Hurricanes and typhoons Tropical cyclones
Need warm, moist air ►Most powerful over oceans
Storm surge ►Elevated sea level in center of storm
►Midlatitude cyclones
Climate
►Summary of weather conditions over several decades or more
►Influences
►Changes over time
►Humans and climate
►2 primary measures Temperature
Precipitation
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Air Temperature
►Variation
Latitude
Seasonal solar energy input
Elevation
Topography
Precipitation ►Variable between places and through
time
►Worldwide variation = 0-120 inches
►Global circulation patterns
►Amount of precipitation
►Reliability
►Regularity
Soil saturation
Human adjustments
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Classifying Climate
►Allows analysis and planning
►Communication
►Köppen System
Wladimir Köppen, 1918
Distribution of plants
5 basic climate types with subdivisions
Most widely used system
Climate Regions
►Horizontal bands based on latitude
►Climate regions similar to
Bioregions
Temperature and precipitation maps
►Other influences
Continents
Mountains
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Humid Low-Latitude Tropical Climates (A)
►Warm all year
►Humid tropical (Af, Am) +/- 10 degrees N/S of equator
Warm & humid; Little seasonal temp. variation
High temps; Rain
Amazon River Basin, Equatorial Africa, Islands of Southeast Asia
► Seasonally humid tropical climates (Aw) Concentrated rainfall
►Seasonal shifts of ITCZ
Central & South America
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Dry Climates (B)
►Dry climates, BW & BS 35% of Earth’s land area
Border low-latitude humid climates on North and South
North Africa, Central Asia
►Desert climates (BWh, BWk) Warm and dry
Subtropics
New Mexico (BWh), China (BWk)
► Semi-arid climates (BSh, BSk) Transitional areas between deserts and humid areas
Grasslands, steppes
Seasonal temperature contrasts
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Warm Midlatitude Climates (C)
► Seasonal temp variation
► Less precipitation
►Humid subtropical (Cfa, Cw) Latitude: 25-40 degrees on east side of continents
Eastern China, SE US, Brazil, Argentina
►Marine west coast (Cfb, Cfc) Continental west coasts, 35-65 degrees
Mild climates
California to coastal Alaska, Southern Chile
►Mediterranean climates (Cs) Dry summers with seasonal precipitation
Cold Midlatitude Climates (D)
►Humid continental climates (Dfa, Dwa, Dfb, Dwb) Strong contrasts
Remote from oceans = little moisture
Interior & eastern side of Northern Hemisphere Continents (35-60 degrees)
► Subarctic climates (Dfc, Dwc, Dfd, Dwd) Northern edge of humid continental climates
No agriculture
Northern Hemisphere only
Vegetation: Boreal forests
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Polar Climates (E)
►High-latitude climates
►Low temps
►Extreme seasonal variability
►Tundra climate (ET) Permafrost
Tundra
►Ice-cap climates (EF) Near poles & high altitudes at low latitudes
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Climate Change
► 3 hypotheses
►Astronomical
Geometry of Earth’s orbit
Sunspots
►Geologic
Continental drift
Volcanic eruptions
►Human
Atmospheric Changes
Vegetation Changes
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