Chapter 3
Air Temperature
Visualizing Physical Geography
Copyright © 2008 John Wiley and Sons Publishers Inc.
Surface and Air Temperature
Surface Temperature
When solar radiation strikes the ground what happens to:
• Shortwave radiation?
• Longwave radiation ?
• Sensible heat flows?
• Latent heat transfer?
• Convection?
Visualizing Physical Geography
Copyright © 2008 John Wiley and Sons Publishers Inc.
Temperatures Close to the
Ground
• Temperatures on the ground
usually more extreme than
temperatures at standard height
(4 ft.)
• Soil, surface, and air
temperatures vary throughout the
day
Visualizing Physical Geography
Copyright © 2008 John Wiley and Sons Publishers Inc.
Surface and Air Temperature
Environmental Contrasts: Urban and Rural Temperatures
Surface materials influence temperature strongly
Why?
Transpiration?
Evapotranspiration?
Visualizing Physical Geography
Copyright © 2008 John Wiley and Sons Publishers Inc.
The Urban Heat Island
City centers tend to be several degrees warmer
than surrounding suburbs and countryside.
Why?
Albedo
evapotranspiration
High-Mountain Environments
• Reduced air pressurereduced oxygen to
lungs
• Fewer air moleculessun’s rays stronger What do these graphs
• Less CO2 and water vaporreduced
show?
greenhouse effect
Temperature Inversion: reversal of normal temperature pattern
so that air temperature increases with altitude
Occurs when
cold marine
air slips under
warm air.
Daily and Annual Cycles of Air
Temperature
• Insolation varies by season
• Net radiation varies daily
• Positive after sunrise
• Peaks at noon
• Decreases to negative by sunset
• Air temperature varies daily
When is lowest temp?
When max? Why
Land and Water Contrasts
Temperature
Ranges for
Maritime and
Inland?
Daily and Annual Cycles of Air Temperature
Annual Net Radiation and Temperature Cycles
Annual cycle of daily insolation affectsnet radiation,
which affectsmonthly mean air temperature
Review sheet
#16
Isotherm?
Air temperature maps- high, low temp, gradients
Temperature gradient: rate
of temperature change
along a selected line or
direction
World Patterns of Air Temperature
Factors Controlling Air Temperature Patterns
Three main factors explaining world isotherm patterns:
1. Latitude affects annual insolation, temperatures, and seasonal temperature
variation
2. Maritime-continental contrast
3. Elevation
Patterns to note:
• Large land masses in Arctic and
subarctic zones are extremely cold
•Ice and snow reflect insolation
• Temperatures decrease from equator
to poles
• Highlands are colder than
surrounding lowlands.
• Temperatures in equatorial
regions?
• Continents heat/cool faster
than oceans
Temperature Structure of the Atmosphere
Lapse Rate: rate at which
air temperature drops with
increasing altitude
Visualizing Physical Geography
Copyright © 2008 John Wiley and Sons Publishers Inc.
Temperature Structure of the Atmosphere
Aerosols: tiny particles present
in the atmosphere
Temperature Structure of the Atmosphere
Stratosphere and Upper Layers
Stratosphere: What is happening to
temperature?
• Contains ozone layer
Visualizing Physical Geography
Copyright © 2008 John Wiley and Sons Publishers Inc.
Global Warming and the Greenhouse Effect
Factors Influencing climatic Warming and Cooling
Earth is getting warmer. Intergovernmental Panel on Climate Change:
global warming is “unequivocal”, very likely caused by human activity
Greenhouse Gases:
• Carbon dioxide (CO2)
• Methane (CH4)
• Chlorofluorocarbons (CFC’s)
• Tropospheric ozone (O3)
Temp
?
• Nitrous oxide (N2O)
What trends do you see in the graph?
Visualizing Physical Geography
Copyright © 2008 John Wiley and Sons Publishers Inc.
Global Warming and the Greenhouse Effect
Greenhouse Gases
• Some pollutants
have
a cooling effect
• Some factors are
natural
• Net warming effect of 1.6 W/m2
Global Warming and the Greenhouse Effect
The Temperature Record
Reconstructing temperature records:
• Thermometers
• Historical data
• Tree rings
• Coral growth
• Ice cores
Visualizing Physical Geography
Copyright © 2008 John Wiley and Sons Publishers Inc.
Global Warming and the Greenhouse Effect
• 2005 warmest year recorded since mid-19th century
• 2005, 1998, 2002, 2003,2006 five warmest years since 1400
• Earth’s temperature up:
• 0.6º C (1.1º F) in last 30 years
• 0.8º C (1.4º F) in last 100 years
• IPCC projects increase in global temperatures between 1.8º C (3.2º F)
and 4.0º C (7.2º F) by 2100
Visualizing Physical Geography
Copyright © 2008 John Wiley and Sons Publishers Inc.
Potential future effects of
greenhouse warming???
Global Warming and the Greenhouse Effect
International efforts to reduce greenhouse emissions?
Solutions?