GEOG 140
Intro Physical Geography
Lecture Notes
Global Temperatures
Temperature Concepts and Measurement
-all objects above absolute zero have volume and molecular motion
-energy associated with molecular motion-kinetic energy
-more energy-faster the movement
-temperature describes energy/speed of movement
Temperature Scales
-three scales for measuring temperature
-Celsius- boiling point 100oC, freezing point 0oC
-Fahrenheit- boiling point 212oF, freezing point 32oF
-Kelvin-boiling point 373 K, freezing point 273 K-absolute zero
–minus 273oC
temperature vs. heat
-temperature measures the kinetic energy of molecules
-does not measure number of molecules or the density
-heat of a substance depends on volume, temperature, and heat
capacity
Principal Temperature Controls
-latitude
-single most important influence on temperature variations
-subsolar point (insolation)
-day length and Sun angle change
-example-five cities with different latitudes (fig. 5.4, pg. 122)
-altitude
-temperatures decrease with increasing altitude
-normal lapse ate (3.5oF/1000 ft)
-18,000ft- 50% density sea level
-ability to absorb and radiate sensible heat reduced
-average air temperatures lower
-nighttime cooling greater
-day-night differential greater
-sun light shadow contrast greater
-cloud cover
-global average about 50%
-effects vary with type, height, and density
-reduce insolation that reaches the ground
-night-act as insulation and radiate longwave energy
-day-reflect insolation
-most variable component of Earth’s radiation budget
-land-water heating differences (five controls)
-evaporation
-84% of global evaporation from oceans
-latent heat of evaporation
-removes energy and lowers temperatures
-more over oceans
-transparency
-water allows penetration of light to an average of 200ft
-large energy reservoir
-land is opaque
-energy is absorbed in a much thinner layer
-rapid heating/rapid heat loss
-specific heat
-heat capacity of an object
-water requires more energy to raise temperature than land
-movement
-mixing in water (vertical and horizontal)
-ocean currents and sea surface temperatures
-higher ocean temp. result in higher evaporation to overlying air
resulting in lower ocean temp.
-negative feedback mechanism
-summary of marine effects and continental effects (Fig. 5.7 pg.127)
-maritime effect
-moderating influences near coasts/islands
-continental effect
-greater min/max difference daily and annually
Earth’s Temperature Pattern
-tropical zone on each side of the equator experiences the least change between
January and July
-higher amounts of net radiation at lower latitudes
-middle and upper latitudes (winter)
-isotherms tightly packed
-pronounced temperature gradient
-contrast between land and ocean temperatures