METR 104:
Our Dynamic Weather

(Lecture w/Lab)
Some Notes on Topics Covered
in the Week of Feb. 6, 2012
Dr. Dave Dempsey
Dept. of Geosciences
SFSU

Temperature Patterns in Space and Time

By examining a few sets of observations of temperature, we have noticed some patterns of variation in temperature, in both time and space:

  1. From meteograms (which show weather conditions at one place at a series of times):

    1. Systematic variation in temperature over the course of a day
      1. generalized conceptual model: the daily temperature cycle
        • lowest temperatures near sunrise
        • temperature then rises to their highest values in mid afternoon (plus or minus an hour or two)
        • temperatures then generally decrease until near sunrise again

  2. From global plots of temperature in the lower atmosphere:

    1. Global spatial pattern in temperature (that is, patterns in space—that is, from place to place)

      1. warmest in the tropics, decreases with increasing latitude (farther from the equator), coldest in polar regions
      2. the variation from lower to higher latitudes is relatively rapid across a relatively narrow zone in the midlatitudes
        1. this feature noteworthy enough to be given its own name: the polar front
        2. the polar front is not oriented straight east-to-west, but has "wobbles" in it
          • the wobbles define alternating "tongues" of relatively warmer and colder air
          • the warm tongues "protrude" from lower latitudes (where it is warm) toward higher latitudes
          • the cold tongues "protrude" from higher latitudes (where it is cold) toward lower latitudes

    2. Global temporal patterns in temperature (that is, patterns in time)

      1. Global temperature pattern varies with time of year
        1. the Northern Hemisphere is generally colder in February and warmer in August
        2. opposite is true in Southern Hemisphere
        3. in both hemispheres, the polar front shifts northward by August and back southward by February

      2. At midlatitudes, the temperature pattern shows systematic variations over several days
        1. the alternating "tongues" of relatively colder and warmer air outlined by the polar front (that is, wobbles in the polar front) shift eastward over periods of days both hemispheres
        2. as the alternating tongues pass over any particular place, that place experiences variations in temperature over periods of days

What accounts for these spatial and temporal patterns of temperature?


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