CrossSection Analysis

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Cross-Section Analysis

• metr2413
• April 2, 2004

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Cross-Section Analysis

• Illustrates the vertical structure of the
  atmosphere (2D vs 1D)
• Compliments horizontal analyses to help diagnose
  three-dimensional structure
• Helps to determine the location of jets, fronts
  and other stable layers

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Analysis of soundings

• From a horizontal chart, identify the features
  you want to analyze (fronts, jet stream, etc.)
• Determine a line of radiosonde stations which
  is perpendicular to this feature.

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Identification of stable layers

• The second step is to locate the stable layers
  and tropopause in each of the soundings. If some
  of the stable layers represent fronts and can be
  identified on two or more adjacent soundings,
  they should be connected. The tropopause should
  be connected where it is behaving as a material
  surface.

Cross-section analysis

• On the cross-section chart, perform scalar
  analysis of temperature, potential temperature,
  winds, mixing ratio and others

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Thermal Wind Relationship in Isentropic
Coordinates

• Isentropic surfaces have a steep slope in regions
  of fronts. Flat isentropes indicate more
  unstable conditions and little/no change of the
  wind with height.
• Frontal zones are characterized by sloping
  isentropic surfaces which are vertically
  compacted (indicating strong static stability).
• In the stratosphere the static stability
  increases by about one order of magnitude.

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Isentropic Mean Meridional Cross Section
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Isentropes near Frontal Zones
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Surface Map for 12 UTC 30 December 1990
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Cross Section Taken Normal to Arctic Frontal
Zone12 UTC 30 December 1990
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Surface Map for 00 UTC 27 November 2001
DTX
DDC
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Sample Cross section for 00 UTC 27 November 2001
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Lab Assignment 11

• Using upper air soundings, construct your own
  cross-section from Brownsville, TX (BRO) to
  Aberdeen, SD (ABR) using the following location
  for data
• Brownsville, TX (BRO)
• Corpus Christi, TX (CRP)
• Dallas/Ft. Worth, TX (FWD)
• Norman, OK (OUN)
• Topeka, KS (TOP)
• Omaha, NE (OAX)
• Aberdeen, SD (ABR)
• Data should be from 12Z April 2, 2004
• Vertical coordinate should be pressure
• Plot potential temperature and mixing ratio

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310K _at_ 600mb 305K _at_ 700mb 297K _at_ 800mb 290K _at_
900mb
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300K _at_ 600mb 297K _at_ 700mb 289K _at_ 800mb 285K _at_
900mb
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309K _at_ 600mb 303K _at_ 700mb 297K _at_ 800mb 285K _at_
900mb
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Additional Notes

• On your chart, identify the location of the
  tropopause and any fronts that may be present
• The lab assignment and all relevant soundings are
  located at weather.ou.edu/metr2413
• Office Hours Tuesday/Thursday 130-230 SEC 1370