1. Cross-Section Analysis metr2413 April 2, 2004

2. 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

3. 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.

4. 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

5. 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.

6. Isentropic Mean Meridional Cross Section

8. Isentropes near Frontal Zones

9. Surface Map for 12 UTC 30 December 1990

10. Cross Section Taken Normal to Arctic Frontal Zone: 12 UTC 30 December 1990

11. Surface Map for 00 UTC 27 November 2001 DDC DTX

12. Sample Cross section for 00 UTC 27 November 2001

13. 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

15. 310K @ 600mb 305K @ 700mb 297K @ 800mb 290K @ 900mb

16. 300K @ 600mb 297K @ 700mb 289K @ 800mb 285K @ 900mb

17. 309K @ 600mb 303K @ 700mb 297K @ 800mb 285K @ 900mb

19. 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 1:30-2:30 SEC 1370