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Experiment #1: Thermal

Experiment #1: Thermal. By: Steven Van Horn A&OS C115/C228. Outline of Experiment. Experiment: To ascertain how a thermal responds to varying sound speeds in a compressible atmosphere versus an incompressible atmosphere Prediction: Thermal ascent will become slower as csnd is decreased

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Experiment #1: Thermal

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  1. Experiment #1: Thermal By: Steven Van Horn A&OS C115/C228

  2. Outline of Experiment • Experiment: To ascertain how a thermal responds to varying sound speeds in a compressible atmosphere versus an incompressible atmosphere • Prediction: Thermal ascent will become slower as csnd is decreased • Hypothesis: As the atmosphere becomes more incompressible the faster the thermal will have to respond to compression H L

  3. DTDM Model Setup • Common among experiments • Dx = 1000 m, Dz = 250 m, Dt = 1.0 s • Neutral atmosphere • Initially calm • Varied among experiments • csnd is set to 50 m/s, 75 m/s, & 100 m/s

  4. Outline of Results • Show 3 figures comparing ’ for the incompressible case compared with ’ for the compressible cases • Show 2 figures examining a vertical profile of p’ • Analyze results • Evaluate hypothesis

  5. Results • This plot is showing the anelastic ’ minus the non-anelastic ’ (where csnd = 100 m/s)

  6. Results • This plot is showing the anelastic ’ minus the non-anelastic ’ (where csnd = 75 m/s)

  7. Results • This plot is showing the anelastic ’ minus the non-anelastic ’ (where csnd = 50 m/s) Lets look at the vertical profile of p’ to see if we can explain why a thermal in a compressible atmosphere travels up faster than one in an incompressible atmosphere

  8. Results • csnd =  • csnd = 100 m/s • csnd = 75 m/s • csnd = 50 m/s

  9. Results

  10. Summary of Results • We can see from the three figures that by t = 6 the thermals in a compressible atmosphere have greater ’ higher in the atmosphere compared to the thermal in the incompressible atmosphere • We can also see that as we increase the sound speed the magnitude of the difference between the incompressible and compressible cases decrease • p’ up the center of the thermals are weaker for the thermals in the compressible atmosphere compared to the thermal in the incompressible atmosphere

  11. Evaluation of Hypothesis • According to the DTDM model, my hypothesis that thermals in an incompressible atmosphere rise faster than ones in a compressible atmosphere was incorrect

  12. Conclusions • Thermals in a compressible atmosphere rise faster than those in an incompressible atmosphere • Smaller sound speeds resulted in faster rising thermals • This was explained by a weaker p’ force acting downward as csnd decreased

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