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Topographic Effects on Typhoon Nari (2001): Model Verification and Sensitivity Experiments

Topographic Effects on Typhoon Nari (2001): Model Verification and Sensitivity Experiments. Ming-Jen Yang 1 , Hsiao-Ling Huang 1 , Da-Lin Zhang 2 1 National Central University, Taiwan 2 University of Maryland, USA. Why studied Typhoon Nari (2001)?. Unique track Slowly moving Long duration

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Topographic Effects on Typhoon Nari (2001): Model Verification and Sensitivity Experiments

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  1. Topographic Effects on Typhoon Nari (2001): Model Verification and Sensitivity Experiments Ming-Jen Yang1,Hsiao-Ling Huang1, Da-Lin Zhang2 1National Central University, Taiwan 2University of Maryland, USA

  2. Why studied Typhoon Nari (2001)? • Unique track • Slowly moving • Long duration • Warm ocean • Heavy rainfall • Severe flooding Sui et al. (2002) EOS article

  3. MM5 model physics (Control) TC initialization: Davis and Low-Nam (2001)

  4. Track Comparison

  5. Time Series of SLP and Vmax

  6. 24-h rainfall on 09/16 6km MM5 2km MM5 OBS

  7. 24-h rainfall on 09/17 2km MM5 OBS 6km MM5

  8. 24-h rainfall on 09/18 OBS 2km MM5 6km MM5

  9. 3-day rainfall on 09/16~09/18 2km MM5 OBS 6km MM5

  10. Average Rainfall on Taiwan Percentage wrt Rain Gauge OBS

  11. 3-Day Total Rainfall versus Terrain Height Rain Gauge OBS 2km MM5

  12. Cloud Features CWB: 0916_0100 UTC CTL: 0916_0000 UTC Iso-surface of Snow (0.01 g/kg) and Cloud Water (0.3 g/kg)

  13. Radar CV Composite Before Landfall OBS MM5

  14. Radar CV Composite After Landfall OBS MM5

  15. Sounding Comparison(within Eyewall) MM5 Simulation Observed Sounding

  16. Horizontal Cross Section ofPressure Perturbations 0916_1400 UTC 5 ~ 6 hPa 8 ~ 9 hPa MM5 Simulation (wrt. aHorizontal Area Mean) Radar Retrieval (wrt. aStation Sounding) Courtesy of T.-C. Chen and Y.-C. Liou

  17. Radial Wind wrt RCWF Radar @ 3 km Height Obs Vr (6 km pixel) MM5 Vr (dx = 6 km) -45.1 -41.9 43.6 41.4 Courtesy of T.-C. Chen and Y.-C. Liou

  18. MM5 Simulated Vr & Vt Nari at Sea (@ 3 km Height) Tangential Velocity Radial Velocity

  19. MM5 Simulated Vr & Vt Nari Landfall (@ 3 km Height) Tangential Velocity Radial Velocity

  20. Over Ocean Radar Echo (color) Condensational Heating (contour) A B After Landfall C D

  21. Over Ocean Radar Echo (color) Tangential Velocity (contour) A B After Landfall C D

  22. Over Ocean Radar Echo (color) Radial Velocity (contour) A B After Landfall C D

  23. Terrain Sensitivity Experiments

  24. 75% Terrain 50% Terrain 25% Terrain No Terrain

  25. Time series of SLP and Vmax

  26. 100% Terrain 75% Terrain 50% Terrain 878 631 533 585 770 24-h Rainfall On 09/16 25% Terrain No Terrain

  27. Conclusions ■After 22-h integration, the MM5 can simulate Nari’s landfall over the observed location in northern Taiwan with 3-h timing error. ■ For the 3-day-total rainfall averaged over Taiwan, the 6-km (2-km) MM5 can reach 80% (88%) of the observed amount. ■ The 2-km MM5 can simulate the observed storm intensity prior to landfall, the pressure filling and shrinking of eyewall during the landfall period, and the pressure gradient near the inner core.

  28. Conclusions ■After landfall, Taiwan’s terrain induces strong asymmetry on kinematic and precipitation structure, and lower the max. heating along mountain slopes. ■ The terrain impact on Nari’s intensity is quite linear, i.e., higher terrain producing a weaker typhoon. However, terrain impact on the accumulated rainfall on Taiwan is nonlinear. ■ Nari’s complex tracks near Taiwan result from the interactions between the steering flow, Taiwan topography, and terrain-induced mesoscale forcings

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