1. Numerical simulation on the effects of latent heating and Taiwan topography on Typhoon Morakot (2009) 莫拉克颱風之數值模擬研究：颱風、地形、及降雨
指導教授：王重傑 博士
學生：陳郁涵

2. About Typhoon Morakot Affect Taiwan during 7-9 August 2009
The most serious typhoon-induced damages over southern Taiwan in 50 years.
Maximum accumulated rainfall of 2884 mm, surpassing previous record of 1987 mm set by Typhoon Herb in 1996.

3. About Typhoon Morakot
Morakot was embedded in the unusually strong large-scale monsoon gyre (Hong et al., 2010).
Weak steering flow made it move slowly.
With most rain to the south of typhoon center.
the high topography of Taiwan enhanced uplifting and increased the rainfall significantly (Ge at el., 2010).

4. About Typhoon Morakot Why it moved so slowly?
Three points are inseparable:
─ the track of typhoon (slow movement)
─ the asymmetric convection and latent
heat release
─ topography of Taiwan that enhanced
latent heating at fixed location
Why it moved so slowly?
─ simply the steering flow?
─ the latent heating (LH) effect ???

5. Model and experiment designs
Cloud-Resolving Storm Simulator (CReSS)
(X,Y,Z)dim = 576 x 480 x 50
dx,dy,dz = 3km x 3km x 500m
dzmin = 100 m
from 8/ UTC to 8/ UTC (96 hrs)

6. extreme rainfall on 8/8 – 8/9
(from the NSC Scientific Report on Typhoon Morakot)

7. Result

8. Control v.s. JTWC best track
✽The two tracks
are similar.

9. (24hr) accumulated rainfall CWB v.s. Model

13. accumulated rainfall TRMM PR v.s. Model

14. asymmetric rainfall structure

17. Sensitivity Experiment

18. Different water vapor amount

19. Different water vapor amount

20. [Control run] 100%terrain height
100%water vapor
100%terrain height
25% water vapor

21. At 8/8 2200 UTC [Control run] 100% terrain height 100% water vapor

22. 100%
Water vapor
50%
Water vapor
25%
Water vapor

23. Different terrain height of Taiwan

24. Different terrain height of Taiwan

25. [Control run] 100% terrain height
100% water vapor
0% terrain height
100% water vapor

26. “ The topography effect on the track is important
when the scale of the topography is greater
than the vortex Rmax. “
(Kuo et al., 2001)
From west to east of Taiwan → 140 km
Morakot’s Rmax → about 180 km
Discernible impact of Taiwan topography on Morakot’s track, but smaller than that of reducing moisture content (latent heating effect)

27. 100%
terrain height
50%
terrain height 0%
terrain height

28. No cloud microphysics

29. The speed of Morakot
km/hr

30. Conclusion heating effect was the another reason
As well as the steering flow, latent
heating effect was the another reason
that caused Typhoon Morakot’s slow
speed.

31. References
Tsuboki, K. and Sakakibara, A. 2002: Large-scale parallel computing of Cloud Resolving Storm Simulator. High Performance Computing,
Tsuboki, K. and Sakakibara, A. 2007: Numerical Prediction of High-Impact Weather Systems –The Textbook for Seventeenth IHP Training Course in Hydrospheric Atmospheric Research Center, Nagoya, Japan, 281 pp.
Kuo, H.-C., Williams, R.-T., Chen, J.-H., and Chen, Y.-L., 2001: Topographic effects on barotropic vortex motion: no mean flow. Journal of the Atmospheric Sciences, 58,
Ge, X., T. Li, S. Zhang, and M. Peng, 2010: What causes the extremely heavy rainfall in Taiwan during Typhoon Morakot (2009)? Atmos. Sci. Lett., 11,
Hong, C.-C., M.-Y. Lee, H.‐H. Hsu, and J.‐L. Kuo, 2010: Role of submonthly disturbance and 40–50 day ISO on the extreme rainfall event associated with Typhoon Morakot (2009) in Southern Taiwan. Geophy. Res. Lett., 37, 6pp.
周仲島, 李清勝, 鄭明典, 鳳雷, 于宜強, 2010: 莫拉克颱風綜觀環境與降雨特徵分析。莫拉克颱風科學報告, 1-26。

32. Thank you !