1 / 35

How Do Outer Spiral Rainband Affect Tropical Cyclone Structure and Intensity?

This study investigates the influence of outer spiral rainbands on the structure and intensity of tropical cyclones, focusing on the hydrostatic adjustment mechanism associated with diabatic heating. Experimental simulations show that modifying the heating and cooling rates in the rainbands affects the size of the eye and eyewall, indicating the weakening or strengthening of the storm. The results highlight the importance of understanding the role of outer spiral rainbands in tropical cyclone dynamics.

haroldw
Download Presentation

How Do Outer Spiral Rainband Affect Tropical Cyclone Structure and Intensity?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. How Do Outer Spiral Rainband Affect Tropical Cyclone Structure and Intensity? Reference : Wang, Y., 2009: How Do Outer Spiral Rainbands Affect Tropical Cyclone Structure and Intensity?. J. Atmos. Sci., 66, 1250–1273.

  2. CONTENTS Add your title INTRODUCTION Numerical model description Add your title TCM4 Add your title EXPERIMENTAL DESIGN Focus on the effect of the outer spiral rainbands on both the intensity and structure Add your title RESULTS Add your title CONCLUSIONS

  3. Introduction A long-standing issue on how outer spiral rainbands affect the structure and intensity of tropical cyclones Wang(2008b) found that interaction between the eyewall and outer spiral rainbands can be lead to a size increase of storm’s eye and eyewall and formation of annular hurricane. The particular focus is on the hydrostatic adjustment mechanism associated with diabatic heating in outer spiral rainbands and anvil clouds outside the inner core Inner spiral rainband

  4. Tropical Cyclone Model (TCM-4) • Capable of simulating the inner-core structure and intensity change of TC at nearly cloud resolving resolution(Wang 2007,2008)

  5. Tropical Cyclone Model (TCM-4) (Durran and Klemp,1983) 38 km solve sound and gravity waves problem Initially, with anaxisymmetric cyclonic vortex Maximum wind speed of 20m/s at a radius of 80 km at the surface f plane at 18oN in a quietscent environment Constant SST of 29oC No cumulus parameterization is considered in any domain Explicit treatment of mixing-phase cloud microphysics(Wang 2001) Fully compressible nonhydrostatic primitive equation model An unperturbed surface pressure of 1010 hPa.

  6. Experimental design After a spinup period of 48 h ,the modle TC develops a structure similar to real TCs. outer spiral rainbands are mainly driven by diabatic heating due to phase changes in the rainbands. The heating due to condensa-tion, depostion, and freezing while the cooling due to sublimation of ice particle ,evaporation of rain and cloud droplets ,melting of snow and guapel. The effect on TC intensity and structure can be evaluated by artifcially modifying the heating and cooling rate due to phase change .

  7. Experimental design

  8. Experimental design C120 H110 HC80,C80,H80 CTRL Inner Spiral Rainbands Outer Spiral Rainbands RMW

  9. Results 9h Weak tangential wind (K/h)

  10. Results >120 h Reducing the heating rate (H80) or increasing the cooling rate (C120) considerably decreased the size of eye and eyewall relative to CTRL. In contrast, reducing the cooling rate (C80) or increasing the heating rate (H110) considerably increased the size of eye and eyewall relative to CTRL. The heating is critical to the maintenance of outer spiral rain-bands, whereas cooling is destructive.

  11. 小結 • The stronger storms in HC80,H80, and C120 than in CTRL imply that outer spiral rainbands weaken a storm.

  12. Results 120 h Rain rate

  13. Results Transition period

  14. Results The extension of the warm core in the upper layer provides a more stable vertical structure . dry dry warm moist moist

  15. Results The correlation between surface Rain Rate and surface Pressure Drop

  16. Results 72-144 h time average

  17. Results z 9 h This is eyewall r Heating 120 h L Reduce pressure gradient force

  18. Conclusion I • The previous views on the effect of outer spiral rainbands on TC intensity : 1. Blocking of the boundary layer inflow 2. Subsidence forced by diabatic heating 3. cooling and drying of the boundary layer inflow due to convective downdraft • Internal atmospheric heating (cooling ) would tend to decrease(increase) surface pressure underneath the column. • As a result above, it would reduce the horizontal pressure gradient across RMW and increase the inner-core size of the .storm

  19. Conclusion II • Heating/cooling outside the inner core depends strongly on the relative humidity in the near-core environment. • Deep moist layer in the near-core environment may favor the development of large tropical cyclone ,annular hurricane, and concentric eyewall. • A relatively dry environment may favor small, compact tropical cyclones and is unfavorable to the formation of annular hurricane or concentric eyewall. • May and Holland(1999),PV generation in the outer spiral rainbands could contribute to the formation of a concentric eyewall.

  20. Thank You!

  21. C80

  22. H110

  23. H110

  24. content CONTENTS ADD YOUR TITLE ADD YOUR TITLE ADD YOUR TITLE ADD YOUR TITLE

  25. content CONTENTS ADD YOUR TITLE welcome to use these powerpoint templates, New Content design, 10 years experience

  26. CONTENTS Add your title welcome to use these powerpoint templates, New Content design, 10 years experience Add your title welcome to use these powerpoint templates, New Content design, 10 years experience

  27. CONTENTS Add your title Add your title Add your title welcome to use these powerpoint templates, New Content design, 10 years experience welcome to use these powerpoint templates, New Content design, 10 years experience welcome to use these powerpoint templates, New Content design, 10 years experience

  28. CONTENTS welcome to use these powerpoint templates, New Content design, 10 years experience welcome to use these powerpoint templates, New Content design, 10 years experience

  29. CONTENTS Add your title Add your title Add your title welcome to use these powerpoint templates, New Content design, 10 years experience welcome to use these powerpoint templates, New Content design, 10 years experience welcome to use these powerpoint templates, New Content design, 10 years experience

  30. CONTENTS welcome to use these powerpoint templates, New Content design, 10 years experience Add your title welcome to use these powerpoint templates, New Content design, 10 years experience

  31. CONTENTS welcome to use these powerpoint templates Add your title Add your title welcome to use these powerpoint templates Add your title Add your title welcome to use these powerpoint templates Add your title Add your title welcome to use these powerpoint templates Add your title Add your title welcome to use these powerpoint templates Add your title Add your title

  32. CONTENTS welcome to use these powerpoint templates welcome to use these powerpoint templates Add your text text welcome to use these powerpoint templates welcome to use these powerpoint templates Add your text Add your text Add your text

  33. Thank you!

  34. content CONTENTS • INTRODUCTION • TCM4 • EXPERIMENTAL DESIGH • RESULTS • DISCUSSION • CONCLUSIONS

More Related