Extended Abstract (268K)10D.3
Sensitivity of tropical cyclone intensification and intensity to cloud microphysics parameterization
Yuqing Wang, Univ. of Hawaii, Honolulu, HI
It has been long known that cloud microphysics can have a significant impact on the simulations of precipitation, but there have been few studies that have investigated the effect of cloud microphysics on tropical cyclones. In the most advanced simulation of tropical cyclones by numerical models, the use of explicit cloud microphysics becomes more and more attractive with cumulus parameterization bypassed at very high resolutions. In this study, the sensitivity of the simulated tropical cyclone structure and intensity to the choice and details of cloud microphysics parameterization is investigated using the tropical cyclone model TCM3 developed by the author previously. It is shown that the structure, intensification rate and final intensity of the simulated tropical cyclone are all sensitive to the details of the cloud microphysics parameterizations in the model. This sensitivity is found to stem from the differences in the simulated stratiform clouds outside the eyewall by various mixed-ice phase parameterizations. The melting of snow and graupel in the stratiform clouds is a major process in initiating the spiral rainbands outside the eyewall by producing strong downdrafts. The evaporation of rain also plays a role but is of secondary importance. Downdrafts can also be generated near the lateral boundaries of deep clouds either in the eyewall or in the convective rainbands due to the melting of ice species and evaporation of both cloud water and raindrops, being detrained from the deep clouds. Rainbands affect the structure, intensification and final intensity of the model tropical cyclone through two major processes: barrier effect on the inflow to the eyewall and low equivalent potential temperature air in the boundary layer related to strong downdrafts.
Session 10D, Tropical Cyclone Simulation: Parameterizations and Numerics (Parallel with Sessions 10A, 10B, and 10C)
Wednesday, 1 May 2002, 2:00 PM-3:30 PM
Previous paper Next paper