17:15 〜 18:45
[AAS06-P03] Impact of an upper-level Coriolis parameter on tropical cyclone intensification by using an axisymmetric model
キーワード：CM1、慣性安定度、流出層、台風
The Coriolis force is a necessary condition of formation and intensification for a tropical cyclone (TC). Nevertheless, as indicated by there are the peaks of TC intensity mainly over the lower latitude, the large Coriolis parameter does not necessarily make TCs stronger. Previous studies suggest that the large inertial stability made by the large Coriolis parameter weakens the upper-level outflow. However, recent study shows that the upper-level outflow is a passive result of intensification. Here, I examine the effect of upper-level wind change on the TC intensification.
The present study carried out the axisymmetric idealized simulations using the vertical profiles of the Coriolis parameter to separate influence from the lower-level structure, such as boundary layer process. I used the axisymmetric version of the Cloud Model 1 (CM1) version 21.0 (cm1r21.0). The model domain was 910 km in radial and 25 km in vertical direction. The radial grid size was 2 km inside the 160 km radius and stretched outward to the 10 km spacings at the lateral edge. The interval of the vertical layers was increased linearly from was 50 m at the surface to 500 m at the 5.5 km height, and then fixed to the top. The physical processes were set as follows. I used the CM1 simple scheme for the planetary boundary layer process. The horizontal and asymptotic vertical turbulence scale were 750 m and 100 m, respectively. The water only scheme was used for the microphysics process. The radiative cooling was parameterized by the relaxation term which was capped at 2 K/day. The Rayleigh damping layer was applied above 20 km height. I set the modified Rankine vortex and thermodynamics fields for the initial conditions. These initial conditions gave the tropopause height of 15 km.
The results indicated that the smaller Coriolis parameter above 15 km height hastened the rapid intensification onset and widened the TC size. The warm anomaly above 10 km height in the eye wall explained quite well the surface pressure change. From the thermal wind relationship, the vertical tangential wind shear is responsible for the warm core structure. The upper-level Coriolis parameter has a potential to affect the TC intensification through the warm core development. These results are also compared with the recent similar study.
The present study carried out the axisymmetric idealized simulations using the vertical profiles of the Coriolis parameter to separate influence from the lower-level structure, such as boundary layer process. I used the axisymmetric version of the Cloud Model 1 (CM1) version 21.0 (cm1r21.0). The model domain was 910 km in radial and 25 km in vertical direction. The radial grid size was 2 km inside the 160 km radius and stretched outward to the 10 km spacings at the lateral edge. The interval of the vertical layers was increased linearly from was 50 m at the surface to 500 m at the 5.5 km height, and then fixed to the top. The physical processes were set as follows. I used the CM1 simple scheme for the planetary boundary layer process. The horizontal and asymptotic vertical turbulence scale were 750 m and 100 m, respectively. The water only scheme was used for the microphysics process. The radiative cooling was parameterized by the relaxation term which was capped at 2 K/day. The Rayleigh damping layer was applied above 20 km height. I set the modified Rankine vortex and thermodynamics fields for the initial conditions. These initial conditions gave the tropopause height of 15 km.
The results indicated that the smaller Coriolis parameter above 15 km height hastened the rapid intensification onset and widened the TC size. The warm anomaly above 10 km height in the eye wall explained quite well the surface pressure change. From the thermal wind relationship, the vertical tangential wind shear is responsible for the warm core structure. The upper-level Coriolis parameter has a potential to affect the TC intensification through the warm core development. These results are also compared with the recent similar study.