CHARACTERISTIC ANALYSIS OF DIURNAL CYCLE OF TYPHOON CHANCHU'S (0601) INTENSITY
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摘要: 利用非静力中尺度模式WRF模拟了台风Chanchu（0601），模式再现了台风Chanchu的路径、强度及结构。利用模式资料分析了台风Chanchu发展增强过程中其流出层和流入层风速的日变化特征、造成该日变化特征的机制及其对台风强度的影响。分析表明：台风Chanchu流出层和流入层的风速均存在显著的日变化特征，表现在低层径向入流和高层径向出流在夜间至清晨明显增强，在白天增加缓慢；切向风变化趋势同径向风类似，位相较径向风落后约6 h。通过对比夜间和白天云顶温度（CTT）和垂直速度频率（CFADS）的分布，发现夜间对流较白天更加活跃，这与夜间云顶冷却所导致的静力稳定度降低有关。利用切向风倾向方程进行收支分析，结果显示太阳辐射日变化通过调节对流日变化，引起高低层径向气流的日变化，进而造成切向风速的日变化，从而影响台风强度，在一定程度上揭示了日变化对台风强度变化的指示意义。Abstract: The non-hydrostatic mesoscale model WRF is employed to perform a simulation of Chanchu (0601), which reproduces well the track, intensity and basic structures. In this paper, data from the numerical simulations of WRF model on typhoon Chanchu (0601) is used to investigate the diurnal variation characteristics of the wind velocity in the outflow and inflow layers of the typhoon, as well as the mechanism of the diurnal variation and its influence on the typhoon intensity during the stage of its development. Results demonstrate that a clear diurnal oscillation signal of wind speed exists in both the outflow and inflow layer of Chanchu with a maximum increase in the night to early morning, and a slow increase in the daytime. The variation trend of tangential wind is similar to that of radial wind, but lags behind the radial wind in phase by approximately 6 hours. By comparing the distribution of cloud top temperature and vertical velocity frequency at both night and daytime, we find that the strong convective activities tend to occur at night rather than during the day, which is related to the decrease of static stability caused by cloud top cooling at night. Momentum budget analysis is performed based on the tangential tendency equation. It is indicated that the diurnal cycle of solar radiation can produce diurnal variation of radial airflow by adjusting the convective diurnal variation, causing the diurnal variation of tangential velocity, thus affecting the intensity of typhoon, which reveals to a certain extent the significance of the diurnal cycle for typhoon intensity variation.
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Key words:
- typhoon /
- wind speed /
- diurnal cycle /
- radiation /
- convection /
- static stability /
- intensity
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图 1 模式嵌套网格示意图
A、B、C、D分别为分辨率54 km、18 km、6 km、2 km的嵌套网格，叠加的矢量场为5月10日0000 UTC时刻的700 hPa水平风场；A、B、C位置固定，D跟随TC中心沿D1到D2移动，TC标记处代表TC初始位置。
图 3 12月11时（a，e）、13日11时（b，f）、14日11时（c，g）和15日00时（d，h）6 km分辨率的WRF模式资料在700 hPa的雷达反射率(dBz)(a~d)和85 GHZ亮温(K)(e~h)水平分布图
图 4 去除风场随台风强度变化趋势后，流出层距台风中心100~280 km区域平均的逐6 h变化的径向风(实线)和切向风(虚线)随时间的演变
横坐标为地方时，13-14表示13日14时，以此类推。
图 7 去除风场随台风强度变化趋势后，流入层距台风中心50~280 km区域平均的逐6 h变化的径向风(实线)和切向风(虚线)随时间的演变
横坐标为地方时，13-14表示13日14时，以此类推。
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