A Dynamical Initialization Scheme for Real-Time Forecasts of Tropical Cyclones Using the WRF Model
A Dynamical Initialization Scheme for Real-Time Forecasts of Tropical Cyclones Using the WRF Model
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DOI：
10.1175/mwr-d-12-00077.1
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发表时间：
2013-03-01
影响因子：
3.2
通讯作者：
Wang, Yuqing
中科院分区：
文献类型：
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作者：
Cha, Dong-Hyun;Wang, Yuqing
为了改进热带气旋预报模式的初始条件，提出了一种基于循环运行的热带气旋动力初始化方案，并将其应用于西北太平洋热带气旋预报系统中。在该方案中，在初始预报时间之前重复运行一个6小时窗口的循环，以使TC涡旋轴对称分量旋转，直到模式TC强度与观测到的相当。其次是使用全球预报系统(GFS)预报作为侧边界条件的72小时预报。在DI方案中，在每个周期运行时使用谱推技术来减少大范围环境场中的偏差，并在最后一个周期运行后应用重定位方法来减小初始位置误差。为了证明建议的直接降水方案的有效性，在2010年和2011年对西北太平洋的13个热带气旋进行了69次有无直接降水的预报试验。热带气旋对TCS的路径和强度预报都显示出积极的影响，尽管它的总体技能很大程度上依赖于GFS预报的表现。与没有DI的预报相比，有DI的预报的位置和强度误差分别减少了10%和30%。结果表明，DI方案改善了初始TC涡旋结构和强度，并提供了暖物理自旋，产生了与预报模式一致的初始态，从而实现了更好的路径和强度预报。
To improve the initial conditions of tropical cyclone (TC) forecast models, a dynamical initialization (DI) scheme using cycle runs is developed and implemented into a real-time forecast system for northwest Pacific TCs based on the Weather Research and Forecasting (WRF) Model. In this scheme, cycle runs with a 6-h window before the initial forecast time are repeatedly conducted to spin up the axisymmetric component of the TC vortex until the model TC intensity is comparable to the observed. This is followed by a 72-h forecast using the Global Forecast System (GFS) prediction as lateral boundary conditions. In the DI scheme, the spectral nudging technique is employed during each cycle run to reduce bias in the large-scale environmental field, and the relocation method is applied after the last cycle run to reduce the initial position error. To demonstrate the effectiveness of the proposed DI scheme, 69 forecast experiments with and without the DI are conducted for 13 TCs over the northwest Pacific in 2010 and 2011. The DI shows positive effects on both track and intensity forecasts of TCs, although its overall skill depends strongly on the performance of the GFS forecasts. Compared to the forecasts without the DI, on average, forecasts with the DI reduce the position and intensity errors by 10% and 30%, respectively. The results demonstrate that the proposed DI scheme improves the initial TC vortex structure and intensity and provides warm physics spinup, producing initial states consistent with the forecast model, thus achieving improved track and intensity forecasts.