The present study evaluates the impact of vortex initialization (VI) scheme within the NCMRWF Global Unified model (NCUM-G) for prediction of tropical cyclones (TCs) formed over Bay of Bengal (BoB). For this purpose, two numerical experiments such as control simulation (CNTL) without using VI scheme and VOTX simulation using the VI scheme in the NCUM-G are performed by considering four landfalling TCs formed over BoB basin during the year 2016–17. The results suggest that even though TCs are large synoptic systems, the introduction of VI scheme has a positive impact on the prediction of the location, movement, intensity and development of rain bands associated with the TCs. The initial vortex position and landfall position errors are reduced by ∼64% and ∼39% in VOTX simulations over CNTL, respectively. The mean track errors of all the four TCs are reasonably improved by ∼58% in VOTX over CNTL. The equitable threat score (ETS) and frequency bias are significantly improved in the VOTX for all the TC cases as compared to CNTL. Study results provide a positive proof of concept that the VI scheme within the NCUM-G can help to improve the simulation of track and intensity of TCs over BoB.

中文翻译：

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涡流初始化对使用 NCUM 模型预测孟加拉湾热带气旋的影响

本研究评估了 NCMRWF 全球统一模型 (NCUM-G) 中涡流初始化 (VI) 方案对预测在孟加拉湾 (BoB) 上空形成的热带气旋 (TC) 的影响。为此，通过考虑 2016-17 年在 BoB 盆地上空形成的四个登陆 TC，在 NCUM-G 中进行了两个数值实验，例如不使用 VI 方案的控制模拟（CNTL）和使用 VI 方案的 VOTX 模拟。结果表明，尽管台风是大型天气系统，但VI方案的引入对台风相关雨带的位置、运动、强度和发展的预测具有积极影响。在 CNTL 上的 VOTX 模拟中，初始涡旋位置和着陆位置误差分别减少了约 64% 和约 39%。在 VOTX 中，所有四个 TC 的平均轨道误差比 CNTL 合理地改善了约 58%。与 CNTL 相比，VOTX 中所有 TC 案例的公平威胁评分 (ETS) 和频率偏差都有显着改善。研究结果提供了一个积极的概念证明，即 NCUM-G 中的 VI 方案有助于改善对 BoB 上 TC 的轨迹和强度的模拟。