Weather Research and Forecasting (WRF) model version 4.1.3 is configured in the present study to understand the impact of microphysical parameterization schemes on the track and intensity of extremely severe cyclonic storm (ESCS) “Fani” that occurred during 26 April to 4 May 2019 in the Bay of Bengal. The model is customized with six different microphysical parameterization schemes along with Kain–Fritsch cumulus for convection and the Yonsei University planetary boundary-layer scheme for computation of heat and moisture transport. The simulations are conducted at 27-km horizontal resolution with 41 levels in the vertical for 150 h (00UTC 28 April to 06UTC 4 May 2019). Model-simulated features such as the track, track error, minimum central sea-level pressure (MSLP), maximum sustained surface wind (MSW), and precipitation are validated against India Meteorological Department (IMD) and Tropical Rainfall Measuring Mission (TRMM) observation data. Although all the schemes predict track patterns similar to observation, the MP3 scheme shows the least track error even after landfall, and its track length is maximum in comparison with other schemes, albeit less than the observed track. The MP3 scheme exhibits a better track for “Fani,” followed by MP14. The lowest mean direct position error (along-track error) of 85 km (68.5 km) is noted for the MP3 scheme, followed by 112.5 km (82.3 km) for the MP8 scheme. Analysis of the MSLP and MSW using the t -test suggests that the MP2 scheme has better forecast ability, followed by MP6. Analysis of the quantitative/spatial matching of the rainfall forecasts and TRMM observations using the Method for Object-Based Diagnostic Evaluation (MODE) tool suggests that the MP8 (MP14) scheme is capable of simulating the rainfall beyond (up to) 48 h. Analysis of the zonal cross-section of horizontal and vertical winds shows that intense convection is well simulated by the MP2, MP3, and MP4 schemes during the change of intensity from cyclonic storm to severe cyclonic storm (SCS), by MP6 and MP14 from SCS to very severe cyclonic storm (VSCS) and from VSCS to ESCS, and by MP8 at ESCS level. All the schemes can capture the eyewall and simulate the westerly that allowed the system to move north-northeastwards. The synoptic flow at different pressure levels is reproduced by all the schemes. However, assessing the impact of the microphysics parameterizations on the synoptic flow of “Fani” at low resolution was difficult. Analysis of Qc and Qr indicates definite impacts of the microphysical parameterizations on the vertical structure of “Fani” in producing rainfall. The MP3 scheme exhibits a better cloud pattern up to upper troposphere level, followed by the MP2 scheme. Analysis of the latent heat flux predicted using the different microphysics schemes suggests that the latent heat flux release at VSCS intensity level or above contributes to further intensification of the TC, and this feature is very well simulated by the MP2 scheme.

中文翻译：

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WRF 参数化方案对极强气旋风暴“Fani”的轨迹和强度的影响

本研究中配置了天气研究和预测 (WRF) 模型版本 4.1.3，以了解微物理参数化方案对 4 月 26 日至 5 月 4 日期间发生的极强气旋风暴 (ESCS)“Fani”的轨迹和强度的影响2019 年在孟加拉湾。该模型使用六种不同的微物理参数化方案以及用于对流的 Kain-Fritsch 积云和用于计算热量和水分传输的延世大学行星边界层方案进行定制。模拟以 27 公里的水平分辨率进行，垂直方向为 41 个级别，持续 150 小时（2019 年 4 月 28 日 00UTC 至 2019 年 5 月 4 日 06UTC）。模型模拟特征，例如航迹、航迹误差、最小中央海平面压力 (MSLP)、最大持续表面风 (MSW)、和降水根据印度气象部门 (IMD) 和热带降雨测量任务 (TRMM) 观测数据进行验证。尽管所有方案都预测了类似于观测的航迹模式，但 MP3 方案即使在登陆后也显示出最小的航迹误差，与其他方案相比，其航迹长度最大，尽管小于观测航迹。MP3 方案为“Fani”展示了更好的曲目，其次是 MP14。MP3 方案的最低平均直接位置误差（沿轨道误差）为 85 公里（68.5 公里），其次是 MP8 方案的 112.5 公里（82.3 公里）。使用 t 检验分析 MSLP 和 MSW 表明 MP2 方案具有更好的预测能力，其次是 MP6。使用基于对象的诊断评估方法 (MODE) 工具对降雨预报和 TRMM 观测的定量/空间匹配进行分析表明 MP8 (MP14) 方案能够模拟超过（最多）48 小时的降雨。水平和垂直风的纬向截面分析表明，在从气旋风暴到强气旋风暴（SCS）的强度变化过程中，MP2、MP3和MP4方案可以很好地模拟强对流，SCS的MP6和MP14方案可以很好地模拟强对流。到非常严重的气旋风暴 (VSCS) 和从 VSCS 到 ESCS，以及在 ESCS 级别通过 MP8。所有方案都可以捕获眼墙并模拟允许系统向北-东北移动的西风。所有方案都再现了不同压力水平下的天气流。然而，在低分辨率下评估微物理参数化对“Fani”天气流的影响很困难。Qc 和Qr 的分析表明微物理参数化对产生降雨的“Fani”垂直结构的影响。MP3 方案在对流层上层表现出更好的云模式，其次是 MP2 方案。对使用不同微物理方案预测的潜热通量的分析表明，在 VSCS 强度水平或以上的潜热通量释放有助于 TC 的进一步增强，MP2 方案很好地模拟了这一特征。Qc 和Qr 的分析表明微物理参数化对产生降雨的“Fani”垂直结构有明确的影响。MP3 方案在对流层上层表现出更好的云模式，其次是 MP2 方案。对使用不同微物理方案预测的潜热通量的分析表明，在 VSCS 强度水平或以上的潜热通量释放有助于 TC 的进一步增强，MP2 方案很好地模拟了这一特征。Qc 和Qr 的分析表明微物理参数化对产生降雨的“Fani”垂直结构的影响是明确的。MP3 方案在对流层上层表现出更好的云模式，其次是 MP2 方案。对使用不同微物理方案预测的潜热通量的分析表明，在 VSCS 强度水平或以上的潜热通量释放有助于 TC 的进一步增强，MP2 方案很好地模拟了这一特征。