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A distributed wind downscaling technique for wave climate modeling under future scenarios
Ocean Modelling ( IF 3.2 ) Pub Date : 2020-01-01 , DOI: 10.1016/j.ocemod.2019.101513
Mohamad Javad Alizadeh , Mohamad Reza Kavianpour , Bahareh Kamranzad , Amir Etemad-Shahidi

Abstract The aim of this study is to develop a Weibull-based distributed downscaling technique for wind field as forcing for the wave models to investigate the wave climate under future scenarios. For this purpose, the statistical downscaling approach modifies Weibull distribution parameters of the global circulation model wind speeds based on the corresponding features of wind data of ECMWF (European Center for Medium-Range Weather Forecasts). The proposed technique has the advantage of modifying the wind components in each grid point based on the corresponding values in the same grid point of ECMWF wind field. Hence, it is superior to other existing models due to considering the spatial variation. The previous models using inverse distance weighting suffer from heterogeneity and ignoring spatial variation in areas with high gradient of wind speed. Moreover, the Weibull-based technique outperforms the existing statistical downscaling techniques in terms of accuracy. Prior to investigate future distribution of wave characteristics, performance of the selected GCM was evaluated and compared against the corresponding models obtained from the available regional climate models. Future projections of wind fields (RCP4.5, RCP8.5) were downscaled for the period of 2081 to 2100 with the proposed model as driving force for wave modeling in the Persian Gulf. To investigate the impacts of climate change on wave characteristics, results of the wave simulations from a third generation wave model (SWAN) for future scenarios are compared with those of the historical period (1981–2000) in monthly, seasonal, and annual scales. Generally, for RCP8.5, the results indicate a decrease in future significant wave height and peak wave period about 15% and 5%, respectively. However, the change of wave direction is marginal. Moreover, wave models forced with RCP4.5 wind data provide slightly higher average values in terms of wave height and peak wave period compared to those of RCP8.5.

中文翻译:

未来情景下波浪气候建模的分布式风降尺度技术

摘要 本研究的目的是开发一种基于威布尔的风场分布式降尺度技术,作为波浪模型研究未来情景下的波浪气候的动力。为此,统计降尺度方法根据ECMWF(欧洲中期天气预报中心)的风数据的相应特征修改了全球环流模型风速的威布尔分布参数。所提出的技术具有基于ECMWF风场相同网格点中的相应值修改每个网格点中的风分量的优点。因此,由于考虑了空间变化,它优于其他现有模型。以前使用逆距离加权的模型存在异质性,并且忽略了高风速梯度区域的空间变化。此外,基于 Weibull 的技术在准确性方面优于现有的统计降尺度技术。在调查波浪特征的未来分布之前,对所选 GCM 的性能进行了评估,并将其与从可用区域气候模型中获得的相应模型进行了比较。在 2081 年至 2100 年期间,风场(RCP4.5、RCP8.5)的未来预测被缩小,所提出的模型作为波斯湾波浪建模的驱动力。为了调查气候变化对波浪特征的影响,将来自第三代波浪模型 (SWAN) 的未来情景的波浪模拟结果与历史时期(1981-2000 年)的月度、季节和年度尺度进行比较。一般来说,对于RCP8.5,结果表明未来显着波高和峰值波周期分别减少约15%和5%。然而,波浪方向的变化是微不足道的。此外,与 RCP8.5 相比,使用 RCP4.5 风数据强制的波浪模型在波高和波峰周期方面提供了略高的平均值。
更新日期:2020-01-01
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