Geostrophic wind shear from CFSR v2 data for usage in WAsP

The change of the geostrophic wind speed has an impact on boundary layer mixing that can be important for microscale flow modelling for wind energy purposes. The WAsP software is often used for this purpose. This dataset contains the climatological geostrophic wind shear and direction over the whole global on a 0.5 degree grid that has been used in WAsP 12. It was obtained from the 6-hourly CFSR v2 reanalysis for the period 2011 to 2017 (see https://doi.org/10.5065/D61C1TXF). The omni-directional geostrophic wind shear vector denotes how much the geostrophic wind speed is changing over a certain vertical distance. Because we are interested in geostrophic wind shear changes that contribute to turbulent mixing in the atmospheric boundary layer, it was estimated by using the data on pressure levels from the pressure level closest to the surface up to 500 hPa above that heights.More details about the implementation of the model in the WAsP software and a validation can be found in the corresponding technical report:<br>Floors, R. R., Troen, I., &amp; Kelly, M. C. (2018). <i>Implementation of large-scale average geostrophic wind shear in WAsP12.1</i>. DTU Wind Energy. DTU Wind Energy E No. 0169<br>meandgdz_2010_2017_CFSRv3.nc: version with coordinate reference system in the coordinates for usage in GIS programs. NaN values at the poles are filled with 0.0, i.e. assuming barotropic atmosphere, which avoids crashes in the pywasp code. A single sector variable has been added, indicating that these values are valid for all wind direction, as opposed to other files that have values for each wind direction sector (for example: https://data.dtu.dk/articles/dataset/ERA5_atmospheric_stability_for_usage_in_WAsP_12_8/19576042). Naming conventions are in accordance with the windkit package (https://docs.wasp.dk/windkit/)

地转风速（geostrophic wind speed）的变化会对边界层混合（boundary layer mixing）产生影响，这对于用于风能领域的微尺度流动建模（microscale flow modelling）而言至关重要。WAsP软件常被应用于该类场景。
本数据集包含了WAsP 12中所使用的全球0.5度网格（0.5 degree grid）下的气候学地转风切变（climatological geostrophic wind shear）与风向数据，其源自2011至2017年间逐6小时的CFSR v2再分析资料（CFSR v2 reanalysis）（详见https://doi.org/10.5065/D61C1TXF）。
全向地转风切变矢量用于表征特定垂直距离内地转风速的变化幅度。鉴于我们关注的是对大气边界层（atmospheric boundary layer）湍流混合（turbulent mixing）有贡献的地转风切变变化，因此我们通过提取距地表最近的气压层（pressure levels）至该层以上500百帕（hPa）的气压层数据来估算该切变。
有关WAsP软件中模型的实现细节与验证方法，可参阅对应技术报告：<br>Floors, R. R., Troen, I., & Kelly, M. C. (2018). 《WAsP12.1中大尺度平均地转风切变的实现》，丹麦技术大学风能研究所（DTU Wind Energy），DTU Wind Energy E No. 0169
meandgdz_2010_2017_CFSRv3.nc：该版本的坐标参考系已适配坐标格式，可直接用于地理信息系统（GIS）程序。极地的非数值（NaN，Not a Number）值已被填充为0.0，即假设为正压大气，此举可避免pywasp代码运行崩溃。此外，本数据集新增了单一扇区变量，表明这些数值适用于所有风向，而其他文件则仅针对各风向扇区提供对应数值（例如：https://data.dtu.dk/articles/dataset/ERA5_atmospheric_stability_for_usage_in_WAsP_12_8/19576042）。
本数据集的命名规范符合windkit工具包（windkit package）的要求（详见https://docs.wasp.dk/windkit/）