Monthly and Annual contour lines of the zero and the positive maximum of the Wind Stress Curl over Western North Atlantic during 1980-2019 and the Gulf Stream path during 1993-2019.

This dataset includes multiple fields: (i) files for monthly and annual fields for the max curl line and the zero curl line at 0.1 degree longitudinal resolutions; (ii) files for monthly and annual GS path obtained from Altimetry and originally processed by Andres (2016) at 0.1 degree longitudinal resolution. The maximum curl line (MCL) and the zero curl line (ZCL) calculations are briefly described here and are based on the original wind data (at 1.25 x 1.25 degree) provided by the Japanese reanalysis (JRA-55; Kobayashi et al., 2015) and available at https://zenodo.org/record/8200832 (Gifford et al. 2023). For details see Gifford, 2023. The wind stress curl (WSC) fields used for the MCL and ZCL calculations extend from 80W to 45W and 30N to 45N at the 1.25 by 1.25-degree resolution. The MCL is defined as the maximum WSC values greater than zero within the domain per 1.25 degree longitude. As such, it is a function of longitude and is not a constant WSC value unlike the zero contour. High wind stress curl values that occurred near the coast were not included within this calculation. After MCL at the 1.25 resolution was obtained the line was smoothed with a gaussian smoothing and interpolated on to a 0.1 longitudinal resolution. The smoothed MCL lines at 0.1 degree resolution are provided in separate files for monthly and annual averages (2 files). Similarly, 2 other files (monthly and annual) are provided for the ZCL. Like the MCL, the ZCL is a line derived from 1.25 degree longitude throughout the domain under the condition that it's the line of zero WSC. The ZCL is constant at 0 and does not vary spatially like the MCL. If there are more than one location of zero curl for a given longitude the first location south of the MCL is selected. Similar to the MCL, the ZCL was smoothed with a gaussian smoothing and interpolated on to a 0.1 longitudinal resolution. The above files span the years from 1980 through 2019. So, the monthly files have 480 months starting January 1980, and the annual files have 40 years of data. The files are organized with each row being a new time step and each column being a different longitude. Therefore, the monthly MCL and ZCL files are each 480 x 351 for the 0.1 resolution data. Similarly, the annual files are 40 x 351 for the 0.1 degree resolution data. <strong>Note that the monthly MCLs and ZCLs are obtained from the monthly wind-stress curl fields. The annual MCLs and ZCLs are obtained from the annual wind-stress curl fields.</strong> Since the monthly curl fields preserves more atmospheric mesoscales than the annual curl fields, the 12-month average of the monthly MCLs and ZCLs will not match with the annual MCLs and ZCLs derived from the annual curl field. The annual MCLs and ZCLs provided here are obtained from the annual curl fields and representative metrics of the wind forcing on an annual time-scale. Furthermore, the monthly Gulf Stream axis path (25 cm isoheight from Altimeter, reprocessed by Andres (2016) technique) from 1993 through 2019 have been made available here. A total of 324 monthly paths of the Gulf Stream are tabulated. In addition, the annual GS paths for these 27 years (1993-2019) of altimetry era have been put together for ease of use. The monthly Gulf Stream paths have been resampled and reprocessed for uniqueness at every 0.1 degree longitude from 75W to 50W and smoothed with a 100 km (10 point) running average via matlab. The uniqueness has been achieved by using Consolidator algorithm (D’Errico, 2023). Each monthly or annual GS path has 251 points between 75W to 50W at 0.1 degree resolution.本数据集包含多个数据字段：(i) 0.1度经度分辨率下的最大涡度线（max curl line, MCL）与零涡度线（zero curl line, ZCL）的月度与年度场文件；(ii) 0.1度经度分辨率下，由卫星测高数据（Altimetry）获取、Andres(2016)原始处理得到的墨西哥湾流（Gulf Stream, GS）路径月度与年度文件。 最大涡度线（MCL）与零涡度线（ZCL）的计算方法简述如下：其基于日本再分析数据（JRA-55; Kobayashi等，2015）提供的1.25×1.25度分辨率原始风场数据，相关数据集可在https://zenodo.org/record/8200832获取（Gifford等，2023），详细细节参见Gifford, 2023。用于MCL与ZCL计算的风应力涡度（wind stress curl, WSC）场，覆盖范围为西经80°至西经45°、北纬30°至北纬45°，分辨率为1.25×1.25度。MCL被定义为研究区域内，每1.25度经度范围内大于0的最大WSC值。因此，MCL为经度的函数，并不像零等值线那样为恒定的WSC值。本次计算未纳入海岸附近的高风应力涡度值。在获取1.25度分辨率的MCL后，通过高斯平滑对该线进行处理，并插值至0.1度经度分辨率。0.1度分辨率下的月度与年度平滑MCL线，分别存储于两个独立文件中。同理，ZCL也对应两个文件（月度与年度）。与MCL类似，ZCL是在整个研究区域内，由1.25度经度推导得到的零WSC等值线，其数值固定为0，并不像MCL那样存在空间变化。若某一经度存在多个零涡度位置，则选取MCL以南的首个位置。与MCL处理流程一致，ZCL也经过高斯平滑并插值至0.1度经度分辨率。 上述文件的时间跨度为1980年至2019年。其中月度文件包含1980年1月起的480个月份数据，年度文件则包含40年的数据集。文件组织格式为：每行对应一个时间步长，每列对应不同经度。因此，0.1度分辨率下的月度MCL与ZCL文件尺寸均为480×351；同理，年度文件尺寸为40×351。 **请注意：月度MCL与ZCL由月度风应力涡度场推导得到，而年度MCL与ZCL则基于年度风应力涡度场计算。**由于月度涡度场相较于年度涡度场保留了更多大气中尺度特征，因此月度MCL与ZCL的12个月平均值，与由年度涡度场推导得到的年度MCL、ZCL并不一致。本数据集提供的年度MCL与ZCL由年度涡度场得到，可代表年尺度上海洋风强迫的典型特征。 此外，本数据集还提供了1993年至2019年的月度墨西哥湾流轴路径数据（来自卫星测高仪的25厘米等高度线，采用Andres(2016)的方法重新处理），总计包含324条月度湾流路径。为便于使用，同时整理了测高时代（1993-2019年）共27年的年度GS路径数据。月度墨西哥湾流路径已通过Consolidator算法（D’Errico, 2023）实现唯一性处理，并重采样至西经75°至西经50°间的0.1度经度间隔，同时采用Matlab实现100 km（10点）滑动平均平滑。每条月度或年度GS路径在西经75°至西经50°间包含251个0.1度分辨率采样点。