HYSPLIT计算水汽轨迹来源

推开世界的门

请问各位大佬，在Run HYSPLIT中，将ERA5的数据转化为HYSPLIT所能识别的数据时。Invariant (geop)这个是什么意思，该输入什么变量呀。
Converts multi-time-period ECMwF ERA-40 or -Interim GRIB-1 files to ARL format. Files are available from http://apps.ecmwf.int/datasets/. The following fields are required: 3D (geop, temp, uvel, vvel, wvel, rh); 2D (2m temp, 1Om UV);Invariant (geop). These are designated by the three different input files.