40 years of continental moisture tracking using WAM-2layers

The WAM-2layers is an Eulerian moisture tracking numerical model. We used the Python version available on the GitHub repository (https://github.com/ruudvdent/WAM2layersPython). For a detailed description of the WAM-2layers, we refer the reader to van der Ent et al. (2013, 2014). Moisture tracking was conducted forward in time, focusing on the fate of evapotranspiration contributing to Terrestrial Moisture Recycling to calculate the amount of precipitation with continental origin. Our tracking experiment spans from 1979 to 2018. The model domain covers a global grid from 79.5ºN to 79.5ºS latitude. Calculations use data of specific humidity, zonal and meridional wind speeds at 24 pressure levels, surface pressure at 6-h intervals, and 3-h accumulated precipitation and evaporation, from the ERA-Interim reanalysis (Dee et al., 2011) on a 1.5º grid with 25,680 cells total (nx=240, ny=107). This set-up is based on previous studies indicating that it is adequate to track moisture spatially, both forward and backward in time and at regional and global scales.