| .add_derived_dt | Add derived temperature values for TMAX and TMIN |
| .drop_source_vars_dt | Remove source vars if not requested |
| read_cru_dt | Create a data.table of CRU CL v. 2.0 climatology elements |
| read_cru_rast | Create a terra SpatRaster object of CRU CL v. 2.0 climatology elements |