[pyicon_dwd] Use ERA5 data as reference for atmospheric plots: part 2

    ('part 2': all atmospheric plots created by qp_compare_atm_dwd.py)

    More details:

    *) pyicon/quickplots/qp_compare_atm_dwd.py is updated so that ERA5
       is used as reference for bias plots. Many new plots are added
       as compared to the previous case, where only a limited set
       of variables were available from ERA Interim the format that
       was eatable by pyicon.

    *) pyicon/quickplots/pyicon_quickplots.py is updated in order
       to show ERA5 data also in times series plots for the atmosphere.
       The changes are done under 'if use_tave_int_for_ts:' and
       'if fpath_ref_data_atm != ''' statements so that it does not
       change anything for ocean plots.

    *) tools/run_qp_compare_atm_dwd.sh is updated by the path and
       file name of the ERA5 reference data.

tools/run_qp_compare_atm_dwd.sh

@@ -47,7 +47,7 @@ gnameu = gname.split('_')[0].upper()
 fpath_tgrid         = path_grid + gname+'_tgrid.nc'
 fpath_tgrid_atm     = path_grid_atm + gname_atm+'_tgrid.nc'
 fpath_ref_data_oce  = path_grid + 'ts_phc3.0_annual_icon_grid_0043_R02B04_G_L40.nc'
-fpath_ref_data_atm  = path_grid_atm + 'pyicon_prepare_era.nc'
+fpath_ref_data_atm  = path_grid_atm + 'era5_pyicon_2000-2010_1.5x1.5deg.nc'
 fpath_fx            = path_grid + 'oce_fx.19600102T000000Z.nc'
 
 # --- nc file prefixes ocean