added clarification to "sample exe input" file about requirement of matching cs tile space when using surface met forcing on cs grid (ldas_setup)

Author: gmao-rreichle

GEOSldas_App/ldas_setup

@@ -1504,6 +1504,11 @@ def _printExeInputKeys(rqdExeInpKeys):
     print ('#                                                          #')
     print ('#  Surface meteorological forcing time step is in seconds. #')
     print ('#                                                          #')
+    print ('#  NOTE:                                                   #')
+    print ('#    When forcing is on cube-sphere (CS) grid, must use:   #')
+    print ('#    - Model tile space (BCS) derived from same CS grid.   #')
+    print ('#    - Nearest-neighbor interpolation (MET_HINTERP: 0).    #')    
+    print ('#                                                          #')
     print ('#  For more information, see:                              #')
     print ('#    GEOSldas/doc/README.MetForcing_and_BCS.md             #')
     print ('#                                                          #')