ml2pl: docu update

doc/tex/mod/Intlevel

 @BeginModule
-@NewPage
 @Name      = Intlevel
 @Title     = Linear level interpolation
 @Section   = Interpolation
@@ -8,8 +7,7 @@
 @Operators = intlevel
 
 @BeginDescription
-This operator performs a linear vertical interpolation of non hybrid 
-3D variables.
+This operator performs a linear vertical interpolation of non hybrid 3D variables.
 @EndDescription
 @EndModule
 
@@ -27,8 +25,7 @@ FLOAT  Target levels
 
 
 @BeginExample
-To interpolate 3D variables on height levels to a new set of
-height levels use:
+To interpolate 3D variables on height levels to a new set of height levels use:
 @BeginVerbatim
    cdo intlevel,10,50,100,500,1000 ifile ofile
 @EndVerbatim

doc/tex/mod/Vertint

@@ -59,6 +59,21 @@ If set to 1 extrapolate missing values.
 
 @BeginNote
 The netCDF CF convention for vertical hybrid coordinates is not supported, yet!
+The vertical coordinate definition of a netCDF file has to follow the ECHAM convention.
+This means:
+@BeginItemize
+@Item = the dimension of the full level coordinate and the corresponding variable is called mlev,
+@Item = the dimension of the half level coordinate and the corresponding variable is called ilev (ilev must have one element more than mlev)
+@Item = the hybrid vertical coefficient a is given in units of Pa and called hyai (hyam for level midpoints)
+@Item = the hybrid vertical coefficient b is given in units of 1 and called hybi (hybm for level midpoints)
+@Item = the mlev variable has a borders attribute containing the character string 'ilev'
+@EndItemize
+
+Use the @mod{sinfo} command to test if your vertical coordinate system is recognized as hybrid system.
+
+In case this operator complains about not finding any data on hybrid model levels you may wish
+to use the @mod{setzaxis} command to generate a zaxis description which conforms to the ECHAM convention.
+See section "1.4 Z-axis description" for an example how to define a hybrid Z-axis.
 @EndNote
 
 

src/operator_help.h

@@ -3435,6 +3435,19 @@ static char *IntvertHelp[] = {
     "",
     "NOTE",
     "    The netCDF CF convention for vertical hybrid coordinates is not supported, yet!",
+    "    The vertical coordinate definition of a netCDF file has to follow the ECHAM convention.",
+    "    This means:",
+    "    - the dimension of the full level coordinate and the corresponding variable is called mlev,",
+    "    - the dimension of the half level coordinate and the corresponding variable is called ilev (ilev must have one element more than mlev)",
+    "    - the hybrid vertical coefficient a is given in units of Pa and called hyai (hyam for level midpoints)",
+    "    - the hybrid vertical coefficient b is given in units of 1 and called hybi (hybm for level midpoints)",
+    "    - the mlev variable has a borders attribute containing the character string 'ilev'",
+    "    ",
+    "    Use the sinfo command to test if your vertical coordinate system is recognized as hybrid system.",
+    "    ",
+    "    In case this operator complains about not finding any data on hybrid model levels you may wish",
+    "    to use the setzaxis command to generate a zaxis description which conforms to the ECHAM convention.",
+    "    See section \"1.4 Z-axis description\" for an example how to define a hybrid Z-axis.",
     NULL
 };
 
@@ -3446,8 +3459,7 @@ static char *IntlevelHelp[] = {
     "    intlevel,levels  ifile ofile",
     "",
     "DESCRIPTION",
-    "    This operator performs a linear vertical interpolation of non hybrid ",
-    "    3D variables.",
+    "    This operator performs a linear vertical interpolation of non hybrid 3D variables.",
     "",
     "PARAMETER",
     "    levels  FLOAT  Target levels",