Docu update.

doc/tex/mod/Vertint

@@ -10,7 +10,7 @@
 @BeginDescription
 Interpolate 3D variables on hybrid sigma pressure level to pressure or height levels.
 The input file should contain the log. surface pressure or the surface pressure.
-To interpolate the temperature, the surface geopotential is also needed.
+To extrapolate the temperature, the surface geopotential is also needed.
 The pressure, temperature, and surface geopotential are identified by their GRIB1 code number
 or NetCDF CF standard name.
 Supported parameter tables are: WMO standard table number 2 and ECMWF local table number 128.

src/operator_help.h

@@ -3881,7 +3881,7 @@ static const char *VertintmlHelp[] = {
     "DESCRIPTION",
     "    Interpolate 3D variables on hybrid sigma pressure level to pressure or height levels.",
     "    The input file should contain the log. surface pressure or the surface pressure.",
-    "    To interpolate the temperature, the surface geopotential is also needed.",
+    "    To extrapolate the temperature, the surface geopotential is also needed.",
     "    The pressure, temperature, and surface geopotential are identified by their GRIB1 code number",
     "    or NetCDF CF standard name.",
     "    Supported parameter tables are: WMO standard table number 2 and ECMWF local table number 128.",