Index: palm/trunk/DOC/app/chapter_3.5.4.html
===================================================================
--- palm/trunk/DOC/app/chapter_3.5.4.html	(revision 337)
+++ palm/trunk/DOC/app/chapter_3.5.4.html	(revision 343)
@@ -275,5 +275,25 @@
 ENDIF</span><br style="font-family: monospace;"><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
 grid = 'zu'</span><br>&nbsp;<br>The <span style="font-family: monospace;">ELSE</span> case is
-only needed in case that output of time-averaged data is requested.<br><br><br></li><li>For
+only needed in case that output of time-averaged data is requested.<br><br>
+As a special case, xy cross section output can also be defined at one single level at height <span style="font-family: monospace;">k=nzb+1</span> on the u-grid. This features is useful for output of surface data (e.g. heat fluxes). In this case, the corresponding 2d data has to be resorted to the array <span style="font-family: monospace;">local_pf(i,j,nzb+1).</span> In addition to this, the grid in <a href="chapter_3.5.1.html#user_define_netcdf_grid"><span style="font-family: monospace;">user_define_netcdf_grid</span></a> as well as in <a href="chapter_3.5.1.html#user_data_output_2d"><span style="font-family: monospace;">user_data_output_2d</span></a> must be set to <span style="font-family: monospace;">grid = 'zu1'</span>.<br><br>
+<span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;CASE
+( 'u2_xy' )</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+IF ( av == 0 )&nbsp; THEN</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+DO&nbsp; i = nxl-1, nxr+1</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+DO&nbsp; j = nys-1, nyn+1</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+local_pf(i,j,nzb+1) = u2(j,i)</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+ENDDO</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+ENDDO</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+ELSE</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+DO&nbsp; i = nxl-1, nxr+1</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+DO&nbsp; j = nys-1, nyn+1</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+local_pf(i,j,nzb+1) = u2_av(j,i)</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+ENDDO</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+ENDDO</span><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+ENDIF</span><br style="font-family: monospace;"><br style="font-family: monospace;"><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+grid = 'zu1'</span><br><span style="font-family: monospace;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
+two_d = .TRUE.</span><br><br>
+Note that <span style="font-family: monospace;">two_d = .TRUE.</span> is necessary for output of a 2d data slice.<br><br>
+<br></li><li>For
 output of 3d volume data, the gridpoint data of the quantity has to be
 resorted to array <span style="font-family: monospace;">local_pf</span>
