_VPINDEXENTRY_990" id="_VPINDEXENTRY_990"></a></p>
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<p align="left">With sigma coordinate data the vertical coordinate (or layer thickness) is available as a dependent variable and the Z axis of the sigma-encoded variables is layer number (the Z index). This is precisely analogous to method 3 of handling <a href="VERTICAL-PROFILES.html#_VPINDEXENTRY_979" title="8.3 VERTICAL PROFILES">collections of profiles</a>. The family of <a href="../variables-xpressions/XPRESSIONS.html#_VPID_115" title="3.2 EX