<!--Copyright (C) 1988-2005 by the Institute of Global Environment and Society (IGES). See file COPYRIGHT for more information.--> <html> <head> <title>GrADS Function: fndlvl</title> </head> <body text="#000000" bgcolor="e0f0ff"> <h2><b>fndlvl()</b></h2> <p> <code>fndlvl (<i>expr, expr_to_find, lev1, lev2</i>)</code> <p> Given two gridded variables, <code><i>expr</i></code> and <code><i>expr_to_find</i></code>, this function finds the first vertical level at which the <code><i>expr_to_find</i></code> value occurs in <code><i>expr</i></code>. <code><i>lev1</i></code> and <code><i>lev2</i></code> specify the range of levels over which to search. The result is a grid of pressure values. <p> <h3>Usage Notes</h3> <ol> <li>The dimensions of <code><i>expr</i></code> and <code><i>expr_to_find</i></code>   must match. </ol> <p> <h3>Examples </h3> <p> <ol> <li>This example finds the pressure levels of the 240 degree isotherm: <p> <ul><code>d fndlvl (t, const(t,240), lev=1000, lev=100)</code></ul> <p> <li>The <code><i>expr_to_find</i></code> doesn't have to be a constant; it can change with location. This example returns the pressure level of the tropopause, given the variable <code>'ttrop'</code> that contains the temperature at the tropopause: <p> <ul><code>d fndlvl (t, ttrop, lev=1000, lev=100)</code></ul> <p> <li>This example illustrates the limitations of <code>fndlvl</code>. It returns the level of the surface pressure variable <code>psfc</code> in the coordinate system of <code>lev</code>, a GrADS <a href="variable.html">pre-defined variable</a>. <p> <ul> <code>d fndlvl (lev, psfc, lev=1000, lev=100)</code> </ul> <p> The display should be exactly the same as <code>psfc</code> except in locations where <code>psfc</code> is greater than 1000 mb, the maximum value of <code>lev<code>. </code></code></ol> </body> </html>