ast provide information about the time axis of the file and how
to relate the input time axis to the model time axis.  
default="null".
</pre>
        </div>
    </td>
    <td>char*256(30)</td>
    <td>shr_strdata_nml</td>
  </tr>
  <tr id="taxmode_tr">
    <td><a name="taxmode"></a>
        <img id="taxmode_arrow" src="./images/arrow_right.gif">
        <code class="varname">
          <a href="javascript:void(0)"
             onclick="toggleHelp('taxmode')">taxmode</a>
        </code>
        <div id="tax