Samplings of available levels (see <a href="http://dss.ucar.edu/datasets/ds353.4/inventories/list_A_mandatory_level_checks/">level analysis</a>) shows</font>
<ul><ul><ul><table cellpadding="1" cellspacing="1" border="0">
<tr><td align="right">only  </td><td align="right">. of all raobs</td></tr>
<tr><td align="right">about </td><td align="right">         reach</td></tr>
<tr><td align="right"> 50%  </td><td align="right">          20mb</td></tr>
<tr><td align="right"> 25%  </td><td align="right">          10mb</td></tr>
<tr><td align="right">  5%  </td><td align="right">           7mb</td></tr>
<tr><td align="right">  2%  </td><td align="right">           5mb</td></tr>
<tr><td align="right"> <1%  </td><td align="right">           3mb</td></tr>
</table>
<a href="http://dss.ucar.edu/datasets/ds353.4/docs/more.summary.html#STRAT" >stratosphere comments</a></ul></ul></ul>
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ds353.4_levels.