[Dart-dev] <P>Jump/ Revision: 12385

Thu Feb 1 14:45:43 MST 2018

nancy at ucar.edu
2018-02-01 14:45:43 -0700 (Thu, 01 Feb 2018)
181
created missing documentation for the quality control module.
the interface section is slightly incomplete, but we hope to
generate the exact interfaces via doxygen sometime soon.




Added: DART/branches/rma_trunk/assimilation_code/modules/assimilation/quality_control_mod.html
===================================================================

--- DART/branches/rma_trunk/assimilation_code/modules/assimilation/quality_control_mod.html	                        (rev 0)
+++ DART/branches/rma_trunk/assimilation_code/modules/assimilation/quality_control_mod.html	2018-02-01 21:45:43 UTC (rev 12385)
@@ -0,0 +1,485 @@
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
+          "http://www.w3.org/TR/html4/strict.dtd">
+<HTML>
+<HEAD>
+<TITLE>module quality_control_mod</TITLE>
+<link rel="stylesheet" type="text/css" href="../../../documentation/html/doc.css" />
+<link href="../../../documentation/images/dart.ico" rel="shortcut icon" />
+</HEAD>
+<BODY>
+<A NAME="TOP"></A>
+
+<H1>MODULE quality_control_mod</H1>
+
+<table border=0 summary="" cellpadding=5>
+<tr>
+    <td valign=middle>
+    <img src="../../../documentation/images/Dartboard7.png" alt="DART project logo" height=70 />
+    </td>
+    <td>
+       <P>Jump to <a href="../../../documentation/index.html">DART Documentation Main Index</a><br />
+          <small><small>version information for this file: <br />
+          <!-- version tag follows, do not edit -->
+          $Id$</small></small>
+       </P></td>
+</tr>
+</table>
+
+<A HREF="#Usage Notes">USAGE</A> /
+<A HREF="#Namelist">NAMELIST</A> /
+<A HREF="#Discussion">DISCUSSION</A> /
+<A HREF="#Interface">INTERFACES</A> /
+<A HREF="#FilesUsed">FILES</A> /
+<A HREF="#References">REFERENCES</A> /
+<A HREF="#Errors">ERRORS</A> /
+<A HREF="#FuturePlans">PLANS</A> /
+<A HREF="#PrivateComponents">PRIVATE COMPONENTS</A> /
+<A HREF="#Legalese">TERMS OF USE</A>
+
+<H2>Overview</H2>
+
+<P>
+Routines in this module deal with two different types
+of quality control (QC) related functions.  The first is
+to support interpretation of the <em>incoming</em> data
+quality, to reject observations at assimilation time
+which are marked as poor quality.  The second is to
+document how DART disposed of each observation; whether
+it was successfully assimilated or rejected, and if
+rejected, for which reason.  
+</P>
+
+<!--=====================================================================-->
+<!--===================== USAGE NOTES ===================================-->
+<!--=====================================================================-->
+
+<A NAME="Usage Notes"></A>
+<div class="top">[<a href="#">top</a>]</div><hr />
+<H2>Usage</H2>
+
+<H4>Incoming Data Quality Control</H4>
+<P>
+DART currently supports a single incoming quality control
+scheme compatible with NCEP usage.  Lower values are considered
+better and higher values are considered poorer.
+A single namelist item, <em class=code>input_qc_threshold</em>
+sets the boundary between accepted and rejected observations.
+Values <em>larger</em> than this value are rejected; values
+equal to or lower are accepted.  Note that observations could
+be subsequently rejected for other reasons, including failing
+the outlier threshold test or all observations of this type
+being excluded by namelist control.  See the
+<a href="../observations/obs_kind_mod.html#Namelist">obs_kind_mod</a>
+namelist documentation for more details on how to enable or
+disable assimilation by observation type at runtime.
+</P>
+<P>
+The incoming quality control value is set when an observation 
+sequence file is created.  If the data provider user a different
+scheme the values must be translated into NCEP-consistent values.
+Generally we use the value 3 for most runs.
+</P>
+<P>
+Observations can also be rejected by the assimilation if the
+observation value is too far from the mean of the ensemble
+of expected values (the forward operator results).
+This is controlled by the <em class=code>outlier_threshold</em>
+namelist item.  
+</P>
+<P>
+Specifically, the outlier test computes the difference between the observation value
+and the prior ensemble mean.  It then computes a standard deviation by
+taking the square root of the sum of the observation error variance and
+the prior ensemble variance for the observation.  If the difference
+between the ensemble mean and the observation value is more than the
+specified number of standard deviations then the observation is not used.
+This can be an effective way to discard clearly erroneous observation values.
