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3<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
4  <head>
5    <title>grad.pro (SAXO Documentation Assistant)</title>
6  </head>
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[168]50<font size=-1><i>SAXO Documentation Assistant</i>: <a href="./../home.html">Overview</a></font></td>
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56
[168]57    <h1><font size="-2">Computation/</font></h1>
[163]58    <h2>grad.pro</h2>
59
60    <dl>
61    </dl>
62
63   
[321]64 compute the gradient of a variable located on Arakawa C-grid.
[163]65
66
67   
68
69     
70      <a name="#_grad"></a>
71
72      <h2>grad  <font size="-1" color="#006633">
[168]73 Calculation
[163]74</font></h2>
75
[321]76      <p><font face="Courier"><i>result = </i>grad(<i><a href="#_grad_keyword_field">field</a>, <a href="#_grad_keyword_direc">direc</a></i>, <a href="#_grad_keyword_MILLION">MILLION</a>=<i>scalar: 0 or 1</i>, <a href="#_grad_keyword__EXTRA">_EXTRA</a>=<i>_EXTRA</i>)</font></p>
[163]77
78   
79
[234]80
[242]81    <h3>Return value</h3>
[321]82 the gradient of the input data with the same size 2D, 3D or 4D
83 array, located on the appropriate grid (see restrictions)
[163]84
85
86   
87    <h3>Parameters</h3>
88   
89
90    <a name="#_grad_keyword_field"></a>
91    <h4>field&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
92     
93     
94     
95     
96     
97     
98     
99     
100    </h4>
101
102   
[242]103 The field for which we want to compute the gradient. A 2D (xy),
104 3D (xyz or yt) or 4D (xyzt) array or a structure readable by
[321]105 <a href="..//ToBeReviewed/LECTURE/litchamp.html">litchamp</a> and containing a 2D (xy), 3D (xyz or yt) or 4D (xyzt) array.
[242]106 Note that the dimension of the array must suit the domain dimension.
[163]107
108   
109
110    <a name="#_grad_keyword_direc"></a>
111    <h4>direc&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
112     
113     
114     
115     
116     
[168]117      <font size="-1" color="#006633">type:</font> <font size="-1" color="#006633"><i>scalar string</i></font>
[163]118     
119     
120    </h4>
121
122   
[168]123 the gradient direction: 'x', 'y', 'z'
[163]124
125   
126   
127
128   
[321]129    <h3>Keywords</h3>
[163]130
[321]131   
132    <a name="#_grad_keyword_MILLION"></a>
133    <h4>MILLION&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
134     
135     
136     
137     
138     
139      <font size="-1" color="#006633">type:</font> <font size="-1" color="#006633"><i>scalar: 0 or 1</i></font>
140      <font size="-1" color="#006633">default:</font> <font size="-1" color="#006633"><i>0</i></font>
141     
142    </h4>
143
144   
145 Activate to multiply returned array by 1.e6
146 
147   
148    <a name="#_grad_keyword__EXTRA"></a>
149    <h4>_EXTRA&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
150     
151     
152     
153     
154     
155     
156     
157     
158    </h4>
159
160   
161 Used to declare that this routine accepts inherited keywords
162
163   
164   
165
[234]166    <h3>Examples</h3><pre>
[163]167
[402]168   IDL> @tst_initorca2
169   IDL> plt, grad({arr:gphit,g:'T'}, 'x')
170   IDL> plt, grad({arr:gphit,g:'T'}, 'y')
171
[234]172    </pre><h3>Version history</h3>
[163]173   
174    <h4>Version</h4>
[402]175 $Id: grad.pro 371 2008-08-07 09:32:02Z pinsard $
[163]176
177    <h4>History</h4>
178 Sebastien Masson (smasson@lodyc.jussieu.fr)
179
180   
181
182    <h3>Known issues</h3>
183   
184   
[168]185   
[163]186    <h4>Restrictions</h4>
[234]187 - Works only for Arakawa C-grid.
[168]188 - When computing the gradient, the result is not on the same grid point
189   than the input data. In consequence, we update, vargrid and the grid position
190   parameters (firstx[tuvf], lastx[tuvf], nx[tuvf], firsty[tuvf], lasty[tuvf],
191   ny[tuvf], firstz[tw], lastz[tw], nz[tw]).
[234]192 - points that cannot be computed (domain boundaries, coastline) are set to NaN
[168]193 - the common variable jpt is used to differ xyz (jpt=1) and xyt (jpt=1) cases.
[163]194
195
196    <h3>Other attributes</h3>
197   
198   
199    <h4>Uses routines</h4>
[402]200 <a href="..//Commons/cm_4cal.html">cm_4cal</a>
201 <a href="..//Commons/cm_4data.html">cm_4data</a>
202 <a href="..//Commons/cm_4mesh.html">cm_4mesh</a>
[163]203
204   
205   
206   
207
208    <font size="-3"><p>&nbsp;</p></font>
209    <hr size="1" color="#CCCCCC"/>
210     
211
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213
[187]214    <p><font color="gray" size="-3">&nbsp;&nbsp;Produced by IDLdoc 2.0.</font></p>
[163]215
216  </body>
[249]217</html>
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