<div dir="ltr"><div>Hi -- I don't really know the answer to your question. I do note wrf_user_ll_to_ij() is considered deprecated in the latest version of NCL, and it is recommended to use wrf_user_ll_to_xy() instead. Also, are you taking into account that wrf_user_ll_to_ij() returns a 1-based index (the recommended function returns a 0-based index)? <br></div><div><br></div><div>Hope that helps..</div><div>Rick<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Mon, May 27, 2019 at 7:37 PM LSL <<a href="mailto:lslrsgis@whu.edu.cn">lslrsgis@whu.edu.cn</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF">
Dear NCL Community,
<div class="gmail-m_-7688987409912985110moz-forward-container">
<div class="gmail-m_-7688987409912985110moz-forward-container">
<p style="margin-bottom:0in;line-height:100%"><br>
</p>
<p style="margin-bottom:0in;line-height:100%">I am writing
for a wrf_usr_ll_to_ij problem. I am trying to extract
stations within WRF domain 01, and converting lat/lon to i/j.
However, I found the i/j are not correctly converted, since
XLAT(i,j), XLONG(i,j) are not the same as the original
lat/lon.</p>
<p style="margin-bottom:0in;line-height:100%"><br>
</p>
<p style="margin-bottom:0in;line-height:100%">For example,
the first line in file (2)
REP-SITE-LIST-LAT-LON-XY-REVISED-ECO.TXT attached:</p>
<p style="margin-bottom:0in;line-height:100%"><font style="font-size:10pt" size="2">ID LAT LON I J I_MAX-I
J_MAX-J LON_S LAT_S LAT_R LON_R LAT_R’ LON_R’ </font> </p>
<p style="margin-bottom:0in;line-height:100%"><font style="font-size:10pt" size="2">52101 43.44 93.04 2 67 59
23 92.87 43.52 26.06 115.21 42.11 101.25</font></p>
<p style="margin-bottom:0in;line-height:100%"><br>
</p>
<p style="margin-bottom:0in;line-height:100%">To verify the
I,J calculated, three pairs of lat/lon are reconstructed as
follows:</p>
<p style="margin-bottom:0in;line-height:100%"><br>
</p>
<p style="margin-bottom:0in;line-height:100%"><font style="font-size:10pt" size="2">LAT_S/LON_S are calculated
from wrf_usr_ij_to_ll(J,I)</font></p>
<p style="margin-bottom:0in;line-height:100%"><font style="font-size:10pt" size="2">LAT_R/LON_R are calculated
from XLAT(I,J), XLONG(I,J)</font></p>
<p style="margin-bottom:0in;line-height:100%"><font style="font-size:10pt" size="2">LAT_R’/LON_R’ are
calculated from XLAT(I_MAX-I,J_MAX-J),
XLONG(I_MAX-I,J_MAX-J)</font></p>
<p style="margin-bottom:0in;line-height:100%"><br>
</p>
<p style="margin-bottom:0in;line-height:100%">Any indication
is appreciated. Thanks.</p>
<p style="margin-bottom:0in;line-height:100%">LSL<br>
</p>
<p style="margin-bottom:0in;line-height:100%"><br>
</p>
<p style="margin-bottom:0in;line-height:100%">P.S. Three
fiels are attached:</p>
<p style="margin-bottom:0in;line-height:100%">(1)extract_list_CMA_sites_within_WRF_D01_latlon_XY_VERSION001.ncl
--extraction code</p>
<p style="margin-bottom:0in;line-height:100%">(2)PREP-SITE-LIST-LAT-LON-XY-REVISED-ECO.TXT
--extraction results</p>
<p style="margin-bottom:0in;line-height:100%">(3)SURF_CLI_CHN_MUL_DAY-PRE-13011-SITE-LIST.TXT
--CMA station list (with lat/lon)</p>
<p style="margin-bottom:0in;line-height:100%"><br>
</p>
<p style="margin-bottom:0in;line-height:100%">(4)<a href="http://wrfout_d01.nc" target="_blank">wrfout_d01.nc</a>
--wrfout file, big as 8.4M, not attached<br>
</p>
<p style="margin-bottom:0in;line-height:100%">
</p>
<p>
</p>
</div>
</div>
</div>
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</blockquote></div>