<div dir="ltr"><div><div><div><div><div><div><div>Mary was guessing that the TRMM data was curvilinear where the latitude and longitudes are two-dimensional. RG lat2d(nlat,mlon) and lon2d(nlat,mlon)<br><br></div>However, *if* your data has a structure like the following. The grid is **rectilinear**.<br><br>netcdf TRMM {<br>dimensions:<br> time = UNLIMITED ; // (172 currently)<br> longitude = 1440 ;<br> latitude = 400 ;<br>variables:<br> double time(time) ;<br> time:units = "hours since 1998-1-1 0" ;<br> double longitude(longitude) ;<br> longitude:units = "degrees_east" ;<br> longitude:long_name = "Longitude" ;<br> double latitude(latitude) ;<br> latitude:units = "degrees_north" ;<br> latitude:long_name = "Latitude" ;<br> float pcp(time, latitude, longitude) ; <====<br> pcp:comments = "Unknown1 variable comment" ;<br> pcp:long_name = "precipitation:" ;<br> pcp:units = "" ;<br></div>[snip]<br><br>===<br></div>Also, the question is a bit ambiguous. Please be clear when posting questions.<br><br></div>re: <br>" ... extract some grid values of TRMM according to a series of specified
point locations (defined by their latitudes and longitudes).<br><br>===<br></div><div>If you want a *region* from a *rectilinear* grid<br><br></div><div> latS = -25<br></div><div> latN = 15<br></div><div> lonL = -120<br></div><div> lonR = 30<br><br></div><div><div> f = addfile("...", "r")<br></div><div> PCP = f->pcp(:, {latS:latN},{lonL:lonR}) <br></div> printVarSummary(PCP)<br><br><br>Variable: PCP<br>Type: float<br>Total Size: 66048000 bytes<br> 16512000 values<br>Number of Dimensions: 3<br>Dimensions and sizes: [time | 172] x [latitude | 160] x [longitude | 600] <===<br>Coordinates: <br> time: [ 0..124896]<br> latitude: [-24.875..14.875]<br> longitude: [-119.875..29.875]<br><br>=================================<br></div>So if you want random *individual grid points* from a *rectilinear* grid:<br><br></div> LAT = (/ -20, 0, 25/) ; user specified grid location<br></div> LON = (/0, 50, 100/)/)<br><div><div><div> <div><div><div><div><br></div><div> f = add file("...", "r")<br></div><div> pcp = f->pcp(:, {LAT},{LON}) ; all timed at 3 grid locations<br></div><div> printVarSummary(pcp)<br><br>===<br>Variable: pcp<br>Type: float<br>Total Size: 6192 bytes<br> 1548 values<br>Number of Dimensions: 3<br>Dimensions and sizes: [time | 172] x [latitude | <b>3</b>] x [longitude | <b>3</b>]<br>Coordinates: <br> time: [ 0..124896]<br> latitude: [-20.125..24.875]<br> longitude: [-0.125..99.875]<br>Number Of Attributes: 9<br><br>====<br><br></div><div>If you are learning NCL, please spend the time to look at <br><br><a href="http://www.ncl.ucar.edu/Document/Manuals/NCL_User_Guide/">http://www.ncl.ucar.edu/Document/Manuals/NCL_User_Guide/</a><br></div><div><br></div><div>This will help you learn the language<br></div></div></div></div></div></div></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Mar 14, 2017 at 10:09 AM, Mary Haley <span dir="ltr"><<a href="mailto:haley@ucar.edu" target="_blank">haley@ucar.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_default" style="font-size:small;display:inline">Hi </div>Yi Lu,<br><br>We have a examples page on subsetting data based on lat/lon. See:<br><br><a href="http://www.ncl.ucar.edu/Applications/latlon_subset.shtml" target="_blank">http://www.ncl.ucar.edu/<wbr>Applications/latlon_subset.<wbr>shtml</a><br><br>I believe TRMM data is represented by two-dimensional lat/lon arrays, is that correct? If so, then the "latlon_subset_2.ncl" example is the one you want to look at. The function it uses is getind_latlon2d:<br><br><a href="http://www.ncl.ucar.edu/Document/Functions/Contributed/getind_latlon2d.shtml" target="_blank">http://www.ncl.ucar.edu/<wbr>Document/Functions/<wbr>Contributed/getind_latlon2d.<wbr>shtml</a><br><br>--Mary<div class="gmail_default"><br></div><div class="gmail_default"><br></div></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div class="h5">On Tue, Mar 14, 2017 at 8:26 AM, 易路 <span dir="ltr"><<a href="mailto:dg1225033@smail.nju.edu.cn" target="_blank">dg1225033@smail.nju.edu.cn</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div class="h5"><div>Hi, all</div><div> I planned to extract some grid values of TRMM according to a series of specified point locations (defined by their latitudes and longitudes), but I don't know which function I could use, are there any functions in NCL like wrf_user_ll_to_ij() and wrf_user_ij_to_ll() to obtain the grid numbers of TRMM according to the latitude and longitude information?</div><div> Thanks very much for your attentions and precious time!</div><div> </div><div>Best wishes!</div><div> </div><div>Yi Lu</div><div><u></u><div style="color:rgb(144,144,144);font-family:Arial Narrow;font-size:12px"><br><br><br><br></div><div style="color:rgb(0,0,0);font-family:Verdana;font-size:14px"><div style="overflow:hidden"><table class="m_799404551415173320m_-4797716102570359145preview_table"><tbody><tr><td valign="middle"><img id="m_799404551415173320m_-4797716102570359145preview_qrcode" src="https://exmail.qq.com/cgi-bin/setting_qrcode_card?action=qrcode_card&alias=dg1225033@smail.nju.edu.cn&key=33b1e5708e6a55b5"></td><td style="color:rgb(160,160,160);font-size:12px" valign="middle"><h4 class="m_799404551415173320m_-4797716102570359145name" style="margin:0px;color:rgb(0,0,0);line-height:28px;font-size:14px;font-weight:bold">易路</h4><p class="m_799404551415173320m_-4797716102570359145department" style="margin:0px">南大邮件系统/学生/博士生/12级博士生</p><p class="m_799404551415173320m_-4797716102570359145addr" style="margin:0px;color:rgb(160,160,160);line-height:22px">南京市汉口路22号 </p></td></tr></tbody></table></div></div><u></u></div><div> </div><div><u></u><u></u></div><br></div></div>______________________________<wbr>_________________<br>
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