<div dir="ltr"><div><div><div><div><div><div><div><div><div><div>Brian, <br><br></div><div>wrfhelp is being cc'd. They are the WRF experts and may know how to compute geostrophic winds.<br><br>===<br></div><div><br>You have obviously put a lot of work into trying to derive geostrophic winds from WRF variables. Unfortunately, the steps you have used will not return the results you wish. A few comments:<br>
<br></div><div>[0] <br>The ftp area was 100% full. Thus, your files could not be accommodated<span></span>. The IT people have cleaned up the ftp file system. That said, transmitting 9GB file(s) is not commonly done for ncl-talk related questions. You should use tools (say, netCDF operators or NCL) to subset the data. For example, only one time step.<br>
</div><div> ncks -O -d Time,0 WrfBigFile.nc WrfLittleFile.nc <br></div><div><br></div>[1] <br>z2geos works *only* for rectilinear grids with variables on isobaric levels. The documentation has been changed to make this more explicit.<br>
<a href="http://www.ncl.ucar.edu/Document/Functions/Built-in/z2geouv.shtml">http://www.ncl.ucar.edu/Document/Functions/Built-in/z2geouv.shtml</a><br><br>**Generally,** WRF grids are curvilinear. The following operation does *not* make make a curvilinear grid and rectilinear grid<br>
</div><br></div>
lat = f->XLAT(0,:,0) ; lat(south_north)<br></div> lon = f->XLONG(0,0,:) ; lon(west_east)<br><br></div>Yes, lat and lon are one-dimensional BUT they do not represent a rectilinear grid orientation.<br>
</div>Use of the above lat & lon would be erroneous. You will get numbers but they are not the correct numbers.<br><br>[2] <br></div>Using, say, the ESMF regridding to interpolate the WRF curvilinear gridded data to a rectilinear grid is a possibility *if* working with data on a rectilinear grid is adequate for the problem you wish to address. <br>
<br>[a] Attached is a simple (*untested*) function that will interpolate a WRF (mass) variable on eta levels to user specified isobaric levels;.<br><br> function eta2isop_wrf(fwrf, varName[1]:string, prs_iso[*]:numeric \<br>
,itime:integer, linlog[1]:integer, opt[1]:logical)<br> Usage:<br> f = addfile(...) , or, f = addfiles(...)<br> <br> plev = (/ 1000,925,850,700,600,500,400,300,250 \ ; integer, float, double<br>
, 200,150,100,70,50/)<br> plev!0 = "plev"<br> plev@units = "hPa"<br><br> linlog = 0<br> itime = -1<br> z_iso = eta2isop_wrf(f, "geopotential", plev, itime, linlog, False)<br>
<br>[b] You could now use z2geouv to calculate the geostrophic components<br><br></div>[c] Unfortunately, reinterpolating the components [b] back to the WRF grid will not yield geostrophic winds.<br><br>===<br></div>Hopefully, wrfhelp can provide some information or talk with your advisor.<br>
<br></div>Good Luck<br><div><div><br><br><div><div><div>
<br><br></div></div></div></div></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Mon, Aug 11, 2014 at 8:55 PM, brianjs @<a href="http://iastate.edu">iastate.edu</a> <span dir="ltr"><<a href="mailto:brianjs@iastate.edu" target="_blank">brianjs@iastate.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">Good Evening,<div><br></div><div>I am attempting to calculate both the u and v components of the geostrophic winds in the WRF. </div>
<div><br></div><div>The function z2geouv (which calculates both components using the geopotential height, as well as the latitude and longitude of gridded data) must utilize the geopotential height on a constant pressure surface. WRF data however, is on constant eta levels/terrain following coordinates, and as such, this function applied to WRF data could only work if data is converted to a constant pressure surface from its original eta coordinate system.</div>
<div><br></div><div>Attached is the WRF code with issues. I have attempted to calculate the geostrophic wind components (ug and vg) by using the z2geouv with a height variable that has been interpolated on to a constant pressure coordinate (z_const_p). I first attempted to interpolate z_const_p with a geopotential height variable that was not terrain following (z_model). When I do this, I get realistic values for the geostrophic wind components, but I obviously would not get the lower levels (below 1000 generally) to be interpolated. I also interpolated z_const_p with an original terrain following geostrophic height or geostrophic height above ground level (AGLheight_model), but then unrealistic answers followed. </div>
<div><br></div><div>I have also taken a similar approach by calculating the ug and vg components separately without using z2geouv, but I am still getting unrealistic answers. </div><div><br></div><div>
I wish to implement this routine in order to plot the geostrophic winds on maps of constant height (above ground level) hence the ug/vg interpolations thereafter to constant height levels</div><div><br></div><div>For reference, I sent the used RUC and WRF output to the ncl-talk FTP account given their large size. I did get the message "451 Failure writing to local file" so I am not sure if they made it over there successfully. The wrf file is rather large (approximately 9 GB) so maybe the account could not hold it?</div>
<div><br></div><div>I was wondering if someone could guide me to improve this code to get geostrophic winds interpolated on constant height fields from an original terrain following (eta) coordinate system (i.e. 200-2000 m at 100 m intervals), or if someone could assist by making a recommendation for an alternate approach? I have also attached my RUC code for plotting RUC Analysis geostrophic winds along with some sample images of what I believe the WRF profile should look generally like (as the RUC data is already on constant pressure surface).</div>
<div><br></div><div>Any suggestions would be greatly appreciated!<br></div><div><br></div><div>Brian Squitieri</div><div>Graduate Research Assistant</div><div>Iowa State University</div>
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