<div dir="ltr">Hi,<div><br></div><div>Could someone please help me with a conceptual skewT + hodograph plot?  My hope is to create a skewT plot with a hodograph overlaid, much like what you see from other skewT plots, such as this one: <a href="http://weather.rap.ucar.edu/upper/dnr.gif">http://weather.rap.ucar.edu/upper/dnr.gif</a>.  I couldn't find any examples on the NCL website, so I thought I could create my own, but couldn't get it to plot correctly.</div><div><br></div><div>Conceptually, I imagine the script would be created in this order:</div><div>1) Draw the background using <a href="https://www.ncl.ucar.edu/Document/Functions/Skewt_func/skewT_BackGround.shtml">skewT_BackGround</a>.</div><div>2) Draw the hodograph using <a href="https://www.ncl.ucar.edu/Document/Graphics/Interfaces/gsn_csm_xy.shtml">gsn_csm_xy</a></div><div>   - making sure to set gsnDraw and gsnFrame to False</div><div>   - set vpXF, vpYF, vpWidthF, and vpHeightF to only plot in the upper-lefthand side of the plot</div><div>3) Use the <a href="http://overlay">overlay</a> procedure to overlay the two, like this: overlay(skewt_bkgd,hodo_plot)</div><div>4) Draw the plot, like this: draw (skewt_bkgd)</div><div>5) Use the <a href="https://www.ncl.ucar.edu/Document/Functions/Skewt_func/skewT_PlotData.shtml">skewT_PlotData</a> to overlay the skewT data.</div><div>6) Advance the frame: frame(wks)</div><div><br></div><div>I almost got it to work, except the hodograph only plots on the bottom of the image the portion of the hodograph with positive V component (I assume the rest is "off screen" below); I assume it is using the native coordinate system of <a href="https://www.ncl.ucar.edu/Document/Functions/Skewt_func/skewT_BackGround.shtml" style="color:rgb(17,85,204);font-family:arial,sans-serif;font-size:small;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255)">skewT_BackGround</a> instead of having its own independent coordinate system.</div><div><br></div><div>Does anyone have any thoughts or ideas of how I can do this?  Thanks!</div><div><br></div><div>Joe</div><div><br></div><div>P.S.  Here is the current version of my code:</div><div><br></div><div><div>load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/skewt_func.ncl"</div><div>begin</div><div>; Read in WRF data</div><div> in_file = "/d3/ATEC/wrfout_misc/ATC/wrfout_d01_2017-09-02_05:00:00.ATC_P+FCST"</div><div> ncdf_in = addfile(in_file+".nc","r")</div><div> P_tot      = wrf_user_getvar(ncdf_in,"pressure",0)</div><div> z_tot      = wrf_user_getvar(ncdf_in,"z",-1)</div><div> U          = wrf_user_getvar(ncdf_in,"U",-1)</div><div> U_unstag = wrf_user_unstagger(U,U@stagger)</div><div> V          = wrf_user_getvar(ncdf_in,"V",-1)</div><div> V_unstag = wrf_user_unstagger(V,V@stagger)</div><div> TC         = wrf_user_getvar(ncdf_in,"tc",-1)</div><div> TD         = wrf_user_getvar(ncdf_in,"td",-1)</div><div><br></div><div>; Create skewT background</div><div> PlotType = "png"</div><div> PlotName = "Sounding_MartinAF"</div><div> wks = gsn_open_wks(PlotType,PlotName)</div><div>  loc = wrf_user_ll_to_ij(ncdf_in,-76.42,39.33,True)</div><div>  locX = loc(0) - 1</div><div>  locY = loc(1) - 1</div><div> skewtOpts          = True</div><div> skewtOpts@vpXF              = 0.07    ; controls off-set from left</div><div> skewtOpts@vpYF              = 0.92    ; controls off-set from top</div><div> skewtOpts@vpWidthF          = 0.85    ; controls size of plot</div><div> skewtOpts@vpHeightF         = 0.85    ; controls size of plot</div><div> skewtOpts@tiMainString = "Sounding at 39.33N, 76.42W"</div><div> skewt_bkgd             = skewT_BackGround (wks, skewtOpts)</div><div> draw (skewt_bkgd)</div><div><br></div><div>; Draw hodograph here???</div><div> hodo_res = True</div><div> hodo_res@vpXF      = 0.07</div><div> hodo_res@vpYF      = 0.92</div><div> hodo_res@vpWidthF  = 0.15</div><div> hodo_res@vpHeightF = 0.15</div><div> hodo_res@gsnDraw   = False</div><div> hodo_res@gsnFrame  = False</div><div> hodo_plot = gsn_csm_xy(wks,U_unstag(0,:,locY,locX),V_unstag(0,:,locY,locX),hodo_res)</div><div> overlay(skewt_bkgd,hodo_plot)</div><div> draw (skewt_bkgd)</div><div><br></div><div>; Draw the skew-T data</div><div> dataOpts           = True</div><div> dataOpts@Parcel          = 1</div><div> dataOpts@WspdWdir        = False  ; wind speed and dir [else: u,v]</div><div> skewT_data = skewT_PlotData(wks, skewt_bkgd, P_tot(:,locY,locX), \</div><div>                                               TC(0,:,locY,locX), \</div><div>                                               TD(0,:,locY,locX), \</div><div>                                            z_tot(0,:,locY,locX), \</div><div>                                         U_unstag(0,:,locY,locX), \</div><div>                                         V_unstag(0,:,locY,locX), \</div><div>                                             dataOpts)</div><div> frame(wks)</div><div><br></div><div>end</div></div></div>