How to Extract and plot wind vectors in a box

Dear NCL users,

I have a* .nc* file (*met_em_files* after WPS) which have U (wind) and V
(Wind) values for the domain 7N-20N; 70E-80E and which is staggered. I want
to extract and unstagger them (only u and v) and then plot (u,v) vector
for the domain *8N; 76E-77E* and *18N; 73E-74E* (domain attached *doc1.pdf*).

The below is my approach (I modified the domain from 73E-77E and 78N-18N).

But the issues are:
1). The vectors are not as expected. I have values at all grid points but
only few vectors r there.
2). Not able to generate the box I wanted (as highlighted in doc1.pdf).
3). I wanted to plot the (u,v) vector at the four corners of the box.

Can anyone suggest a solution to this?

load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRF_contributed.ncl"

begin

  a = addfile("met_em.d01.2009-04-01_00:00:00.nc","r")

  uu = wrf_user_getvar(a, "UU", 0)
  ua = uu(1,:,:)
  u = wrf_user_unstagger(ua,ua@stagger)

  vv = wrf_user_getvar(a, "VV", 0)
  va = vv(1,:,:)
  v = wrf_user_unstagger(va,va@stagger)

  wks = gsn_open_wks("ps", "uv_plot") ; open ps file
  gsn_define_colormap(wks,"gui_default") ; choose colormap

  res = True ; plot mods desired
  res@gsnMaximize = True ; maximize size
  res@gsnSpreadColors = True ; use full colormap
  res@gsnSpreadColorEnd = -2
  res@lbOrientation = "vertical" ; vertical label bar
  res@mpFillOn = True ; no map fill
  res@vcRefMagnitudeF = 5 ; make vectors larger
  res@vcRefLengthF = 0.025 ; ref vec length
  res@vcMinDistanceF = 0.025 ; thin out vectors
  res@vcGlyphStyle = "CurlyVector" ; choose wind barbs
  res@vcLabelsOn = True
 res@vcMonoLineArrowColor = False ; color barbs by scalar

  minlat = 8
  maxlat = 18
  minlon = 73
  maxlon = 77

  res@mpMinLatF = minlat
  res@mpMaxLatF = maxlat
  res@mpMinLonF = minlon
  res@mpMaxLonF = maxlon
  res@mpOutlineBoundarySets = "National"
  res@pmTickMarkDisplayMode = "Always"
  res@mpFillOn = False ; turn off map fill
  res@mpOutlineDrawOrder = "PostDraw"

   plot=gsn_csm_vector_map_ce(wks,u,v,res)

end

*-- *
***Regards,*
*A.R.Ragi*
 *Research Scholar
*
*Centre for Atmospheric Sciences
IIT Delhi, Hauz Khas
New Delhi, India.
*
**

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