[ncl-talk] Contour Shape gets distorted for gsn_csm_contour_map plot

[Rick Brownrigg]

Hi,

Given the aspect ratio of the underlying data (range of -74.25...-70.17 in
lon, 36...46.9 in lat), it seems like the plot produced via
gsn_csm_contour_map is about what one would expect ?  I see you manually
assigned those geographic coordinates to the grid. Are those correct?  Do
you have other reasons to believe the storm shape should be more circular,
rather than elongated?

Not sure what to suggest here...

Rick


On Wed, Jan 2, 2019 at 10:46 AM Mansur Ali Jisan <jisan.mansur at gmail.com>
wrote:

> Dear NCL Community,
>
> I need help with contour map plot for a Hurricane wind field. At first, I
> used gsn_csm_contour function for making the plot and the shape of the
> storm looked correct. But when I tried to make a contour map plot using
> gsn_csm_contour_map, the shape got distorted. I tried to solve this by
> setting the res at mpShapeMode = "FreeAspect". While it improved the contour
> plot but the map got stretched. Similarly, I set up the map projection to
> cylindrical equidistant but still got the same result. I have added the
> code and PrintVarSummary. Any suggestions will be very helpful.
>
> Wishing you a Happy New Year!
>
>
> --------------------------------------------------------------------------------------------------------
>
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> begin
>   ntim = 318
>   nlat = 1202
>   mlon = 1202
>
>   f1 = addfile("bound_param_diag_var_rough.nc","r")
>   u = f1->um_bot   ; 97 x 1202 x 1202
>   v = f1->vm_bot
>   ws = sqrt(u^2+v^2)
>
>  lat  = fspan(36.07092, 46.86241,nlat)
>   lon  = fspan(-74.25677, -70.17657,mlon)
>
>   lat!0= "lat"                   ; name dimension
>   lat at units = "degrees_north"    ; associate units attribute
>   lat&lat   = lat                ; coordinate variable
>
>   lon!0= "lon"
>   lon at units = "degrees_east"
>   lon&lon   = lon
>
>   u!0 = "time"
>   u!1 = "lat"
>   u!2 = "lon"
>   u&lat = lat
>   u&lon = lon
>   v!0 = "time"
>   v!1 = "lat"
>   v!2 = "lon"
>
>   v&lat = lat
>   v&lon = lon
>
>   ws!0 = "time"
>   ws!1 = "lat"
>   ws!2 = "lon"
>
>   ws&lat = lat
>   ws&lon = lon
>
>  printVarSummary(lat)
>  print("-----")
>  printVarSummary(lon)
>  print("-----")
>  printVarSummary(u)
>  print("-----")
>
>   ws = mask(ws,ws.lt.4,False)
>   u = mask(u,u.lt.4,False)
>   v = mask(v,v.lt.4,False)
>
>   wks = gsn_open_wks("png","gsn_csm_contour_map")
>   res                          = True
>   res at gsnDraw        = False
>   res at gsnFrame      = False
>   res at gsnAddCyclic   = False
>   res at gsnMaximize    = True
>   res at cnFillOn            = True
>   res at cnLinesOn        = False
>   res at cnFillMode        = "AreaFill"
>   res at cnFillPalette      = "matlab_jet"
>
> ;  res at mpShapeMode = "FreeAspect"
> ;  res at vpWidthF = 0.6
> ;  res at vpHeightF = 0.5
>
>   res at tmXBOn = True
>   res at tmYLOn = True
>   res at tiMainString   = "gsn_csm_contour_map"
>   res at tmXBMode = "Explicit"
>   res at tmXBValues = (/-66, -67, -68, -69, -70, -71,  -72,  -73,   -74,
> -75, -76, -77/)
>   res at tmXBLabels =
> (/"66W","67W","68W","69W","70W","71W","72W","73W","74W","75W","76W","77W"/)
>
>   res at tmYLMode = "Explicit"
>   res at tmYLValues = (/34, 35,  36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46,
> 47/)
>   res at tmYLLabels =
> (/"34N","35N","36N","37N","38N","39N","40N","41N","42N","43N","44N","45N","46N","47N"/)
>
>   res at cnLevelSelectionMode = "ManualLevels"
>   res at cnMinLevelValF       = 10
>   res at cnMaxLevelValF       = 80
>   res at cnLevelSpacingF      = 2.5
>
>   res at mpFillOn = False
>   res at mpGeophysicalLineThicknessF = 2.5
>   res at mpOutlineBoundarySets     = "geophysicalandusstates"
>   res at mpDataBaseVersion = "MediumRes"
>   res at mpDataSetName = "Earth..4"
>   res at mpGeophysicalLineColor = "Black"
>
>   res at mpLimitMode = "LatLon"
>   res at mpMinLatF = 36.0
>   res at mpMaxLatF = 46.0
>   res at mpMinLonF = -76.0
>   res at mpMaxLonF = -70.0
>
>   plot = gsn_csm_contour_map(wks,ws(22,:,:),res)
>
> draw(plot)
>
> frame(wks)
>
> end
>
>
> Variable: lat
> Type: float
> Total Size: 4808 bytes
>             1202 values
> Number of Dimensions: 1
> Dimensions and sizes:   [lat | 1202]
> Coordinates:
>             lat: [36.07092..46.86241]
> Number Of Attributes: 1
>   units :       degrees_north
> (0)     -----
>
> Variable: lon
> Type: float
> Total Size: 4808 bytes
>             1202 values
> Number of Dimensions: 1
> Dimensions and sizes:   [lon | 1202]
> Coordinates:
>             lon: [-74.25677..-70.17657]
> Number Of Attributes: 1
>   units :       degrees_east
> (0)     -----
>
>
> Variable: u
> Type: float
> Total Size: 1837790688 bytes
>             459447672 values
> Number of Dimensions: 3
> Dimensions and sizes:   [time | 318] x [lat | 1202] x [lon | 1202]
> Coordinates:
>             lat: [36.07091903686523..46.86241149902344]
>             lon: [-74.25676727294922..-70.17656707763672]
> Number Of Attributes: 1
>   units :
> (0)     -----
>
>
> --
> *Mansur Ali Jisan*
> Ph.D. Student
> URI Graduate School of Oceanography, RI 02882
>
> <hasancee at iut-dhaka.edu>
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