[ncl-talk] how to plot divergent winds, divergence and velocity potential in one single plot?
Vyankatesh Manoj Mundhada
vyankatesh at iiserb.ac.in
Sat Feb 24 02:33:57 MST 2018
Hello,
I am new to NCL and I am trying to plot annual mean climatology for
divergent winds (vectors), divergence (contours (shading)) and velocity
potential (contours (lines)) in a single plot using velocities u and v
only. I am using two input .nc files f1 and f2, where f1 contains u and v
and f2 contains velocity potential.
I am trying to plot divergent velocities over velocity potential using the
following script:
begin
;*************************************************
; open file and read in data: data are on a gaussian grid
;*************************************************
f1 = addfile ("ERAI_200uvd_1979-2010_new.nc", "r")
u = f1->u
v = f1->v
f2 = addfile ("ERAI_200sfvp_1979-2010_new.nc", "r")
vp = f2->velopot
;*************************************************
; calculate divergence on a gaussian grid
;*************************************************
div = uv2dvG_Wrap(u,v) ; u,v ==>
divergence
div at long_name = "Divergence"
div at units = "s-1"
;*************************************************
; calculate velocity potential
;*************************************************
;chi = ilapsG_Wrap ( div , 0)
chi = new ( dimsizes(vp), double, vp at _FillValue )
chi = (/vp/1e4/) ;
arbitrary scale
copy_VarCoords(vp, chi )
;chi at long_name = "velocity potential"
;chi at units = "m^2/s"
;*************************************************
; calculate divergent wind component
; --
; note: the calculation uses a procedure, so memory
; must be preallocated.
;*************************************************
ud = new ( dimsizes(u), double, u at _FillValue )
vd = new ( dimsizes(v), double, v at _FillValue )
dv2uvg(div,ud,vd) ; div ==> divergent wind components
copy_VarCoords(u, ud )
copy_VarCoords(v, vd )
ud at long_name = "Zonal Divergent Wind"
ud at units = u at units
vd at long_name = "Meridional Divergent Wind"
vd at units = v at units
;udAve = avg(ud(:,:,:,:))
;vdAve = avg(vd(:,:,:,:))
;scale =(/vdAve/udAve/)
;ud = (/scale*ud/)
ud = (/ud/1e3/)
vd = (/vd/1e3/)
div = (/div*1e3/)
;UD = month_to_annual(ud, 1)
;VD = month_to_annual(vd, 1)
;DIV = month_to_annual(div, 1)
;CHI = month_to_annual(chi, 1)
UDavg = dim_avg_n_Wrap(ud, (/0,1/))
VDavg = dim_avg_n_Wrap(vd, (/0,1/))
DIVavg = dim_avg_n_Wrap(div, (/0,1/))
CHIavg = dim_avg_n_Wrap(chi, (/0,1/))
CHIavg = abs(CHIavg)
;*************************************************
; plot results
;*************************************************
wks = gsn_open_wks("png","vp_dv_d") ; send graphics to PNG
file
;cmap = read_colormap_file("GMT_polar")
;cmap = read_colormap_file("GMT_seis")
cmap = read_colormap_file("cmp_b2r")
nc = dimsizes(cmap(:,0))
res = True
res at gsnDraw = False
res at gsnFrame = False
cnres1 = res
cnres2 = res
vcres = res
cnres1 at cnFillOn = True ; color on
cnres1 at cnLinesOn = False ; turn off contour lines
cnres1 at cnFillPalette = cmap(:nc-4,:)
cnres1 at tiMainString = "Divergent Winds, Divergence and Velocity
Potential"
cnres1 at cnLevelSelectionMode = "ManualLevels" ; manually set the
contour levels with the following 3 resources
cnres1 at cnMinLevelValF = -5. ;
set the minimum contour level
cnres1 at cnMaxLevelValF = 5. ;
set the maximum contour level
cnres1 at cnLevelSpacingF = 0.5 ;
set the interval between contours
cnres1 at lbOrientation = "vertical"
cnres1 at lbBoxSeparatorLinesOn = False
cnres1 at lbTitleString = div at long_name
cnres1 at lbTitlePosition = "Left"
cnres1 at lbAutoManage = False
cnres1 at lbTitleFontHeightF = 0.012
;cnres1 at lbLabelStrings = (/"-5.0","-2.5","0","2.5","5.0"/)
cnres1 at mpMinLonF = 0
cnres1 at mpMaxLonF = 360
cnres1 at mpCenterLonF = 180 ; This is necessary to get the
correct map
cnres1 at mpMinLatF = -80
cnres1 at mpMaxLatF = 80
vcres at vcRefMagnitudeF = 10. ; make vectors larger
vcres at vcRefLengthF = 0.05 ; ref vector length
vcres at vcGlyphStyle = "CurlyVector" ; turn on curly vectors
vcres at vcMinDistanceF = 0.012 ; thin the vectors
vcres at vcRefAnnoOrthogonalPosF = 0 ; Move ref anno into plot
vcres at vcRefAnnoBackgroundColor = "Background"
vcres at vcRefAnnoString2On = False
;vcres at vcRefAnnoSide = "Left"
;cnres2 at gsnCenterString = "Chi scaled by 1e8"
cnres2 at cnFillOn = False
cnres2 at cnLinesOn = True
;cnres2 at mpMinLonF = 0
;cnres2 at mpMaxLonF = 360
;cnres2 at mpCenterLonF = 180 ; This is necessary to get the
correct map
cnres2 at trGridType = "TriangularMesh"
plot1 = gsn_csm_vector(wks,UDavg(:,:),VDavg(:,:),vcres)
plot2 =
gsn_csm_contour_map_overlay(wks,DIVavg(:,:),CHIavg(:,:),cnres1,cnres2)
overlay(plot2,plot1)
draw(plot2)
frame(wks)
end
I am getting the following warning messages:
(0) check_for_y_lat_coord: Warning: Data either does not contain a valid
latitude coordinate array or doesn't contain one at all.
(0) A valid latitude coordinate array should have a 'units' attribute
equal to one of the following values:
(0) 'degrees_north' 'degrees-north' 'degree_north' 'degrees north'
'degrees_N' 'Degrees_north' 'degree_N' 'degreeN' 'degreesN' 'deg north'
(0) check_for_lon_coord: Warning: Data either does not contain a valid
longitude coordinate array or doesn't contain one at all.
(0) A valid longitude coordinate array should have a 'units' attribute
equal to one of the following values:
(0) 'degrees_east' 'degrees-east' 'degree_east' 'degrees east'
'degrees_E' 'Degrees_east' 'degree_E' 'degreeE' 'degreesE' 'deg east'
and the plot which is attached to this mail. I think I am getting proper
divergence but velocity potential lines are not getting plotted at all and
I feel the direction of winds are also wrong. So please help me to get a
proper plot without error. I am expecting humble reply from your side.
Thanking you,
Vyankatesh Mundhada
On Wed, Feb 21, 2018 at 5:40 PM, Vyankatesh Manoj Mundhada <
vyankatesh at iiserb.ac.in> wrote:
> Thank you very much. That was really helpful.
>
> Regards,
> Vyankatesh
>
> On Wed, Feb 21, 2018 at 4:03 PM, Guido Cioni <guidocioni at gmail.com> wrote:
>
>> Hi,
>> This error usually pops up when you're doing assignment that delete the
>> original attributes of the variable, including the reference to the
>> coordinate variables.
>>
>> I'm just speculating but...could it be this line?
>>
>> plot1 = gsn_csm_vector_map(wks,0.001*ud(0,0,:,:),0.001*vd(0,0,:,:),v
>> cres)
>>
>> You are doing 0.001*ud(0,0,:,:), so merely assigning a new variable
>> without copying the attributes.
>> You should instead do the scaling first
>>
>> ud=0.001*ud(:,:,:,:) ; here the attributes are preserved
>>
>> and then plot ud(0,0,:,:).
>> Or just a define a new variable based un ud first.
>>
>> Let us know whether that works, that's the first thing that comes to my
>> mind.
>>
>>
>>
>> On 21. Feb 2018, at 10:20, Vyankatesh Manoj Mundhada <
>> vyankatesh at iiserb.ac.in> wrote:
>>
>> 0.001*vd(0,0,:,:)
>>
>>
>>
>> Guido Cioni
>> http://guidocioni.altervista.org
>>
>>
>
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