[ncl-talk] A question about vertical section of wind vector with wrfout data

[Mary Haley]

Dear Yan,

I'm not an expert in this area, but I didn't see any responses to your
question so I'll try to help.

First, if I understand your question, I'm not sure how that particular
figure was generated. I doubt it was done using wrf_vector, because is
mainly for drawing surface vector plots. Also, if this is a plot of
curvilinear data, then I doubt gsn_csm_vector_pres_hgt was used, because
this assumes that the level dimension is a coordinate array attached to the
data.

It's a bit tricky to do vertical cross sections with vector data on a
curvilinear grid because then what do your X and Y axes actually
represent?  Since the x,y value at each grid location is different, you
can't really put meaningful labels on the X and Y axis.

What exactly do you want to take the cross section of? You can arbitrarily
slice the data across some index value in the latitude or longitude
direction, but then again, the X and Y axis will not really have any
meaning, and so we can only label them with index values.

I created a simple script that reads QVAPOR, and U/V (at mass points) off a
WRF file, and then creates vectors over a filled contour plot at an
arbitrary latitude index value across all height/longitude values.

I plotted the data two ways:

The first way I let NCL label the X and Y axis with array index values.

The second way I set trGridType to TriangularMesh, which allows us to have
2D X and Y axis values set.  Notice that this changes the shape of the plot
and also the X and Y axis now have labels.

As a side, I should point out that it's just the height values that are
different at each location.  At any particular height location, the
longitude values are actually all the same across a latitude index, and
vice versa.  But, I think NCL doesn't like it when you try to plot data
using a 2D array for one axis and a 1D array for the other axis, so I
propagated the 1D longitude array to a 2D array using conform.

I'm not sure this is what you want, but hopefully you will see that you
need to be careful with cross sections of curvilinear data.

--Mary




On Thu, Sep 14, 2017 at 8:07 PM, 古枫玥瑟 <6544191 at qq.com> wrote:

> Dear ncl-talk,
> I want to draw a figure as shown below. Is the vertical section of wind
> vector drawed by "gsn_csm_pres_hgt_vector" or  "wrf_vector"?
> My data is WRF-ARW data like "wrfout_d03_2016-08-11_00:00:00".
> May I follow with the example of  "*wrf_CrossSection4.ncl
> <http://www2.mmm.ucar.edu/wrf/OnLineTutorial/Graphics/NCL/Examples/CROSS_SECTION/wrf_CrossSection4.ncl> "or
> "*h_lat_7.ncl <http://www.ncl.ucar.edu/Applications/Scripts/h_lat_7.ncl>*"
> or "*vector_5.ncl
> <http://www.ncl.ucar.edu/Applications/Scripts/vector_5.ncl>*" or any
> other?*
> *
> <http://www2.mmm.ucar.edu/wrf/OnLineTutorial/Graphics/NCL/Examples/CROSS_SECTION/wrf_CrossSection4.ncl>*
> Please give me some guidance.
>
>
>
>
>
>
>
>
>
> Many thanks in advance
>
> Regards
>
> Yan
>
> Shanghai Institute of Meteorology,China.
>
>
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