[ncl-talk] 2ND TIME POST: add polyline with gsn_csm_pres_hgt_vector

[Dennis Shea]

I think the U.S. Standard atmosphere is used.
   http://www.ncl.ucar.edu/Document/Functions/Built-in/stdatmus_z2tdp.shtml

You can input 'z' and get the corresponding 'p'      also ... 't' and 'density'

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The actual code used is attached.



On Thu, Aug 20, 2015 at 2:44 PM, Zhifeng Yang <yangzf01 at gmail.com> wrote:
> Hi Dennis,
> Yes, you are right Height is just added as the label for right-Y axis, not
> like gsn_csm_xy2.ncl. I searched "gsn_csm_pres_hgt_vector" the code
> (gsn_csm.ncl). However, I did not find how it calculates the height using
> pressure value. Do you know who wrote this code (gsn_csm.ncl) or do you know
> who is more familiar with this code? Thank you,
>
> Zhifeng
>
> On Thu, Aug 20, 2015 at 10:31 AM, Dennis Shea <shea at ucar.edu> wrote:
>>
>> " I am not sure how to add a polyline using the right y-axis"
>>
>> I did not write this so I am guessing:
>>
>> I think the right-y-axis ("Height") is not a y-coordinate. Rather,
>> 'under-the-hood,' a function (say) Height = f(pressure) was used to
>> estimate the heights for labeling purposes.
>>
>> if the x-axis is (say, lat or lon), and you have:
>>       polyline_values = f(x,height)
>> then you may have to recast the 2nd line in terms of pressure and add
>> like the 1st polyline
>>
>>
>>
>>
>>
>> On Wed, Aug 19, 2015 at 2:16 PM, Zhifeng Yang <yangzf01 at gmail.com> wrote:
>> > Hi
>> >
>> > Sorry for posting this problem again. Since I haven't received reply
>> > from my
>> > previous post, I promote it by myself.
>> >
>> > I want to add a polyline on a image generated by
>> > gsn_csm_pres_hgt_vector,
>> > and the y value of the polyline is height, which is the right y-axis. I
>> > can
>> > add a polyline using the left y-axis, but I need to reverse pressure to
>> > plot
>> > a polyline. I don't know how to plot a polyline with reversed y-axis.
>> > Most
>> > important, I am not sure how to add a polyline using the right y-axis.
>> > Do
>> > you know how to fix it?
>> > Thank you.
>> >
>> > Best,
>> > Zhifeng
>> >
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>
>
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