[ncl-talk] problem about function "trop_wmo"

[Dennis Shea]

One issue is that that when the WMO criteria  for detecting a 'tropopause
break' was not found, the function correctly assigns a values of -999.0.
This should have been returned as an attribute (_FillValue) of the returned
variable. This was not done. A bug report has been submitted: NCL-2730.

---
The fix is 'trivial'. Manually set the value after return.

    ptrop = trop_wmo(ta&level, ta(time|:,lat|:,lon|:,level|:),0,False)
    ptrop at long_name = "tropopause"
    ptrop at units     = ta&level at units
    ptrop at _FillValue= -999.0   <====

---

More important, I think that the order you did the computations should be
altered.

[a] You computed a temperature climatology. Then you computed the
tropopause levels  using the temperature climatology.

[b] I suggest that the tropopause height  for each year-month be computed
first. Then compute the climatology of the tropopause heights.

I made some changes to your code [ :-) ].

[a] calculate_tropopause.ncl_v0: your 'updated' code
[b] calculate_tropopause.ncl: I think this is the better approach

Note: the differences are not 'visually' significant except for Dec.

Good Luck
D

On Thu, Mar 1, 2018 at 8:14 AM, 黄涵 <hedgehogh at pku.edu.cn> wrote:

> Hi all,
>
>   I have been calculating tropopause height recently, but I found the
> results from the function "trop_wmo" is quite strange.
>   Attached are the code of using "trop_wmo" to calculate the tropopause
> height and corresponding images.
>
>   The dataset is from NCEP2, you can download from:
> https://www.esrl.noaa.gov/psd/cgi-bin/db_search/DBSearch.pl?
> &Dataset=NCEP/DOE+AMIP-II+Reanalysis+(Reanalysis-2)+
> Monthly+Averages&Variable=Air+Temperature
>
>   The version of NCL is 6.4.0
>
>   Thank you very much.
>
> Han
>
>
> _______________________________________________
> ncl-talk mailing list
> ncl-talk at ucar.edu
> List instructions, subscriber options, unsubscribe:
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20180303/443b9618/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: calculate_tropopause.ncl
Type: application/octet-stream
Size: 3712 bytes
Desc: not available
URL: <http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20180303/443b9618/attachment.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: calculate_tropopause.ncl_v0
Type: application/octet-stream
Size: 3481 bytes
Desc: not available
URL: <http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20180303/443b9618/attachment-0001.obj>