[ncl-talk] I might find some bugs about calculation of wet-bulb temperature

[Mary Haley]

Hi,

I do not know the answer to your second question about the correct units of
"p" for wrf_wetbulb, but wrfhelp should be able to answer that.

The documentation for "wrf_user_getvar" says to use "tw", but it should be
"twb".  I don't know if this is an error in the documentation or the
WRFUserARW.ncl script, but I've updated the documentation to reflect this.

--Mary


On Tue, Dec 23, 2014 at 12:26 AM, Mr.J <shengxuan_ji at sina.com> wrote:

> Dear Sir / Madam
>
> Thank you for your hard working on the development of NCL software. I can
> easily manipulate the met data and professional plots now.
>
>
> During my usage of wrf related functions, I found a bug, which is about
> calculation of wet-bulb temperature. I noticed that after the version
>
> 6.2.0, the Wet bulb temperature is available to be calculated in one step
> by wrf_user_getvar(file,"tw",time). However, when I used the way
>
> to get it, I got a error massage:
>
>
> fatal:["Execute.c":6321]:variable (tw) is not in file (nc_file)
>
>
> I think it means the function "wrf_user_getvar" is trying to get the "tw"
> variable from the wrfout file instead of calculating the diagnostics "we-
>
> t bulb temperature".
>
>
> Secondly, I tried to use the other way to calculate the "Tw" by using the
> function " wrf_wetbulb ",  I also found some incorrect stuffs.On the
>
> description page of the "wrf_wetbulb", it shows that we need to put
> argument "p" in mb (hPa). However in the given example 1, the script
>
> uses "p   = wrf_user_getvar(a,"p",0)" to get the pressure. It may be
> wrong, because the unit is Pa calculating in this way. All in all, what unit
>
> should I use for the pressure. (Please refer to test_scrpit1.ncl)
>
>
> Thirdly, in the description page of function "wrf_wetbulb", the unit of
> return value is [C]. When I get the results, these values are larger than
>
> 250. So, I am confused about the return value unit. Is it [C] or [K]?
> (Please refer to test_script2.ncl)
>
>
> The attachments are my test scripts, please check them. The wrfout file is
> too large to put it on a website, you may find
>
> another one to try the scripts.
>
>
> My system details:
>
> *ncl version: **6.2.0*
>
> *( I also tried the vesion 6.2.1, the results are the same.)*
>
>
> *uname -a *
>
> *Linux nowcast 2.6.32-358.el6.x86_64 #1 SMP Tue Jan 29 11:47:41 EST 2013
> x86_64 x86_64 x86_64 GNU/Linux*
>
>
> *gcc --version*
>
> *gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-3)*
>
> *Copyright (C) 2010 Free Software Foundation, Inc.*
>
>
> *cat /etc/redhat-release*
>
> *Red Hat Enterprise Linux Server release 6.4 (Santiago)*
>
>
>
> To be honest, I am not sure whether these are bugs or not. Please help me
> to deal with these questions. Hope your reply ASAP. Thank
>
> you very very much!
>
>
> Yours sincerely,
>
> Shengxuan JI
> --------------------------------
>
>
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