# [ncl-talk] A question about the Cape index

Guido Cioni guidocioni at gmail.com
Thu Mar 24 03:53:41 MDT 2016

```Dear Kai,
I already noticed that “problem”, since I worked many times both with the skewt function and the wf_cape_3d function using both model and radiosonde data. The simple answer is YES, depending on the interpolation that you choose you will likely have different results. I think this is related to the fact that, depending on how many points you have in the vertical, the routine that search LCL and LFC will compute a point maybe 300 or 500 m lower/higher and thus you will have a different value of CAPE since it is integrated in the whole column on a different moist adiabatic.. I suggest you to work with the number of interpolation points that give you the same answer that you get also with other software, that’s how I did…

Guido Cioni
http://guidocioni.altervista.org <http://guidocioni.altervista.org/>

> On 24 Mar 2016, at 06:08, 姚凯 <ken3yao at 126.com> wrote:
>
>
> Dear all: <>
>       I’m Kai Yao, a graduate from Nanjing University. Recently, I’m doing some work about convection weather. Your ncl scripts are really helpful, and thanks for everything you have done.
>
>       Now, I’m confused about the script that plots the Skew_T and the Cape index it calculates. I have a data containing pressure, height, temperature, dew point temperature, wind speed and wind direction of 28 levels from 1000hpa to 100hpa in TXT format. The plot shows that the cape index is about 2000, but when after the interpolation, I get the data of 901 levels from 1000hpa to 100hpa, then I redrew the plot, and it shows the cape index is about 800 which is much closer to the calculation from the micaps software.
>
>       I would like to know whether it is the vertical resolution that causes the difference. If so, what is the supposed vertical resolution and the best interpolation method when I want to know the real cape index?
>
>
> Best
>
> Yours
>
> Kai Yao
>
>
>
>
>
> _______________________________________________
> 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/20160324/06d7985d/attachment.html
```