# [ncl-talk] Extracting Time Series From WRF Output

Dennis Shea shea at ucar.edu
Thu Apr 23 20:42:07 MDT 2020

```The syntax *{...} *can ONLY be used with a special type of variable called
a *coordinate variable [CV]*
A CV is a one where the variable name *and* the dimension names are
identical.
eg:  lat(lat),  lon(on), latitude(latitude) .   etc

The WRF variables containing the geographic coordinates are two-or-three
dimensions.
XLAT ( Time, south_north, west_east )
XLONG(...)

Hence, they are not CVs.
Use the *getind_latlon2d *f
<http://www.ncl.ucar.edu/Document/Functions/Contributed/getind_latlon2d.shtml>unction.

lat2d = f[0]->XLAT(0,:,:)
lon2d = f-[0]>XLONG(0,:,:)

printVarSummary(lat2d)
printMinMax(lat2d, 0)
printMinMax(lon2d, 0)

lat   = (/  -18  /)   ; user specified coordinate pairs
lon   = (/ -30  /)
; return 2d subscripts
nm = *getind_latlon2d* (lat2d,lon2d, lat, lon)
print(nm)

x = a[:]->T2(:,n,m)
y = a[:]->V(:,{2},n,m)

On Thu, Apr 23, 2020 at 4:31 PM zilore mumba via ncl-talk <ncl-talk at ucar.edu>
wrote:

> Hello once again.
> I am hoping someone may have a script which they can share,or correct my
> code below where I am attempting to extract a time series. From the
> assistance I got a few days ago, I am able to write values at a given
> location at the surface T2) and a a fixed level (V). Though I am getting
> several warnings, firstly
>
> Dimension (west_east) and (south_north) of file
> (wrfout_d01_2020-02-03_00:00:00) does not have an associated coordinate
> variable
> and
>
> warning:Invalid stride: stride must be positive non-zero integer
>
> But my problem is that I am not able to select the forecast time of the
> series, i.e e.g. daily time series of the forecast at 0600UTC. Currently I
> am printing 484 values from 12 files each with forecast range of 120H (5
> days). I am not able to tell which value corresponds to what forecast range
> and why they are 484.
> Is there a way to select for x and y (in the code below) the specific time
> step for the time series?
>
> Help will be appreciated
>
> begin
>   files = systemfunc("ls -1 data/wrfout_d01_2020*") + ".nc"
>
>   ListSetType (a, "cat")          ; concatenate (=default)
>
>   varnames = getfilevarnames(a[0]) ; get var names from the first file
>   print(varnames)
>
>   x = a[:]->T2(:,{-18},{30})
>   y = a[:]->V(:,{2},{-18},{30})
>
>   asciiwrite("Lusaka.txt", x)
>   asciiwrite("Lusaka2.txt", y)
>
> end
>
>
>
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