[ncl-talk] Filtering dates of a netcdf file (include number of gridpoints as additional criteria)

Rashed Mahmood rashidcomsis at gmail.com
Tue Sep 10 05:07:24 MDT 2019 

Since your *olr_aave *variable contains multiple times, the error is
expected. You need to change in the if statement, from olr_aave to
old_aave(n).
See attached.

Good luck!

On Tue, Sep 10, 2019 at 7:13 AM Lyndz <olagueralyndonmark429 at gmail.com>
wrote:

> Dear Rashed and NCL experts,
>
> I tried adding another condition on the above script:
> (a) OLR < 240 W/m2 and the number of grid points with rainfall above 0
> mm/day should be at least 10%.
>
>
> Like this:
>      olr_threshold = 240
>      olr_aave=wgt_areaave_Wrap(olr_region,1.0,1.0,0)
>
>
>
>
>
> *     if((perc.gt.req_perc) .and. (olr_aave.lt.olr_threshold))then
> ids_valid(n) = n       else        print(n+ " ... pertange of grid points
> is less than 80% = > "+perc)      end if*
>
> I am getting the following errors:
>
>
> *fatal:Conditional statements (if and do while) require SCALAR logical
> values, see all and any functionsfatal:["Execute.c":8637]:Execute: Error
> occurred at or near line 66 in file date_filter.ncl*
>
> Line 66 is the end if part of the script.
>
> I uploaded the olr data here:
> https://www.dropbox.com/s/ufdzfk4ky2gfmz8/olr_1979_AMJ.nc?dl=0
>
> and the script is attached in this email.
>
> Any suggestions on how to do this correctly in NCL?
> I'll appreciate any help.
>
> Sincerely,
> Lyndz
>
>
> On Tue, Sep 10, 2019 at 1:28 PM Lyndz <olagueralyndonmark429 at gmail.com>
> wrote:
>
>> Dear Rashed,
>>
>> Thank you so much for your help!
>> This works. I just need to tweak the threshold.
>>
>> Sincerely,
>> Lyndz
>>
>>
>> On Tue, Sep 10, 2019 at 3:15 AM Rashed Mahmood <rashidcomsis at gmail.com>
>> wrote:
>>
>>>
>>> I think your condition (b) would be the only condition that is needed,
>>> since if condition b is true then condition "a" must be true. So, it
>>> appears that you do not need condition "a".
>>> For example, if 80% of grid points for a given time and region has
>>> precipitation values greater than zero, then for that particular time and
>>> region area average value will always be above zero.
>>>
>>> So I modified your script (see attached) and added a loop to find out
>>> those time steps:
>>>
>>> ; condition b:
>>>
>>>    dims      = dimsizes(rain_region)
>>>    ntime     = dims(0)
>>>    tot_point = dims(1)*dims(2)*1.
>>>    ids_valid = new(ntime,integer)
>>>    req_perc  = 80. ; 40.
>>>
>>>    do n=0,ntime-1
>>>       tmp_rain = rain_region(n,:,:)
>>>       oneD     = ndtooned(tmp_rain)
>>>       npnts    = 1.*dimsizes(ind(oneD.gt.0))
>>>       perc     = 100.*(npnts/tot_point)
>>>
>>>       if(perc.gt.req_perc)then
>>>         ids_valid(n) = n
>>>        else
>>>         print(n+ " ... pertange of grid points is less than 80% = >
>>> "+perc)
>>>       end if
>>>       delete([/tmp_rain,oneD,npnts,perc/])
>>>    end do
>>>
>>>    if(.not.all(ismissing(ids_valid)))then
>>>        n_thres  = ids_valid(ind(.not.ismissing(ids_valid)))
>>>    else
>>>      print(" No valid time step for the specified condition: Exiting")
>>>     exit
>>>    end if
>>>
>>>
>>> You need to play with the variable    req_perc  = 80., by changing to
>>> lower values such 40. or anything else to see how it works. In your data
>>> file no time step would satisfy the 80% condition.
>>> hope that helps.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Mon, Sep 9, 2019 at 9:20 AM Lyndz <olagueralyndonmark429 at gmail.com>
>>> wrote:
>>>
>>>> Hi,
>>>>
>>>> This includes all time steps. But, in the file that I sent, I want to *count
>>>> the number of gridpoints in each time step* with rainfall above 0. I
>>>> have to include this in the time filter. Specifically, these two
>>>> conditions: the area averaged rainfall is > 0 *and* at least 80% of
>>>> the total gridpoints have rainfall > 0.
>>>>
>>>> Over the region I specified (rain_region), it has 40 x 30 x 10 (ntim x
>>>> nlat x nlon).
>>>> The above command you gave results to 5830.
>>>> I can get a similar result by just doing this: a =
>>>> num(rain_region.gt.0)
>>>>
>>>> Sincerely,
>>>>
>>>>
>>>> On Tue, Sep 10, 2019 at 12:02 AM Rashed Mahmood <rashidcomsis at gmail.com>
>>>> wrote:
>>>>
>>>>> Yes, there can be several ways of counting grid points with rainfall
>>>>> above 0:
>>>>>
>>>>> e.g. say your variable name is "precp"
>>>>>
>>>>> oneD = ndtooned(precip)
>>>>>
>>>>>  nVal = dimsizes(ind(oneD.gt.0))
>>>>>
>>>>> nVal is the number of time precip is greater than 0. Does this makes
>>>>> sense, let me know if does not.
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Mon, Sep 9, 2019 at 11:36 AM Lyndz via ncl-talk <ncl-talk at ucar.edu>
>>>>> wrote:
>>>>>
>>>>>> Dear NCL experts,
>>>>>>
>>>>>> I would like to filter the dates in a NetCDF file when the following
>>>>>> conditions are met:
>>>>>> (a) Area averaged rainfall is greater than 0.
>>>>>>
>>>>>> Area:
>>>>>>   latS = 12.5
>>>>>>   latN = 20.0
>>>>>>   lonL = 120.0
>>>>>>   lonR = 122.5
>>>>>>
>>>>>> (b) At least 80% of the grid points within the specified area
>>>>>> satisfies (a).
>>>>>>
>>>>>> Attached in this email is the script that I am currently working on.
>>>>>> The sample data can be accessed here:
>>>>>> https://www.dropbox.com/s/spfnwb4rhwjo90o/aphro_1979_AMJ.nc?dl=0
>>>>>>
>>>>>>
>>>>>> *[Problem]*
>>>>>> I was able to do the condition (a) but is there a way to count the
>>>>>> number of grid points with rainfall above 0 over the specified region? How
>>>>>> can I add this as another condition for the date filter?
>>>>>>
>>>>>> The time filter is like this:
>>>>>>
>>>>>>   rain_threshold = 0
>>>>>>   rain_aave=wgt_areaave_Wrap(rain_region,1.0,1.0,0)
>>>>>>   printVarSummary(rain_aave)
>>>>>>   n_thres  = ind(rain_aave .gt. rain_threshold) ;time indices
>>>>>>   print(n_thres)
>>>>>>   print("=====")
>>>>>>
>>>>>> I'll appreciate any guidance about this.
>>>>>>
>>>>>> Sincerely,
>>>>>> Lyndz
>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> 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/20190910/4b23263a/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: date_filter.ncl
Type: application/octet-stream
Size: 3278 bytes
Desc: not available
URL: <http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20190910/4b23263a/attachment.obj>

More information about the ncl-talk mailing list