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

Rashed Mahmood rashidcomsis at gmail.com
Tue Sep 10 05:08:14 MDT 2019 

I meant to:  olr_aave(n)

On Tue, Sep 10, 2019 at 1:07 PM Rashed Mahmood <rashidcomsis at gmail.com>
wrote:

> 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
>>>>>>
>>>>>>
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