[ncl-talk] SPI calculation
Dennis Shea
shea at ucar.edu
Fri Nov 30 09:02:40 MST 2018
*Please* read the File IO on netCDF. As noted in the documentation, the
following is the most commonly used approach.
http://www.ncl.ucar.edu/Applications/method_1.shtml
===
*system*
<http://www.ncl.ucar.edu/Document/Functions/Built-in/system.shtml>("/bin/rm
-f SPI.nc") ; remove any pre-existing file
ncdf = *addfile*
<http://www.ncl.ucar.edu/Document/Functions/Built-in/addfile.shtml>("SPI.nc"
,"c") ; open output netCDF file
;===================================================================
; create global attributes of the file (optional)
;===================================================================
fAtt = True ; assign file attributes
fAtt at title = "Standardized Precipitation Index"
fAtt at Conventions = "None"
fAtt at creation_date = *systemfunc*
<http://www.ncl.ucar.edu/Document/Functions/Built-in/systemfunc.shtml>
("date")
*fileattdef*
<http://www.ncl.ucar.edu/Document/Functions/Built-in/fileattdef.shtml>(
ncdf, fAtt ) ; copy file attributes
;===================================================================
; output variables directly; NCL will call appropriate functions
; to write the meta data associated with each variable
;===================================================================
ncdf->SPI = spi ; (len,time,lat,lon)
On Thu, Nov 29, 2018 at 10:29 PM Soma Roy <somaroy892 at gmail.com> wrote:
> Hello Mary,
>
> I just want to know that what is the more efficient way to save the
> variable "spi" as a netcdf for multiple runlen?
>
> Say 3,6,9 and 12 or 12 and 24 as mentioned in the spi_2.ncl script.
>
> I want to save all runlen in a single netcdf file in single run time.
>
> Please kindly inform me.
>
> Thanking you,
> Soma
>
> On Thu, Nov 29, 2018, 20:12 Dennis Shea <shea at ucar.edu wrote:
>
>> I do not understand: *"197207 with 3 month running avg"*
>>
>>
>> If you used:
>>
>>
>>
>> *runlen = (/ 12, 24 /) *
>>
>> and your source array is dimensioned:
>> *(time,lat,lon) ==> (492,129,135)*then your SPI variable should be
>>
>>
>>
>> *[len | 2] x [time | 492] x [lat | 129] x [lon | 135]*and your source array is dimensioned:
>> * (time,lon,lat) ==> (492,135,129)*then your SPI variable should be
>>
>>
>>
>>
>>
>>
>> *[len | 2] x [time | 492] x [lon | 135] x [lat | 129] --- 0 1 2 3---*
>>
>> *IF* you want to perform a 3-month running average of the 12 and 24 run-lengths
>>
>> nrun = 3
>> opt = ? ; read documentation
>> tdim = 1 ; time dimension
>> spi3= *runave_n_Wrap* <http://www.ncl.ucar.edu/Document/Functions/Contributed/runave_n_Wrap.shtml> (spi, nrun, tdim, opt)
>>
>> *printVarSummary*(spi3)
>>
>> ========
>>
>>
>>
>>
>>
>> On Thu, Nov 29, 2018 at 1:15 AM Soma Roy <somaroy892 at gmail.com> wrote:
>>
>>> Hello Mary,
>>>
>>> I save the data of 'spi' as netcdf file.
>>>
>>> Where dimension of the data is like below;
>>> spi(135x129x492) ; (lon, lat, spi values)
>>>
>>> Now my question is if I want to select 197207 with 3 month running avg.
>>> Then how to select those indices from 3rd dimension of the matrix "spi"?
>>>
>>> Start yr is 1970.
>>>
>>> Please kindly inform me.
>>>
>>> Thanking you,
>>> Soma
>>>
>>> On Thu, Nov 29, 2018, 12:39 Oluwaseun Ilori <wilseun at gmail.com wrote:
>>>
>>>> Good day, please could you assist with the correct script of the spi
>>>> calculation, I'm having problem listing the result of the one I'm doing to
>>>> text file for further analysis on ArcGis.
>>>>
>>>> Thanks
>>>>
>>>> On Thu, Nov 29, 2018, 7:47 AM Soma Roy <somaroy892 at gmail.com wrote:
>>>>
>>>>> I fixed the issue. Please ignore my last mail.
>>>>>
>>>>> Soma
>>>>>
>>>>> On Thu, Nov 29, 2018, 11:07 Soma Roy <somaroy892 at gmail.com wrote:
>>>>>
>>>>>> Hello Mary,
>>>>>>
>>>>>> I am using the attached script. Modified it as per your hints. But
>>>>>> getting some errors at run time.
>>>>>>
>>>>>> printVarSummary of the data is as follows;
>>>>>> Variable: prc
>>>>>> Type: double
>>>>>> Total Size: 73560960 bytes
>>>>>> 9195120 values
>>>>>> Number of Dimensions: 3
>>>>>> Dimensions and sizes: [time | 528] x [lat | 129] x [lon | 135]
>>>>>> Coordinates:
>>>>>> time: [ 360..1068]
>>>>>> lat: [ 6.5..38.5]
>>>>>> lon: [66.5.. 100]
>>>>>> Number Of Attributes: 3
>>>>>> _FillValue : -999
>>>>>> long_name : GRIDDED RAINFALL
>>>>>> missing_value : -999
>>>>>> : min=0 max=222.9121398925781
>>>>>>
>>>>>> I am getting the following errors;
>>>>>> fatal:Dimension sizes of left hand side and right hand side of
>>>>>> assignment do not match
>>>>>> fatal:["Execute.c":8640]:Execute: Error occurred at or near line 47
>>>>>> in file spi_2.ncl
>>>>>>
>>>>>> fatal:NclOneDValGetClosestIndex: Non-monotonic coordinate value being
>>>>>> used, can't complete coordinate subscript
>>>>>> fatal:Could not obtain coordinate indexes, unable to perform subscript
>>>>>> fatal:["Execute.c":8640]:Execute: Error occurred at or near line 82
>>>>>> in file spi_2.ncl
>>>>>>
>>>>>> Please kindly inform me how to correct it.
>>>>>>
>>>>>> Thanking you,
>>>>>> Soma
>>>>>>
>>>>>>
>>>>>> On Thu, Nov 29, 2018 at 9:51 AM Soma Roy <somaroy892 at gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Thank you very much.
>>>>>>>
>>>>>>> Soma
>>>>>>>
>>>>>>> On Thu, Nov 29, 2018, 02:28 Mary Haley <haley at ucar.edu wrote:
>>>>>>>
>>>>>>>> Soma,
>>>>>>>>
>>>>>>>> The spi_2.ncl script shows you how to calculate the yyyymm variable:
>>>>>>>>
>>>>>>>> year = yyyymm/100
>>>>>>>> yrStrt = year(0)
>>>>>>>> yrLast = year(ntim-1)
>>>>>>>> nyear = yrLast-yrStrt+1
>>>>>>>> yyyymm = yyyymm_time(yrStrt, yrLast, "integer")
>>>>>>>>
>>>>>>>> You don't need the "date" or "yyyymm" arrays, because you already
>>>>>>>> have the year information. Use ispan to generate the "year" array and now
>>>>>>>> you can get your yyyymm and yrfac values as needed:
>>>>>>>>
>>>>>>>> year = ispan(1970,2010,1)
>>>>>>>> ntim = dimsizes(year)
>>>>>>>> yrStrt = year(0)
>>>>>>>> yrLast = year(ntim-1)
>>>>>>>> nyear = yrLast-yrStrt+1
>>>>>>>> yyyymm = yyyymm_time(yrStrt, yrLast, "integer")
>>>>>>>> yrfrac = (/ yyyymm_to_yyyyfrac(yyyymm, 0.0) /)
>>>>>>>>
>>>>>>>> --Mary
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> On Wed, Nov 28, 2018 at 1:05 PM Soma Roy <somaroy892 at gmail.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> Thank you very much for the hint.
>>>>>>>>> I will check it.
>>>>>>>>>
>>>>>>>>> But mannualy we can't set the "date" range in the script without
>>>>>>>>> using CDO?
>>>>>>>>>
>>>>>>>>> Please kindly inform me.
>>>>>>>>>
>>>>>>>>> Thanking you,
>>>>>>>>> Soma
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Thu, Nov 29, 2018, 01:28 Guilherme Martins <jgmsantos at gmail.com
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> I don't know if you use climate data operators or cdo software.
>>>>>>>>>>
>>>>>>>>>> You can set the data in your file.
>>>>>>>>>>
>>>>>>>>>> Exemple
>>>>>>>>>>
>>>>>>>>>> cdo settaxis,1970-01-01,00:00:00,1mon input.nc output.nc
>>>>>>>>>>
>>>>>>>>>> Guilherme.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Em qua, 28 de nov de 2018 16:35, Soma Roy <somaroy892 at gmail.com
>>>>>>>>>> escreveu:
>>>>>>>>>>
>>>>>>>>>>> Hello,
>>>>>>>>>>>
>>>>>>>>>>> I am trying to calculate standadize precipitation index using
>>>>>>>>>>> monthly gridded dataset.
>>>>>>>>>>>
>>>>>>>>>>> Dimension of data is like below;
>>>>>>>>>>> Rainfall(12x41) (months x years).
>>>>>>>>>>>
>>>>>>>>>>> I am using the script from the below link;
>>>>>>>>>>> https://www.ncl.ucar.edu/Applications/Scripts/spi_2.ncl
>>>>>>>>>>>
>>>>>>>>>>> But in my dataset there is no variable as "date".
>>>>>>>>>>>
>>>>>>>>>>> Can we manually set the date range inside the script?
>>>>>>>>>>>
>>>>>>>>>>> I am using rainfall dataset for 1970-2010.
>>>>>>>>>>>
>>>>>>>>>>> Please kindly inform me how we can modify it over the same
>>>>>>>>>>> script.
>>>>>>>>>>>
>>>>>>>>>>> Thanking you,
>>>>>>>>>>> Soma
>>>>>>>>>>> _______________________________________________
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