[Qgis-us-user] Standard precipitation index interpolation

Dani Varghese danivarghes at gmail.com
Sat Sep 5 12:41:32 PDT 2020

Hi Karsten

Thanks for your reply, please accept my apologies for the late reply.

like you said, if i focus on the month of july ( for example)  can i take
the average SPI values for  all the 30 years to denote/represent a station?


On Thu, Sep 3, 2020 at 9:26 PM karsten <karsten at terragis.net> wrote:

> Hi Dani.
> well generally for each point in time you would need run the kriging
> process separately (each monthly data set for all points counts as one), so
> that would be 30*12 = 360 times ...
> So a lot of runs ...  if you really wanted to do that best would be to run
> that as a batch process or script it in python for the processing toolbox...
> Another good tool to look at for such things is the R Program
> https://www.r-project.org/ and possibly using Raster instead of vector
> data to create stacks of precipitation time series...
> However, if I where you, I might step back first and determine what
> results you would like to get or which comparisons you would want to
> make....
> I don't know what you are after - but for example would it make more sense
> to look at the differences of one month over the 30 years time sequence to
> detect changes in precipitation?
> This would make sense if you where to find dry versus wet years e.g. for
> the growing season of crops or the like ?
> Let's say if July was interesting for you then you could run the
> interpolations for July of each year and that way get a time sequences you
> can look at to dervive your conclusions from....
> Cheers
> Karsten
> Karsten Vennemann
> Principal
> Terra GIS LTD
> 2119 Boyer Ave E
> Seattle, WA  98112
> www.terragis.net
> Phone ++1 206 905 1711
> Fax      ++1 925 905 1711
> ------------------------------
> *From:* Qgis-us-user [mailto:qgis-us-user-bounces at lists.osgeo.org] *On
> Behalf Of *Dani Varghese
> *Sent:* Thursday, September 03, 2020 03:14
> *To:* qgis-us-user at lists.osgeo.org
> *Subject:* [Qgis-us-user] Standard precipitation index interpolation
> Dear All
> I  had SPI (Standard precipitation index) values for 1000 stations (30
> years monthly data for each station) . I needed to perform the
> interpolation method ( kriging). What confuses me is that each
> station/point has 30 years of monthly data ranging from +2 to -2, Can
> anyone suggest to me how to interpolate these values, thanks  in advance.
> Best
> Dani
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