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<DIV dir=ltr align=left><SPAN class=309260020-05092020><FONT color=#000080
size=2 face=Arial>Hi Dani,</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=309260020-05092020><FONT color=#000080
size=2 face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN class=309260020-05092020></SPAN><FONT
face=Arial><FONT color=#000080><FONT size=2>><SPAN
class=309260020-05092020>>> </SPAN></FONT></FONT></FONT>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? <SPAN class=309260020-05092020><FONT color=#000080 size=2
face=Arial> </FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=309260020-05092020><FONT color=#000080
size=2 face=Arial>I assume you meant using the July value for each of the
30 years i.e. averaging 30 values for each individual
point.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=309260020-05092020><SPAN
class=309260020-05092020><FONT color=#000080 size=2 face=Arial>You could do that
but it would average out many differences over the timeline of 30 years -
which likely (with assumed climate change) would show smaller differences among
location points as a result. That still might work - depending what you are
trying to do ...</FONT></SPAN></SPAN></DIV>
<DIV dir=ltr align=left><SPAN class=309260020-05092020><SPAN
class=309260020-05092020><FONT color=#000080 size=2 face=Arial>But you could
also average always a decade of data for each point to get 3 SPI averaged values
and determine if that gives you any different results than the first
approach. <BR>Also you need to consider that the SPI already is a summarized
value which shows deviations itself for a long term precipitation series.... So
overall you might be better off to calculate the standard precipitation index
yourself from a given time series of precipitation values. That way you can
calculate for your preferred time period and get only one value , instead
of averaging out already averaged statistical values....
</FONT></SPAN></SPAN></DIV>
<DIV><SPAN class=309260020-05092020><SPAN class=309260020-05092020><FONT
color=#000080 size=2 face=Arial></FONT></SPAN></SPAN> </DIV>
<DIV><SPAN class=309260020-05092020><SPAN class=309260020-05092020><FONT
color=#000080 size=2 face=Arial>You can also take a look at these RASTER data
source <A
href="https://www.chc.ucsb.edu/data/chirps">/www.chc.ucsb.edu/data/chirps</A></FONT></SPAN></SPAN></DIV>
<DIV><SPAN class=309260020-05092020><SPAN class=309260020-05092020><FONT
color=#000080 size=2 face=Arial>I used those for areas in Africa to determine
dry vs. wet years (calculated in R)</FONT></SPAN></SPAN></DIV>
<DIV><SPAN class=309260020-05092020><SPAN class=309260020-05092020><FONT
color=#000080 size=2 face=Arial></FONT></SPAN></SPAN> </DIV>
<DIV><SPAN class=309260020-05092020><SPAN class=309260020-05092020><FONT
color=#000080 size=2 face=Arial>Cheers</FONT></SPAN></SPAN></DIV>
<DIV><SPAN class=309260020-05092020><SPAN class=309260020-05092020><FONT
color=#000080 size=2 face=Arial>Karsten</FONT></SPAN></SPAN></DIV>
<DIV><FONT color=#000080 size=2 face=Arial></FONT><BR> </DIV>
<DIV dir=ltr><BR>
<DIV><BR></DIV></DIV><BR><BR>
<DIV class=gmail_quote>
<DIV class=gmail_attr dir=ltr>On Thu, Sep 3, 2020 at 9:26 PM karsten <<A
href="mailto:karsten@terragis.net">karsten@terragis.net</A>> wrote:<BR></DIV>
<BLOCKQUOTE class=gmail_quote
style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: rgb(204,204,204) 1px solid"><U></U>
<DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#000080 size=2 face=Arial>Hi
Dani.</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#000080 size=2
face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#000080 size=2 face=Arial>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 ...</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#000080 size=2 face=Arial>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...</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#000080 size=2 face=Arial>Another
good tool to look at for such things is the R Program <A
href="https://www.r-project.org/"
target=_blank>https://www.r-project.org/</A> and possibly using Raster
instead of vector data to create stacks of precipitation time
series...</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#000080 size=2
face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#000080 size=2 face=Arial>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.... <BR>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? <BR>This would make sense if you where to find dry
versus wet years e.g. for the growing season of crops or the like ?
<BR>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....</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#000080 size=2
face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#000080 size=2
face=Arial>Cheers</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#000080 size=2
face=Arial>Karsten</FONT></SPAN></DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#000080 size=2
face=Arial></FONT></SPAN> </DIV>
<DIV dir=ltr align=left><SPAN><FONT color=#000080 size=2 face=Arial>
<DIV align=left>
<DIV><SPAN style="FONT-SIZE: 11pt; FONT-FAMILY: Verdana,sans-serif">Karsten
Vennemann<BR></SPAN><SPAN
style="FONT-SIZE: 9pt; FONT-FAMILY: Verdana,sans-serif">Principal<BR><BR><SPAN
style="COLOR: rgb(0,50,100)">Terra GIS LTD<BR>2119 Boyer Ave E
<BR>Seattle, WA 98112<BR>USA <BR><A
title="http://www.terragis.net/
blocked::http://www.terragis.net/"
href="http://www.terragis.net/" target=_blank><FONT
title=http://www.terragis.net/
color=#0000ff>www.terragis.net</FONT></A></SPAN></SPAN><U></U><U></U><U></U></DIV>
<DIV align=left>
<P class=MsoNormal><SPAN
style="FONT-SIZE: 9pt; FONT-FAMILY: Verdana,sans-serif; COLOR: rgb(0,50,100)">Phone
++1 206 905 1711<BR>Fax ++1 925 905
1711</SPAN></P></DIV></DIV></FONT></SPAN></DIV><BR>
<DIV lang=en-us dir=ltr align=left>
<HR>
<FONT size=2 face=Tahoma><B>From:</B> Qgis-us-user [mailto:<A
href="mailto:qgis-us-user-bounces@lists.osgeo.org"
target=_blank>qgis-us-user-bounces@lists.osgeo.org</A>] <B>On Behalf Of
</B>Dani Varghese<BR><B>Sent:</B> Thursday, September 03, 2020
03:14<BR><B>To:</B> <A href="mailto:qgis-us-user@lists.osgeo.org"
target=_blank>qgis-us-user@lists.osgeo.org</A><BR><B>Subject:</B>
[Qgis-us-user] Standard precipitation index interpolation<BR></FONT><BR></DIV>
<DIV></DIV>
<DIV dir=ltr>Dear All
<DIV><BR></DIV>
<DIV>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.</DIV>
<DIV><BR></DIV>
<DIV>Best</DIV>
<DIV>Dani<BR clear=all>
<DIV>
<DIV dir=ltr>
<DIV dir=ltr><BR>
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