[R-sig-Geo] Daily precipitation kriging
h.greatrex at reading.ac.uk
Wed Aug 19 12:56:33 CEST 2009
I think I have an answer to your problem. Maybe you're getting the
errors because you're inputting data at more than one time step into the
Also there might be a slightly more elegant way of approaching the
Normally, you would krige at one point in time -(i.e. the structure of
gold ore doesn't change over time) However, unless you have an extremely
dense raingauge network, you're not going to obtain a reasonable
variogram doing this for daily rainfall. Also it's reasonable to assume
that rainfall on different days has the same spatial structure over a
short enough time period (i.e. all the days in January). So you can pool
the data together and make a 'January' variogram and krige using that.
At Reading, we do this through using a climatological variogram.
Basically, you 'normalise' each day's rainfall by dividing through by
the total daily variance to create the variogram, then at the end of the
kriging process you remultiply each day's estimate to give you final
estimates. The method is explained more briefly in Teo & Grimes,
"Stochastic Modelling of rainfall from satellite data", J. Hydrology
346, 2007. We also have another publication on 'Geostatistical analysis
of rainfall' which has just been accepted for publication in a special
edition of Geographical Analysis on ‘Geostatistical Methods in
Geography', which should explain the process in detail.
I've created a set of self contained R scripts to do the entire process
(plus an extensive user manual which should explain things further).
I'll send it to you as a separate e-mail to stop large attachments
getting sent to everyone on the list.
I'm aware this e-mail hasn't answered your specific coding problems, but
I hope it helps!
Helen Greatrex (PhD Student)
Department of Meteorology
University of Reading
PO Box 243
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