SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...
SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...
SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...
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Y orientation<br />
Chapter 4 Temporal stability of soil moisture and its application in model result validation<br />
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Fig. 4.1. Demonstration of sample grids in the experimental site (example for UG 79). Each<br />
site has an area of 105 m×135 m. Sampling points are spaced every 15 m with a subgrid<br />
spacing of 5 m (Hollow circles donate the field long-term monitoring positions).<br />
Time stability<br />
1985):<br />
δ<br />
δ<br />
i j<br />
i j = ,<br />
,<br />
The mean relative difference (MRD) is expressed as follows (Vachaud et al.,<br />
S − S<br />
1<br />
S<br />
m<br />
i = ∑ m j=<br />
1<br />
j<br />
δ<br />
j<br />
i,<br />
j<br />
where S i,<br />
j is soil moisture at location i (1-100) and time j, and S j is spatially<br />
mean soil moisture at the same time, and δ i, j is the relative difference of the<br />
spatially mean soil moisture,. Subsequently, the MRD δ i are calculated by<br />
averaged δ i, j over the m sampling dates during the considered period for each<br />
location. Following Grayson and Western (1998), sampling locations are<br />
considered to be time stable when δ i is close to zero and the standard deviation<br />
(1)<br />
(2)<br />
69