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R. De Jeu, D. Miralles, M. Van Marle, W. Dorigo, W. Wagner, Y. Liu:
"Validation of annual variations in satellite based transpiration and soil moisture using tree ring data";
Talk: WIRADA Science Symposium, Melbourne, Australia; 2011-08-01 - 2011-08-05; in: "WIRADA Science Symposium", (2011), 5 pages.

Recently, a multi-decadal dataset of satellite based soil moisture and the
evaporative flux have been developed. This dataset is based on different satellite
observations and has been validated extensively with in situ observations and models.
However, these validation studies have always been applied on short periods but
never evaluated long term variations (> 10 years). This study aims on the use of tree
ring data for annual variation validation. As a first test case, the Los Lobos Creek
site in central California was selected with a 21 year record (1984-2004) of tree
ring width data from 27 blue oak trees (Quercus Douglasii). The dominant tree ring
signal was retrieved by applying an empirical orthogonal Function (EOF) analysis
on the normalized tree ring widths resulting in one dominant signal that described
the temporal behaviour of the 27 trees for 80%. This signal was then compared to
soil moisture and transpiration rates from the satellite based Global Land surface
Evaporation: the Amsterdam Methodology (GLEAM) Model. The analysis revealed
a strong relationship between annual tree ring width and transpiration in June
(R=0.79) and soil moisture in April (R=0.82). These first preliminary results give us
confidence in the reliability of the annual variations of the different products. Both the
soil moisture and transpiration fluxes capture the extreme years as given by the tree
ring width. Although this is still based on one site we believe that data from the tree
ring data bank can have a strong potential as a validation tool for long record satellite
datasets. However, further research on other sites is still necessary to confirm the
consistency of such an approach.

Evaporation; soil moisture; tree ring data; satellite data

http://publik.tuwien.ac.at/files/PubDat_201886.doc