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Y. Liu, R. Parinussa, W. Dorigo, R. De Jeu, W. Wagner, A. Van Dijk, M. McCabe, J. Evans:
"Developing an improved soil moisture dataset by blending passive and active microwave satellite-based retrievals";
Hydrology and Earth System Sciences, 15 (2011), 425 - 436.

Combining information derived from satellitebased
passive and active microwave sensors has the potential
to offer improved estimates of surface soil moisture at global
scale. We develop and evaluate a methodology that takes advantage
of the retrieval characteristics of passive (AMSR-E)
and active (ASCAT) microwave satellite estimates to produce
an improved soil moisture product. First, volumetric
soil water content (m3 m−3) from AMSR-E and degree of
saturation (%) from ASCAT are rescaled against a reference
land surface model data set using a cumulative distribution
function matching approach. While this imposes any bias
of the reference on the rescaled satellite products, it adjusts
them to the same range and preserves the dynamics of original
satellite-based products. Comparison with in situ measurements
demonstrates that where the correlation coefficient
between rescaled AMSR-E and ASCAT is greater than 0.65
("transitional regions"), merging the different satellite products
increases the number of observations while minimally
changing the accuracy of soil moisture retrievals. These transitional
regions also delineate the boundary between sparsely
and moderately vegetated regions where rescaled AMSR-E
and ASCAT, respectively, are used for the merged product.
Therefore the merged product carries the advantages of better
spatial coverage overall and increased number of observations,
particularly for the transitional regions. The combination
method developed has the potential to be applied
to existing microwave satellites as well as to new missions.
Accordingly, a long-term global soil moisture dataset can be
developed and extended, enhancing basic understanding of
the role of soil moisture in the water, energy and carbon cycles.

http://publik.tuwien.ac.at/files/PubDat_196086.pdf