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@ARTICLE{Lorenz:857643,
author = {Lorenz, C. and Montzka, C. and Jagdhuber, T. and Laux, P.
and Kunstmann, H.},
title = {{L}ong-term and high-resolution global time series of
brightness temperature from {C}opula-based fusion of {SMAP}
{E}nhanced and {SMOS} data},
journal = {Remote sensing},
volume = {10},
number = {11},
issn = {2072-4292},
address = {Basel},
publisher = {MDPI},
reportid = {FZJ-2018-06621},
pages = {1842},
year = {2018},
abstract = {Long and consistent soil moisture time series at adequate
spatial resolution are key to foster the application of soil
moisture observations and remotely-sensed products in
climate and numerical weather prediction models. The two
L-band soil moisture satellite missions SMAP (Soil Moisture
Active Passive) and SMOS (Soil Moisture and Ocean Salinity)
are able to provide soil moisture estimates on global scales
and in kilometer accuracy. However, the SMOS data record has
an appropriate length of 7.5 years since late 2009, but with
a coarse resolution of ∼25 km only. In contrast, a
spatially-enhanced SMAP product is available at a higher
resolution of 9 km, but for a shorter time period (since
March 2015 only). Being the fundamental observable from
passive microwave sensors, reliable brightness temperatures
(Tbs) are a mandatory precondition for satellite-based soil
moisture products. We therefore develop, evaluate and apply
a copula-based data fusion approach for combining SMAP
Enhanced $(SMAP_E)$ and SMOS brightness Temperature (Tb)
data. The approach exploits both linear and non-linear
dependencies between the two satellite-based Tb products and
allows one to generate conditional $SMAP_E-like$ random
samples during the pre-SMAP period. Our resulting global
Copula-combined $SMOS-SMAP_E$ (CoSMOP) Tbs are statistically
consistent with $SMAP_E$ brightness temperatures, have a
spatial resolution of 9 km and cover the period from 2010 to
2018. A comparison with Service Soil Climate Analysis
Network (SCAN)-sites over the Contiguous United States
(CONUS) domain shows that the approach successfully reduces
the average RMSE of the original SMOS data by $15\%.$ At
certain locations, improvements of $40\%$ and more can be
observed. Moreover, the median NSE can be enhanced from zero
to almost 0.5. Hence, CoSMOP, which will be made freely
available to the public, provides a first step towards a
global, long-term, high-resolution and multi-sensor
brightness temperature product, and thereby, also soil
moisture},
cin = {IBG-3},
ddc = {620},
cid = {I:(DE-Juel1)IBG-3-20101118},
pnm = {255 - Terrestrial Systems: From Observation to Prediction
(POF3-255)},
pid = {G:(DE-HGF)POF3-255},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000451733800173},
doi = {10.3390/rs10111842},
url = {https://juser.fz-juelich.de/record/857643},
}