Global Land Data Assimilation System (GLDAS) is often used as a test bed for innovative modeling and assimilation capabilities. So its reliability is very important, the validation and the evaluation of product from GLDAS often use in-situ observations. Now remote sensing has been an important observation source, but satellite observations have not directly relation with the output of GLDAS, their relationships are so complex even fuzzy with many parameters. This study analyzed the reliability of soil moisture and land surface temperature simulated by GLDAS using Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) data for the periods of one year based on fuzzy comprehensive evaluation theory, Results demonstrate that both of them are relatively believable, and the land surface temperature is more reliable than the soil moisture.
Forest covers about 30% of earth surface, which plays an important role in global forecast and carbon cycle.
Monitoring forest biomass, and retrieving soil moisture at forest area, are the main goals of most passive microwave
sensors on satellite missions. L-band is the most sensitive frequency among all the frequencies due to its good penetration
ability. Because of its variety of the size of scattering components, the complicated structures and species of forest, it is
difficult to describe the scattering and attenuation characters of forest in modeling microwave emission at forest area.
In this paper, we studied the emissivity and transmissivity of deciduous forest at L(1.4GHz) by model simulation and
field experiment. The microwave emission model was based on Matrix-Doubling algorithm. The comparison between
simulated emissivity and measured data collected during an experiment at Maryland, USA in 2007 was good.
Since theoretical model like Matrix-Doubling is too complicated to be used in retrial application, we mapped the
results of Matrix-Doubling to a simple 0th-order model, also called ω-τ model, by setting the simulated emissivity to be the
emissivity of 0th-order model at the same environment, which 2 unknown variables---opacity τ and effective single
scattering albedo ω need to be determined.
To valited τ (transmissivity of forest) simulated by Matrix-Doubling, we took an deciduous forest experiment by an L
band microwave radiometer under trees at JingYueTan area, Changchun, Jilin Province in April to June in 2014. Thus the ω
of forest can be determined.
The matching results are presented in this paper. The relationship between LAI and forest microwave characters are
discussed.
This paper demonstrates a study to simulate brightness temperature (BT) between 1-100GHz on the Tibetan plateau area
using a coupled land-canopy-atmosphere model at clear-sky conditions.These simulations were compared with
Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) measurements on May 1, 2003. A
sensitivity study was also carried out to access the relative contributions of the main parameters (particularly the
roughness and vegetation water content). Difference between simulated and measured TB were analyzed, discriminating
possible issues either linked to the radiative transfer model or due to the land surface parameters.
Global brightness temperature simulations were performed at 0.25 degree resolution both including the atmospheric
effect and pixel heterogeneity in wide wave band. For surfaces such as snow, deserts, and vegetation, volumetric
scattering was calculated using a two-stream radiative transfer approximation. The reflection and transmission at the
surface-air interface and lower boundary were derived by modifying the Frenel equations and QP model to account for
cross-polarization. Several models were utilized to compute the optical parameters for the medium. Global Land Data
Assimilation Systems (GLDAS) provided time series of the main input variables. These simulations were compared with
Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) measurements in January, April, July,
and September 2003, including both the spectral and temporal variations. A sensitivity study was also carried out to
access the relative contributes of the main parameters (particularly the roughness and soil moisture). Difference between
simulated and measured TBs were analyzed, discriminating possible issues either linked to the radiative transfer model
or due to land surface parameters .
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