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Parameter Optimization of a Discrete Scattering Model by Integration of Global Sensitivity Analysis Using SMAP Active and Passive Observations
- Source :
- IEEE transactions on geoscience and remote sensing, 57(2):8457483, 1084-1099. IEEE
- Publication Year :
- 2019
-
Abstract
- Active and passive microwave signatures respond differently to the land surface and provide complementary information on the characteristics of the observed scenes. The objective of this paper is to explore the synergy of active radar and passive radiometer observations at the same spatial scale to constrain a discrete radiative transfer model, the Tor Vergata (TVG) model, to gain insights into the microwave scattering and emission mechanisms over grasslands. The TVG model can simultaneously simulate the backscattering coefficient and emissivity with a set of input parameters. To calibrate this model, in situ soil moisture and temperature data collected from the Maqu area in the northeastern region of the Tibetan Plateau, interpolated leaf area index (LAI) data from the Moderate Resolution Imaging Spectroradiometer LAI eight-day products, and concurrent and coincident Soil Moisture Active Passive (SMAP) radar and radiometer observations are used. Because this model needs numerous input parameters to be driven, the extended Fourier amplitude sensitivity test is first applied to conduct global sensitivity analysis (GSA) to select the sensitive and insensitive parameters. Only the most sensitive parameters are defined as free variables, to separately calibrate the active-only model (TVG-A), the passive-only model (TVG-P), and the active and passive combined model (TVG-AP). The accuracy of the calibrated models is evaluated by comparing the SMAP observations and the model simulations. The results show that TVG-AP can well reproduce the backscattering coefficient and brightness temperature, with correlation coefficients of 0.87, 0.89, 0.78, and 0.43 and root-mean-square errors of 0.49 dB, 0.52 dB, 7.20 K, and 10.47 K for $\sigma _{\mathrm{ HH}}^{o} $ , $\sigma _{\mathrm{ VV}}^{o} $ , $T_{\mathrm {BH}}$ , and $T_{\mathrm {BV}}$ , respectively. In contrast, TVG-A and TVG-P can only accurately model the backscattering coefficient and brightness temperature, respectively. Without any modifications of the calibrated parameters, the error metrics computed from the validation data are slightly worse than those of the calibration data. These results demonstrate the feasibility of the synergistic use of SMAP active radar and passive radiometer observations under the unified framework of a physical model. In addition, the results demonstrate the necessity and effectiveness of applying GSA in model optimization. It is expected that these findings can contribute to the development of model-based soil moisture retrieval methods using active and passive microwave remote sensing data.
- Subjects :
- Backscatter
0211 other engineering and technologies
Microwave radiometry
02 engineering and technology
Tor Vergata (TVG) model
Passive radar
law.invention
Scattering
Atmospheric radiative transfer codes
law
Calibration
Emissivity
Calibration and validation
Electrical and Electronic Engineering
Radar
021101 geological & geomatics engineering
Remote sensing
Physics
Radiometer
Global sensitivity analysis (GSA)
Active and passive microwave
Spaceborne radar
22/4 OA procedure
Soil Moisture Active Passive (SMAP)
Brightness temperature
ITC-ISI-JOURNAL-ARTICLE
General Earth and Planetary Sciences
Soil moisture
Subjects
Details
- Language :
- English
- ISSN :
- 01962892
- Volume :
- 57
- Issue :
- 2
- Database :
- OpenAIRE
- Journal :
- IEEE transactions on geoscience and remote sensing
- Accession number :
- edsair.doi.dedup.....aad4ef61710cdcd9d52164a50544969f