A physically-based inversion algorithm for retrieving soil moisture in passive microwave remote sensing

► By reducing degrees of freedom of the Fresnel equation, a unique inversion algorithm (Hong’s algorithm) is developed for retrieving soil moisture in passive microwave remote sensing. ► The surface roughness and the dielectric constant are retrieved using Hong’s approximation. ► The Hong’s algorith...

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Veröffentlicht in:Journal of hydrology (Amsterdam) Jg. 405; H. 1; S. 24 - 30
Hauptverfasser: Hong, Sungwook, Shin, Inchul
Format: Journal Article
Sprache:Englisch
Veröffentlicht: Kidlington Elsevier B.V 21.07.2011
Elsevier
Schlagworte:
Algorithms
Applied geophysics
Dielectric constant
Earth Observing System
Earth sciences
Earth, ocean, space
energy
equations
Exact sciences and technology
Georgia
Hong’s approximation
Hydrology
Hydrology. Hydrogeology
Internal geophysics
Inversion
Inversions
land use
Mathematical analysis
Microwaves
Missions
oceans
Oklahoma
Polarization
radiometers
Remote sensing
Retrieval
roots
Roughness
salinity
satellites
Soil moisture
soil water
surface roughness
temperature
Volumetric soil water content
United States
Oklahoma
Georgia
USA, Oklahoma
ASW, USA, Georgia
Polarization
Inversion
Dielectric constant
Hong’s approximation
Volumetric soil water content
Roughness
atmosphere
microwaves
algorithms
accuracy
soil water
North America
dielectric constant
roughness
water content
polarization
soils
satellites
models
inverse problem
salinity
interfaces
soil moisture
Space remote sensing
Hong's approximation
surface water
brightness temperature
errors
Pixel
ISSN:0022-1694, 1879-2707
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Beschreibung
Zusammenfassung:► By reducing degrees of freedom of the Fresnel equation, a unique inversion algorithm (Hong’s algorithm) is developed for retrieving soil moisture in passive microwave remote sensing. ► The surface roughness and the dielectric constant are retrieved using Hong’s approximation. ► The Hong’s algorithm shows good consistency with field observations (SMEX03) and with current AMSR-E soil moisture algorithms. ► Consequently, the Hong’s algorithm is advantageous for an operational purpose with the minimal use of land surface forward models. Surface soil moisture plays a key role in water and energy exchanges at the land–atmosphere interface. Previous research on the microwave remote sensing of soil moisture focused mostly on the forward modeling problem. This paper presents a unique inversion algorithm (Hong’s algorithm) for soil moisture retrieval with reduced degrees of freedom of the Fresnel equation; the algorithm is based on the characteristics of the polarization ratio for rough surfaces around the Brewster angle and Hong’s approximation, which is an approximate relationship between vertically and horizontally polarized reflectivities. Using the daily observations of the Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) taken at 0.25° × 0.25° pixel, the soil moisture is estimated globally over the land surface using a relation between the complex dielectric constant and the soil moisture after retrieving the surface roughness and complex dielectric constant. The surface soil moisture products obtained from Hong’s algorithm are validated using in situ observations carried out in Oklahoma and Georgia in 2003. The official AMSR-E soil moisture products are compared to assess Hong’s algorithm using identical brightness temperature data sets. The biases and the root mean squared error calculated in comparison with the ground observations are in the range of −0.059 m 3/m 3 to 0.01 m 3/m 3 and 0.023 m 3/m 3 to 0.065 m 3/m 3, respectively. Hong’s algorithm estimates the soil moisture within the estimated accuracy of AMSR-E surface soil moisture, 0.06 m 3/m 3, without requiring a priori information about the roughness and the dielectric constants of the surface. With a minimal use of forward models, this research could also be applied to global soil moisture retrieval in the Soil Moisture and Ocean Salinity satellite mission and the Soil Moisture Active/Passive mission.
Bibliographie:ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:0022-1694
1879-2707
DOI:10.1016/j.jhydrol.2011.05.005