Journal Article

FZJ-2014-00432

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Soil Hydraulic Parameters and Surface Soil Moisture of a Tilled Bare Soil Plot Inversely Derived from L-Band Brightness Temperatures

Dimitrov, M. (Corresponding author)FZJ* ; Vanderborght, J.FZJ* ; Kostov, K. G. ; Jadoon, K. Z.FZJ* ; Weihermüller, L.FZJ* ; Jackson, T. J. ; Bindlish, R. ; Pachepsky, Y. ; Schwank, M. ; Vereecken, H.FZJ*

2014
SSSA Madison, Wis.

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Please use a persistent id in citations: doi:10.2136/vzj2013.04.0075

Abstract: L-band radiometers can be used to remotely monitor the microwave brightness temperature of land surfaces. We investigated how soil hydraulic properties and soil moisture contents of a bare soil plot can be inferred from L-band brightness temperatures using a coupled inversion approach.We coupled a radiative transfer model and a soil hydrologic model (HYDRUS 1D) with an optimization routine to derive soil hydraulic parameters, surface roughness, and soil moisture of a tilled bare soil plot using measured brightness temperatures at 1.4 GHz (L-band), rainfall, and potential soil evaporation. The robustness of the approach was evaluated using five 28-d data sets representing different meteorological conditions. We considered two soil hydraulic property models: the unimodal Mualem–van Genuchten and the bimodal model of Durner. Microwave radiative transfer was modeled by three different approaches: the Fresnel equation with depth-averaged dielectric permittivity of either 2- or 5-cm-thick surface layers and a coherent radiative transfer model (CRTM) that accounts for vertical gradients in dielectric permittivity. Brightness temperatures simulated by the CRTM and the 2-cm-layer Fresnel model fitted well to the measured ones. L-band brightness temperatures are therefore related to the dielectric permittivity and soil moisture in a 2-cm-thick surface layer. The surface roughness parameter that was derived from brightness temperatures using inverse modeling was similar to direct estimates from laser profiler measurements. The laboratory-derived water retention curve was bimodal and could be retrieved consistently for the different periods from brightness temperatures using inverse modeling. A unimodal soil hydraulic property function underestimated the hydraulic conductivity near saturation. Surface soil moisture contents simulated using retrieved soil hydraulic parameters were compared with in situ measurements. Depth-specific calibration relations were essential to derive soil moisture from near-surface installed sensors.

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Contributing Institute(s):

1. Agrosphäre (IBG-3)

Research Program(s):

1. 255 - Terrestrial Systems: From Observation to Prediction (POF3-255) (POF3-255)

Appears in the scientific report 2014

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Database coverage:
; Current Contents - Agriculture, Biology and Environmental Sciences ; JCR ; SCOPUS ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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