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17 March 2003 Multifrequency ground-based radiometer and in-situ measurements of soil moisture at high temporal resolution
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We compare methods used to measure the water content near the soil surface. The primary objective of this project is to link remotely sensed surface water contents to the soil water regime, in particular to the regime of structured soils. We attempt to use the dynamics of spatially averaged surface water contents measured with microwave radiometry to predict preferential infiltration and drainage. Under field conditions the so-called macropore flow plays an important role in the infiltration and drainage behavior of a soil, as well as in the mass transfer of all kinds of solutes to larger soil depths. These rapid processes are only detectable during the first few hours after a rainfall event, when most of the larger pores are still water filled. The main focus of our project lies in an areal integration of such processes on a field scale. For this reason, we depend on areal data with a high temporal resolution that allow to characterize the soil water dynamics. In this study we report on a field experiment with two different ground-based radiometers (1.4 GHz and 11.4 GHz, respectively) centered at a 5 m × 10 m bare soil plot. The brightness temperature measured with passive microwave sensors contains information on surface water content that is already spatially averaged. Furthermore the water content was measured in-situ with time domain reflectometry probes (TDR) assembled at five depths. In the same depths we measured matric potential (pressure head of soil water) and soil temperature. These data were recorded every 30 min from May to July 2002. In addition, we determined the moisture profile over the top 15 cm using neutron radiography. Transmission radiographs of soil slabs vertically taken from the surface horizon allow for a high spatial resolution of the water distribution. In order to characterize the surface roughness of the soil on a mm-scale we used optical measurement techniques. We illustrate the implications of the results from this field campaign on the dynamics of surface water content.
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Katrin Schneeberger, Christian Stamm, Christian Maetzler, Hannes Fluehler, Eberhard Lehmann, and Jochen Willneff "Multifrequency ground-based radiometer and in-situ measurements of soil moisture at high temporal resolution", Proc. SPIE 4879, Remote Sensing for Agriculture, Ecosystems, and Hydrology IV, (17 March 2003);

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