|Timeline:||October 2015 - 30 September 2019|
Unsaturated zone is an important integral part of hydraulic cycle in land surface process. Soil hydraulic properties (water retention, hydraulic conductivity) (SHP) are the most important vadose zone parameters to govern the partitioning of soil moisture between infiltration and evaporation flux and soil thermal properties (heat capacity, thermal conductivity) (STP) for water heat transport process. These two physical properties are interactive and cannot be violated. Pixel-scale soil physical parameters and their accuracies are critical for the success of hydroclimate and soil hydrologic models. However, limited by inappropriate upscaling methods, it is difficult to characterize soil physical parameters under regional scales. Pedotransfer functions (PTFs), relating SHP/STP with readily available data on soil properties i.e., soil texture information have been used in land surface model (LSM). However, published soil texture maps or field soil profile may not be representative in regional scale, it thus cause biases for LSM results. Getting available SHP/STP in landscape scale is imperative for LSM applications.
Inverse approach using LSM and remote sensing is another way to determine these parameters (Figure 1). Different state variables (soil moisture content, land surface temperature, leaf area index) have been used to retrieve soil physical properties using LSMs. Soil moisture content is a direct parameter related with soil physical properties, while L-band microwave brightness temperature (TB) is the essence of retrieving soil moisture content. Our main objective is to estimate SHP/STP in landscape scale using microwave L-band TB remote sensing and LSM.
In our study (1) it will be found whether soil texture information in landscape scale can have a possibility of retrieval from TB information in emission models i.e., CMEM; (2) Whether LSM i.e., HTESSEL will produce a reliable results using estimated SHP/STP derived from PTFs based on (1); (3) Whether dynamic SHP/STP under different meteorological conditions can be obtained from coupled CMEM and HTESSEL; (4) Extend this method from in-situ measurements (see Fig. 2a) to earth observations (see Fig. 2b).