20-6. Advancing soil moisture monitoring at a national scale

CLOSED

----------

Background: Soil moisture is a key state variable of the climate system, coupling energy and water exchange to the atmosphere, while partitioning precipitation into infiltration and runoff. However, soil moisture is difficult to quantify at appropriate scales due to its inherent variability and the spatial extent of its measurement. In situ sensors have a small support volume that reflect local-scale variability from soil properties, topography, and vegetation. Spaceborne retrieval of soil moisture from NASA’s Soil Moisture Active Passive (SMAP) has coarse spatial (~9 or 36 km) and temporal (2-3 days) resolutions [Chan et al., 2016]. More often, intermediate-scale (1-4 km) soil moisture estimates are needed for hydrological, meteorological, and climatological applications. Cosmic-ray neutron sensing (CRNS) can effectively close this scale gap. This next-generation technique integrates soil moisture observations over ~10 hectares using a proximal, non-contact sensor that requires no site disturbance, below-ground infrastructure, or routine maintenance [Zreda et al., 2012].

Soil moisture networks [Cosh et al., 2021] can be classified as either sparse, containing a single measurement location, or dense, providing multiple measurements within representative area (e.g., 1² km or HUC10 catchment). For accurate calibration and validation of soil moisture from satellite and models, dense networks are required with sufficient spatial representativeness to produce soil moisture estimates at 3², 9² or 36² km footprints [Caldwell et al., 2019]. Hydrologic models are now running at hyper-resolutions and satellite downscaling routines are producing 1 km soil moisture products that require network densities of <0.1 km².  However, there are few of such networks operating across these scales.

The selected Fellow is expected to leverage ongoing activities related to the Next Generation Water Observing Systems (NGWOS) efforts to develop and utilize a network of CRNS probes in Integrated Water Science (IWS) Basins. The Fellow will be based in the Nevada Water Science Center located in Carson City, Nevada, and work in collaboration with Hydrologic Remote Sensing Branch (HRSB) of the USGS Water Mission Area (WMA) and CRNS researchers at the University of Arizona and Forschungszentrum Jülich. The Fellow will participate in field campaigns across all NGWOS basins and develop novel applications of CRNS to monitor soil moisture in NGWOS basins. NGWOS and WMA have the goal of operationally producing terrestrial water storage observations with seamless national coverage, high resolution, and high accuracy. The Fellow will have access to the tremendous scientific resources of USGS and collaborators and the opportunity to pursue their own scientific interests while furthering the Earth science goals of the Bureau.  

Description of the Research Opportunity: Recent satellite missions and land surface models have advanced soil moisture science but benefit from on-ground data collection for calibration, validation, and assimilation [Colliander et al., 2017]. This research opportunity proposes to advance soil moisture monitoring at the USGS using temporary, dense network of CRNS probes, portable CRNS measurements, and in situ data. The objective is to produce a set of high-resolution measurement zones for each IWS basin. The Fellow will work with Research and Development activities on CRNS in NGWOS and develop methodologies to utilize CRNS data and conduct independent, innovative research in the field of soil moisture.

This work will be closely tied with CRNS researchers at the University of Arizona and the Terrestrial Environmental Observatory in Germany to develop and optimize sensor requirements and calibration needs within USGS WMA specifications. The Fellow would utilize these data to develop novel approaches to integrate CRNS into workflows with WMA collaborators in the HRSB and model-derived soil moisture and other applications involving scaling, sensor networks, terrain analysis, hydrological modeling, and applications such as wildfire potential, groundwater recharge, flood and drought forecasting within WMA.

A successful applicant must show evidence of the following: 

• Demonstrated record of peer-reviewed publications related to science and applications for hydrology
• Demonstrated research record using soil moisture data for hydrologic science 
• Excellent oral (including public speaking) and written communication skills. 

• Experience building and/or working in collaborative, diverse and inclusive team environments 
• Strong interpersonal and communication skills 

The following knowledge and skills are preferred: 

• Advanced knowledge of soil moisture sensing methodologies and applications including but not limited to observational techniques (in situ and remote), and their combination in the form of scientific analyses, data assimilation, machine learning, and cloud- and/or high-performance-computing 
• Strong interest in the justification, formulation, and implementation of new hydrologic monitoring systems

Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas.

References:

Caldwell, T. G., T. Bongiovanni, M. H. Cosh, et al. (2019), The Texas Soil Observation Network: A comprehensive soil moisture dataset for remote sensing and land surface model validation, Vadose Zone Journal, 18:100034, doi:10.2136/vzj2019.04.0034.

Chan, S. K., R. Bindlish, P. E. O'Neill, et al. (2016), Assessment of the SMAP passive soil moisture product, IEEE Transactions on Geoscience and Remote Sensing, 54, 4994-5007, doi:10.1109/Tgrs.2016.2561938.

Colliander, A., T. J. Jackson, R. Bindlish, et al. (2017), Validation of SMAP surface soil moisture products with core validation sites, Remote Sensing of Environment, 191, 215-231, doi:10.1016/j.rse.2017.01.021.

Cosh, M. H., T. G. Caldwell, C. B. Baker, et al. (2021), Developing a strategy for the national coordinated soil moisture monitoring network, Vadose Zone Journal, e20139, 1-13, doi: 10.1002/vzj2.20139.

Zreda, M., W. J. Shuttleworth, X. Zeng, C. Zweck, D. Desilets, T. E. Franz, and R. Rosolem (2012), COSMOS: the COsmic-ray Soil Moisture Observing System, Hydrology and Earth System Sciences, 16, 4079-4099, doi: 10.5194/hess-16-4079-2012.

Proposed Duty Station: Carson City, Nevada

Areas of PhD: Geology, hydrology, geophysics, engineering, physical science, or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).

Qualifications: Applicants must meet the qualifications for one of the following: Research Geologist, Research Geophysicist, Research Engineer, Research Hydrologist, or Research Physical Scientist.

(This type of research is performed by those who have backgrounds for the occupations stated above.  However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)

Human Resources Office Contact:  Audrey Tsujita, 916-278-9395, atsujita@usgs.gov