Using Remotely-Sensed Estimates of Soil Moisture to Infer Soil Texture and Hydraulic Properties Christa D. Peters-Lidard, Joseph A. Santanello, Jr., and David M. Mocko, NASA/GSFC Code Near-surface soil moisture is a critical component of land-surface energy and water balance models, and controls water and energy cycles, as well as weather, climate, hydrological, and agricultural prediction. Accurate soil moisture prediction requires soil texture and hydraulic property information, which is poorly characterized over most of the globe. Comparisons of simulated and measured soil texture demonstrate new capabilities in NASA’s Land Information System model. The optimized modeling capabilities represent a significant improvement over previous approaches, and improve NASA support of agency needs for accurate soil moisture measurements Optimized vs. Measured Soil Textures Christa Peters-Lidard NASA/GSFC Multiple agencies are responding to this need for accurate soil moisture measurements a) Default Soil Texture b) Optimized Soil Texture SIMULATED ERROR PBMR

Name: Christa Peters-Lidard, NASA/GSFC Phone: References: Santanello, J.A., Jr., C. D. Peters-Lidard, M. Garcia, D. Mocko, M. Tischler, MS. Moran, and D.P. Thoma, Using Remotely-Sensed Estimates of Soil Moisture to Infer Soil Texture and Hydraulic Properties across a Semi-arid Watershed, In Press, Remote Sensing of the Environment. Peters-Lidard, Christa D., David M. Mocko, Joseph A. Santanello, Jr., Michael A. Tischler, M. Susan Moran, Matthew Garcia, and Y. Wu, The role of precipitation uncertainty for soil property estimation using soil moisture retrievals in a semi-arid environment. Submitted to Water Resources Research. Garcia, M., C.D. Peters-Lidard, and D.C. Goodrich, Spatial interpolation of precipitation in a dense gauge network for monsoon storm events in the southwestern US. Submitted to Water Resources Research. Data Sources: This is a joint effort composed of multiple agencies including the USDA-Agricultural Research Service (watershed, remote-sensing data), NASA-GSFC (land-surface modeling within the Land Information System (LIS; coupled with Parameter Estimation (PEST)) and US Army Corps of Engineers-Engineering Research and Development Center (financial support, operational testing, user interface development), Near-surface (0-5cm) soil moisture observations (Figure 1) derived from successive aircraft flights using NASA’s L-Band Push-Broom Microwave Radiometer (PBMR; a precursor to the Hydros/SMAP mission) were acquired during the Monsoon ‘90 experiment in SE Arizona, and used to calibrate soil hydraulic properties in the Noah land-surface model executed within LIS at a very high horizontal spatial resolution of 40 meters. Technical Description of Image: Figure 1: Simulated (top), PBMR-observed (middle), and difference (bottom) 0-5 cm soil moisture using a) default (USDA SSURGO) soils and b) soil properties calibrated using LIS/Noah+PEST on DOY 214. The soil moisture bias and RMS error are greatly reduced after the soil property calibration. Limited remote microwave retrievals of near-surface soil moisture can be used to calibrate the soil texture and hydraulic properties using this combined observation, modeling and parameter estimation approach. (Fig. 1). [Santanello et al., 2007] Figure 2: Percentages of sand, silt, and clay estimated using this approach at the eight sites compared with in-situ soil measurements from Schmugge et al. (1994). The LIS/Noah+PEST system correctly estimates highly-sandy soils in this semi-arid watershed. Soil texture estimated using this approach corresponds well with in situ observations of sand, silt, and clay at various sites across the watershed. By estimating within a continuous range of soil properties such as sand, silt, and clay percentages rather than applying disconitnuous soil texture classes, the physical accuracy and consistency of the estimated soil properties is assured and can be more easily assessed against in situ measurements. Scientific significance: Soil texture and hydraulic properties are required for accurate prediction of soil moisture, and are poorly known over many areas of the globe. This work is the first to demonstrate how remotely sensed soil moisture combined with a physical model may be combined to infer these critical parameters. Relevance for future science and relationship to Decadal Survey: Soil moisture is a critical control on water and energy cycles, as well as weather, climate, hydrological and agricultural prediction. Soil texture and hydraulic properties are required for accurate prediction of soil moisture. Soil moisture observations from the SMAP mission, to be launched in the timeframe, combined with precipitation observations from the GPM mission, to be launched in 2013, will provide the necessary data products to infer soil textures world wide using the techniques presented in this work. Christa Peters-Lidard NASA/GSFC

“Sensors With Wings”: Aerotenna Ocean Marsh A prototype L-band radiometer on a UAV aircraft provides new capabilities for detailed studies of hydrological processes, including measurements of salinity, soil moisture and snow thickness (w/Hilliard/555 et al) The Aerotenna is an experimental system designed to investigate the use of a miniature L-band passive microwave instrument on a small aerial platform and will improve our understanding of local hydrological processes. A first flight was successfully conducted over Wallops Island on June 18, A measurement resolution of <100m was demonstrated.

Name: Geoff Bland, NASA/GSFC Phone number: References: Bland, G., Coronado, P., Miles, T., Bretthauer, P., The AEROS Project – Experiments with Small Electric Powered UAVs for Earth Science, AIAA 2005 Hilliard, L., Hildebrand, P., Markus, T., Johnson, C., Lawrence, R., Bland, G., Microwave Instrumentation for UAV Platforms Enabling Thin Ice Measurement, AIAA 2005 Lawrence, R., Hilliard, L., Bland, G., Markus, T., Autonomous Aerial Observation System Concepts for Microwave Remote Sensing, AIAA 2005 Hilliard, L., Phelps, N., Riley, J., Markus, T., Bland, G., Ruf, C., Lawrence, R., Reising, S., Pichel, T., Prototype Cryospheric Experimental Synthetic Array Radiometer (CESAR), International Geoscience and Remote Sensing Symposium (IGARSS), 2005 Data Sources: Experimental L-Band (~1.4 GHz) Radiometer uses Innovative Antennas and Electronics. Unmanned Aerial Vehicle (UAV) System uses Electric Propulsion and Weighs 12 Pounds. Technical Description of Images: Figures 1 and 2 show the Aerotenna UAV. The first flight was conducted June 18, 2007 over Wallops Island, and the results indicate good sensitivity and performance. Flown at an altitude of approximately 100 meters, surface feature resolution is better than the original goal of 100 meters. This radiometer operates at L-Band (~1.4 GHz) and two lightweight antenna arrays were mounted internally, one in each wing. The airframe, electric propulsion, power and data systems were tailored for this instrument, and GPS and a real-time video camera were included in the payload. The integrated instrument/vehicle system is performing well, and the team is encouraged that the “Sensors with Wings” approach will provide new capabilities for detailed studies of hydrological processes. Figure 3 shows the modulation of the sensor signals (left and right wing antennas) as it flies a racetrack pattern over the marsh/land and ocean areas. The marsh and land have higher brightness temperatures than the ocean, and the modulation of the marsh/land signal is due to the highly varied ground and water features, versus the relatively uniform ocean signal. Scientific Significance: The Aerotenna Unmanned Aerial Vehicle (UAV) is an experimental system intended to investigate the use of a miniaturized passive microwave instrument on a small aerial platform. High spatial resolution measurements of sea surface salinity, snow depth, and soil moisture are the objective, and the small UAV is well suited for local scale observations. The prototype antenna and electronics represent a significant step in the miniaturization of instruments suitable for small UAVs. Relevance for future science and relationship to Decadal Survey: Near term experiments include evaluating this system for the mapping of variations in salinity, particularly in coastal areas. A thermal infrared imager may be added to the instrument suite, and flights over agricultural areas are also planned. Tests to characterize the performance of this system in the arctic environment will be conducted as well. This effort is aimed to provide high resolution measurements that will be helpful in refining models based on satellite observations, as well as improve our understanding of local processes. These Aerotenna tests directly support the Decadal Survey recommendation to include UAV technology in the strategic planning of Earth science research.