H187-01
Detecting Soil Moisture under Temperate Forest Canopies: SMAP Validation Experiment 2019-2021 (SMAPVEX19-21)
Tuesday, 15 December 2020: 17:30
Virtual
Andreas Colliander1, Michael H Cosh2, Vicky Kelly3, Simon Kraatz4, Laura L Bourgeau-Chavez5, Paul Siqueira4, Alexandre Roy6, Tarendra Lakhankar7, Alexandra G. Konings8, Nataniel Holtzman8, Sidharth Misra1, Mehmet Kurum9, Dara Entekhabi10, Peggy E O'Neill11 and Simon H Yueh12, (1)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (2)U. S. Dept. of Agriculture, Beltsville, MD, United States, (3)Cary Institute of Ecosystem Studies, Millbrook, United States, (4)University of Massachusetts, Amherst, Amherst, United States, (5)Michigan Technological University, MI, USA, Michigan Tech Research Institute, Ann Arbor, MI, United States, (6)Université du Québec à Trois-Rivières, Québec, United States, (7)NOAA-CREST, The City College of New York, CUNY, New York, NY, United States, (8)Stanford University, Department of Earth System Science, Stanford, CA, United States, (9)Mississippi State University, Mississippi State, MS, United States, (10)Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, Cambridge, MA, United States, (11)NASA Goddard SFC, Greenbelt, MD, United States, (12)JPL, Pasadena, CA, United States
Abstract:
The retrieval of soil moisture under forest canopy has long been an important goal for low frequency remote sensing. The NASA SMAP mission started a dedicated field experiment in May 2019 by deploying two temporary soil moisture networks in northeast US that cover two separate SMAP pixels with variable degree of forest cover. The measurements will run through 2021 and they will be augmented with two intensive observation periods (IOP) in 2021. The experiment also includes tower-based radiometer observations with ground truth measurements within the instrument footprint.
The soil moisture networks are deployed at two SMAP footprint size domains in Millbrook, New York and Harvard Forest, Massachusetts. Each network has over 20 stations measuring soil moisture, soil temperature and air temperature. Additionally, each station has a nadir pointing camera for phenology monitoring and a selection of sites have sap flow and tree dielectric constant sensors. The first IOP is planned for April 2021, and the second one in July 2021. The IOPs will see mapping of the experiment domains with airborne high-resolution SMAP-like observations using the PALS (Passive Active L-band sensor) instrument, and intensive manual measurements of soil moisture and vegetation.
Early results have shown that the SMAP measurement signal at L-band is sensitive to soil moisture changes observed on the ground underneath some forest canopies with a root mean square error of about 0.05 m3/m3. Based on an empirical tuning exercise of a brightness temperature model, the L-band transmissivity of the signal is larger than conventionally assumed for forests. The results indicate that roughly half of the emission detected by SMAP comes from the ground and the other half from the vegetation. Expectation is that the spatially and temporally varying vegetation parameters will be quantified through future efforts for forest soil moisture retrieval at global scale.
