TY - JOUR
T1 - Assessment of the SMAP Level-4 surface and root-zone soil moisture product using in situ measurements
AU - Reichle, Rolf H.
AU - De Lannoy, Gabrielle J.M.
AU - Liu, Qing
AU - Ardizzone, Joseph V.
AU - Colliander, Andreas
AU - Conaty, Austin
AU - Crow, Wade
AU - Jackson, Thomas J.
AU - Jones, Lucas A.
AU - Kimball, John S.
AU - Koster, Randal D.
AU - Mahanama, Sarith P.
AU - Smith, Edmond B.
AU - Berg, Aaron
AU - Bircher, Simone
AU - Bosch, David
AU - Caldwell, Todd G.
AU - Cosh, Michael
AU - González-Zamora, Ángel
AU - Collins, Chandra D.Holifield
AU - Jensen, Karsten H.
AU - Livingston, Stan
AU - Lopez-Baeza, Ernesto
AU - Martínez-Fernández, José
AU - McNairn, Heather
AU - Moghaddam, Mahta
AU - Pacheco, Anna
AU - Pellarin, Thierry
AU - Prueger, John
AU - Rowlandson, Tracy
AU - Seyfried, Mark
AU - Starks, Patrick
AU - Su, Zhongbo
AU - Thibeault, Marc
AU - van der Velde, Rogier
AU - Walker, Jeffrey
AU - Wu, Xiaoling
AU - Zeng, Yijian
N1 - Publisher Copyright:
© 2017 American Meteorological Society.
PY - 2017/10/1
Y1 - 2017/10/1
N2 - The Soil Moisture Active Passive (SMAP) mission Level-4 Surface and Root-Zone Soil Moisture (L4_SM) data product is generated by assimilating SMAP L-band brightness temperature observations into the NASA Catchment land surface model. The L4_SM product is available from 31 March 2015 to present (within 3 days from real time) and provides 3-hourly, global, 9-km resolution estimates of surface (0-5 cm) and root-zone (0-100 cm) soil moisture and land surface conditions. This study presents an overview of the L4_SM algorithm, validation approach, and product assessment versus in situ measurements. Core validation sites provide spatially averaged surface (root zone) soil moisture measurements for 43 (17) "reference pixels" at 9- and 36-km gridcell scales located in 17 (7) distinct watersheds. Sparse networks provide point-scale measurements of surface (root zone) soil moisture at 406 (311) locations. Core validation site results indicate that the L4_SM product meets its soil moisture accuracy requirement, specified as an unbiased RMSE (ubRMSE, or standard deviation of the error) of 0.04 m3 m-3 or better. The ubRMSE for L4_SM surface (root zone) soil moisture is 0.038 m3 m-3 (0.030 m3 m-3) at the 9-km scale and 0.035 m3 m-3 (0.026 m3 m-3) at the 36-km scale. The L4_SM estimates improve (significantly at the 5% level for surface soil moisture) over model-only estimates, which do not benefit from the assimilation of SMAP brightness temperature observations and have a 9-km surface (root zone) ubRMSE of 0.042 m3 m-3 (0.032 m3 m-3). Time series correlations exhibit similar relative performance. The sparse network results corroborate these findings over a greater variety of climate and land cover conditions.
AB - The Soil Moisture Active Passive (SMAP) mission Level-4 Surface and Root-Zone Soil Moisture (L4_SM) data product is generated by assimilating SMAP L-band brightness temperature observations into the NASA Catchment land surface model. The L4_SM product is available from 31 March 2015 to present (within 3 days from real time) and provides 3-hourly, global, 9-km resolution estimates of surface (0-5 cm) and root-zone (0-100 cm) soil moisture and land surface conditions. This study presents an overview of the L4_SM algorithm, validation approach, and product assessment versus in situ measurements. Core validation sites provide spatially averaged surface (root zone) soil moisture measurements for 43 (17) "reference pixels" at 9- and 36-km gridcell scales located in 17 (7) distinct watersheds. Sparse networks provide point-scale measurements of surface (root zone) soil moisture at 406 (311) locations. Core validation site results indicate that the L4_SM product meets its soil moisture accuracy requirement, specified as an unbiased RMSE (ubRMSE, or standard deviation of the error) of 0.04 m3 m-3 or better. The ubRMSE for L4_SM surface (root zone) soil moisture is 0.038 m3 m-3 (0.030 m3 m-3) at the 9-km scale and 0.035 m3 m-3 (0.026 m3 m-3) at the 36-km scale. The L4_SM estimates improve (significantly at the 5% level for surface soil moisture) over model-only estimates, which do not benefit from the assimilation of SMAP brightness temperature observations and have a 9-km surface (root zone) ubRMSE of 0.042 m3 m-3 (0.032 m3 m-3). Time series correlations exhibit similar relative performance. The sparse network results corroborate these findings over a greater variety of climate and land cover conditions.
KW - Data assimilation
KW - Kalman filters
KW - Land surface model
KW - Satellite observations
KW - Soil moisture
KW - Soil temperature
UR - http://www.scopus.com/inward/record.url?scp=85032730324&partnerID=8YFLogxK
U2 - 10.1175/JHM-D-17-0063.1
DO - 10.1175/JHM-D-17-0063.1
M3 - Article
AN - SCOPUS:85032730324
SN - 1525-755X
VL - 18
SP - 2621
EP - 2645
JO - Journal of Hydrometeorology
JF - Journal of Hydrometeorology
IS - 10
ER -