Assessment of the SMAP Level-4 Surface and Root-Zone Soil Moisture Product Using In Situ Measurements

[EN]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 (...

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Detalles Bibliográficos
Autores: Zeng, Yijian, Wu, Xiaoling, Walker, Jeffrey, van der Velde, Rogier, Thibeault, Marc, Su, Zhongbo, Starks, Patrick, Seyfried, Mark, Rowlandson, Tracy, Prueger, John, Pellarin, Thierry, Pacheco, Anna, Moghaddam, Mahta, McNairn, Heather, Martínez Fernández, José, Lopez-Baeza, Ernesto, Livingston, Stan, Jensen, Karsten H., Holifield Collins, Chandra D., González Zamora, Ángel, Cosh, Michael, Caldwell, Todd G., Bosch, David, Bircher, Simone, Berg, Aaron, Smith, Edmond B., Mahanama, Sarith P., Koster, Randal D., Kimball, John S., Jones, Lucas A., Jackson, Thomas J., Crow, Wade, Conaty, Austin, Colliander, Andreas, Ardizzone, Joseph V., Liu, Qing, De Lannoy, Gabrielle J. M., Reichle, Rolf H.
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2017
País:España
Institución:Universidad de Salamanca (USAL)
Repositorio:GREDOS. Repositorio Institucional de la Universidad de Salamanca
OAI Identifier:oai:gredos.usal.es:10366/167289
Acceso en línea:http://hdl.handle.net/10366/167289
Access Level:acceso abierto
Palabra clave:SMAP
Soil Moisture
Validation
Descripción
Sumario:[EN]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 m23 (0.030 m3 m-3) at the 9-km scale and 0.035 m3 m23 (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.

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