TY - JOUR
T1 - The Soil Moisture Active Passive Experiments
T2 - validation of the SMAP products in Australia
AU - Ye, Nan
AU - Walker, Jeffrey P.
AU - Wu, Xiaoling
AU - De Jeu, Richard
AU - Gao, Ying
AU - Jackson, Thomas J.
AU - Jonard, Francois
AU - Kim, Edward
AU - Merlin, Olivier
AU - Pauwels, Valentijn R.N.
AU - Renzullo, Luigi J.
AU - Rudiger, Christoph
AU - Sabaghy, Sabah
AU - Von Hebel, Christian
AU - Yueh, Simon H.
AU - Zhu, Liujun
PY - 2021/4
Y1 - 2021/4
N2 - The fourth and fifth Soil Moisture Active Passive Experiments (SMAPEx-4 and -5) were conducted at the beginning of the SMAP operational phase, May and September 2015, to: 1) evaluate the SMAP microwave observations and derived soil moisture (SM) products and 2) intercompare with the Soil Moisture and Ocean Salinity (SMOS) and Aquarius missions over the Murrumbidgee River Catchment in the southeast of Australia. Airborne radar and radiometer observations at the same microwave frequencies as SMAP were collected over SMAP footprints/grids concurrent with its overpass. In addition, intensive ground sampling of SM, vegetation water content, and surface roughness was carried out, primarily for validation of airborne SM retrieval over six sim 3,,text {km} times 3 km focus areas. In this study, the SMAPEx-4 and -5 data sets were used as independent reference for extensively evaluating the brightness temperature and SM products of SMAP, and intercompared with SMOS and Aquarius under a wide range of SM and vegetation conditions. Importantly, this is the only extensive airborne field campaign that collected data while the SMAP radar was still operational. The SMAP radar, radiometer, and derived SM showed a high agreement with the SMAPEx-4 and -5 data set, with a root-mean-squared error (RMSE) of 3 K for radiometer brightness temperature, and an RMSE of sim 0.05~text{m}^{3}/text{m}^{3} for the radiometer-only SM product. The SMAP radar backscatter had an RMSE of 3.4 dB, while the retrieved SM had an RMSE of 0.11 m3/m3 when compared with the SMAPEx-4 data set.
AB - The fourth and fifth Soil Moisture Active Passive Experiments (SMAPEx-4 and -5) were conducted at the beginning of the SMAP operational phase, May and September 2015, to: 1) evaluate the SMAP microwave observations and derived soil moisture (SM) products and 2) intercompare with the Soil Moisture and Ocean Salinity (SMOS) and Aquarius missions over the Murrumbidgee River Catchment in the southeast of Australia. Airborne radar and radiometer observations at the same microwave frequencies as SMAP were collected over SMAP footprints/grids concurrent with its overpass. In addition, intensive ground sampling of SM, vegetation water content, and surface roughness was carried out, primarily for validation of airborne SM retrieval over six sim 3,,text {km} times 3 km focus areas. In this study, the SMAPEx-4 and -5 data sets were used as independent reference for extensively evaluating the brightness temperature and SM products of SMAP, and intercompared with SMOS and Aquarius under a wide range of SM and vegetation conditions. Importantly, this is the only extensive airborne field campaign that collected data while the SMAP radar was still operational. The SMAP radar, radiometer, and derived SM showed a high agreement with the SMAPEx-4 and -5 data set, with a root-mean-squared error (RMSE) of 3 K for radiometer brightness temperature, and an RMSE of sim 0.05~text{m}^{3}/text{m}^{3} for the radiometer-only SM product. The SMAP radar backscatter had an RMSE of 3.4 dB, while the retrieved SM had an RMSE of 0.11 m3/m3 when compared with the SMAPEx-4 data set.
KW - Calibration and validation
KW - field experiment
KW - passive microwave remote sensing
KW - radar remote sensing
KW - remote sensing
KW - soil moisture (SM)
UR - http://www.scopus.com/inward/record.url?scp=85103412018&partnerID=8YFLogxK
U2 - 10.1109/TGRS.2020.3007371
DO - 10.1109/TGRS.2020.3007371
M3 - Article
AN - SCOPUS:85103412018
SN - 0196-2892
VL - 59
SP - 2922
EP - 2939
JO - IEEE Transactions on Geoscience and Remote Sensing
JF - IEEE Transactions on Geoscience and Remote Sensing
IS - 4
ER -