Table 1.

Performance metrics R [−] and ubRMSD [m³/m³] of OL, DA_σ°, DA_TB and DA_σ°,TB for surface (sfmc) and root-zone (rzmc) soil moisture. Average metrics for 9-km core sites and sparse networks are followed by the metrics for individual sites/networks. N is the number of grid cells (for core sites) or point measurements (for sparse networks). N_{in situ} is the number of 3-hourly in situ measurements used for validation. N_σ° and N_TB are the numbers of assimilated Sentinel-1 σ° and SMAP TB observations, respectively. SCAN stands for the U.S. Natural Resources Conservation Service Soil Climate Analysis Network, USCRN for the U.S. Climate Reference Network, and SMOSMANIA for the SMOS-Meteorological Automatic Network Integrated Application.

					R[−]					ubRMSD [m3/m3]
sfmc (0–5 cm)	N	Nin situ	Nσ°	NTB	OL	DAσ°	DATB	DAσ°,TB	CI	OL	DAσ°	DATB	DAσ°,TB	CI
Core sites	16	2686	75	540	0.58	0.63	0.66	0.70	±0.04	0.052	0.050	0.048	0.046	±0.006
REMEDHUS	2	2667	127	545	0.59	0.61	0.53	0.60	±0.14	0.032	0.034	0.037	0.035	±0.011
Yanco	2	3913	42	628	0.84	0.86	0.92	0.93	±0.07	0.079	0.074	0.049	0.049	±0.030
Twente1	1	2611	148	307	0.66	0.81	0.52	0.62	±0.17	0.081	0.076	0.083	0.080	±0.053
Little Washita	1	2646	78	501	0.70	0.73	0.80	0.79	±0.07	0.041	0.040	0.035	0.035	±0.010
Fort Cobb	2	4083	78	520	0.64	0.63	0.74	0.74	±0.08	0.043	0.043	0.038	0.037	±0.007
South Fork	2	3161	45	486	0.10	0.44	0.62	0.67	±0.11	0.069	0.060	0.052	0.050	±0.012
Valencia	1	1754	94	605	0.39	0.42	0.49	0.51	±0.16	0.026	0.025	0.024	0.024	±0.006
Niger2	1	1066	42	595	0.28	0.23	0.47	0.54	±0.17	0.038	0.040	0.049	0.045	±0.006
Benin2	1	1821	85	607	0.68	0.71	0.74	0.76	±0.13	0.063	0.062	0.056	0.056	±0.024
TxSON	2	2177	22	711	0.75	0.77	0.83	0.82	±0.13	0.045	0.044	0.039	0.039	±0.014
HOBE3	1	1080	134	248	0.82	0.82	0.73	0.83	±0.13	0.044	0.046	0.051	0.046	±0.026
Sparse networks	201	3488	49	580	0.59	0.61	0.66	0.68	±0.04	0.059	0.057	0.054	0.053	±0.005
SCAN4	27	3472	33	544	0.57	0.57	0.64	0.64	±0.04	0.057	0.056	0.056	0.055	±0.006
USCRN5	25	3288	36	509	0.58	0.60	0.66	0.66	±0.04	0.058	0.057	0.053	0.053	±0.005
Oklahoma Mesonet6	93	3825	47	585	0.54	0.56	0.67	0.67	±0.09	0.064	0.062	0.058	0.057	±0.013
OzNet7	42	3405	39	655	0.78	0.79	0.84	0.85	±0.12	0.077	0.073	0.062	0.061	±0.031
SMOSMANIA8	14	1887	142	512	0.55	0.61	0.62	0.66	±0.14	0.048	0.045	0.045	0.042	±0.014
rzmc (0–100 cm)
Core sites	7	2705	52	562	0.53	0.65	0.73	0.75	±0.18	0.034	0.033	0.027	0.028	±0.008
Little Washita	1	1999	78	501	0.81	0.87	0.84	0.85	±0.17	0.032	0.031	0.027	0.027	±0.012
Fort Cobb	2	3418	78	520	0.68	0.64	0.68	0.70	±0.26	0.028	0.030	0.031	0.030	±0.009
South Fork	2	3122	45	486	0.02	0.38	0.57	0.61	±0.32	0.043	0.038	0.030	0.030	±0.009
TxSON	2	1927	22	711	0.85	0.84	0.90	0.90	±0.37	0.032	0.033	0.023	0.024	±0.023
Sparse networks	161	3534	51	574	0.64	0.62	0.64	0.64	±0.10	0.046	0.045	0.046	0.046	±0.015
SCAN	23	3335	35	537	0.65	0.63	0.63	0.62	±0.11	0.041	0.042	0.043	0.042	±0.014
USCRN	22	3175	37	518	0.64	0.62	0.64	0.63	±0.11	0.046	0.046	0.043	0.043	±0.008
Oklahoma Mesonet	85	3947	47	587	0.62	0.60	0.64	0.64	±0.36	0.057	0.057	0.056	0.056	±0.075
OzNet	18	3527	39	667	0.75	0.77	0.81	0.81	±0.66	0.029	0.031	0.054	0.049	±0.176
SMOSMANIA	13	1799	145	520	0.50	0.55	0.52	0.57	±0.47	0.040	0.038	0.039	0.037	±0.094

¹van der Velde et al. [2015],

²Lebel et al. [2009]; Pellarin et al. [2009]; Cappelaere et al. [2009],

³Bircher et al. [2012],

⁴Schaefer et al. [2007],

⁵Diamond et al. [2013]; Bell et al. [2013],

⁶McPherson et al. [2007],

⁷Smith et al. [2012],

⁸Albergel et al. [2008]; Dorigo et al. [2011]