Table 2:

Ancillary data used in L2_SM_P_E and L2_SM_P processing.

Ancillary Data	Grid Resolution	Time Resolution	Primary Data Source
Water fraction	3 km	Static	MODIS MOD44W (Chan, 2013)
Urban fraction	3 km	Static	Global Rural Urban Mapping Project (GRUMP) (Das, 2013)
DEM slope variability	3 km	Static	USGS GMTED 2010 (Podest and Crow, 2013)
Soil texture	3 km	Static	FAO Harmonized World Soil Database (HWSD) (Das, 2013)
Land cover	3 km	Static	MODIS MCD12Q1 (V051) (Kim, 2013)
NDVI	3 km	2000–2013	MODIS MOD13A2 (V005) (Chan, 2013)
Snow fraction	9 km	Daily	NOAA IMS (Kim, 2011)
Freeze/thaw fraction	9 km	1 hourly	GMAO GEOS-5 (SMAP, 2015)
Soil temperatures	9 km	1 hourly	GMAO GEOS-5 (SMAP, 2015)
Precipitation	9 km	3 hourly	GMAO GEOS-5 (Dunbar, 2013)