Combined Passive and Active Microwave Observations of Soil Moisture During CLASIC

Analysis of coincident L-band radiometer and radar measurements with respect to soil moisture and vegetation conditions

“…In SGP99 and SMEX02 the aircraft was a C-130 and the instrument was equipped with horn antenna [Njoku et al, 2002;Narayan et al, 2004]. In CLASIC and SMAPVEX08 the aircraft was a Twin Otter and the instrument was equipped with a microstrip antenna [Yueh et al, 2008;Bindlish et al, 2010]. The flight altitude of the aircrafts ranged from 1000 m to 3000 m and the beam width from 13° (horn) to 20° (microstrip) resulting in footprint of about 300 m to 1300 m. The relative accuracy of radar and radiometer were less than 0.2 K and 0.2 dB, respectively, throughout the campaigns.…”

Application of reflected Global Navigation Satellite System (GNSS-R) signals in the estimation of sea roughness effects in microwave radiometry

“…Data from three instruments, PALS [16], POLSCAT [17] and the DMR [9][18] were used to record brightness temperature, wind speed from Ku-band polarimetric backscatter, and the GNSS-R DDM. A brief description is provided for each instrument and the flight campaign.…”

“…To investigate the polarimetric observations of land or sea surfaces, the original S-band receiver was converted to another L-band receiver to enable simultaneous reception of vertical and horizontal polarizations. This conversion was completed in 2006-2007 prior to PALS' participation in the Cloud and Land Surface Interaction Campaign (CLASIC) in 2007 [24] [16]. The PALS radiometer electronics were also modified to include a microwave hybrid after the front-end low noise amplifiers in the V and H receivers to produce the brightness temperature measurements at +45 and -45 degree linear polarizations, which can be used to derive the third Stokes parameter measurement.…”

Water stress detection using radar

“…Current applications of radar include crop classification (Ulaby et al, 1982b;Hoogeboom, 1983;Foody et al, 1989;McNairn et al, 2009), biomass monitoring (Ferrazzoli et al, 1997;Paloscia et al, 1999;Chambers et al, 2007), fuel load estimation , and soil moisture estimation (Wagner et al, 1999;Bindlish and Barros, 2001;Joseph et al, 2008;Kim and van Zyl, 2009;Entekhabi et al, 2010;Brocca et al, 2017). Although vegetation water content (VWC) varies diurnally and seasonally (McNairn and Brisco, 2004), VWC is generally considered constant or to change only on a seasonal timescale (Wagner et al, 1999;Bindlish et al, 2009;Panciera et al, 2014;Kim et al, 2010;Steele-Dunne et al, 2017). Depending on the timescale of interest, diurnal variations in VWC can have a significant impact on backscatter.…”

“…When studying soil and vegetation water status dynamics on a daily timescale, diurnal variations might be significant. Soil moisture retrieval algorithms for radar missions require an estimate of VWC, which is generally considered constant or to change only on a seasonal time scale (Wagner et al, 1999;Naeimi et al, 2009;Bindlish et al, 2009;Kim et al, 2010;Panciera et al, 2014). In the latter case, seasonal variation is assumed to be due to canopy growth rather than diurnal moisture dynamics.…”