Abstract
Abstract. Spaceborne microwave remote sensing is widely used to monitor global environmental changes for understanding hydrological, ecological, and climate processes. A new global land parameter data record (LPDR) was generated using similar calibrated, multifrequency brightness temperature (Tb) retrievals from the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) and the Advanced Microwave Scanning Radiometer 2 (AMSR2). The resulting LPDR provides a long-term (June 2002–December 2015) global record of key environmental observations at a 25 km grid cell resolution, including surface fractional open water (FW) cover, atmosphere precipitable water vapor (PWV), daily maximum and minimum surface air temperatures (Tmx and Tmn), vegetation optical depth (VOD), and surface volumetric soil moisture (VSM). Global mapping of the land parameter climatology means and seasonal variability over the full-year records from AMSR-E (2003–2010) and AMSR2 (2013–2015) observation periods is consistent with characteristic global climate and vegetation patterns. Quantitative comparisons with independent observations indicated favorable LPDR performance for FW (R ≥ 0.75; RMSE ≤ 0.06), PWV (R ≥ 0.91; RMSE ≤ 4.94 mm), Tmx and Tmn (R ≥ 0.90; RMSE ≤ 3.48 °C), and VSM (0.63 ≤ R ≤ 0.84; bias-corrected RMSE ≤ 0.06 cm3 cm−3). The LPDR-derived global VOD record is also proportional to satellite-observed NDVI (GIMMS3g) seasonality (R ≥ 0.88) due to the synergy between canopy biomass structure and photosynthetic greenness. Statistical analysis shows overall LPDR consistency but with small biases between AMSR-E and AMSR2 retrievals that should be considered when evaluating long-term environmental trends. The resulting LPDR and potential updates from continuing AMSR2 operations provide for effective global monitoring of environmental parameters related to vegetation activity, terrestrial water storage, and mobility and are suitable for climate and ecosystem studies. The LPDR dataset is publicly available at http://files.ntsg.umt.edu/data/LPDR_v2/.
Highlights
Earth’s atmospheric, biophysical, and hydrological processes are closely coupled (Walko et al, 2000; Trenberth et al, 2007) and respond to altered climate forcing manifested by changes in key environmental variables (Meehl et al, 2007)
Recent refinements based on the land parameter data record (LPDR) v1 algorithm framework were carried out separately using Advanced Microwave Scanning Radiometer for EOS (AMSR-E) or Advanced Microwave Scanning Radiometer 2 (AMSR2) Tb observations, including (a) an empirical calibration of the AMSR2 precipitable water vapor (PWV) retrieval based on similar observations from the Atmospheric Infrared Sounder (AIRS; Du et al, 2015), (b) a refined AMSR2 estimation of Tmx and Tmn that considers terrain and latitude effects (Du et al, 2015), and (c) an improved AMSR-E volumetric soil moisture (VSM) retrieval using a weighted averaging strategy and dynamic selection of vegetation-scattering albedos (Du et al, 2016a)
The LPDR fractional open water (FW) record distinguishes dynamic flooding events not represented by the ancillary static water map, including extensive water inundation (Fig. 3a) and large seasonal FW variations (Fig. 3b) in Bangladesh where the summer monsoon brings large precipitation-driven flooding (Brouwer et al, 2007)
Summary
Earth’s atmospheric, biophysical, and hydrological processes are closely coupled (Walko et al, 2000; Trenberth et al, 2007) and respond to altered climate forcing manifested by changes in key environmental variables (Meehl et al, 2007). While lower-frequency (e.g., L-band) sensors, including the ESA Soil Moisture and Ocean Salinity (SMOS) and NASA Soil Moisture Active Passive (SMAP) missions, are generally considered optimal for detecting soil and surface water signals under moderate to high vegetation biomass conditions (Kerr et al, 2001; Entekhabi et al, 2010), higherfrequency sensors, such as AMSR-E (Koike et al, 2004) and AMSR2 (Imaoka et al, 2012), provide simultaneous multichannel (C- to W-band) Tb observations with variable sensitivity to surface water, soil, vegetation, and atmosphere conditions (Njoku et al, 2003; Jones et al, 2010). The LPDR v1 encompasses the AMSR-E record (2002–2011), while similar observations from AMSR2 enable potential LPDR continuity (Du et al, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
