Evaluation of Soil Moisture Estimates Derived from the Advanced Microwave Scanning Radiometer 2 (AMSR2) in the Philippines

ABSTRACT: Advancements in satellite data retrievals of soil moisture immensely alleviated the challenges of acquiring soil moisture measurements at high spatial and temporal resolution. However, usefulness of these datasets is subject to validation before utilization in operational and research applications. Also, to substantiate the validity of a prior study on soil moisture from AMSR-E that paved way to understanding the trends, variability, and dynamics of soil moisture across the country from 2002 to 2011, an elaborate assessment on this product is vital. The Advanced Microwave Scanning Radiometer 2 or AMSR2 was launched on May 18, 2012 as the follow-up mission of AMSR-E, the first passive sensor to include surface soil moisture in its standard products. This study validated AMSR2 soil moisture estimates over agricultural sites in Philippines by comparing in situ soil moisture obtained using the gravimetric technique and a soil moisture sensor. Ground measurements were obtained from several provinces from 2013 up to the present. Also, through time-series analysis, correlation and regression studies, its potential in monitoring surface soil moisture variations due to precipitation events and temperature fluctuations was evaluated. Rainfall estimates were derived from the Tropical Rainfall Measuring Mission (TRMM), which is widely used to monitor rainfall in the tropics. Results demonstrated the capability of AMSR2 to provide reliable surface soil moisture estimates (R2=0.64) and its sensitivity to precipitation and heating events. Areas and season when AMSR2 is most reliable were also investigated. This study aims to provide an efficient and sustainable means of obtaining accurat