Estimation of global soil moisture seasonal variability using SMOS satellite observations

Abstract

Soil moisture observations are expected to play an important role in monitoring global climate trends. However, measuring soil moisture is challenging because of its high variability; point-scale in situ measurements are scarce being remote sensing the only practical means to obtain regional- and global-scale soil moisture estimates. The ESA’s Soil Moisture and Ocean Salinity (SMOS) is the first satellite mission ever designed to measuring the Earth’s surface soil moisture at daily time scales with an unprecedented level of accuracy. Since its launch in November 2009, significant efforts have been dedicated to validate, and finetune, the retrieval algorithms so that SMOS-derived soil moisture estimates meet the standards required for a wide variety of applications. The SMOS Barcelona Expert Center (BEC) is distributing daily, monthly, seasonal and annual temporal averages of 0.25° global soil moisture maps, which have proved useful for assessing drought conditions and monitoring water stress. These products include a downscaling algorithm to combine SMOS and NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) data into fine-scale (< 1km) soil moisture estimates, which permits extending the applicability of the data to regional and local studies. These soil moisture products can also be a useful tool to monitor the effectiveness of land restoration management practices. The aim of this work is to assess the reliability of novel global SMOS-derived soil moisture products produced at BEC. The analysis includes determination of variability at seasonal and interannual scales, focusing on six target regions representative of arid, semi-arid, sub-humid and humid areas across global land biomes. In addition, the dry-normal-humid ranges from SMOS products are being generated to provide maps of their spatial and temporal distribution. These soil moisture climatologies are further used for analyzing the anomalies during the four-year of SMOS in orbit