Assessment of the Soil Moisture-Evaporative Fraction Coupling Strength Using the Cosmic-Ray Neutron Sensing Network

Abstract:

Terrestrial land-to-atmosphere interaction, especially the soil moisture-evaporative fraction (SM-EF) coupling, provides an essential understanding of climate variability and natural disasters monitoring. This relationship is commonly obtained by land surface and climate models, whereas their assessment using direct observations is limited due to the lack of high-quality soil moisture and flux tower networks. The Cosmic-Ray Neutron Sensing (CRNS) network emerging recently has demonstrated the feasibility of field scale surface and root-zone soil moisture monitoring. Moreover, the neutron intensity measured at CRNS is sensitive to not only soil water content but also atmospheric water vapor and biomass water content, holding the potential to quantify evapotranspiration (ET) and vegetation water variability. This study aims to assess the feasibility of CRNS in capturing the regional SM-EF coupling and evaluate this coupling strength under water-limited and energy-limited conditions, and over different vegetation covers and climatic zones. The SM-EF coupling strength information provided by CRNS is useful for ET and other hydrological variables estimation using CRNS, extreme events forecasting and uncertainties reduction in climate models.