Abstract
Global information on the spatio-temporal variation of parameters driving the Earth’s terrestrial water and energy cycles, such as evapotranspiration (ET) rates and surface soil moisture (SSM), is of key significance. The water and energy cycles underpin global food and water security and need to be fully understood as the climate changes. In the last few decades, Earth Observation (EO) technology has played an increasingly important role in determining both ET and SSM. This paper reviews the state of the art in the use specifically of operational EO of both ET and SSM estimates. We discuss the key technical and operational considerations to derive accurate estimates of those parameters from space. The review suggests significant progress has been made in the recent years in retrieving ET and SSM operationally; yet, further work is required to optimize parameter accuracy and to improve the operational capability of services developed using EO data. Emerging applications on which ET/SSM operational products may be included in the context specifically in relation to agriculture are also highlighted; the operational use of those operational products in such applications remains to be seen.
Highlights
These demands combined with the potential forward impact of climate change demonstrate that there is an urgent need to garner a better understanding of the natural processes driving the global hydrological cycle [5,6,7]
This paper provided a review of the state of the art in the use of Earth Observation (EO) data to derive operational estimates of ET and surface soil moisture (SSM)
It discussed emerging applications that can potentially benefit from the integration of ET/SSM operational products
Summary
As global population and the human desire for a higher protein diet grows, pressure on the world’s scarce water supply will increase This pressure and demand for water shows a high geographic variance and there is no doubt that global droughts and flood risk, are threatening regional food security. These parameters exert a strong control on the Earth’s water, carbon cycles and ecosystem functioning [8,9] Tools to quantify both ET and SSM have a crucial role in understanding the Earth’s climatic system on the longer term but by enabling increased water use efficiency they can have significant economic, environmental and social impact on the shorter term. Data is required at high spatial and temporal resolutions to inform decision makers on sustainable utilisation and management of water [10]
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