The global water cycle is the continuous transformation and movement of water on, above, and below the surface of the Earth through the phases of liquid, solid (ice and snow), and gas (vapor). It is the most active and important of the planet’s cycles, defining Earth’s mass, energy transportation, and transitions, and is influenced by factors such as global climate and human activity. To measure the effects of these transformations, scientists examine spatial distribution and temporal variations in images of cycle processes. However, such studies are currently limited by shortfalls in knowledge and observational capabilities. Existing systems offer satellite monitoring of the cycle, but the images they produce would benefit from improved temporal resolution, for example.
Here, we present an integrated satellite-based observation system for the key elements and corresponding processes of the global water cycle. Our approach enhances observing and retrieval capabilities, to improve Earth science and global change studies. The proposed system, the Water Cycle Observation Mission (WCOM; see Figure 1), monitors soil moisture, ocean salinity, snow water equivalent, soil freeze-thaw processes, atmospheric water vapor, and precipitation. Moreover, its optimized payload configuration and design enable the mission to provide observations of all the environmental parameters—dominant and auxiliary—required for accurate retrieval of water cycle information. We can use the resulting datasets to refine the long-term satellite observations made during recent decades, and to monitor changes in hydrological elements.