Irrigation Signals Detected From SMAP Soil Moisture Retrievals

• Published in: Geophysical research letters 2017-12, Vol.44 (23), p.11,860-11,867
• Main Authors: Lawston, Patricia M., Santanello, Joseph A., Kumar, Sujay V.
• Format: Article
• Language: English
• Subjects: Atmospheric models; Baskets; Climate models; Clouds; Detection; Earth; Human influences; Human performance; Hydrologic cycle; Hydrological cycle; Irrigation; Irrigation systems; Rain; Remote sensing; Satellite observation; Satellites; Semiarid lands; Semiarid zones; SMAP; Soil; Soil moisture; Spaceborne remote sensing; Weather forecasting
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2017GL075733

Irrigation can influence weather and climate, but the magnitude, timing, and spatial extent of irrigation are poorly represented in models, as are the resulting impacts of irrigation on the coupled land‐atmosphere system. One way to improve irrigation representation in models is to assimilate soil moisture observations that reflect an irrigation signal to improve model states. Satellite remote sensing is a promising avenue for obtaining these needed observations on a routine basis, but to date, irrigation detection in passive microwave satellites has proven difficult. In this study, results show that the new enhanced soil moisture product from the Soil Moisture Active Passive satellite is able to capture irrigation signals over three semiarid regions in the western United States. This marks an advancement in Earth‐observing satellite skill and the ability to monitor human impacts on the water cycle. Plain Language Summary When farmers use irrigation over large areas, it can make the air cooler and more humid, sometimes even changing how clouds form and where rain falls. For this reason, it is important to know where and when irrigation is used, how wet the soil becomes, and how long it stays artificially wet. This information is critical for improving weather models, and therefore forecasts, in the food baskets of the world. However, until now it has been difficult to find accurate and consistent irrigation practice information over time and for large areas. In this paper, we show that a NASA satellite that measures soil moisture routinely across the globe is able to detect wet soil resulting from irrigation in naturally dry environments. This marks an advancement in Earth‐observing satellite skill and improves our ability to monitor and predict human impacts on the water cycle. Key Points To date, irrigation detection from passive microwave satellites has proven difficult even over well‐known, expansive regions of agriculture The new enhanced soil moisture product from the Soil Moisture Active Passive satellite can detect irrigation signals in three regions Satellite detection of irrigation increases our ability to understand, monitor, and predict human impacts on the water cycle