This year we celebrate the 50th anniversary of Earth Day. Climate change is one of the biggest challenges facing humanity and so the theme for Earth Day 2020 is climate action. There are many ways that individuals and organizations can take climate action. As a climatologist in the Department of Geography at The Ohio State University, one of the ways that I am taking action is through helping to assemble, quality control, harmonize and disseminate high-quality climate observations. These data are essential for monitoring and detecting climate variability and climate change. Since 2010, I have been involved in developing the most comprehensive soil moisture database in the United States. With funding from the National Science Foundation, USDA and NOAA, we developed nationalsoilmoisture.com. The map shown below indicates the locations where soil moisture measurements are currently being made in the United States. Data from many of these sites are being provided in near-real-time on nationalsoilmoisture.com. This includes in situ measurements of soil moisture, satellite-derived soil moisture from NASA SMAP and model-derived soil moisture from NLDAS-2.
Figure 1. Locations of in situ soil moisture sensor networks across the United States from federal- and state-level networks. Credit: nationalsoilmoisture.com.
These data fill a critical gap because unlike for other climatological and hydrological variables, there are no national databases for soil moisture. The 2008 report on “Future Climate Change Research and Observations: GCOS, WCRP and IGBP Learning from the IPCC Fourth Assessment Report” (WMO/TD No. 1418) recommended that soil moisture data should be assembled because of its importance for:
(1) improving our understanding of land-atmosphere interactions,
(2) developing seasonal to decadal climate forecasting tools,
(3) calibrating, validating and improving the physical parameterizations in regional and global land surface models (LSM),
(4) developing and validating satellite-derived soil moisture algorithms, and
(5) monitoring and detecting climate variability and change in this key hydrological variable.
Why is soil moisture important?
As we noted in Legates et al. (2011), “soil moisture is not just a process that is integral to climate, geomorphology, and biogeography – it truly lies at the intersection of all three branches of physical geography. A complete understanding of soil moisture and its spatial and temporal variability and impact draws upon interactions among and expertise gained from all three subdivisions. Soil moisture lies at the intersection of climatology, geomorphology, biogeography, and hydrology, thereby providing true integration of the subdisciplines rather than just supplying a common theme.” Soil moisture influences the exchange of energy and water between the land surface and atmosphere. Soil moisture controls the partitioning of rainfall into runoff and infiltration. It modulates vegetation growth and photosynthesis. It also influences mass movements, weathering, erosion and sediment transport. Therefore, soil moisture is a key climatological and hydrological variable. However, compared to precipitation and temperature, there are very few soil moisture measurements.
Current Efforts to Develop a National Soil Moisture Network
Significant progress is being made in the United States to address the critical gaps in soil moisture observations. As a member of the National Soil Moisture Network Executive Committee, I helped to draft “A Strategy for the National Soil Moisture Network: Coordinated, High-Quality, Nationwide, Soil Moisture Information for the Public Good” that was released in February 2020. This Strategy Document was called for in the National Integrated Drought Information System (NIDIS) Reauthorization of 2018. It is intended to review the current status of soil moisture monitoring and reporting in the U.S., and to develop a strategy for a national coordinated soil moisture monitoring network, involving federal agencies, regional and state mesonets, data providers, researchers, user groups, and others. The strategy document identifies ten recommendations for how to implement a National Soil Moisture Network. The goal of this effort is to provide a unifying structure to enhance monitoring activities, establish partnerships for building out the network, develop an organizational structure that will collect, integrate and deliver transformative soil moisture products to the nation. This one tangible way that the Department of Geography at Ohio State is actively involved in climate change research. This effort provides better data for assessing how the climate is changing and to increase the resilience of the United States to these changes.
Dr. Steven Quiring,