An international team of scientists has found that moisture rising from crops, irrigation systems and shallow groundwater in the U.S. Corn Belt helps fuel large thunderstorm complexes across the region.
The study, led by researchers at the U.S. National Science Foundation National Center for Atmospheric Research, examined mesoscale convective systems, or MCSs, which are clusters of thunderstorms spanning at least 60 miles and lasting for extended periods.
Researchers concluded that shallow groundwater reservoirs, combined with irrigation and extensive crop production across the Corn Belt, increase the frequency of these storm systems by 24% to 35%. The systems also persist about 10% longer.
MCSs account for an estimated 40% to 60% of growing-season precipitation in the Corn Belt, supplying critical moisture to one of the world’s leading corn-producing regions. At the same time, the storms can produce flooding, hail, damaging winds and tornadoes.
Scientists said the findings could improve both short-term severe weather forecasting and longer-range weather prediction models for the Midwest and Great Plains.
The research focused on the Corn Belt region stretching from Ohio to Nebraska. Scientists used advanced computer simulations and a specialized algorithm to track the movement of water vapor and analyze how agricultural practices interact with atmospheric conditions.
The study was published in "Nature Communications Earth & Environment" and involved researchers from NSF NCAR, ETH Zürich in Switzerland, the Universidade de Santiago de Compostela in Spain and the Hong Kong University of Science and Technology. The work was supported by the National Science Foundation.
Researchers said previous studies showed the Corn Belt has become more humid and has experienced increasing rainfall, but the causes have been difficult to isolate. Earlier work by the same research team found that groundwater left behind by retreating glaciers, along with irrigation and crop growth, contributes moisture to the atmosphere.
For the new study, researchers used two NSF NCAR-based computer models to simulate storms during the April-to-August growing season. One set of simulations included groundwater, crop growth and irrigation, while another excluded those factors.
The models were run using the NSF NCAR-Wyoming Supercomputing Center and compared with observed weather conditions during 2010, 2011 and 2012, representing wet, normal and dry years.
Researchers found that only simulations incorporating groundwater, crops and irrigation closely matched observed storm activity, rain gauge data and satellite observations.
The analysis showed that moisture from groundwater and agricultural activity increased atmospheric water vapor and strengthened storm updrafts, creating conditions favorable for more frequent and longer-lasting storm systems.
Scientists said the research highlights the importance of understanding how land use changes influence weather patterns in heavily farmed regions. They also noted the findings could help improve future atmospheric models and support decisions related to planting strategies and water management across the Corn Belt.
Source: University Corporation for Atmospheric Research, "Fields of thunder"