When the COVID-19 pandemic hit in early 2020 and countries went under quarantine, industries shut down and travel became limited, thus improving air quality conditions. From late January to March 2020, satellite-based maps showed a reduction in aerosols— which are tiny solid particles— and liquid droplets in the atmosphere. Additionally, from February to March 2022 in the central United States— particularly the Missouri River Basin— there was less precipitation than normal. Gabriele Villarini, a professor at the University of Iowa in the Department of Civil and Environmental Engineering, wonders if the observed reduction in precipitation was driven by the reduced aerosols that resulted from the pandemic.

The flood event of 2008 in eastern Iowa shaped Gabriele Villarini’s research interests. He was, at that time, working on completing his graduate studies and has since received his Ph.D. from the University of Iowa. “I focus on extreme events, such as floods, hurricanes, and atmospheric rivers, on what physical processes drive them, and on their future changes,” says Villarini of his career path.

In 2021, Villarini received funds from the Iowa Water Center Targeted Seed Grant Competition Program. Villarini was awarded $20,000 from the grant program to evaluate how much of an impact the abrupt reduction in aerosols had on precipitation and to determine what physical processes were responsible for the decrease in precipitation. He matched the grant with $40,000 from partners and university support. When asked what importance this research held for Villarini, he said, “This work combines my passion for hydroclimatology with an event (i.e., the pandemic) that affected many spheres of our lives.” Villarini hypothesizes that local aerosol reduction led to a detectable change in precipitation and discharge across the central United States, and the effects were either magnified or reduced depending on the magnitude of aerosols coming from outside the central United States. This hypothesis will be tested in Villarini’s research project, titled “Understanding the Impacts of Coronavirus-related Reduction in Aerosols and Pollution on Precipitation and Discharge across Iowa.”

To determine the validity of his hypothesis, Villarini will perform four experiments to isolate the contribution of aerosols. The experiments will utilize WRF-Chem, a computer program that simulates interactions of aerosols with radiation, clouds, and snow albedo and reveals the impact of aerosols on air quality and climate. It also simulates the emissions, transport, mix, and chemical transformation of aerosols and trace gasses— which are the small number of certain gasses in the atmosphere— simultaneously with meteorology.

The first experiment is the control, wherein all aerosol emissions and transport will be included for February through April 2020. Business As Usual, the second experiment, will simulate the same data as the control experiment, but from February through April 2019 to isolate the role of aerosols. The third experiment, NoTRANS, will remove aerosols transported from outside the central US to highlight the effect of remote anthropogenic aerosols. NoLocal, the fourth experiment, will turn off the anthropogenic aerosols within the central US to highlight the effect of local aerosols.

Villarini, the lead principal investigator, will be in charge of project vision, oversight, implementation, and supervision of the graduate student devoted to this project, as well as the focus on evaluating the atmospheric model’s performance. Co-PIs Professor Witold Krawjeski (Department of Civil and Environmental Engineering at the University of Iowa) and Dr. Felipe Quintero (research scientist for the Iowa Flood Center at the University of Iowa) will oversee the evaluation of the impacts that the reduction in aerosols had on discharge across Iowa by focusing on the hydrologic model developed by the Iowa Flood Center to complement Villarini’s simulated results.

The long-term impact of this research will be to provide information on the potential impacts of mitigation efforts aimed at reducing anthropogenic aerosols on precipitation across the central United States. The issue of aerosols and their impacts on precipitation has been previously studied, but the benchmark work from Villarini will look at the effects of their reductions on a large scale (i.e., the pandemic). As a result of this project, methodologies for characterizing the impact of climate change on discharge will be enhanced, and advancements in the interdisciplinary studies of hydrology, climatology, and atmospheric sciences will be made.