WEST LAFAYETTE, Ind. — Gully warsher. Duck drownder. Toad strangler. Cob floater. Sod soaker. These colorful terms describe the intense summer storms that have become synonymous with the Midwest. While the Indian subcontinent is renowned for its monsoon season, few realize that the Midwestern United States experiences its own powerful monsoon-like weather patterns. These storms are increasingly breaking through the atmospheric ceiling into the stratosphere, carrying with them aerosols and biomass from wildfires, with potentially concerning implications for the climate and the ozone layer.
Recent research conducted in partnership with NASA has revealed that these storms are introducing pollutants into the stratosphere, a layer of the atmosphere typically untouched by such disturbances. Using a high-altitude research aircraft, the study led by Dan Cziczo, a professor in Purdue University’s Department of Earth, Atmospheric, and Planetary Sciences, has uncovered this phenomenon. The findings, published in Nature Geoscience, indicate that the stratosphere is becoming littered with biomass particles during significant wildfire seasons.
Breaking Through the Atmospheric Barrier
The Midwest’s summer storms, fueled by warm, wet air from the Gulf of Mexico colliding with the Rocky Mountains, are akin to the monsoon systems in India. These storms often create towering clouds that, under certain conditions, can breach the boundary between the troposphere and the stratosphere. This phenomenon, known as an overshooting top, allows the storm to punch through into the stratosphere, carrying with it aerosols and pollutants from the lower atmosphere.
The stratosphere, home to the ozone layer, acts as a shield against the sun’s harmful radiation. Typically, only significant events like volcanic eruptions or meteor impacts introduce particles into this layer. However, the study suggests that human-induced climate changes could be affecting the stratosphere’s chemistry and stability.
“For so long, we’ve assumed the stratosphere is a pristine area. But what this shows is that human impacts through a changing climate can affect the chemistry and the radiative ability of the stratosphere,” Cziczo explained.
Wildfires Creating Their Own Weather
It’s not just the summer storms contributing to this phenomenon. Wildfires themselves can generate storm clouds, known as pyrocumulus, which are capable of propelling ash and biomass directly into the stratosphere. This was notably observed during the 2019 bushfire season in Australia. As climate change intensifies, these occurrences are becoming more frequent, raising concerns about their cumulative impact on the stratosphere.
“There are actually two ways for this stratosphere puncture to happen,” Cziczo noted. “It can be the one severe fire, but it can also be a bunch of little fires that are just constantly perturbing the stratosphere in a way that we didn’t recognize before.”
Exploring the Stratosphere with Advanced Technology
To study these atmospheric changes, NASA utilized a modified Lockheed Martin U-2 aircraft, known as the ER-2, capable of reaching altitudes of 70,000 feet. This aircraft, equipped with sophisticated instruments, allows scientists to measure changes in air quality and chemistry. By tracking the paths of summer storms and wildfires, Cziczo and his team have been able to document the effects on the stratosphere.
The ER-2’s capabilities are crucial for understanding the dynamics of the stratosphere. Unlike the troposphere, where weather occurs, the stratosphere is a high and isolated layer, typically only accessed by military aircraft, weather balloons, and spacecraft. The research conducted with the ER-2 provides valuable insights into how human activities are impacting this critical part of the atmosphere.
Implications for the Future
The introduction of aerosols and biomass into the stratosphere could have significant implications for the planet’s climate. These particles can interact with sunlight, potentially warming the stratosphere and affecting its stability. As the climate continues to change, understanding these interactions becomes increasingly important.
This research, funded by NASA’s Earth Science Project Office, underscores the need for continued investigation into the effects of human activities on the atmosphere. As Cziczo emphasized, “We went to all this trouble to save the ozone layer.” The findings highlight the delicate balance of Earth’s atmospheric systems and the potential consequences of disrupting them.
As the Midwest continues to experience intense summer storms and wildfires, the research conducted by Purdue University and NASA serves as a critical reminder of the interconnectedness of climate systems and the importance of preserving the integrity of the stratosphere.
For more information on Purdue University’s research initiatives, visit Purdue University Strategic Initiatives.
