A new study by scientists at the Massachusetts Institute of Technology (MIT) reveals critical atmospheric conditions that may help predict the onset of humid heat waves and related storms in regions traditionally unaccustomed to such extreme weather. This research, published in the journal Science Advances, highlights how climate change is intensifying the frequency and severity of humid heat waves in midlatitude areas, particularly in the Midwestern United States.
Historically, humid heat waves followed by severe thunderstorms have been more common in tropical regions. However, rising global temperatures are shifting this pattern, leading to unusual episodes of high heat and humidity in temperate climates. The MIT researchers identified that the maximum heat and humidity a region can experience is largely influenced by the presence of an atmospheric inversion—a condition where a layer of warm air traps cooler air beneath it.
Funing Li, a postdoctoral researcher in MIT’s Department of Earth, Atmospheric and Planetary Sciences, explained, “Our analysis shows that the eastern and midwestern regions of the U.S. and eastern Asian regions may be new hotspots for humid heat in the future climate.” This finding underscores the potential for these areas to face increased discomfort due to more frequent humid heat waves.
The team’s research found that atmospheric inversions act like a blanket, not only trapping pollutants but also accumulating heat and moisture at the surface. The longer these inversions persist, the more oppressive the humid heat waves can become. Eventually, when the inversion weakens, the stored energy can trigger intense thunderstorms and heavy rainfall.
Understanding Atmospheric Inversions
The study delves into the mechanics of how atmospheric inversions affect weather patterns. In typical conditions, as a heat wave passes, warm air at ground level rises, leading to convection and rain as the warm air cools at higher altitudes. The researchers sought to understand the threshold at which air begins to convect and release moisture.
Using a model that examines the energy dynamics within air parcels, the team discovered that the strength of the atmospheric inversion is critical. The greater the stability of the inversion, the more heat and moisture must accumulate before the air can rise and lead to precipitation. This mechanism can create a cycle where regions experience prolonged periods of oppressive heat followed by intense rainfall events.
The Impact of Climate Change
As the climate continues to warm, the researchers suspect that atmospheric inversions may become more persistent, exacerbating the situation. This means regions that have historically experienced mild weather could face increased risks of both humid heat waves and severe storms.
Talia Tamarin-Brodsky, an assistant professor at MIT, noted, “As the climate warms, theoretically the atmosphere will be able to hold more moisture. This could lead to new regions in the midlatitudes experiencing moist heat waves that will cause stress that they weren’t used to before.” The implications for public health, agriculture, and infrastructure in these areas could be significant.
The research highlights a pressing need for enhanced forecasting methods that account for these atmospheric dynamics. As weather patterns evolve, communities must adapt to the potential for both more severe heat waves and less frequent but more intense storm events.
This study is part of the MIT Climate Grand Challenge focusing on weather and climate extremes, with support from Schmidt Sciences. The findings provide a framework for understanding how midlatitude regions can prepare for and respond to the impacts of climate change, particularly in relation to humid heat and its associated risks.