New insights from Purdue University have reignited our understanding of atmospheric blocking, a pivotal phenomenon responsible for extreme weather events such as heat waves, droughts, floods, and frigid cold spells. This research sheds light on how moisture intricately alters the atmospheric dynamics governing blocking patterns, providing vital clues that could revolutionize weather forecasting and climate model accuracy. Atmospheric blocking occurs when persistent, stagnant air masses disrupt the conventional west-to-east flow of the jet stream, effectively “blocking” the natural progression of weather systems. These patterns can cause prolonged periods of abnormal weather that challenge meteorologists and climate scientists worldwide.
Historically, the study of atmospheric blocking has been rooted in simplifying assumptions, notably the premise that the atmosphere is entirely dry. Originating around the 1940s, these classical theories, while foundational, have overlooked a fundamental aspect of Earth’s atmosphere—its moisture content. Assistant Professor Lei Wang of Purdue’s Department of Earth, Atmospheric, and Planetary Sciences (EAPS), alongside PhD student Zhaoyu Liu, have steered research that directly challenges this long-standing assumption. Their work pioneers an understanding of how moisture-driven diabatic heating influences the formation, intensity, and persistence of blocking events, adding a nuanced layer to meteorological theory.
Atmospheric blocking manifests predominantly in two forms: ridge blocks and dipole blocks. Ridge blocks are large, quasi-stationary high-pressure systems that create a “bubble” in the atmosphere, pushing the jet stream northward. These ridges often correlate with heat waves during summer months. Dipole blocks, meanwhile, are characterized by adjacent high- and low-pressure systems that trap contrasting weather patterns, such as prolonged cold spells juxtaposed with warm conditions. The distinction between these types is critical, as Wang and Liu’s research reveals that moisture’s role in enhancing or dampening these blocks is not uniform but highly dependent on their structural diversity.
At the core of this discovery is the concept of diabatic heating—the warming or cooling of air resulting from the exchange of thermal energy with its surroundings. Moisture induces diabatic heating primarily through condensation and evaporation processes. Wang and Liu found that moisture-induced diabatic heating fortifies ridge blocks by reinforcing their high-pressure dominance, which solidifies the blocking pattern, prolonging extreme heat episodes. Conversely, this same heating mechanism surprisingly weakens dipole blocks by dampening their amplitude, reducing the intensity and duration of contrasting weather anomalies.
This dichotomous effect of moisture is groundbreaking because it resolves a perplexing inconsistency in climate model projections. Models have increasingly predicted a decrease in blocking events as the planet warms, a prediction historically at odds with observational data indicating stable or even increased blocking frequency. The team’s physical interpretation, based on the geopotential height tendency equation, elucidates why dipole blocks diminish in strength under humid conditions, reconciling model data with observed atmospheric behavior. This mathematical framework quantifies how variations in atmospheric height fields evolve, influenced by heat exchanges and moisture content, revealing the mechanics behind blocking diversity.
Wang likens atmospheric blocking to traffic jams on highways. Traditional dry atmosphere theories treated these blocks as inevitable choke points. However, introducing moisture into the equation is akin to changing the road conditions during a traffic jam. “Sometimes,” Wang explains, “drivers adjusting to traffic flow can alleviate congestion rather than exacerbate it.” Similarly, moisture acts as an environmental factor that can modulate the severity of blocking, smoothing out some blocks like dipole systems while enhancing others like ridge blocks.
The implications for weather prediction are significant. Subseasonal to seasonal forecasts, which cover periods from weeks to months, have historically struggled to accurately predict blocking events and their associated extreme weather outcomes. Recognizing the distinct roles of diabatic heating and moisture in different blocking types introduces a paradigm shift in forecasting models. This refined understanding promises to enhance the skill of predictions, improving preparation for events like heat waves, cold spells, droughts, and flooding.
Purdue’s research team utilized advanced high-performance computing resources at the Rosen Center for Advanced Computing, enabling detailed simulations and analysis of atmospheric dynamics on an unprecedented scale. The computational power allowed them to dissect complex interactions between moisture and air flow, teasing out the subtle mechanisms by which moisture modulates blocking behavior. Their interdisciplinary approach merges atmospheric science, fluid dynamics, and thermodynamics, illustrating the multifaceted nature of weather systems.
This study’s publication in the esteemed journal Nature Communications underscores its importance to the global scientific community. It represents a significant leap forward in understanding how moisture impacts atmospheric circulation patterns—knowledge that is crucial in the context of ongoing climate change. As the planet warms, moisture content in the atmosphere is expected to increase, making it imperative that climate models incorporate these nuanced interactions to provide reliable future projections.
Furthermore, this research highlights the broader scope of atmospheric dynamics, with Wang’s group exploring not only Earth’s weather but also the atmospheres of other planets. By decoding the universal principles underpinning blocking and extreme weather events, they contribute to a more comprehensive understanding of atmospheric behavior across different planetary environments. This work situates Earth’s weather within a larger cosmic context, emphasizing the fundamental physics that govern atmospheres universally.
Funding for this research came from prestigious institutions, including the National Oceanic and Atmospheric Administration (NOAA), the U.S. National Science Foundation (NSF), and the NASA Science Mission Directorate. Such support reflects a growing recognition of the critical need to improve predictive capabilities for extreme weather events and climate phenomena—issues that bear profound implications for societies worldwide.
In summary, Purdue University’s groundbreaking research overturns decades of dry-assumption models by revealing the intricate and varying impacts of moisture-induced diabatic heating on atmospheric blocking. This nuanced insight reconciles previous inconsistencies in climate modeling and paves the way for enhanced forecasting accuracy. As extreme weather events become increasingly frequent and severe, understanding these atmospheric mechanisms will be essential in safeguarding communities and informing policy decisions globally.
Subject of Research: Atmospheric blocking, moisture impacts on diabatic heating, climate dynamics, extreme weather prediction
Article Title: Blocking Diversity Causes Distinct Roles of Diabatic Heating in the Northern Hemisphere
News Publication Date: July 1, 2025
Web References:
- Article: https://www.nature.com/articles/s41467-025-60811-4
- DOI: http://dx.doi.org/10.1038/s41467-025-60811-4
Image Credits: Photo provided by Lei Wang, Purdue University
Keywords: Climatology, Atmospheric science, Atmospheric dynamics, Atmospheric physics, Weather forecasting, Weather
