Researchers from the University of Leeds have discovered how rainfall patterns influence extreme humid heatwaves in tropical regions, offering hope for improved early warning systems to protect vulnerable communities.
Scientists have taken a significant step toward enhancing warning systems for communities at risk from increasingly severe humid heatwaves. These extreme weather events, exacerbated by climate change, pose a severe threat to human health, particularly in the global tropics and subtropics.
In a new study published in Nature Communications, researchers from the University of Leeds and the UK Centre for Ecology & Hydrology revealed how recent rainfall patterns intersect with land conditions to trigger extreme humid heat events.
This novel insight lays the groundwork for developing early warning systems that can save lives.
A Growing Threat
Climate change is making humid heatwaves more frequent and intense, especially in tropical and subtropical regions. Unlike dry heatwaves, the meteorological drivers behind extreme humid heat are not well understood until now.
Humid heatwaves are particularly perilous because when the wet-bulb temperature — a measure considering both temperature and humidity — hits 35 degrees Celsius, the human body cannot effectively cool down through sweating.
Lead author Lawrence Jackson, a research fellow in the School of Earth and Environment at Leeds University, highlighted the growing risk.
“With climate change driving more frequent and intense humid heat events, particularly in tropical and subtropical regions, the risks to vulnerable populations and outdoor workers are increasing,” he said in a news release. “The new understanding provided by our research highlights the potential for improved humid heat early warning systems, using near real-time satellite observations for soil moisture and rainfall.”
Research Findings
The researchers analyzed weather and climate data from 2001 to 2022 to track humid heatwaves across the tropics and subtropics. By examining the interplay between recent rainfall and whether the land was dry or wet, the team identified the conditions that precipitate these dangerous heat events.
Their findings show that in drier regions, humid heatwaves are more likely to occur during or immediately after periods of increased rainfall, while in wetter regions, they tend to follow at least two days of reduced rainfall.
This difference is due to changes in soil moisture and cloud cover affecting local humidity and temperatures.
Critical Implications
These insights are crucial for regions such as West Africa, India, East China, North Australia, the Amazon, Southeast United States and the Congo Basin — areas already experiencing these extreme conditions.
The study suggests that better prediction models and early warning systems could be developed to protect these vulnerable populations.
Cathryn Birch, a professor in meteorology and climate in the School of Earth and Environment who led the study, noted the urgent need for action.
“The outlook for tropical humid heat is really concerning. Humans avoid overheating by sweating. Evaporation of the sweat cools your body, allowing you to maintain a safe body temperature. Humidity makes this less effective,” she said in the news release. “Humid heatwaves can be lethal at air temperatures that for dry heat would be relatively safe. The tropics are naturally humid and even an apparently small increase in global temperatures leads to large increases in dangerous humid heat extremes. We not only need to urgently cut greenhouse gas emissions but also need improved early warning systems for humid heat.”
Further Research Needed
While this study has unlocked new understanding of the triggers behind extreme humid heatwaves, the researchers stress the need for continued investigation. Extending the analysis to hourly data could refine predictions, making community warnings even more precise and potentially lifesaving.
“Our results focus on the daily timescale for these heatwaves. An obvious next step would be to extend our analysis to hourly time scales which might allow us to work towards near real-time predictions with all the benefits that would bring to vulnerable communities,” added co-author John Marsham, a professor of atmospheric science in the School of Earth and Environment.
Source: University of Leeds