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Apr 29 2025
1Researchers have discovered that recent rainfall patterns play a critical role in triggering extreme humid heat events in tropical and subtropical regions—insights that could transform early warning systems for at-risk communities.
Scientists from the University of Leeds and the UK Centre for Ecology and Hydrology conducted the first comprehensive analysis of how rainfall and soil moisture interact to influence the occurrence of humid heat waves. Published in Nature Communications, the study sheds new light on the meteorological conditions behind these potentially deadly events.
As climate change intensifies, humid heat waves—characterized by high temperatures and extreme humidity—pose growing health risks, particularly across tropical zones. Unlike dry heat waves, which are better understood, the causes and behavior of humid heat have remained less clear.
Humid heat severely affects the body’s ability to regulate temperature through sweating. When the wet-bulb temperature—a metric combining temperature and humidity—reaches 35°C, the human body struggles to cool itself effectively. Prolonged exposure to such conditions can lead to heat stress, which in severe cases raises core body temperature by 3°C or more, potentially causing confusion, seizures, organ failure, or death. Alarmingly, this threshold has already been recorded in some coastal subtropical areas.
Dr. Lawrence Jackson, lead author and Research Fellow at the University of Leeds, emphasized the increasing danger: “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.”
Using climate and weather data spanning from 2001 to 2022, the research team examined how rainfall events—tracked via satellite—affected land surface moisture levels and the subsequent likelihood of humid heat waves. They found that in drier regions, such heat waves were more likely to follow or coincide with periods of increased rainfall. Conversely, in already wet regions, these events tended to follow at least two days of reduced rainfall.
This contrast is due to differing land-surface responses: rainfall raises soil moisture and humidity, while low rainfall and clear skies increase land temperatures, both contributing to humid heat in distinct ways depending on the region’s baseline conditions.
Professor Cathryn Birch, senior author of the study, warned, “The outlook for tropical humid heat is really concerning. In naturally humid environments, even small increases in temperature can result in dangerous extremes. This makes improved forecasting and rapid response systems crucial.”
The study identifies humid heat wave hotspots including monsoon regions like West Africa, India, East China, and northern Australia, as well as humid zones such as the Amazon, Congo Basin, and the southeastern U.S., and hot coastal areas in the Middle East.
Professor John Marsham, a co-author, added that while their current findings focus on daily rainfall and temperature patterns, future research could explore hourly data to support near real-time prediction capabilities.
These insights could significantly enhance preparedness in regions most vulnerable to the growing threat of humid heat, supporting both public health and climate resilience efforts.
Source:https://phys.org/news/2025-04-rainfall-patterns-trigger-extreme-humid.html
This is non-financial/medical advice and made using AI so could be wrong.
