A new study finds that dry air mixing into rising warm plumes can help heat and humidity build near the ground, raising the risk of dangerous humid heat.
A drier lower atmosphere can help intensify humid heat.As the climate warms, studies continue to show how extreme heat can affect our health, raising the risk of heat-related illness. Scientists are also learning more about the atmospheric processes that trigger and intensify dangerous heat. A new study points to a hidden factor that could make hot, humid conditions even worse.
The unexpected role of dry air in making humid heat worse
Dry air may not sound like an ingredient for oppressive humidity. However, according to a new study in Geophysical Research Letters, dry air can indirectly allow hotter, more humid conditions to develop near the surface.
The main interaction takes place in the lower troposphere, the lowest part of the atmosphere. When a column of warm, moist air rises, some of the surrounding dry air mixes into it by a process known as entrainment. This causes the plume to weaken and enables more heat and moisture to accumulate close to the ground.
When wet-bulb temperatures climb, the body has to work harder to stay cool on hot, muggy days.The buildup of moisture and heat raises wet-bulb temperatures. Wet-bulb temperature measures both heat and humidity, showing how hard it is for sweat to cool the body down.
Testing the effect of dry-air mixing
To see how much this process matters, University of St. Andrews researchers R. Jha and M.P. Byrne
Original Record.
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