Study Finds That Drought Can Add Two Days to Heat Waves

A recent study finds that drought can lengthen heat waves if these two features occur at the same time.  According to NOAA/NIDIS "researchers examined the influence of drought on heat wave intensity, duration, and human exposure to extreme heat using air temperature, soil moisture, and soil temperature observations from across the country."

Research team members found that drought increased the average duration of heat waves by 13 to 48 hours at most of the weather stations included in the study.  Nationally, heat waves during drought had an average of about nine more hours of extreme heat compared to heat waves that occur in non-drought conditions.  

What Role Do Dry Soils Play?

Researchers say soil moisture is likely one component driving this phenomenon.  It is understood that dry soils reduce local evapotranspiration (ET) rates, but this study also found that the soils retained more heat.  The combination of reduced ET and warmer soils likely allowed heat to escape into the atmosphere, driving warmer air temperatures.  This effect is particularly impactful in the early evening, driving warmer evenings.  Measuring soil moisture and soil temperature conditions therefore could improve assessments of how crops, economies, wildfire risk, infrastructure, and human health are impacted by extreme heat.

Research results were recently published in the Journal of Applied Meteorology and Climatology.

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