Most people know about a flash flood. Under the warmer conditions of climate change, sudden, abnormal, dry episodes are speeding up, so sadly that may be about to change.
According to a new analysis, over half of all flash droughts now emerge within five days, which is more than in the last two decades.
Compared to our traditional understanding, flash droughts are marked by a rapid intensification of the problem due to a long deficit in precipitation.
The phenomenon has been observed in a number of countries, including the 2012 North American drought, which occurred in the middle of the year, and recent episodes in Australia, China, and Africa.
While these rapid events have been documented in many places, there is still a lot we don't know about flash droughts.
The new study, led by co-first authors Shuo Wang from the Hong Kong, explains that the most important characteristic of flash droughts is the rapid onset phase.
The spatial pattern and temporal variability of the speed of flash drought development is needed to reveal a global picture of flash drought onset.
The researchers analyzed 21 years of hydroclimate data from 2000 to 2020 to provide an overview.
The results show that flash droughts are not increasing in number, but they do seem to be emerging even faster as time goes on.
The researchers explain that the incidence of flash droughts within five days is increasing, which poses a challenge for the monitoring of the problem.
In general, more than 70 percent of flash droughts develop within half a month, and more than 30 percent within 5 days with a high intensification rate, whereas the traditional droughts can take up to six months to develop due to the cumulative effects of related climate.
According to the researchers, flash droughts are likely to be triggered during episodes of atmospheric aridity, characterized by high temperatures, low precipitation, and high vapor pressure deficit.
In terms of geography, flash droughts are most likely to occur in humid and semi-humid regions such as Southeast Asia, East Asia, the Amazon Basin, Eastern North America, and Southern South American.
Wang says that they should pay close attention to the vulnerable regions with a high probability of concurrent soil and atmospheric aridity.
In addition to monitoring vulnerable areas, the findings could help us mitigate the devastation of future flash droughts by hopefully identifying them quicker using the criteria defined here, the researchers suggest.
The criterion of a rapid intensification rate should be taken into account in order to further improve the ability of monitoring and predicting flash droughts.
The change in the state of the climate should be incorporated into flash drought monitoring and prediction so that it remains meaningful in a warming climate.
Nature Communications reported the findings.
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