Research has found that sudden, severe dry spells known as flash droughts are becoming more intense globally, except in mountainous Central Asia where flash drought extent is actually shrinking. The increase in intensity of flash droughts is being driven by heat and changes in precipitation patterns due to a warming climate. These flash droughts arrive suddenly, within weeks, impacting communities that are often not prepared and causing lasting effects. The study, led by climate scientist Maheshwari Neelam, is the first to quantitatively analyze the global incidence of flash droughts, mapping hotspots and regions of rapid increases over the past few decades.
The study focused on tracking three critical measures of drought severity: speed of onset, duration, and geographic extent. By analyzing 40 years of NASA’s MERRA-2 climate data, from 1980 to 2019, the researchers aimed to improve prediction and disaster preparedness for flash droughts. The findings revealed that in many parts of the world, flash droughts are extending over larger areas, for longer periods of time, and with faster onset speeds. This information can be utilized by early warning systems to incorporate rates of change in flash drought characteristics into risk assessment and disaster preparedness strategies.
Certain regions, such as South America and parts of Africa, are experiencing strong intensification in all three dimensions of flash droughts. For example, in the watersheds of South America, the onset of flash droughts is getting faster by about 0.12 days per year, leading to significant changes over the course of a decade. Additionally, the extent of flash droughts in South America is increasing by 1 to 3% per year. The study also identified land cover as an important factor in flash drought vulnerability, with savanna and grasslands being more susceptible, especially in humid and semi-humid climates.
In Central Asian watersheds, including regions like the Himalaya Karakoram, Tianshan, and Hindu Kush, flash drought extent has actually been shrinking over the study period, contrary to the global trend. The researchers attribute this phenomenon to climate-driven changes in precipitation, melting snowpack, and a shift from snow to rain in the mountains, which has kept soils moist. However, these changes can also lead to an increase in flash floods in the region. Neelam emphasized the importance of understanding landscapes’ response to disasters on a watershed scale for assessing water budgets and water management, transcending geopolitical boundaries.
Overall, the study highlights the importance of monitoring and addressing the increasing incidence of flash droughts around the world, especially in regions where they are intensifying. By utilizing data-driven approaches and focusing on critical measures of drought severity, such as onset speed, duration, and extent, researchers and policymakers can better prepare for and respond to these sudden and severe dry spells. Additionally, understanding the role of factors such as land cover and climate-driven changes in specific regions, like Central Asia and South America, can help tailor mitigation strategies to address the unique challenges posed by flash droughts in different environments.