Warming climate intensifies flash droughts worldwide

Warming climate intensifies flash droughts worldwide

Sub: Geography

Sec: Climatology

Tags: flash drought

Flash Droughts:

• Flash drought is simply the rapid onset or intensification of drought.
• It is set in motion by lower-than-normal rates of precipitation, accompanied by abnormally high temperatures, winds, and radiation.
• Together, these changes in weather can rapidly alter the local climate.
• Higher temperature increases evapotranspiration (ET)—the process by which water is transferred from the land to the atmosphere by evaporation from the soil and by transpiration from plants—and further lowers soil moisture (SM), which decreases rapidly as drought conditions continue.

Causes of Flash Droughts:

• Unlike slow-evolving drought caused by a decline in precipitation, flash drought occurs with:
  • Low precipitation
  • Abnormally high temperatures (e.g., heat waves)
  • High winds
  • Changes in radiation
• These rapid changes can quickly:
  • Raise evapotranspiration rates
  • Remove available water from the landscape
• Geographic differences and climate patterns impact flash drought development:
  • Conventional drought can occur year-round at any location
  • Flash drought typically occurs during warm seasons in the central United States
  • Widespread flash drought in the U.S. is often linked to La Niña events

Study on Flash Droughts:

• The study, using 40 years of NASA’s MERRA-2 climate data (1980-2019), is the first to systematically quantify global flash drought occurrences, mapping hotspots and trends.
• Regions worldwide are experiencing larger, longer-lasting flash droughts with quicker onset.
• The study measured drought severity through onset speed, duration, and geographic extent.
• Findings:
  • Flash droughts, characterized by their sudden and severe onset, are becoming more intense globally, except in mountainous Central Asia where their extent is decreasing.
  • This trend is driven by climate change-induced heat and altered precipitation patterns. 
• Geographical impact of flash droughts:
  • It highlights significant intensification in South America, particularly southern Brazil and the Amazon, linked to deforestation, high temperatures, and reduced rainfall.
  • Similarly, parts of Africa, including Congo, Angola, and South Africa, are also identified as hotspots, where high temperatures play a crucial role.
  • The vulnerability to flash droughts is also influenced by land cover, with savanna and grasslands in humid and semi-humid climates being particularly susceptible.
  • In contrast, Central Asia’s high mountain regions, such as the Himalayas and the Hindu Kush, have seen a reduction in flash drought extent due to climate-induced changes in precipitation patterns, melting snowpack, and a shift from snow to rain, which maintain soil moisture but increase the risk of flash floods.

Source: TH