Evaporative Demand

Evaporative demand determines the near-maximum of how much water will evaporate from a given piece of land if sufficient water is available.

Evaporative Demand

Evaporative Demand Latest News

The rising evaporative demand in India is exposing significant gaps in the country’s climate data and research.

About Evaporative Demand

  • Evaporative demand is a measure of how thirsty the atmosphere is. 
  • It determines the near-maximum of how much water will evaporate from a given piece of land if sufficient water is available.
  • It does not necessarily relate to actual evaporation rate, as if there is little water supply there can only be a small evaporation rate, no matter how large the demand.
  • It is driven by atmospheric factors including temperature, wind speed, humidity and cloud cover. 
  • Periods of high evaporative demand are connected to droughts and increased fire danger.
  • Tracking extended periods with above normal evaporative demand can be a useful way to detect drought onset, drought intensification, and elevated fire danger. 
  • Above normal temperatures, clear skies, and wind speed, and below normal humidity all drive evaporative demand up and lead to quicker drying at the surface. 
  • Soil moisture is reduced which leads to less water available for plants and vegetation becomes stressed and more flammable. 
  • When extended periods of below normal precipitation overlap with extended periods of above normal evaporative demand fuels become critically dry favoring rapidly spreading wildfires.

What is a Thirstwave?

  • It denotes three or more contiguous days of intense evaporative demand.
  • While heat waves are caused by particular temperature and wind patterns, a thirstwave is the product of temperature, humidity, solar radiation, and wind speed.
  • When temperatures rise, the consequences include more heat as well as the mechanics of water exchange between land and atmosphere, which in turn alters humidity, wind, and solar radiation.
  • In a warming world, the researchers found that thirstwaves have grown more intense, are more frequent, and are lasting longer.

Source: TH

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Evaporative Demand FAQs

Q1. What does evaporative demand mean?+

Q2. What atmospheric condition causes increased evaporative demand?+

Q3. What does high evaporative demand indicate about surface moisture?+

Q4. What is the relationship between evaporative demand and droughts?+

Q5. What impact does high evaporative demand have on vegetation?+

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