Why in the News?
Scientists have coined a new term, “thirstwave”, to describe spikes in evaporative demand, where a warmer atmosphere draws more water from plants, soil, and trees.
What is Evaporative Demand?
- Definition: Evaporative demand is the measure of how much water the atmosphere can potentially absorb from land, plants, and water surfaces if there is unlimited water available. It tells us how “thirsty” the atmosphere is.
- Nature of Measurement: It is not about how much water is actually lost but how much could be lost if water was fully available. It depends on weather conditions, not the amount of water in the soil.
- Standard Metric: The most widely used metric to quantify this is Standardized Short-Crop Reference Evapotranspiration (ETos)—which assumes a 12 cm grass surface with unlimited water availability.
- Impact of Global Warming: As global warming increases atmospheric heat, evaporative demand also rises, making the air more “thirsty”.
- Key Features:
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- Simplified Model: ETos simplifies evapotranspiration by assuming fixed vegetation properties and only variable weather conditions.
- Indicators of Stress: An increase in ETos indicates higher temperatures, lower humidity, faster wind, and stronger solar radiation.
- Effect on Soil and Crops: Rising evaporative demand leads to more rapid drying of soil and plants, even with ample irrigation.
- Agricultural Relevance: This directly affects irrigation scheduling, crop productivity, and climate-resilient farming strategies.
What is a Thirstwave?
- Origin: “Thirstwave” is a newly coined term (2025) by Meetpal Kukal and Mike Hobbins to describe three or more consecutive days of extreme evaporative demand.
- Definition: A thirstwave is a period of sudden and intense increase in evaporative demand, caused by hot, dry, and sunny weather. It means the atmosphere becomes extremely “thirsty” and starts pulling water rapidly from soil, plants, and water bodies, even if they already have limited moisture.
- Distinction from Heatwaves: Unlike heatwaves, thirstwaves account for multifactorial stress, combining temperature, humidity, wind, and solar input.
- Thirstwave in India: There is no dedicated data yet on thirstwaves in India, but researchers are beginning to investigate, especially in South Asia’s climate-vulnerable zones.
| [UPSC 2018] Which of the following leaf modifications occur(s) in the desert areas to inhabit water loss?
1. Hard and waxy leaves 2. Tiny leaves 3. Thorns instead of leaves Select the correct answer using the code given below: Options: (a) 2 and 3 only (b) 2 only (c) 3 only (d) 1, 2 and 3 * |
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