METEOROLOGY – HUMIDITY & WATER VAPOUR CALCULATOR
Vapour Pressure Deficit
A precise tool.
What is the Vapour Pressure Deficit & How does it work?
Vapour pressure deficit (VPD) is a measure of the difference between the actual water vapour present in the air and the maximum amount of water vapour that the air can hold at a given temperature. It is an important factor in plant physiology, influencing transpiration rates and stomatal conductance.
VPD = e_s – e_a
VPD = Vapour Pressure Deficit, e_s = Saturation Vapour Pressure, e_a = Actual Vapour Pressure
Saturation vapour pressure is the maximum amount of water vapour that air can hold at a specific temperature. Actual vapour pressure is the current amount of water vapour present in the air.
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Frequently Asked Questions
What is Vapour Pressure Deficit?
Vapour Pressure Deficit (VPD) measures the difference between the actual water vapour in the air and the maximum amount of water vapour it can hold at a given temperature.
How do I calculate VPD?
To calculate VPD, subtract the actual vapour pressure (e_a) from the saturation vapour pressure (e_s).
Why is VPD important in plant physiology?
VPD influences transpiration rates and stomatal conductance in plants, affecting their water use and photosynthesis.
What factors affect saturation vapour pressure?
Saturation vapour pressure is influenced by temperature; higher temperatures increase the maximum amount of water vapour air can hold.
How does VPD impact plant growth?
High VPD can lead to increased transpiration, potentially causing plants to lose more water than they absorb, which can stress them.
Can VPD be used in agriculture?
Yes, VPD is crucial for agricultural practices as it helps farmers manage irrigation and understand plant water needs.
What units are typically used for VPD?
VPD is often measured in kilopascals (kPa) or hectopascals (hPa).
Results are for informational purposes only and do not constitute professional advice.