What is Vapor Pressure Deficit (VPD)?

Vapor pressure deficit is another way of saying relative humidity. It means the amount of water vapor in the air compared to how much there would be if the air had 100% relative humidity, which is a total saturation of water vapor.

The higher the vapor pressure deficit, the more likely it is that clouds will form and precipitation will occur.

The pressure of the air that surrounds us is not constant. It changes depending on the weather, time of day, and even who you are with.

Vapor Pressure Deficit is one of the tools that meteorologist use to predict weather. It describes how much the air feels hot and dry compared to the air around it. When temperatures are high, water molecules move faster and bounce off each other more often. Because of this, they have a harder time staying together as a liquid, so they turn into a gas.

Vapor pressure deficit (VPD) is defined as the difference between the partial vapor pressure of water in air and the equilibrium vapor pressure of pure water at a given temperature. In other words, it is an indicator of how much potential energy there is for evaporation.

The higher the VPD, the more water that evaporates from a leaf or any other surface area exposed to humid air. A high VPD often results in high rates of transpiration and plant growth. A low VPD on the other hand indicates low rates of transpiration and little plant growth.