How Much Water Is in the Air?

The atmosphere is like a giant, invisible sponge, absorbing and releasing water through a process called the water cycle. Globally, the atmosphere contains approximately 12,900 cubic kilometers of water vapor at any given time, approximately 7 times more than all the world’s rivers combined. Though this water is invisible to us in its vapor state, it plays a huge role in weather patterns, cloud formation, and even climate. 

 

 

Interestingly, this water is not evenly distributed. Warmer regions and areas near large bodies of water tend to have more water from air, while cooler and drier places, such as deserts or high altitudes, have less. 

When discussing how much water is in the air, two important terms come into play: absolute humidity and relative humidity.

 

• Absolute Humidity is the actual amount of water vapor present in a given volume of air, usually expressed in grams of water per cubic meter (g/m³). This measurement doesn’t change with temperature — it’s a direct count of water vapor molecules in the air. 

 

• Relative Humidity, on the other hand, is more commonly discussed. Expressed in “% RH,” relative humidity measures how much water vapor the air is holding relative to the maximum amount it can hold at a given temperature. Warm air can hold more water vapor than cold air, which is why relative humidity can vary greatly depending on temperature. 

 

For example, the air might feel very humid on a hot day because warm air can hold more water vapor. The same amount of water vapor in cooler air would feel less humid because the air’s capacity to hold moisture decreases as temperatures drop. 

Several factors affect how much water vapor the air can hold, and therefore, how much water from air can be harvested. These factors include temperature, location, and altitude. 

 

Temperature’s Impact on Water Vapor

 

This is the primary factor. Warm air can hold significantly more water vapor than cold air. For instance, at 30°C (86°F), a cubic meter of air can hold about 30 grams of water vapor, but at 10°C (50°F), it can only hold about 9 grams. So, generally speaking, warmer climates naturally have more potential for water from air collection.

 

Geographical Location and Water Vapor Concentration

 

Geographical factors like proximity to oceans, lakes, or rivers influence how much water vapor the air holds. Coastal areas and tropical regions tend to have higher humidity levels because of the large amounts of water available to evaporate into the atmosphere. Deserts, on the other hand, have much lower humidity, making it more challenging to extract water from air 

 

Altitude and Its Effect on Atmospheric Moisture

 

Air pressure decreases as altitude increases, which affects the air’s ability to hold water vapor. The air is cooler and thinner at higher altitudes, holding less moisture. This is why mountaintops tend to be dry, even when surrounded by clouds.

 

Given the vast amounts of water vapor in the atmosphere, innovative technologies have been developed to harvest water from air, a concept that has the potential to transform water access in arid regions specifically. 

 

Existing technologies, known as atmospheric water generation (AWG), most commonly work by cooling air to the point where water vapor condenses, much like how water droplets form on the outside of a cold glass. This condensation is collected, filtered, and mineralized, if intended for human consumption. The effectiveness of such systems is highly dependent on the amount of water vapor present in the air, meaning in arid and semi-arid regions where water is needed the most, they will typically be challenged. 

 

Another approach is based on desiccants — materials that absorb water vapor from the air — followed by an energy intensive heating process required to release the water molecules from the desiccant material. This method can extract water from air even in dry regions but depends on a very high energy input. 

 

Atmospheric water harvesting based on nano-engineered reticular materials can generate potable water from air even at humidities below 20% and without the need for any external energy input, leveraging nothing but free ambient renewable energy. Find out more about such systems here.  

As freshwater sources become increasingly strained due to population growth, pollution, and climate change, finding alternative ways to access clean water is more crucial than ever. Extracting water from air presents a sustainable solution with huge potential for arid regions and desert climates where traditional water sources are scarce.  

 

 

Tapping into the vast reservoir of water vapor in the atmosphere could provide a renewable and reliable supply of fresh water, reducing our dependency on shrinking freshwater sources. But to fully unlock this potential, we need transformational advancements in atmospheric water harvesting technologies. Overcoming current limitations will enable us to extract water from air on a larger scale, bringing a critical new resource to regions facing severe water shortages and helping to address the global water crisis. Find out more about how we at Atoco are working on bringing an end to water scarcity: The End of Water Scarcity.

Atoco is a leader in climate technology, founded by Professor Omar Yaghi, the pioneer of Reticular Chemistry. Atoco leverages reticular materials such as Metal organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs) to develop breakthrough solutions for carbon capture and atmospheric water harvesting.

These technologies, designed with atomic precision, are engineered to tackle global and most pressing challenges: climate change and water scarcity.