Air is the composition of gases like nitrogen, oxygen, carbon dioxide, dust particles, smoke, and water vapor. The existence of moisture (water vapor) in the air is called humidity. Absolute humidity and relative humidity are two ways to measure the steam content in the air.
Absolute Humidity vs Relative Humidity
The main difference between absolute and relative humidity is that absolute humidity is the actual quantity of water vapor in the air irrespective of its temperature. On the other hand, the ratio of the actual quantity of water vapor in the air to the quantity of water vapor air can detain until saturation at that temperature is known as relative humidity.
The mass of moisture existing in a given volume of air is referred to as absolute humidity. Dividing the quantity of moisture in grams (g) by the air volume in a meter cube (m3) provides the measurement of absolute humidity. As a result, absolute humidity is measured in grams per cubic meter.
The quantity of water vapor relative to the highest moisture air can detain at that temperature is referred to as relative humidity. The unit does not exist in the case of relative humidity as it is calculated in percentage.
Comparison Table Between Absolute Humidity and Relative Humidity
| Parameters of Comparison | Absolute Humidity | Relative Humidity |
| Definition | Absolute humidity refers to the quantity of moisture existing in the air at any given time | The quantity of moisture existing in the air in comparison to the highest amount it can detain at a given temperature is referred to as relative humidity |
| Temperature | It does not take temperature into account | It takes temperature into account |
| Saturation humidity | It does not take the maximum possible water vapor concentration in the air into consideration | It takes saturation humidity at a particular temperature into consideration |
| Unit | g/m3 is the standard unit to measure absolute humidity | The unit does not exist in the format of relative humidity as it is calculated in percentage |
| Scientific accuracy | It is the most scientifically precise method to measure the humidity level in the air | It is the comparatively less accurate scientific method |
| Comprehensive easiness | Not easy for the general population to know the humidity level in terms of absolute humidity | Easy for the general population to understand in the format of relative humidity as it has no unit |
What is Absolute Humidity?
Absolute humidity measures the actual quantity of moisture in the atmosphere. Dividing the quantity of moisture in grams (g) by the air volume in a meter cube (m3) provides the measurement of absolute humidity. g/m3 is the SI unit while measuring humidity in absolute terms. It does not consider temperature in its ambit. It is just about the mass of moisture in a quantity of air, irrespective of the air’s temperature. As the quantity of moisture rises, absolute humidity also increases.
Saturation humidity is not included in the computation of absolute humidity. Saturation humidity is the highest quantity of moisture the air can detain at a particular temperature. Therefore, it becomes difficult for the general population to understand the level of humidity present in the air. In other words, the unit of absolute humidity, which is g/m3 is not easily comprehensible to the general people.
Absolute humidity is the most accurate method to scientifically measure the humidity level. However, it is not used on a large scale compared to relative humidity. Scientists and trained professionals measure humidity in terms of absolute humidity.
What is Relative Humidity?
The ratio of the quantity of moisture in the air to the utmost amount of moisture the air can detain at that temperature is known as relative humidity. In other words, Water vapor is also measured by relative humidity, but this time about the temperature of the air. At a given temperature, it is stated as a percentage of the total quantity of moisture that the air can detain. As a result, relative humidity, unlike absolute humidity, has no units.
In contrast to absolute humidity, relative humidity takes temperature into account. It also considers the highest quantity of moisture that air can store at any particular temperature, known as saturation humidity. The relative humidity is higher when air is cooler and lower when air is warmer because warm air can detain more moisture than cold air.
The application of the relative humidity format is much more than absolute humidity. The weather forecasting of humidity level that we see in the news is done in terms of relative humidity as it is easier to comprehend in the format of relative humidity than that of absolute humidity by the general population. Relative humidity compares the quantity of moisture in the air to what the air can detain at the utmost level at that temperature. That’s why getting a fair idea of the humidity level becomes easier. However, relative humidity is less precise in scientific view than absolute humidity.
Main Differences Between Absolute Humidity and Relative Humidity
- Absolute humidity refers to the actual quantity of moisture in the air. In contrast, relative humidity refers to the ratio of the quantity of moisture in the air to the maximum quantity of moisture the air can detain at a particular temperature. While relative humidity considers temperature, this is not true with absolute humidity.
- The absolute humidity’s standard unit is g/m3 because absolute humidity is measured in grams of steam per cubic meter of air volume. On the other hand, no unit exists for relative humidity and is calculated in percentage.
- Saturation humidity (the maximum water vapor holding capacity of air at a given temperature) is considered in relative humidity but not in absolute humidity.
- Relative humidity is a less scientifically accurate method to measure the humidity level in the air compared to absolute humidity, which is the most scientifically accurate method.
- Weather forecasting happens in the format of relative humidity as it is easy to comprehend the humidity level by the general population. However, absolute humidity is mainly limited to scientists and trained professionals.
Conclusion
To sum up, absolute and relative humidity are two methods to measure the air’s humidity level. While absolute humidity is the most scientifically accurate method to measure humidity in the air, relative humidity is used because it is easier for the general public to understand.
