Today we are going to learn how to find dew point and relative humidity using the hygrometric table. The hygrometric table is very important for weather observers, meteorologists, and weather forecasters. It is a table that shows the amount of R.H. and Dewpoint. This table can be obtained from any meteorological office or online. We will discuss how to find the dew point and relative humidity using this table
Important Points about Dew Point and Relative Humidity :
1. Dew point is a measure of the temperature at which water vapor in the air condenses to liquid form. The dew point is the temperature at which water condenses from the atmosphere. The dew point can also be termed as the freezing point of water vapor in the atmosphere around us. Dew point and relative humidity are important for many reasons.
2. The dew point can be used to calculate the amount of water vapor in a given volume of air.
3. The dew point can be used to determine whether an object is wet or dry since the dew point is the temperature at which water vapor begins to condense on the object.
4. Relative humidity can be used to calculate the percentage of water vapor in a given volume of air.
5. Relative humidity can be used to determine the moisture content of a substance, such as food or building material.
6. The relative humidity can be used to determine the saturation humidity, which is the maximum amount of water vapor that can be contained in a given volume of air.
7. Relative humidity can be used to determine the dew point, which is the minimum temperature required to produce a measurable quantity of water vapor in a given volume of air.
How To Find Dew Point and Relative Humidity Using Hygrometric Table.
We live in a world of extremes. The weather is a constant source of wonder, excitement, and dread. Depending upon our scenario we love it when the sun shines and the wind blows. We hate it when the rain pours, the snow falls, and the sleet freezes us. We can’t control the weather, but we can control our response to it. And that’s where hygrometry comes in. Hygrometry is the science of measuring the amount of water vapor in the atmosphere. It measures the air’s humidity.
In the hygrometric table, the relative humidity and dew point are written with respect to dry bulb temperatures verse the difference between dry bulb and wet bulb temperatures. Finding Relative Humidity and Dew point using a Hygrometer is very easy. Follow the following easy steps:
1. Read a Dry Bulb temperature:
Read the temperature of the dry bulb thermometer. For example, let’s say it is -13 degrees Celcius.
2. Read a Wet bulb Temperature:
Read the temperature of the wet bulb thermometer. For example, let’s say it is -14 degrees Celcius.
3. Find the Difference between Dry bulb and wet bulb Temperatures:
Find the difference between dry bulb and wet bulb temperatures by Subtracting wet bulb temperature from dry bulb temperature. for example, a Dry bulb temperature: is -13 degree celsius, and a Wet bulb temperature is -14 degrees Celcius. Their difference -13-(-14)=+1 degree Celcius.
4. Look at the Hygrometric Table:
Now Look for the Dry bulb temperature and its corresponding Dry and wet bulb temperature difference. from our previous example
Dry bulb temperature: -13 degrees Celcius
Wet bulb temperature: -14 degrees Celcius
Difference between Dery bulb and wet bulb(Depression of the wet bulb): +1 degree Celcius.
In the hygrometric table, we have to look for -13 degrees celsius in the dry bulb and +1 degree celsius in the difference column. According to the table, the Dew point is -18.1 degree celsius and the Relative humidity(R.H) is 62%. Similarly, D.P and R.H for any value can be calculated using the same method explained above.
Note:
To calculate the Dew point or relative humidity, we need the absolute values for the dry and wet bulb temperature difference. As we know the differences between dry and wet bulb temperatures are always positive and never negative.
Final Thoughts:
Dew point and R.H can be found using a hygrometer. A hygrometer is an instrument that measures the amount of water vapor in the air. The hygrometer is used to measure the dew point, which is the lowest temperature at which the moisture in the air condenses to form dew on a surface. The dew point is measured in degrees Celsius (°C). Relative humidity is the ratio of the actual relative humidity of the air to the maximum possible relative humidity. The maximum possible relative humidity is 100 percent. Relative humidity of 100 percent means that the air is saturated with water vapor.
