Does rain improve air quality?

We continuously breathe in and breathe out. Therefore, good air quality is an essential need. However, in packed cities, such as Jabodetabek, clean air is increasingly becoming rare. Some of you may already know that air quality is not only affected by human activities. There are several natural phenomena that also play a role, one of which is rain.

Rain is claimed to cleanse air pollution

Rain is a natural phenomenon in which water droplets fall from the sky to the earth's surface due to condensation. Generally, rain is often assumed to have the ability to clear smoke and reduce air pollution. Several studies have also shown that rainfall can improve air quality.

Technically, raindrops can draw hundreds of PM2.5 particles to their surface as they move through the atmosphere before falling to the ground. This process of attraction between water droplets and aerosols is called coagulation. Thus, raindrops can remove airborne pollutants, like noxious gases and particulates.

Rainfall frequency is predicted to increase until the end of 2022

Recently, the BMKG analyzed that the IOD index in August showed negative IOD conditions and will remain negative until the end of 2022. Negative Indian Ocean Dipole (IOD) is an event of decreasing sea surface temperature in the western Indian Ocean which causes higher air pressure in this region compared to the east coast of the ocean (which is located closer to Indonesia). This negative IOD has an impact on increasing the frequency of rain in Indonesia.

“So, if rainfall is predicted to increase, the air quality will improve!” - You might be thinking something like this.

But will it really be like that? We’re afraid it’s not really. Let's dive into this!

Rain has only an 8.7% effect on PM2.5 reduction

Several studies show that rain has a relatively small impact on reducing air pollutants (0-30%). The most noticeable impact is after hefty rainfall, where air pollutants are cut by up to 30%. In addition, a study from China revealed that minor pollutants were reduced by only 8.7%. The effect on PM2.5 is close to zero for light to moderate rain.

This is because rain is more likely to wash away particles with larger concentrations and sizes.

Due to the effective removal of particulate pollutants, air quality is generally improved after the precipitation process. Particle removal is affected by ambient temperature, rainfall intensity, particle size, and pollutant concentration. The larger the initial concentration of particulates, the better the rain-induced removal effect. The effect is even more pronounced for PM10 than for PM2.5. PM10, particles less than 10 μm in diameter, will be more easily suspended with rainwater than PM2.5, which is less than 2.5 μm in diameter.

Monitoring air quality regularly is the key

Air quality conditions can be unpredictable. However, now you know that air quality doesn't always improve after it rains. You may experience good air quality after the rain, but you may also face air conditions that never improve. 

Thus, monitoring air quality needs to be done at all times before starting outdoor activities. This needs to be done to keep your body healthy and avoid air pollution's short-term and long-term effects. You can use the nafas app to stay updated on air quality. Always wear your mask when the air pollution is in an 'unhealthy' condition, or in a worse condition.

Now it’s your time to maximize your nafas experience with these tips!

References:

Feng, X., & Wang, S. (2012). Influence of different weather events on concentrations of particulate matter with different sizes in Lanzhou, China. Journal of Environmental Sciences, 24(4), 665–674. https://doi.org/10.1016/s1001-0742(11)60807-3

Liu, Z., Shen, L., Yan, C., Du, J., Li, Y., & Zhao, H. (2020). Analysis of the Influence of Precipitation and Wind on PM2.5 and PM10 in the Atmosphere. Advances in Meteorology, 2020, 1–13. https://doi.org/10.1155/2020/5039613

Related Tags