Isn’t this sunset beautiful? I am sure that many of us would love this photograph.

BUT do you know that this is an indication that the air we are breathing is polluted?
This stunning red sunset that we anticipate is caused by a high concentration of aerosols in the atmosphere. Not so beautiful after all right? 

Here’s a short lesson for you guys!
Incoming solar radiation passes through the atmosphere while going through a few different processes, namely absorption, reflection/scattering, and transmission. Just as the name suggests, absorption is when solar radiation is being absorbed by the atmosphere, thus increasing the temperature. As for transmission, incoming solar radiation passes through the atmosphere unobstructed as it reaches the Earth’s surface as direct radiation. Finally, reflection/scattering refers to radiation being diffused and thus decreasing the intensity of the incoming radiation. 

There are three types of scattering, Rayleigh scattering, Mie scattering and non-selective scattering and what causes the beautiful red sunset we love is Mie scattering. 

Scattering occurs when there are scattering agents in the atmosphere that will redirect the radiation when it interacts. Mie scattering happens when there are large scattering agents such as aerosols and dust in the atmosphere. Mie scattering is mostly forward unlike rayleigh scattering which scatter radiation forward and backward. In contrast to rayleigh scattering which primarily affects the shorter wavelengths, Mie scattering interacts with most of the wavelengths across the visible spectrum, causing the sky to appear hazy, grey, and the breathtaking red sunset which is enhanced by heavy air pollution. 

Though we always look forward to this spectacular phenomenon, let us take some time to think about the air we are breathing too! Would we really want to breathe in such polluted air? 

Your environmental buddy,
Jeanice

References:

Aguado, E., & Burt, J. E. (2013). Understanding weather and climate (6th ed.). Upper Saddle River, NJ: Pearson Education.

Jeff Hollett. (N.D) Red Sunset Lake. [Online image].
Retrieved from https://isorepublic.com/photo/red-sunse