Excess Aerosols Current Affairs - 2020

NASA: Air Pollution in India at 20 year low

On April 22, 2020, NASA (National Aeronautics and Space Administration) announced that Air Pollution in India has reached 20 year low.

Highlights

According to the data published by NASA, the Aerosol Optical Depth in 2020 has been the least as compared to the average of 2016 to 2019. Aerosol Optical Depth is absorption of light by airborne particles in the atmosphere. When the aerosols are near the surface, the optical depth of 1 or above indicate hazy conditions.

The AOD was 0.7 in 2016 and has now reached 0.1. The patterns were observed by the MODIS model. MODIS is Moderate Resolution Imaging Spectroradiometer

Aerosol Optical Depth

The aerosols are particles in atmosphere released due to anthropogenic activities such as industries, vehicles and natural events such as dust storms, fires, etc. The presence of Aerosols in the atmosphere is also affected by particulate matter in the atmosphere.

The Aerosol Optical Depth is the quantitative measure of aerosols present in the atmosphere. It measures the extinction of light when it passes through the atmosphere. As AOD increases, the rate of extinction of light increases.

Erratic monsoon rainfall in India partly due to air pollution: Study

According to recent study by scientists from IIT Kanpur, erratic behaviour of monsoon rainfall, including phenomenon of concentrated heavy rainfall on small number of days in localized area can be attributed to the rising air pollution, especially the increase in suspended particles in the atmosphere. The study has found that high pollution levels are not just changing cloud shape and size and depth, but also its microstructure.

Key Findings of this study

Excess aerosols, suspended solid particles like dust, smoke and industrial effluents in atmosphere is changing cloud patterns, its shape, size and other properties like temperature, which in turn is resulting in variability in rainfall over Indian sub-continent during monsoon season.

Aerosols are extremely important for cloud formation. In absence of aerosols, no clouds can be formed and consequently no rainfall will take place. But due to increase in aerosol content in atmosphere, there is direct consequence of rising air pollution interfering with stable cloud formation system and influencing rainfall patterns.

In short term, these changes in cloud structure and cloud dynamics lead to sharp variability in rainfall, which is similar to rainfall patterns witnessed very often in India in last few years. In the long term, it is likely to lead to overall suppression of rainfall during the monsoon season.

Significance of this study

The linkage of air pollution to rainfall activity is not new and has been established in many earlier studies as well. But this is for the first time, study has given details of the exact changes that take place inclouds over India as result of increase in aerosols. It also shows how it is leading to reduction in difference in day and night temperatures and also impacting rainfall activity. For this study, researchers had analysed satellite data and data from atmospheric computer models from last 16 years to make an assessment of likely impacts of changes in cloud behaviour over land area of about 16 lakh square kilometres.