-Sristi Raj Rai, Amity University Kolkata
Aerosols are minute solid particle/liquid droplets suspended in atmospheric air or other gaseous phases. Various natural (volcanic eruptions, dust storms) and anthropogenic activities (air pollution) give rise to the formation of these aerosols. The particles acts as the core upon which water vapor condense, leading to cloud formation. These cloud-aerosol interactions have an impact on the convection currents in the atmosphere and are the key to an in-depth understanding of the climate and weather. An increase in aerosols concentration has been linked to lightning and storms in the past. Moreover, observations suggest that the lightning frequency is more along the shipping routes, and thunderstorms have mostly impacted the tropics.
Tristan H. Abbott & Timothy W. Cronin, from the Massachusetts Institute of Technology, decided to lay down a poof via high-resolution atmospheric simulations including the “humidity entrainment” mechanism. They deviated from the previous pathways put forward and suggested that the phenomenon may arise due to a chain of “microphysical invigoration”. A model was devised where cloud behavior was studied under ideal conditions in a volume of the box representing a 128 km wide square of Tropical Ocean. Further, the environment was manipulated by altering various parameters (relative humidity, temperature), allowing room for changes in each grid cells of the box, which were closely monitored. The duo was able to prove that higher aerosol concentration in the cloud resulted in high humidity.
Hence, if a cloud laden with aerosols that suppress rain undergoes evaporation then it is possible to switch dry setting into a humid one. Once the surrounding turns humid, it does not favor the time required to bring down its internal temperature by evaporation of moisture. Due to which earth’s troposphere gets heated up and as warm air rises, so do the clouds. As the cloud ascends to altitudes like 10-15 km, it generates enough space for air currents to turn into thunderstorms. Thus, one can easily conclude from the cloud dynamics study that an increase in the concentration of aerosols increases the frequency as well as the intensity of the thunderstorms. Therefore by controlling pollution or mapping high-aerosols areas, one might have a hand in managing thunderstorms and depicting weather conditions.
SOURCE – Aerosol invigoration of atmospheric convection through increases in humidity” by Tristan H. Abbott and Timothy W. Cronin, 1 January 2021, Science. DOI: 10.1126/science.abc5181
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