By Our Reporter
SHILLONG, Dec 24: A decade-long scientific assessment has found that increasing air pollution is closely associated with a marked decline in rainfall in Mawsynram, globally known as the wettest place on earth.
The study, published in the Journal of the Indian Society of Remote Sensing, examined satellite observations of atmospheric aerosols alongside rainfall data from 2014 to 2023 to understand long-term climatic changes over the region. The research was conducted by Mamta Devi, Sumit Kumar Mishra, Kartika Pandey, Supreet Kaur, Anikender Kumar, Vijay Kumar Soni, Amarendra Singh and Atul Kumar Srivastava.
Researchers reported that aerosol levels over Mawsynram increased by approximately 14.6 percent over the ten-year period. During the same time, annual rainfall declined by nearly 14 percent, decreasing from 10,235 millimetres in 2014 to 8,838 millimetres in 2023.
The analysis found a statistically significant negative correlation between aerosol optical depth and rainfall, indicating that higher concentrations of airborne particles were consistently linked to reduced precipitation.
Aerosols from sources such as biomass burning, vehicular emissions and long-range pollution transport were found to influence cloud formation and rainfall efficiency.
According to the study, higher aerosol concentrations result in clouds forming with smaller droplets which delay their ability to merge into larger raindrops. This aerosol indirect effect suppresses rainfall even in moisture-rich environments like Meghalaya.
The impact was most pronounced during the pre-monsoon and winter seasons, when aerosol levels were highest. The study noted that aerosol optical depth increased steadily by about 0.007 per year, with fine particles becoming increasingly dominant in the atmosphere.
The researchers also observed changes in atmospheric heating over the region. Winter heating rates rose from 0.4 to 0.6 Kelvin per day, while pre-monsoon heating increased from 0.5 to 0.7 Kelvin per day over the decade. These changes coincided with reduced sunlight reaching the surface, a process known as surface dimming.
The authors said the findings underscore the complexity of aerosol–cloud–rainfall interactions in climatically sensitive regions and cautioned that such effects are often underestimated in climate models. They added that observations from Mawsynram provide important insights into broader regional and global climate processes.
