Sunshine-hour data from 20 weather stations was examined.
This year the monsoon lasted for a long time. Due to the sudden rain after monsoon, it seems as if cold has suddenly knocked. Snowfall has also started on the mountains before time. In a new study conducted by Banaras Hindu University (BHU), Pune-based Indian Institute of Tropical Meteorology (IITM) and other institutions including the Indian Meteorological Department (IMD), scientists have found that sunshine hours have been continuously decreasing in most parts of India over the last three decades. This trend is related to dense clouds and increasing aerosol pollution.
The research, published in ‘Nature’s Scientific Reports’ this month (October), examined sunshine-hour data from 20 weather stations in nine regions between 1988 and 2018. It was found that annual sunshine hours have decreased in all regions except the northeastern regions.
BHU scientist Manoj K. Srivastava told Times of India – On an average, there was a decrease of 8.6 hours in sunshine hours every year on the west coast. Whereas the maximum decline of 13.1 hours was recorded in the North Indian plains. The East Coast and Deccan Plateau also saw declines of 4.9 and 3.1 hours per year, respectively. Even the central inland region saw a reduction of about 4.7 hours per year.
Aerosol concentrations attributed
The study said that between October and May, which are the dry months, there was an increase in sunshine. Whereas, from June to September, which coincides with the monsoon, it declined sharply. Scientists associated with the study attributed the high aerosol concentrations to long-term ‘solar dimming’. These include fine particles released from industrial emissions, biomass combustion and vehicular pollution.
These aerosols act as condensation nuclei, forming small and long-lived cloud droplets that keep the sky covered with clouds for long periods of time. This year’s monsoon also witnessed persistent cloud cover over most parts of India, especially the west coast, central India and the Deccan plateau. It is often cloudy here even on days without rain.
This is how the hours of sunlight reaching the earth are decreasing
Srivastava said- However, the study period is till 2018. But its trends are equally relevant even today. Because the same form of mist, moisture and clouds remains. But more strongly than before. He told- Higher amount of aerosols increases the duration of clouds in the atmosphere, which reduces the hours of sunlight reaching the ground. Scientists said the reduction in sunshine hours also has a profound impact on solar energy production, agriculture and climate modeling.