PUNE: If this year's prolonged monsoon and endless overcast skies have made it feel like the Sun has gone missing, there is data to back up the impression.
In a new study by Banaras Hindu University (BHU), Pune-based Indian Institute of Tropical Meteorology (IITM) and India Meteorological Department (IMD), among others, scientists have found that sunshine hours across most parts of India have been steadily declining over the past three decades - a trend linked to thicker cloud cover and rising aerosol pollution.
The research, published in " Nature's Scientific Reports " this month, examined sunshine-hour data from 20 met stations across nine regions between 1988 and 2018. It found the annual sunshine hours - the duration when sunlight is strong enough to be recorded as a sunshine hour - have declined in all regions, except northeast where a marginal seasonal "levelling off" was seen.
BHU scientist Manoj K Srivastava told TOI: "On average, the west coast saw sunshine hours fall by 8.6 hours per year, while the north Indian plains recorded the steepest drop at 13.1 hours a year."
"The east coast and Deccan plateau also showed declining trends of 4.9 and 3.1 hours per year, respectively. Even the central inland region showed a loss of about 4.7 hours per year."
The study said sunshine increased between Oct and May - the drier months - but declined sharply from June to Sept, coinciding with the monsoon. The scientists associated with the study attributed the long-term "solar dimming" to higher aerosol concentrations - tiny particles released from industrial emissions, biomass burning and vehicular pollution.
"These aerosols act as condensation nuclei, creating smaller and longer-lived cloud droplets that keep skies overcast for extended periods. This year's monsoon, too, has been marked by persistently cloudy skies across much of India, especially over the west coast, central India and Deccan plateau, which saw frequent overcast conditions even on days without rain. Though the study period spans till 2018, trends remain just as relevant today, as the same haze, humidity and cloud patterns persist - if anything, more strongly than before," one scientist said.
"Higher aerosol numbers increase the residence time of clouds in the atmosphere, reducing the hours of sunlight reaching the ground," Srivastava said. The scientists said the decline in sunshine hours has major implications for solar energy generation, agriculture and climate modelling. While India has emerged as one of the fastest-growing solar markets, reduced solar incidence could affect power output and long-term planning for renewable infrastructure.
In a new study by Banaras Hindu University (BHU), Pune-based Indian Institute of Tropical Meteorology (IITM) and India Meteorological Department (IMD), among others, scientists have found that sunshine hours across most parts of India have been steadily declining over the past three decades - a trend linked to thicker cloud cover and rising aerosol pollution.
The research, published in " Nature's Scientific Reports " this month, examined sunshine-hour data from 20 met stations across nine regions between 1988 and 2018. It found the annual sunshine hours - the duration when sunlight is strong enough to be recorded as a sunshine hour - have declined in all regions, except northeast where a marginal seasonal "levelling off" was seen.
BHU scientist Manoj K Srivastava told TOI: "On average, the west coast saw sunshine hours fall by 8.6 hours per year, while the north Indian plains recorded the steepest drop at 13.1 hours a year."
"The east coast and Deccan plateau also showed declining trends of 4.9 and 3.1 hours per year, respectively. Even the central inland region showed a loss of about 4.7 hours per year."
The study said sunshine increased between Oct and May - the drier months - but declined sharply from June to Sept, coinciding with the monsoon. The scientists associated with the study attributed the long-term "solar dimming" to higher aerosol concentrations - tiny particles released from industrial emissions, biomass burning and vehicular pollution.
"These aerosols act as condensation nuclei, creating smaller and longer-lived cloud droplets that keep skies overcast for extended periods. This year's monsoon, too, has been marked by persistently cloudy skies across much of India, especially over the west coast, central India and Deccan plateau, which saw frequent overcast conditions even on days without rain. Though the study period spans till 2018, trends remain just as relevant today, as the same haze, humidity and cloud patterns persist - if anything, more strongly than before," one scientist said.
"Higher aerosol numbers increase the residence time of clouds in the atmosphere, reducing the hours of sunlight reaching the ground," Srivastava said. The scientists said the decline in sunshine hours has major implications for solar energy generation, agriculture and climate modelling. While India has emerged as one of the fastest-growing solar markets, reduced solar incidence could affect power output and long-term planning for renewable infrastructure.
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