New Delhi: It’s raining less in India.
Or, to be scientifically exact, it’s increasingly raining less in at least 67% of India.
That’s the conclusion of a study that analysed rainfall trends between 1813 and 2006, and the results could have a significant impact on agricultural and economic planning and cropping patterns (or what is grown where, and when).
The study—which shows that there is a decreasing trend in rainfall received by at least two-thirds of India, and that the contribution of the monsoon months, June to September, to annual rainfall has been falling—could also explain why it has been raining more in certain states and less in others—changes that are usually attributed to erratic weather patterns.
PRECIPITATION PATTERNS (Graphic)
The study, conducted by scientists at the Pune-based Indian Institute of Tropical Meteorology, or IITM, used the widest ever data set of monsoon records and will, the people who worked on it claim, help farmers, policy planners and meteorologists better understand—and predict—rainfall trends in India.
That is critical in a country where agriculture accounts for almost one-fifth of the economy and provides employment to around 60% of a population of a little more than one billion. It is even more critical in a country where most agricultural land is “rain-fed”, a term that means that the primary source of irrigation is rainfall.
The study shows that except for the east coast regions of Tamil Nadu and Andhra Pradesh, south Gujarat, West Bengal and parts of Orissa, the country is showing a gradual decrease in rainfall levels and, while the overall annual decline, between the representative averages of 1944-1969 and 1970-2006, is only 4.1%, the shortfall is magnified at a microscopic level.
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India’s fluctuating rainfall pattern
For instance, in the plains of Kerala, peak rainfall declined from at least 3,700mm (received in the 1920s and 1930s) to around 2,800mm in the 1960s, a fall of 24%, which means significant changes in irrigation planning and cropping patterns.
In the plains of Punjab, there has been a similar fall—from 1,100mm in the early years of the 20th century to around 687mm now, a decrease of 37.5%.
“The decline began in the 1960s, but why (it happened) hasn’t been very well understood,” said Nityanand Singh, senior scientist at IITM and one of the people behind the study.
“Global warming may be a factor but, studies suggest, there’s actually a cooling in the upper atmosphere near the Tibetan plateau. The atmospheric ‘warming’ stops 3-4km above. And, this cooling affects something called the Tibetan anticyclone that’s closely linked to India’s monsoon systems. We still don’t understand a lot of this,” he added.
According to Singh, the most important reason why his team undertook the study was to make India’s understanding of the monsoon more contemporary, “beyond the 1900s”.