Drizzle or downpour? They have the answer: The people who predict the monsoon
The drama unfolds as the first rain-bearing clouds gather over the ocean in Kerala, marking the annual arrival of the monsoon to the Indian mainland. When the first drops descend, you know the nation is watching.
The meteorological (Met) office in Thiruvananthapuram is used to the attention. Set up in 1836 as the Trivandrum Observatory by the then king of Travancore, Swathi Thirunal, it was redesigned the following year by British weather expert John Caldecott,who added the astronomical and meteorological sections. The meteorological division was taken over by the Government of India and upgraded to a meteorological centre in 1973.
“Each monsoon is unique and its onset features different,” says K Santhosh, director of the Met centre. “We have to monitor 14 stations, including two in Lakshadweep. If 60 per cent of these stations get 2.5 mm or more of rain for two consecutive days, the monsoon has arrived.” Other indicators include westerlies (winds blowing from west to east), cloud build-up and, of course, satellite images, which give you the most aerial view possible of how the monsoon is progressing.
From Kerala, the monsoon spreads to other parts of the country. It might gather force on its journey, or lose steam, depending on local, national and global changes in weather patterns, bringing a deluge in some parts, and a rain deficiency in others.
Every day around 5.30am and at the same hour every evening the meteorological observatory at Delhi’s Aya Nagar releases a big hydrogen-filled balloon to which is attached a sensor payload that samples temperature, pressure, wind speed and direction, and moisture with exact GPS location at several levels in the atmosphere. It is one of 43 locations across India where such simultaneous observations are made twice daily. The upper air measurements of data collected is then collected instantaneously at the telecommunications hub in India Meteorological Department (IMD) HQs for pushing to global weather forecasting centers and also to the Indian Global Data Assimilation and Forecasting System (GDAFS) to generate most representative forecasts, explains KJ Ramesh, director general (meteorology), IMD.
For weathermen, the Indian monsoon, is the most challenging aspect of all weather conditions, says Ramesh. But as Alexander Frater wrote in Chasing The Monsoon, “Predicting the burst is not just a matter of dry figures and charts. As it approaches, you begin to feel elated, even slightly intoxicated...”
The setting up of the first met observatory in India by the British in Calcutta in 1785, was also, largely propelled by the need to study the monsoon rainfall variability along with its seasonal quantum, he says. In 1636, Hailey, a British scientist had published his treatise on the Indian monsoon, which he attributed to a seasonal reversal of winds due to the differential heating of the Asian land mass and the Indian Ocean as the primary seasonal feature for the evolution of the summer monsoon circulation. “The British cotton mills in Manchester were dependent on raw materials from India based on the good rainfall season for Indian agriculture. A deficit monsoon meant failure of good cotton crop yields and production deficit in England. Therefore it was important for them to study the season,” explains Ramesh.
Over the years, the observing system technology used for weather forecasting has advanced from simple thermometers, barometers and rain gauges, to include radars and satellite imagery.
The accuracy of predictions have also improved. “We can now predict weather changes over shorter time periods and across a radius of 12 sq km (10-days in advance),” says Ramesh. He adds: “Severe weather conditions can be predicted three days in advance for a finescale of nine square km, across India.”
Nor is the Met office our only point of reference for weather-related information anymore. From Accuweather to Google, we now have forecasts of rain and sunshine available on our smart devices. Skymet, a private weather services company, has been working with many state governments. since it was founded in 2003. “We get it more right than wrong. Except when we missed a drought in 2015, our forecasts have always been accurate,” says Jatin Singh, founder, Skymet.
It is a track record to be proud of. As Frater wrote, in India “a failed monsoon could mean riots and lost elections”. And in families of farmers, the ache of bereavement, as lives are lost under the burden of economic doom.