Panaji
Heavy rain is falling across every part of Goa, causing multiple problems such as fallen trees, road accidents, route diversions due to landslides, collapsing houses and structures, and power outages. People are asking: if this is just the prelude, what will the full monsoon bring?
Addressing these fears, Dr Ramesh Kumar says, “The pre-monsoon season (March to May) showers are an important part of Goa’s annual rainfall. This season contributes about 3.6% of the mean annual rainfall. The monsoon season (June to September) provides about 91%, while the post-monsoon season (October to December) adds around 5.4%. The winter months (January and February) contribute very little.”
“This year we had an unusually large amount of pre-monsoon rain, thanks to a convective system near the west coast of India in the southeastern Arabian Sea, which caused about 983.4% excess rainfall during this season,” he adds. “The average rainfall for this season is 40.2 mm, but until 8:30 am on June 24, Goa had already received 436.1 mm. This is a record that may not be broken soon.”
Each monsoon and pre-monsoon season is unique, explains Dr Ramesh Kumar. “It depends on synoptic conditions over the land and surrounding seas like the Arabian Sea, Bay of Bengal, and the south Indian Ocean. Large-scale ocean-atmosphere phenomena such as El Niño/La Niña in the Pacific Ocean, and the Indian Ocean Dipole also influence rainfall during the pre-monsoon, monsoon, and post-monsoon seasons over India.”
The melting of glaciers and ice shelves in Antarctica plays a role too. It lowers sea water salinity in those regions and slows down the Ocean Conveyor Belt, which affects weather and climate globally. “It depends on the region we are talking about,” says Dr Ramesh Kumar, who visited Antarctica in 1986-87 to study how the ice cover affects the Indian monsoon, including the onset over Kerala, active and break spells during the monsoon, and rainfall across 36 meteorological regions, influenced by the Mascarene High pressure.
All 13 rain gauge stations in Goa have recorded over 250 mm of rainfall during this pre-monsoon season. Dharbandora received the highest at 539 mm, followed by Margao with 537.9 mm, and Dabolim with 516.3 mm. The lowest was Valpoi, with 255.1 mm.
Antarctica voyage to study the Indian monsoon
Dr Ramesh Kumar was part of the 6th Indian Scientific Expedition to Antarctica, studying weather and climate there. The summer team leaves Goa in November, reaches Antarctica in about a month, celebrates Christmas there, and returns in March.
“I studied how air-sea fluxes change from tropical to polar regions and published my work in top scientific journals like Boundary Layer Meteorology and Continental Shelf Research. Both papers were well received worldwide,” he adds.
When we talk about the monsoon (Southwest Monsoon), it mainly involves the seasonal reversal of winds to the south-westerly direction. But most people think of monsoon only as rainfall. Three key conditions define the monsoon onset: a) widespread rainfall over most regions, b) winds from the surface up to about 4.2 km (600 hPa) should be westerly with a speed of at least 6 m/s, and c) outgoing longwave radiation (OLR) should be below 200 W/sq m, indicating strong convection.
“These conditions will meet first in Kerala by today noon,” Dr Ramesh Kumar explains, “and Kerala is the gateway for the monsoon over India. The monsoon will reach Goa depending on surrounding synoptic conditions. For convenience, we consider March 1 to May 31 as the pre-monsoon season, and June 1 to September 30 as the monsoon season.”
This is according to the India Meteorological Department (IMD), he points out. As an outreach effort, Dr Ramesh Kumar has given over 500 talks on monsoon, cyclones, climate change, oceanography, remote sensing, and careers in oceanography. He has shared Antarctic rocks, penguin feathers, and science books in schools and colleges across India to inspire students to pursue science careers.
