KOCHI: The city is basking in a pleasant warmth. The bright blue sky gives way to white clouds rolled up like cotton candy. However, like a petulant kid, it changes mood. The wind picks up and brings with it menacingly dark clouds — the harbinger of rain. In a snap, it starts to rain with familiar abandon.
But, it’s nothing like what we are used to — familiarity, it seems, does breed contempt. The storm clouds seem to dissolve into the heavens, as the downpour stops as soon as it starts. All in just half an hour. As the gloom fades, the curtain lifts on the sun and the sky turns blue.
Researchers have been noticing changes in rain patterns since 2018 — the year of the grand deluge in the state.
“Most of the clouds that appear in the skies have white wimpy forms, which, of course, at times, attract our attention. But only a few clouds produce rain, and they are called nimbus clouds” says Dr Vijaykumar P, assistant professor of environmental sciences at the University of Kerala. The nimbus clouds, he adds, can take different forms.
“Say around 40 years ago, we used to have mostly shallow nimbostratus clouds, which would have formed not more than 8km from the ground. During monsoons, the skies over Kerala were covered in these clouds, like a sheet. However, recent studies by the Cochin University of Science and Technology (Cusat) suggest an alarming trend of clouds taking shape vertically during monsoons. “These nimbus clouds have been forming at a height of 14km in recent years,” he added.
Such structural changes in cloud patterns produce more intense rain over shorter durations. This phenomenon will persist in Kerala, he says. “The recent cloudburst in Kalamassery was the result of such a cumulonimbus cloud that formed at unnatural heights.” And the reason, he explains, is the warming of the Arabian Sea.
Climate change has turned the waters of the Arabian Sea into the warmest. This results in taller cumulonimbus clouds, those that cause strong thunderstorms. “Kerala usually sees such clouds form ahead of pre-monsoon showers during the summer. Such clouds also form post monsoon, but usually with a lower height. The difference is that these clouds used to be very rare during monsoon time in the state. Now, we may witness more frequent mini or major cloudburst events along the western seaboard, especially Kerala,” he points out.