Scientist warns warming Arabian Sea makes Kerala landslide prone

Soil has already become saturated from prolonged rainfall

KOCHI: A senior climate scientist has indicated that the warming of the Arabian Sea is facilitating the formation of deep cloud systems, which are causing extremely heavy rainfall in Kerala over short periods and heightening the risk of landslides.

The intense rainfall triggered a series of landslides in the hilly areas of Kerala’s Wayanad district early on Tuesday, resulting in at least 162 deaths and 128 injuries. Many people are feared to be trapped under the debris.

S. Abhilash, Director of the Advanced Centre for Atmospheric Radar Research at Cochin University of Science and Technology (CUSAT), explained that districts including Kasargod, Kannur, Wayanad, Calicut, and Malappuram have experienced heavy rainfall due to an active monsoon offshore trough affecting the Konkan region for the past two weeks.

The soil had already become saturated from the prolonged rainfall. On Monday, a deep mesoscale cloud system developed off the Arabian Sea coast, leading to extremely heavy rain in Wayanad, Kozhikode, Malappuram, and Kannur, which in turn caused localized landslides, Abhilash said.

Cloud systems are very deep

He noted that the cloud systems were very deep, comparable to those seen during the 2019 Kerala floods.

Abhilash pointed out that scientists have observed a trend of increasingly deep cloud systems forming over the southeast Arabian Sea. These systems occasionally move inland, as seen in 2019. “Our research indicates that the warming of the southeast Arabian Sea is making the atmosphere above this region, including Kerala, thermodynamically unstable,” he said.

This instability, which fosters the development of deep clouds, is linked to climate change. Previously, such intense rainfall was more common in the northern Konkan belt, north of Mangalore. However, with climate change, this rain-bearing zone with deep clouds is shifting southward, which is contributing to extreme rainfall events.

Abhilash and other scientists published research in the Climate and Atmospheric Science journal in 2022, showing that rainfall over the west coast of India is becoming more convective. Another study by Abhilash and researchers from IITM and IMD, published in Elsevier in 2021, found that one of the hotspots for heavy rainfall in the Konkan region seems to be moving southward, potentially leading to severe consequences.

The study also suggested that increased rainfall intensity may heighten the risk of landslides in the high to mid-land slopes of the Western Ghats in eastern Kerala during monsoon seasons.

Weather stations report rainfall exceeds 24 cm

According to the India Meteorological Department, automatic weather stations in Thrissur, Palakkad, Kozhikode, Wayanad, Kannur, Malappuram, and Ernakulam recorded rainfall between 19 cm and 35 cm. “Most IMD weather stations in the region reported rainfall exceeding 24 cm within 24 hours, with some farmer-installed stations recording over 30 cm,” Abhilash noted.

The Met Office has forecasted that very heavy rainfall could continue in some parts of the state over the next two days. Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology, cautioned that it is too early to fully understand the specifics of the Kerala landslides. He added that monsoon patterns have become more erratic, with increasing instances of landslides and floods along the Western Ghats from Kerala to Maharashtra.