‘Rivers in the sky’ are becoming more intense in India, can be linked with devastating floods, heat stress

Sub : Geo

Sec: Climatology

Context:

The Wayanad landslide, claiming over 300 lives, highlights the urgent need to address climate change.
Experts link the disaster to intensifying monsoon rains and land-use changes from forests to plantations.

Increasing Monsoon Intensity:

The subcontinent is experiencing more intense humid heat in summers and heavy rainfall during monsoons.
Monsoon months from July to September have become wetter with erratic precipitation patterns due to global warming.
The number of stations recording ‘very heavy’ and ‘extremely heavy rainfall’ has more than doubled in the last five years.

Atmospheric Rivers (AR) and Rainfall Intensity:

Atmospheric rivers (AR), streams of water vapour from warming oceans, contribute to increased rainfall and humid heat.
- ARs are identified and measured using a metric called Vertical integrated vapour transport (IVT).
- Scientists going through satellite or model data “look for corridors that are greater than 2,000 kilometres long and less than 1,000 km wide that have at least 2 centimetres of vertically integrated precipitable water”.
ARs are associated with heat-then-flood events, as evidenced in the US and a seminal study in India.
70% of major floods in India over the past 35 years were linked to ARs, with 65% of ARs causing floods.

Impact of Atmospheric Rivers:

ARs carry large volumes of moisture and flow faster than major rivers, significantly altering local climates.
These events increase wind speeds and cause violent showers, especially during summer-monsoon months.
AR events are expected to rise, leading to more landslides and flash floods.

Historical and Current Trends

From 1950-2020, 596 major AR events occurred in India, mostly between June-September.
The frequency and severity of ARs have increased, particularly in peninsular India and the Indo-Gangetic plain.

Source: DTE