Monsoon Breaks

A new study published in the Journal of Climate sheds light on the causes of “break periods” in the South West Monsoon (SWM), which provides over 75% of India’s annual rainfall between June and September.

What Are Monsoon Breaks?

Break periods are phases during the SWM when rainfall sharply decreases across most of India while precipitation increases along the Himalayan foothills and Northeast.

These breaks typically last from a few days to a couple of weeks and can significantly impact agriculture, water supply and hydropower generation.

Causes Identified by Study

The study notes that break periods are caused by dry winds flowing from western and northwestern India. These winds shift the main monsoon trough northward toward the Himalayan foothills, reducing rainfall over central India.

Researchers say these dry spells can potentially be predicted in advance, improving early warning systems for drought-like conditions during the monsoon season.

Role of Monsoon Trough and ITCZ

The Monsoon Trough is an elongated low-pressure area extending from Pakistan’s heat low to the Head Bay of Bengal and is a semi-permanent feature of monsoon circulation.

During break periods, this trough shifts northward.

The Inter Tropical Convergence Zone (ITCZ), a low-pressure belt near the equator where trade winds converge, also plays a role. In July, it shifts to around 20°N–25°N over the Gangetic plains, sometimes referred to as the monsoon trough.