Cloudburst | UPSC

Recent news from Himachal Pradesh highlights the occurrence of a cloudburst, drawing attention to this meteorological phenomenon that can have significant impacts in various regions.

Contents

Defining a Cloudburst: Beyond Ordinary Rainfall

A cloudburst is characterized by a sudden and intense bout of localized rainfall. It’s essential to note that not all instances of heavy rainfall qualify as cloudbursts. The criteria for classifying a rain event as a cloudburst include:

Rainfall of 10 cm or more within a single hour.
Coverage across an area of at least 10 km x 10 km.
In some cases, even 5 cm of rain within 30 minutes can be categorized as a cloudburst.

Contextualizing Cloudbursts in India’s Rainfall Patterns

In the context of Indian rainfall, which averages around 116 cm across the country in a normal year, cloudbursts stand out due to their intensity and localized nature. To put this in perspective, if the annual average rainfall were evenly spread, it would accumulate to a height of 116 cm. However, geographical variations lead to some areas receiving rainfall that’s as much as 10 times the annual average, underscoring the diversity of India’s precipitation patterns.

The Significance of Cloudbursts: A Sudden Onslaught of Rain

The impact of a cloudburst is substantial, with about 10% of the annual rainfall occurring within just one hour during these events. To draw a comparison, the infamous Mumbai cloudburst of July 26, 2005, witnessed an extreme instance of rainfall with 94 cm of rain in 24 hours. This resulted in over 400 fatalities and economic losses exceeding USD 1 billion.

Locations Prone to Cloudbursts: A Focus on Hilly Regions

Cloudbursts tend to occur in hilly regions and states along the Himalayas due to a combination of factors. Local topology, wind systems, and temperature gradients between the lower and upper atmosphere contribute to the conditions that can trigger these intense rain events.

When Cloudbursts Strike: The Frequency and Timing

While not uncommon, cloudbursts are especially prevalent during the monsoon months. These intense bursts of rainfall can disrupt normal life, cause flash floods, and trigger landslides in hilly terrain.