Cloudburst
SyllabusDisaster and disaster management
The India Meteorological Department defines a cloudburst as rainfall of 100 mm or more within one hour at a station. It is therefore an exceptionally intense, short-duration and highly localized rainfall event, rather than the physical bursting of a cloud.
Understanding the criterion
The defining variable is rainfall intensity, measured over a one-hour interval. A large daily rainfall total is not necessarily a cloudburst unless the hourly threshold is satisfied.
- The criterion is based on rainfall recorded at a station, not merely on reports of sudden heavy rain.
- Because the event is spatially concentrated, a nearby rain gauge may record much less rainfall or miss it entirely.
Disaster significance
Such concentrated precipitation can rapidly overwhelm local drainage and increase surface runoff. In steep terrain, it may trigger flash floods, debris flows and landslides with little response time.
- Precise prediction is difficult because cloudbursts develop over small areas and short time spans.
- Cloudbursts may occur beyond mountains, although terrain-induced uplift can favour intense rainfall in hilly regions.
How UPSC asks this
Remember the IMD threshold and distinguish hourly rainfall intensity from daily rainfall totals.
Explain how the localized nature of cloudbursts creates forecasting challenges and can trigger flash floods and landslides.
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