GS 1 – GEOGRAPHY
Context:
Cloudbursts are sudden, intense rainfall events that can cause flash floods, landslides, and severe local damage, especially in Himalayan and mountainous regions.
Definitions:
- India Meteorological Department (IMD): Rainfall exceeding 100 mm in one hour over ~20–30 sq. km area.
- World Meteorological Organisation (WMO): Rainfall ≥ 100 mm/hour; also refers to ‘skyfall’ (Swedish term) defined as 1 mm per minute (60 mm/hour) for short bursts or 50 mm/hour if prolonged.
- Process-based View: Focuses on mechanisms rather than fixed rainfall figures.
Scientific Mechanisms:
- Thunderstorm Updrafts: Strong upward winds suspend large volumes of water high in the atmosphere; collapse of updraft releases this water suddenly as a torrential downpour.
- Orographic Lifting: Moist air forced upwards by mountain ranges leads to rapid cooling, condensation, and concentrated rainfall.
Key Features:
- Highly Localised: Affects a small area but can trigger widespread flooding downstream.
- Short Duration, High Intensity: Distinct from steady monsoon rains.
- High Destructive Potential: Triggers flash floods, erosion, damage to infrastructure and agriculture.