Pune has been experiencing an increase in torrential rains, which experts attribute to climate change, weak monsoons, and urbanization. Meteorologists have observed a rise in heavy rainfall events over short periods, particularly in rapidly urbanizing cities.
Climate Change and Urbanization
Dr. Medha Khole, head of Climate Research & Services in Pune, noted that both Maharashtra and the rest of the country have seen heavy rains during the pre-monsoon period, the northward movement of the monsoon, and the monsoon retreat. This rain often falls over very localized areas, sometimes within just a few kilometers. For instance, the Chinchwad area recently experienced such cloudburst-like rain. Dr. Khole explained that while overall monsoon rainfall is weak, high water vapor content in the air causes local warming, leading to the formation of clouds that result in sudden heavy rainfall. However, as monsoon activity increases, such incidents are expected to decrease.
Impact of Global Factors
Dr. Anupam Kashyapi, a retired scientist from the India Meteorological Department (IMD), pointed out that global climate change, deforestation, increasing urbanization, dense populations, and rising pollution have all contributed to the increase in cloudburst-like rain events. These events, often covering a radius of four to five kilometers, have become more frequent due to the lack of consistent monsoon rains.
Local Atmospheric Conditions
Rainfall in specific areas of a village or city is influenced by the convective action of the local atmosphere, shaped by the geographical structure and the sun’s heat. This heat causes the land to evaporate water, which rises and condenses into rain at higher altitudes. This convective action results in cloudburst or cloudburst-like rain. Manikrao Khule, a retired IMD scientist, explained that vapors from the sea often mix with local vapors, linking local heavy rains to both atmospheric and sea energy.
When Does Torrential Rain Occur?
Torrential rain events in Pune typically occur during the following periods:
- The pre-monsoon season from March to May.
- September and October, after the monsoon rains begin to retreat.
- During the arrival and immediate cessation of monsoon rains.
A cumulonimbus cloud is considered a cloudburst if it produces more than 100 mm of rain within one hour from clouds located one to two and a half kilometers above ground level.
Long-term Changes in Rainfall Patterns
Changes in rainfall patterns cannot be concluded immediately. According to Dr. Medha Khole, continuous observation over 30 to 40 years is required to confirm any changes in monsoon rainfall patterns. This long-term observation is crucial to understanding the characteristic changes in the Indian subcontinent’s monsoons.
