The number of rainy days is decreasing while intense rainfall events are increasing globally
A rainy day in Mumbai. Photo: Nidhi Jamwal If Donald Trump were to deny climate change again, he can be shown proof: The deluge in Mumbai, India’s biggest city, mid-2019.
Torrential rains starting June 28 in the past five days have brought Mumbai to a grinding halt. Until 8:30 am on July 2, Mumbai’s Colaba station received 137.8 mm rainfall.
This, when the whole of Mumbai received 433.7 mm rainfall from June 1 to July 1. That means the city got almost one-third of its monthly rain in these 8.5 hours. The previous day, there was 92.6 mm rainfall in the city, which brings the total to 230.4 mm in less than one and a half day. More than 50 per cent of the month’s rainfall fell on Mumbai in this time.
And this is not the story of Mumbai alone. Palghar received 212 mm of absolute rainfall on July 1, which is 593 per cent of the normal rainfall the district receives for that day.
The districts of Raigad, Suburban Mumbai and Thane have also received more than 90 mm of rainfall. Only this small region of Western Maharashtra has received such heavy rainfall. In other regions of the state, there are a few districts with big spikes in rainfall but the rest have remained dry.
From June 20 to June 26, Mumbai had received only 8.4 mm rainfall, a deficit of 95 per cent. At the time, the seasonal deficit for the city stood at 70 per cent. And then, this week brought so much rain that the city got flooded.
A similar situation had occurred in 2018 and this seems to have become a pattern. First, there is a deficit in rainfall for an extended period and when the rains do arrive, they are so intense that they cause floods, landslides and flash floods.
Before the once-in-a-century devastating floods in Kerala which had killed more than 500 people, the state had experienced a very dormant monsoon. Once the rains began, they did not stop for almost two weeks.
This has been a worrying trend for the past few years. Back in 2016, Madhya Pradesh and Rajasthan were in a drought-like situation when floods occurred in July-August, while Bihar and Assam — two states that are facing their worst floods in almost three decades, had deficit rainfall that monsoon.
Global rainfall data for over the last century shows an alarming trend. The number of rainy days is decreasing while intense rainfall events of 10-15 cm/day are increasing. This means that more amount of water is pouring down in lesser time. For example, globally, 50 per cent of annual precipitation (rain, snow and ice) is received in just 11 days.
A study published in the journal Nature Communications in October 2017 had predicted that widespread extreme rain events over Central India have increased three-fold in the 66-year period between 1950 and 2015.
The study notes a 10-30 per cent increase in rainfall events over the region where more than 150 mm of rain is registered in a day has been occurring despite a general weakening of monsoon circulation.
Another study conducted by the Indian Institute of Technology, Gandhinagar, had predicted an increase in extreme rainfall events in Southern and Central India and had linked it to global warming due to climate change.
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