Explained: Why showers might become more frequent


Written by Aswathi Pasha, edited by Explained Desk | Cochin |

Updated: Aug 4, 2021 12:24:31 pm

On July 28, at least seven people were killed, 17 injured and more than 35 missing after a downpour hit a remote village of Jammu and Kashmir. Recently, showers were reported in several places in J&K, Union Territory of Ladakh, Uttarakhand and Himachal Pradesh. A 2017 study of downpours in the Indian Himalayas noted that most of the events occurred during the months of July and August.

What is a downpour?

Showers are intense, short-lived rainy events over a small area. According to the Indian Meteorological Department (IMD), this is a meteorological phenomenon with unexpected precipitation exceeding 100 mm / h over a geographical area of ​​approximately 20 to 30 km².

A study published last year investigated the meteorological factors that caused the waterspout over the Kedarnath region. They analyzed atmospheric pressure, atmospheric temperature, precipitation, cloud water content, cloud fraction, cloud particle radius, cloud mixing ratio, total cloud cover, wind speed, wind direction and relative humidity during rain, before and after rain. The results showed that during the waterspout, relative humidity and cloud cover were at the maximum level with low temperatures and slow winds. “It is expected that due to this situation a large amount of cloud will condense at a very rapid rate and result in a downpour,” the team wrote.

Will we see more such showers?

Several studies have shown that climate change will increase the frequency and intensity of downpours in many cities around the world. In May, the World Meteorological Organization noted that there is about a 40% chance that the annual average global temperature will temporarily rise to 1.5 ° C above the pre-industrial level in at least one of the next five years. . He added that there is a 90% chance that at least a year between 2021 and 2025 will become the hottest on record and dislodge 2016 from the top spot.

“As temperatures rise, the atmosphere can hold more and more humidity and that humidity decreases in the form of a short, very intense rain for a short period of time, probably half an hour or an hour, resulting in flash floods in mountainous areas and urban flooding in cities. In addition, there is evidence to suggest that extreme short-term precipitation globally will become more intense and more frequent. With global warming or climate change, we will surely see these downpouring events with increased frequency in the future, ”says Vimal Mishra of Civil Engineering and Earth Sciences at IIT Gandhinagar.

Can we predict showers?

“It is an extremely difficult task and it is very difficult to model a downpour,” says Subimal Ghosh of the IIT Bombay Civil Engineering Department. His team studied the Indian monsoon and hydro-climatic extremes.

He adds that the models don’t really work at this resolution and explains in detail with the example of a popcorn. “Imagine you are making popcorn. The pot heats up and the corn pops. If I ask you which corn will pop first, you may not be able to answer. You need very fine resolution studies to decode. Also, if I ask you how much corn will pop after two minutes, you could say 99%. But what about how much after 10 seconds? The answer is difficult for a finer resolution and a finer timescale. Likewise, for hourly precipitation and downpours, it is very difficult to simulate the intensity and location.

About Marco C. Nichols

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