New Delhi: A month after rains lashed parts of India’s Northeast and Bangladesh, monsoon’s fury is now being felt in parts of Pakistan, where excessive rainfall has led to flooding in areas in Karachi and Balochistan. Peninsular and central India, meanwhile, are reeling under drought-like conditions and a deficit of rain.
Pakistan’s Met department predicted that heavy rainfall and urban flooding would continue across Sindh and Balochistan for the next two days, and that the rains would finally abate by 21 July.
An intense low pressure area “over Northeast Arabian Sea & adjoining Gulf of Kutch has slowly moved northwestward with a speed of 5 km/hr during the last 18 hours,” it said in its daily weather report Sunday, adding that the rest of the month may see “slightly above normal precipitation”.
According to reports, over 160 people have been killed in flash floods caused by torrential rains in Pakistan in July.
Back home in India, the western coast and northwest regions are seeing excess rainfall, according to the Indian Meteorological Department (IMD), while southern, northern, and central regions are experiencing a deficit.
The IMD, in its two week forecast released on 14 July, described rainfall activity over Gujarat as “this monsoon season’s most extremely heavy rainfall spell, if we consider all spells, so far in the plains, in this season till today”.
“States like Uttar Pradesh and Bihar in northern plains also received deficient rainfall due to monsoon trough at south of the normal position and absence of any system forming or moving over to the region,” it added.
Even the Northeast is experiencing drought-like conditions — which the IMD predicts will correct itself after 21 July.
Monsoon in India covered the full subcontinent on 2 July. Even though it was classified as “normal”, wide variations were reported from different regions across the country.
Rainfall and flooding in Bangladesh, meanwhile, seems to have subsided compared to last month, when a deluge killed at least 42.
What explains these differing weather patterns across South Asia? Experts say it’s a combination of internal variability (the natural climatic changes that occur in weather systems), an unusually long La Niña period, and the effect of climate change.
Also Read: La Niña, climate change — why Indian subcontinent got scorched so early & for so long this year
La Niña, climate change
The meteorological departments in India, Pakistan, and Bangladesh acknowledge the presence of a La Niña – which is predicted to enter its third year in 2023 – and its effect on monsoon patterns.
La Niña is a global weather phenomenon that causes the surface ocean waters along the tropical west coast of South America to cool. La Niña causes lower air pressure over the western pacific, which generally causes higher rainfall.
“We had a La Niña over the 2021-22 winter and that usually causes a rainfall deficit during the monsoon. Since the La Niña is continuing, the June deficits are almost gone and the La Niña could also affect the monsoon withdrawal and we could see heavy rainfall late in the season too,” said Raghu Murtugudde, a professor with the department of atmospheric and oceanic science in the University of Maryland.
According to Murtugudde, the southwesterly winds that cross the Arabian Sea have shifted northwards, causing a downpour across Gujarat and Pakistan and also the Northeast, while leaving Kerala and peninsular regions dryer.
J.R. Kulkarni, a retired scientist from the Indian Institute of Technology, Madras, said such monsoon weather patterns are not unusual across South Asia, and that the deluge in Pakistan will be short-lived.
“Moisture from the Bay of Bengal and the Arabian Sea has gone over Pakistan. From the Arabian Sea, the moisture went over northwest India, became energised because of higher temperatures, and travelled to the Pakistan area where clouds developed,” he said, adding that the heavy rainfall would subside within a week.
While extreme weather events from time to time are normal, the onset of climate change is causing their frequency to increase. In India and South Asia, this means higher and more intense spells of rain, according to the Intergovernmental Panel on Climate Change (IPCC).
“Generally, with global warming, warm air will hold more moisture for a longer time. So, there are spells when it doesn’t rain for a long time, but when it does, it dumps all that moisture within a few hours or days, causing extreme rainfall,” Roxy Koll, a scientist with the Centre for Climate Change Research at the Indian Institute of Tropical Meteorology (IITM) in Pune, had told ThePrint last month.
(Edited by Amrtansh Arora)
Also Read: 2021 monsoon shows impact of climate change. Here’s what it’s doing to kharif crops