Pakistan is experiencing a record monsoon season. Here’s why


Record rainfall this summer has pushed Pakistan into its worst floods in at least a decade. The flood waters turned the lowlands around the Indus into swamps. At least a million homes have suffered some level of damage, and about 5,500 roads, bridges and shops have been damaged since mid-June. More than 1,160 people were killed and 3,500 injured from June to August.

The government estimates that about 33 million people, or 13 percent of the population, have been affected by the floods.

Most of the heavy rainfall is associated with the summer monsoon pattern over the region. The term ‘monsoon’ describes the shift of the monsoon winds that bring moist air to southern Asia during the summer, resulting in heavy rainfall. The summer monsoon provides 65 to 75 percent of the annual water in Pakistan, and plays an important role in agriculture and the livelihoods of the population.

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But exceptional rainfall rates have made this season a ‘monsoon on steroids’, He said António Guterres, Secretary-General of the United Nations.

From June to August, Pakistan received 190 percent of the usual rainfall. July alone exceeded the normal monsoon total by about 26 percent, becoming the wettest July on record since 1961. Heavy rainfall saturated the soil, preventing the land from absorbing more water from August storms. Rainfall during the monsoon season reaches its peak in August, which has continued to bring significant rainfall and flooding.

Unusually heaviest rains fell in Balochistan and Sindh provinces, which suffered extensive damage. Rainfall amounts from mid-June through August were 430 percent of normal in Balochistan and 460 percent of normal in the bond. About 50 different cities experienced much higher than normal monthly rainfall.

“The season is not over yet, and the total number of rainy days has already doubled in several cities,” said Bushra Khaled, a researcher at the Institute of Geographical Sciences and Natural Resources Research. He told the newspaper in a letter.

The monsoon regime begins as the air temperature rises over the elevated terrain in Tibet during the summer, creating a broad belt of low pressure known as the hypothermic. Thermal depression draws moist airflow from the Arabian Sea and the Bay of Bengal.

The monsoon usually takes time to travel north to Pakistan in the summer. This year, the Pakistan Meteorological Department said the season settled in the country on June 30, a day before the usual start.

Muhammad Fahim Khokhar, a researcher at the National University of Science and Technology in Islamabad, explains that the summer monsoon enters Pakistan in two different directions. First, the southwesterly winds coming from the Bay of Bengal travel along the foothills of the Himalayas and enter Pakistan. The system brings the first monsoon rains to the districts of Sialkot, Jhelum, Islamabad and Lahore, which form the northern monsoon belt and are the main area of ​​monsoon activity.

The second path comes from the southwesterly winds entering Pakistan from the Arabian Sea, causing rainfall in the southeastern region of Pakistan. Khokhar said Balochistan usually remains largely unaffected by the summer monsoon but has received heavy rains this year.

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“The seasonal low pressure regime over South Asia is larger than ever, it cuts through western Pakistan as far as Iran and brings rainfall to Balochistan province as well,” Khalid said. She said the monsoon basin, which determines the distribution of rainfall over Pakistan, is further south than usual, resulting in more rainfall in southern Pakistan, including Sindh and Punjab.

The researchers also say that the extraordinary precipitation is caused in part by the presence of La Niña, which features cooler surface waters in the equatorial Pacific. Cooler water temperatures are pushing an air current known as the Walker circulation to speed up through the Pacific Ocean and boosting monsoon rains in South Asia.

2022 is the third year in a row with La Niña, a rare achievement. But Khaled said this year has seen “a more severe La Niña phenomenon, bringing with it severe and destructive monsoon winds”.

La Niña was also present during the last disastrous monsoon season in 2010, which claimed more than 2,000 lives and is considered the worst season on record. Preliminary numbers suggest that this year’s monsoon season could be even worse.

Waheedullah, assistant professor at Nanjing University of Information Science and Technology, said the floods may also be linked to heat waves in Europe.

He said the atmospheric blocking pattern that caused heat waves in Europe also tends to favor above-normal rainfall in Pakistan, bringing significant moisture to the region across the Indian Ocean and Bay of Bengal. He and his colleagues have a “firm belief” that a similar moisture transfer could occur this time as well.

Allah said, “In past situations like 2003 and 2010, there were devastating floods in Pakistan when Europe suffered from heat waves.”

Living in a climate torn world

Researchers say climate change has also played a role in this year’s monsoon season.

Khokhar said temperatures above Pakistan’s monsoon belt have increased at a rate of about 0.18 degrees each year since 2010. Warmer air can contain more moisture, which can lead to heavy rains and subsequent floods.

Khokhar and his companions found previously The number of rainy days during the monsoon season has decreased in recent decades, but he said climate change could lead to increased rainfall intensity and flash flood risks in Pakistan.

Similarly, Allah and colleagues found that the duration of wet events in the country decreased, but the number and frequency of extreme events, especially after 2011, increased.

Allah said: “The monsoons and the extreme conditions associated with them over Pakistan in particular and in the area of ​​the monsoons in South Asia, in general, are increasing significantly.”

Higher-than-average sea surface temperatures over the Indian Ocean also intensified the season. Warmer sea surface temperatures prompted more evaporation, allowing more moisture to be transported over the area and fall as rain. Khokhar said that tropical depressions systems in the Bay of Bengal and the Arabian Sea could play an important role along with rising sea surface temperatures.

The summer rains come after record heat hit Pakistan in the spring, which the researchers calculated was 30 times more likely Occur due to climate change. Record heat helped melt glaciers, and some Flash floods in nearby villages. Additional glacier melt throughout the summer has increased seasonal flooding.

Pakistan is consistently listed as one of the countries most vulnerable to climate change by the Intergovernmental Panel on Climate Change, despite contributing less than 1 percent of recent global greenhouse gas emissions.

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Part of the reason is due to the diversity of its ecosystems, including glaciers, rain-dependent rivers, melting glaciers, deserts, and mangroves in the south. Khokhar said that a large number of Pakistan’s population with poor socio-economic conditions depend on these natural systems for their livelihood.

“Pakistan is more vulnerable to minor climate disturbances due to its sensitive ecosystems,” Khokhar said. “It is certain that Pakistan should redesign its development plan which focuses on integrating all types of natural disasters, and resiliency and sustainability of society.”

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