Causes of the 2022’s super flood in Pakistan

Unprecedented. Relentless and Catastrophic climatic events have made Pakistan ground zero!

And here we are again…just few months back we were blogging about the persistency & longevity of the heat wave. The month of March and April are the warmest since 1961 in Pakistan, May and June followed relatively a similar trajectory leading to an outbreak of ‘never-seen-before’ widlfires.

When the unprecedented heatwave of 2022 entered its 3^rd month, we expressed our fear regarding the potential deadly impact the heat could have on the monsoon season.

Recalling the horrors of 2010’s flood which preceded a much harsher heatwave. However, that uneasy feeling was quickly suppressed with the realization that ‘’monsoon booster” La-Nina which had earlier entered its third year would subside during the mid of the monsoon season or continue in a weak phase and the development of anti-monsoon phenomena known as the negative Indian Ocean Dipole (-IOD) was a sign of relief. As per scholarly research, -IOD is associated with scarce rains in the region.

Unfortunately, what unfolded is beyond what anyone can comprehend! It is apparent that the -IOD had no impact on the monsoon. This observation is itself astonishing & challenges the decade-old findings that it causes a decreasing rain trend.

33 million people have been affected by floods in Pakistan, which is more than the population of most European countries. The scale of flooding is far greater in the Sindh province than it was in 2010 as apparent from NASA’s satellite picture. Worth-mentioning, 2022 flooding is after the record-breaking rains, while the 2010 floods originated from the northern province of Khyber Pakhtunkhwa and reached Sindh towards the Arabian Sea.

Abnormal downpours have created a 100 km inland lake in Sindh as well.

Pakistan floods were imminent after the unprecedented heat wave

10 to 15 years of annual rain has fallen in just 2 to 3 months in most parts of Sindh & Balochistan, it is an out-of-an-ordinary event. Padidan, a town in Sindh province, with just 100 mm yearly rain has officially recorded 1,539.5 mm in just 2 months (July and August), the majority of it was recorded during the week starting from 15^th August till 23^rd August

Making 2022’s monsoon rains the wettest in the history of Sindh since data collection began in 1930s surpassing 2011’s abnormal rains.  

Official highest recorded rain in Sindh;

• 2022: Padidan recorded 1539.5 mm in 2 months.
• 2011: Mithi recorded 1,290 mm in 2 months.
• 2022: Karachi recorded 600 mm in 31 days of July
• 2012: Jacobabad recorded 441 mm in 36 hours in September
• 2022: Jamshoro recorded 335 mm rain in 24 hours in August

The city of Karachi has broken its all-time high monthly rain in just 2 years

The provincial capital was not spared either. Having just broken its all-time high rain figure in August 2020, the month of July 2022 set a new record. It rained more in July 2022 alone than in any previous year since 1930s.

• 588.0 mm – Faisal Base (Official stat by GOP – Aug 2020)
• 600 mm – PAF Masroor (Official stat by GOP – July 2022)

The average monthly rain is only 60 mm to 80 mm in July however highest official recorded was 600 mm (PAF Base), unofficially it may have reached 800 to 1,000 mm, especially in southern areas. As per Government of Pakistan’s official statement, Karachi’s July 2022 was the wettest month across Pakistan.

Bear in mind that Karachi gets only 175 to 200 mm rain per year.  It is very rare for the city to get a 200 mm rain in 24 hours. In July 2022, it got it twice in just two weeks! On July 10^th, it recorded 200+ mm (unofficially it reached 295 mm) in just 24 hours while another 204 mm on July 25 (official stat). Though, the official highest 24-hour record still stands at 235 mm on 27^th August, 2020.

Causes behind the heat and flood in Sindh

Interestingly, the year 2021 also had a striking resemblance to 2022 in terms of the atmospheric conditions that is lingering La-Nina and a developing negative Indian Ocean Dipole yet the heat and rains largely remained normal. This is what makes 2022’s weather pattern unexplainable! 

’Sweltering’ heat wave has occurred in a supposedly cooler year of La-Nina which makes it rare. The only likely explanation behind this is the formation of a ‘stubborn’ low pressure over southern Pakistan from March till early June that led to an unusually long heat wave. This created a vacuum of heavily warm air which condensed rapidly due to the moist air from the Arabian Sea and the cool outflow generated by the westerlies and easterlies.  The persistent heat sped up the melting of glaciers in the northern province of Khyber Pakhtunkhwa.

Much of the devastating rain occurred during the week of 15th August till 23rd  August in Sindh province. A strong low pressure had stalled over upper Sindh for 5 days. It originated as a tropical depression in the Bay of Bengal. Despite dry air from the west & strong westerly wind shear from the northwest, it re-intensified over land as pressure dropped from 998 to 995 mbar. The strengthening can be associated due to the SW wind flow from coastal Sindh as well as the moisture from flooded areas of Balochistan which is known as the ‘Brown Ocean effect’. Tropical Storm ‘Julia’ intensified over land in 2016 due to the same effect near the coast of Georgia, United States.

While the slow movement can also be attributed to the formation of cyclone ‘4B’ in the Bay of Bengal whose remnants were also moving towards Sindh. Being a much stronger system than the predecessor low, it led to a ‘Fujiwhara effect’ as on the 5^th day, the ‘stagnant’ low moved towards the approaching remnants of the cyclone.

According to the study conducted at the University of Reading (UK), a drought-hit area with a heat wave would absorb water slowly. The above findings can be applied to Sindh and Balochistan which were under drought conditions before the monsoon season and when it rained the area was badly flooded.

Yes, climate change is here but human-led activities cannot be ignored

While our climate is changing, we cannot solely hold it responsible. Water companies are draining groundwater, impacting evapotranspiration which in turn increases the likelihood of a severe heat wave as the soil is unable to release moisture when the temperature rises. Similarly, national issues like land encroachment, deforestation, lack of urban planning, and annual crop burning are also contributing to the rapid change in Pakistan’s climate. Until we address such matters, we should continue to brace for more calamities!

Read other articles on the changing climate of Pakistan and its impact;

1. Unprecedented Heat Waves and Rains in Sindh are worrying
2. The weather in Karachi is changing
3. Incidence of temperatures above 50°C has dramatically increased in Pakistan
4. Ever-increasing heat waves are a cause of concern in Pakistan
5. The migratory behaviour of the Red-Wattled Lapwing has a relationship with the monsoon season
6. Climate change and man-made disaster puts Karachi on the edge