Investigation of causes and characteristics of monsoon extremes in Pakistan: a case study for monsoon 2022

Abstract

Apart from the long-term changes in the climate patterns, the extreme weather conditions (heat waves, heavy precipitation, and droughts) have also emerged as a prominent consequence of the global climate change. Pakistan being listed among the most susceptible nations to the changing climate patterns has witnessed an increasing trend of extreme precipitation (particularly during monsoon). Therefore, this study was conducted to probe the major meteorological causes of extreme monsoon precipitation in Pakistan, with a special focus on the monsoon 2022, that lead to severe flooding and devastation of infrastructure, agriculture, and loss of lives. The methodology included an in-depth analysis of unusual atmospheric conditions that triggered exceptionally high precipitation. For this purpose, a number of 25 stations across the country lying in the southwest monsoon zone were selected. The analysis revealed that in April 2022, about 1.2 to 6.0 °C above normal temperature was observed in Balochistan, 2.0 to 4.5 °C in Sindh, and 3.0 to 5.8 °C in Punjab and KPK. Similarly, in May, about 1.0 to 3.5 °C above normal temperature was observed in Sindh and Balochistan, and 1.0 to 3.0 °C in Punjab and KPK. Due to this exceptional warming, an intense trough developed over the area. In April, about 0.5 to 2.5 mb below normal air pressure was observed in Sindh and Balochistan, and 1.5 to 2.2 mb in Punjab. In May, about 1.0 to 3.0 mb below normal air pressure was observed over the study area. For precipitation, the analysis unearthed that in July 2022, about 100 to 300 mm above normal monthly rainfall was received in Sindh, 50 to 200 mm in Punjab and Balochistan, and 5 to 30 mm in KPK. In August, about 100 to 500 mm above normal rainfall was received in Sindh, and 50 to 250 mm in KPK and Balochistan. However, in September, about 15 to 75 mm above normal rainfall was received in Punjab, while the remaining stations showed a negative departure. Conclusively, the unusual pre-monsoon heating resulted in an intense depression over the plains that facilitated the excess moisture penetration from the Indian Ocean, and consequentially extreme precipitation in Pakistan in 2022. The study outcomes are expected to help in devising an effective climate change adaptation and mitigation strategy for the country and to conduct further research on the prediction and analysis of extreme weather conditions under the changing climate patterns.