Influence of large-scale circulation and interannual modes of climate variability on seasonal drought characteristics over Pakistan

Abstract

The long-term drought monitoring and its assessment are of great importance for meteorological disaster risk management. The recurrent spells of heatwaves and droughts have severely affected the environmental conditions worldwide, including Pakistan. The present work sought to investigate the spatiotemporal changes in drought characteristics over Pakistan during Rabi and Kharif cropping seasons. The role of large-scale circulation and interannual mode of climate variability is further explored to identify the physical mechanisms associated with droughts in the region. Monthly precipitation and temperature data (1983–2019) from 53 meteorological stations were used to study drought characteristics, using the standardized precipitation evapotranspiration index (SPEI). The non-parametric Mann-Kendall (MK), Sen’s Slope (SS), and Sequential Mann-Kendall (SQMK) tests were applied on the drought index to determine the statistical significance and magnitude of the historical trend. The state-of-the-art Bayesian Dynamic Linear (BDL) model was further used to analyze large scale climate drivers of droughts, analysis revealed an increase in drought severity mostly over arid to semi-arid regions for both cropping seasons. Temperature played a significant role in defining droughts over dry and hot seasons, while rainfall is influential over the western disturbances (WD) influenced region. The analysis of atmospheric circulation patterns revealed that large-scale changes in wind speed, air temperature, relative humidity and geopotential height anomalies are the likely drivers of droughts in the region. We found that Niño4, Sea Surface Temperature (SST), and multivariate El Niño-Southern Oscillation (ENSO4.0) Index are the most influential factors for seasonal droughts across Pakistan. Overall, the findings provide a better understanding of drought-prone areas in the region, and this information is of potential use for mitigating and managing drought risks.

Recent and projected changes in water scarcity and unprecedented drought events over Southern Pakistan

“…Most of the country's southern region has been greatly hit by droughts with a decrease in precipitation. Fluctuations in rainfall patterns caused by large-scale drivers (South Asian summer monsoon and ENSO) have caused severe dry/warm conditions in Pakistan as a result of the warmer climate (Ullah et al, 2022c). Over Pakistan, the monsoon currents flow divide into two branches: the Southeastern monsoon (SEM) and the Northeastern monsoon (NEM).…”

“…This trend pattern may be caused by increased moisture transport together with warmer SSTs, southwesterly/southerly tide over the Arabian Sea (AS), and a westward movement of the South Asian monsoon trough (Preethi et al, 2017). As a result, the monsoon rainfall has augmented considerably in the northern regions of Pakistan, whereas a substantial decrease was noticed from western to southern areas that are declared drought-prone regions of the country (Hina et al, 2021;Ullah et al, 2022c). The drought episode of 1999-2002 is considered the most devastating that affected about 2,200,000 individuals across the country and in human and animal losses, crop failures, and large-scale migrations (Ahmad et al, 2018).…”

Spatiotemporal Rainfall Variability and Drought Assessment during Past Five Decades in South Korea Using SPI and SPEI

“…Thus, water shortfall for agricultural needs lead to agricultural drought and less soil moisture affect crops and their yield, causing starvation, which can ultimately trigger socioeconomic drought [9,13]. Shortage of rainfall is the main cause of drought, but other factors of climate can increase its severity, i.e., high temperature, wind, and humidity [8,10,14,15]. Drought occurs frequently around the world for months, a season, or even years, but drought characteristics vary in terms of climate zones [12].…”