Understanding spatiotemporal variability of drought in recent decades and its drivers over identified homogeneous regions of India

Abstract

Drought is a recurring hydroclimatic extreme whose frequency and intensity have increased over India in recent decades, with a detrimental effect on regional water resources. This study addresses the spatiotemporal variability of drought and its plausible mechanism over India from 1951 to 2018. Firstly, six drought‐homogeneous regions are adequately ascertained by applying rotated empirical orthogonal function analysis using the Standardized Precipitation Evapotranspiration Index that captures most of the reported drought and regional hydroclimatic patterns. For the study period, a drying trend is witnessed across the regions though not significant, whereas in recent decades, northeast India (NEI) and some parts of the Indo‐Gangetic plain (IGP) exhibit higher drought frequency. This anomalous drying is attributed to a weakening of the monsoon circulation and accelerated warming caused by changes in the land‐use pattern. The interplay between El Niño Southern Oscillation and the Indian Ocean Dipole largely affects drought's interannual variability, which shows a modified response in recent decades. However, the long‐term decadal drought pattern is found to be strongly teleconnected with a newly discovered Southern Atlantic Oscillation (SAO) index, which reveals a statistically quite significant relationship (>50%) with drought variability. The positive phase of the SAO index is generally associated with drought across the regions except for IGP and NEI. Despite the recent overall wetting trend, drought frequency has enhanced over most of the regions, modulating the regional hydrological cycle.

Spatiotemporal variability of droughts over the Arabian Peninsula and associated mechanisms

“…Together, these modes explained a variance of 83%. That these modes retain such a considerable proportion of variation is an important criterion for their selection as relevant patterns of dominant variability 35,51 . Importantly, the maximum loadings in the gravest four REOFs were concentrated in distinct quadrants (Fig.…”

“…Pearson correlation analysis was used to determine the association between the variables examined in this study. We identi ed abrupt changes in SPEI variability using the Change Point Model (CPM) 60 , which has been used in hydroclimatic studies to detect multiple change points in a single timeseries 35,61 . The CPM method involves processing an entire sequence of observations, for example, a timeseries of rainfall at a grid-point.…”

“…The widely-used PDSI uses several parameters that are not readily accessible for long-term assessments 3,34 . It is also subject to several limitations; for example, it generally shows a lagged response for individual events and is only calculated for a single timescale 35 .…”

Long‐Term Variability in the Arabian Peninsula Droughts Driven by the Atlantic Multidecadal Oscillation

“…We applied Sen's slope method (Sen, 1968) and the Mann-Kendall test (Kendall, 1975;Mann, 1945) to determine monotonic trends in time series such as the SPEI and their statistical significance. We identified abrupt changes in SPEI variability by using the change point model (CPM) (Ross, 2015), which is commonly employed in hydroclimatic studies (e.g., Saharwardi et al, 2022;Shirvani, 2017). We further applied the Granger causality test (Granger, 1969) to identify the causal relationship between decadal SPEI variability and AMO.…”

Assessment and characterisation of hydrometeorological droughts in the Upper Mzingwane sub-catchment of Zimbabwe

“…Drought frequency and intensity have increased in recent decades due to climate change (Saharwardi et al, 2022;Peng et al, 2022;Piraino et al, 2022;Uwimbabazi et al, 2022). Meteorological, hydrological, agricultural and other forms of drought have severe impacts on water-dependent sectors (Zarei et al, 2021).…”