Reconstruction of July-September Standardized Precipitation-Evapotranspiration Index (SPEI) for the Hindu Kush region of Northern Pakistan

Abstract

Abstract The Prolonged drought resulting from global warming is considered an important factor affecting the Asia's socioeconomic growth of West Asia, with a significant impact on the dynamic forecasting of water supply and forest ecosystems. In such a scenario, Understanding future long-term drought (SPEI) changes is crucial for accurately forecasting regional drought shifts in the Hindukush region. In this study, a 517-year (1506-2022 CE) long tree-ring width chronology of the Himalayan Cedar (Cedrus deodara D. Don) from the eastern Hindukush has been developed. The July-September SPEI has revealed a positive and significant relationship (r = 0.633, p < 0.001) with tree growth, which leads to SPEI reconstruction from AD 1626 in the Hindu Kush Region. Our reconstruction model has explained 40.01% of the climate variance during the instrumental period from AD 1965 to 2018. Fourteen wet periods (≥ 3 years) were observed before the instrumental period, specifically in C.E. 1629–1635, 1638–1658, 1666–1674, 1680–1701, 1715–1724, 1770–1776, 1794–1797, 1802–1810, 1822–1846, 1850–1857, 1872–1881, 1883–1890, 1906–1914, and 1921–1937. Similarly, twelve dry summer periods were also observed in the past 339 years, such as C.E. 1659–1665, 1675–1679, 1702–1714, 1725–1769, 1777–1793, 1798–1801, 1811–1821, 1847–1849, 1858–1871, 1891–1905, 1915–1920, and 1938–1963. Nevertheless, AD 1663 was individually the wettest (with a value of 2.13), while AD 1754 was the driest (-0.99) year. The spatial correlation analysis and its comparisons with Karakoram-Himalayan drought and precipitation reconstructions have convincingly confirmed the reliability of our SPEI reconstruction. Consequently, this reconstruction can effectively serve as a proxy for large-scale drought variability in the Hindu Kush region of northern Pakistan. Our findings strongly suggest the considerable dendrochronological potential for further climatological studies in the western Hindu Kush Mountains System.