Department of Remote Sensing and GIS, Vidyasagar University, Midnapore, West Bengal, India.
Environ Sci Pollut Res Int. 2024 Mar;31(15):22471-22493. doi: 10.1007/s11356-024-32286-1. Epub 2024 Feb 26.
Uncertainty and uneven distribution of monsoonal rainfall and its consequences on crop production is a matter of serious concern in India, specifically, in the Indo-Gangetic plain region. In this study, drought patterns were investigated through standardised precipitation index (SPI) of varying timescales, using the India Meteorological Department (IMD) precipitation data (1901-2021). We analysed the spatio-temporal pattern of different drought characteristics (frequency, duration, severity, intensity) of the Indian Gangetic basin using run theory. The bivariate copula method has been incorporated to combine two drought properties (severity and duration). Copula integrates multivariate distribution and considers the dependency rate among the variables. The five most widely used copulas from various copula families, elliptical (normal, t-copula) and Archimedean (Clayton, Gumbel, Frank), were estimated for modelling, and the best fit copula was selected. The study revealed that seasonal drought is more frequent and intense in the Upper and Middle Gangetic Plain, whereas annual drought is quite scattered in nature. It is worthy to mention that downward drought trends were observed in this agricultural belts significantly after 1965; specifically, in the Upper, Middle, and Trans Gangetic Plain regions. With increasing drought duration and severity, the drought return period raised, but the frequency decreased gradually. Most of the droughts characterised by less duration and severity occurred with a return period below 10 years for the whole region. The major 100 + years return period droughts were to be found after 1960 and their frequencies were significantly higher after 2000. The most recent remarkable droughts with more than 100 years of return occurred during 2008-2011 and 2016-2018 in the Upper and Middle Gangetic plains, whereas in the Lower Gangetic plain, a hundred-year return period drought was occurred during 2010-2013. This study provides agroclimatic-zones-wise significant information of drought characteristics and its nature of occurrence in the Indian Ganga Basin. The results enhance the understanding of drought management and formulation of adaptive strategies to mitigate the adverse impact of droughts.
季风降雨的不确定性和分布不均及其对作物生产的影响是印度，特别是印度恒河平原地区严重关切的问题。本研究通过使用印度气象部门（IMD）降水数据（1901-2021 年），使用不同时间尺度的标准化降水指数（SPI）来研究干旱模式。我们使用运行理论分析了印度恒河流域不同干旱特征（频率、持续时间、严重程度、强度）的时空模式。二元 copula 方法已被纳入到结合两种干旱属性（严重程度和持续时间）中。copula 集成了多元分布并考虑了变量之间的依存率。从各种 copula 家族中选择了五个最广泛使用的 copula（椭圆（正态，t-copula）和阿基米德（Clayton，Gumbel，Frank））进行建模，并选择了最佳拟合 copula。研究表明，上恒河平原和中恒河平原的季节性干旱更为频繁和强烈，而年度干旱则较为分散。值得一提的是，自 1965 年以来，这些农业带的干旱趋势明显呈下降趋势；特别是在上恒河平原、中恒河平原和跨恒河平原地区。随着干旱持续时间和严重程度的增加，干旱重现期增加，但频率逐渐降低。整个地区大部分持续时间和严重程度较低的干旱都发生在 10 年以下的重现期内。主要的 100 年以上重现期干旱发生在 1960 年之后，其频率在 2000 年之后显著增加。最近发生的在恒河平原上和上恒河平原上发生的、持续时间超过 100 年的显著干旱发生在 2008-2011 年和 2016-2018 年，而在恒河平原下游，发生了一次持续时间为 100 年的干旱。年重现期干旱发生在 2010-2013 年。本研究提供了印度恒河流域农业气候带的干旱特征及其发生规律的重要信息。研究结果提高了对干旱管理的认识，并为制定适应策略以减轻干旱的不利影响提供了依据。
