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Annual cycle of ENSO Index during observed El Niño and La Niña years between 1950 and 2016. Basic data source: NOAA (https://origin.cpc.ncep.noaa.gov), shaded is the threshold crossing period of ENSO Index. The absolute values of ENSO Index during La Niña years are considered for presentation purpose
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This investigation highlights changes and various facets of inter-connections between rainfall over India and its prominent drivers such as Southern Oscillation (SO) and Indian Ocean Dipole (IOD). As the monsoon rainfall over majority of sub-divisions from Northeast India (NEI) and Central Northeast India regions (53% area) exhibits declining trend...
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In recent decades, water scarcity is a significant constraint for socioeconomic development and threatens livelihood in an agriculture-based developing country like Pakistan. The water crisis in the country is projected to exacerbate in the coming years, especially in the southern parts. This dire situation calls for an investigation of major droug...
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... Past studies (Kripalani and Kumar 2004, Kumar et al 2009, Rao et al 2012, Abish et al 2018, Todmal et al 2022 reported that the sea surface temperature of western Indian Ocean is non linearly increasing, particularly after 1960. It is argued that the warming in the western Indian Ocean is perhaps influenced by surplus heat transported from the Pacific Ocean to the Indian Ocean (Dong et al 2016), increased solar flux absorption due to less cloud cover (Mayer et al 2013) and increased greenhouse gases concentration (Du and Xie 2008). ...
The Indian Ganga Basin (IGB) is one of the most valuable socioeconomic regions in the Indian subcontinent. The IGB supports more than half a billion people due to an abundant supply of freshwater for agro-industrial purposes, primarily through Indian Summer Monsoon (ISM) rainfall contributions (~85%). Any alterations in ISM characteristics would significantly affect freshwater availability, and as a result, socioeconomic activities would be affected. Therefore, in this study, we have attempted to assess how the monsoon rain spell characteristics, i.e., peak, volume, and duration, altered historically between 1901 to 2019. We further analyzed the specific IGB regions where monsoon rain spell changes are more prominent and their hydrological implications. Our estimates reveal that short-duration high-magnitude rain spells have significantly increased across the major regions of the IGB after 1960, which implies the increased probabilities of flash flood hazards. At the same time, the rain spell volumes have been depleted across the IGB after 1960, especially in the eastern Indo-Gangetic plains and southern IGB regions, indicating increased drought frequencies. Further, Himalayan regions, i.e., upper Ganga, upper Yamuna, and upper Ghaghra, have demonstrated increasing magnitudes of rain spell peaks, volume, and duration post-1960. In addition, the continuous warming and anthropogenic alterations might further exaggerate the current situation. Thus, these inferences are helpful for river basin management strategies to deal with the extreme hydrological disasters in the IGB.
... Further, there is an increase in summer monsoon rainfall over northwestern parts of the west coast in India (Preethi et al., 2017). Coupled ocean-atmospheric interactions, i.e., Southern Oscillation (SO) and Indian Ocean Dipole (IOD), play a significant role in regulating the rainfall over the Indian sub-continent (Maharana et al., 2021;Todmal et al., 2022). Generally, La Nina events are associated with above-average rainfall over India (Kripalani & Kulkarni, 2001). ...
... An overall increase in rainfall in the last 40 years over the basin can be associated with Southern Oscillations and the active phase of the Indian Ocean dipole (the negative phase of the IOD generally causes above-average rainfall). Todmal et al. (2022) have suggested that the years with positive Southern Oscillation Index (SOI) experienced above-average rainfall. This indicates that large-scale ocean-atmosphere interactions can influence rainfall at a regional river basin scale (Todmal, 2020). ...
... Variability in inter-decadal rainfall may be caused because of variation in the complex relationship between the Sothern Oscillation Index and Monsoon rainfall, which is attributed to a zonal shift in the Centre of ENSO. Further, human-induced warming has contributed to a weakening of the SOI-Annual Rainfall index between 1995 and 2016, which has resulted in an abrupt shift in rainfall pattern (Maharana et al., 2021;Todmal et al., 2022). ...
The present study investigates long-term changes in the rainfall regime over the Sabarmati River Basin, Western India, during 1981–2020 using computational and spatial analysis tools. Daily gridded rainfall data from India Meteorological Department (IMD) at 0.25 × 0.25 spatial resolution was employed to determine changes in rainfall at annual, monthly, and seasonal scales and analyze changes in rainfall characteristics using different thresholds for dry/ wet days and prolonged spells over Western India. Mann–Kendall test, Sen slope estimation, and linear regression analysis indicate that annual and monsoon rainfall over the basin has increased while the rest of the seasons have shown a declining trend. However, none of the trends obtained was found to be statistically significant. Spatial analysis of rainfall trends for each decade between 1980 and 2020 revealed that certain parts of the basin had experienced a significant declining trend during 1991–2000. Monthly rainfall analysis indicates the presence of a unimodal distribution of rainfall and a shift in rainfall towards later monsoon months (August and September). It is also inferred that days with moderate rainfall have decreased while low and extreme rainfall events have increased over the basin. It is evident from the study that the rainfall regime is highly erratic, and the study is important in understanding the changes in the rainfall regime during the last 40 years. The study has significant implications for water resource management, agricultural planning, and mitigation of water-related disasters.
... Several studies have found that ENSO significantly affects the ISMR (Ashok & Tejavath, 2019;Hrudya et al., 2021;Varikoden et al., 2015). The ISMR has become relatively weak (stronger) all through establishing El Nino (La Nina) years, despite the fact that the negative relation between ENSO indices and ISMR must have weakened in recent epochs (Goswami & Chakravorty, 2017;Goswami et al., 2016;Todmal et al., 2022). Various investigations observed that floods have even more short active spells of the summer monsoon, although drought have long break spells (Rajeevan et al., 2010;Rajesh & Goswami, 2020;Vishnu et al., 2022). ...
The basic and derived meteorological parameters, are important factors that affect the epochal changes of monsoonal drought/flood events which consequently influence the socio‐economic aspects of India. The anomalous tricade departure of parameters namely rainfall, surface pressure, surface temperature, zonal and meridional wind, cloud cover (CC), outgoing longwave radiation, latent heat flux (LHF), sensible heat flux, net incoming shortwave radiation flux and net heat flux (NHF) have been considered between past, and recent tricade respectively drought and flood events. An anomalous decrease (−3 to −2 mm/d) in rainfall over the southern Arabian sea (AS), southern peninsular India and Bay of Bengal during past and recent tricade, on the other side increase (2–2.5 mm/d) in rainfall over the equatorial Indian ocean (EIO) during drought. The drought episode of the recent tricade is showing basin wise significant increase in LHF (20–30 W/m²) and decrease in NHF (−30 to −60 W/m²) from the Somali coast to Indonesian region which is linked with changing oceanic processes linked with the Indian ocean warming. The comparison of past and recent monsoonal flood has shown decrease in the CC over EIO and AS region which supported anomalous highest departure in LHF (12 W/m²) over EIO. A direct association of dry and moist static energy variations have been found to be linked with the surface fluxes during Indian summer monsoon season. Further, epochal differences of vertically integrated moisture flux convergence is consistent with flood/drought rainfall anomaly. Thus, radiative imbalance also plays a secondary role in determining epochal nature of drought/flood variability and its nature.
Recent climatic changes and anthropogenic activities considerably affect regional water resources, particularly in water‐scarce regions. The present study, therefore, aims to understand the changes in monsoon rainfall, potential evapotranspiration (PET), surface runoff, dam storage and groundwater in the drought‐prone region of Maharashtra. The analyses of trend and step‐change were carried out using standard parametric tests. The results were verified with the application of non‐parametric statistical techniques. Notably, monsoon rainfall and runoff were observed to be declining. Exceptionally, the Yerala Basin witnessed significant increase in rainfall along with heavy rainfall events. Contradictorily, Agrani and Man Basins registered a notable decline in rainfall and runoff. As vulnerability to hydrological disasters is high, these basins should be carefully monitored. Although surface water harvesting brought a positive change in post‐monsoon groundwater level, it was the main reason for a decline in runoff volume at downstream reaches, which led to intra‐basin water disparity. The study area witnessed significant increase in groundwater extraction. Unfortunately, the misuse of government‐subsidized schemes exacerbates groundwater exploitation and stockpiling of water resources. Moreover, the increasing rate of PET augments hydrological losses and amplifies water distress. Interestingly, almost all the hydrological changes were notably experienced during the post‐2000 period. To cope with present and future water scarcity problems, it is therefore necessary to restrict irrational use and allocation of available limited water resources. The findings that emerge from this investigation may help to formulate judicious water policies and plans which could be implemented by the government, agronomists, water resource managers and farmers.
The present investigation endeavored to understand trends in climatic, hydrological, and agricultural variables in the five semi-arid river basins of Maharashtra (India). For this, parametric and non-parametric statistical techniques were applied. The monsoon rainfall over the study area reveals no considerable increase during the past (1981–2013) and future (2020–2050). Although the construction of a large number of impoundment structures during the last two decades resulted in a significant rise in post-monsoon groundwater table (by 40 cm/decade), it caused a decline in surface runoff. The study area witnessed a significant increase in area under irrigated crops at the cost of rainfed crops, which resulted in a significant increase in groundwater withdrawal (GWW) by 70 cm/decade. The cropped area and productivity of irrigated crops heavily depend on rainfall and groundwater resources. Moreover, the Southern Oscillation Index (SOI) has a positive connection with the productivity of irrigated crops. On the other hand, a considerable increase in annual minimum temperature (AMNT), annual maximum temperature (AMXT), and annual mean temperature (AMT) (by 1.02, 0.50, and 0.82 °C, respectively) along with a rise of > 100 mm in potential evapotranspiration (PET) is registered during 1985–2015. The study indicates that the irrigated crops are more vulnerable to heat stress, as PHS (plant heat stress with > 34 °C) days show a considerable increase (2–5 days/decade). Furthermore, the climate projection suggest a significant rise of 1.05 °C in AMT by 2050, which is very likely to intensify the hydro-meteorological droughts and adversely affect the agricultural productivity of rainfed and irrigated crops as well. Briefly, the human-induced changes in cropping patterns (without a considerable increase in rainfall/water resource) from one side and the climatic changes (including extreme events) on the other side may exacerbate the regional water scarcity and food security challenges in the semi-arid region of Maharashtra (India) in the near-term future.
