Browsing by Author "Singh, Jayendra"

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    Climate-driven acceleration in forest evapotranspiration fuelling extreme rainfall events in the Himalaya
    (IOP Publishing Ltd, 2021) Singh, Nilendu; Singh, Jayendra; Gupta, Anil K.; Brauning, Achim; Dimri, A.P.; Ramanathan, A.L.; Sharma, Vikram; Tiwari, Reet Kamal; Chakraborty, Joyeeta Singh; Chauhan, Pankaj; Shukla, Tanuj; Singhal, Mohit; Rawat, Suman; Agarwal, Shefali; Raja, P.
    Warming-induced expansion in vegetation coverage and activity can accelerate the montane hydrological regimes. However, the climate impacts on ecohydrology of forested valleys of the Himalaya are uncertain. In this study, utilizing results of about three centuries of cellulose isotope chronologies (? 13C and ? 18O) of dominant tree species, geo-chronological proxies, bio-geophysical dataset and simulations including satellite observations, we show an activation in the ecophysiological processes including evapotranspiration (ET) since the 1950s. Observation suggests rapid greening, while isotopic records indicate enhanced assimilation and transpiration in deciduous species vis-a-vis conifers post 1950s. Given strong vegetation-precipitation feedback and superimposed on the increasing trends of conducive atmospheric factors affecting valley-scale convective processes, intensification in forest ET is manifesting in a progressive enhancement in extreme rainfall events (EREs) since the last few decades. Results suggest that representation of ecophysiological processes and dynamics of seasonal moisture loading in observational and modelling framework is critical for understanding EREs under climate change. � 2021 The Author(s). Published by IOP Publishing Ltd.
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    Temperature variability over Dokriani glacier region, Western Himalaya, India
    (Elsevier Ltd, 2023) Rastogi, Tanupriya; Singh, Jayendra; Singh, Nilendu; Chauhan, Pankaj; Yadav, Ram R.; Pandey, Bindhyachal
    Long-term climate records which help decipher past climate variability and its impact are scarce in the tough terrain of the Himalayan region. Therefore, in order to fill the climate data gap and understand the glacier climate linkage, we developed a 231 year long (1785�2015 CE) March�June temperature record using ring-width chronology of Himalayan fir (Abies pindrow (Royle ex D.Don) Royle) for the Din Gad valley, Dokriani glacier region, Uttarkashi, Uttarakhand, in the Western Himalaya. The Din Gad, originating from the Dokriani glacier, is a meltwater river contributing to Bhagirathi catchment in the headwaters of the socio-economically vital Ganga River. The 21-year running mean of the temperature record showed 1978�1998 CE as the coldest period followed by 1925�1945 CE, and 1890�1910 CE as the warmest period followed by 1946�1966 CE over the entire time series. The reconstruction matches well with tree-ring based temperature records available from the Garhwal Himalaya. It also shows similarity to tree-ring based temperature reconstructions from the Western Himalaya, Nepal, Tibetan Plateau and Bhutan, thus displaying a regional scale climate signal. The low frequency fluctuation patterns of the March�June temperature also matches with Asia and Northern hemisphere temperature records. Reconstructed March�June temperature record showed a statistically negligible warming temperature trend during 1901�1989 CE in the 20th century. It, however, captured a warming spike from 1990s CE which continues rising into the 21st century, which is also evident in the Northern hemisphere temperature record. Moreover, temperature rise is not anomalous in the past 231 years and well within range of the rest of the series. The present temperature record exclusively from the glacier region revealed a strong linkage with the benchmark Dokriani glacier's winter mass balance (November�April) revealing mass loss (gain) episodes occurred in warm (cool) phases. This first such record from the glacier valleys in Ganga headwaters would be of great value at providing insight into past climate variability and glacier behaviour with respect to climate change in long term perspective, and thus would provide valuable information for water resource management in light of climate change. � 2023 Elsevier Ltd and INQUA