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Abstract. Tree-ring δ18O values are a sensitive proxy for regional physical climate, while their δ13C values are a strong predictor of local ecohydrology. Utilizing available ice-core and tree-ring δ18O records from the central Himalaya (CH), we found an increase in east–west climate heterogeneity since the 1960s. Further, δ13C records from transitional western glaciated valleys provide a robust basis for reconstructing about 3 centuries of glacier mass balance (GMB) dynamics. We reconstructed annually resolved GMB since 1743 CE based on regionally dominant tree species of diverse plant functional types. Three major phases became apparent: positive GMB up to the mid-19th century, the middle phase (1870–1960) of slightly negative but stable GMB, and an exponential ice mass loss since the 1960s. Reasons for accelerated mass loss are largely attributed to anthropogenic climate change, including concurrent alterations in atmospheric circulations (weakening of the westerlies and the Arabian Sea branch of the Indian summer monsoon). Multi-decadal isotopic and climate coherency analyses specify an eastward declining influence of the westerlies in the monsoon-dominated CH region. Besides, our study provides a long-term context for recent GMB variability, which is essential for its reliable projection and attribution.

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Abstract:The extreme rainfall event during June 2013 in the Western Himalayas caused widespread flash floods, which triggered landslides, a lake-outburst, and debris flow. For the hydrological study of such an unexpected extreme event, it is essential to have reliable and accurate rainfall predictions based on satellite observations. The mountainous state of Uttarakhand is covered by complex topography, and this state has few, unevenly distributed, rain gauge networks. This unique study was conducted to evaluate three satellite based rainfall products (i.e., TMPA-3B42, Global Satellite Mapping of Precipitation (GSMaP), and NOAA CPC Morphing Technique (CMORPH)) against the observed rain gauge-based India Meteorological Department (IMD) gridded dataset for this rainfall episode. The results from this comprehensive study confirmed that the magnitude of precipitation and peak rainfall intensity were underestimated in TMPA-3B42 and CMORPH against gauge-based IMD data, while GSMaP showed dual trends with under-and over-predictions. From the results of the statistical approach on the determination of error statistic metrics (MAE (mean absolute error), NRMSE (normalized root mean square error), PBIAS (percent bias), and NSE (Nash-Sutcliffe efficiency)) of respective satellite products, it was revealed that TMPA-3B42 predictions were more relevant and accurate compared to predictions from the other two satellite products for this major event. The TMPA-3B42-based rainfall was negatively biased by 18%. Despite these caveats, this study concludes that TMPA-3B42 rainfall was useful for monitoring extreme rainfall event in the region, where rain-gauges are sparse.

Driven by the strength in local land–atmosphere coupling, inter‐annual variability of larger‐scale atmospheric circulations primarily determines a glacier's response to warming in high Asia. In this study, micrometeorological measurements in conjunction with regional reanalysis data set were analysed to examine seasonal land–atmosphere coupling strength at a typical central Himalayan (CH) glacier where the influence of Indian summer monsoon (ISM) predominates relative to winter‐westerlies. Energy–water (E–W) exchange and coupling behaviour were studied for the Pindari glacier based on sub‐hourly measurements of radiative–convective flux, state parameters, and sub‐surface thermal profiles using cross‐correlations between various E–W balance components. Coupling was positive in summer and winter accumulation seasons. However, it remained strongest during ISM. Coupling reversed during seasonal transition phases concurrent with distinct seasonality in E–W components. Lead–lag relation between some variables showed strong association at diurnal‐scale (VPD–Rn; VPD–LE; Rn–G), whereas some persisted beyond months (Rn–LE; Bowen ratio–precipitation; surface–air temperature). Weak association of variation of latent heat flux (LE) and rainfall was found during ISM at local scale than at regional scale, but with a lag, which was more prominent at regional scale. These observations indicate a seasonally variable coupling between E–W balance components through response–feedback mechanisms. Cross‐correlations of daily mean values of energy fluxes and meteorological variables reveal that Rn and air temperature are the prime drivers of energy balance. Net radiative energy (Rn) dominates energy exchanges at the glacier–atmosphere interface (governed primarily by the variation in net shortwave radiation), contributed on average 62% of the melt energy. However, sub‐surface heat flux along with the turbulent fluxes was the energy sinks of 24 and 15%, respectively. This study would help understand and parameterize E–W exchange pathways for ISM dominated CH glaciers in coupled glacier–climate models.

Vitamin B1 functionalised nano-ferrites: an organo-nanocatalyst for the synthesis of various spiro derivatives.

Climatic extremes including precipitation are bound to intensify in the global warming environment. The present study intends to understand the response of the Tons sub-watershed in Lesser Himalaya, in 3 years with entirely different hydrological conditions (July 2008-June 2011) in terms of discharge, sediment flux and denudation rates. Within an uncertainty limit of ±20%, the mean interannual discharge (5.74 ± 1.44 m 3 s −1) (±SE), was found highly variable (CV: 151%; 0.8-38 m 3 s −1). In a normal rainfall year (2008-2009; ∼1550 mm), the discharge was 5.12 ± 1.75 m 3 s −1 , whereas in a drought year (2009-2010), it reduced by 30% with the reduction in ∼23% rainfall (CV: 85%). In an excessive rainfall year (once-in-acentury event) (2010-2011; ∼3050 mm), discharge as well as total solid load was ∼200% higher. Monsoon months (July-September) accounted for more than 90% of the annual solid load transport. The ratio of dissolved to suspended solid (C/P ratio) was consistently low (<1) during monsoon months and higher (1-7) during the rest of the dry period. C/P ratio was inversely (R 2 = 0.49), but significantly (P <0.001) related to the rainfall. The average mechanical erosion rate in the three different rainfall years was 0.24, 0.19 and 1.03 mmyr −1 , whereas the chemical erosion was estimated at 0.12, 0.11 and 0.46 mmyr −1 , respectively. Thus, the average denudation rate of the Tons sub-watershed has been estimated at 0.33 mmyr −1 (excluding extreme rainfall year: 1.5 mmyr −1). Our results have implications to understand the hydrological behaviour of the Lesser Himalayan watersheds and will be valuable for the proposed and several upcoming small hydropower plants in the region in the context of regional ecology and natural resource management.