The climatic conditions are changing and showing their impact on the glaciers. The melting of glaciers is amplified in the recent past and in the present time due to increased global warming. Consequently, the hazardous events of glacial lake outburst floods (GLOFs) are posing a serious threat to the population in the Himalayan region. Many events of GLOFs have caused a huge loss of life and property in the downstream mountain regions. Therefore, there is an essential requirement of developing an effective early warning system to alert masses before any disastrous incident. In this paper, we reviewed the studies related to the GLOF events in the Indian and surrounding Himalayan region. Our main aim for this study is to emphasize the need for an early warning system and in this connection, we are proposing the wireless sensor network (WSN) based system. In the present time, the WSN based early warning systems are gaining popularity in the domain of different natural hazards due to their low cost of installation, maintenance and capability of real-time monitoring. For that reason, these kinds of early warning systems can be installed at multi-locations in a planned manner. This will help authorities for forming mitigation and executions plans as well as downstream people will be attentive regarding any unfortunate GLOF related catastrophe.

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 (δ 13C and δ 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-à-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.

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.

Soil temperature is one of the most important glacio-meteorological parameters that play a critical role in glacier energy and mass balance dynamics, surface hydrological processes, and glacier-atmosphere interaction. However, the availability of the data is acutely scarce in the Himalayan glaciated region. In this study, we applied artificial neural network (ANN) models for the prediction of soil temperature of glacial forefield region of the Pindari Glacier (Central Himalaya). Three-layer feed-forward ANN models were developed and tested for estimating multi-depth soil temperatures using concurrent and antecedent air-soil temperature data for one complete annual cycle as inputs for the models. Models with different combinations of input variables were tested, and best sets of variables were selected based on the prediction accuracy. Rigorous statistics were further employed to compare the performances of different models. High concurrence was obtained between ANN-estimated and measured soil and air temperatures as evident by various correlation coefficients and error ranges. In a boarder perspective, our results point toward the applicability of developed ANN models to provide robust soil temperature prediction for the glacial forefield regions of the Central Himalaya.

General comments: This paper of Singh et al. reconstructed and analyzed the glacier mass balance since 1743 in central Himalaya, using tree ring carbon isotope, it is meaningful for the understanding the glacier variation in Himalaya area. Response: We are thankful to the reviewer for valuable comments and suggestions that improved this manuscript. In this paper, we reconstructed annual variability of four ‘benchmark glaciers’ of the Uttarakhand Himalaya utilizing tree-ring carbon isotopes of two dominant conifer species growing in the valleys. We also analyzed the variability of tree-ring and ice-core oxygen isotopes on a central Himalayan-scale. Comment: However, the

Comments to authors: The manuscript, titled "Central Himalayan tree-ring isotopes reveal increasing regional heterogeneity and enhancement in ice-mass loss since the 1960s", tries to address the correlation between δ 13C and glacier mass balance and their temporal evolution in the past. The authors provided a detailed description of their tree ring isotope measurements and showed a decent correlation with the reconstructed glacial mass balance for the past 273 years in the central Himalaya. The authors attempted several different statistical tests and presented their results. The results clearly show a shift in climate proxies since 1960’s. The supplementary figures

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.

A weather monitoring system was developed using open-source hardware and software, with the main objective of collecting meteorological data at a very low cost, from the remote terrain of the Indian Himalaya.

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-a-century 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.

Regions of strong land–atmosphere coupling will be more susceptible to the hydrological impacts in the intensifying hydrological cycle. In this study, micrometeorological experiments were performed to examine the land–atmosphere coupling strength over a heat low region (Thar desert, NW India), known to influence the Indian summer monsoon (ISM). Within the vortex of Thar desert heat low, energy–water exchange and coupling behavior were studied for 4 consecutive years (2011–2014) based on sub-hourly measurements of radiative–convective flux, state parameters and sub-surface thermal profiles using lead-lag analysis between various E–W balance components. Results indicated a strong (0.11–0.35) but variable monsoon season (July–September) land–atmosphere coupling events. Coupling strength declined with time, becomes negative beyond 10-day lag. Evapotranspiration (LE) influences rainfall at the monthly time-scale (20–40 days). Highly correlated monthly rainfall and LE anomalies (r = 0.55, P < 0.001) suggested a large precipitation memory linked to the local land surface state. Sensible heating (SH) during March and April are more strongly (r = 0.6–0.7) correlated to ISM rainfall than heating during May or June (r = 0.16–0.36). Analyses show strong and weak couplings among net radiation (Rn)–vapour pressure deficit (VPD), LE–VPD and Rn–LE switching between energy-limited to water-limited conditions. Consistently, +ve and −ve residual energy [(dE) = (Rn − G) − (SH + LE)] were associated with regional wet and dry spells respectively with a lead of 10–40 days. Dew deposition (18.8–37.9 mm) was found an important component in the annual surface water balance. Strong association of variation of LE and rainfall was found during monsoon at local-scale and with regional-scale LE (MERRA 2D) but with a lag which was more prominent at local-scale than at regional-scale. Higher pre-monsoon LE at local-scale as compared to low and monotonous variation in regional-scale LE led to hypothesize that excess energy and water vapour brought through advection caused by pre-monsoon rainfall might have been recycled through rainfall to compensate for early part of monsoon rainfall at local-scale. However, long-term measurements and isotope analysis would be able to strengthen this hypothesis. This study would fill the key gaps in the global flux studies and improve understanding on local E–W exchange pathways, responses and feedbacks.

The possibility of detecting buried objects remotely has spellbound mankind over centuries. As yet, no single method has been found which could provide the ground and its contents clearly visible. Ground penetrating,-probing or surface-penetrating radar has been found to be an especially attractive option. The last two decades have witnessed major advances and the range of applications is ever-increasing for Ground Penetrating Radar (GPR) methods and the complexity of signal recovery techniques, hardware designs and operating practices is increasing as the technology is maturing. Now we are in a much better position to understand that in which type of geographical settings GPR is effective. Not only do we understand the fine scale geological texture better than we ever did before, we also have attained a good understanding of the physical properties which can control the penetration and reflection of radio waves.Instrumentation developments are also on the progressing note. Radar systems with higher power and high quality digital data recording capability have been developed. Furthermore, digital data processing capability and presentation is enhanced over the years which were thought to be an impossible task just a few years ago. The evolution of quantitative interpretation tools for GPR is just beginning. Though the technique is still not infallible and much is still to be explored, GPR is now a recognized weapon in the geophysical arsenal. In favourable geographical settings, GPR is unparallel in possession of detailed information.