• Sunil Oulkar

Articles written in Journal of Earth System Science

• Distribution of lightning in relation to topography and vegetation cover over the dry and moist regions in the Himalayas

The impacts of elevation, terrain slope and vegetation cover on lightning activity are investigated for contrasting environments in the north-east (NE) (21–29$^{\circ}$N; 86–94$^{\circ}$E) and the north-west (NW) (28–36$^{\circ}$N; 70–78$^{\circ}$E) regions of the Himalayan range. Lightning activity is more at a higher terrain slope/elevation in the dry NW region where vegetation cover is less, whereas it is more at a lower terrain slope/elevation in the moist NE region where vegetation cover is more. In the wet NE, 86% (84%) of the annual lightning flash rate density (LFRD) occurs at an elevation < 500 m (terrain slope < 2%) and then sharply falls off at a higher elevation (terrain slope). However, only 49% (47%) of LFRD occurs at an elevation of < 500 m (terrain slope < 2%) and then rather gradually falls off at a higher elevation (terrain slope) in the dry NW. The ratio of the percentages of LFRD and elevation points is much higher in the NW than in the NE above an elevation of ${\sim}$1000 m. The impacts of terrain slope and elevation in enhancing the lightning activity are stronger in the dry NW than in the moist NE. The correlation coefficient of the LFRD with the normalised difference vegetation index is higher in the NW than in the NE on both the regional and annual scales. Results are discussed as a caution in using any single climate variable as a proxy for projecting a change in the lightning–climate relationships in the scenario of global warming.

• Water discharge and suspended sediment dynamics in the Chandra River, Western Himalaya

Glacier systems are important components of the hydrological cycle and a major source of meltwater and sediment flux that controls the river ecology, water quality, and hydropower generation in the Indian Himalayan Region (IHR). Thus, understanding short- and long-term changes in water and suspended sediment (SS) dynamics is crucial in highly sensitive pro-glacial Himalayan Rivers. In the present study, the Chandra River basin in Western Himalaya was chosen to study river discharge, SS transport dynamics, physical erosion rate, and their governing factors for the 2017 melting season (May–September). The daily mean water discharge and SS concentration in the Chandra River was 260.7 m$^{3}$ s$^{-1}$ and 775.5 mgL$^{-1}$ with maximum discharge and SS flux in the month of July. The air temperature showed significant relationship with the river discharge ($R^{2}$= 0.67; n = 156; p <0.001), which in turn controlled the SS export in the basin ($R^{2}$ =0.86; n = 130; p <0.001). An anticlockwise sediment-discharge hysteresis during peak flow conditions suggest exhausted sediments or large distance of sediment transport (>100 km) from the upper glacierized region to the end of the basin. Statistical analysis of SS particle size showed poorly sorted immature grains with a dominance of silt particles (85%), followed by sand (8.5%) and clay (6.5%). The SS estimates revealed a total suspended sediment yield of 1285 tons km$^{-2}$ yr$^{-1}$ and physical erosion rate of 0.47 mm yr$^{-1}$. Considering the socio-economic importance of the Himalayan region, the present study will help to evaluate the water and sediment budget of the Chandra River, Western Himalaya and to establish their relationship to the meteorological conditions in the basin.

$\bf{Highlights}$

$\bullet$The total water discharge and suspended sediment flux during ablation period (May–September 2017) in the Chandra River were 3536 MCM and 3 million tons.

$\bullet$Overall, the suspended sediment were composed of silt size particles (85%) followed by sand (8.5%) and clay size (6.5+%) particles.

$\bullet$The suspended sediment estimates revealed a total suspended sediment yield of 1285 tons km$^{3}$ yr$^{-1}$ and physical erosion rate of 0.47 mm yr$^{-1}$

$\bullet$ This study will be useful in understanding the SS cycling from the Himalayan region and to build robust models for future projections.

• # Journal of Earth System Science

Volume 131, 2022
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019