scholarly journals Deposition of light-absorbing particles in glacier snow of the Sunderdhunga Valley, the southern forefront of Central Himalaya

2020 ◽  
Author(s):  
Jonas Svensson ◽  
Johan Ström ◽  
Henri Honkonen ◽  
Eija Asmi ◽  
Nathaniel B. Dkhar ◽  
...  
Keyword(s):  
Large Scale ◽  
Anthropogenic Activities ◽  
Central Himalaya ◽  
Snow Layer ◽  
Gangetic Plain ◽  
Central Himalayas ◽  
Indo Gangetic Plain ◽  
The Himalaya ◽  
Very High ◽  
Fractional Absorption

Abstract. Anthropogenic activities on the Indo-Gangetic Plain emit vast amounts of light-absorbing particles (LAP) into the atmosphere, modifying the atmospheric radiation scheme. With transport to the nearby Himalayan mountains and deposition to its surfaces the particles contribute to glacier and snowmelt via darkening of the highly reflective snow. The Central Himalayas have been identified as a region where LAP are especially pronounced in glacier snow, but still remain a region where measurements of LAP in the snow are scarce. Here we study the deposition of LAP in five snow pits sampled in 2016 (and one from 2015) from two glaciers in the Sunderdhunga valley, state of Uttarakhand, India, Central Himalaya. The snow pits display a distinct melt layer interleaved by younger snow above, and older snow below. The LAP exhibit a large vertical distribution in these different snow layers. For the analyzed elemental carbon (EC), the younger snow layers in the different pits show similarities, and can be characterized by a deposition constant of about 50 µg m−2 mm−1 while the old snow layers also indicate similar values, and can be described with deposition constant of roughly 150 µg m−2 mm−1. The melt layer, contrarily, display no similar trends between the pits. Instead, it is characterized by very high amounts of LAP, and differ in orders of magnitude for concentration between the pits. The melt layer is likely a result of strong melting that took place during the summers of 2015 and 2016. The mineral dust fractional absorption is slightly below 50 % for the young and old snow layer, whereas in the melt layer is the dominating light absorbing constituent, thus, highlighting the importance of dust in the region. Our results indicate the problems with complex topography in the Himalaya, but nonetheless, can be useful in large-scale assessments of LAP in Himalayan snow.

scholarly journals Deposition of light-absorbing particles in glacier snow of the Sunderdhunga Valley, the southern forefront of the central Himalayas

2021 ◽  
Vol 21 (4) ◽  
pp. 2931-2943
Author(s):  
Jonas Svensson ◽  
Johan Ström ◽  
Henri Honkanen ◽  
Eija Asmi ◽  
Nathaniel B. Dkhar ◽  
...  
Keyword(s):  
Large Scale ◽  
Elemental Carbon ◽  
Snow Water Equivalent ◽  
Anthropogenic Activities ◽  
Gangetic Plain ◽  
Central Himalayas ◽  
Snow Water ◽  
Indo Gangetic Plain ◽  
Very High ◽  
Fractional Absorption

Abstract. Anthropogenic activities on the Indo-Gangetic Plain emit vast amounts of light-absorbing particles (LAPs) into the atmosphere, modifying the atmospheric radiation state. With transport to the nearby Himalayas and deposition to its surfaces the particles contribute to glacier melt and snowmelt via darkening of the highly reflective snow. The central Himalayas have been identified as a region where LAPs are especially pronounced in glacier snow but still remain a region where measurements of LAPs in the snow are scarce. Here we study the deposition of LAPs in five snow pits sampled in 2016 (and one from 2015) within 1 km from each other from two glaciers in the Sunderdhunga Valley, in the state of Uttarakhand, India, in the central Himalayas. The snow pits display a distinct enriched LAP layer interleaved by younger snow above and older snow below. The LAPs exhibit a distinct vertical distribution in these different snow layers. For the analyzed elemental carbon (EC), the younger snow layers in the different pits show similarities, which can be characterized by a deposition constant of about 50 µg m−2 mm−1 snow water equivalent (SWE), while the old-snow layers also indicate similar values, described by a deposition constant of roughly 150 µg m−2 mm−1 SWE. The enriched LAP layer, contrarily, displays no similar trends between the pits. Instead, it is characterized by very high amounts of LAPs and differ in orders of magnitude for concentration between the pits. The enriched LAP layer is likely a result of strong melting that took place during the summers of 2015 and 2016, as well as possible lateral transport of LAPs. The mineral dust fractional absorption is slightly below 50 % for the young- and old-snow layers, whereas it is the dominating light-absorbing constituent in the enriched LAP layer, thus, highlighting the importance of dust in the region. Our results indicate the problems with complex topography in the Himalayas but, nonetheless, can be useful in large-scale assessments of LAPs in Himalayan snow.

scholarly journals Large contrast in the vertical distribution of aerosol optical properties and radiative effects across the Indo-Gangetic Plain during the SWAAMI–RAWEX campaign

2018 ◽  
Vol 18 (23) ◽  
pp. 17669-17685 ◽  
Author(s):  
Aditya Vaishya ◽  
Surendran Nair Suresh Babu ◽  
Venugopalan Jayachandran ◽  
Mukunda M. Gogoi ◽  
Naduparambil Bharathan Lakshmi ◽  
...  
Keyword(s):  
Optical Properties ◽  
Radiative Forcing ◽  
Anthropogenic Activities ◽  
Eastern Coast ◽  
Biomass Combustion ◽  
Spectral Variation ◽  
Vertical Profiles ◽  
Industrial Emissions ◽  
Gangetic Plain ◽  
Indo Gangetic Plain

Abstract. Measurements of the vertical profiles of the optical properties (namely the extinction coefficient and scattering and absorption coefficients respectively σext ∕ σscat ∕ σabs) of aerosols have been made across the Indo-Gangetic Plain (IGP) using an instrumented aircraft operated from three base stations – Jodhpur (JDR), representing the semi-arid western IGP; Varanasi (VNS), the central IGP characterized by significant anthropogenic activities; and the industrialized coastal location in the eastern end of the IGP (Bhubaneswar, BBR) – just prior to the onset of the Indian summer monsoon. The vertical profiles depicted region-specific absorption characteristics, while the scattering characteristics remained fairly uniform across the region, leading to a west–east gradient in the vertical structure of single-scattering albedo (SSA). Integrated from near the ground to 3 km, the highest absorption coefficient and hence the lowest SSA occurred in the central IGP (Varanasi). Size distribution, inferred from the spectral variation of the scattering coefficient, showed a gradual shift from coarse-particle dominance in the western IGP to strong accumulation dominance in the eastern coast with the central IGP coming in between, arising from a change in the aerosol type from a predominantly natural (dust and sea salt) type in the western IGP to a highly anthropogenic type (industrial emissions, fossil fuel and biomass combustion) in the eastern IGP, with the central IGP exhibiting a mixture of both. Aerosol-induced short-wave radiative forcing, estimated using altitude-resolved SSA information, revealed significant atmospheric warming in the central IGP, while a top-of-atmosphere cooling is seen, in general, in the IGP. Atmospheric heating rate profiles, estimated using altitude-resolved SSA and column-averaged SSA, revealed considerable underestimation in the latter case, emphasizing the importance and necessity of having altitude-resolved SSA information as against a single value for the entire column.

scholarly journals Airborne in situ measurements of aerosol size distributions and black carbon across the Indo-Gangetic Plain during SWAAMI–RAWEX

2020 ◽  
Vol 20 (14) ◽  
pp. 8593-8610 ◽  
Author(s):  
Mukunda Madhab Gogoi ◽  
Venugopalan Nair Jayachandran ◽  
Aditya Vaishya ◽  
Surendran Nair Suresh Babu ◽  
Sreedharan Krishnakumari Satheesh ◽  
...  
Keyword(s):  
Black Carbon ◽  
Mass Fraction ◽  
Aerosol Size Distribution ◽  
Size Distributions ◽  
Gangetic Plain ◽  
Airborne Measurements ◽  
Coarse Mode ◽  
Indo Gangetic Plain ◽  
Very High ◽  
Mass Concentrations

Abstract. During the combined South-West Asian Aerosol–Monsoon Interactions and Regional Aerosol Warming Experiment (SWAAMI–RAWEX), collocated airborne measurements of aerosol number–size distributions in the size (diameter) regime 0.5 to 20 µm and black carbon (BC) mass concentrations were made across the Indo-Gangetic Plain (IGP), for the first time, from three distinct locations, just prior to the onset of the Indian summer monsoon. These measurements provided an east–west transect of region-specific properties of aerosols as the environment transformed from mostly arid conditions of the western IGP (represented by Jodhpur, JDR) having dominance of natural aerosols to the central IGP (represented by Varanasi, VNS) having very high anthropogenic emissions, to the eastern IGP (represented by the coastal station Bhubaneswar, BBR) characterized by a mixture of the IGP outflow and marine aerosols. Despite these, the aerosol size distribution revealed an increase in coarse mode concentration and coarse mode mass fraction (fractional contribution to the total aerosol mass) with the increase in altitude across the entire IGP, especially above the well-mixed region. Consequently, both the mode radii and geometric mean radii of the size distributions showed an increase with altitude. However, near the surface and within the atmospheric boundary layer (ABL), the features were specific to the different subregions, with the highest coarse mode mass fraction (FMC∼72 %) in the western IGP and highest accumulation fraction in the central IGP with the eastern IGP in between. The elevated coarse mode fraction is attributed to mineral dust load arising from local production as well as due to advection from the west. This was further corroborated by data from the Cloud-Aerosol Transport System (CATS) on board the International Space Station (ISS), which also revealed that the vertical extent of dust aerosols reached as high as 5 km during this period. Mass concentrations of BC were moderate (∼1 µg m−3) with very little altitude variation up to 3.5 km, except over VNS where very high concentrations were seen near the surface and within the ABL. The BC-induced atmospheric heating rate was highest near the surface at VNS (∼0.81 K d−1), while showing an increasing pattern with altitude at BBR (∼0.35 K d−1 at the ceiling altitude).

scholarly journals Aerosol chemistry, transport and climatic implications during extreme biomass burning emissions over Indo-Gangetic Plain

2018 ◽  
Author(s):  
Nandita Singh ◽  
Tirthankar Banerjee ◽  
Made P. Raju ◽  
Karine Deboudt ◽  
Meytar Sorek-Hamer ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Radiative Forcing ◽  
Large Scale ◽  
Regional Climate ◽  
Water Soluble ◽  
Submicron Particles ◽  
Aerosol Layer ◽  
Sudden Increase ◽  
Gangetic Plain ◽  
Indo Gangetic Plain

Abstract. The large-scale emissions of airborne particulates from burning of agricultural residues particularly over the upper Indo-Gangetic Plain (IGP) have often been associated with frequent formation of haze, adverse health impacts, modification in aerosol climatology and thereby aerosols impact on regional climate. In this study, short-term variations in aerosol climatology during extreme biomass burning emissions over IGP, and thereby to regional climate were investigated. Size-segregated particulate concentration was initially measured and submicron particles (PM1.1) were found to dominate particulate mass within the fine mode (PM2.1). Particulate bound water-soluble ions were mainly secondary in nature, primarily composed of sulfate and nitrate. There was evidence of gaseous NH3 dominating neutralization of acidic aerosol species (SO42−) in submicron particles, in contrast to crustal dominating neutralization in coarser particulates. Variation in black carbon mass ratio was found to be influenced by local sources, while sudden increase in concentration was consistent with high Delta-C, referring to biogenic emissions. Influence of biomass burning emissions were established using specific organic (levoglucosan), inorganic (K+ and NH4+) and satellite (UV Aerosol Index, UVAI) tracers. Levoglucosan was the most abundant within submicron particles (649±177 ng m−3), with a very high ratio (>50) against other anhydrosugars, indicating exclusive emissions from burning of agriculture residues. Temporal variations of all the tracers were consistent, while NH4+ was more closely associated to levoglucosan. Spatio-temporal distribution of aerosol and few trace gases (CO and NO2) were evaluated using both space-borne active and passive sensors, and a significant increase in columnar aerosol loading (AOD: 0.98) was evident during extreme biomass burning emissions, with presence of absorbing aerosols (UVAI > 1.5) having low aerosol layer height (~1.5 km). A strong intraseasonality in aerosol cross-sectional altitudinal profile was even noted from CALIPSO, referring dominance of smoke and polluted continental aerosols across IGP. Possible transport mechanism of biomass smoke was established using cluster analysis and concentration weighted of air mass back-trajectories. Short-wave aerosol radiative forcing (ARF) was further simulated considering intraseasonality in aerosol properties, which resulted in considerable increase of atmospheric ARF (135 Wm−2) and heating rate (4.3 K day−1) during extreme biomass burning emissions compared to non-dominating one (56 Wm−2, 1.8 K day−1). We therefore conclude that influence of biomass burning emissions on regional aerosol climatology must need to be studied in much finer scale to improve parameterization of aerosol/-climate model across the region.

scholarly journals Natural processes dominate the pollution levels during COVID-19 lockdown over India

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Venkat Ratnam Madineni ◽  
Hari Prasad Dasari ◽  
Ramakrishna Karumuri ◽  
Yesubabu Viswanadhapalli ◽  
Prasad Perumal ◽  
...  
Keyword(s):  
South India ◽  
Anthropogenic Activities ◽  
Gangetic Plain ◽  
Pollution Levels ◽  
Natural Processes ◽  
Range Transport ◽  
Northwest India ◽  
Indo Gangetic Plain ◽  
Pollution Concentrations ◽  
Natural Laboratory

AbstractThe lockdown measures that were taken to combat the COVID-19 pandemic minimized anthropogenic activities and created natural laboratory conditions for studying air quality. Both observations and WRF-Chem simulations show a 20–50% reduction (compared to pre-lockdown and same period of previous year) in the concentrations of most aerosols and trace gases over Northwest India, the Indo Gangetic Plain (IGP), and the Northeast Indian regions. It is shown that this was mainly due to a 70–80% increase in the height of the boundary layer and the low emissions during lockdown. However, a 60–70% increase in the pollutants levels was observed over Central and South India including the Arabian sea and Bay of Bengal during this period, which is attributed to natural processes. Elevated (dust) aerosol layers are transported from the Middle East and Africa via long-range transport, and a decrease in the wind speed (20–40%) caused these aerosols to stagnate, enhancing the aerosol levels over Central and Southern India. A 40–60% increase in relative humidity further amplified aerosol concentrations. The results of this study suggest that besides emissions, natural processes including background meteorology and dynamics, play a crucial role in the pollution concentrations over the Indian sub-continent.

scholarly journals Aerosol chemistry, transport, and climatic implications during extreme biomass burning emissions over the Indo-Gangetic Plain

2018 ◽  
Vol 18 (19) ◽  
pp. 14197-14215 ◽  
Author(s):  
Nandita Singh ◽  
Tirthankar Banerjee ◽  
Made P. Raju ◽  
Karine Deboudt ◽  
Meytar Sorek-Hamer ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Radiative Forcing ◽  
Large Scale ◽  
Water Soluble ◽  
Submicron Particles ◽  
Aerosol Layer ◽  
Aerosol Chemistry ◽  
Short Term ◽  
Gangetic Plain ◽  
Indo Gangetic Plain

Abstract. The large-scale emissions of airborne particulates from burning of agricultural residues particularly over the upper Indo-Gangetic Plain (IGP) have often been associated with frequent formation of haze, adverse health impacts, and modification in aerosol climatology and thereby aerosol impact on regional climate. In this study, short-term variations in aerosol climatology during extreme biomass burning emissions over the IGP were investigated. Size-segregated particulate concentration was initially measured and submicron particles (PM1.1) were found to dominate particulate mass within the fine mode (PM2.1). Particulate-bound water-soluble ions were mainly secondary in nature and primarily composed of sulfate and nitrate. There was evidence of gaseous NH3 dominating neutralization of acidic aerosol species (SO42-) in submicron particles, in contrast to crustal-dominating neutralization in coarser particulates. Diurnal variation in black carbon (BC) mass ratio was primarily influenced by regional meteorology, while gradual increase in BC concentration was consistent with the increase in Delta-C, referring to biomass burning emissions. The influence of biomass burning emissions was established using specific organic (levoglucosan), inorganic (K+ and NH4+), and satellite-based (UV aerosol index, UVAI) tracers. Levoglucosan was the most abundant species within submicron particles (649±177 ng m−3), with a very high ratio (> 50) to other anhydrosugars, indicating exclusive emissions from burning of agriculture residues. Spatiotemporal distribution of aerosol and a few trace gases (CO and NO2) was evaluated using both spaceborne active and passive sensors. A significant increase in columnar aerosol loading (aerosol optical depth, AOD: 0.98) was evident, with the presence of absorbing aerosols (UVAI > 1.5) having low aerosol layer height (∼ 1.5 km). A strong intraseasonality in the aerosol cross-sectional altitudinal profile was even noted from CALIPSO, referring to the dominance of smoke and polluted continental aerosols across the IGP. A possible transport mechanism of biomass smoke was established using cluster analysis and concentration-weighted air mass back trajectories. Short-wave aerosol radiative forcing (ARF) was further simulated considering intraseasonality in aerosol properties, which resulted in a considerable increase in atmospheric ARF (135 W m−2) and heating rate (4.3 K day−1) during extreme biomass burning emissions compared to the non-dominating period (56 W m−2, 1.8 K day−1). Our analysis will be useful to improve understanding of short-term variation in aerosol chemistry over the IGP and to reduce uncertainties in regional aerosol–climate models.

Where does all the gravel go? Tracking landslide sediment from the 2015 Gorkha earthquake along the Kosi River, Nepal

2020 ◽  
Author(s):  
Emma Graf ◽  
Hugh Sinclair ◽  
Mikael Attal
Keyword(s):  
Large Scale ◽  
Size Fraction ◽  
Sediment Supply ◽  
Gorkha Earthquake ◽  
Gangetic Plain ◽  
Gangetic Plains ◽  
2015 Gorkha Earthquake ◽  
Channel Aggradation ◽  
The Impact ◽  
The Himalaya

<p>Rivers draining the Himalaya and feeding the Indo-Gangetic plain support around 10% of the world’s population. However, these rivers are also prone to frequent and often devastating floods such as the 2008 Kosi floods which displaced more than 2.5 million people. Changes in sediment supply from the Himalaya influence the magnitude and distribution of floods through changing capacity and routing respectively. Widespread landsliding following the 2015 Gorkha (Nepal) earthquake increased suspended sediment supply to the river network and is expected to result in some degree of coarse bedload aggradation and increased rates of channel migration at the mountain front. Given the significant amounts of channel aggradation observed in the aftermath of similar events, understanding the timescales of sediment transport following the 2015 Gorkha earthquake and the impact of any resulting sediment wave on flooding in the Gangetic plains is crucial. We track the gravel size fraction of the landslide sediment along the Kosi River (East Nepal) by mapping zones of sediment input from optical satellite imagery and constructing a time series of high-resolution channel cross-sections using an Acoustic Doppler Current Profiler (ADCP) in the years following the earthquake. We use these datasets to identify zones of channel aggradation and migrating sediment, and test whether the changes are consistent with the location of sediment sources (landslides) and magnitude of the monsoon floods with the aid of landslide inventories and flow data. While initial results show a marked increase in coarse sediment following the 2015 monsoon, we see little evidence of large-scale downstream migration of any sediment pulse, indicating the Gorkha landslides may have less of an impact on flood and sediment dynamics on the Indo-Gangetic plains than expected from comparison with similar events. We suggest that the Gorkha landslides may not be connected to the fluvial system to the same extent as for similar events and revegetated rapidly, and therefore did not release significant amounts of sediment into channels after the initial post-2015 monsoon pulse.</p>

scholarly journals A Correlation based study using air quality and meteorological parameters for the outbreak of COVID-19 on major affected districts in India

2021 ◽  
Author(s):  
Amitesh Gupta
Keyword(s):  
Air Quality ◽  
Meteorological Parameters ◽  
Virus Transmission ◽  
Quality Parameters ◽  
Eastern India ◽  
Gangetic Plain ◽  
Highly Correlated ◽  
Matter Concentration ◽  
Indo Gangetic Plain ◽  
Very High

Abstract Air quality is an important factor for human health conditions. Simultaneously, suitable meteorology poses the circumstances for virus transmission. Hence, we investigated both these two important aspects for the COVID-19 pandemic. We correlated the remote sensing based observations of meteorological parameters and air quality parameters with COVID-19 cases from 657 districts all over the country and found that air quality parameters are playing very crucial role along with a few meteorological parameters for this outbreak. We observed that air temperature, and wind speed were significantly and positively correlated with COVID-19 cases but precipitation and humidity were negatively correlated with confirmed cases. Cloudiness had no significant relation in this aspect. Among the air pollutants, O3 was better correlating with COVID-19 cases. AOD representing the particulate matter concentration also significantly correlated with such cases majorly over Indo-Gangetic plain region. The carbon-pollutants CO was also very high over the same region. Though NO2 and SO2 were reduced during lockdown, due to the power generation and mining activities both these gases were quite highly correlated over eastern India region. We noted the eastern and western coastal districts of India and districts from the low-lying plain areas had more cases during this pandemic. Our study suggests that improving air quality with proper strict regulations and complete lockdown during the peak of pandemic could reduce the misfortune in all over India. Hence, the summer season could be susceptible and might pose a gesture of seasonality for this disease.

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