Evaluation of emission strength efficacy in simulating black carbon burden with CHIMERE: estimating wintertime radiative effect over Indo-Gangetic Plain

2020 ◽  
Author(s):  
Sanhita Ghosh ◽  
Shubha Verma ◽  
Jayanarayanan Kuttippurath
Keyword(s):  
Black Carbon ◽  
Transport Model ◽  
Indian Subcontinent ◽  
Chemical Transport ◽  
Climate Impacts ◽  
Eastern Coast ◽  
Spatial And Temporal Patterns ◽  
Gangetic Plain ◽  
Bc Aerosols ◽  
Indo Gangetic Plain

<p>Black carbon (BC) aerosols over the Indian subcontinent have been represented inadequately so-far in chemical transport models restricting the accurate assessment of BC-induced climate impacts. The divergence between simulated and measured BC concentration has specifically been reported to be large over the Indo-Gangetic Plain (IGP) during winter when a large BC burden is observed. In this study, we evaluate the BC transport simulations over the IGP in a high resolution (0.1º × 0.1º ) chemical transport model, CHIMERE. We examine the model efficiency to simulate the observed BC distribution executing five sets of simulation experiments: <em>Constrained </em>and<em> bottomup</em> (<em>Smog, Pku, Edgar, Cmip</em>) implementing respectively, the recently estimated India-based constrained BC emission and the latest bottom-up BC emissions (India-based: Smog-India, and global: Coupled Model Intercomparison Project phase 6 (CMIP6), Emission Database for Global Atmospheric Research-V4 (EDGAR-V4) and Peking University BC Inventory (PKU)). The mean BC emission flux over most of the IGP from the five emission datasets is considerably high (450–1000 kg km<sup>-2</sup> y<sup>-1</sup>) with a relatively low divergence obtained for the eastern and upper-mideastern IGP. Evaluation of BC transport simulations shows that the spatial and temporal gradient in the simulated BC concentration from the <em>Constrained </em>was equivalent to that from the <em>bottomup</em> and also to that from observations. This indicates that the spatial and temporal patterns of BC concentration are consistently simulated by the model processes. However, the efficacy to simulate BC distribution is commendable for the estimates from <em>Constrained</em> for which the lowest normalised mean bias (NMB, < 20%) is obtained in comparison to that from the <em>bottomup</em> (37–52%). 75–100% of the observed all-day (daytime) mean BC concentration is simulated most of the times (>80% of the number of stations data) for <em>Constrained</em>, whereas, this being less frequent (<50%) for the <em>Pku, Smog, Edgar</em> and poor for <em>Cmip</em>. The BC-AOD (0.04–0.08) estimated from the <em>Constrained</em> is 20–50% higher than the <em>Pku</em> and <em>Smog</em>. Three main hotspot locations comprising of a large value of BC load are identified over the eastern, mideastern, and northern IGP. Assessment of the effect of BC burden on the wintertime radiative perturbation over the IGP shows that the presence of BC aerosols in the atmosphere enhances atmospheric heating by 2–3 times more compared to that considering atmosphere without BC. Also, a net warming at the top of the atmosphere (TOA) by 10–17 W m<sup>-</sup><sup>2</sup> is noticed from the <em>Constrained</em>, with the largest value estimated in and around megacities (Kolkata and Delhi) that extends to the eastern coast. This value is higher by 10–20% than that from <em>Cmip</em> over the IGP and by 2–10% than that from <em>Smog</em> over Delhi and eastern part of the IGP.</p>

scholarly journals Wintertime direct radiative effects due to black carbon (BC) over the Indo-Gangetic Plain as modelled with new BC emission inventories in CHIMERE

2021 ◽  
Vol 21 (10) ◽  
pp. 7671-7694
Author(s):  
Sanhita Ghosh ◽  
Shubha Verma ◽  
Jayanarayanan Kuttippurath ◽  
Laurent Menut
Keyword(s):  
Black Carbon ◽  
Transport Model ◽  
Eastern Coast ◽  
Emission Inventories ◽  
Surface Cooling ◽  
Gangetic Plain ◽  
Bottom Up ◽  
Bc Aerosols ◽  
Radiative Perturbation ◽  
Indo Gangetic Plain

Abstract. To reduce the uncertainty in climatic impacts induced by black carbon (BC) from global and regional aerosol–climate model simulations, it is a foremost requirement to improve the prediction of modelled BC distribution, specifically over the regions where the atmosphere is loaded with a large amount of BC, e.g. the Indo-Gangetic Plain (IGP) in the Indian subcontinent. Here we examine the wintertime direct radiative perturbation due to BC with an efficiently modelled BC distribution over the IGP in a high-resolution (0.1∘ × 0.1∘) chemical transport model, CHIMERE, implementing new BC emission inventories. The model efficiency in simulating the observed BC distribution was assessed by executing five simulations: Constrained and bottomup (bottomup includes Smog, Cmip, Edgar, and Pku). These simulations respectively implement the recently estimated India-based observationally constrained BC emissions (Constrainedemiss) and the latest bottom-up BC emissions (India-based: Smog-India; global: Coupled Model Intercomparison Project phase 6 – CMIP6, Emission Database for Global Atmospheric Research-V4 – EDGAR-V4, and Peking University BC Inventory – PKU). The mean BC emission flux from the five BC emission inventory databases was found to be considerably high (450–1000 kg km−2 yr−1) over most of the IGP, with this being the highest (> 2500 kg km−2 yr−1) over megacities (Kolkata and Delhi). A low estimated value of the normalised mean bias (NMB) and root mean square error (RMSE) from the Constrained estimated BC concentration (NMB: < 17 %) and aerosol optical depth due to BC (BC-AOD) (NMB: 11 %) indicated that simulations with Constrainedemiss BC emissions in CHIMERE could simulate the distribution of BC pollution over the IGP more efficiently than with bottom-up emissions. The high BC pollution covering the IGP region comprised a wintertime all-day (daytime) mean BC concentration and BC-AOD respectively in the range 14–25 µg m−3 (6–8 µg m−3) and 0.04–0.08 µg m−3 from the Constrained simulation. The simulated BC concentration and BC-AOD were inferred to be primarily sensitive to the change in BC emission strength over most of the IGP (including the megacity of Kolkata), but also to the transport of BC aerosols over megacity Delhi. Five main hotspot locations were identified in and around Delhi (northern IGP), Prayagraj–Allahabad–Varanasi (central IGP), Patna–Palamu (upper, lower, and mideastern IGP), and Kolkata (eastern IGP). The wintertime direct radiative perturbation due to BC aerosols from the Constrained simulation estimated the atmospheric radiative warming (+30 to +50 W m−2) to be about 50 %–70 % larger than the surface cooling. A widespread enhancement in atmospheric radiative warming due to BC by 2–3 times and a reduction in surface cooling by 10 %–20 %, with net warming at the top of the atmosphere (TOA) of 10–15 W m−2, were noticed compared to the atmosphere without BC, for which a net cooling at the TOA was exhibited. These perturbations were the strongest around megacities (Kolkata and Delhi), extended to the eastern coast, and were inferred to be 30 %–50% lower from the bottomup than the Constrained simulation.

scholarly journals Wintertime radiative effects of black carbon (BC) over Indo-Gangetic Plain as modelled with new BC emission inventoriesin CHIMERE

2020 ◽  
Author(s):  
Sanhita Ghosh ◽  
Shubha Verma ◽  
Jayanarayanan Kuttippurath ◽  
Laurent Menut
Keyword(s):  
Black Carbon ◽  
Climate Model ◽  
Transport Model ◽  
Indian Subcontinent ◽  
Chemical Transport Model ◽  
Surface Cooling ◽  
Gangetic Plain ◽  
Bottom Up ◽  
Radiative Perturbation ◽  
Indo Gangetic Plain

Abstract. To reduce the uncertainty in the black carbon (BC) induced climatic impacts from the global and regional aerosol-climate model simulations, it is a foremost requirement to improve the prediction of modelled BC distribution. And that specifically, over the regions where the atmosphere is loaded with a large amount of BC, e.g., the Indo-Gangetic plain (IGP) in the Indian subcontinent. Here we present the wintertime radiative perturbation due to BC with an efficiently modelled BC distribution over the IGP in a high-resolution (0.1° × 0.1°) chemical transport model, CHIMERE, implementing new BC emission inventories. The model efficiency in simulating the observed BC distribution was examined executing five simulations: Constrained and bottomup (Smog, Cmip, Edgar, Pku) implementing respectively, the recently estimated India-based constrained BC emission and the latest bottom-up BC emissions (India-based: Smog-India, and global: Coupled Model Intercomparison Project phase 6 (CMIP6), Emission Database for Global Atmospheric Research-V4 (EDGAR-V4) and Peking University BC Inventory (PKU)). A low estimated value of the normalised mean bias (NMB) and root mean square error (RMSE) from Constrained estimated BC concentration (NMB: < 17 %) and aerosol optical depth due to BC (BC-AOD) (NMB: 11 %) indicated that simulation with constrained BC emissions in CHIMERE could simulate the distribution of BC pollution over the IGP more efficiently than with the bottom-up. The large BC pollution covering the IGP region comprised of wintertime all-day (daytime) monthly mean BC concentration and BC-AOD from the Constrained, respectively, in the range 14–25 (6–8) µg m−3 and 0.04–0.08, with a strong correlation between the variance in BC emission and simulated BC mass concentration or BC-AOD. Five main hotspot locations were identified in and around Delhi (northern-IGP), Prayagraj (or Allahabad)-Varanasi (central-IGP), Patna-Palamu (upper/lower mideastern-IGP), and Kolkata (eastern-IGP). The wintertime radiative perturbation due to BC aerosols from the Constrained included a wide-spread enhancement in atmospheric radiative warming by 2–3 times and a reduction in surface cooling by 10 %–20 %, with net warming at the top of atmosphere (TOA) of 10–15 W m−2, compared to the atmosphere without BC, for which, a net cooling at the TOA was, although, exhibited. These perturbations were spotted being the strongest around megacities (Kolkata and Delhi), and were inferred as 30 %–50 % lower from the bottomup than the Constrained.

scholarly journals A global 3-D CTM evaluation of black carbon in the Tibetan Plateau

2014 ◽  
Vol 14 (13) ◽  
pp. 7091-7112 ◽  
Author(s):  
C. He ◽  
Q. B. Li ◽  
K. N. Liou ◽  
J. Zhang ◽  
L. Qi ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Transport Model ◽  
The Tibetan Plateau ◽  
Emission Inventories ◽  
Chemical Transport Model ◽  
Central Plateau ◽  
Gangetic Plain ◽  
Rural Sites ◽  
Indo Gangetic Plain

Abstract. We systematically evaluate the black carbon (BC) simulations for 2006 over the Tibetan Plateau by a global 3-D chemical transport model (CTM) (GEOS-Chem) driven by GEOS-5 assimilated meteorological fields, using in situ measurements of BC in surface air, BC in snow, and BC absorption aerosol optical depth (AAOD). Using improved anthropogenic BC emission inventories for Asia that account for rapid technology renewal and energy consumption growth (Zhang et al., 2009; Lu et al., 2011) and improved global biomass burning emission inventories that account for small fires (van der Werf et al., 2010; Randerson et al., 2012), we find that model results of both BC in surface air and in snow are statistically in good agreement with observations (biases < 15%) away from urban centers. Model results capture the seasonal variations of the surface BC concentrations at rural sites in the Indo-Gangetic Plain, but the observed elevated values in winter are absent. Modeled surface-BC concentrations are within a factor of 2 of the observations at remote sites. Part of the discrepancy is explained by the deficiencies of the meteorological fields over the complex Tibetan terrain. We find that BC concentrations in snow computed from modeled BC deposition and GEOS-5 precipitation are spatiotemporally consistent with observations (r = 0.85). The computed BC concentrations in snow are a factor of 2–4 higher than the observations at several Himalayan sites because of excessive BC deposition. The BC concentrations in snow are biased low by a factor of 2 in the central plateau, which we attribute to the absence of snow aging in the CTM and strong local emissions unaccounted for in the emission inventories. Modeled BC AAOD is more than a factor of 2 lower than observations at most sites, particularly to the northwest of the plateau and along the southern slopes of the Himalayas in winter and spring, which is attributable in large part to underestimated emissions and the assumption of external mixing of BC aerosols in the model. We find that assuming a 50% increase of BC absorption associated with internal mixing reduces the bias in modeled BC AAOD by 57% in the Indo-Gangetic Plain and the northeastern plateau and to the northeast of the plateau, and by 16% along the southern slopes of the Himalayas and to the northwest of the plateau. Both surface BC concentration and AAOD are strongly sensitive to anthropogenic emissions (from China and India), while BC concentration in snow is especially responsive to the treatment of BC aerosol aging. We find that a finer model resolution (0.5° × 0.667° nested over Asia) reduces the bias in modeled surface-BC concentration from 15 to 2%. The large range and non-homogeneity of discrepancies between model results and observations of BC across the Tibetan Plateau undoubtedly undermine current assessments of the climatic and hydrological impact of BC in the region and thus warrant imperative needs for more extensive measurements of BC, including its concentration in surface air and snow, AAOD, vertical profile and deposition.

scholarly journals A global 3-D CTM evaluation of black carbon in the Tibetan Plateau

2014 ◽  
Vol 14 (6) ◽  
pp. 7305-7354
Author(s):  
C. He ◽  
Q. B. Li ◽  
K. N. Liou ◽  
J. Zhang ◽  
L. Qi ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
Transport Model ◽  
The Tibetan Plateau ◽  
Chemical Transport Model ◽  
Gangetic Plain ◽  
Remote Sites ◽  
Rural Sites ◽  
Indo Gangetic Plain ◽  
Good Agreement

Abstract. We evaluate the black carbon (BC) simulations for 2006 over the Tibetan Plateau by a global 3-D chemical transport model using surface observations of BC in surface air and in snow and BC absorption aerosol optical depth (AAOD). Using updated Asian anthropogenic BC emissions (Lu et al., 2011; Zhang et al., 2009) and global biomass burning emissions (Randerson et al., 2012; van der Werf et al., 2010), model results of both surface BC and BC in snow are statistically in good agreement with observations (biases < 15%). Model results capture the seasonal variation of surface BC concentration, but the observed wintertime high values at rural sites in the Indo-Gangetic Plain are absent in the model. Model results are in general agreement with observations (within a factor of two) at remote sites. Model simulated BC concentrations in snow are spatiotemporally consistent with observations at most sites. We find that modeled BC AAOD are significantly lower than observations to the northwest of the Plateau and along the southern slopes of the Himalayas during winter and spring, reflecting model deficiencies in emissions, topography and BC mixing state. We find that anthropogenic emissions strongly affect surface BC concentration and AAOD, while the BC aging mainly affects BC in snow over the Plateau.

Black carbon sanitary burden in the Indo-Gangetic plain: exposures, risks and mitigation

2020 ◽  
Author(s):  
Shubha Verma ◽  
Sanhita Ghosh ◽  
Olivier Boucher ◽  
Rong Wang ◽  
Laurent Menut ◽  
...  
Keyword(s):  
Black Carbon ◽  
Urban Area ◽  
Transport Model ◽  
Thermal Power ◽  
Surface Concentration ◽  
Population Exposure ◽  
Chemical Transport Model ◽  
Modeling Framework ◽  
Gangetic Plain ◽  
Indo Gangetic Plain

Abstract A large discrepancy between simulated and observed black carbon (BC) surface concentrations over the densely populated Indo-Gangetic plain (IGP) has so far limited our ability to assess the magnitude of BC sanitary impacts in terms of population exposure, morbidity, and mortality. We evaluate these impacts using an integrated modeling framework, including a successfully predicted BC surface concentration in a high-resolution chemical transport model CHIMERE with observationally-constrained BC emissions, combined with consistent health functions for BC. Population exposure to BC is noteworthy, with more than 60 million people identified living over hotspots of BC concentration (wintertime mean > 20 μg m−3). A fraction of 62% of the total cardiovascular diseases mortality (CVM) burden for the megacity is found attributable to wintertime BC exposure. The semi-urban area has 50% of the CVM burden attributable to BC exposure in the total population over the IGP. More than 400 thousand lives can potentially be saved from CVM annually, by implementing prioritized emission reduction from the combustion of domestic biofuel in the semi-urban area, and diesel oil in transportation and coal in thermal power plant and brick kiln industries in megacities.

scholarly journals MOPITT total column CO over the Indian Subcontinent: Spatial variability and long term trend

2014 ◽  
Vol XL-8 ◽  
pp. 323-327
Author(s):  
S. Srivastava
Keyword(s):  
East Coast ◽  
Indian Subcontinent ◽  
Eastern Coast ◽  
Coastal Regions ◽  
The West ◽  
Gangetic Plain ◽  
Co Concentration ◽  
Indo Gangetic Plain ◽  
Total Column ◽  
Co Concentrations

Total column carbon monoxide (CO) concentration obtained from MOPITT (Measurement Of Pollution In The Troposphere) have been analyzed over the Indian subcontinent for a period of March, 2000 to December, 2010. Average monthly variation of columnar CO is investigated over the eastern and western coasts of India (latitude > 18&deg;N). The columnar CO concentration is found to be larger over the east coast than the west coast. The higher columnar CO concentrations (2.3&ndash;2.8 x 1018 molec/cm<sup>2</sup>) occur during November to April months over both the coastal regions. The lower columnar CO concentrations (1.6&ndash;1.7 x 1018 molec/cm<sup>2</sup>) occur during July-August months over these coastal regions when air blows from the Bay of Bengal towards the east coast and from the Arabian Sea towards the west coast. The latitudinal variations of ten year averaged columnar CO are also investigated over the eastern and western coastlines of India (23.5&deg;N to 8.5&deg;N). The latitudinal gradient is stronger over the eastern coast (3.2 x 1016 molec/cm<sup>2</sup>/&deg;N) with respect to the western coast (8.6 x 1015 molec/cm<sup>2</sup>/&deg;N) due to injection of highly polluted air mass from the Indo-Gangetic Plain over the northern part of Bay of Bengal. In order to investigate the source of pollution, variation of columnar CO concentration over the 11 polluted cities situated in the Indo-Gangetic plain has been examined. Columnar CO concentrations are found to be significantly higher over the southeast Indo-Gangetic plain and show a linear decreasing tendency from southeast to northwest cities. The maximum columnar CO concentration is observed over Patna (~ 2.48 x 1018 molec/cm<sup>2</sup>) and minimum over Multan (~ 2.19 x 1018 molec/cm<sup>2</sup>). This indicates that south-eastern part of Indo-Gangetic plain is mainly contributing towards enhancement in columnar CO concentration over the eastern coast. Columnar CO concentration showed an increasing trend during 2000 to 2010 over all the 11 cities. This increasing tendency is stronger over the cities situated in the southeast part of Indo-Gangetic plain.

scholarly journals Black Carbon physical and optical properties across northern India during pre-monsoon and monsoon seasons

2019 ◽  
Author(s):  
James Brooks ◽  
Dantong Liu ◽  
James D. Allan ◽  
Paul I. Williams ◽  
Jim Haywood ◽  
...  
Keyword(s):  
Physical Properties ◽  
Black Carbon ◽  
Mixing State ◽  
Atmospheric Measurements ◽  
Core Diameter ◽  
Gangetic Plain ◽  
North West ◽  
North East ◽  
Northern India ◽  
Indo Gangetic Plain

Abstract. Black carbon (BC) is known to have major impacts on both climate and human health, so is therefore of global importance, particularly so in regions close to large populations that have strong sources. The physical properties and mixing state of black carbon containing particles are important determinants in these effects but information is often lacking, particularly in some of the most important regions of the globe. Detailed analysis into the vertical and horizontal BC optical and physical properties across northern India has been carried out using airborne in-situ measurements. The size-resolved mixing state of BC-containing particles was characterised using a single particle soot photometer (SP2). The study focusses on the Indo-Gangetic Plain during the pre-monsoon and monsoon seasons. Data presented are from the UK Facility for Airborne Atmospheric Measurements BAe-146 research aircraft that performed flights during the pre-monsoon (11th and 12th June) and monsoon (30th June to 11th July) seasons of 2016. Over the Indo-Gangetic Plain, BC mass concentrations were greater (1.95 µg/m3) compared to north-west India (1.50 µg/m3) and north-east India (0.70 µg/m3) during the pre-monsoon. Across northern India, two distinct BC modes were recorded; a mode of small BC particles (core diameter 

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).

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