scholarly journals Recent Increase in Winter Hazy Days over Central India and the Arabian Sea

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Abin Thomas ◽  
Chandan Sarangi ◽  
Vijay P. Kanawade
Keyword(s):  
Biomass Burning ◽  
Arabian Sea ◽  
Indian Subcontinent ◽  
Winter Season ◽  
Central India ◽  
Gangetic Plain ◽  
Particulate Pollution ◽  
Aerosol Loading ◽  
Recent Climate ◽  
Indo Gangetic Plain

AbstractIndian subcontinent is greatly vulnerable to air pollution, especially during the winter season. Here, we use 15 years (2003–2017) of satellite and model reanalysis datasets over India and adjoining Seas to estimate the trend in hazy days (i.e. days with high aerosol loading) during the dry winter season (November to February). The number of hazy days is increasing at the rate of ~2.6 days per year over Central India. Interestingly, this is higher than over the Indo-Gangetic Plain (~1.7 days/year), a well known global hotspot of particulate pollution. Consistent increasing trends in absorbing aerosols are also visible in the recent years. As a result, the estimated atmospheric warming trends over Central India are two-fold higher than that over Indo-Gangetic Plain. This anomalous increment in hazy days over Central India is associated with the relatively higher increase in biomass burning over the region. Moreover, the trend in aerosol loading over the Arabian Sea, which is located downwind to Central India, is also higher than that over the Bay of Bengal during the dry winter season. Our findings not only draw attention to the rapid deteriorating air quality over Central India, but also underline the significance of increasing biomass burning under the recent climate change.

Recent increase in winter hazy days over Central India

2020 ◽  
Author(s):  
Vijay Kanawade ◽  
Abin Thomas ◽  
Chandan Sarangi
Keyword(s):  
Biomass Burning ◽  
Indian Subcontinent ◽  
Winter Season ◽  
Central India ◽  
Anomalous Increase ◽  
Gangetic Plain ◽  
Aerosol Loading ◽  
Recent Climate ◽  
Absorbing Aerosols ◽  
Indo Gangetic Plain

<p>The Indian subcontinent is greatly vulnerable to air pollution, especially during the dry winter season. Here, we use 15 years (2003-2017) of satellite and model reanalysis datasets over India and adjoining Seas to estimate the trends in the number of days with high aerosol loading (i.e. hazy days) from October to February. The number of days with high aerosol loading in recent years (2013-2017) is increasing at the rate of ~2.6 days/year over Central India, which is surprisingly higher than the more polluted Indo-Gangetic Plain (~1.7 days/year).  Similar increment in absorbing aerosols is also visible in recent years.  As a result, the estimated atmospheric warming over Central India is two-fold higher than that over Indo-Gangetic Plain. This anomalous increase in hazy days over Central India is attributed to a relatively higher increase in biomass burning over this region. The number of days with high aerosol loading in recent years are also higher over the Arabian Seas, which is located downwind to Central India, as compared to the Bay of Bengal. Thus, our findings not only draw attention to deteriorating air quality over Central India but also underlines the significance of enhanced biomass burning activities under recent climate change.</p>

scholarly journals Measurement report: Regional characteristics of seasonal and long-term variations in greenhouse gases at Nainital, India, and Comilla, Bangladesh

2021 ◽  
Vol 21 (21) ◽  
pp. 16427-16452
Author(s):  
Shohei Nomura ◽  
Manish Naja ◽  
M. Kawser Ahmed ◽  
Hitoshi Mukai ◽  
Yukio Terao ◽  
...  
Keyword(s):  
Growth Rate ◽  
Greenhouse Gases ◽  
Mole Fraction ◽  
Biomass Burning ◽  
Climatic Conditions ◽  
Gangetic Plain ◽  
Air Mass ◽  
Regional Characteristics ◽  
Northern India ◽  
Indo Gangetic Plain

Abstract. Emissions of greenhouse gases (GHGs) from the Indian subcontinent have increased during the last 20 years along with rapid economic growth; however, there remains a paucity of GHG measurements for policy-relevant research. In northern India and Bangladesh, agricultural activities are considered to play an important role in GHG concentrations in the atmosphere. We performed weekly air sampling at Nainital (NTL) in northern India and Comilla (CLA) in Bangladesh from 2006 and 2012, respectively. Air samples were analyzed for dry-air gas mole fractions of CO2, CH4, CO, H2, N2O, and SF6 and carbon and oxygen isotopic ratios of CO2 (δ13C-CO2 and δ18O-CO2). Regional characteristics of these components over the Indo-Gangetic Plain are discussed compared to data from other Indian sites and Mauna Loa, Hawaii (MLO), which is representative of marine background air. We found that the CO2 mole fraction at CLA had two seasonal minima in February–March and September, corresponding to crop cultivation activities that depend on regional climatic conditions. Although NTL had only one clear minimum in September, the carbon isotopic signature suggested that photosynthetic CO2 absorption by crops cultivated in each season contributes differently to lower CO2 mole fractions at both sites. The CH4 mole fraction of NTL and CLA in August–October showed high values (i.e., sometimes over 4000 ppb at CLA), mainly due to the influence of CH4 emissions from the paddy fields. High CH4 mole fractions sustained over months at CLA were a characteristic feature on the Indo-Gangetic Plain, which were affected by both the local emission and air mass transport. The CO mole fractions at NTL were also high and showed peaks in May and October, while CLA had much higher peaks in October–March due to the influence of human activities such as emissions from biomass burning and brick production. The N2O mole fractions at NTL and CLA increased in June–August and November–February, which coincided with the application of nitrogen fertilizer and the burning of biomass such as the harvest residues and dung for domestic cooking. Based on H2 seasonal variation at both sites, it appeared that the emissions in this region were related to biomass burning in addition to production from the reaction of OH and CH4. The SF6 mole fraction was similar to that at MLO, suggesting that there were few anthropogenic SF6 emission sources in the district. The variability of the CO2 growth rate at NTL was different from the variability in the CO2 growth rate at MLO, which is more closely linked to the El Niño–Southern Oscillation (ENSO). In addition, the growth rates of the CH4 and SF6 mole fractions at NTL showed an anticorrelation with those at MLO, indicating that the frequency of southerly air masses strongly influenced these mole fractions. These findings showed that rather large regional climatic conditions considerably controlled interannual variations in GHGs, δ13C-CO2, and δ18O-CO2 through changes in precipitation and air mass.

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 Direct radiative effect by brown carbon over the Indo-Gangetic Plain

2015 ◽  
Vol 15 (22) ◽  
pp. 12731-12740 ◽  
Author(s):  
A. Arola ◽  
G. L. Schuster ◽  
M. R. A. Pitkänen ◽  
O. Dubovik ◽  
H. Kokkola ◽  
...  
Keyword(s):  
Winter Season ◽  
Carbonaceous Aerosols ◽  
Radiative Effect ◽  
Gangetic Plain ◽  
Brown Carbon ◽  
Relative Significance ◽  
Aerosol Absorption ◽  
Spectrally Resolved ◽  
First Time ◽  
Indo Gangetic Plain

Abstract. The importance of light-absorbing organic aerosols, often called brown carbon (BrC), has become evident in recent years. However, there have been relatively few measurement-based estimates for the direct radiative effect of BrC so far. In earlier studies, the AErosol RObotic NETwork (AERONET)-measured aerosol absorption optical depth (AAOD) and absorption Angstrom exponent (AAE) were exploited. However, these two pieces of information are clearly not sufficient to separate properly carbonaceous aerosols from dust, while imaginary indices of refraction would contain more and better justified information for this purpose. This is first time that the direct radiative effect (DRE) of BrC is estimated by exploiting the AERONET-retrieved imaginary indices. We estimated it for four sites in the Indo-Gangetic Plain (IGP), Karachi, Lahore, Kanpur and Gandhi College. We found a distinct seasonality, which was generally similar among all the sites, but with slightly different strengths. The monthly warming effect up to 0.5 W m−2 takes place during the spring season. On the other hand, BrC results in an overall cooling effect in the winter season, which can reach levels close to −1 W m−2. We then estimated similarly also the DRE of black carbon and total aerosol, in order to assess the relative significance of the BrC radiative effect in the radiative effects of other components. Even though BrC impact seems minor in this context, we demonstrated that it is not insignificant. Moreover, we demonstrated that it is crucial to perform spectrally resolved radiative transfer calculations to obtain good estimates for the DRE of BrC.

scholarly journals Impact of Biomass Burning Plumes on the Size-Segregated Aerosol Chemistry over an Urban Atmosphere at Indo-Gangetic Plain

2019 ◽  
Vol 19 (1) ◽  
pp. 163-180 ◽  
Author(s):  
Abhinandan Ghosh ◽  
Arindam Roy ◽  
Abhijit Chatterjee ◽  
Sanat K. Das ◽  
Sanjay K. Ghosh ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Urban Atmosphere ◽  
Aerosol Chemistry ◽  
Gangetic Plain ◽  
Indo Gangetic Plain

scholarly journals Improving regional air quality predictions in the Indo-Gangetic Plain – case study of an intensive pollution episode in November 2017

2021 ◽  
Vol 21 (4) ◽  
pp. 2837-2860 ◽  
Author(s):  
Behrooz Roozitalab ◽  
Gregory R. Carmichael ◽  
Sarath K. Guttikunda
Keyword(s):  
Air Quality ◽  
Boundary Conditions ◽  
Infrared Imaging ◽  
Central India ◽  
Aerosol Composition ◽  
Gangetic Plain ◽  
Back Trajectories ◽  
Fire Emissions ◽  
Pollution Episode ◽  
Indo Gangetic Plain

Abstract. The Indo-Gangetic Plain (IGP) experienced an intensive air pollution episode during November 2017. Weather Research and Forecasting model coupled to Chemistry (WRF-Chem), a coupled meteorology–chemistry model, was used to simulate this episode. In order to capture PM2.5 peaks, we modified input chemical boundary conditions and biomass burning emissions. The Community Atmosphere Model with Chemistry (CAM-chem) and Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) global models provided gaseous and aerosol chemical boundary conditions, respectively. We also incorporated Visible Infrared Imaging Radiometer Suite (VIIRS) active fire points to fill in missing fire emissions in the Fire INventory from NCAR (FINN) and scaled by a factor of 7 for an 8 d period. Evaluations against various observations indicated the model captured the temporal trend very well although missed the peaks on 7, 8, and 10 November. Modeled aerosol composition in Delhi showed secondary inorganic aerosols (SIAs) and secondary organic aerosols (SOAs) comprised 30 % and 27 % of total PM2.5 concentration, respectively, during November, with a modeled OC/BC ratio of 2.72. Back trajectories showed agricultural fires in Punjab were the major source for extremely polluted days in Delhi. Furthermore, high concentrations above the boundary layers in vertical profiles suggested either the plume rise in the model released the emissions too high or the model did not mix the smoke down fast enough. Results also showed long-range-transported dust did not affect Delhi's air quality during the episode. Spatial plots showed averaged aerosol optical depth (AOD) of 0.58 (±0.4) over November. The model AODs were biased high over central India and low over the eastern IGP, indicating improving emissions in the eastern IGP can significantly improve the air quality predictions. We also found high ozone concentrations over the domain, which indicates ozone should be considered in future air quality management strategies alongside particulate matter.

scholarly journals Organic molecular tracers in the atmospheric aerosols from Lumbini, Nepal, in the northern Indo-Gangetic Plain: Influence of biomass burning

2017 ◽  
Author(s):  
Xin Wan ◽  
Shichang Kang ◽  
Quanlian Li ◽  
Dipesh Rupakheti ◽  
Qianggong Zhang ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Vanillic Acid ◽  
Monsoon Season ◽  
Syringic Acid ◽  
Rural Site ◽  
Aerosol Composition ◽  
Gangetic Plain ◽  
Post Monsoon ◽  
Post Monsoon Season ◽  
Indo Gangetic Plain

Abstract. To better understand the characteristics of biomass burning in the northern Indo-Gangetic Plain (IGP), total suspended particles were collected in a rural site, Lumbini, Nepal during April 2013 to March 2014 and analyzed for the biomass burning tracers (i.e., levoglucosan, mannosan, vanillic acid, etc.). The annual average concentration of levoglucosan was 734 ± 1043 ng m−3 with the maximum seasonal mean concentration during post-monsoon season (2206 ± 1753 ng m−3), followed by winter (1161 ± 1347 ng m−3), pre-monsoon (771 ± 524 ng m−3) and minimum concentration during monsoon season (212 ± 279 ng m−3). The other biomass burning tracers (mannosan, galactosan, p-hydroxybenzoic acid, vanillic acid, syringic acid, and dehydroabietic acid) also showed the similar seasonal variations. There were good correlations among levoglucosan, organic carbon (OC) and elemental carbon (EC), indicating significant impact of biomass burning activities on carbonaceous aerosol loading throughout the year in Lumbini area. According to the characteristic ratios: levoglucosan / mannosan (Lev / Man) and syringic acid / vanillic acid (Syr / Van), we deduced that the high abundances of biomass burning products during non-monsoon seasons were mainly caused by the burning of crop residues and hardwood while the softwood had less contribution. Based on the diagnostic tracer ratio (i.e., Lev / OC), the OC derived from biomass burning constituted large fraction of total OC, especially during post-monsoon season. By analyzing the MODIS fire spot product and five-day air-mass back trajectories, we further demonstrated that organic aerosol composition was not only related to the local agricultural activities and residential biomass usage, but was also impacted by the regional emissions. During the post-monsoon season, the emissions from rice residue burning in western India and eastern Pakistan could impact particulate air pollution in Lumbini and surrounding regions in southern Nepal. Therefore, our finding is meaningful and has a great importance for adopting the appropriate mitigation measures, not only at the local level but also by involving different regions and nations, to reduce the biomass burning emissions in the broader IGP region nations.

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