Soumyajyoti Jana

Abstract: Near surface aerosol black carbon (BC) concentration data were collected using a seven channel Aethalometer (AE31) during June 2012–May 2013 in Kolkata (22° 34′E, 88° 22′N), a metropolitan city located near the land–ocean boundary in Eastern India. BC concentration shows a prominent seasonal and diurnal variation associated with the meteorological parameters. The mean BC concentration varied from 5 μg/m 3 to 27 μg/m 3 seasonally. The variation of BC mass concentration and its significant association with atmospheric parameters such as temperature profile, relative humidity and wind speed have been studied. Moreover, the influence of the transported air masses on BC concentration at different seasons has also been discussed. An estimation of Angstrom exponent discloses that fossil fuel combustion is a major source of BC at this location.

Abstract: Atmospheric pollutants (NO2, SO2, PM10, BC, CO, surface O3), emitted during fireworks display, have significant effects on meteorological parameters like air temperature, relative humidity, lapse rate and visibility in air over Kolkata (22°65′ N, 88°45′ E), a metropolitan city near the land–ocean boundary, on the eve of Deepawali festival when extensive fireworks are burnt. Long-term trend (2005–2013), indicates that the yearly average concentrations of both primary and secondary air pollutants have increased, exceeding the National Ambient Air Quality Standard (NAAQS) limit, on the respective Deepawali days. Short-term study (2012–2013) during the festival shows that the average pollutant concentrations have increased too compared to normal days. This study also reveals the immediate effects of the increased air pollutants on the boundary layer meteorology. PM10 has been found to be the most dominant atmospheric pollutants during this period. As a result of an increase in atmospheric heat content with elevated surface air temperature, a significant increase in the environmental lapse rate bears a signature of the influence of pollutants on the boundary layer temperature profile. A change in the diurnal pattern of relative humidity as well as in the vertical temperature profile is due to the change of the lapse rate during the festival days. Thus, the atmospheric pollutants during this festival over the urban region have significant effect on the boundary layer meteorology with bearings on environmental hazards.

Abstract: Summary Nowcasting of heavy rain events using microwave radiometer has been carried out at Kolkata (22.65°N, 88.45°E), a tropical location. Microwave radiometer can produce the temperature and humidity profiles of the atmosphere with fairly good accuracy. Definite changes are observed in temperature and humidity profiles before and at the onset of heavy rain events. Concurrent changes in the brightness temperatures (BT) at 22 GHz and 58 GHz are found to be suitable to nowcast rain. The time derivatives of brightness temperatures at 22 GHz and 58 GHz are used as inputs to the proposed nowcasting model. In addition, the standard deviation of the product of these time derivatives is also considered. The model has been developed using the data of 2011 and validated for rain events of 2012–2013 showing a prediction efficiency of about 90% with alarm generated about 25 min in advance.

Abstract: The effects of the convective rain on various atmospheric parameters have been investigated at Kolkata (22.57°N, 88.37°E), India, during pre-monsoon and monsoon period of 2013. Various parameters like cloud base height and depth, liquid water content, rain rate and rain drop size distribution (DSD) are observed concurrently. The atmospheric electric field measured with an electric field monitor and the attenuation and depolarisation of satellite signals measured by a Ku-band receiving system are also studied during rain events. The instability indices obtained from radiometric measurements and the rain height profiles from micro rain radar are used to classify rain into two types, namely, convective and stratiform. The signatures of rain events on multi-technique observations are studied to indicate the various aspects of convective processes at a tropical location.

Abstract: Two years of aerosol spectral light absorption measurements, using filter based technique, from the central Indo-Gangetic plain (IGP), Gorakhpur (26.75°N, 83.38°E, 85 m amsl), are analyzed to study their seasonal behavior and to quantify their magnitude in terms of absorbing aerosols loading and source speciation. Spectral absorption analysis reveals a four-fold enhancement in absorption in winter (W) and post-monsoon (PoM) seasons at UV wavelengths as compared to IR wavelengths on account of increased biomass burning aerosol contribution to total absorbing aerosol load. Aerosols from the biomass sources contribute ~ 28% during W and PoM seasons as against ~ 16% in pre-monsoon (PM) and monsoon (M) seasons to the total absorbing aerosol content. A Mode shift in the distribution of the Absorption Angstrom exponent (α) from 1.3 to 1.6 from PM-M seasons to PoM-W seasons signifies change in source type of absorbing aerosols from fossil fuel to biomass burning and their relative source strength. Due to near stagnant wind conditions combined with shallow boundary layer height, where air masses travelling to the central IGP are confined to a smaller volume, in W and PoM seasons, local sources assume more prominence rather than long-range transport of aerosols. Long-term measurements of aerosols physicochemical and radiative properties from this measurement location will enhance our understanding of the complex aerosol system over the IGP and its climatic implications.

Abstract: India is currently the second-largest emitter of black carbon (BC) in the world, with emissions projected to rise steadily in the coming decades. In view of the large variations associated with BC emission inventories in this region, model outputs of BC mass and radiative forcing (RF) need to be validated against long-term regionally-representative atmospheric measurements. Such measurements are highly scattered spatially as well as temporally in India, and a systematic evaluation of BC data is non-existent so far. To address this issue, we present here a comprehensive review of BC measurements in India from a survey of >140 studies spanning 2002–2018. In addition to summarizing baseline BC levels in urban, semi-urban, rural and remote locations, we report impacts of anomalous environmental and/or emission conditions, e.g., truck/general strikes, firework events, fog/haze episodes, large-scale biomass burning events, etc. We also present a discussion on major BC sources and climate impacts (in terms of direct RF) in major land-use categories, mitigation strategies currently employed on a national scale, and recent advances in measuring brown carbon (BrC) in India. We identify key areas for improvement, such as – i) the need for long-term BC monitoring networks, especially in regions where estimated emissions are high but measurement coverage is low; ii) the general lack of understanding, despite some recent reports, of BC aerosol mixing states, aging and direct climate effects in the Indian context; iii) the need to shift from qualitative approaches of BC source apportionment to robust quantitative measures; and iv) the prospects for coupled chemical-optical characterization of BrC for a better understanding of its sources and climate effects. We list potential research directions for the scientific community to address these knowledge gaps. We also believe that this review will be beneficial to policymakers for prioritizing BC mitigation efforts.

Abstract: We present the systematic analysis of individual black carbon (BC) mixing state and its impact on radiative forcing from an urban Indian city, Kanpur, located in Indo-Gangetic Plain (IGP). Simultaneous measurements using Single Particle Soot Photometer (SP2), Photo-Acoustic Soot Spectrometer (PASS-3) and High-Resolution Time-of-Flight Aerosol Mass Spectrometer (AMS) were conducted from 8 January 2015 to 28 February 2015 at Kanpur. BC mass and number concentrations varied between 0.7 and 17 μg/m 3 and 277–5866 #/cm 3 with a mean of 4.06 μg/m 3 and 1314 #/cm 3 , respectively. The diurnal variation of BC mass concentration showed a traffic hour peak during both the morning and late night. The mean fraction of “thickly coated BC” particles (fTC BC ) was found to be 61.6%, indicating that a large fraction of BC particles was internally mixed. The fTC BC increased after sunrise with a peak at about noontime, indicating that the formation of secondary organic aerosol under active photochemistry can enhance organic coating on a core of black carbon. High-resolution positive matrix factorization (HR-PMF) factors showed distinct characteristics with fTC BC . While primary organic aerosols like cooking organic aerosols (COA) and biomass burning organic aerosols (BBOA) were negatively correlated with fTC BC (r = − 0.78 and − 0.51, respectively), aged low volatile oxygenated organic aerosol (LVOOA) was forming a coating over BC (r = 0.6). Similar positive correlation of fTC BC with inorganic species like ammonium (r = 0.58) and nitrate (r = 0.47) further suggested that BC appears to be largely coated with LVOOA, ammonium, and nitrate. A positive correlation between the fTC BC and the mass absorption cross-section at 781 nm (MAC 781 ) was also observed (r = 0.58). Our results suggest that the observed fTC BC could amplify the MAC 781 approximately by a factor of 1.8, which may catalyze the positive radiative forcing in the IGP.

Abstract: Emission factor is a relative measure and can be used to estimate emissions from multiple sources of air pollution For this reason, data from literature on particulate matter emission factors from different types of biomass were evaluated in this paper Initially, the main sources of particles were described, as well as relevant concepts associated with particle measurements In addition, articles about particle emissions were classified and described in relation to the sampling environment (open or closed) and type of burned biomass (agricultural, garden, forest, and dung) Based on this analysis, a set of emission factors was presented and discussed Important observations were made about the main emission sources of particulate matter Combustion of compacted biomass resulted in lower particulate emission factors PM25 emissions were predominant in the burning of forest biomass Emission factors were more elevated in laboratory burning, followed by burns in the field, residences and combustors