Browsing by Author "D.S. Bisht"

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Aerosol characteristics at a rural station in southern peninsular India during CAIPEEX-IGOC: physical and chemical properties
(Springer Verlag, 2015) D.S. Bisht; A.K. Srivastava; A.S. Pipal; M.K. Srivastava; A.K. Pandey; S. Tiwari; G. Pandithurai
To understand the boundary layer characteristics and pathways of aerosol–cloud interaction, an Integrated Ground Observational Campaign, concurrent with Cloud Aerosol Interaction and Precipitation Enhancement Experiment, was conducted by the Indian Institute of Tropical Meteorology, Pune, under Ministry of Earth Sciences at Mahabubnagar (a rural environment, which is ~100 km away from an urban city Hyderabad in Andhra Pradesh), during the period of July–November 2011. Collected samples of PM2.5 and PM10 were analyzed for water-soluble ionic species along with organic carbon (OC) and elemental carbon (EC). During study period, the average mass concentrations of PM2.5 and PM10 were about 50(±10) and 69(±14) μg m−3, respectively, which are significantly higher than the prescribed Indian National Ambient Air Quality Standards values. The chemical species such as sum of anions and cations from measured chemical constituents were contributed to be 31.27 and 38.49 % in PM2.5 and 6.35 and 5.65 % to the PM10, whereas carbonaceous species contributed ~17.3 and 20.47 % for OC and ~3.0 and 3.10 % for EC, respectively. The average ratio of PM2.5/PM10 during study period was ~0.73(±0.2), indicating that the dominance of fine size particles. Carbonaceous analysis results showed that the average concentration of OC was 14 and 8.7 μg m−3, while EC was 2.1 and 1.5 μg m−3 for PM10 and PM2.5, respectively. The ratios between OC and EC were estimated, which were 6.6 and 5.7 for PM10 and PM2.5, suggesting the presence of secondary organic aerosol. Total carbonaceous aerosol accounts 23 % of PM10 in which the contribution of OC is 20 % and EC is 3 %, while 20 % of PM2.5 mass in which the contribution of OC is 17 % and EC is 3 %. Out of the total aerosols mass, water-soluble constituents contributed an average of 45 % in PM10 and 38 % in PM2.5 including about 39 % anions and 6 % cations in PM10, while 31 % anions and 7 % cations in PM2.5 aerosol mass collectively at study site. © 2014, Springer-Verlag Berlin Heidelberg.
Aerosol optical properties and their relationship with meteorological parameters during wintertime in Delhi, India
(Elsevier Ltd, 2015) S. Tiwari; G. Pandithurai; S.D. Attri; A.K. Srivastava; V.K. Soni; D.S. Bisht; V. Anil Kumar; Manoj K. Srivastava
In situ and columnar measurements of aerosol optical properties (AOPs) [Aerosol optical depth (AOD), Angstrom Exponent (AE), Aerosol scattering (σscat) and absorption (σabs) coefficients and single scattering albedo (SSA)] along with soot particles (Black carbon: BC) and fine particles (PM2.5: d ≤2.5) were continuously measured at an urban site in Delhi, India during winter period (December 2011 to March 2012). Average values of AOD, σscat, σabs, and SSA at 500nm; and AE for the observation period were found to be 0.95±0.32, 1027.36±797.1Mm-1, 85.95±73.2Mm-1 and 0.93±0.03; and 0.94±0.19, respectively. Higher values of σscat and σabs were occurred in the month of December (1857 and 148Mm-1) while relatively lower values of σscat (585Mm-1) and σabs (44Mm-1) were occurred in March and February respectively. SSA, however, was higher during January (0.94) and lower in March (0.89). The mass concentration of PM2.5 and BC were 195.34±157.99 and 10.11±8.83μgm-3 respectively during study period. Bimodal distributions were observed in σscat and σabs coefficients during 0800 and 0900h LT (traffic rush hours) and at 2200 and 2300h LT (low boundary layer conditions) with lower values during daytime between 1500 and 1700h LT, respectively. The σscat peak in morning may be attributed to large emissions of aerosol in the traffic rush hours and production of secondary aerosols with increasing solar radiation and temperature. During study period, the σscat (mean) coefficient was 13% lower during daytime as compared to nighttime. An interesting feature was seen in monthly analysis of σscat in between day and nighttime which was 18% and 22% higher in December and January in nighttime however ~4% lower during February and March; it is due to effect of local meteorology. The impact of meteorological parameters such as wind speed (WS), wind direction (WD), visibility (VIS) and mixed layer depths (MLDs) on AOPs along with fine and soot particles were studied. A clear negative significant correlation between atmospheric visibility with σscat (-0.64); σabs (-0.57) and PM2.5 (-0.56) were observed. During foggy days (VIS ≤1000m), the AOPs, fine and soot particles were substantially (~1.8 times) higher as compared to clean days, however, it was ~2.3 times higher during dense foggy days (VIS ≤500m). Similarly higher (~2 times) AOPs and aerosol concentrations were also seen below 200m MLDs. In addition to this, ~4 times higher AOPs and aerosol mass concentrations were observed when WS was below 1m/s. In view of the above results and regression analysis, we can say that the meteorological parameters play a crucial role in enhancement of aerosols at ground level during winter period over Delhi. © 2014 Elsevier B.V.
Assessment of air quality during 19th Common Wealth Games at Delhi, India
(Kluwer Academic Publishers, 2013) D.S. Bisht; S. Tiwari; A.K. Srivastava; Manoj K. Srivastava
The 19th Common Wealth Games was organized at Delhi, India, during October 3 to 14, 2010, where more than 8,000 athletes from 71 Commonwealth Nations have participated. In order to give them better environment information for proper preparedness, mass concentrations of particulate matters below 10 microns (PM10) and 2. 5 microns (PM2. 5), black carbon (BC) particles and gaseous pollutants such as carbon monoxide (CO) and nitrogen oxide (NO) were monitored and displayed online for ten different locations around Delhi, including inside and outside the stadiums. This extensive information system for air quality has been set up for the period from September 24 to October 21, 2010, and data have been archived at 5-min interval for further research. During the study period, average concentration of PM10 and PM2. 5 was observed to be 229. 7 ± 85. 5 and 112. 1 ± 56. 0 μg m-3, respectively, which is far in excess of the corresponding annual averages, stipulated by the national ambient air quality standards. Significant large and positive correlation (r = 0. 93) between PM10 and PM2. 5 implies that variations in PM10 mass are governed by the variations in PM2. 5 mass. The mass concentrations of PM2. 5 inside the stadium were found to be ~18 % lower than those outside; however, no large variations were observed in PM10. Mean concentrations of BC, CO and NO for the observation period were 10. 9 μg m-3 (Min, 02 μg m-3; Max, 31 μg m-3), 1. 83 ± 0. 89 ppm (Min, 0. 48 ppm; Max, 4. 55 ppm) and 37. 82 ppb (Min, 2. 4 ppb; Max, 206. 05 ppb), respectively. BC showed positive correlation (r = 0. 73) with CO suggests unified source for both of them, mainly from combustion emissions. All the measured parameters, however, show a significant diurnal variation with enhanced peaks in the morning and late night hours and lower values during daytime. © 2012 Springer Science+Business Media B.V.
Characterization of carbonaceous aerosols over Delhi in Ganga basin: Seasonal variability and possible sources
(Springer Verlag, 2014) A.K. Srivastava; D.S. Bisht; K. Ram; S. Tiwari; Manoj K. Srivastava
The mass concentration of carbonaceous species, organic carbon (OC), and elemental carbon (EC) using a semicontinuous thermo-optical EC-OC analyzer, and black carbon (BC) using an Aethalometer were measured simultaneously at an urban mega city Delhi in Ganga basin from January 2011 to May 2012. The concentrations of OC, EC, and BC exhibit seasonal variability, and their concentrations were ~2 times higher during winter (OC 38.1 ± 17.9 μg m-3, EC 15.8 ± 7.3 μg m-3, and BC 10.1 ± 5.3 μg m-3) compared to those in summer (OC 14.1 ± 4.3 μg m-3, EC 7.5 ± 1.5 μg m-3, and BC 4.9 ± 1.5 μg m-3). A significant correlation between OC and EC (R = 0.95, n = 232) indicate their common emission sources with relatively lower OC/EC ratio (range 1.0-3.6, mean 2.2 ± 0.5) suggests fossil fuel emission as a major source of carbonaceous aerosols over the station. On average, mass concentration of EC was found to be ~38 % higher than BC during the study period. The measured absorption coefficient (babs) was significantly correlated with EC, suggesting EC as a major absorbing species in ambient aerosols at Delhi. Furthermore, the estimated mass absorption efficiency (σabs) values are similar during winter (5.0 ± 1.5 m2 g-1) and summer (4.8 ± 2.8 m2 g-1). Significantly high aerosol loading of carbonaceous species emphasize an urgent need to focus on air quality management and proper impact assessment on health perspective in these regions. © 2014 Springer-Verlag Berlin Heidelberg.
Diurnal and seasonal variations of black carbon and PM2.5 over New Delhi, India: Influence of meteorology
(2013) S. Tiwari; A.K. Srivastava; D.S. Bisht; P. Parmita; Manoj K. Srivastava; S.D. Attri
Black carbon (BC), which is one of the highly absorbing capacities of solar radiation, reduces albedo of atmospheric aerosol. BC along with fine particulate matters (PM2.5), which play crucial role in climate and health, was monitored online for an entire year of 2011 at an urban megacity of Delhi, situated in the northern part of India. Daily mass concentration of BC varies from 0.9 to 25.5μgm-3, with an annual mean of 6.7±5.7μgm-3 displayed clear monsoon minima and winter maxima; however, PM2.5 concentration was ranging from 54.3 to 338.7μgm-3, with an annual mean of 122.3±90.7μgm-3. BC typically peaked between 0800 and 1000 LST and again between 2100 and 2300 LST, corresponding to the morning and evening traffic combined with the ambient meteorological effect. During summer and monsoon, the BC concentrations were found less than 5μgm-3; however, the highest concentrations occurred during winter in segments from <5 to >10μgm-3. In over all study, the BC mass concentration was accounted for ~6% of the total PM2.5 mass, with a range from 1.0% to 14.3%. The relationship between meteorological parameters and BC mass concentrations was studied and a clear inverse relationship (r=-0.53) between BC and wind speed was observed. Relation between visibility and BC mass concentrations was also significantly negative (-0.81), having relatively higher correlation during post-monsoon (-0.85) and winter (-0.78) periods and lower during summer (-0.45) and monsoon (-0.54) periods. The mixed layer depths (MLDs) were found to be shallower during post monsoon (379m) and winter (335m) as compared during summer (1023m) and monsoon (603m). The study indicated that during post-monsoon season, the impact of biomass burning is higher as compared to combustion of fossil fuels. Results are well associated with the rapid growth of anthropogenic emissions and ambient meteorological conditions over the station. © 2013 Elsevier B.V.
High concentration of acidic species in rainwater at Varanasi in the Indo-Gangetic Plains, India
(Kluwer Academic Publishers, 2015) D.S. Bisht; S. Tiwari; A.K. Srivastava; J.V. Singh; B.P. Singh; M.K. Srivastava
The Indo-Gangetic Plains (IGP), straddling the northeastern parts of India near the foothills of the Himalayas, are one of the most densely populated and polluted regions on the globe, with consequent large anthropogenic emissions. In particular, the use of traditional biofuels in the rural areas along the plains leads to strong emissions of various pollutants. Due to this importance, a comprehensive study on the chemical characteristics of rainwater was carried out during southwest summer monsoon season of 2009 at two different locations over Varanasi, India, located in the middle of IGP region in the eastern part of Uttar Pradesh. The rainwater samples were analyzed for major chemical constituents along with pH and its electric conductivity. The pH values ranged from 5.18 to 7.08 with a mean of 5.82 ± 0.45 suggest the alkaline nature of rainwater over Varanasi. During the study period, ~14 % rainwater samples were found to be acidic when the winds blew from south–southeast direction. The weighted mean pH and electric conductivity were found higher (5.92 ± 0.45) and (24.59 µS/cm) at Maldahiya site than Banaras Hindu University (5.89 ± 0.46) and (17.16 µS/cm) due to dominance of soil-derived particles. The equivalent concentration of ionic species is of the order: Ca2+ > SO4 2− > NO3 − > Cl− > Mg2+ > Na+ > HCO3 − > NH4 + > K+ > F− > H+. The weighted mean concentration of dominant ions in rainwater over Varanasi was Ca2+ (67.1 ± 56 µeq/l), SO4 2− (37 ± 23 µeq/l) and NO3 − (27.1 ± 28 µeq/l). Significant correlation (r = 0.81; P < 0.001) between the sum of major cations (NH4 + + Ca2+ + Mg2+) and the sum of acidic species (SO4 2− + NO3 −) corroborates that these alkaline species may act as a neutralizing agent for the acidity of rainwater. The source contribution of SO4 2− in rainwater was estimated and was ~95 % by man-made activities, which is mainly derived from burning of fossil/biofuels over this region. The source of nitrate (11 %) emissions was mainly from automobiles and biomass burning. Statistical analysis such as principle component analysis was performed to find out possible sources of measured ions. First factor accounted for ~54 % variance suggested that most of the ions were from natural sources especially soil dust and sea; however, factor 2 accounted only for ~12 % variance suggests their sources from burning of fossil fuel and biomass. The third factor also indicates the mixed sources into the atmosphere. © 2014, Springer Science+Business Media Dordrecht.
Impacts of the high loadings of primary and secondary aerosols on light extinction at Delhi during wintertime
(Elsevier Ltd, 2014) S. Tiwari; A.K. Srivastava; D.M. Chate; P.D. Safai; D.S. Bisht; M.K. Srivastava; G. Beig
High emissions of anthropogenic aerosols over Indo-Gangetic Plain (IGP) inspired continuous measurements of fine particles (PM2.5), carbonaceous aerosols (BC, OC and EC), oxides of nitrogen (NOx) and estimation of light extinction (bext) and absorption (babs) coefficients over Delhi during high pollution season in winter from December 2011 to March 2012. During study period, the mass concentrations of PM2.5, BC and NOx were 186.5±149.7μgm-3, 9.6±8.5μgm-3 and 23.8±16.1ppb, respectively. The mass concentrations of OC and EC were studied by two different techniques (i) off-line (gravimetric method) and (ii) semi-continuous (optical method) and their mean mass concentrations were 51.1±15.2, 10.4±5.5μgm-3 and 33.8±27.7, 8.2±6.2μgm-3, respectively during the study period. The ratios of mass concentration of OC to EC in both cases were in between 4 and 5. The source contribution of carbonaceous aerosols in PM2.5 estimated over 24hrs, during day- and night-time where motor vehicles accounted for ~69%, 90% and 61% whereas coal combustion accounted for ~31%, 10% and 39%, respectively. The estimated mean values of bext and babs over the station were 700.0±268.6 and 71.7±54.6Mm-1, respectively. In day and night analysis, bext is ~37% higher during night-time (863.4Mm-1) than in day-time (544.5Mm-1). Regression analysis between bext and visibility showed significant negative correlation (r=-0.85). The largest contribution in the light extinction coefficients was found to be due to organic carbon (~46%), followed by elemental carbon (~24%), coarse mode particles (~18%), ammonium sulfate (~8%) and ammonium nitrate (~4%). The individual analysis of light extinction due to chemical species and coarse mode particles indicates that scattering type aerosols dominated by ~76% over the absorbing type. The aforementioned results suggest that the policy-induced control measures at local administration level are needed to mitigate the excess emissions of carbonaceous aerosols over IGP region which ranks highest in India and elsewhere in worldwide. © 2014.
Implications of different aerosol species to direct radiative forcing and atmospheric heating rate
(Elsevier Ltd, 2020) A.K. Srivastava; Bharat Ji Mehrotra; Abhishek Singh; V. Singh; D.S. Bisht; S. Tiwari; Manoj K. Srivastava
The optical and radiative characteristics of water-soluble and carbonaceous aerosol species in the PM2.5 samples were examined for a representative megacity over the Indo-Gangetic Basin (IGB). Aerosol optical and radiative transfer models were used to extract sulphate (SO4), nitrate (NO3), organic carbon (OC) and elemental carbon (EC) from the observations done in 2012. Initial results suggest that the mass concentration of OC dominated over other species, but impacts on optical characteristics were mostly due to the SO4 aerosols. Further, EC shows relatively large impact on radiative forcing. The aerosol optical depth (AOD) at 500 nm for SO4, NO3, EC and OC was found to be contributing ~36%, 20%, 27% and 9%, respectively in the total AOD value (0.61 ± 0.18) during the entire study period. The single scattering albedo (SSA) for SO4 and NO3 was high and suggested their scattering nature; however, being the highly absorbing species, EC was found to show the lowest values of SSA during the study period. SSA for OC was, however, ~0.70, which was found to show the second highest warming species in the atmosphere with contribution of ~10%, after EC, which caused the highest warming (~70%), to the total atmospheric forcing. © 2020 Elsevier Ltd
Intra-seasonal variability of black carbon aerosols over a coal field area at Dhanbad, India
(Elsevier Ltd, 2015) S. Singh; S. Tiwari; D.P. Gond; U.C. Dumka; D.S. Bisht; Shani Tiwari; G. Pandithurai; A. Sinha
Black carbon (BC) aerosols, which are optically absorbing parts of carbonaceous aerosols and have significantly different optical and radiative properties were continuously measured at a coal field area in Dhanbad (23° 47' N, 86° 30' E: 222m amsl), India for the first time from 1st January to 31st December, 2012. Daily BC mass concentrations varied within the range of 0.84-17.0μgm-3 with an annual average of 6.3±2.7μgm-3. About 45% of samples of the measured days exceeded the mean level of BC indicating the high loading of soot particles over the study region. Intra-seasonal variation in BC concentrations exhibited a strong seasonal cycle with the highest concentrations during winter (8.2±2.8μgm-3), followed by post-monsoon (6.4±2.6μgm-3), pre-monsoon (5.5±1.9μgm-3) and monsoon (4.6±1.7μgm-3). In diurnal analysis, BC showed a significant peak from 06:00 to 10:00 local time (LT) during all the seasons whereas the lowest concentrations were found during 14:00 to 17:00 LT in the late afternoon. The difference between maximum and minimum concentrations of BC was found to be higher during winter (8.3μgm-3) followed by post-monsoon (4.7μgm-3), pre-monsoon (4.3μgm-3) and monsoon (1.7μgm-3). An interesting feature was seen in the difference between morning and evening peaks, it was maximum during winter (4.8μgm-3) followed by pre-monsoon (1.5μgm-3) and post-monsoon (1.3μgm-3), however, during monsoon, it was opposite i.e. ~23% lower during morning time. During day-time and night-time variability analyses, it fluctuated largely, varying from 1% (December) to 35% (June) higher during night-time as compared to day-time as whole mean was ~19%. Data of BC were separated as stable (<1ms-1) and unstable weather conditions (>1ms-1), the corresponding values of BC were 6.06 and 3.75μgm-3 respectively which is ~38% higher during stable weather condition indicating that the major portion of BC was mainly emitted from local sources instead of transported from remote sources. Apart from this, it was observed that the concentration of BC mass during winter was ~78% higher (8.2μgm-3) as compared to monsoon (4.6μgm-3) when the winds were from the SE (158°) direction. © 2015 Elsevier B.V.
Long-term (2005–2012) measurements of near-surface air pollutants at an urban location in the Indo-Gangetic Basin
(Springer, 2019) N. Kishore; A.K. Srivastava; Hemwati Nandan; Chhavi P Pandey; S. Agrawal; N. Singh; V.K. Soni; D.S. Bisht; S. Tiwari; Manoj K Srivastava
Simultaneous long-term measurements of near-surface air pollutants at an urban station, New Delhi, were studied during 2005–2012 to understand their distribution on different temporal scales. The annual mean mass concentrations of nitrogen dioxide (NO 2) , sulphur dioxide (SO 2) , particulate matter less than 10μm (PM 10) and suspended particulate matter (SPM) were found to be 62.0±27.6, 12.5±8.2, 253.7±134 and 529.2±213.1μg/m3, respectively. The 24-hr mean mass concentrations of NO 2, PM 10 and SPM were exceeded on ∼ 27%, 87% and 99% days that of total available measurement days to their respective National Ambient Air Quality Standard (NAAQS) level. However, it never exceeded for SO 2, which could be attributed to reduction of sulphur in diesel, use of cleaner fuels such as compressed natural gas, LPG, etc. The mean mass concentrations of measured air pollutants were found to be the highest during the winter/post-monsoon seasons, which are of concern for both climate and human health. The annual mean mass concentrations of NO 2, PM 10 and SPM showed an increasing trend while SO 2 appears to be decreasing since 2008. Air mass cluster analysis showed that north–northwest trajectories accounted for the highest mass concentrations of air pollutants (more prominent in the winter/post-monsoon season); however, the lowest were associated with the southeast trajectory cluster. © 2019, Indian Academy of Sciences.
Pre-monsoon aerosol characteristics over the Indo-Gangetic Basin: Implications to climatic impact
(Copernicus GmbH, 2011) A.K. Srivastava; S. Tiwari; P.C.S. Devara; D.S. Bisht; Manoj K. Srivastava; S.N. Tripathi; P. Goloub; B.N. Holben
Sun/sky radiometer observations over the Indo-Gangetic Basin (IGB) region during pre-monsoon (from April-June 2009) have been processed to analyze various aerosol characteristics in the central and eastern IGB region, represented by Kanpur and Gandhi College, respectively, and their impacts on climate in terms of radiative forcing. Monthly mean aerosol optical depth (AOD at 500 nm) and corresponding Angstrom Exponent (AE at 440-870 nm, given within the brackets) was observed to be about 0.50 (0.49) and 0.51 (0.65) in April, 0.65 (0.74) and 0.67 (0.91) in May and 0.69 (0.45) and 0.77 (0.71) in June at Kanpur and Gandhi College, respectively. Results show a positive gradient in AOD and AE from central to eastern IGB region with the advancement of the pre-monsoon, which may be caused due to diverse geographical location of the stations having different meteorological conditions and emission sources. Relatively lower SSA was observed at the eastern IGB (0.89) than the central IGB (0.92) region during the period, which suggests relative dominance of absorbing aerosols at the eastern IGB as compared to central IGB region. The absorbing aerosol optical properties over the station suggest that the atmospheric absorption over central IGB region is mainly due to dominance of coarse-mode dust particles; however, absorption over eastern IGB region is mainly due to dominance of fine-particle pollution. The derived properties from sun/sky radiometer during pre-monsoon period are used in a radiative-transfer model to estimate aerosol radiative forcing at the top-of-the atmosphere (TOA) and at the surface over the IGB region. Relatively large TOA and surface cooling was observed at the eastern IGB as compared to the central IGB region. This translates into large heating of the atmosphere ranging from 0.45 to 0.55 K day-1 at Kanpur and from 0.45 to 0.59 K day-1 at Gandhi College. © Author(s) 2011.
Predicting the rapid intensification and dynamics of pre-monsoon extremely severe cyclonic storm ‘Fani’ (2019) over the Bay of Bengal in a 12-km global model
(Elsevier Ltd, 2021) Vivek Singh; Rakesh Teja Konduru; Atul Kumar Srivastava; I.M. Momin; Sushant Kumar; Abhay Kumar Singh; D.S. Bisht; Suresh Tiwari; Abhay Kumar Sinha
The present study investigates into genesis, intensification, dynamical behavior and the prediction of Extremely Severe Cyclonic Storm (ESCS) ‘Fani' over the Bay of Bengal (BoB) in the National Centre for Medium-Range Weather Forecasting (NCMRWF) global numerical weather prediction (NWP) modeling system ‘NCUM.’ The global model is adopted from the UK Met office's Unified Model (UM). The ESCS ‘Fani' formed from 26 April–04 May 2019, over the warm waters of BoB. In the criterion of landfalling tropical cyclones (TCs), which crossed the Orissa coast, it was the most intense cyclonic storm during pre-monsoon season since 1965. The TC exhibited a markedly different characteristic having genesis very near to the equator (near 2.7°N and 88.7°E) and possessing one of the longest tracks (~3030-km) over the BoB region. The NCUM global model was operationally run during the occurrence of the TC. The diagnosis of the TC's genesis and rapid intensification (RI) in the model is carried out using various metrics such as Genesis potential parameter (GPP), winds at 850-hPa, vertically integrated moisture flux, potential vorticity (PV) at isentropic level 315 K, Severe Weather Threat (SWEAT) index and daily averaged latent heat flux, etc. It is found that the early genesis, structure, RI, and movement of the TC were well captured by the model in advance. The Model predicted TC tracks for a total of seven initial conditions (from 27 April to 03 May 2019, at 24-h interval) are found closely co-related with the observed best track of the TC provided by India Meteorological Department (IMD). The lower values of Direct Position Errors (DPEs), along-track errors (ATEs), and cross-track errors (CTEs) indicate the skillful prediction of the TC by the model. The structure, amplitude, and location (SAL) simulated precipitation of the TC over the BoB and along the central-east coast of India are in agreement with the observed systems. Our detailed diagnostic analysis suggests that the TC formation, development, and intensification was mostly controlled by the warmer BoB sea surface temperatures. © 2020 Elsevier B.V.
Radiative impact of fireworks at a tropical Indian location: A case study
(2014) B.P. Singh; A.K. Srivastava; S. Tiwari; S. Singh; R.K. Singh; D.S. Bisht; D.M. Lal; A.K. Singh; R.K. Mall; Manoj K. Srivastava
During Diwali festival, extensive burning of crackers and fireworks is made. Weeklong intensive observational campaign for aerosol study was carried out at a representative urban location in the eastern Indo-Gangetic Plain (IGP), Varanasi (25.3°N, 83.0°E), from October 29 to November 04, 2005 (Diwali on November 01, 2005), to investigate behavioral change of aerosol properties and radiative forcing between firework affected and nonaffected periods. Results show a substantial increase (27%) in aerosol optical depth, aerosol absorption coefficients, and aerosol scattering coefficients during affected period as compared to non-affected periods. Magnitudes of radiative forcing at top of atmosphere during affected and non-affected periods are found to be +10 ± 1 and +12 ± 1 Wm-2, respectively, which are -31 ± 7 and -17 ± 5 Wm-2, respectively, at surface. It suggests an additional cooling of 20% at top of atmosphere, 45% cooling at surface, and additional atmospheric heating of 0.23 Kday-1 during fireworks affected period, which is 30% higher than the non-affected period average. © 2014 B. P. Singh et al.
Rainwater chemistry in the North Western Himalayan Region, India
(Elsevier Ltd, 2012) S. Tiwari; D.M. Chate; D.S. Bisht; M.K. Srivastava; B. Padmanabhamurty
Precipitation chemistry studies were conducted at Kothi (32.31°N, 77.20°E), a rural Indian location, in the North Western Himalayas during June to October of 2006 and 2007. The volume weighted mean pH values ranged from 5.16 to 6.36 with a mean of 5.68±0.26 indicating mostly alkaline precipitation events. However, 18% samples were found acidic due to dominance of acidic components. The alkaline to acidic ions ratio (1.05) confirms that acidic components are neutralized by alkali radicals in rainwater. Of the total ionic composition 159μeq/l, in rainwater samples, dominant were Ca2+ (19%) followed by Na+ (14%). Among the anions, Cl- (17%) was slightly higher than SO42- (16%) and NO3- (11%). The ratio (NO3-+Cl-)/SO42-) 1.05 indicates acidity in rainwater by the cumulative effects of HNO3, H2SO4 and HCl. The ratios NH4+/NO3- as 0.76 and NH4+/SO42- as 0.50 show the pre-dominance of atmospheric NH4NO3 and (NH4)2SO4. Significant correlation between Na+ and Cl- (r=0.97; p<0.0001) and between SO42- and NO3- (r=0.60; p<0.0001) indicates their origin from similar sources. Neutralization factor calculations show that Ca2+ plays a major role in the neutralizing processes. Enrichment factors indicate that Ca2+, SO42- K+ and Mg2+ were originated from non-marine sources. The principle component analysis indicates the influence of transportation of air-born primary and secondary particles on the chemical composition of rainwater. © 2011 Elsevier B.V.
Seasonal inhomogeneity of soot particles over the central indo-gangetic plains, India: Influence of meteorology
(Chinese Meteorological Society, 2015) B.P. Singh; S. Tiwari; Philip K. Hopke; R.S. Singh; D.S. Bisht; A.K. Srivastava; R.K. Singh; U.C. Dumka; A.K. Singh; B.N. Rai; Manoj K. Srivastava
Black carbon (BC) particles play a unique and important role in earth’s climate system. BC was measured (in-situ) in the central part of the Indo-Gangetic Plains (IGP) at Varanasi, which is a highly populated and polluted region due to its topography and extensive emission sources. The annual mean BC mass concentration was 8.92 ± 7.0 μg m−3, with 34% of samples exceeding the average value. Seasonally, BC was highest during the post-monsoon and winter periods (approximately 18 μg m−3) and lower in the premonsoon/ monsoon seasons (approximately 6 μg m−3). The highest frequency (approximately 46%) observed for BC mass was in the interval from 5 to 10 μg m−3. However, during the post-monsoon season, the most common values (approximately 23%) were between 20 and 25 μg m−3. The nighttime concentrations of BC were approximately twice as much as the daytime values because of lower boundary layer heights at nighttime. The Ångström exponent was significantly positively correlated (0.55) with ground-level BC concentrations, indicating the impact of BC on the columnar aerosol properties. The estimated mean absorption Ångström exponent was 1.02 ± 0.08 μg m−3, indicating that the major source of BC was from fossil fuel combustion. Significant negative correlations between BC mass and meteorological parameters indicate a pronounced effect of atmospheric dynamics on the BC mass in this region. The highest mean BC mass concentration (18.1 ± 6.9 μg m−3) as a function of wind speed was under calm wind conditions (38% of the time). © The Chinese Meteorological Society and Springer-Verlag Berlin Heidelberg 2015.
Sources and characteristics of carbonaceous aerosols at Agra "World heritage site" and Delhi "capital city of India"
(Springer Verlag, 2014) A.S. Pipal; S. Tiwari; P.G. Satsangi; Ajay Taneja; D.S. Bisht; A.K. Srivastava; M.K. Srivastava
Agra, one of the oldest cities "World Heritage site", and Delhi, the capital city of India are both located in the border of Indo-Gangetic Plains (IGP) and heavily loaded with atmospheric aerosols due to tourist place, anthropogenic activities, and its topography, respectively. Therefore, there is need for monitoring of atmospheric aerosols to perceive the scenario and effects of particles over northern part of India. The present study was carried out at Agra (AGR) as well as Delhi (DEL) during winter period from November 2011 to February 2012 of fine particulate (PM2.5: d < 2.5 μm) as well as associated carbonaceous aerosols. PM2.5 was collected at both places using medium volume air sampler (offline measurement) and analyzed for organic carbon (OC) and elemental carbon (EC). Also, simultaneously, black carbon (BC) was measured (online) at DEL. The average mass concentration of PM2.5 was 165.42 ± 119.46 μg m-3 at AGR while at DEL it was 211.67 ± 41.94 μg m-3 which is ~27 % higher at DEL than AGR whereas the BC mass concentration was 10.60 μg m-3. The PM2.5 was substantially higher than the annual standard stipulated by central pollution control board and United States Environmental Protection Agency standards. The average concentrations of OC and EC were 69.96 ± 34.42 and 9.53 ± 7.27 μm m-3, respectively. Total carbon (TC) was 79.01 ± 38.98 μg m-3 at AGR, while it was 50.11 ± 11.93 (OC), 10.67 ± 3.56 μg m-3 (EC), and 60.78 ± 14.56 μg m-3 (TC) at DEL. The OC/EC ratio was 13.75 at (AGR) and 5.45 at (DEL). The higher OC/EC ratio at Agra indicates that the formation of secondary organic aerosol which emitted from variable primary sources. Significant correlation between PM2.5 and its carbonaceous species were observed indicating similarity in sources at both sites. The average concentrations of secondary organic carbon (SOC) and primary organic carbon (POC) at AGR were 48.16 and 26.52 μg m-3 while at DEL it was 38.78 and 27.55 μg m-3, respectively. In the case of POC, similar concentrations were observed at both places but in the case of SOC higher over AGR by 24 in comparison to DEL, it is due to the high concentration of OC over AGR. Secondary organic aerosol (SOA) was 42 % higher at AGR than DEL which confirms the formation of secondary aerosol at AGR due to rural environment with higher concentrations of coarse mode particles. The SOA contribution in PM2.5 was also estimated and was ~32 and 12 % at AGR and DEL respectively. Being high loading of fine particles along with carbonaceous aerosol, it is suggested to take necessary and immediate action in mitigation of the emission of carbonaceous aerosol in the northern part of India. © 2014 Springer-Verlag Berlin Heidelberg.
Statistical evaluation of PM10 and distribution of PM1, PM2.5, and PM10 in ambient air due to extreme fireworks episodes (Deepawali festivals) in megacity Delhi
(Kluwer Academic Publishers, 2012) S. Tiwari; D.M. Chate; M.K. Srivastava; P.D. Safai; A.K. Srivastava; D.S. Bisht; B. Padmanabhamurty
Temporal variation of PM10 using 2-year data (January, 2007-December, 2008) of Delhi is presented. PM10 varied from 42 to 200 μg m-3 over January to December, with an average 114. 1 ± 81. 1 μg m-3. They are comparable with the data collected by Central Pollution Control Board (National Agency which monitors data over the entire country in India) and are lower than National Ambient Air Quality (NAAQ) standard during monsoon, close to NAAQ during summer but higher in winter. Among CO, NO2, SO2, rainfall, temperature, and wind speed, PM10 shows good correlation with CO. Also, PM10, PM2. 5, and PM1 levels on Deepawali days when fireworks were displayed are presented. In these festive days, PM10, PM2. 5, and PM1 levels were 723, 588, and 536 μg m-3 in 2007 and 501, 389, and 346 μg m-3 in 2008. PM10, PM2. 5, and PM1 levels in 2008 were 1. 5 times lower than those in 2007 probably due to higher mixing height (446 m), temperature (23. 8°C), and winds (0. 36 ms-1). © 2011 Springer Science+Business Media B.V.
Study of the carbonaceous aerosol and morphological analysis of fine particles along with their mixing state in Delhi, India: A case study
(Springer Verlag, 2015) S. Tiwari; A.S. Pipal; Philip K. Hopke; D.S. Bisht; A.K. Srivastava; Shani Tiwari; P.N. Saxena; A.H. Khan; S. Pervez
Because of high emissions of anthropogenic as well as natural particles over the Indo-Gangetic Plains (IGP), it is important to study the characteristics of fine (PM2.5) and inhalable particles (PM10), including their morphology, physical and chemical characteristics, etc., in Delhi during winter 2013. The mean mass concentrations of fine (PM2.5) and inhalable (PM10) (continuous) was 117.6±79.1 and 191.0± 127.6 μg m−3, respectively, whereas the coarse mode (PM10–2.5) particle PM mass was 73.38±28.5 μg m−3. During the same period, offline gravimetric monitoring of PM2.5 was conducted for morphological analysis, and its concentration was ~37% higher compared to the continuous measurement. Carbonaceous PM such as organic carbon (OC) and elemental carbon (EC) were analyzed on the collected filters, and their mean concentration was respectively 33.8 and 4.0 μg m−3 during the daytime, while at night it was 41.2 and 10.1 μg m−3, respectively. The average OC/EC ratio was 8.97 and 3.96 during the day and night, respectively, indicating the formation of secondary organic aerosols during daytime. Effective carbon ratio was studied to see the effect of aerosols on climate, and its mean value was 0.52 and 1.79 during night and day, indicating the dominance of absorbing and scattering types of aerosols respectively into the atmosphere over the study region. Elemental analysis of individual particles indicates that Si is the most abundant element (~37–90%), followed by O (oxide) and Al. Circularity and aspect ratio was studied, which indicates that particles are not perfectly spherical and not elongated in any direction. Trajectory analysis indicated that in the months of February and March, air masses appear to be transported from the Middle Eastern part along with neighboring countries and over Thar Desert region, while in January it was from the northeast direction which resulted in high concentrations of fine particles. © Springer-Verlag Berlin Heidelberg 2015.
Variability in atmospheric particulates and meteorological effects on their mass concentrations over Delhi, India
(Elsevier BV, 2014) S. Tiwari; D.S. Bisht; A.K. Srivastava; A.S. Pipal; A. Taneja; M.K. Srivastava; S.D. Attri
Simultaneous and continuous measurements of PM2.5 and PM10 along with other co-existent pollutants viz., black carbon (BC), CO, NO and NOx were carried out over Delhi with high resolution (5min) datasets from 1st Sept. 2010 to 23rd Aug. 2012. Arithmetic mean mass concentrations of PM2.5 and PM10 were about 130±103 and 222±142μgm-3 respectively during the entire measurement period, which are considerably higher than the annual averages of PM2.5 and PM10, stipulated by the National and International standards. It was noticed that the fine mode particles (PM2.5) were higher than the coarse mode particles (PM10-2.5) during post-monsoon (~89%), winter (~69%) and monsoon (~64%) periods; however, PM10-2.5 was higher (~22%) than PM2.5 during summer. Arithmetic mean mass concentrations of BC, CO, NO and NOx were about 7±5μgm-3, 2±1ppm, 17±17ppb and 30±24ppb, respectively. In the present study, highest fraction of BC (~6%) in PM2.5 mass was in winter, whereas the lowest fraction (~4%) was in summer. Relationships among PMs (particulate matters) and other pollutants indicated that the fine mode particles are highly correlated with BC (0.74) and CO (0.51). The effects of meteorological parameters on aerosols have been studied and a significant negative relationship (-0.45) between mixing height (MH) and PM2.5 has been noticed. Higher correlation was during winter (-0.55), however lower was in summer (-0.16). Relation between visibility (VIS) and PM2.5 was higher during post-monsoon (-0.85) and winter (-0.78) when the visibility was around 2km; however, it was relatively less correlated when VIS was greater than 2km during summer and monsoon. Relationship between PM2.5 and relative humidity (RH) showed a significant negative correlation (-0.56) for the entire study period. A positive correlation (0.32) was observed during the winter period with fine mode particles whereas negative correlation was seen with coarse mode particles during monsoon (-0.70) and summer (-0.51). © 2014.