Browsing by Author "Suresh Tiwari"

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Aerosol characteristics during the coolest june month over new delhi, northern india
(Taylor and Francis Ltd., 2011) Atul Kumar; Suresh Tiwari; Deewan Singh Bisht; Panuganti China Sattilingam Devara; Philippe Goloub; Zhengqiang Li; Manoj K. Srivastava
June 2008, which is also the transition month between two major seasons for Indo-Gangetic Basin (IGB), has been identified the coolest June over New Delhi during the past century, showing mean temperature of 31.6 ± 1.7°C, which was found to be ~2°C less than its climatological mean (33.9°C). Aerosol optical properties for this month and thus obtained physical parameters have been studied using data from the CIMEL sun/sky radiometer, installed in New Delhi under the Aerosol Robotic Network (AERONET) programme. Results reveal bimodal aerosol volume size distribution. The monthly mean values for aerosol optical depth (AOD) at 500 nm (0.96 ± 0.31) and Ångström exponent at the wavelength pair of 440-870 nm (0.79 ± 0.42) show significant lower values whereas single scattering albedo at 675 nm shows a significantly larger value (0.94 ± 0.04) compared with previous measurements over the station. Results suggest dominance of scattering- type particles such as water-soluble aerosols from anthropogenic sources and dust aerosols from natural sources with higher relative humidity over the station. Radiative forcing caused due to the aerosols for the month of June 2008, which have been computed using the radiative-transfer model, informs low forcing at the top of atmosphere (TOA, +14 W -m) as well as at surface (-33 W m-2). The resultant atmospheric forcing (+47 W m-2) indicates warming effect that caused heating of lower atmosphere at the rate of 0.89 K day-1. © 2011 Taylor & Francis.
Aerosol chemistry over a high altitude station at northeastern Himalayas, India
(2010) Abhijit Chatterjee; Anandamay Adak; Ajay K. Singh; Manoj K. Srivastava; Sanjay K. Ghosh; Suresh Tiwari; Panuganti C. S. Devara; Sibaji Raha
Background: There is an urgent need for an improved understanding of the sources, distributions and properties of atmospheric aerosol in order to control the atmospheric pollution over northeastern Himalayas where rising anthropogenic interferences from rapid urbanization and development is becoming an increasing concern. Methodology/Principal Findings: An extensive aerosol sampling program was conducted in Darjeeling (altitude~2200 meter above sea level (masl), latitude 27°01'N and longitude 88°15'E), a high altitude station in northeastern Himalayas, during January-December 2005. Samples were collected using a respirable dust sampler and a fine dust sampler simultaneously. Ion chromatograph was used to analyze the water soluble ionic species of aerosol. The average concentrations of fine and coarse mode aerosol were found to be 29.5±20.8 μg m-3 and 19.6±11.1 μg m-3 respectively. Fine mode aerosol dominated during dry seasons and coarse mode aerosol dominated during monsoon. Nitrate existed as NH4NO3 in fine mode aerosol during winter and as NaNO3 in coarse mode aerosol during monsoon. Gas phase photochemical oxidation of SO2 during premonsoon and aqueous phase oxidation during winter and postmonsoon were the major pathways for the formation of SO42- in the atmosphere. Long range transport of dust aerosol from arid regions of western India was observed during premonsoon. The acidity of fine mode aerosol was higher in dry seasons compared to monsoon whereas the coarse mode acidity was higher in monsoon compared to dry seasons. Biomass burning, vehicular emissions and dust particles were the major types of aerosol from local and continental regions whereas sea salt particles were the major types of aerosol from marine source regions. Conclusions/Significance: The year-long data presented in this paper provide substantial improvements to the heretofore poor knowledge regarding aerosol chemistry over northeastern Himalayas, and should be useful to policy makers in making control strategies. © 2010 Chatterjee et al.
Black carbon and chemical characteristics of PM10 and PM 2.5 at an urban site of North India
(2009) Suresh Tiwari; Atul K. Srivastava; Deewan S. Bisht; Tarannum Bano; Sachchidanand Singh; Sudhamayee Behura; Manoj K. Srivastava; D.M. Chate; B. Padmanabhamurty
The concentrations of PM10, PM2.5 and their water-soluble ionic species were determined for the samples collected during January to December, 2007 at New Delhi (28.63° N, 77.18° E), India. The annual mean PM10 and PM2.5 concentrations (± standard deviation) were about 219 (± 84) and 97 (±56) μgm -3 respectively, about twice the prescribed Indian National Ambient Air Quality Standards values. The monthly average ratio of PM 2.5/PM10 varied between 0.18 (June) and 0.86 (February) with an annual mean of ∼0.48 (±0.2), suggesting the dominance of coarser in summer and fine size particles in winter. The difference between the concentrations of PM10 and PM2.5, is deemed as the contribution of the coarse fraction (PM10-2.5). The analyzed coarse fractions mainly composed of secondary inorganic aerosols species (16.0 μgm-3, 13.07%), mineral matter (12.32 μgm-3, 10.06%) and salt particles (4.92 μgm-3, 4.02%). PM2.5 are mainly made up of undetermined fractions (39.46 μgm-3, 40.9%), secondary inorganic aerosols (26.15 μgm-3, 27.1%), salt aerosols (22.48 μgm-3, 23.3%) and mineral matter (8.41 μgm-3, 8.7%). The black carbon aerosols concentrations measured at a nearby (∼300 m) location to aerosol sampling site, registered an annual mean of ∼14 (±12) μgm-3, which is significantly large compared to those observed at other locations in India. The source identifications are made for the ionic species in PM10 and PM2.5. The results are discussed by way of correlations and factor analyses. The significant correlations of Cl-, SO 4 2-, K+, Na+, Ca2+, NO 3 - and Mg 2+ with PM2.5 on one hand and Mg2+ with PM 10 on the other suggest the dominance of anthropogenic and soil origin aerosols in Delhi. © 2010 Springer Science+Business Media B.V.
Characterization and radiative impact of dust aerosols over northwestern part of India: a case study during a severe dust storm
(Springer-Verlag Wien, 2016) Atinderpal Singh; Shani Tiwari; Deepti Sharma; Darshan Singh; Suresh Tiwari; Atul Kumar Srivastava; Neeraj Rastogi; A.K. Singh
The present study focused on examining the impact of a severe dust storm (DS) on aerosol properties over Patiala (30.33°N, 76.4°E), a site located in the northwestern part of India during 20th–23rd March, 2012. On 20th March, average PM10 mass concentration increased abruptly from 182 to 817 µg m−3 along with significant increase in the number density of coarser particles (diameter >0.45 µm). During DS, spectral aerosol optical depth (AOD) increases significantly with more increase at longer wavelengths resulting in weak wavelength dependence (AOD at 380 nm increases by ~210 % and at 870 nm by ~270 % on 20th March). Significant decrease in Ångström exponent (AE; α380–870) from 0.56 to 0.11 and fine-mode fraction (FMF; PM2.5/PM10) from 0.49 to 0.25 indicates dominance of coarser particles over the station. Net short wave (SW) radiation flux has been decreased by ~20 % and single scattering albedo (SSA675) has been increased from 0.86 (19th March) to 0.90 (20th March). This observation is attributed to additional loading of scattering type aerosols on arrival of DS. Wavelength dependence of SSA reverses during DS and it increases with wavelength due to dominance of coarse-mode particles. Atmospheric aerosol radiative forcing (ATM ARF) during DS ranged from +45 to +77 W m−2, consequently heating the lower atmosphere up to 2.2 K day−1. Significant atmospheric heating rate due to severe dust storm may affect the regional atmospheric dynamics and hence the climate system. © 2016, Springer-Verlag Wien.
Intra-urban variability of particulate matter (PM2.5 and PM10) and its relationship with optical properties of aerosols over Delhi, India
(Elsevier Ltd, 2015) Suresh Tiwari; Philip K. Hopke; Atar S. Pipal; Atul K. Srivastava; Deewan S. Bisht; Shani Tiwari; Abhay K. Singh; Vijay K. Soni; Shiv D. Attri
Highly time-resolved measurements of particulate matter (PM: PM2.5 and PM10) were made at three different sites across Delhi (CCRI: a highly traffic site, IMD: a less traffic site and IITM: an urban background site) from 1st December, 2011 to 30th June, 2013. Also, coarse mode (PM10-2.5) mass was estimated as the difference between PM10 and PM2.5. In addition, columnar aerosol optical properties such as aerosol optical depth (AOD) and Angstrom exponent (AE) were studied concurrently over IMD. The mean mass concentrations of PM2.5, PM10-2.5 and PM10 were 118.3±81.7, 113.6±70.4 and 232.1±131.1μgm-3, respectively. Among the three sites, relatively higher mass concentrations of PM2.5 (~35% and 3%) were observed at CRRI compared to IMD and IITM.PM10 and PM10-2.5 were higher at these sites by ~31% and 19%; and 27% and 40%, respectively, compared to CRRI. Coefficients of divergence (COD) and correlation coefficients (r) were calculated between site pairs to assess the spatial and temporal heterogeneity of PM and moderate spatial divergence was found over the three sites. Traffic emission particles (PM2.5) exhibited high spatial heterogeneity as well. The mass concentrations of PM2.5 and PM10 were found to be higher during the night compared to the day. The mean PM2.5/PM10 ratio was ~51%, indicating generally equal amounts of coarse and fine mode PM in the Delhi urban atmosphere. AOD and PM2.5 were positively correlated and a negative correlation was observed between AE and PM10-2.5. PM2.5 particles were significantly correlated with AOD during post-monsoon and winter. Because of the lower vehicular emissions on weekends compared to weekdays, PM at CRRI, IMD, and IITM were separated by day of week and large heterogeneities were found. During weekdays, the mass concentrations of PM10 were ~4, 2, and 12% higher than on weekends. However, for PM2.5, weekend values were 5, 7, and 9% higher for CRRI, IMD and IITM, respectively. © 2015 Elsevier B.V.
Nature and sources of ionic species in precipitation across the indo-gangetic plains, India
(AAGR Aerosol and Air Quality Research, 2016) Suresh Tiwari; Philip K. Hopke; Devraj Thimmaiah; Umesh C. Dumka; Atui K. Srivastava; Deewan S. Bisht; Pasumarti S.P. Rao; Dilip M. Chate; Manoj K. Srivastava; Sachchida N. Tripathi
The spatial distribution of rainwater chemistry over the densely-populated and highly polluted Indo-Gangetic Plains (IGP) was investigated using samples (total = 687) collected during three consecutive summer monsoon seasons from 2009 to 2011. The concentrations of secondary ionic species (SO42– and NO3–) were measured along with the other major ions (F–, Cl–, Na+, K+, Ca2+, Mg2+ and NH4+) and pH and specific conductivity. The weighted mean pH (± std) and conductivity of rainwater were 5.73 (± 0.17) and 31.6 (± 31.0) µS cm–1, respectively. Approximately 16% of rainwater samples were acidic (pH < 5.61) with a mean pH = 5.38 of acid rain and rest of them were more alkaline (pH > 5.61) (mean pH = 6.34 for the more basic samples). Specific conductivity was ~39% lower (20.6 µS cm–1) for the acidic rain compared to the more basic (33.6 µS cm–1) samples. The mean sum of all of the measured ions is 351.6 ± 130.1 µeq L–1 with the highest contributions being Ca2+ (30%) and SO42– (15%). Mean [SO42–] (52 µeq L–1) and [NO3–] (29 µeq L–1) were approximately five and ten times higher, respectively, compared to background hemispheric values. Secondary ions had the highest deposition fluxes (SO42–, 25.2 kg ha–1 y–1 and NO3–: 18.3 kg ha–1 y–1). The mean ratio of H+/(NO3– + SO42–) was 0.02 indicating ~98% of the acidity was neutralized. Ca2+, (57%), Mg2 (25%), NH4+ (15%) and K+ (4%) were important neutralizing species. Positive Matrix Factorization (PMF) was applied to the deposition fluxes. Five factors were identified and identified as ammonia neutralized, sea salt, soil, biomass burning, and calcium neutralized. © Taiwan Association for Aerosol Research.
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.
Variability in optical properties of atmospheric aerosols and their frequency distribution over a mega city “New Delhi,” India
(Springer Verlag, 2016) S. Tiwari; Suresh Tiwari; P.K. Hopke; S.D. Attri; V.K. Soni; Abhay Kumar Singh
The role of atmospheric aerosols in climate and climate change is one of the largest uncertainties in understanding the present climate and in capability to predict future climate change. Due to this, the study of optical properties of atmospheric aerosols over a mega city “New Delhi” which is highly polluted and populated were conducted for two years long to see the aerosol loading and its seasonal variability using sun/sky radiometer data. Relatively higher mean aerosol optical depth (AOD) (0.90 ± 0.38) at 500 nm and associated Angstrom exponent (AE) (0.82 ± 0.35) for a pair of wavelength 400–870 nm is observed during the study period indicating highly turbid atmosphere throughout the year. Maximum AOD value is observed in the months of June and November while minimum is in transition months March and September. Apart from this, highest value of AOD (AE) value is observed in the post-monsoon [1.00 ± 0.42 (1.02 ± 0.16)] season followed by the winter [0.95 ± 0.36 (1.02 ± 0.20)] attributed to significance contribution of urban as well as biomass/crop residue burning aerosol which is further confirmed by aerosol type discrimination based on AOD vs AE. During the pre-monsoon season, mostly dust and mixed types aerosols are dominated. AODs value at shorter wavelength observed maximum in June and November while at longer wavelength maximum AOD is observed in June only. For the better understanding of seasonal aerosol modification process, the aerosol curvature effect is studied which show a strong seasonal dependency under a high turbid atmosphere, which are mainly associated with various emission sources. Five days air mass back trajectories were computed. They suggest different patterns of particle transport during the different seasons. Results suggest that mixtures of aerosols are present in the urban environment, which affect the regional air quality as well as climate. The present study will be very much useful to the modeler for validation of satellite data with observed data during estimation of radiative effect. © 2016, Springer-Verlag Berlin Heidelberg.