Browsing by Author "S.D. Attri"

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Aerosol chemical characterization and role of carbonaceous aerosol on radiative effect over Varanasi in central Indo-Gangetic Plain
(Elsevier Ltd, 2016) S. Tiwari; U.C. Dumka; D.G. Kaskaoutis; Kirpa Ram; A.S. Panicker; M.K. Srivastava; Shani Tiwari; S.D. Attri; V.K. Soni; A.K. Pandey
This study investigates the chemical composition of PM10 aerosols at Varanasi, in the central Indo-Gangetic Plain (IGP) during April to July 2011, with emphasis on examining the contribution of elemental carbon (EC) to the estimates of direct aerosol radiative effect (DARE). PM10 samples are analysed for carbonaceous aerosols (Organic Carbon, OC and EC) and water-soluble ionic species (WSIS: Cl-, SO42-, NO3-, PO42- NH4+, Na+, K+, Mg2+ and Ca2+) and several diagnostic ratios (OC/EC, K+/EC, etc) have been also used for studying the aerosol sources at Varanasi. PM10 mass concentration varies between 53 and 310 μgm-3 (mean of 168 ± 73 μgm-3), which is much higher than the National and International air quality standards. The OC mass concentration varies from 6 μg m-3 to 24 μg m-3 (mean of 12 ± 5 μg m-3; 7% of PM10 mass), whereas EC ranges between 1.0 and 14.3 μg m-3 (4.4 ± 3.9 μg m-3; ~3% of PM10 mass). The relative low OC/EC of 3.9 ± 2.0 and strong correlation (R2 = 0.82) between them suggest the dominance of primary carbonaceous aerosols. The contribution of WSIS to PM10 is found to be ~12%, out of which ~57% and 43% are anions and cations, respectively. The composite DARE estimates via SBDART model reveal significant radiative effect and atmospheric heating rates (0.9-2.3 Kday-1). Although the EC contributes only ~3% to the PM10 mass, its contribution to the surface and atmospheric forcing is significantly high (37-63% and 54-77%, respectively), thus playing a major role in climate implications over Varanasi. © 2015 Elsevier Ltd.
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.
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 aerosol loading over mega city Delhi in the western Indo-Gangetic plain: Optical characteristics
(India Meteorological Department, 2016) S.D. Attri; V.K. Soni; S. Tiwari; A.K. Srivastava; Shani Tiwari; Kanika Taneja
Measurements of aerosol optical properties were carried out at an urban mega city Delhi, which is situated in the western Indo-Gangetic Plain (IGP) region in north India using an automatic sun/sky radiometer during 2006-2008. The present study revealed high aerosol loading over the station, which could be due to its topography surrounded by different natural and anthropogenic emission sources, and may have major implications towards health, air quality and climate system. Results show a large variability in AOD during the study period, with nearly equal values during winter (0.67 ± 0.06) and summer (0.71 ± 0.11). The Ångström exponent (AE) values were found to be relatively higher during winter (1.19 ± 0.07, suggests dominance of fine-mode aerosols) and lower during summer (0.74±0.06, suggests dominance of coarse-mode aerosols). A slight decrease in single scattering albedo (SSA) was observed during the study period, with a mean value of ~0.9. SSA was found to be about 0.93 during post-monsoon and 0.96 during the winter period whereas during summer and monsoon, SSA was about 0.95. The estimated monthly absorption Ångström exponent (AAE) values over the station varied from 0.11 to 1.87, which were found to be less than 1.0 by ~55% time (mostly during winter and monsoon), and greater than 1.0 by ~45% time (mostly during summer and post-monsoon). © 2016, India Meteorological Department. All rights reserved.
Optimum sowing dates for soybean in Central India using CROPGRO and ClimProb symbiosis
(Cambridge University Press, 2002) Rajesh Kumar; K.K. Singh; B.R.D. Gupta; A.K. Baxla; L.S. Rathore; S.D. Attri
The optimum sowing dates for soybean cv. Gaurav were derived for Jabalpur, Raipur and Gwalior in the state of Madhya Pradesh in central India. Dates were derived based on two strategies: (a) probabilities of rainfall and temperature events using ClimProb, a PC based software package, and (b) the CROPGRO Soybean v3.0 crop growth simulation model. In Madhya Pradesh, the optimum sowing dates for multiple cropping, with the first crop as soybean under rainfed conditions, are between weeks 25 and 27, while the optimum sowing dates for rainfed mono-cropping are between weeks 28 and 29.
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.
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.