Puna Sinha - Academia.edu (original) (raw)

Papers by Puna Sinha

Vertical distribution of aerosols and their composition in the lower troposphere is critically im... more Vertical distribution of aerosols and their composition in the lower troposphere is critically important for assessing the Earth's radiation budget and their impact on monsoon circulation. We combine the extinction coefficient, particulate depolarization ratio obtained from CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) for period of 11 years (2008-2018) over the Indian region to provide an unprecedented climatological overview of the physical and optical characteristics of quasi-aerosol layers and their source and formation mechanism throughout its annual life cycle in the free troposphere. The key findings includes: i)The quasi aerosol layer over the Indian region are found to be persistent between 4-6 km during all seasons and occasionally reach above 6 km and exhibited strong seasonal and regional dependency, ii) Layer thickness varies between 2.0-3.0 km corresponds to primary peak are more frequent of about 80-90 % of cases over all six regions and while secondary layer occasionally forms (10-20 %), iii) The aerosol layer thickness increases by about 36.7 and 25% during summer and fall season compared to that of spring, and winter, iv) Layer-AOT showed year-to-year variations of up to a factor of two with a relative variability of about 15-23% (1σ), v) Trend in layer AOT is not very conspicuous and showed oscillatory pattern, vi) Depolarization ratios generally increase with height suggesting that the irregularity of aerosol shape increases with altitude, vii) The polluted dust and smoke are the major aerosol components of the observed quasi aerosol layer between 4 to 6 km for spring and fall season while these are the polluted dust during winter and summer.

Journal of Geophysical Research: Atmospheres, 2020

Black carbon (BC) aerosol deposited in and onto Arctic snow increases the snow's absorption o... more Black carbon (BC) aerosol deposited in and onto Arctic snow increases the snow's absorption of sunlight and accelerates snowmelt. Wet removal of BC from the atmosphere plays a key role in determining its abundance in the Arctic atmosphere and in Arctic snow. However, this process is poorly understood, mainly due to the scarcity of relevant measurements. To reveal characteristic features of the wet deposition of BC, we made measurements of mass concentration of BC in snow and rain (C_MBC) with relatively high (16%) accuracy and mass concentration of BC in air (M_BC) at the Barrow Atmospheric Baseline Observatory, Alaska, from July 2013 to August 2017 and analyzed them along with routinely measured meteorological parameters from Barrow. Monthly mean M_BC near the surface and C_MBC were poorly correlated from midwinter to early spring, when C_MBC was close to the annual median while M_BC was at its annual peak. Seasonal variations in the altitude distribution of M_BC may lead to these differences in seasonal variation of M_BC near the surface and C_MBC. About 50% of the annual wet deposition of BC occurred in the three months of summer, associated with high values of total precipitation and BC originating from biomass burning. Size distributions of BC in snow and rain were stable throughout the year, suggesting that the size distribution of BC in the lower troposphere was similarly stable. Calculations by two global models reproduced the observed seasonal variations of C_MBC and showed that BC from biomass burning dominated C_MBC in summer.

Aerosol Science and Technology, 2019

Long-term measurements of black carbon (BC) aerosols by filter-based absorption photometers with ... more Long-term measurements of black carbon (BC) aerosols by filter-based absorption photometers with a heated inlet (COSMOS) in different regions have been useful in elucidating spatial variations and radiative impacts of BC. Evaluations of mass concentrations of BC (M BC) measured by the COSMOS have been made by our previous studies through comparisons with other measurement techniques. However, how variations in the microphysical properties of BC and the co-existing light scattering aerosols affect the COSMOS measurements should be evaluated in more detail. In this study, we assessed these potential effects under various field environments in the Arctic and in the East Asia. From the slopes of the correlation plots between the M BC values measured by the COSMOS and a single-particle soot photometer, the average accuracy of the COSMOS was estimated as $10% in the M BC range 1-3000 ng m À3. On an hourly basis, the estimated sensitivity of the COSMOS M BC values to the changes in the BC size distributions was less than 10%, within the typical variabilities of BC size at individual observation sites. The COSMOS measurements depended little on the mixing states of BC and the concentrations of co-existing light scattering aerosols, except in the maritime air masses of East Asia, where the relative abundance of sea salt to BC was very high. The M BC measured by COSMOS also well agreed with elemental carbon measurements. Our results demonstrate the high reliability of COSMOS measurements under various environments.

Theoretical and Applied Climatology, 2015

The influence of lightning over surface-level trace gases was examined for pre-monsoon and monsoo... more The influence of lightning over surface-level trace gases was examined for pre-monsoon and monsoon seasons in the year 2012. Lightning events were measured using ground-based electric field monitor (EFM) and space-based lightning imaging sensor (LIS). The results showed that lightning frequency was higher during pre-monsoon period compared to monsoon, which is in good agreement with the satellite retrievals. The increase in concentration of NO x on lightning event led to a subsequent decrease in surface O 3 due to the titration reaction. Source apportionment study of SO 2 /NO x (S/N) and CO/NO x (C/N) ratios and poor correlation of NO x vs CO and NO x vs SO 2 on the lightning day confirmed the emission of NO x from dissimilar sources.

According to the Indian meteorological data analysis the year 2009 received inadequate rainfall d... more According to the Indian meteorological data analysis the year 2009 received inadequate rainfall during monsoon while the year 2010 was a normal monsoon year all over the country. To study the impact of pre-monsoon aerosol loading on successive monsoon rainfall, aerosol optical depth (AOD) and shortwave direct aerosol radiative forcing (SWARF) values are analyzed over four different locations of India: Patiala (30.33ºN, 76.46ºE), Hyderabad (17.48ºN, 78.4º E), Kanpur (26.5ºN, 80.2 ºE) and Dibrugarh (27.3 ºN, 94.6 ºE) for the pre-monsoon and monsoon seasons of the two years. The differences in the optical and radiative properties of aerosols in the two years have also been examined. For estimation of the SWARF the Optical Properties of Aerosols and Clouds (OPAC) outputs are used as inputs of Santa Barbara Discrete Ordinate Atmospheric Radiative Transfer (SBDART) model. In the year 2009 the AOD in pre-monsoon season was higher than monsoon AOD at Dibrugarh and Hyderabad (0.63 and 0.57in...

Air Quality, Atmosphere & Health, 2015

The chemistry and variation in light molecular weight (C 2-C 5) volatile organic compounds (VOCs)... more The chemistry and variation in light molecular weight (C 2-C 5) volatile organic compounds (VOCs) and nitrogen oxides (NO x =NO+NO 2) over the formation of tropospheric ozone (O 3) was studied for a time period of 1 year (2013) at a tropical urban site located in Deccan plateau region of Hyderabad, India, with semi-arid climate. Diel pattern of hydrocarbons showed maxima in the morning and night and minima in the afternoon. Ethylene and propylene showed relatively larger diurnal amplitude than other hydrocarbons. Among the analyzed hydrocarbons, acetylene was the most abundant with an annual mean of 5.5±1.3 ppbv. All the VOCs exhibited a seasonal variation with monsoon and summer minimum and winter maximum. Ozone formation potentials (OFP) and propylene-equivalents (propy-equiv.) were calculated to account the contribution of individual hydrocarbons towards formation of O 3. Propylene had the highest contribution of propy-equiv. (34 %) and OFP (28.4 %) among the VOCs observed. The concentrations of VOCs and their reactivity with hydroxyl radicals played a significant role on the levels of propy-equiv. and OFP. Strong correlations 0.65 and 0.77 were observed between O 3 vs. propy-equiv. and O 3 vs. OFP, respectively. The crossover point relationship between NO x , VOCs, and O 3 showed enhancement of O 3 at lower levels and decreased at higher levels of NO x in the range of VOCs concentrations studied. Among hydrocarbons, propylene (10) and ethane (6.5) showed the highest and lowest crossover points, respectively.

Advances in Meteorology, Climatology and Atmospheric Physics, 2012

ABSTRACT The measurements of aerosol physical optical properties were carried out over placeBay o... more ABSTRACT The measurements of aerosol physical optical properties were carried out over placeBay of Bengal (BoB) during the period 27 December 2008--30 January 2009 as part of Winter Integrated Campaign on Aerosols, Gases and Radiation Budget (W-ICARB). The aerosol number size distribution at the surface was found to be bi-modal in the 72% of the cases with mode radius for the submicron aerosol of 0.13±0.01 μ m and 0.72±0.10μ m for the super-micron aerosol and the highest NT (350-550 cm{-3}), AOD500 (0.7}) and α 380-870 values were observed in western and northern BoB with lower values in the southern and parts of central BoB. The eastern part of BoB which was investigated for the first time showed concurrently high values of NT (200 and 300 cm-3), AOD500 (0.39±0.07) and α 380-870 (1.27±0.09). The aerosol types are examined using a classification scheme based on the relationship between aerosol load (AOD500) and particle size (α 380-870). The classification scheme indicated an extremely large fraction of fine-mode aerosols in turbid atmospheres, which is even larger than 90% in the western part of BoB and approaches 100% over eastern BoB. Furthermore, there is also an evidence of aerosol-size growth under more turbid conditions indicative of coagulation and/or humidification over specific BoB regions. The altitude variation of aerosol number density made for the first time over five different locations in BoB is found to be nearly steady at all locations within the convective boundary layer (up to 400 m), while above the aerosol concentration is found to decrease except for far east BoB. Examination of the air-mass back trajectories and the aerosol size distribution indicates that the aerosols advected from continental country-regionIndia have a pronounced natural (coarse mode) component, while those originating from placeEast Asia are in general accumulation origin.

Atmospheric Chemistry and Physics Discussions, 2011

Ship-borne observations of spectral aerosol optical depth (AOD) have been carried out over the en... more Ship-borne observations of spectral aerosol optical depth (AOD) have been carried out over the entire Bay of Bengal (BoB) as part of the W-ICARB cruise campaign during the period 27 December 2008-30 January 2009. The results reveal a pronounced temporal and spatial variability in the optical characteristics of aerosols mainly due to anthropogenic emissions and their dispersion controlled by local meteorology. The highest aerosol amount, with mean AOD 500 over 0.4, being even above 1.0 on specific days, is found close to the coastal regions in the western and northern parts of BoB. In these regions theÅngström exponent is also found to be high (∼ 1.2-1.25) indicating transport of strong anthropogenic emissions from continental regions. A very high AOD 500 (0.39 ± 0.07) and α 380-870 values (1.27 ± 0.09) are found for the first time over the Eastern BoB, which was unexplored in the earlier ICARB-06 campaign. Except from the large α 380-870 values, an indication of strong fine-mode dominance is also observed from the AOD curvature, which is negative in the vast majority of the cases, suggesting dominance of an anthropogenic-pollution aerosol type. On the other hand, clean maritime conditions are rather rare over the region, while the aerosol types are further examined through a classification scheme using the relationship between α and dα. It was found that even for the same α values the fine-mode dominance is larger for higher AODs showing the strong continental influence over the marine environment of BoB. Furthermore, there is also an evidence of aerosol size growth under more turbid conditions indicative of coagulation and/or humidification over specific BoB regions. The results obtained using OPAC model show significant fraction of soot aerosols (∼ 6-8%) over the Eastern and Northwestern BoB, while coarse-mode sea salt particles are found to dominate in the southern parts of BoB.

Atmospheric Measurement Techniques Discussions, 2011

Atmospheric aerosols over south Asia constitute a major environmental and climate issue. Thus, ex... more Atmospheric aerosols over south Asia constitute a major environmental and climate issue. Thus, extensive land and cruise campaigns have been conducted over the area focusing on investigating the aerosol properties and climate implications. Except from the ground-based instrumentation, several studies dealt with analyzing the aerosol properties from space, focusing mainly on the spatial distribution of the aerosol optical depth (AOD) and possible feedbacks of aerosols on the monsoon system. However, except from some works using ground-based instrumentation or satellite observations over a specific region, there is lack of studies dealing with monitoring of the aerosol trend over south Asia. The present work analyzes the variations and trends in aerosol load over south Asia using Terra-MODIS AOD 550 data in the period 2000-2009. Overall, an increasing trend of 10.17 % in AOD is found over whole south Asia, which exhibits large spatio-temporal variation. More specifically, the AOD 550 increasing trend is more pronounced in winter, and especially over northern India. The present study shows an evidence of a decreasing AOD 550 trend over the densely-populated Indo-Gangetic Plains (IGP) during the period April-September, which has never been reported before. This decreasing trend is not statistically significant and leads to an AOD change of −0.01 per year in June, when the dust activity is at its maximum. The AOD decrease seems to be attributed to weakness of dust activity in the northwest of India, closely associated with expansion of the vegetated areas and increase in precipitation over the Thar desert. Similarly, GOCART simulations over south Asia show a pronounced decreasing trend in dust AOD in accordance with MODIS. However, much more analysis and longer dataset are required for establishing this evidence. 1 Introduction Atmospheric aerosols affect in many ways the global climatic system, i.e. by attenuating the solar radiation reaching the ground, modifying the solar spectrum, redistributing

Orthopedics, 2008

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Advances in Meteorology, 2012

This study focuses on the detection of the dust source region and monitoring of the transport of ... more This study focuses on the detection of the dust source region and monitoring of the transport of the dust plume from its primary outflow to final deposition. The application area is the Sahara desert and the eastern Mediterranean, where two dust events occurred during the period 4-6 February 2009, an unusual event for a winter period. The Aqua-MODIS and OMI observations clearly define the spatial distribution of the dust plumes, while the CALIPSO observations of total attenuated backscatter (TAB) at 532 nm, depolarization ratio (DR), and attenuated color ratio (1064/532 nm) on 5 February 2009 provide a clear view and vertical structure of the dust-laden layer. The dust source region is defined to be near the Chad-Niger-Libyan borders, using satellite observations and model (DREAM) output. This dust plume is vertically extended up to 2.5 km and is observed as a mass plume of dust from surface level to that altitude, where the vertical variation of TAB (0.002 to 0.2) and DR (0.2-0.5) implies dust-laden layer with non-spherical particles. CALIPSO profiles show that after the dust plume reached at its highest level, the dust particles start to be deposited over the Mediterranean and the initial dust plume was strongly attenuated, while features of dust were limited below about 1-1.5 km for latitudes northern of ∼36 • (Greek territory).

Journal of Atmospheric and Solar-Terrestrial Physics, 2011

... and Vertical Structure of the MABL Aerosols over Bay of 1 Bengal during winter: Results from ... more ... and Vertical Structure of the MABL Aerosols over Bay of 1 Bengal during winter: Results from W-ICARB Experiment 2 3 PR Sinha 1 , RK Manchanda 1 , JV ... D. Bala Subrahamanyam and NVPKiran Kumar for providing the 339 meteorological parameters used in this study. ...

Journal of Atmospheric and Solar-Terrestrial Physics, 2013

ABSTRACT Time variability of black carbon (BC) aerosols over different timescales (daily, weekly ... more ABSTRACT Time variability of black carbon (BC) aerosols over different timescales (daily, weekly and annual) is studied over a tropical urban location Hyderabad in India using seven channel portable Aethalometer. The results for the 2-year period (January 2009–December 2010) show a daily-mean BC variability from ~1.00±0.12 µg m−3 to 12.50±3.06 µg m−3, with a remarkable annual pattern of winter high and monsoon low. The BC values maximize during winter (December–January), ~6.67±0.22 µg m−3, and drop during summer (June–August), ~2.36±0.09 µg m−3, which establishes a large seasonal variation. Furthermore, the BC mass concentration exhibits a well-defined diurnal variation, with a morning peak and early afternoon minimum. The magnitude of the diurnal variations is seasonal dependent, which maximizes during the winter months. Air mass back trajectories indicated several different transport pathways, while the concentration weighted trajectory (CWT) analysis reveals that the most important potential sources for BC aerosols are the Indo-Gangetic plain (IGP), central India and some hot spots in Pakistan, Arabian Peninsula and Persian Gulf. The absorbing Ångström exponent (αabs) estimated from the spectral values of absorption coefficient (σabs) ranges from 0.9 to 1.1 indicating high BC/OC ratio typical of fossil fuel origin. The annual average BC mass fraction to composite aerosols is found to be (10±3) % contributing to the atmospheric forcing by (55±10) %. The BC radiative forcing at the atmosphere shows strong seasonal dependency with higher values in winter (33.49±7.01) and spring (31.78±12.89) and moderate in autumn (18.94±6.71) and summer (13.15±1.66). The BC radiative forcing at the top of the atmosphere (TOA) is positive in all months, suggesting an overall heating of the regional climate over Hyderabad.

Journal of Atmospheric and Solar-Terrestrial Physics, 2012

Sudden blockage of the solar radiation during the eclipse leads to both prompt and delayed effect... more Sudden blockage of the solar radiation during the eclipse leads to both prompt and delayed effects on both the stratospheric and the tropospheric ozone. In this paper we present the in-situ measurements of vertical distribution of ozone made by ozonesondes during the annular solar eclipse of January 15, 2010 from Thiruvananthapuram (8.531N, 76.871E). Concurrent measurement of various atmospheric parameters, columnar ozone and UV radiation were also made from ground. The column ozone showed a large decrease matching well with the maximum phase of the eclipse. A systematic decrease in the ozone concentration observed in the stratosphere. A formation of double mixed layer inversion was also observed at $ 2 km on the eclipse day. The eclipse was manifested from the space and captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua satellites.

International Journal of Environmental Science and Technology, 2014

Increasing concentration of tropospheric ozone (O 3) is a serious air pollution problem faced com... more Increasing concentration of tropospheric ozone (O 3) is a serious air pollution problem faced commonly by the urban people. The present study emphasizes on variations of air pollutant concentrations viz., O 3 , nitrogen oxides (NO x), carbon monoxide (CO), sulfur dioxide (SO 2) and black carbon (BC) at a tropical urban site located in the Deccan plateau region with semi-arid climate. The air monitoring site revealed typical diurnal/seasonal trends attributing to the complex chemistry of surface O 3 formation from its precursors. Role of SO 2 in the formation of free radical (HO Á 2) and its impact on O 3 concentration is distinguished part of the study. The results showed the highest mean O 3 in summer (57.5 ± 15.2 ppbv) followed by winter and monsoon. Observations of BC aerosols showed the highest mean value during winter (8.2 ± 2 lg m-3) and the lowest in monsoon (4.2 ± 1 lg m-3). Besides local influences, long-range transport of air masses were also studied by simulating back trajectories at different elevations during the study period. Furthermore, statistical analysis and modeling was performed with both linear (regression) and nonlinear (neural network) methods.

Geophysical Research Letters, 2011

First ever in-situ measurements of black carbon (BC) aerosols in the troposphere (up to 9 km) mad... more First ever in-situ measurements of black carbon (BC) aerosols in the troposphere (up to 9 km) made over central India and the resulting atmospheric impact as revealed by the environment lapse rate are presented. The altitude distribution of BC showed multiple peaks; two ...

Environmental Monitoring and Assessment, 2013

Diwali is one of the largest festivals for Hindu religion which falls in the period October-Novem... more Diwali is one of the largest festivals for Hindu religion which falls in the period October-November every year. During the festival days, extensive burning of firecrackers takes place, especially in the evening hours, constituting a significant source of aerosols, black carbon (BC), organics, and trace gases. The widespread use of sparklers was found to be associated with short-term air quality degradation events. The present study focuses on the influence of Diwali fireworks emissions on surface ozone (O 3), nitrogen oxides (NO x), and BC aerosol concentration over the tropical urban region of Hyderabad, India during three consecutive years (2009-2011). The trace gases are analyzed for pre-Diwali, Diwali, and post-Diwali days in order to reveal the festivity's contribution to the ambient air quality over the city. A twofold to threefold increase is observed in O 3 , NO x , and BC concentrations during the festival period compared to control days for 2009-2011, which is mainly attributed to firecrackers burning. The high correlation coefficient (~0.74) between NO x and SO 2 concentrations and higher SO 2 /NO x (S/N) index suggested air quality degradation due to firecrackers burning. Furthermore, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation-derived aerosol subtyping map also confirmed the presence of smoke aerosols emitted from firecrackers burning over the region. Nevertheless, the concentration level of pollutants exhibited substantial decline over the region during the years 2010 and 2011 compared to 2009 ascribed to various awareness campaigns and increased cost of firecrackers.