Shailesh Kumar Kharol

Effects of crop residue burning on aerosol properties, plume characteristics, and long‐range transport over northern India

Aerosol emissions from biomass burning are of specific interest over the globe due to their strong radiative impacts and climate implications. The present study examines the impact of paddy crop residue burning over northern India during the postmonsoon (October–November) season of 2012 on modification of aerosol properties, as well as the long-range transport of smoke plumes, altitude characteristics, and affected areas via the synergy of ground-based measurements and satellite observations. During this period, Moderate Resolution Imaging Spectroradiometer (MODIS) images show a thick smoke/hazy aerosol layer below 2–2.5u2009km in the atmosphere covering nearly the whole Indo-Gangetic Plains (IGP). The air mass trajectories originating from the biomass-burning source region over Punjab at 500u2009m reveal a potential aerosol transport pathway along the Ganges valley from west to east, resulting in a strong aerosol optical depth (AOD) gradient. Sometimes, depending upon the wind direction and meteorological conditions, the plumes also influence central India, the Arabian Sea, and the Bay of Bengal, thus contributing to Asian pollution outflow. The increased number of fire counts (Terra and Aqua MODIS data) is associated with severe aerosol-laden atmospheres (AOD500u2009nmu2009>u20091.0) over six IGP locations, high values of Angstrom exponent (>1.2), high particulate mass 2.5 (PM2.5) concentrations (>100–150u2009µgm−3), and enhanced Ozone Monitoring Instrument Aerosol Index gradient (~2.5) and NO2 concentrations (~6u2009×u20091015u2009mol/cm2), indicating the dominance of smoke aerosols from agricultural crop residue burning. The aerosol size distribution is shifted toward the fine-mode fraction, also exhibiting an increase in the radius of fine aerosols due to coagulation processes in a highly turbid environment. The spectral variation of the single-scattering albedo reveals enhanced dominance of moderately absorbing aerosols, while the aerosol properties, modification, and mixing atmospheric processes differentiate along the IGP sites depending on the distance from the aerosol source, urban influence, and local characteristics.

Impact of biomass burning on aerosol properties over tropical urban region of Hyderabad, India

[1]xa0Biomass burning is identified as a major source of atmospheric pollution giving rise to the release of large quantities of gaseous emissions and particulate matter. The present study aims at analyzing the impacts of biomass burning on aerosol loading over urban area of Hyderabad, India using synchronous measurements of Aerosol Optical Depth (AOD), solar irradiance in different wavelength bands, aerosol particle size distribution measurements and black carbon (BC) aerosol mass concentration. Temporal variation of AOD and aerosol index (AI) correlated with occurrence of forest fires as derived from DMSP-OLS and MODIS satellite data. BC values showed good correlation with total aerosol number density and showed patterns correlating with wind direction. Radiative forcing estimated from synchronous measurements of AOD and ground reaching broadband solar irradiance suggested −12.5W/m 2 reduction per 0.1 increase in AOD. Diffuse to direct ratio of solar irradiance showed variations correlating with changes in aerosol optical depth.

Variation in aerosol properties over Hyderabad, India during intense cyclonic conditions

In this study, we examine the changes in aerosol properties associated with an intense tropical cyclone, the so‐called ‘Mala’, that occurred during April 2006, over the Bay of Bengal. This cyclone, accompanied by very strong surface winds reaching 240 km h−1, caused extensive disasters in houses and beach resorts in the coastal areas of Myanmar. Ground‐based measurements of aerosol optical depth (AOD), particle‐size distribution and erythemal UV radiation in the neighbouring urban environment of Hyderabad, India, showed significant variations due to changes in wind velocity and direction associated with the cyclone event. The results show an increase in ground‐measured PM1.0, PM2.5, and PM10 concentrations, probably associated with the strong surface winds on 28 April, the day on which the cyclone affected the study region. In contrast, the AOD on that day exhibited a significant decrease, since the winds probably acted as a ventilation mechanism for the atmosphere. The Terra‐MODIS satellite images showed a prevalence of dust particles over the study region on the next day of the cyclone. Results from ground‐based AOD sun‐photometer observations matched well with satellite AOD retrievals. Aerosol index obtained from Ozone Monitoring Instrument (OMI) during the cyclone events suggested increasing trend, indicating the presence of an elevated dust‐aerosol layer during and after the cyclone. Results on the effects of wind and air mass fields in affecting the AOD during cyclone events are also presented.

Synoptic weather conditions and aerosol episodes over Indo-Gangetic Plains, India

The present study focuses on identifying the main atmospheric circulation characteristics associated with aerosol episodes (AEs) over Kanpur, India during the period 2001–2010. In this respect, mean sea level pressure (MSLP) and geopotential height of 700xa0hPa (Z700) data obtained from the NCEP/NCAR Reanalysis Project were used along with daily Terra-MODIS AOD550 data. The analysis identifies 277 AEs [AOD500xa0>xa0

Forest fire monitoring and burnt area mapping using satellite data: a study over the forest region of Kerala State, India

overline{AOD}

Variations in mass concentrations of airborne particulate matter over tropical urban environment

AOD¯500xa0+xa01STDEV (standard deviation)] over Kanpur corresponding to 13.2xa0% of the available AERONET dataset, which are seasonally distributed as 12.5, 9.1, 14.7 and 18.6xa0% for winter (Dec–Feb), pre-monsoon (Mar–May), monsoon (Jun–Sep) and post-monsoon (Oct–Nov), respectively. The post-monsoon and winter AEs are mostly related to anthropogenic emissions, in contrast to pre-monsoon and monsoon episodes when a significant component of dust is found. The multivariate statistical methods Factor and Cluster Analysis are applied on the dataset of the AEs days’ Z700 patterns over south Asia, to group them into discrete clusters. Six clusters are identified and for each of them the composite means for MSLP and Z700 as well as their anomalies from the mean 1981–2010 climatology are studied. Furthermore, the spatial distribution of Terra-MODIS AOD550 over Indian sub-continent is examined to identify aerosol hot-spot areas for each cluster, while the SPRINTARS model simulations reveal incapability in reproducing the large anthropogenic AOD, suggesting need of further improvement in model emission inventories. This work is the first performed over India aiming to analyze and group the atmospheric circulation patterns associated with AEs over Indo-Gangetic Plains and to explore the influence of meteorology on the accumulation of aerosols.

Case study of a dust storm over Hyderabad area, India: its impact on solar radiation using satellite data and ground measurements.

Every year, fog formation over the Indo-Gangetic Plains (IGP) of Indian region during the winter months of December-January is believed to create numerous health hazards, economic loss, and cross-country transportation of aerosols. It has attracted the global scientific communitys attention to address the uncertainties pertaining to its formation and physico-chemical properties. In this paper, we made an attempt to study the fog conditions that occurred over the north Indian region and long-range transport of aerosols from the fog region towards the southern region during November 2008, using multisatellite data sets and ground-based observations on aerosol properties and solar irradiance in the urban region of Hyderabad, India. Ground measurements showed a considerable increase in aerosol optical depth (AOD) at 500 nm ( ~ 30%) and a decrease in total solar irradiance ( ~ 7%) over Hyderabad, India, during the fog period compared to a normal day corresponding to 04 November 2008.

Contrasting Aerosol Trends Over South Asia During the Last Decade Based on MODIS Observations

The present study describes the night-time active forest fire detection capabilities of Defense Meteorological Satellite Program – Operational Linescan System (DMSP-OLS) satellite data over the forest region of Kerala State, India in 2004. Kerala State had a high incidence of forest fires during 2004 because of the extended dry season, with the unusual absence of intermittent rainfall from January to April. DMSP-OLS data were processed to detect active night-time forest fires over Kerala State and validated with ground data and fine-resolution Indian Remote Sensing (IRS)-P6 Advanced Wide Field Sensor (AWiFS) satellite imagery. DMSP-OLS-derived night-time fire products were compared with synchronous Moderate Resolution Imaging Spectroradiometer (MODIS)-derived daytime fire products to check for the spatial agreement and continuity of fires. To estimate the burnt areas, different atmospheric correction algorithms were applied to the IRS-P6 AWiFS dataset; these included the cosine approximation model (COST), ATCOR2 in ERDAS Imagine and the Second Simulation of a Satellite Signal in the Solar Spectrum (6S) code. Atmospheric corrections to the satellite data indicated significant improvement in burnt area estimates. The results of the study suggest a good correlation between AWiFS data-derived burnt areas, DMSP-OLS-derived fire counts and MODIS-derived fire products. The fire occurrences derived from DMSP-OLS and MODIS data were validated with field records on fire occurrences over the study area.