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

Abstract

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 2-2.5 km 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 500 m 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 (AOD 500 nm > 1.0) over six IGP locations, high values of Ångström exponent (>1.2), high particulate mass 2.5 (PM 2.5 ) concentrations (>100-150 μgm À3 ), and enhanced Ozone Monitoring Instrument Aerosol Index gradient (~2.5) and NO 2 concentrations (~6 × 10 15 mol/cm 2 ), 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.

Nature and Sources of Ionic Species in Precipitation across the Indo-Gangetic Plains, India

“…The mean specific conductivity over IGP region is much higher than that reported by IMD (1982) in rainwater at 10 background locations in India (5-57 µS cm -1 ). Prior studies (Ghude et al, 2008;Srivastava et al, 2012;Tiwari et al, 2013;Kaskaoutis et al, 2014; http://www.moef.nic.in, and references therein) of the atmospheric aerosol over the IGP region indicated high concentrations of fine particles produced by man-made and natural sources.…”

Spring-Time Enhancement in Aerosol Burden over a High-Altitude Location in Western Trans-Himalaya:Results from Long-Term Observations

“…Nainital) will continued to be exposed to the regional sources and hence the M BC levels continue to be high till the spring months. Earlier studies also have shown the influence of transported plumes originating from crop residue burning in the northwest India over the Himalayan sites 17,43,44,47 . Kaskaoutis et al 44 attributed the high aerosol loading observed over the eastern Himalaya during post-monsoon to the possible transport of plumes originated from crop residue and biomass burning activities over the western IGP (mainly Punjab).…”

“…Earlier studies also have shown the influence of transported plumes originating from crop residue burning in the northwest India over the Himalayan sites 17,43,44,47 . Kaskaoutis et al 44 attributed the high aerosol loading observed over the eastern Himalaya during post-monsoon to the possible transport of plumes originated from crop residue and biomass burning activities over the western IGP (mainly Punjab). By November, the winter conditions (sub-zero temperatures and appearance of snow caps on the mountain peaks) set in, with shallow local ABL keeping the pollutants close to the surface and with the mountain peaks being above this local ABL, BC level decreases in November.…”

“…The airmasses having long continental overpass, pick up dust and carbonaceous aerosols from western and northwestern India and transport them to the IGP and the Himalaya. Several studies carried out from the other Himalayan locations suggest that biomass (agricultural) burning over the IGP and forest fires over the Himalayan foothills are one of the major sources of carbonaceous aerosols during premonsoon 17,43,44 . Such build-up of absorbing aerosols during pre-monsoon over IGP and the Himalayan slopes, and anomalous mid and upper tropospheric warming induced by these aerosols are postulated to cause anomalies in the Asian summer monsoon due to an atmospheric radiativedynamical process proposed as elevated heat pump (EHP) effect 5,10 .…”

Determination of enhancement ratios of HCOOH relative to CO in biomass burning plumes by the Infrared Atmospheric Sounding Interferometer (IASI)

“…This is strongly possible as agricultural residue burning is prevalent in these regions (e.g., Kaskaoutis et al, 2014;Vadrevu et al, 2015). Over India and over Southeast Asia, our ER (HCOOH/CO) values (6.8 × 10 −3 ± 0.44 × 10 −3 mol mol −1 for India and 5.8 × 10 −3 ± 0.15 × 10 −3 mol mol −1 for Southeast Asia) are close to the value referenced by Akagi et al (2011) for cropland fires (6 × 10 −3 mol mol −1 ).…”