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    ABSTRACT: Biomass burning activity captured attention of the scientific community because of its significant impact on global climate change. In this paper, we present the results of a study of variations in aerosol optical, microphysical and radiative properties during the occasions of biomass burning at an high-altitude rural station, Sinhagad (18° 21′ N, 73° 45′ E, 1450 m AMSL), employing ground-based observations of MICROTOPS-II and short-wave (SW) Pyranometer, as well as satellite (MODIS) measurements of AOD during 28 April 2011 – 06 May 2011. Vertically resolved feature mask images from CALIPSO during night-time on available days are utilized as an additional tool to monitor the smoke/dust vertical distributions. A prominent smoke/dust layer is observed between 2 and 4 km altitude, while the CALIPSO observations of the vertical profile of aerosols are in qualitative agreement with values of MODIS-AOD550 nm. During the smoke/dust event, a drastic increase (∼0.9) in Terra/Aqua MODIS AOD550 nm is observed. Satellite data indicate a long-range transport of aerosol particles from Indo-Gangetic Plains (IGP) over large regions. The observed short-wave solar flux at the bottom of the atmosphere (BOA) is found to decrease due to aerosol extinction and was found to be −25 and −16 Wm−2 for the aerosol laden days and normal days, respectively. In addition, the transport of a wide spread forest fire plume is observed across the country as evidenced by the MODIS imagery and HYSPLIT back trajectories. The observed features are also explained on the basis of the results from the NCEP/NCAR and ECMWF re-analysis data.
    No preview · Article · Jun 2014 · Journal of Aerosol Science
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    ABSTRACT: The relationship between the number of lightning flashes (NLF) and the cosmic ray flux (CRF) during the period of ENSO (El Niño/La Niña Southern Oscillations) with and without IOD (Indian Ocean Dipole) has been studied for the first time in the region of South/Southeast Asia (8°N–35°N and 60°E–120°E) to the authors' knowledge. Our analysis shows that the relationship is governed by regional meteorology and not by direct solar influence. Unlike on global scale, the data during ENSO are important for this relationship on regional scale. CRF and NLF are in statistically significant relationship only when CRF is significantly correlated with the meteorological parameters. CRF and NLF are significantly correlated during the period of ENSO with IOD (ENSO–IOD) but not during the period of ENSO without IOD (ENSO). The Aerosol Optical Depth (AOD), the positive temperature anomaly (TA) and an increase in TA may be responsible for this relationship during the ENSO–IOD period. On the shorter temporal/spatial scale, meso-scale meteorological parameters are responsible for the negative correlation between the CRF and the NLF. On the other hand, on the longer scale, an amount of Low Level Cloud Fraction (LLCF) is responsible for the positive correlation between the CRF and the NLF. Our partial correlation analysis shows that controlling for the AOD weakens the correlation between the CRF and the NLF but does not affect that between the 12 month running means of the same. Thus, aerosols are responsible during the total study period and during the IOD period for enhancing the significant CRF–NLF relationship. Solar radio flux F10.7 cm (SRF10.7) seems to be the main controlling parameter for the stronger relationship. We find that there is a distinct difference in the average magnitude of different solar and meteorological parameters between that during the ENSO period and the ENSO–IOD period which may be attributed to the difference in cloud types and aerosol properties between the two periods. The results of our analysis may be confirmed with longer data sets and more number of IOD events in the future.
    Full-text · Article · Jun 2014 · Atmospheric Research
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    ABSTRACT: h i g h l i g h t s Similar variation of OC and EC in all seasons. Both SOC and POC almost equally contributed to form OC. Dominance of POC and EC in post-monsoon and winter. A new term Effective carbon ratio in place of conventional OC/EC.: Organic and elemental carbon OC/EC ratio Primary and secondary organic carbon Effective carbon ratio a b s t r a c t Increasing emissions from fossil-fuel, biomass burning, land use changes and industrial growth have led to rapid increase in the atmospheric concentrations of carbonaceous species over many cities in India. The present paper deals with the results obtained from year long (2012e13) observations conducted at a tropical urban location, Pune in southwestern India on Organic and Elemental Carbon as well as Black Carbon; using the Sunset OCEC Analyzer and Aethalometer, respectively. The average mass concentra-tions of OC and EC were in the order of winter > post-monsoon > summer > monsoon. Mean annual OC/ EC ratio was found to be 2.4 AE 1.1 during the study period, suggesting the presence of secondary organic carbon (SOC). Estimated SOC was found to form 47% of OC mass concentration. OC and EC were also significantly well correlated (r ¼ 0.95, p < 0.0001) to each other, indicating towards common combustion sources. The primary organic carbon (POC) dominated over SOC and EC in post-monsoon and winter seasons indicating impact of anthropogenic burning activity, enhanced by prevailing meteorological conditions as well as that of long range transport. Mean annual POC þ EC/TC ratio was 0.69 indicating that more than 2/3 of TC is formed from combustion sources. Thermally derived EC and optically derived BC correlated very well (r ¼ 0.98, p < 0.0001). A new concept e.g. Effective carbon ratio (ECR) is suggested to better assess the scattering/absorptive nature and probable source identification of carbonaceous aerosols in place of conventional OC/EC ratio.
    Full-text · Article · May 2014 · Atmospheric Environment


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