4 research outputs found
Meridional gradients in aerosol vertical distribution over Indian Mainland: Observations and model simulations
No full textMulti-year observations from the network of ground-based observatories (ARFINET), established under the project `Aerosol Radiative Forcing over India' (ARFI) of Indian Space Research Organization and space-borne lidar `Cloud Aerosol Lidar with Orthogonal Polarization' (CALIOP) along with simulations from the chemical transport model `Goddard Chemistry Aerosol Radiation and Transport' (GOCART), are used to characterize the vertical distribution of atmospheric aerosols over the Indian landmass and its spatial structure. While the vertical distribution of aerosol extinction showed higher values close to the surface followed by a gradual decrease at increasing altitudes, a strong meridional increase is observed in the vertical spread of aerosols across the Indian region in all seasons. It emerges that the strong thermal convections cause deepening of the atmospheric boundary layer, which although reduces the aerosol concentration at lower altitudes, enhances the concentration at higher elevations by pumping up more aerosols from below and also helping the lofted particles to reach higher levels in the atmosphere. Aerosol depolarization ratios derived from CALIPSO as well as the GOCART simulations indicate the dominance of mineral dust aerosols during spring and summer and anthropogenic aerosols in winter. During summer monsoon, though heavy rainfall associated with the Indian monsoon removes large amounts of aerosols, the prevailing southwesterly winds advect more marine aerosols over to landmass (from the adjoining oceans) leading to increase in aerosol loading at lower altitudes than in spring. During spring and summer months, aerosol loading is found to be significant, even at altitudes as high as 4 km, and this is proposed to have significant impacts on the regional climate systems such as Indian monsoon. (C) 2015 Elsevier Ltd. All rights reserved
Role of circulation parameters in long range aerosol transport: evidence from Winter-ICARB
No full textThis study explores the inevitable role of wind parameters such as wind speed, wind convergence and wind vorticity in the long range transport and distribution of aerosols in the winter time atmosphere over the Bay of Bengal (BoB) during the campaign Winter ICARB. MODIS observed aerosol optical depth (AOD), with an excellent agreement with ship borne Microtops AOD, was found to increase over the BoB particularly, in the eastern parts during the course of the campaign. The influence of atmospheric circulation on this increase is examined using the wind field from NCEP reanalysis and computed wind convergence and vorticity for first and second halves (FH and SH) of the campaign along with a back trajectory analysis using HYSPLIT transport and dispersion model. While surface winds over the BoB remained nearly the same throughout the campaign denying the possibility of enhancement in marine aerosol generation, the higher altitude winds altered significantly in SH providing a channel for aerosol transport from the Indian landmass to the BoB in addition to the increased forest fire contribution from south Asia. This suggested mechanism is supported by CALIPSO aerosol extinction profiles over the eastern BoB and the surrounding land masses. Fine particle dominance in MODIS AOD and diminished correlation between ship borne AOD and surface aerosol mass measurements during SH corroborate this inference by indicating the presence of elevated aerosol layers, which can contribute substantially to the radiative effects of the earth–atmosphere system. This study throws light on the importance of wind convergence and vorticity in the investigations on the long range transport and spatial distribution of aerosols
Spatial and temporal variabilities in vertical structure of the Marine Atmospheric Boundary Layer over Bay of Bengal during Winter Phase of Integrated Campaign for Aerosols, gases and Radiation Budget
No full textLong-term changes in aerosol radiative properties over Ny-Ålesund: Results from Indian scientific expeditions to the Arctic
No full textContinuous long-term monitoring of black carbon (BC) mass concentration and aerosol light scattering coefficient (σSCA), supplemented by number size distribution and chemical composition, are utilized in this study to understand the temporal changes in aerosol properties, associated source processes and radiative effects at Ny-Ålesund (79 oN) in the Svalbard Archipelago. A statistically significant decreasing trend in BC (- 24.7 ng m−3 decade−1) is observed during spring of 2010–2019. In contrast, σSCA depicted a general increasing trend (5.2 Mm−1 decade−1) during 2011–2016. BC and σSCA were higher during winter and spring. Aerosol single scattering albedo was highest in May ~ 0.95 (during spring) and lowest in September ~ 0.87 (during summer). Fractional share of BC to total aerosol mass was higher in winter and summer. Anthropogenic SO42− and NO3− (after ssNa+) species dominated the summer, when total number and mass concentrations of aerosols were at their minimum. Elemental Carbon (EC) and Organic Carbon (OC) showed higher concentrations in spring with EC-to-OC ratio ~ 0.08 - 0.22. The columnar AOD varied between 0.01 and 0.20 (annual mean ~ 0.09), resulting in aerosol radiative forcing (in the top of the atmosphere) ~ 0.15 - 2.69 Wm-2 in the month of April (during spring). Potential source contribution function (PSCF) revealed the dominant source areas to be over Europe and Russia in terms of contributing to the seasonal high BC mass concentrations at Ny-Ålesund. Our study has also revealed an unusual impact of biomass burning aerosols (advected from the Alaska wildfire) during July 2015.journal articl
