Aerosol variability and atmospheric transport in the Himalayan region from CALIOP 2007–2010 observations

Bucci, Silvia; Cagnazzo, Chiara; Cairo, F.; Liberto, Luca Di; Fierli, F.

doi:10.5194/acp-14-4369-2014

Cited by 23 publications

(7 citation statements)

References 31 publications

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“…Hamburger et al [2013] found evidence that biomass burning aerosols emitted in Venezuela are transported by the easterly trade winds toward the Andes and then orographically lifted into the FT. Similar indications of natural and anthropogenic species lifted along high mountains have been found for the Himalayan region [Bucci et al, 2014;Cong et al, 2015] and the Swiss Alps [Griffiths et al, 2014].…”

Section: Introductionsupporting

confidence: 57%

Aerosol transport over the Andes from the Amazon Basin to the remote Pacific Ocean: A multiyear CALIOP assessment

2015

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Six years (2007Six years ( -2012 of data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) satellite instrument were used to investigate the vertical distribution and transport of aerosols over the tropical South American continent and the southeast Pacific Ocean. The multiyear aerosol extinction assessment indicates that aerosols, mainly biomass burning particles emitted during the dry season in the Amazon Basin, are lifted in significant amounts over the Andes. The aerosols are mainly transported in the planetary boundary layer between the surface and 2 km altitude with an aerosol extinction maximum near the surface. During the transport toward the Andes, the aerosol extinction decreases at a rate of 0.02 km −1 per kilometer of altitude likely due to dilution and deposition processes. Aerosols reaching the top of the Andes, at altitudes typically between 4 and 5 km, are entrained into the free troposphere (FT) over the southeast Pacific Ocean. A comparison between CALIOP observations and ERA-Interim reanalysis data indicates that during their long-range transport over the tropical Pacific Ocean, these aerosols are slowly transported toward the marine boundary layer by the large-scale subsidence at a rate of 0.4 cm s −1 . The observed vertical/horizontal transport ratio is 0.7-0.8 m km −1 . Continental aerosols linked to transport over the Andes can be traced on average over 4000 km away from the continent indicating an aerosol residence time of 8-9 days in the FT over the Pacific Ocean. The FT aerosol optical depth (AOD) above the Pacific Ocean near South American coast accounts on average for 6% and 25% of the total AOD during the season of low and high biomass burning, respectively. This result shows that, during the biomass burning season, continental aerosols largely influence the AOD over the remote southeast Pacific Ocean. Overall, FT AOD decrease exponentially with the distance to continental sources at a rate of about 10% per degree of longitude over the Pacific Ocean.

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Section: Introductionsupporting

confidence: 57%

Aerosol transport over the Andes from the Amazon Basin to the remote Pacific Ocean: A multiyear CALIOP assessment

2015

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“…The slightly lower DecemberJanuary values were attributed to the confinement of the IGP polluted boundary layer below the site's altitude. Furthermore, synoptic-scale transport and changing air-mass origin affect the aerosol loading over the Himalayan sites (Xu et al, 2014;Bucci et al, 2014). The annual variation of the σ ap seems to follow that of the BC mass fraction, which was found to be ∼ 1 % during the monsoon and 7.6 % during winter associated with variation in σ ap (at 0.678 µm) from 0.9 to 33.9 Mm −1 .…”

Section: Diurnal Cycle Of Aerosol Propertiesmentioning

confidence: 91%

Scattering and absorption properties of near-surface aerosol over Gangetic–Himalayan region: the role of boundary-layer dynamics and long-range transport

et al. 2015

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Abstract. Light scattering and absorption properties of atmospheric aerosols are of vital importance for evaluating their types, sources and radiative forcing. This is of particular interest over the Gangetic-Himalayan (GH) region due to uplift of aerosol from the plains to the Himalayan range, causing serious effects on atmospheric heating, glaciology and monsoon circulation. In this respect, the Ganges Valley Aerosol Experiment (GVAX) was initiated in Nainital from June 2011 to March 2012 with the aim of examining the aerosol properties, source regions, uplift mechanisms and aerosol-radiation-cloud interactions. The present study examines the temporal (diurnal, monthly, seasonal) evolution of scattering (σ sp ) and absorption (σ ap ) coefficients, their wavelength dependence, and the role of the Indo-Gangetic plains (IGP), boundary-layer dynamics (BLD) and longrange transport (LRT) in aerosol evolution via the Atmospheric Radiation Measurement Mobile Facility. The analysis is separated for particles < 10 µm and < 1 µm in diameter in order to examine the influence of particle size on optical properties. The σ sp and σ ap exhibit a pronounced seasonal variation between the monsoon low and post-monsoon (November) high, while the scattering wavelength exponent exhibits higher values during the monsoon, in contrast to the absorption Ångström exponent which maximizes in December-March. The elevated-background measuring site provides the advantage of examining the LRT of natural and anthropogenic aerosols from the IGP and southwest Asia and the role of BLD in the aerosol lifting processes. The results reveal higher aerosol concentrations at noontime along with an increase in mixing height, suggesting influence from IGP. The locally emitted aerosols present higher wavelength dependence of the absorption in October-March compared to the rather well-mixed and aged transported aerosols. Monsoon rainfall and seasonally changing air masses contribute to the alteration of the extensive and intensive aerosol properties.

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“…To make such operational systems robust, there is a need to evaluate and refine fire-aerosol relationships in multiple regions. Specific to Asia, most of the biomass burning aerosols are often mixed from fossil fuel combustion and dust emissions (Kaskaoutis et al 2009, Bucci et al 2014, Mishra et al 2014. In such a context, an important question to address is 'how much of the AOD increase is due to biomass burning and how well do satellite fire retrievals explain AOD variation?…”

Section: Introductionmentioning

confidence: 99%

Vegetation fires, absorbing aerosols and smoke plume characteristics in diverse biomass burning regions of Asia

Vadrevu

Lasko

Giglio

et al. 2015

Environ. Res. Lett.

109

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In this study, we explored the relationships between the satellite-retrieved fire counts (FC), fire radiative power (FRP) and aerosol indices using multi-satellite datasets at a daily time-step covering ten different biomass burning regions in Asia. We first assessed the variations in MODIS-retrieved aerosol optical depths (AOD's) in agriculture, forests, plantation and peat land burning regions and then used MODIS FC and FRP (hereafter FC/FRP) to explain the variations in AOD characteristics. Results suggest that tropical broadleaf forests in Laos burn more intensively than the other vegetation fires. FC/FRP-AOD correlations in different agricultural residue burning regions did not exceed 20% whereas in forest regions they reached 40%. To specifically account for absorbing aerosols, we used Ozone Monitoring Instrument-derived aerosol absorption optical depth (AAOD) and UV aerosol index (UVAI). Results suggest relatively high AAOD and UVAI values in forest fires compared with peat and agriculture fires. Further, FC/FRP could explain a maximum of 29% and 53% of AAOD variations, whereas FC/FRP could explain at most 33% and 51% of the variation in agricultural and forest biomass burning regions, respectively. Relatively, UVAI was found to be a better indicator than AOD and AAOD in both agriculture and forest biomass burning plumes. Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations data showed vertically elevated aerosol profiles greater than 3.2-5.3 km altitude in the forest fire plumes compared to 2.2-3.9 km and less than 1 km in agriculture and peat-land fires, respectively. We infer the need to assimilate smoke plume height information for effective characterization of pollutants from different sources.

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Aerosol variability and atmospheric transport in the Himalayan region from CALIOP 2007–2010 observations

Cited by 23 publications

References 31 publications

Aerosol transport over the Andes from the Amazon Basin to the remote Pacific Ocean: A multiyear CALIOP assessment

Aerosol transport over the Andes from the Amazon Basin to the remote Pacific Ocean: A multiyear CALIOP assessment

Scattering and absorption properties of near-surface aerosol over Gangetic–Himalayan region: the role of boundary-layer dynamics and long-range transport

Vegetation fires, absorbing aerosols and smoke plume characteristics in diverse biomass burning regions of Asia

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