High altitude (∼4520 m amsl) measurements of black carbon aerosols over western trans-Himalayas: Seasonal heterogeneity and source apportionment

Abstract

[1] The first ever, year-round measurements of aerosol black carbon (BC) over the western part of trans-Himalayas are reported from Hanle ($4520 m above mean sea level). The daily mean BC concentrations varied from as low as 7 ng m À3 to as high as 296 ng m À3 with an annual average of 77 AE 64 ng m À3, indicating significant BC burden even at freetropospheric altitudes. Variation with in the day as well as from day to day were highly subdued during winter season (December to February) while they used to be the highest in Spring (March to May). In general, the less frequently occurring high BC values contributed more to the annual and seasonal means, while 64% of the values were below the annual mean. Seasonally, highest BC concentration (109 AE 78 ng m

Seasonal Characteristics of Aerosol Black Carbon in Relation to Long Range Transport over Tripura in Northeast India

“…Though the optical attenuation method has shown excellent agreement with other analytic methods (Allen et al, 1999;Im et al, 2001) and has been widely used Beegum et al, 2009;Babu et al, 2011), there are several reports available in recent literature on the uncertainties related to the estimation of EBC by aethelometer (e.g., Weingartner et al, 2003;Arnott et al, 2005;Corrigan et al, 2006). From different literature, it is clear that all the available methods for measurement of EBC mass concentration are based on some assumptions that are instrument specific, site specific and also depends on the type of carbonaceous aerosol, and its fraction to the total aerosol mass (Weingartner et al, 2003;Hitzenberger et al, 2006;Moorthy et al, 2007;Nair et al, 2007).…”

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

“…This observatory is also a part of the network of observatories under Aerosol Radiative Forcing over India (ARFI) project of ISRO-GBP, which is now known as ARFINET 23,24 . Some of the findings from this observatory have been published earlier [25][26][27][28][29][30][31] . These include the role of photochemistry in the new particle formation events at the freetropospheric altitudes 25 , temporal evolution and annual cycle in BC concentration over the Himalaya 26 , dust transport and associated changes in physical and optical properties of aerosols [27][28][29][30][31] and spring-time enhancement in aerosol optical depth (AOD) and BC over Hanle 30 .…”

“…Some of the findings from this observatory have been published earlier [25][26][27][28][29][30][31] . These include the role of photochemistry in the new particle formation events at the freetropospheric altitudes 25 , temporal evolution and annual cycle in BC concentration over the Himalaya 26 , dust transport and associated changes in physical and optical properties of aerosols [27][28][29][30][31] and spring-time enhancement in aerosol optical depth (AOD) and BC over Hanle 30 . While these earlier works are focused on characterization of aerosol optical and physical properties over Hanle, this article presents the quantitative estimation of spring-time enhancement in aerosol loading, its vertical structure and possible reasons for the inter-annual variability in springtime enhancement based on long-term observations of aerosol properties over Hanle during August 2009-December 2014.…”

“…Saraswati), among which some are snow-covered throughout the year while others experience seasonal precipitation, especially during winter (December-February) and summer (JulyAugust). More details of this near-free-tropospheric background location are available in the literature [25][26][27][28][29][30][31] . Figure 2 shows the prevailing surface meteorological conditions obtained using data from a collocated automatic weather station.…”

“…Continuous measurements of BC mass concentration (M BC ) have been carried using a two-channel (370 and 880 nm) aethalometer (make: Magee Scientific) 26,30 . The Aethalometer works on the principle of optical attenuation, in which continuous filtration of the particles through a quartz filter tape that is illuminated by light sources is utilized, and light attenuation between consecutive measurements is used for the estimation of M BC deposited on the filter tape during this sampling period.…”