دانلود رایگان مقاله لاتین تعیین کمیت بازتاب پراکندگی آئروسل از سایت الزویر
عنوان فارسی مقاله:
تعیین کمیت بازتاب پراکندگی آئروسل آلی برفراز مناطق سوزان زیست توده گرمسیری
عنوان انگلیسی مقاله:
Quantifying organic aerosol single scattering albedo over the tropical biomass burning regions
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
During the last decade, light absorption by atmospheric aerosols has attracted significant attention because of its huge impact on regional climate and the Earth's radiation balance. In the solar spectrum, under cloud-free conditions, direct radiative forcing by atmospheric aerosols is usually negative at the top of the atmosphere (TOA); however, it can become less negative or even positive with increasing aerosol absorption (Boucher et al., 2013; Feng et al., 2013). Studies regarding aerosol light absorption have considered black carbon (BC) as a single light absorbing species. During the last 10 years, laboratory and field experiments have provided strong evidence of the fact that some organic aerosols (OAs) absorb a substantial amount of sunlight, whereas others only scatter sunlight (Kirchstetter et al., 2004; Andreae and Gelencser, 2006;Alexander et al., 2008; Chen and Bond, 2010; Chung et al., 2012; Lack et al., 2012). The evidence for the presence of light absorbing OAs originates from the spectral dependence of light absorption that cannot be explained by BC absorption near specific combustion sources. OAs that absorb sunlight appear brownish owing to their strong solar absorption toward shorter visible and ultraviolet radiation; therefore, such OAs are known as brown carbon (BrC; Andreae and Gelencser, 2006 ). The origins of atmospheric OAs are the incomplete combustion of biomass (Reid et al., 2005; Hoffer et al., 2006; Chakrabarty et al., 2010; Lack et al., 2013; Forrister et al., 2015) and fossil fuels (Bond, 2001; Yang et al., 2009; Zhang et al., 2011) and the secondary formation from gas-phase organic compounds (Laskin et al., 2014; Nakayama et al., 2013; Yu et al., 2014). The OAs make up more than 80% of fine-particle mass in the atmosphere in tropical savannas (Magi, 2009) where tens to hundreds of mega hectares are burned every year (Giglio et al., 2013) (Fig. 1). However, there are various OA source materials and chemical composition; therefore, it is difficult to generalize optical properties of OAs (Kanakidou et al., 2005). The aerosol light absorption can be quantitatively expressed by using single scattering albedo (SSA) which is defined by the ratio of aerosol light scattering to aerosol light extinction (the sum of absorption and scattering). For non-absorbing aerosols the SSA is 1. It is crucial to exactly understand the SSA of aerosol since the sensitivity in aerosol direct radiative forcing is primarily driven by differences in SSA (Abel et al., 2005; Magi et al., 2008) rather than the absolute value of absorption, and hence even small error in its estimation can change the sign of aerosol radiative forcing (Yamamoto and Tanaka, 1972; Takemura et al., 2002; Kanakidou et al., 2005). Large uncertainties exist, however, in the measurement of OA light absorption from both laboratory experiments and field observations, which tend to cause substantial overestimation of OA light absorption. For example, the extraction of laboratory generated aerosol samples with organic solvents prior to thermochemical analysis generally shows greater absorption than those not extracted (Chen and Bond, 2010). In addition, the most commonly used in situ instruments for measuring aerosol light absorption, including the Aethalometer (Magee Scientific Co., Berkely, CA) and the Particle Soot Absorption Photometer (Radiance Research, Seattle, WA), tend to overestimate aerosol light absorption because the absorption is enhanced by backscattering and multiple scattering (Chow et al., 2009). Providing long-term, continuous, and readily available aerosol observation, the ground-based worldwide network of automatic sun- and sky-scanning measurements, Aeronet Robotic Network (AERONET; Holben et al., 1998, 2001), has been used throughout the literature to determine aerosol optical properties near specific source regions (Russell et al., 2010; Giles et al., 2012). However, these observations yield column-integrated measurements and therefore include different aerosols and mixing states. To make the best use of AERONET data, there is a need for additional work in characterizing light absorption by individual aerosol species. However, due to the difficulties in separating contribution of individual species to total light absorption, only few studies tried to partition OA light absorption using AERONET (Bahadur et al., 2012; Chung et al., 2012). The main purpose of this study is the development of an algorithm to derive OA SSA empirically and the determination of OA SSA over the tropical biomass burning regions. In particular, we develop an algorithm that binds OA SSA with sulfate þ nitrate AOD mostly by using ground-based AERONET data. The algorithm partly employs the ensemble mean of model simulations. We apply this empirical algorithm to determine the OA SSA over the tropical biomass burning regions by using the sulfate þ nitrate AOD measured during the Southern African Research Initiative field campaign in August and September 2000 (SAFARI-2000) (Swap et al., 2003). The uncertainties from observations and the retrieval algorithm are extensively considered in estimating the range of OA SSA. Our method is different from that of Bahadur et al. (2012) in that there is no assumption of OA light absorption at higher wavelengths, and the OA SSA is determined from the amount of measured sulfate þ nitrate AOD. It should be also pointed out that there are large differences in individual aerosol composition among models, and the model diversity of each of aerosol component will introduce large uncertainties to the aerosol-associated solar direct radiative forcing (Kinne et al., 2006). The biases provide an additional motivation for examining observation-based retrieval of individual aerosol species such as light scattering sulfate and nitrate aerosols. We further provide the first global estimate of sulfate þ nitrate AOD constrained mostly by observations using the empirically derived OA SSA.
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کلمات کلیدی:
Biomass burning, land-cover change, and the hydrological cycle in ... iopscience.iop.org/article/10.1088/1748-9326/11/9/095005/pdf by C Ichoku - 2016 - Cited by 3 - Related articles Sep 14, 2016 - Surface albedo darkening from wildfires in northern sub-Saharan Africa. C K Gatebe .... This region is subjected to intense biomass burning during the dry ... and variation in SST over the tropical Pacific (Giannini et al 2003 ... Quantifying organic aerosol single scattering albedo over the tropical ... https://www.deepdyve.com/.../quantifying-organic-aerosol-single-scattering-albedo-o... Read "Quantifying organic aerosol single scattering albedo over the tropical biomass burning regions, Atmospheric Environment" on DeepDyve, the largest ... [PDF]Tropical biomass burning smoke plume size ... - Atmos. Chem. Phys www.atmos-chem-phys.net/12/3437/2012/acp-12-3437-2012.pdf by CS Zender - 2012 - Cited by 6 - Related articles Apr 11, 2012 - reported for tropical biomass burning plumes on three conti- nents are ... (Tosca et al., 2010) suggest that smoke may reduce regional. SST and .... higher albedo than that recommended by Reid et al. for tropi- cal forest fire smoke ... to understanding the energetic impact of a plume are its over- all scale and ... [PDF]Evaluation of biomass burning aerosols in the ... - Atmos. Chem. Phys www.atmos-chem-phys.net/16/14657/2016/acp-16-14657-2016.pdf by BT Johnson - 2016 - Cited by 1 - Related articles Nov 24, 2016 - the observed size distribution, single scattering albedo, and. Ångström exponent across different tropical biomass burn- ing source regions. [PDF]Aircraft measurements of biomass-burning aerosols over ... - Met Office ensembles-eu.metoffice.com/met-res/dabex/papers/Johnson.pdf by BT Johnson - Cited by 110 - Related articles single scattering albedos. After removing this bias, the mean single scattering albedo was 0.81 +/- 0.08 for ... regions. Biomass burning aerosols are generated mainly by agricultural burning in tropical regions. Africa, the. Amazon basin and ... Global estimate of aerosol direct radiative forcing from satellite ... https://www.nature.com/nature/journal/v438/n7071/pdf/nature04348.pdf?origin... by N Bellouin - 2005 - Cited by 331 - Related articles Anthropogenic biomass burning and industrial pollution aerosols are primarily emitted ... fires in tropical and boreal regions. Natural aerosols are .... Over land, largest AOTs are observed in the biomass-burning areas of. Africa and South ... stems from (in order of importance) too bright a surface albedo over both ocean and ...
