Top PDF Modelling the Radiative Effects of Biomass Burning Aerosols on Carbon Fluxes in the Amazon Region

Modelling the Radiative Effects of Biomass Burning Aerosols on Carbon Fluxes in the Amazon Region

Modelling the Radiative Effects of Biomass Burning Aerosols on Carbon Fluxes in the Amazon Region

a Now at Universities Space Research Association/Goddard Earth Sciences Technology and Research (USRA/GESTAR) at Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, MD, USA. Correspondence to: Demerval S. Moreira (demerval@fc.unesp.br) Abstract. Every year, a dense smoke haze covers a large portion of South America originating from fires in the Amazon Basin and central parts of Brazil during the dry/biomass-burning season between August and October. Over a large portion of South America, the average aerosol optical depth at 550 nm exceeds 1.0 during the fire season while the background value during the rainy season is below 0.2. Biomass burning aerosol particles increase scattering and absorption of the incident solar radiation. The regional-scale aerosol layer reduces the amount of solar energy reaching the surface, cools the near surface 5
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Impacts of water vapor/aerosol loading trends and land cover on aerosol microphysical and radiative effects on clouds during the Amazon biomass burning season

Impacts of water vapor/aerosol loading trends and land cover on aerosol microphysical and radiative effects on clouds during the Amazon biomass burning season

4 Conclusions In this study, a 5 ◦ NE×5 ◦ WE region over Rond ˆonia, Brazil was analyzed using high res- 20 olution aerosol, cloud, water vapor, and atmospheric temperature profile data from the Moderate Resolution Imaging Spectroradiometer (MODIS). Four years of data (2004– 2007) during the biomass burning transition season (August–October) were compiled to analyze the e ffect of aerosols on warm cloud development. Several years of data were employed to gather a large enough dataset for analysis, and to smooth out inter-

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Hygroscopicity of organic compounds from biomass burning and their influence on the water uptake of mixed organic ammonium sulfate aerosols

Hygroscopicity of organic compounds from biomass burning and their influence on the water uptake of mixed organic ammonium sulfate aerosols

Biomass burning is one of the important sources of an- thropogenic atmospheric aerosols and also leads to the emis- sion of greenhouse gases. The annual globally burned land area is in the range of 3 to 3.5 million square kilometers, resulting in emissions amounting to 2.5 × 10 9 kg carbon per year (van der Werf et al., 2006; Schultz et al., 2008). Parti- cles in biomass burning smoke enriched with hygroscopic organic and inorganic constituents are suggested to act as efficient cloud condensation nuclei (Novakov and Corrigan, 1996; Petters et al., 2009; Rissler et al., 2010; Dusek et al., 2011; Frosch et al., 2011). In the Amazon basin, for example, the CCN concentration in the dry season is 1 order of mag- nitude higher than in the wet season due to biomass burn- ing (Roberts et al., 2001; Carrico et al., 2008; Hening et al., 2010). In addition, the aerosol indirect climatic effects re- sulting from increased cloud condensation nuclei concentra- tions are expected to be very important in tropical regions, particularly in the regions with very high biomass burning emissions (Roberts et al., 2001; Carrico et al., 2008; Hen- ing et al., 2010). Increased CCN concentrations may lead to reduced average cloud droplet radii and associated with this, likely an enhanced negative radiative forcing of af- fected clouds (Roberts et al., 2003; Lohmann and Feichter, 2005; Dinar et al., 2006a, b, 2007; Carrico et al., 2008). Because of the complex chemical composition of biomass burning aerosols (Decesari et al., 2000, 2006; Shimmo et al., 2004), there is lack of qualitative as well as quantitative in- formation on the detailed chemical composition and mixing state (i.e., internally or externally mixed aerosol populations and/or whether individual particles consist of a single, ho- mogeneously mixed phase or multiple liquid/solid phases). Recently several groups have reported that a significant por- tion of particles in biomass burning (from 11 % to as high as 99 % by mass) consist of water-soluble organic carbon (WSOC) (Ruellan et al., 1999; Novakov and Corrigan, 1996; Narukawa et al., 1999; Hoffer et al., 2006; Iinuma et al., 2007; Fu et al., 2009; Claeys et al., 2010; Dusek et al., 2011; Psichoadaki and Pandis, 2013). One way to handle the large number of organic compounds comprised within
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Studying the impact of biomass burning aerosol radiative and climate effects on the Amazon rainforest productivity with an Earth system model

Studying the impact of biomass burning aerosol radiative and climate effects on the Amazon rainforest productivity with an Earth system model

Aerosols and their precursor emissions are the dataset used during CMIP5 (Lamarque et al., 2010). We use the decadal mean emissions centred around the year 2000 to represent present-day emission rates. Biogenic volatile organic com- pound (BVOC) emissions from vegetation (Pacifico et al., 2012) are sensitive to changes in plant productivity and hence sensitive to DFE. These emissions are calculated online but are not taken into account in the CLASSIC aerosol scheme. Instead, the climatology of BVOCs (also called secondary organics) from CMIP5 is used. The biomass burning emis- sions are based on the GFEDv2 inventory (van der Werf et al., 2006; Lamarque et al., 2010). Given the substantial inter-annual variability of biomass burning on a global and regional scale, a present-day climatology (i.e. average year) is calculated as the GFEDv2 1997–2006 average (Lamarque et al., 2010). These are the standard emission scenarios for the simulation labelled as BBAx1 for the main experiment. A total of five simulations are conducted in the main experi- ment where the standard biomass burning aerosols emissions are varied by −100 %, −50 %, 0 %, +100 % and +300 %, respectively (simulation BBAx0, BBAx0.5, BBAx1, BBAx2 and BBAx4, respectively). A multiplication factor is applied to the emission only for the BB sources over South America (40 ◦ S, 85 ◦ W; 15 ◦ N, 30 ◦ W). We define the control simula- tion as the simulation without BBA being emitted over South America (i.e. BBAx0). The changes in fast carbon fluxes are calculated as the departure from this reference simula- tion (e.g. 1 NPP BBAx1 net impact = NPP BBAx1 − NPP BBAx0 and rep- resents the net change in NPP due to standard emissions of BBA).
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Impacts of Amazonia biomass burning aerosols assessed from short-range weather forecasts

Impacts of Amazonia biomass burning aerosols assessed from short-range weather forecasts

The majority of fires worldwide occur in tropical coun- tries (Crutzen and Andreae, 1990; van der Werf et al., 2010) and the tropics play a particularly pivotal role in tropo- spheric chemistry (Crutzen and Zimmermann, 1991). Land- scape fires occur due to both natural and anthropogenic ac- tivities, such as forest fires, agricultural crop residue burning, deliberate burning of savannah grasslands and deforestation for agricultural purposes. South America accounts for an es- timated 15 % of global fire emissions of carbon from land- scape fires and open biomass burning (van der Werf et al., 2010), with regional hotspots of fire activity around the edges of Amazonia. The Amazon region experiences a large num- ber of fires each dry season (August–October). Emissions of BBA from fires greatly increase regional aerosol con- centrations (Martin et al., 2010), with dry season aerosol optical depth (AOD) of up to 4 observed at 550 nm using AERONET sun photometers (Artaxo et al., 2013). Such large concentrations of BBA with large AOD values may have sub- stantial impacts on the regional radiative balance. Procopio et al. (2004) used observations during the dry season to es- timate that Amazonian BBA caused a clear-sky radiative ef- fect of − 5 to − 12 W m −2 at top of atmosphere (TOA) and − 21 to − 74 W m −2 at the surface. Furthermore, Sena et al. (2013) used a combination of MODIS and CERES data to estimate daily direct TOA radiative effects, which reached − 30 W m −2 locally. Rosário et al. (2013) used a regional model to estimate a surface radiative effect of −55 W m −2 . Such changes in fluxes must affect Amazonian weather and a better understanding of this has potential benefits for im- proving weather and climate prediction.
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The effects of peatland restoration on methane and carbon dioxide fluxes

The effects of peatland restoration on methane and carbon dioxide fluxes

switch from a source to a net sink of carbon ten years after restoration started. However, this faster switch suggested by Bain et al. (2011) may be due to this hypothesis considering non-gaseous carbon fluxes, unlike Joosten et al. (2006). Samaritani et al. (2011) studied net ecosystem CO 2 exchange (NEE) on a cutover bog in the Jura Mountains, Switzerland over one growing season on sites where cutting had stopped 29, 42 and 51 years previously. No active restoration work had occurred, but Sphagnum cover had re-established naturally (Samaritani et al., 2011). Through both measurements and modelling, Samaritani et al. (2011) found that the 29-year site was a net source of CO 2 -C (40 g CO 2 -C m -2 ), whereas both the 42- and 51-year sites were net sinks, with respective average uptake rates of 222 and 209 g CO 2 -C m -2 . These findings by Samaritani et al. (2011) support the hypothesis of Joosten et al. (2006), in that the post-cutting sites followed a similar pattern to the graph shown in Figure 2.3; a net source followed by a net sink. From a study on a peatland over one year prior and three years post restoration in Québec, Canada where drainage ditches had been blocked and Sphagnum fragments had been introduced to speed up re-vegetation, Waddington et al. (2010) hypothesised that it would take 6-10 years from restoration for the site to become a net carbon sink, which is similar to the hypothesis presented by Bain et al. (2011). A maximum of 10 years to become a net carbon sink (Waddington et al., 2010) is a much shorter timescale than observed by Samaritani et al. (2011);
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Simultaneous measurement of multiple organic tracers in fine aerosols from biomass burning and fungal spores by HPLC MS/MS

Simultaneous measurement of multiple organic tracers in fine aerosols from biomass burning and fungal spores by HPLC MS/MS

Hence, it has been challenging to analyze the above- mentioned ve organic tracers simultaneously in the same aerosol sample with pronounced intensities. To ll such a gap, ultrasonication and high performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS) were to be employed in this study and the primary objective was to develop an organic solvent free extraction process and a simultaneous analytical method with good separation, high mass selectivity and sensitivity for the identication and quantication of target compounds including three primary biomass burning tracers (levoglucosan, mannosan, and galactosan), and two fungal spore tracers (arabitol, and mannitol).
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Determination of Extraction Efficiency of Different Solvents for Organic Carbon Content in Biomass Combustion Aerosols

Determination of Extraction Efficiency of Different Solvents for Organic Carbon Content in Biomass Combustion Aerosols

Tar ball found an important component of BrC. Atmospheric HULIS formation occurs during cloud processing of smoke from biomass burning, these are also produced through multiphase chemistry of organic constituents derived from other anthropogenic & natural sources such as vehicle exhaust, fossil fuel combustion in urban areas, biogenic & marine emission. [6] While Tar ball, commonly detected in smoke emission from smoldering burns of biofules. And these are the most absorbing and refractory BrC material that can be easily observed under the vacuum condition of an electron microscope [13]. Although OC could have an important contribution to radiative forcing, its treatment in global models to date has been simplistic; it has been treated as a compound that primarily scatters light and has invariant properties [14]. In fact, chemical and optical properties of OC may differ due to the nature of the OC source [15]. The present paper aims to contribute to understanding the variable behaviour of BrC regarding its polarity. BrC constituents exhibit characteristic of polar molecules and contain both water soluble & insoluble components. For that purpose, in current study four different solvents used for qualitative study of brown carbon composition.
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Estimation of emissions from biomass burning in China (2003–2017) based on MODIS fire radiative energy data

Estimation of emissions from biomass burning in China (2003–2017) based on MODIS fire radiative energy data

sources are shown in Fig. 2 (biomass fire emissions from the small islands in the South China Sea are not included). Forest and grassland fire emissions were mainly distributed in northeastern China and southern China. Dense vegeta- tive covers in the Yunnan–Guizhou Plateau, Inner Mongolian Plateau, Daxing’anling, Xiaoxing’anling, and the southeast hills greatly contribute to fire events. Cropland fire emissions were concentrated in the three great plains of China, namely the Northeast China Plain, the North China Plain, and the Middle-Lower Yangtze Plain. Because of high crop produc- tion in these areas, large quantities of agricultural residues were burned in fields during the short period following the harvest season. In addition, due to snowmelt in the Tian Shan, there are many oases located at the foot of the mountain range in Xinjiang Province. These oases are suitable for growing crops such as wheat and maize (Zhou et al., 2017). There- fore, crop fires emissions in Xinjiang province were higher than those in other northwestern provinces. Compared with other fire types, emissions from shrubland fire were negligi- ble and the high emissions were concentrated in Guangdong and Yunnan provinces.
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Modelling vegetation dynamics and carbon fluxes in a high Arctic mire

Modelling vegetation dynamics and carbon fluxes in a high Arctic mire

10 ability to reproduce regional and global pools, fluxes and vegetation distributions however, regional and global studies are necessary, in which model results are compared to, for example, inventory databases, inverse modelling estimates and maps of the distribution of vegetation (Sitch et al. 2003). “All models are wrong, some are useful” (Box and Draper 1987) is a famous saying by the statistician George Box that is referred to often in the context of ecosystem modelling. All model outputs have uncertainty and it is important to quantify the uncertainty in order to draw valid conclusions from modelling studies. Uncertainty of model outputs can be either due to inaccurate implementation of the processes involved (conceptual uncertainty) or due to uncertainty in the parameterization (parameter uncertainty). For model development this means that the detail in which processes are represented needs to be chosen carefully: processes should be represented as accurately as possible, as long as there is enough data available to either set the parameters directly, or to calibrate them. Additionally, limitations in computing power need to be taken into account. (Smith and Smith 2007)
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Direct radiative effects of aerosols over South Asia from observations and modeling

Direct radiative effects of aerosols over South Asia from observations and modeling

Heritage of regional characterization of columnar aero- sol optical depth (AOD) over the Indian region has begun with Mani et al. ( 1969 ) using a network of sun-photome- ters. However, this activity went to dormancy until it was given a fresh thrust with the climate perspective, as a part of the ISRO-Geosphere Biosphere program under which, a network of indigenously developed multi-wavelength solar radiometer (MWR) was established in a phased manner which has evolved into the Aerosol Radiative Forcing over India NETwork (ARFINET) (Moorthy et al. 1997 ; Babu et al. 2013 ). The data collected from these stations have been used to validate remote sensing satellite retrievals and regional climate model simulations (Nair et al. 2012 ). One of the main objectives of the ARFI project is to estimate the direct radiative forcing (DRF) due to aerosols over the region accurately by synthesizing the data collected from the ARFINET observatories supplemented with satellite data and model simulations. However, the major challenge in the estimation of measurement-based DRF from ARFI- NET data is the lack of measurements of columnar aerosol single scattering albedo (SSA) and asymmetry parameter/ phase function. The former parameter decides the sign of the radiative forcing (warming or cooling) and latter sig- nificantly influences the amount of radiation scattered back to the space. These observational constraints are not only limited to the Indian region but are global in nature as well. Several techniques have been widely used to estimate the aerosol SSA and phase function, which include inversion of sky radiation measurements using multispectral radi- ometers (Dubovik et al. 2000 ), in situ measurements of vertical distribution of scattering/absorption/extinction coefficients using aircraft (Babu et al. 2016 ), satellite meas- urements (Satheesh et al. 2009 ), semi empirical (Moorthy et al. 2009 ) and using chemical transport model simula- tions (Chin et al. 2009 ).
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Modelling of positively charged aerosols in the polar summer mesopause region

Modelling of positively charged aerosols in the polar summer mesopause region

be known to perform more sophisticated model calculations. Further experimental observations of aerosol properties at mesospheric heights are required to further elucidate the role of positively charged aerosols in creating NLCs and PMSEs. Such in situ measurements could be triggered by lidar de- tection of NLCs that require particles of a minimum size of 20–30 nm which is also a necessary though not sufficient condition for the accumulation of positive charge on aerosols. Acknowledgments. We thank Tom Blix and Ove Havnes for fruit- ful discussions, and the Andøya Rocket Range (Norway) and the Mobile Raketenbasis of the DLR in Oberpfaffenhofen (Germany) for their support during the ECHO campaign. The rocket flights and the lidar operations were supported by the Bundesministerium f¨ ur Bildung, Wissenschaft, Forschung und Technologie under grants No. 010E88027 and 50EE94010.
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An Examination of the Effects of Aerosol ChemicalComposition and Size on Radiative Properties of Multi Component Aerosols

An Examination of the Effects of Aerosol ChemicalComposition and Size on Radiative Properties of Multi Component Aerosols

rect aerosol forcing to chemical composition, size dis- tribution and relative humidity on a global scale has been tested with a “reference box model” [1] and a GCM model [6-8] Most of these studies except for Ja- cobson (2001) on direct aerosol forcing only focused on anthropogenic sulfate aerosols. The objectives of this paper are 1) to accurately calculate the refractive index of aerosol particles with the known chemical composi- tion of atmospheric aerosol; 2) to theoretically evaluate the sensitivity of aerosol radiative properties and radia- tion transmission in the visible range to refractive index, size distributions, and relative humidity (RH) using a box model that includes Mie and radiative transfer cal- culation. Since the aerosol particle refractive index is determined by its chemical composition, the depend- ence of radiative properties of aerosol particles on the refractive index can indicate the effects of chemical composition. Since most of the light scattering and ex- tinction are caused by particles in the accumulation mode size range (0.1 - 1.0 m, diameter), and these particles are neither removed effectively by impaction nor by diffusion, the accumulation mode particles are the most important one in terms of aerosol radiative forcing. In this study the sensitivity of aerosol radiative properties to size distribution is examined on the basis of the calculation of the particle radiative properties for the accumulation mode only.
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Genotoxic potential generated by biomass burning in the Brazilian Legal Amazon by Tradescantia micronucleus bioassay: a toxicity assessment study

Genotoxic potential generated by biomass burning in the Brazilian Legal Amazon by Tradescantia micronucleus bioassay: a toxicity assessment study

In this study 2 types of assessment were used: Active and Passive. In active assessment, T. pallida were cultivated in vases (50 cm × 17 cm × 17 cm) containing organic soil, watered daily, as described by Meireles et al. [35] and Sisenando et al. [36]. After a plant adaptation period (3 months), the vases were placed in 6 sampling sites (Figure 1). Passive assessment was carried out at 6 points, using plants of the same species and that grew in public gardens in the cities evaluated in this work (Figure 1). The inclusion criteria for the passive assay points were the proximity to the points selected for active monitoring and the existence of cultivated plants for more than 1 year. Inflorescence collection was performed at the same time in the two assessment types, and during two differ- ent periods: the dry season (May/08 to October/08) and the rainy season (November/08 to April/09), in order to encompass the two climatic periods of the region. The inflorescences were fixed in ethanol-acetic acid solution (3:1) for 24 hours and transferred to a solution of 70% ethanol for storage [37]. The flower buds containing tet- rads in their initial stages were dissected, mounted on slides and stained in 2% acetic-carmine, according to the protocol established by Ma et al. [37]. Analysis consisted of counting 300 cells in the tetrad stage per slide, totaling 3000 cells per sampling site, where mean micronucleus frequency (%MCN) was determined according to criteria adopted by Fenech [38].
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Use of cleaner burning biomass stoves and airway macrophage black carbon in Malawian women

Use of cleaner burning biomass stoves and airway macrophage black carbon in Malawian women

An important outstanding question is whether or not use of cleaner burning biomass-fuelled cookstoves reduces inhaled dose of PM in the group most exposed to HAP; i.e. women who do the family cooking. Al- though measuring long-term personal exposure to PM in adults by por- table monitoring is not yet practical, we previously developed a method for assessing inhaled dose of carbonaceous PM by measuring the amount of carbon in airway macrophages (AMBC) obtained using spu- tum induction. In previous studies, we have found that AMBC is in- creased in biomass-exposed women in Gondar (Ethiopia) compared to UK women (Kulkarni et al., 2005), and in UK children, found that higher AMBC is associated with impaired lung function (Kulkarni et al., 2006). Although the kinetics of AMBC have not been fully de fi ned, since AM are long-lived cells, AMBC is thought to re fl ect longer-term ex- posures (Bai et al., 2014). Since the cookstove used in the CAPS trial re- duces PM emissions by about 75% compared to open fi res in fi eld tests (Wathore et al., 2017), we hypothesised that AMBC would be reduced in women randomised to the intervention arm of the CAPS trial. We therefore sought to compare AMBC in women using the cleaner cook- stove with those using a traditional open fi re. We recruited these two groups from women nearing end of the CAPS trial (i.e. after 20 – - 24 months) who were also recruited into the Malawi Adult Lung Health Study (ALHS). In order to give comparison with a non-biomass exposed population a small group of British women were also recruited.
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Cellular inorganic carbon fluxes in Trichodesmium: a combined approach using measurements and modelling

Cellular inorganic carbon fluxes in Trichodesmium: a combined approach using measurements and modelling

© The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. Abbreviations: a carb , fractional contribution of HCO 3 – to total C i uptake into the carboxysome; a cyt , fractional contribution of HCO 3 – to total C i uptake into the cytosol; CA, carbonic anhydrase; CCM, carbon-concentrating mechanism; chl a, chlorophyll a; C i , inorganic carbon; DIC, dissolved inorganic carbon; K 1/2 , half-saturation concentration; L 13C , leakage calculated from 13 C fractionation; L carb , modelled leakage from the carboxysome; L cyt , modelled leakage over the plasma membrane;
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Chemical Composition and Molecular-specific Optical Properties of Atmospheric Brown Carbon Associated with Biomass Burning

Chemical Composition and Molecular-specific Optical Properties of Atmospheric Brown Carbon Associated with Biomass Burning

S13 Figure S8. Optical properties of bulk tar samples diluted in acetonitrile or methanol (PO - pyrolysis oily phase, PA - pyrolysis aqueous phase, OO - oxidative oily phase, OA -oxidative aqueous phase) and methanol extracted aerosolized PO samples collected on stages 5 to 10 of the MOUDI impactor. The horizontal and vertical bars indicate the SD or the error along the X and Y axis’, respectively. Stage 10 indicates the lower limit of log10 MAC 405. Light orange to brown shaded regions represent very weakly absorbing BrC (VW-BrC), weakly absorbing BrC (W-BrC), moderately absorbing BrC (M-BrC), and strongly absorbing BrC (S-BrC). 1 Circle-line pairs indicate aerosolized fresh BrC and evolution of their optical properties with time in the presence of . NO3 radicals from our recent study. 2 The blue shaded areas highlight the optical properties of water-soluble organic aerosols (WSOA) collected on filters (f#) during a biomass burning event at Rohovot, Israel. 8 The star symbol marks the upper limit of individual ‘tar ball particles’ inferred from the electron energy loss spectro-microscopy in Alexander et al. 9 AAE is calculated for the wavelength range 300-500 nm in this study, 315-450 nm in Li et al., 2 300-650 nm in Bluvshtein et
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The Effects of Chlorophyll Assimilation on Carbon Fluxes in a Global Biogeochemical Model

The Effects of Chlorophyll Assimilation on Carbon Fluxes in a Global Biogeochemical Model

3.2 FCO 2 Comparisons with Data Globally and regionally, we found that the fluxes were not greatly impacted by the assimilation of satellite chlorophyll (Figure 5 and Figure 6). In nine out of the twelve regions, the difference between the fluxes from the free-run and those after assimilation was less than 0.1 mol C m -2 y -1 . The three regions where these differences were greater than 0.1 mol C m -2 y -1 were the North Central Atlantic, South Pacific and South Indian. In the southern basins the assimilation run produced the more biased flux estimates, though the increase in bias was small (Figure 5 and Figure 6).
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Regional modelling of Saharan dust and biomass-burning smoke Part I: Model description and evaluation

Regional modelling of Saharan dust and biomass-burning smoke Part I: Model description and evaluation

The SAMUM-2 field campaign took place in the Cape Verdes from 15 January to 14 February 2008. Numerous in situ and re- mote sensing observations were collected at the airport of Praia, Cape Verde. Measurements taken aboard the research aircraft Falcon complement the ground-based measurements character- izing the mixed plume of Saharan dust and biomass-burning par- ticles. In this study we make use of (1) the particle AOT measured at Praia with an Aerosol Robotic Network (AERONET; Holben et al., 1998; Toledano et al., 2011) sun photometer (CIMEL Electronique 318A spectral radiometer), which measures sun and sky radiances at seven wavelengths (340–1640 nm). Here, only AOTs at 440 nm are considered. (2) Profiles of the 532-nm backscatter coefficient from the six-wavelength Backscatter Ex- tinction lidar-Ratio Temperature Humidity profiling Apparatus (BERTHA) of the Leibniz Institute for Tropospheric Research (IfT) (Althausen et al., 2000; Tesche et al., 2009; 2011) are used to validate the vertical profiles of the modelled dust and smoke plume over Praia. The lidar data have a spatial and tem- poral resolution of 15 m and 10 s, respectively. As described by Tesche et al. (2009), dust and smoke backscatter profiles are separated and can be compared independently. Measurements of the extinction coefficient at 355 nm from the portable lidar system (POLIS) of the Meteorological Institute of the University Munich (MIM) (Heese et al., 2002; Gross et al., 2011) are also used for model evaluation. The POLIS overlap of only 70 m allows for trustworthy extinction profiles below 1 km height. (3) The model-derived dust size distribution is compared with near-surface particle number size distributions for particles with diameters between 20 nm and 20 μm measured at Praia. The particle diameter size range of 20 nm ≤ D ≤ 10 μm was mea- sured quasi-continuously by the combination of a Differential Mobility Particle Sizer (DMPS) and an Aerodynamic Particle Sizer (APS). Particles with 4 ≤ D ≤ 500 μm were measured by impactor collection on coated glass substrates once a day (Kandler et al., 2011a,b; Schladitz et al., 2011). However, the measurements are truncated at 20 μm when compared with the modelled dust particle size to exclude locally emitted large particles (Kandler et al., 2011b). (4) Several flight experiments were conducted to measure the vertical distribution of dust and smoke particles above the observation site. The Falcon aircraft of the German Aerospace Center (DLR) carried the airborne nadir-looking High Spectral Resolution Lidar (HSRL) provid- ing vertical slices of extinction and backscatter coefficients at 532 nm (Esselborn et al., 2009), which are compared to the model-derived dust and smoke extinction coefficients along the flight paths.
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Net Ecosystem Exchange of Carbon Dioxide and Water Vapor Fluxes in Switchgrass and High Biomass Sorghum

Net Ecosystem Exchange of Carbon Dioxide and Water Vapor Fluxes in Switchgrass and High Biomass Sorghum

In this study, cumulative GEP in 2011 was 41% less than that of 2012. The large portion of this difference came during the early growing season (before the canopy fully developed) while similar rates were observed later due to reduction in carbon assimilation capacity of plants (Fig. 11). Actively growing leaves, relatively longer days, and optimal temperature for photosynthesis in the spring favored more carbon uptake. Because of more rapid increase in GEP than ER carbon use efficiency of the ecosystem was about 40% or more (up to 52%) until June. A gradual decline in net carbon uptake started from July because GEP started to decline rapidly due to reduction in photosynthetic area, but ER did not decrease greatly (Fig. 12), most likely due to respiration from dead and senescence tissues (Dufranne et al. 2011). As a result, the ratio of ER to GEP increased and ultimately the ecosystem was a source of carbon. Although different ratios of ER to GEP were observed over time during growing seasons, total seasonal ER accounted for about 75% of cumulative seasonal GEP in both years regardless of the length of growing seasons and differences in aboveground biomass production. However, due to differences in seasonal sums of GEP the ecosystem was able to gain -1128 ± 130 g CO 2 m -2 and -
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