WorldWideScience

Sample records for aerosol indirect effect

  1. Natural aerosol direct and indirect radiative effects

    OpenAIRE

    Rap, Alexandru; Scott, Catherine E.; Spracklen, Dominick V; Bellouin, Nicolas; Forster, Piers M.; Carslaw, Kenneth S.; Schmidt, Anja; Mann, Graham

    2013-01-01

    Natural aerosol plays a significant role in the Earth's system due to its ability to alter the radiative balance of the Earth. Here we use a global aerosol microphysics model together with a radiative transfer model to estimate radiative effects for five natural aerosol sources in the present-day atmosphere: dimethyl sulfide (DMS), sea-salt, volcanoes, monoterpenes, and wildfires. We calculate large annual global mean aerosol direct and cloud albedo effects especially for DMS-derived sulfate ...

  2. Evaluating aerosol indirect effect through marine stratocumulus clouds

    Energy Technology Data Exchange (ETDEWEB)

    Kogan, Z.N.; Kogan, Y.L.; Lilly, D.K. [Univ. of Oklahoma, Norman, OK (United States)

    1996-04-01

    During the last decade much attention has been focused on anthropogenic aerosols and their radiative influence on the global climate. Charlson et al. and Penner et al. have demonstrated that tropospheric aerosols and particularly anthropogenic sulfate aerosols may significantly contribute to the radiative forcing exerting a cooling influence on climate (-1 to -2 W/m{sup 2}) which is comparable in magnitude to greenhouse forcing, but opposite in sign. Aerosol particles affect the earth`s radiative budget either directly by scattering and absorption of solar radiation by themselves or indirectly by altering the cloud radiative properties through changes in cloud microstructure. Marine stratocumulus cloud layers and their possible cooling influence on the atmosphere as a result of pollution are of special interest because of their high reflectivity, durability, and large global cover. We present an estimate of thet aerosol indirect effect, or, forcing due to anthropogenic sulfate aerosols.

  3. Aerosol Indirect effect on Stratocumulus Organization

    Science.gov (United States)

    Zhou, X.; Heus, T.; Kollias, P.

    2015-12-01

    Large-eddy simulations are used to investigate the role of aerosol loading on organized Stratocumulus. We prescribed the cloud droplet number concentration (Nc) and considered it as the proxy for different aerosol loading. While the presence of drizzle amplifies the mesoscale variability as is in Savic-Jovcic and Stevens (JAS, 2008), two noticeable findings are discussed here: First, the scale of marine boundary layer circulation appears to be independent of aerosol loading, suggesting a major role of the turbulence. The precise role of the turbulence in stratocumulus organization is studied by modifying the large scale fluctuations from the LES domain. Second, while it is commonly thought that the whole circulation needs to be represented for robust cloud development, we find that stratocumulus dynamics, including variables like w'w' and w'w'w', are remarkably robust even if large scales are ignored by simply reducing the domain sizes. The only variable that is sensitive to the change of the scale is the amount of cloudiness. Despite their smaller cloud thickness and inhomogeneous macroscopic structure for low Nc, individual drizzling clouds have sizes that are commensurate with circulation scale. We observe an Nc threshold below which stratocumulus is thin enough so that a little decrease of Nc would lead to great change of cloud fraction. The simulated cloud albedo is more sensitive to in-cloud liquid water content than to the amount of cloudiness since the former decreases at least three times faster than the latter due to drizzle. The main impact of drizzle evaporation is observed to keep the sub-cloud layer moist and as a result to extend the lifetime of stratocumulus by a couple of hours.

  4. Simulation of climate response to aerosol direct and indirect effects with aerosol transport‐radiation model

    OpenAIRE

    Takemura, Toshihiko; Nozawa, Toru; Emori, Seita; Nakajima, Takashi-Y.; Nakajima, Teruyuki

    2005-01-01

    With a global aerosol transport‐radiation model coupled to a general circulation model, changes in the meteorological parameters of clouds, precipitation, and temperature caused by the direct and indirect effects of aerosols are simulated, and its radiative forcing are calculated. A microphysical parameterization diagnosing the cloud droplet number concentration based on the Köhler theory is introduced into the model, which depends not only on the aerosol particle number concentration but als...

  5. Emulation of Cloud-Aerosol Indirect Radiative Effects (ECLAIRE)

    Science.gov (United States)

    Dunne, E. M.; Korhonen, H.; Kokkola, H.; Lee, L.; Romakkaniemi, S.

    2014-12-01

    Resolving sub-grid-scale interactions between clouds and aerosols is one of the biggest challenges facing climate models in the 21st century. By carefully selecting boundary conditions to represent grid boxes in larger-scale models, an emulator of a cloud-resolving model can be created and implemented in a regional or global model. Emulators can estimate the output of a model, based on a statistical analysis of outputs from simulations with known inputs. This method may reduce uncertainties in a range of cloud-scale processes, including calculations of aerosol indirect radiative effects, precipitation rates, and wet removal rates of aerosol. The Finnish Academy has recently funded the Emulation of Cloud-Aerosol Indirect Radiative Effects (ECLAIRE) project, whose aim is to construct emulators of cloud-scale processes from the WRF-Chem model and implement them into the ECHAM climate model. This poster will describe the goals and proposed methods of the project, together with any initial results.

  6. Parameterizations of Cloud Microphysics and Indirect Aerosol Effects

    Energy Technology Data Exchange (ETDEWEB)

    Tao, Wei-Kuo [NASA/GSFC

    2014-05-19

    1. OVERVIEW Aerosols and especially their effect on clouds are one of the key components of the climate system and the hydrological cycle [Ramanathan et al., 2001]. Yet, the aerosol effect on clouds remains largely unknown and the processes involved not well understood. A recent report published by the National Academy of Science states "The greatest uncertainty about the aerosol climate forcing - indeed, the largest of all the uncertainties about global climate forcing - is probably the indirect effect of aerosols on clouds [NRC, 2001]." The aerosol effect on clouds is often categorized into the traditional "first indirect (i.e., Twomey)" effect on the cloud droplet sizes for a constant liquid water path [Twomey, 1977] and the "semi-direct" effect on cloud coverage [e.g., Ackerman et al., 2000]. Enhanced aerosol concentrations can also suppress warm rain processes by producing a narrow droplet spectrum that inhibits collision and coalescence processes [e.g., Squires and Twomey, 1961; Warner and Twomey, 1967; Warner, 1968; Rosenfeld, 1999]. The aerosol effect on precipitation processes, also known as the second type of aerosol indirect effect [Albrecht, 1989], is even more complex, especially for mixed-phase convective clouds. Table 1 summarizes the key observational studies identifying the microphysical properties, cloud characteristics, thermodynamics and dynamics associated with cloud systems from high-aerosol continental environments. For example, atmospheric aerosol concentrations can influence cloud droplet size distributions, warm-rain process, cold-rain process, cloud-top height, the depth of the mixed phase region, and occurrence of lightning. In addition, high aerosol concentrations in urban environments could affect precipitation variability by providing an enhanced source of cloud condensation nuclei (CCN). Hypotheses have been developed to explain the effect of urban regions on convection and precipitation [van den Heever and Cotton, 2007 and Shepherd

  7. Modeling the Relationships Between Aerosol Properties and the Direct and Indirect Effects of Aerosols on Climate

    Science.gov (United States)

    Toon, Owen B.

    1994-01-01

    Aerosols may affect climate directly by scattering and absorbing visible and infrared energy, They may also affect climate indirectly by modifying the properties of clouds through microphysical processes, and by altering abundances of radiatively important gases through heterogeneous chemistry. Researchers understand which aerosol properties control the direct effect of aerosols on the radiation budget. Unfortunately, despite an abundance of data on certain types of aerosols, much work remains to be done to determine the values of these properties. For instance we have little idea about the global distribution, seasonal variation, or interannual variability of the aerosol optical depth. Also we do not know the visible light absorption properties of tropical aerosols which may contain much debris from slash and burn agriculture. A positive correlation between aerosol concentrations and albedos of marine stratus clouds is observed, and the causative microphysics is understood. However, models suggest that it is difficult to produce new particles in the marine boundary layer. Some modelers have suggested that the particles in the marine boundary layer may originate in the free troposphere and be transported into the boundary layer. Others argue that the aerosols are created in the marine boundary layer. There are no data linking aerosol concentration and cirrus cloud albedo, and models suggest cirrus properties may not be very sensitive to aerosol abundance. There is clear evidence of a radiatively significant change in the global lower stratospheric ozone abundance during the past few decades. These changes are caused by heterogeneous chemical reactions occurring on the surfaces of particles. The rates of these reactions depend upon the chemical composition of the particles. Although rapid advances in understanding heterogeneous chemistry have been made, much remains to be done.

  8. An investigation of Raman lidar aerosol measurements and their application to the study of the aerosol indirect effect

    Science.gov (United States)

    Russo, Felicita

    The problem of the increasing global atmospheric temperature has motivated a large interest in studying the mechanisms that can influence the radiative balance of the planet. Aerosols are responsible for several radiative effects in the atmosphere: an increase of aerosol loading in the atmosphere increases the reflectivity of the atmosphere and has an estimated cooling effect and is called the aerosol direct effect. Another process involving aerosols is the effect that an increase in their concentration in the atmosphere has on the formation of clouds and is called the aerosol indirect effect. In the latest IPCC report, the aerosol indirect effect was estimated to be responsible for a radiative forcing ranging between -0.3 W/m2 to -1.8 W/m2, which can be as large as, but opposite in sign to, the radiative forcing due to greenhouse gases. The main goal of this dissertation is to study the Raman lidar measurements of quantities relevant for the investigation of the aerosol indirect effect and ultimately to apply these measurements to a quantification of the aerosol indirect effect. In particular we explore measurements of the aerosol extinction from both the NASA Goddard Space Flight Center Scanning Raman Lidar (SRL) and the US Department of Energy (DOE) ARM Climate Research Facility Raman Lidar (CARL). An algorithm based on the chi-squared technique to calculate the aerosol extinction, which was introduced first by Whiteman (1999), is here validated using both simulated and experimental data. It has been found as part of this validation that the aerosol extinction uncertainty retrieved with this technique is on average smaller that the uncertainty calculated with the technique traditionally used. This algorithm was then used to assess the performance of the CARL aerosol extinction retrieval for low altitudes. Additionally, since CARL has been upgraded with a channel for measuring Raman liquid water scattering, measurements of cloud liquid water content, droplet

  9. On the characteristics of aerosol indirect effect based on dynamic regimes in global climate models

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, S.; Wang, Minghuai; Ghan, Steven J.; Ding, A.; Wang, Hailong; Zhang, Kai; Neubauer, David; Lohmann, U.; Ferrachat, S.; Takeamura, Toshihiko; Gettelman, A.; Morrison, H.; Lee, Y. H.; Shindell, D. T.; Partridge, Daniel; Stier, P.; Kipling, Z.; Fu, Congbin

    2016-03-04

    Aerosol-cloud interactions continue to constitute a major source of uncertainty for the estimate of climate radiative forcing. The variation of aerosol indirect effects (AIE) in climate models is investigated across different dynamical regimes, determined by monthly mean 500 hPa vertical pressure velocity (ω500), lower-tropospheric stability (LTS) and large-scale surface precipitation rate derived from several global climate models (GCMs), with a focus on liquid water path (LWP) response to cloud condensation nuclei (CCN) concentrations. The LWP sensitivity to aerosol perturbation within dynamic regimes is found to exhibit a large spread among these GCMs. It is in regimes of strong large-scale ascend (ω500 < -25 hPa/d) and low clouds (stratocumulus and trade wind cumulus) where the models differ most. Shortwave aerosol indirect forcing is also found to differ significantly among different regimes. Shortwave aerosol indirect forcing in ascending regimes is as large as that in stratocumulus regimes, which indicates that regimes with strong large-scale ascend are as important as stratocumulus regimes in studying AIE. 42" It is further shown that shortwave aerosol indirect forcing over regions with high monthly large-scale surface precipitation rate (> 0.1 mm/d) contributes the most to the total aerosol indirect forcing (from 64% to nearly 100%). Results show that the uncertainty in AIE is even larger within specific dynamical regimes than that globally, pointing to the need to reduce the uncertainty in AIE in different dynamical regimes.

  10. Examination of the aerosol indirect effect under contrasting environments during the ACE-2 experiment

    Directory of Open Access Journals (Sweden)

    H. Guo

    2007-01-01

    Full Text Available The Active Tracer High-resolution Atmospheric Model (ATHAM has been adopted to examine the aerosol indirect effect in contrasting clean and polluted cloudy boundary layers during the Second Aerosol Characterization Experiment (ACE-2. Model results are in good agreement with available in-situ observations, which provides confidence in the results of ATHAM. Sensitivity tests have been conducted to examine the response of the cloud fraction (CF, cloud liquid water path (LWP, and cloud optical depth (COD to changes in aerosols in the clean and polluted cases. It is shown for two cases that CF and LWP would decrease or remain nearly constant with an increase in aerosols, a result which shows that the second aerosol indirect effect is positive or negligibly small in these cases. Further investigation indicates that the background meteorological conditions play a critical role in the response of CF and LWP to aerosols. When large-scale subsidence is weak as in the clean case, the dry overlying air above the cloud is more efficiently entrained into the cloud, and in so doing, removes cloud water more efficiently, and results in lower CF and LWP when aerosol burden increases. However, when the large-scale subsidence is strong as in the polluted case, the growth of the cloud top is suppressed and the entrainment drying makes no significant difference when aerosol burden increases. Therefore, the CF and LWP remain nearly constant. In both the clean and polluted cases, the COD tends to increase with aerosols, and the total aerosol indirect effect (AIE is negative even when the CF and LWP decrease with an increase in aerosols. Therefore, the first AIE dominates the response of the cloud to aerosols.

  11. Cloud Condensation Nuclei Prediction Error from Application of Kohler Theory: Importance for the Aerosol Indirect Effect

    Science.gov (United States)

    Sotiropoulou, Rafaella-Eleni P.; Nenes, Athanasios; Adams, Peter J.; Seinfeld, John H.

    2007-01-01

    In situ observations of aerosol and cloud condensation nuclei (CCN) and the GISS GCM Model II' with an online aerosol simulation and explicit aerosol-cloud interactions are used to quantify the uncertainty in radiative forcing and autoconversion rate from application of Kohler theory. Simulations suggest that application of Koehler theory introduces a 10-20% uncertainty in global average indirect forcing and 2-11% uncertainty in autoconversion. Regionally, the uncertainty in indirect forcing ranges between 10-20%, and 5-50% for autoconversion. These results are insensitive to the range of updraft velocity and water vapor uptake coefficient considered. This study suggests that Koehler theory (as implemented in climate models) is not a significant source of uncertainty for aerosol indirect forcing but can be substantial for assessments of aerosol effects on the hydrological cycle in climatically sensitive regions of the globe. This implies that improvements in the representation of GCM subgrid processes and aerosol size distribution will mostly benefit indirect forcing assessments. Predictions of autoconversion, by nature, will be subject to considerable uncertainty; its reduction may require explicit representation of size-resolved aerosol composition and mixing state.

  12. Aerosol Indirect Effect on Warm Clouds over Eastern China Using Combined CALIOP and MODIS Observations

    Science.gov (United States)

    Guo, Jianping; Wang, Fu; Huang, Jingfeng; Li, Xiaowen

    2015-04-01

    Aerosol, one of key components of the climate system, is highly variable, both temporally and spatially. It often exerts great influences on the cloud-precipitation chain processes by serving as CCN/IN, altering cloud microphysics and its life cycle. Yet, the aerosol indirect effect on clouds remains largely unknown, because the initial changes in clouds due to aerosols may be enhanced or dampened by such feedback processes as modified cloud dynamics, or evaporation of the smaller droplets due to the competition for water vapor. In this study, we attempted to quantify the aerosol effects on warm cloud over eastern China, based on near-simultaneous retrievals from MODIS/AQUA, CALIOP/CALIPSO and CPR/CLOUDSAT during the period 2006 to 2010. The seasonality of aerosol from ground-based PM10 is quite different from that estimated from MODIS AOD. This result is corroborated by lower level profile of aerosol occurrence frequency from CALIOP, indicating the significant role CALIOP could play in aerosol-cloud interaction. The combined use of CALIOP and CPR facilitate the process to exactly determine the (vertical) position of warm cloud relative to aerosol, out of six scenarios in terms of aerosol-cloud mixing status in terms of aerosol-cloud mixing status, which shows as follows: AO (Aerosol only), CO (Cloud only), SASC (Single aerosol-single cloud), SADC (single aerosol-double cloud), DASC (double aerosol-single cloud), and others. Results shows that about 54% of all the cases belong to mixed status, among all the collocated aerosol-cloud cases. Under mixed condition, a boomerang shape is observed, i.e., reduced cloud droplet radius (CDR) is associated with increasing aerosol at moderate aerosol pollution (AODcaused by coal-fired heating during the cold season in China. As expected, the sensitivity of CDR to AOD is much weaker for "Separated" cases, irrespective of warm or cold seasons, indicating no real aerosol indirect effect occurring in this case. In contrast, for

  13. Sensitivity studies of different aerosol indirect effects in mixed-phase clouds

    Directory of Open Access Journals (Sweden)

    C. Hoose

    2009-11-01

    Full Text Available Aerosols affect the climate system by changing cloud characteristics. Using the global climate model ECHAM5-HAM, we investigate different aerosol effects on mixed-phase clouds: The glaciation effect, which refers to a more frequent glaciation due to anthropogenic aerosols, versus the de-activation effect, which suggests that ice nuclei become less effective because of an anthropogenic sulfate coating. The glaciation effect can partly offset the indirect aerosol effect on warm clouds and thus causes the total anthropogenic aerosol effect to be smaller. It is investigated by varying the parameterization for the Bergeron-Findeisen process and the threshold coating thickness of sulfate (SO4-crit, which is required to convert an externally mixed aerosol particle into an internally mixed particle. Differences in the net radiation at the top-of-the-atmosphere due to anthropogenic aerosols between the different sensitivity studies amount up to 0.5 W m−2. This suggests that the investigated mixed-phase processes have a major effect on the total anthropogenic aerosol effect.

  14. Sensitivity studies of different aerosol indirect effects in mixed-phase clouds

    Directory of Open Access Journals (Sweden)

    U. Lohmann

    2009-07-01

    Full Text Available Aerosols affect the climate system by changing cloud characteristics. Using the global climate model ECHAM5-HAM, we investigate different aerosol effects on mixed-phase clouds: The glaciation effect, which refers to a more frequent glaciation due to anthropogenic aerosols, versus the de-activation effect, which suggests that ice nuclei become less effective because of an anthropogenic sulfate coating. The glaciation effect can partly offset the indirect aerosol effect on warm clouds and thus causes the total anthropogenic aerosol effect to be smaller. It is investigated by varying the parameterization for the Bergeron-Findeisen process and the threshold coating thickness of sulfate (SO4-crit, which is required to convert an externally mixed aerosol particle into an internally mixed particle. Differences in the net radiation at the top-of-the-atmosphere due to anthropogenic aerosols between the different sensitivity studies amount up to 0.5 W m−2. This suggests that the investigated mixed-phase processes have a major effect on the total anthropogenic aerosol effect.

  15. Estimating the direct and indirect effects of secondary organic aerosols using ECHAM5-HAM

    Directory of Open Access Journals (Sweden)

    D. O'Donnell

    2011-08-01

    Full Text Available Secondary organic aerosol (SOA has been introduced into the global climate-aerosol model ECHAM5/HAM. The SOA module handles aerosols originating from both biogenic and anthropogenic sources. The model simulates the emission of precursor gases, their chemical conversion into condensable gases, the partitioning of semi-volatile condenable species into the gas and aerosol phases. As ECHAM5/HAM is a size-resolved model, a new method that permits the calculation of partitioning of semi-volatile species between different size classes is introduced. We compare results of modelled organic aerosol concentrations against measurements from extensive measurement networks in Europe and the United States, running the model with and without SOA. We also compare modelled aerosol optical depth against measurements from the AERONET network of grond stations. We find that SOA improves agreement between model and measurements in both organic aerosol mass and aerosol optical depth, but does not fully correct the low bias that is present in the model for both of these quantities. Although many models now include SOA, any overall estimate of the direct and indirect effects of these aerosols is still lacking. This paper makes a first step in that direction. The model is applied to estimate the direct and indirect effects of SOA under simulated year 2000 conditions. The modelled SOA spatial distribution indicates that SOA is likely to be an important source of free and upper tropospheric aerosol. We find a negative shortwave (SW forcing from the direct effect, amounting to −0.31 Wm−2 on the global annual mean. In contrast, the model indicates a positive indirect effect of SOA of +0.23 Wm−2, arising from the enlargement of particles due to condensation of SOA, together with an enhanced coagulation sink of small particles. In the longwave, model results are a direct effect of +0.02 Wm−2 and an indirect effect of −0.03 Wm−2

  16. Aerosol indirect effects -- general circulation model intercomparison and evaluation with satellite data

    Energy Technology Data Exchange (ETDEWEB)

    Quaas, Johannes; Ming, Yi; Menon, Surabi; Takemura, Toshihiko; Wang, Minghuai; Penner, Joyce E.; Gettelman, Andrew; Lohmann, Ulrike; Bellouin, Nicolas; Boucher, Olivier; Sayer, Andrew M.; Thomas, Gareth E.; McComiskey, Allison; Feingold, Graham; Hoose, Corinna; Kristjansson, Jon Egill; Liu, Xiaohong; Balkanski, Yves; Donner, Leo J.; Ginoux, Paul A.; Stier, Philip; Feichter, Johann; Sednev, Igor; Bauer, Susanne E.; Koch, Dorothy; Grainger, Roy G.; Kirkevag, Alf; Iversen, Trond; Seland, Oyvind; Easter, Richard; Ghan, Steven J.; Rasch, Philip J.; Morrison, Hugh; Lamarque, Jean-Francois; Iacono, Michael J.; Kinne, Stefan; Schulz, Michael

    2009-04-10

    Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterizes aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (Ta) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (Nd) compares relatively well to the satellite data at least over the ocean. The relationship between Ta and liquid water path is simulated much too strongly by the models. It is shown that this is partly related to the representation of the second aerosol indirect effect in terms of autoconversion. A positive relationship between total cloud fraction (fcld) and Ta as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld - Ta relationship, our results indicate that none can be identified as unique explanation. Relationships similar to the ones found in satellite data between Ta and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR - Ta relationship show a strong positive correlation between Ta and fcld The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of Ta, and parameterisation assumptions such as a lower bound on Nd

  17. Global modelling of direct and indirect effects of sea spray aerosol using a source function encapsulating wave state

    NARCIS (Netherlands)

    Partanen, A.I.; Dunne, E.M.; Bergman, T.; Laakso, A.; Kokkola, H.; Ovadnevaite, J.; Sogacheva, L.; Baisnée, D.; Sciare, J.; Manders, A.; O'Dowd, C.; Leeuw, G. de; Korhonen, H.

    2014-01-01

    Recently developed parameterizations for the sea spray aerosol source flux, encapsulating wave state, and its organic fraction were incorporated into the aerosol-climate model ECHAM-HAMMOZ to investigate the direct and indirect radiative effects of sea spray aerosol particles. Our simulated global s

  18. Indirect Radiative Warming Effect in the Winter and Spring Arctic Associated with Aerosol Pollution from Mid-latitude Regions

    Science.gov (United States)

    Zhao, Chuanfeng; Garrett, Timothy

    2016-04-01

    Different from global cooling effects of aerosols and aerosol-cloud interactions, anthropogenic aerosols from mid-latitude are found to play an increased warming effect in the Arctic in later winter and early spring. Using four-year (2000-2003) observation of aerosol, cloud and radiation at North Slope of Alaska, it is found that the aerosols can increase cloud droplet effective radius 3 um for fixed liquid water path, and increase cloud thermal emissivity about 0.05-0.08. In other words, aerosols are associated with a warming of 1-1.6 degrees (3-5 W/m2) in the Arctic during late winter and early spring solely due to their first indirect effect. Further analysis indicates that total aerosol climate effects are even more significant (8-10 W/m2), with about 50% contribution from aerosol first indirect effect and another 50% contribution from complicated feedbacks. It also shows strong seasonal distribution of the aerosol indirect radiative effects, with warming effects in seasons other than in summer. However, only the significant warming effect in winter and spring passes through the significance test. The strong warming effect due to aerosol indirect effect could be further strengthened through following feedbacks involving the surface albedo (early ice melting).

  19. Aerosol indirect effects ? general circulation model intercomparison and evaluation with satellite data

    Energy Technology Data Exchange (ETDEWEB)

    Quaas, Johannes; Ming, Yi; Menon, Surabi; Takemura, Toshihiko; Wang, Minghuai; Penner, Joyce E.; Gettelman, Andrew; Lohmann, Ulrike; Bellouin, Nicolas; Boucher, Olivier; Sayer, Andrew M.; Thomas, Gareth E.; McComiskey, Allison; Feingold, Graham; Hoose, Corinna; Kristansson, Jon Egill; Liu, Xiaohong; Balkanski, Yves; Donner, Leo J.; Ginoux, Paul A.; Stier, Philip; Grandey, Benjamin; Feichter, Johann; Sednev, Igor; Bauer, Susanne E.; Koch, Dorothy; Grainger, Roy G.; Kirkevag, Alf; Iversen, Trond; Seland, Oyvind; Easter, Richard; Ghan, Steven J.; Rasch, Philip J.; Morrison, Hugh; Lamarque, Jean-Francois; Iacono, Michael J.; Kinne, Stefan; Schulz, Michael

    2010-03-12

    Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the model explicitly parameterises aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth ({tau}{sub a}) and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (N{sub d}) compares relatively well to the satellite data at least over the ocean. The relationship between {tau}{sub a} and liquid water path is simulated much too strongly by the models. This suggests that the implementation of the second aerosol indirect effect mainly in terms of an autoconversion parameterisation has to be revisited in the GCMs. A positive relationship between total cloud fraction (f{sub cld}) and {tau}{sub a} as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong f{sub cld} - {tau}{sub a} relationship, our results indicate that none can be identified as a unique explanation. Relationships similar to the ones found in satellite data between {tau}{sub a} and cloud top temperature or outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR - {tau}{sub a} relationship show a strong positive correlation between {tau}{sub a} and f{sub cld} The short-wave total aerosol radiative forcing as simulated by the GCMs is

  20. Analytical Studies of the Cloud Droplet Spectral Dispersion Influence on the First Indirect Aerosol Effect

    Institute of Scientific and Technical Information of China (English)

    XIE Xiaoning; LIU Xiaodong

    2013-01-01

    Atmospheric aerosols (acting as cloud condensation nuclei) can enhance the cloud droplet number concentration and reduce the cloud droplet size,and in turn affect the cloud optical depth,as well as the cloud albedo,and thereby exert a radiative influence on climate (the first indirect aerosol effect).In this paper,based on various relationships between cloud droplet spectral dispersion (ε) and cloud droplet number concentration (Nc),we analytically derive the corresponding expressions of the cloud radiative forcing induced by changes in the cloud droplet number concentration.Further quantitative evaluation indicates that the cloud radiative forcing induced by aerosols for the different ε-Nc relationships varies from-29.1% to 25.2%,compared to the case without considering spectral dispersion (ε =0).Our results suggest that an accurate description of ε-Nc relationships helps to reduce the uncertainty of the first indirect aerosol effect and advances our scientific understanding of aerosol-cloud-radiation interactions.

  1. Aerosol effects on ice clouds: can the traditional concept of aerosol indirect effects be applied to aerosol-cloud interactions in cirrus clouds?

    Directory of Open Access Journals (Sweden)

    S. S. Lee

    2010-11-01

    Full Text Available Cirrus clouds cover approximately 20–25% of the globe and thus play an important role in the Earth's radiation budget. Therefore the effect of aerosols on cirrus clouds can have a substantial impact on global radiative forcing if either the ice-water path (IWP and/or the cloud ice number concentration (CINC changes. This study examines the aerosol indirect effect (AIE through changes in the CINC and IWP for a cirrus cloud case. We use a cloud-system resolving model (CSRM coupled with a double-moment representation of cloud microphysics. Intensified interactions among CINC, deposition and dynamics play a critical role in increasing the IWP as aerosols increase. Increased IWP leads to a smaller change in the outgoing LW radiation relative to that for the SW radiation for increasing aerosols. Increased aerosols lead to increased CINC, providing increased surface area for water vapor deposition. The increased deposition causes depositional heating which produces stronger updrafts, and leads to the increased IWP. The conversion of ice crystals to aggregates through autoconversion and accretion plays a negligible role in the IWP response to aerosols, and the sedimentation of aggregates is negligible. The sedimentation of ice crystals plays a more important role in the IWP response to aerosol increases than the sedimentation of aggregates, but not more than the interactions among the CINC, deposition and dynamics.

  2. Complexities in the First Aerosol Indirect Effect over the Southern Great Plains

    OpenAIRE

    Pennypacker, Sam; Steiner, Allison L.

    2016-01-01

    The aerosol first indirect effect (FIE) is typically characterized by a reduction in cloud droplet size and an increase in cloud optical thickness in the presence of high concentrations of condensation nuclei. Past studies have derived observational evidence of the FIE in specific locations and conditions, yet critical uncertainties in the validity of this conceptual model as it applies to a range of cloud types and meteorological settings remain unaddressed. We utilize five years of surface...

  3. On the characteristics of aerosol indirect effect based on dynamic regimes in global climate models

    OpenAIRE

    Zhang, Shipeng; Wang, Minghuai; Ghan, Steven J; Ding, Aijun; Wang, Hailong; Zhang, Kai; Neubauer, David; Lohmann, Ulrike; Ferrachat, Sylvaine; Takeamura, Toshihiko; Gettelman, Andrew; Morrison, Hugh; Lee, Yunha; Shindell, Drew T.; Partridge, Daniel G.

    2016-01-01

    Aerosol–cloud interactions continue to constitute a major source of uncertainty for the estimate of climate radiative forcing. The variation of aerosol indirect effects (AIE) in climate models is investigated across different dynamical regimes, determined by monthly mean 500 hPa vertical pressure velocity (ω500), lower-tropospheric stability (LTS) and large-scale surface precipitation rate derived from several global climate models (GCMs), with a focus on liquid water path (...

  4. Use of ARM Mobile Facility (AMF) Data to Study Aerosol Indirect Effects in China

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhanqing [Univ. of Maryland, College Park, MD (United States)

    2012-12-19

    General goals: 1) Facilitating the deployment of the ARM Mobile Facility (AMF) and Ancillary Facility (AAF) in China in 2008, 2) Processing, retrieving, improving and analyzing observation data from ground-based, air-borne and space-borne instruments; 3) Conducting a series of studies to gain insights into the direct and indirect effects of these aerosols on radiation, clouds, and precipitation using both

  5. Impacts of aerosol indirect effect on past and future changes in tropospheric composition

    Directory of Open Access Journals (Sweden)

    N. Unger

    2009-02-01

    Full Text Available The development of effective emissions control policies that are beneficial to both climate and air quality requires a detailed understanding of all the feedbacks in the atmospheric composition and climate system. We perform sensitivity studies with a global atmospheric composition-climate model to assess the impact of aerosols on tropospheric chemistry through their modification on clouds, the aerosol indirect effect (AIE. The model includes coupling between both tropospheric gas-phase and aerosol chemistry and aerosols and liquid-phase clouds. We investigate past impacts from preindustrial (PI to present day (PD and future impacts from PD to 2050 (for the moderate IPCC A1B scenario that embrace a wide spectrum of precursor emission changes and consequential aerosol-cloud interactions. The AIE is estimated to be −2.0 W m−2 for PD–PI and −0.6 W m−2 for 2050–PD, at the high end of current estimates. Inclusion of aerosol-cloud interactions substantially impacts changes in global mean methane lifetime across both time periods, enhancing the past and future increases by 10% and 30%, respectively. In regions where pollution emissions increase, inclusion of aerosol-cloud effects leads to 20% enhancements in in-cloud sulfate production and ~10% enhancements in sulfate wet deposition that is displaced away from the immediate source regions. The enhanced in-cloud sulfate formation leads to larger increases in surface sulfate across polluted regions (~10–30%. Nitric acid wet deposition is dampened by 15–20% across the industrialized regions due to AIE allowing additional re-release of reactive nitrogen that contributes to 1–2 ppbv increases in surface ozone in outflow regions. Our model findings indicate that aerosol-cloud interactions must be considered in studies of methane trends and projections of future changes to particulate matter air quality.

  6. Aerosol effects on ice clouds: can the traditional concept of aerosol indirect effects be applied to aerosol-cloud interactions in cirrus clouds?

    Directory of Open Access Journals (Sweden)

    S. S. Lee

    2010-04-01

    Full Text Available Cirrus clouds cover approximately 20–25% of the globe and thus play an important role in the Earth's radiation budget. This indicates that aerosol effects on cirrus clouds can have a substantial impact on the variation of global radiative forcing if the ice-water path (IWP changes. This study examines the aerosol indirect effect (AIE through changes in the IWP for a cirrus cloud case. We use a cloud-system resolving model (CSRM coupled with a double-moment representation of cloud microphysics. Intensified interactions among the cloud ice number concentration (CINC, deposition and dynamics play a critical role in the IWP increases due to aerosol increases. Increased aerosols lead to increased CINC, providing increased surface area for water vapor deposition. The increased deposition causes depositional heating which produces stronger updrafts, and leads to the increased IWP. The conversion of ice crystals to aggregates through autoconversion and accretion plays a negligible role in the IWP responses to aerosols, as the sedimentation of aggregates. The sedimentation of ice crystals plays a more important role in the IWP response to aerosol increases than the sedimentation of aggregates, but, not more important than the interactions among the CINC, deposition and dynamics.

  7. Aerosol indirect effects – general circulation model intercomparison and evaluation with satellite data

    Directory of Open Access Journals (Sweden)

    J. Quaas

    2009-06-01

    Full Text Available Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs is evaluated using three satellite datasets. The focus is on stratiform liquid water clouds since most GCMs do not include ice nucleation effects, and none of the models explicitly parameterizes aerosol effects on convective clouds. We compute statistical relationships between aerosol optical depth (τa and various cloud and radiation quantities in a manner that is consistent between the models and the satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (Nd compares relatively well to the satellite data at least over the ocean. The relationship between τa and liquid water path is simulated much too strongly by the models. It is shown that this is partly related to the representation of the second aerosol indirect effect in terms of autoconversion. A positive relationship between total cloud fraction (fcld and τa as found in the satellite data is simulated by the majority of the models, albeit less strongly than that in the satellite data in most of them. In a discussion of the hypotheses proposed in the literature to explain the satellite-derived strong fcld – τa relationship, our results indicate that none can be identified as unique explanation. Relationships similar to the ones found in satellite data between τa and cloud top temperature or outgoing long-wave radiation (OLR are simulated by only a few GCMs. The GCMs that simulate a negative OLR – τa relationship show a strong positive correlation between τa and

  8. Aerosol indirect effects – general circulation model intercomparison and evaluation with satellite data

    Energy Technology Data Exchange (ETDEWEB)

    Quaas, Johannes; Ming, Yi; Menon, Surabi; Takemura, T.; Wang, Minghuai; Penner, Joyce E.; Gettelman, A.; Lohmann, U.; Bellouin, N.; Boucher, Olivier; Sayer, Andrew M.; Thomas, Gareth E.; McComiskey, A.; Feingold, G.; Hoose, Corinna; Kristjansson, J. E.; Liu, Xiaohong; Balkanski, Y.; Donner, Leo J.; Ginoux, P.; Stier, P.; Grandey, B.; Feichter, J.; Sednev, Igor; Bauer, Susanne E.; Koch, D.; Grainger, Roy G.; Kirkevag, A.; Iversen, T.; Seland, O.; Easter, Richard C.; Ghan, Steven J.; Rasch, Philip J.; Morrison, H.; Lamarque, J. F.; Iacono, Michael J.; Kinne, Stefan; Schulz, M.

    2009-11-16

    Aerosol indirect effects continue to constitute one of the most important uncertainties for anthropogenic climate perturbations. Within the international AEROCOM initiative, the representation of aerosol-cloud-radiation interactions in ten different general circulation models (GCMs) is evaluated in the present study using three satellite datasets. The satellite datasets are taken as reference bearing in mind that cloud and aerosol retrievals include uncertainties. We compute statistical relationships between aerosol optical depth (τa) and various cloud and radiation quantities consistently in models and satellite data. It is found that the model-simulated influence of aerosols on cloud droplet number concentration (Nd) compares relatively well to the satellite data at least over oceans. The relationship between τa and liquid water path is simulated much too strongly by the models. It is shown that this is partly related to rep¬resentation of the second aerosol indirect effect in terms of autoconversion. A positive re¬lationship between total cloud fraction (fcld) and τa as found in the satellite data is simulated by the majority of the models, albeit less strongly in most of them. In a discussion of the hypo¬theses proposed in the literature to explain the satellite-derived strong fcld – τa relation¬ship, we find that none is unequivocally confirmed by our results. Relationships similar to the ones found in satellite data between τa and cloud top tem¬perature and outgoing long-wave radiation (OLR) are simulated by only a few GCMs. The GCMs that simulate a negative OLR - τa relationship show a strong positive cor¬relation between τa and cloud fraction. The short-wave total aerosol radiative forcing as simulated by the GCMs is strongly influenced by the simulated anthropogenic fraction of τa, and parameterisation assumptions such as a lower bound on Nd. Nevertheless, the strengths of the statistical relationships are good predictors for the short

  9. Evaluating WRF-Chem aerosol indirect effects in Southeast Pacific marine stratocumulus during VOCALS-REx

    Science.gov (United States)

    Saide, P. E.; Spak, S. N.; Carmichael, G. R.; Mena-Carrasco, M. A.; Howell, S.; Leon, D. C.; Snider, J. R.; Bandy, A. R.; Collett, J. L.; Benedict, K. B.; de Szoeke, S. P.; Hawkins, L. N.; Allen, G.; Crawford, I.; Crosier, J.; Springston, S. R.

    2011-11-01

    We evaluate a regional-scale simulation with the WRF-Chem model for the VAMOS (Variability of the American Monsoon Systems) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx), which sampled the Southeast Pacific's persistent stratocumulus deck. Evaluation of VOCALS-REx ship-based and aircraft observations focuses on analyzing how aerosol loading affects marine boundary layer (MBL) dynamics and cloud microphysics. We compare local time series and campaign-averaged longitudinal gradients, and highlight differences in model simulations with (W) and without wet (NW) deposition processes. The higher aerosol loadings in the NW case produce considerable changes in MBL dynamics and cloud microphysics, in accordance with the established conceptual model of aerosol indirect effects. These include increase in cloud albedo, increase in MBL and cloud heights, drizzle suppression, increase in liquid water content, and increase in cloud lifetime. Moreover, better statistical representation of aerosol mass and number concentration improves model fidelity in reproducing observed spatial and temporal variability in cloud properties, including top and base height, droplet concentration, water content, rain rate, optical depth (COD) and liquid water path (LWP). Together, these help to quantify confidence in WRF-Chem's modeled aerosol-cloud interactions, while identifying structural and parametric uncertainties including: irreversibility in rain wet removal; overestimation of marine DMS and sea salt emissions and accelerated aqueous sulfate conversion. Our findings suggest that WRF-Chem simulates marine cloud-aerosol interactions at a level sufficient for applications in forecasting weather and air quality and studying aerosol climate forcing, including the reliability required for policy analysis and geo-engineering applications.

  10. Evaluating WRF-Chem aerosol indirect effects in Southeast Pacific marine stratocumulus during VOCALS-REx

    Energy Technology Data Exchange (ETDEWEB)

    Saide, Pablo; Spak, S. N.; Carmichael, Gregory; Mena-Carrasco, M. A.; Yang, Qing; Howell, S. G.; Leon, Dolislager; Snider, Jefferson R.; Bandy, Alan R.; Collett, Jeffrey L.; Benedict, K. B.; de Szoeke, S.; Hawkins, Lisa; Allen, Grant; Crawford, I.; Crosier, J.; Springston, S. R.

    2012-03-30

    We evaluate a regional-scale simulation with the WRF-Chem model for the VAMOS (Variability of the American Monsoon Systems) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx), which sampled the Southeast Pacific's persistent stratocumulus deck. Evaluation of VOCALS-REx ship-based and aircraft observations focuses on analyzing how aerosol loading affects marine boundary layer (MBL) dynamics and cloud microphysics. We compare local time series and campaign averaged longitudinal gradients, and highlight differences in model simulations with (W) and without wet (NW) deposition processes. The higher aerosol loadings in the NW case produce considerable changes in MBL dynamics and cloud microphysics, in accordance with the established conceptual model of aerosol indirect effects. These include increase in cloud albedo, increase in MBL and cloud heights, drizzle suppression, increase in liquid water content, and increase in cloud lifetime. Moreover, better statistical representation of aerosol mass and number concentration improves model fidelity in reproducing observed spatial and temporal variability in cloud properties, including top and base height, droplet concentration, water content, rain rate, optical depth (COD) and liquid water path (LWP). Together, these help to quantify confidence in WRF-Chem's modeled aerosol-cloud interactions, while identifying structural and parametric uncertainties including: irreversibility in rain wet removal; overestimation of marine DMS and sea salt emissions and accelerated aqueous sulfate conversion. Our findings suggest that WRF-Chem simulates marine cloud-aerosol interactions at a level sufficient for applications in forecasting weather and air quality and studying aerosol climate forcing, including the reliability required for policy analysis and geo-engineering applications.

  11. Aerosol indirect effects from ground-based retrievals over the rain shadow region in Indian subcontinent

    Science.gov (United States)

    Harikishan, G.; Padmakumari, B.; Maheskumar, R. S.; Pandithurai, G.; Min, Q. L.

    2016-03-01

    Aerosol-induced changes in cloud microphysical and radiative properties have been studied for the first time using ground-based and airborne observations over a semiarid rain shadow region. The study was conducted for nonprecipitating, ice-free clouds during monsoon (July to September) and postmonsoon (October) months, when cloud condensation nuclei (CCN) concentrations over the region of interest increased monotonically and exhibited characteristics of continental origin. A multifilter rotating shadowband radiometer and microwave radiometric profiler were used to retrieve the cloud optical depth and liquid water path (LWP), respectively, from which cloud effective radius (CER) was obtained. CER showed wide variability from 10-18 µm and a decreasing trend toward the postmonsoon period. During monsoon, the estimated first aerosol indirect effect (AIE) increased from 0.01 to 0.23 with increase in LWP. AIE at different super saturations (SS) showed maximum value (significant at 95%) at 0.4% SS and higher LWP bin (250-300 g/m2). Also, statistically significant AIE values were found at 0.6% and 0.8% SSs but at lower LWP bin (200-250 g/m2). The relationship between CCN and CER showed high correlation at 0.4% SS at higher LWP bin, while at higher SSs good correlations were observed at lower LWPs. Data combined from ground-based and aircraft observations showed dominance of microphysical effect at aerosol concentrations up to 1500 cm-3 and radiative effect at higher concentrations. This combined cloud microphysical and aerosol radiative effect is more prominent during postmonsoon period due to an increase in aerosol concentration.

  12. Aerosols indirectly warm the Arctic

    Directory of Open Access Journals (Sweden)

    T. Mauritsen

    2010-07-01

    Full Text Available On average, airborne aerosol particles cool the Earth's surface directly by absorbing and scattering sunlight and indirectly by influencing cloud reflectivity, life time, thickness or extent. Here we show that over the central Arctic Ocean, where there is frequently a lack of aerosol particles upon which clouds may form, a small increase in aerosol loading may enhance cloudiness thereby likely causing a climatologically significant warming at the ice-covered Arctic surface. Under these low concentration conditions cloud droplets grow to drizzle sizes and fall, even in the absence of collisions and coalescence, thereby diminishing cloud water. Evidence from a case study suggests that interactions between aerosol, clouds and precipitation could be responsible for attaining the observed low aerosol concentrations.

  13. Study of Mechanisms of Aerosol Indirect Effects on Glaciated Clouds: Progress during the Project Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    None

    2013-10-18

    This 3-year project has studied how aerosol pollution influences glaciated clouds. The tool applied has been an 'aerosol-cloud model'. It is a type of Cloud-System Resolving Model (CSRM) modified to include 2-moment bulk microphysics and 7 aerosol species, as described by Phillips et al. (2009, 2013). The study has been done by, first, improving the model and then performing sensitivity studies with validated simulations of a couple of observed cases from ARM. These are namely the Tropical Warm Pool International Cloud Experiment (TWP-ICE) over the tropical west Pacific and the Cloud and Land Surface Interaction Campaign (CLASIC) over Oklahoma. During the project, sensitivity tests with the model showed that in continental clouds, extra liquid aerosols (soluble aerosol material) from pollution inhibited warm rain processes for precipitation production. This promoted homogeneous freezing of cloud droplets and aerosols. Mass and number concentrations of cloud-ice particles were boosted. The mean sizes of cloud-ice particles were reduced by the pollution. Hence, the lifetime of glaciated clouds, especially ice-only clouds, was augmented due to inhibition of sedimentation and ice-ice aggregation. Latent heat released from extra homogeneous freezing invigorated convective updrafts, and raised their maximum cloud-tops, when aerosol pollution was included. In the particular cases simulated in the project, the aerosol indirect effect of glaciated clouds was twice than of (warm) water clouds. This was because glaciated clouds are higher in the troposphere than water clouds and have the first interaction with incoming solar radiation. Ice-only clouds caused solar cooling by becoming more extensive as a result of aerosol pollution. This 'lifetime indirect effect' of ice-only clouds was due to higher numbers of homogeneously nucleated ice crystals causing a reduction in their mean size, slowing the ice-crystal process of snow production and slowing

  14. Anthropogenic contribution to cloud condensation nuclei and the first aerosol indirect climate effect

    International Nuclear Information System (INIS)

    Atmospheric particles influence the climate indirectly by acting as cloud condensation nuclei (CCN). The first aerosol indirect radiative forcing (FAIRF) constitutes the largest uncertainty among the radiative forcings quantified by the latest IPCC report (IPCC2007) and is a major source of uncertainty in predicting climate change. Here, we investigate the anthropogenic contribution to CCN and associated FAIRF using a state-of-the-art global chemical transport and aerosol model (GEOS-Chem/APM) that contains a number of advanced features (including sectional particle microphysics, online comprehensive chemistry, consideration of all major aerosol species, online aerosol–cloud–radiation calculation, and usage of more accurate assimilated meteorology). The model captures the absolute values and spatial distributions of CCN concentrations measured in situ around the globe. We show that anthropogenic emissions increase the global mean CCN in the lower troposphere by ∼60–80% and cloud droplet number concentration by ∼40%. The global mean FAIRF based on GEOS-Chem/APM is −0.75 W m−2, close to the median values of both IPCC2007 and post-IPCC2007 studies. To the best of our knowledge, this is the first time that a global sectional aerosol model with full online chemistry and considering all major aerosol species (including nitrate, ammonium, and second organic aerosols) has been used used to calculate FAIRF. (letter)

  15. Anthropogenic contribution to cloud condensation nuclei and the first aerosol indirect climate effect modelled by GEOS-Chem/APM

    Science.gov (United States)

    Yu, F.

    2013-05-01

    Atmospheric particles influence climate indirectly by acting as cloud condensation nuclei (CCN) that affect cloud properties (albedo, lifetime, etc.) and precipitation. The first aerosol indirect radiative forcing (FAIRF) (i.e., cloud albedo effect) constitutes the largest uncertainty among the various radiative forcings quantified by the latest IPCC assessment report (IPCC2007). In order to confidently interpret climate change over the past century and project future change, it is essential to reduce the FAIRF uncertainty. One of the large sources of the uncertainty is the poor knowledge of the number concentrations and spatial distributions of pre-industrial and present-day aerosols. All previous and recent FAIRF studies are based on global models with simplified chemistry and aerosol microphysics, which may lead to large uncertainties in predicted aerosol properties and FAIRF values. Here, we investigate the anthropogenic contribution to CCN and associated FAIRF using a state-of-the-art global chemical transport and aerosol model (GEOS-Chem/APM) that contains a number of advanced features (including size-resolved sectional particle microphysics, online comprehensive SOx-NOx-Ox-VOCs chemistry, consideration of nitrate and secondary organic aerosols, online aerosol-cloud-radiation calculation, usage of more accurate assimilated meteorology, etc.). As far as we know, this is the first time that a global model with full chemistry and size-resolved (sectional) particle microphysics is employed to study FAIRF. Key aerosol properties predicted by GEOS-Chem/APM for the present-day case have been evaluated against a large set of land-, ship-, aircraft-, and satellite- based aerosol measurements including total particle number concentrations, CCN concentrations, AODs, and vertical profiles of extinction coefficients. The GEOS-Chem/APM model, with its advanced features and ability to reproduce observed aerosol properties (including CCN) around the globe, is expected to

  16. Global modelling of direct and indirect effects of sea spray aerosol using a source function encapsulating wave state

    Directory of Open Access Journals (Sweden)

    A.-I. Partanen

    2014-02-01

    Full Text Available Recently developed parameterizations for the sea spray aerosol source flux, encapsulating wave state, and its organic fraction were incorporated into the aerosol-climate model ECHAM-HAMMOZ to investigate the direct and indirect radiative effects of sea spray aerosol particles. Our simulated global sea salt emission of 805 Tg yr−1 (uncertainty range 378–1233 Tg yr−1 was much lower than typically found in previous studies. Modelled sea salt and sodium ion concentrations agreed relatively well with measurements in the smaller size ranges at Mace Head (annual normalized mean model bias −13% for particles with vacuum aerodynamic diameter Dva Da Da Da −2, in contrast to previous studies. This positive effect was ascribed to the tendency of sea salt aerosol to suppress both the in-cloud supersaturation and the formation of cloud condensation nuclei from sulphate. These effects can be accounted for only in models with sufficiently detailed aerosol microphysics and physics-based parameterizations of cloud activation. However, due to a strong negative direct effect, the simulated effective radiative forcing (total radiative effect was −0.2 W m−2. The simulated radiative effects of the primary marine organic emissions were small, with a~direct effect of 0.03 W m−2 and an indirect effect of −0.07 W m−2.

  17. Global modelling of direct and indirect effects of sea spray aerosol using a source function encapsulating wave state

    Science.gov (United States)

    Partanen, A.-I.; Dunne, E. M.; Bergman, T.; Laakso, A.; Kokkola, H.; Ovadnevaite, J.; Sogacheva, L.; Baisnée, D.; Sciare, J.; Manders, A.; O'Dowd, C.; de Leeuw, G.; Korhonen, H.

    2014-11-01

    Recently developed parameterizations for the sea spray aerosol source flux, encapsulating wave state, and its organic fraction were incorporated into the aerosol-climate model ECHAM-HAMMOZ to investigate the direct and indirect radiative effects of sea spray aerosol particles. Our simulated global sea salt emission of 805 Tg yr-1 (uncertainty range 378-1233 Tg yr-1) was much lower than typically found in previous studies. Modelled sea salt and sodium ion concentrations agreed relatively well with measurements in the smaller size ranges at Mace Head (annual normalized mean model bias -13% for particles with vacuum aerodynamic diameter Dva sources. At the remote Amsterdam Island site, the organic concentration was underestimated especially in the biologically active months, suggesting a need to improve the parameterization of the organic sea spray fraction. Globally, the satellite-retrieved AOD over the oceans, using PARASOL data, was underestimated by the model (means over ocean 0.16 and 0.10, respectively); however, in the pristine region around Amsterdam Island the measured AOD fell well within the simulated uncertainty range. The simulated sea spray aerosol contribution to the indirect radiative effect was positive (0.3 W m-2), in contrast to previous studies. This positive effect was ascribed to the tendency of sea salt aerosol to suppress both the in-cloud supersaturation and the formation of cloud condensation nuclei from sulfate. These effects can be accounted for only in models with sufficiently detailed aerosol microphysics and physics-based parameterizations of cloud activation. However, due to a strong negative direct effect, the simulated effective radiative forcing (total radiative) effect was -0.2 W m-2. The simulated radiative effects of the primary marine organic emissions were small, with a direct effect of 0.03 W m-2 and an indirect effect of -0.07 W m-2.

  18. Attribution of the United States “warming hole”: Aerosol indirect effect and precipitable water vapor

    OpenAIRE

    Shaocai Yu; Kiran Alapaty; Rohit Mathur; Jonathan Pleim; Yuanhang Zhang; Chris Nolte; Brian Eder; Kristen Foley; Tatsuya Nagashima

    2014-01-01

    Aerosols can influence the climate indirectly by acting as cloud condensation nuclei and/or ice nuclei, thereby modifying cloud optical properties. In contrast to the widespread global warming, the central and south central United States display a noteworthy overall cooling trend during the 20th century, with an especially striking cooling trend in summertime daily maximum temperature (Tmax) (termed the U.S. “warming hole”). Here we used observations of temperature, shortwave cloud forcing (S...

  19. Exploiting the weekly cycle as observed over Europe to analyse aerosol indirect effects in two climate models

    Directory of Open Access Journals (Sweden)

    J. Quaas

    2009-05-01

    Full Text Available A weekly cycle in aerosol pollution and meteorological quantities is observed over Europe. In the present study we exploit this effect to analyse aerosol-cloud-radiation interactions. A weekly cycle is imposed on anthropogenic emissions in two general circulation models that include parameterizations of aerosol cycles and cloud microphysics. It is found that the simulated weekly cycles in sulfur dioxide, sulfate, and aerosol optical depth in both models agree reasonably well with the observed ones indicating model skill in simulating the aerosol cycle. A distinct weekly cycle in cloud droplet number concentration is demonstrated in both observations and models. For other variables, such as cloud liquid water path, cloud cover, top-of-the-atmosphere radiation fluxes, precipitation, and surface temperature, large variability and contradictory results between observations, model simulations, and model control simulations without a weekly cycle in emissions prevent us from reaching any firm conclusions about the potential aerosol impact on meteorology or the realism of the modeled second aerosol indirect effects.

  20. Global modelling of direct and indirect effects of sea spray aerosol using a source function encapsulating wave state

    Directory of Open Access Journals (Sweden)

    A.-I. Partanen

    2014-11-01

    Full Text Available Recently developed parameterizations for the sea spray aerosol source flux, encapsulating wave state, and its organic fraction were incorporated into the aerosol–climate model ECHAM-HAMMOZ to investigate the direct and indirect radiative effects of sea spray aerosol particles. Our simulated global sea salt emission of 805 Tg yr−1 (uncertainty range 378–1233 Tg yr−1 was much lower than typically found in previous studies. Modelled sea salt and sodium ion concentrations agreed relatively well with measurements in the smaller size ranges at Mace Head (annual normalized mean model bias −13% for particles with vacuum aerodynamic diameter Dva Da Da Da −2, in contrast to previous studies. This positive effect was ascribed to the tendency of sea salt aerosol to suppress both the in-cloud supersaturation and the formation of cloud condensation nuclei from sulfate. These effects can be accounted for only in models with sufficiently detailed aerosol microphysics and physics-based parameterizations of cloud activation. However, due to a strong negative direct effect, the simulated effective radiative forcing (total radiative effect was −0.2 W m−2. The simulated radiative effects of the primary marine organic emissions were small, with a direct effect of 0.03 W m−2 and an indirect effect of −0.07 W m−2.

  1. Investigation of Aerosol Indirect Effects using a Cumulus Microphysics Parameterization in a Regional Climate Model

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Kyo-Sun; Fan, Jiwen; Leung, Lai-Yung R.; Ma, Po-Lun; Singh, Balwinder; Zhao, Chun; Zhang, Yang; Zhang, Guang; Song, Xiaoliang

    2014-01-29

    A new Zhang and McFarlane (ZM) cumulus scheme includes a two-moment cloud microphysics parameterization for convective clouds. This allows aerosol effects to be investigated more comprehensively by linking aerosols with microphysical processes in both stratiform clouds that are explicitly resolved and convective clouds that are parameterized in climate models. This new scheme is implemented in the Weather Research and Forecasting (WRF) model, which is coupled with the physics and aerosol packages from the Community Atmospheric Model version 5 (CAM5). A test case of July 2008 during the East Asian summer monsoon is selected to evaluate the performance of the new ZM scheme and to investigate aerosol effects on monsoon precipitation. The precipitation and radiative fluxes simulated by the new ZM scheme show a better agreement with observations compared to simulations with the original ZM scheme that does not include convective cloud microphysics and aerosol convective cloud interactions. Detailed analysis suggests that an increase in detrained cloud water and ice mass by the new ZM scheme is responsible for this improvement. To investigate precipitation response to increased anthropogenic aerosols, a sensitivity experiment is performed that mimics a clean environment by reducing the primary aerosols and anthropogenic emissions to 30% of that used in the control simulation of a polluted environment. The simulated surface precipitation is reduced by 9.8% from clean to polluted environment and the reduction is less significant when microphysics processes are excluded from the cumulus clouds. Ensemble experiments with ten members under each condition (i.e., clean and polluted) indicate similar response of the monsoon precipitation to increasing aerosols.

  2. Potential indirect effects of aerosol on tropical cyclone intensity: convective fluxes and cold-pool activity

    Directory of Open Access Journals (Sweden)

    G. M. Krall

    2012-01-01

    pollution aerosols resulted in large amounts of condensate being thrust into the storm anvil which weakened convective downdrafts and cold-pools, yet the system did show reductions in windspeed (although weaker compared with the clean control run. This study suggests that ingestion of elevated amounts of CCN into a tropical cyclone (TC can appreciably alter the intensity of the storm. This implies that intensity prediction of TCs would be improved by including indirect aerosol affects. However, the pollution aerosols have very little impact on the storm track.

  3. Cloud-system resolving model simulations of aerosol indirect effects on tropical deep convection and its thermodynamic environment

    Directory of Open Access Journals (Sweden)

    H. Morrison

    2011-05-01

    Full Text Available This paper presents results from 240-member ensemble simulations of aerosol indirect effects on tropical deep convection and its thermodynamic environment. Simulations using a two-dimensional cloud system-resolving model are run with pristine, polluted, or highly polluted aerosol conditions and large-scale forcing from a 6-day period of active monsoon conditions during the 2006 Tropical Warm Pool – International Cloud Experiment (TWP-ICE. Domain-mean surface precipitation is insensitive to aerosols primarily because the large-scale forcing is prescribed and dominates the water and static energy budgets. The spread of the top-of-atmosphere (TOA shortwave and longwave radiative fluxes among different ensemble members for the same aerosol loading is surprisingly large, exceeding 25 W m−2 even when averaged over the 6-day period. This variability is caused by random fluctuations in the strength and timing of individual deep convective events. The ensemble approach demonstrates a small weakening of convection averaged over the 6-day period in the polluted simulations compared to pristine. Despite this weakening, the cloud top heights and anvil ice mixing ratios are higher in polluted conditions. This occurs because of the larger concentrations of cloud droplets that freeze, leading directly to higher ice particle concentrations, smaller ice particle sizes, and smaller fall velocities compared to simulations with pristine aerosols. Weaker convection in polluted conditions is a direct result of the changes in anvil ice characteristics and subsequent upper-tropospheric radiative heating and weaker tropospheric destabilization. Such a conclusion offers a different interpretation of recent satellite observations of tropical deep convection in pristine and polluted environments compared to the hypothesis of aerosol-induced convective invigoration. Sensitivity tests using the ensemble approach with modified microphysical parameters or domain

  4. Cloud-system resolving model simulations of aerosol indirect effects on tropical deep convection and its thermodynamic environment

    Directory of Open Access Journals (Sweden)

    H. Morrison

    2011-10-01

    Full Text Available This paper presents results from 240-member ensemble simulations of aerosol indirect effects on tropical deep convection and its thermodynamic environment. Simulations using a two-dimensional cloud-system resolving model are run with pristine, polluted, or highly polluted aerosol conditions and large-scale forcing from a 6-day period of active monsoon conditions during the 2006 Tropical Warm Pool – International Cloud Experiment (TWP-ICE. Domain-mean surface precipitation is insensitive to aerosols primarily because the large-scale forcing is prescribed and dominates the water and static energy budgets. The spread of the top-of-atmosphere (TOA shortwave and longwave radiative fluxes among different ensemble members for the same aerosol loading is surprisingly large, exceeding 25 W m−2 even when averaged over the 6-day period. This variability is caused by random fluctuations in the strength and timing of individual deep convective events. The ensemble approach demonstrates a small weakening of convection averaged over the 6-day period in the polluted simulations compared to pristine. Despite this weakening, the cloud top heights and anvil ice mixing ratios are higher in polluted conditions. This occurs because of the larger concentrations of cloud droplets that freeze, leading directly to higher ice particle concentrations, smaller ice particle sizes, and smaller fall velocities compared to simulations with pristine aerosols. Weaker convection in polluted conditions is a direct result of the changes in anvil ice characteristics and subsequent upper-tropospheric radiative heating and weaker tropospheric destabilization. Such a conclusion offers a different interpretation of recent satellite observations of tropical deep convection in pristine and polluted environments compared to the hypothesis of aerosol-induced convective invigoration. Sensitivity tests using the ensemble approach with modified microphysical parameters or domain

  5. Evaluating the aerosol indirect effect in WRF-Chem simulations of the January 2013 Beijing air pollution event.

    Science.gov (United States)

    Peckham, Steven; Grell, Georg; Xie, Ying; Wu, Jian-Bin

    2015-04-01

    In January 2013, an unusual weather pattern over Northern China produced unusually cool, moist conditions for the region. Recent peer-reviewed scientific manuscripts report that during this time period, Beijing experienced a historically severe haze and smog event with observed monthly average fine particulate matter (PM2.5) concentrations exceeding 225 micrograms per cubic meter. MODIS satellite observations produced AOD values of approximately 1.5 to 2 for the same time. In addition, over eastern and northern China record-breaking hourly average PM2.5 concentrations of more than 700 μg m-3 were observed. Clearly, the severity and persistence of this air pollution episode has raised the interest of the scientific community as well as widespread public attention. Despite the significance of this and similar air pollution events, several questions regarding the ability of numerical weather prediction models to forecast such events remain. Some of these questions are: • What is the importance of including aerosols in the weather prediction models? • What is the current capability of weather prediction models to simulate aerosol impacts upon the weather? • How important is it to include the aerosol feedbacks (direct and indirect effect) in the numerical model forecasts? In an attempt to address these and other questions, a Joint Working Group of the Commission for Atmospheric Sciences and the World Climate Research Programme has been convened. This Working Group on Numerical Experimentation (WGNE), has set aside several events of interest and has asked its members to generate numerical simulations of the events and examine the results. As part of this project, weather and pollution simulations were produced at the NOAA Earth System Research Laboratory using the Weather Research and Forecasting (WRF) chemistry model. These particular simulations include the aerosol indirect effect and are being done in collaboration with a group in China that will produce

  6. Oxalic acid as a heterogeneous ice nucleus in the upper troposphere and its indirect aerosol effect

    Directory of Open Access Journals (Sweden)

    B. Zobrist

    2006-05-01

    Full Text Available Heterogeneous ice freezing points of aqueous solutions containing various immersed solid dicarboxylic acids (oxalic, adipic, succinic, phthalic and fumaric have been measured with a differential scanning calorimeter. The results show that only the dihydrate of oxalic acid (OAD acts as a heterogeneous ice nucleus, with an increase in freezing temperature between 2-5 K depending on solution composition. In several field campaigns, oxalic acid enriched particles have been detected in the upper troposphere with single particle aerosol mass spectrometry. Simulations with a microphysical box model indicate that the presence of OAD may reduce the ice particle number density in cirrus clouds by up to ~50% when compared to exclusively homogeneous cirrus formation without OAD. Using the ECHAM4 climate model we estimate the global net radiative effect caused by this heterogeneous freezing to result in a cooling as high as -0.3 Wm-2.

  7. Oxalic acid as a heterogeneous ice nucleus in the upper troposphere and its indirect aerosol effect

    Directory of Open Access Journals (Sweden)

    B. Zobrist

    2006-01-01

    Full Text Available Heterogeneous ice freezing points of aqueous solutions containing various immersed solid dicarboxylic acids (oxalic, adipic, succinic, phthalic and fumaric have been measured with a differential scanning calorimeter. The results show that only the dihydrate of oxalic acid (OAD acts as a heterogeneous ice nucleus, with an increase in freezing temperature between 2 and 5 K depending on solution composition. In several field campaigns, oxalic acid enriched particles have been detected in the upper troposphere with single particle aerosol mass spectrometry. Simulations with a microphysical box model indicate that the presence of OAD may reduce the ice particle number density in cirrus clouds by up to ~50% when compared to exclusively homogeneous cirrus formation without OAD. Using the ECHAM4 climate model we estimate the global net radiative effect caused by this heterogeneous freezing to result in a cooling as high as −0.3 Wm−2.

  8. Toward a minimal representation of aerosol direct and indirect effects: model description and evaluation

    Science.gov (United States)

    Liu, X.; Easter, R. C.; Ghan, S. J.; Zaveri, R.; Rasch, P.; Shi, X.; Lamarque, J.-F.; Gettelman, A.; Morrison, H.; Vitt, F.; Conley, A.; Park, S.; Neale, R.; Hannay, C.; Ekman, A. M. L.; Hess, P.; Mahowald, N.; Collins, W.; Iacono, M. J.; Bretherton, C. S.; Flanner, M. G.; Mitchell, D.

    2011-12-01

    A modal aerosol module (MAM) has been developed for the Community Atmosphere Model version 5 (CAM5), the atmospheric component of the Community Earth System Model version 1 (CESM1). MAM is capable of simulating the aerosol size distribution and both internal and external mixing between aerosol components, treating numerous complicated aerosol processes and aerosol physical, chemical and optical properties in a physically based manner. Two MAM versions were developed: a more complete version with seven lognormal modes (MAM7), and a version with three lognormal modes (MAM3) for the purpose of long-term (decades to centuries) simulations. Major approximations in MAM3 include assuming immediate mixing of primary organic matter (POM) and black carbon (BC) with other aerosol components, merging of the MAM7 fine dust and fine sea salt modes into the accumulation mode, merging of the MAM7 coarse dust and coarse sea salt modes into the single coarse mode, and neglecting the explicit treatment of ammonia and ammonium cycles. Simulated sulfate and secondary organic aerosol (SOA) mass concentrations are remarkably similar between MAM3 and MAM7 as most (~90%) of these aerosol species are in the accumulation mode. Differences of POM and BC concentrations between MAM3 and MAM7 are also small (mostly within 10%) because of the assumed hygroscopic nature of POM, so that much of the freshly emitted POM and BC is wet-removed before mixing internally with soluble aerosol species. Sensitivity tests with the POM assumed to be hydrophobic and with slower aging increase the POM and BC concentrations, especially at high latitudes (by several times). The mineral dust global burden differs by 10% and sea salt burden by 30-40% between MAM3 and MAM7 mainly due to the different size ranges for dust and sea salt modes and different standard deviations of the log-normal size distribution for sea salt modes between MAM3 and MAM7. The model is able to qualitatively capture the observed geographical

  9. Toward a minimal representation of aerosol direct and indirect effects: model description and evaluation

    Directory of Open Access Journals (Sweden)

    X. Liu

    2011-12-01

    Full Text Available A modal aerosol module (MAM has been developed for the Community Atmosphere Model version 5 (CAM5, the atmospheric component of the Community Earth System Model version 1 (CESM1. MAM is capable of simulating the aerosol size distribution and both internal and external mixing between aerosol components, treating numerous complicated aerosol processes and aerosol physical, chemical and optical properties in a physically based manner. Two MAM versions were developed: a more complete version with seven lognormal modes (MAM7, and a version with three lognormal modes (MAM3 for the purpose of long-term (decades to centuries simulations. Major approximations in MAM3 include assuming immediate mixing of primary organic matter (POM and black carbon (BC with other aerosol components, merging of the MAM7 fine dust and fine sea salt modes into the accumulation mode, merging of the MAM7 coarse dust and coarse sea salt modes into the single coarse mode, and neglecting the explicit treatment of ammonia and ammonium cycles.

    Simulated sulfate and secondary organic aerosol (SOA mass concentrations are remarkably similar between MAM3 and MAM7 as most (~90% of these aerosol species are in the accumulation mode. Differences of POM and BC concentrations between MAM3 and MAM7 are also small (mostly within 10% because of the assumed hygroscopic nature of POM, so that much of the freshly emitted POM and BC is wet-removed before mixing internally with soluble aerosol species. Sensitivity tests with the POM assumed to be hydrophobic and with slower aging increase the POM and BC concentrations, especially at high latitudes (by several times. The mineral dust global burden differs by 10% and sea salt burden by 30–40% between MAM3 and MAM7 mainly due to the different size ranges for dust and sea salt modes and different standard deviations of the log-normal size distribution for sea salt modes between MAM3 and MAM7. The model is able to qualitatively capture the

  10. Evaluating WRF-Chem aerosol indirect effects in Southeast Pacific marine stratocumulus during VOCALS-REx

    OpenAIRE

    Saide, P.E.; S. N. Spak; Carmichael, G R; M. A. Mena-Carrasco; Howell, S.; D. C. Leon; J. R. Snider; A. R. Bandy; J. L. Collett; Benedict, K. B.; Szoeke, S. P.; L. N. Hawkins; Allen, G.; Crawford, I; J. Crosier

    2011-01-01

    We evaluate a regional-scale simulation with the WRF-Chem model for the VAMOS (Variability of the American Monsoon Systems) Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx), which sampled the Southeast Pacific's persistent stratocumulus deck. Evaluation of VOCALS-REx ship-based and aircraft observations focuses on analyzing how aerosol loading affects marine boundary layer (MBL) dynamics and cloud microphysics. We compare local time series and campaign-averaged longitud...

  11. How important is organic aerosol hygroscopicity to aerosol indirect forcing?

    International Nuclear Information System (INIS)

    Organics are among the most abundant aerosol components in the atmosphere. However, there are still large uncertainties with emissions of primary organic aerosol (POA) and volatile organic compounds (VOCs) (precursor gases of secondary organic aerosol, SOA), formation of SOA, and chemical and physical properties (e.g., hygroscopicity) of POA and SOA. All these may have significant impacts on aerosol direct and indirect forcing estimated from global models. In this study a modal aerosol module (MAM) in the NCAR community atmospheric model (CAM) is used to examine sensitivities of aerosol indirect forcing to hygroscopicity (represented by a single parameter 'κ' ) of POA and SOA. Our model simulation indicates that in the present-day (PD) condition changing the 'κ' value of POA from 0 to 0.1 increases the number concentration of cloud condensational nuclei (CCN) at supersaturation S = 0.1% by 40-80% over the POA source regions, while changing the 'κ' value of SOA by ± 50% (from 0.14 to 0.07 and 0.21) changes the CCN concentration within 40%. There are disproportionally larger changes in CCN concentration in the pre-industrial (PI) condition. Due to the stronger impact of organics hygroscopicity on CCN and cloud droplet number concentration at PI condition, global annual mean anthropogenic aerosol indirect forcing (AIF) between PD and PI conditions reduces with the increase of the hygroscopicity of organics. Global annual mean AIF varies by 0.4 W m-2 in the sensitivity runs with the control run of - 1.3 W m-2, highlighting the need for improved understanding of organics hygroscopicity and its representation in global models.

  12. Aerosol indirect effect on warm clouds over South-East Atlantic, from co-located MODIS and CALIPSO observations

    Directory of Open Access Journals (Sweden)

    L. Costantino

    2012-06-01

    Full Text Available In this study, we provide a comprehensive analysis of aerosol interaction with warm boundary layer clouds, over South-East Atlantic. We use MODIS retrievals to derive statistical relationships between aerosol concentration and cloud properties, together with co-located CALIPSO estimates of cloud and aerosol layer altitudes. The latter are used to differentiate between cases of mixed and interacting cloud-aerosol layers from cases where the aerosol is located well-above the cloud top. This strategy allows, to a certain extent, to isolate real aerosol-induced effect from meteorology.

    Similar to previous studies, statistics clearly show that aerosol affects cloud microphysics, decreasing the Cloud Droplet Radius (CDR. The same data indicate a concomitant strong decrease in cloud Liquid Water Path (LWP, in evident contrast with the hypothesis of aerosol inhibition of precipitation (Albrecht, 1989. Because of this water loss, probably due to the entrainment of dry air at cloud top, Cloud Optical Thickness (COT is found to be almost insensitive to changes in aerosol concentration. The analysis of MODIS-CALIPSO coincidences also evidenced an aerosol enhancement of low cloud cover. Surprising, the Cloud Fraction (CLF response to aerosol invigoration is much stronger when (absorbing particles are located above cloud top, than in cases of physical interaction, This result suggests a relevant aerosol radiative effect on low cloud occurrence. Heating the atmosphere above the inversion, absorbing particles above cloud top may decrease the vertical temperature gradient, increase the low tropospheric stability and provide favorable conditions for low cloud formation.

    We also focus on the impact of anthropogenic aerosols on precipitation, through the statistical analysis of CDR-COT co-variations. A COT value of 10 is found to be the threshold beyond which precipitation mostly forms, in both clean and polluted environments. For larger COT

  13. Describing the direct and indirect radiative effects of atmospheric aerosols over Europe by using coupled meteorology-chemistry simulations: a contribution from the AQMEII-Phase II exercise

    Science.gov (United States)

    Jimenez-Guerrero, Pedro; Balzarini, Alessandra; Baró, Rocío; Curci, Gabriele; Forkel, Renate; Hirtl, Marcus; Honzak, Luka; Langer, Matthias; Pérez, Juan L.; Pirovano, Guido; San José, Roberto; Tuccella, Paolo; Werhahn, Johannes; Zabkar, Rahela

    2014-05-01

    The study of the response of the aerosol levels in the atmosphere to a changing climate and how this affects the radiative budget of the Earth (direct, semi-direct and indirect effects) is an essential topic to build confidence on climate science, since these feedbacks involve the largest uncertainties nowadays. Air quality-climate interactions (AQCI) are, therefore, a key, but uncertain contributor to the anthropogenic forcing that remains poorly understood. To build confidence in the AQCI studies, regional-scale integrated meteorology-atmospheric chemistry models (i.e., models with on-line chemistry) that include detailed treatment of aerosol life cycle and aerosol impacts on radiation (direct effects) and clouds (indirect effects) are in demand. In this context, the main objective of this contribution is the study and definition of the uncertainties in the climate-chemistry-aerosol-cloud-radiation system associated to the direct radiative forcing and the indirect effect caused by aerosols over Europe, using an ensemble of fully-coupled meteorology-chemistry model simulations with the WRF-Chem model run under the umbrella of AQMEII-Phase 2 international initiative. Simulations were performed for Europe for the entire year 2010. According to the common simulation strategy, the year was simulated as a sequence of 2-day time slices. For better comparability, the seven groups applied the same grid spacing of 23 km and shared common processing of initial and boundary conditions as well as anthropogenic and fire emissions. With exception of a simulation with different cloud microphysics, identical physics options were chosen while the chemistry options were varied. Two model set-ups will be considered here: one sub-ensemble of simulations not taking into account any aerosol feedbacks (the baseline case) and another sub-ensemble of simulations which differs from the former by the inclusion of aerosol-radiation feedback. The existing differences for meteorological

  14. The effect of ENSO-induced rainfall and circulation changes on the direct and indirect radiative forcing from Indonesian biomass-burning aerosols

    Directory of Open Access Journals (Sweden)

    A. Chrastansky

    2012-12-01

    Full Text Available Emissions of biomass-burning aerosols from the Indonesian region are known to vary in response to rainfall anomalies associated with the El Niño Southern Oscillation (ENSO. For the severe El Niño-related drought in 1997, there have been several attempts to estimate the direct radiative forcing from increased aerosol emissions over Indonesia, as well as the associated feedbacks on climate. However, these estimates have not considered indirect aerosol effects. Another question that has not been addressed is whether the effect of ENSO-related circulation and rainfall anomalies on radiative forcing is significant relative to the effect of changes in emissions. In this study, we analyse the direct and first indirect radiative forcing from El Niño-related increased emissions of Indonesian biomass-burning aerosols, with and without the influence of ENSO-related rainfall and circulation anomalies.

    We compare two experiments that are performed with the CSIRO-Mk3.6 atmospheric global climate model (GCM. The first experiment (AMIP consists of a pair of runs that respectively represent El Niño and La Niña conditions. In these runs, the distribution of aerosols is simulated under the influence of realistic Indonesian biomass-burning aerosol emissions and sea surface temperatures (SSTs for 1997 (El Niño and 2000 (La Niña. The second experiment (CLIM is identical to AMIP, but is forced by climatological SSTs, so that in CLIM meteorological differences between 1997 and 2000 are suppressed.

    The comparison of AMIP and CLIM shows that the aerosol radiative forcing anomalies associated with ENSO (El Niño minus La Niña are substantially stronger when ENSO-related SST anomalies are taken into account. For the first indirect effect, the influence of SST-induced changes in rainfall and circulation exceeds that of changes in emissions. For the direct aerosol forcing, the influence of changes in SSTs and emissions are of comparable magnitude

  15. Aerosol Direct, Indirect, Semidirect, and Surface Albedo Effects from Sector Contributions Based on the IPCC AR5 Emissions for Preindustrial and Present-day Conditions

    Science.gov (United States)

    Bauer, Susanne E.; Menon, Surabi

    2012-01-01

    The anthropogenic increase in aerosol concentrations since preindustrial times and its net cooling effect on the atmosphere is thought to mask some of the greenhouse gas-induced warming. Although the overall effect of aerosols on solar radiation and clouds is most certainly negative, some individual forcing agents and feedbacks have positive forcing effects. Recent studies have tried to identify some of those positive forcing agents and their individual emission sectors, with the hope that mitigation policies could be developed to target those emitters. Understanding the net effect of multisource emitting sectors and the involved cloud feedbacks is very challenging, and this paper will clarify forcing and feedback effects by separating direct, indirect, semidirect and surface albedo effects due to aerosols. To this end, we apply the Goddard Institute for Space Studies climate model including detailed aerosol microphysics to examine aerosol impacts on climate by isolating single emission sector contributions as given by the Coupled Model Intercomparison Project Phase 5 (CMIP5) emission data sets developed for Intergovernmental Panel on Climate Change (IPCC) AR5. For the modeled past 150 years, using the climate model and emissions from preindustrial times to present-day, the total global annual mean aerosol radiative forcing is -0.6 W/m(exp 2), with the largest contribution from the direct effect (-0.5 W/m(exp 2)). Aerosol-induced changes on cloud cover often depends on cloud type and geographical region. The indirect (includes only the cloud albedo effect with -0.17 W/m(exp 2)) and semidirect effects (-0.10 W/m(exp 2)) can be isolated on a regional scale, and they often have opposing forcing effects, leading to overall small forcing effects on a global scale. Although the surface albedo effects from aerosols are small (0.016 W/m(exp 2)), triggered feedbacks on top of the atmosphere (TOA) radiative forcing can be 10 times larger. Our results point out that each

  16. Quantifying the Uncertainties of Aerosol Indirect Effects and Impacts on Decadal-Scale Climate Variability in NCAR CAM5 and CESM1

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sungsu

    2014-12-12

    The main goal of this project is to systematically quantify the major uncertainties of aerosol indirect effects due to the treatment of moist turbulent processes that drive aerosol activation, cloud macrophysics and microphysics in response to anthropogenic aerosol perturbations using the CAM5/CESM1. To achieve this goal, the P.I. hired a postdoctoral research scientist (Dr. Anna Fitch) who started her work from the Nov.1st.2012. In order to achieve the project goal, the first task that the Postdoc. and the P.I. did was to quantify the role of subgrid vertical velocity variance on the activation and nucleation of cloud liquid droplets and ice crystals and its impact on the aerosol indirect effect in CAM5. First, we analyzed various LES cases (from dry stable to cloud-topped PBL) to check whether this isotropic turbulence assumption used in CAM5 is really valid. It turned out that this isotropic turbulence assumption is not universally valid. Consequently, from the analysis of LES, we derived an empirical formulation relaxing the isotropic turbulence assumption used for the CAM5 aerosol activation and ice nucleation, and implemented the empirical formulation into CAM5/CESM1, and tested in the single-column and global simulation modes, and examined how it changed aerosol indirect effects in the CAM5/CESM1. These results were reported in the poster section in the 18th Annual CESM workshop held in Breckenridge, CO during Jun.17-20.2013. While we derived an empirical formulation from the analysis of couple of LES from the first task, the general applicability of that empirical formulation was questionable, because it was obtained from the limited number of LES simulations. The second task we did was to derive a more fundamental analytical formulation relating vertical velocity variance to TKE using other information starting from basic physical principles. This was a somewhat challenging subject, but if this could be done in a successful way, it could be directly

  17. Final Report for “Simulating the Arctic Winter Longwave Indirect Effects. A New Parameterization for Frost Flower Aerosol Salt Emissions” (DESC0006679) for 9/15/2011 through 9/14/2015

    Energy Technology Data Exchange (ETDEWEB)

    Russell, Lynn M. [Univ. of California, San Diego, CA (United States); Somerville, Richard C.J. [Univ. of California, San Diego, CA (United States); Burrows, Susannah [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Rasch, Phil [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-12-12

    Description of the Project: This project has improved the aerosol formulation in a global climate model by using innovative new field and laboratory observations to develop and implement a novel wind-driven sea ice aerosol flux parameterization. This work fills a critical gap in the understanding of clouds, aerosol, and radiation in polar regions by addressing one of the largest missing particle sources in aerosol-climate modeling. Recent measurements of Arctic organic and inorganic aerosol indicate that the largest source of natural aerosol during the Arctic winter is emitted from crystal structures, known as frost flowers, formed on a newly frozen sea ice surface [Shaw et al., 2010]. We have implemented the new parameterization in an updated climate model making it the first capable of investigating how polar natural aerosol-cloud indirect effects relate to this important and previously unrecognized sea ice source. The parameterization is constrained by Arctic ARM in situ cloud and radiation data. The modified climate model has been used to quantify the potential pan-Arctic radiative forcing and aerosol indirect effects due to this missing source. This research supported the work of one postdoc (Li Xu) for two years and contributed to the training and research of an undergraduate student. This research allowed us to establish a collaboration between SIO and PNNL in order to contribute the frost flower parameterization to the new ACME model. One peer-reviewed publications has already resulted from this work, and a manuscript for a second publication has been completed. Additional publications from the PNNL collaboration are expected to follow.

  18. Indirect radiative forcing by ion-mediated nucleation of aerosol

    Directory of Open Access Journals (Sweden)

    F. Yu

    2012-12-01

    Full Text Available A clear understanding of particle formation mechanisms is critical for assessing aerosol indirect radiative forcing and associated climate feedback processes. Recent studies reveal the importance of ion-mediated nucleation (IMN in generating new particles and cloud condensation nuclei (CCN in the atmosphere. Here we implement the IMN scheme into the Community Atmosphere Model version 5 (CAM5. Our simulations show that, compared to globally averaged results based on H2SO4-H2O binary homogeneous nucleation (BHN, the presence of ionization (i.e., IMN halves H2SO4 column burden, but increases the column integrated nucleation rate by around one order of magnitude, total particle number burden by a factor of ~3, CCN burden by ~10% (at 0.2% supersaturation to 65% (at 1.0% supersaturation, and cloud droplet number burden by ~18%. Compared to BHN, IMN increases cloud liquid water path by 7.5%, decreases precipitation by 1.1%, and increases total cloud cover by 1.9%. This leads to an increase of total shortwave cloud radiative forcing (SWCF by 3.67 W m−2 (more negative and longwave cloud forcing by 1.78 W m−2 (more positive, with large spatial variations. The effect of ionization on SWCF derived from this study (3.67 W m−2 is a factor of ~3 higher that of a previous study (1.15 W m−2 based on a different ion nucleation scheme and climate model. Based on the present CAM5 simulation, the 5-yr mean impacts of solar cycle induced changes in ionization rates on CCN and cloud forcing are small (~−0.02 W m−2 but have larger inter-annual (from −0.18 to 0.17 W m−2 and spatial variations.

  19. The effects of aerosols on climate

    International Nuclear Information System (INIS)

    Atmospheric aerosols (fine particles suspended in the atmosphere) can play two roles in the Earth’s radiation budget. In cloud-free air, aerosols scatter sunlight, some of which is reflected back to space (direct effect). Aerosols also determine the microphysical and optical properties of clouds (indirect effect). Whereas changes in natural aerosols are probably small during the last 100 years, there has been a large increase in the concentration of anthropogenic aerosols. The magnitude of their radiative effects is still very uncertain but seems to be sufficient to mask part of the global warming expected to stem from anthropogenic greenhouse gases. This paper presents the physical mechanisms of aerosol influence on climate. We then estimate the anthropogenic aerosol radiative effects and assess the climate response to these perturbations. (author)

  20. Indirect radiative forcing of aerosols via water vapor above non-precipitating maritime cumulus clouds

    Directory of Open Access Journals (Sweden)

    M. A. Pfeffer

    2011-10-01

    Full Text Available Aerosol-cloud-water vapor interactions in clean maritime air have been described for different aerosol sources using the WRF-Chem atmospheric model. The simulations were made over the Lesser Antilles in the region of the RICO measurement campaign where the clouds are low, patchy, typical trade-wind cumuli. In this very clean air, sea salt and DMS are found to have greater effects than anthropogenic pollution on the cloud droplets' effective radii and longwave and shortwave outgoing top of atmosphere radiation. The changes in radiation due to each aerosol source are a function of how each source influences aerosol concentration, cloud droplet number concentration, cloud droplet sizes, and water vapor concentration. Changes in outgoing shortwave radiation are due predominantly to changes in the clouds, followed by the direct aerosol effect which is about 2/3 as important, followed by the effects of water vapor which is in turn about 2/3 as important as the direct effect. Changes in outgoing longwave radiation are due predominantly to changes in the clouds, with changes in water vapor being about 1/10 as important. The simulated changes in water vapor concentration are due to the competing effects of aerosol particles being able to both enhance condensation of available water vapor and enhance evaporation of smaller droplets. These changes are independent of precipitation effects as there is essentially no drizzle in the domain. It is expected that the indirect radiative forcing of aerosols via water vapor may be stronger in dirtier and more strongly convective conditions.

  1. Environmental effects of indirect subsidies

    International Nuclear Information System (INIS)

    The aim of the study on the title subject is to develop a transparent integrated method to determine and analyze the environmental impacts of indirect subsidies, applied in the sectors agriculture, energy, mobility, and tourism. From the results it appears that the hazardous effects of subsidies are big. Examples are milk, the regulating energy levy, and kerosene

  2. Impacts of greenhouse gases and aerosol direct and indirect effects on clouds and radiation in atmospheric GCM simulations of the 1930-1989 period

    OpenAIRE

    Quaas, Johannes; Dufresne, Jean-Louis; Boucher, Olivier; Le Treut, Hervé

    2015-01-01

    Among anthropogenic perturbations of the Earth\\'s atmosphere, greenhouse gases and aerosols are considered to have a major impact on the energy budget through their impact on radiative fluxes. We use three ensembles of simulations with the LMDZ general circulation model to investigate the radiative impacts of five species of greenhouse gases (CO2, CH4, N2O, CFC-11 and CFC-12) and sulfate aerosols for the period 1930-1989. Since our focus is on the atmospheric changes in clouds and radiation f...

  3. Entrainment, Drizzle, and the Indirect Effect in Stratiform Clouds

    Science.gov (United States)

    Ackerman, Andrew

    2005-01-01

    Activation of some fraction of increased concentrations of sub-micron soluble aerosol particles lead to enhanced cloud droplet concentrations and hence smaller droplets, increasing their total cross sectional area and thus reflecting solar radiation more efficiently (the Twomey, or first indirect, effect). However, because of competition during condensational growth, droplet distributions tend to broaden as numbers increase, reducing the sensitivity of cloud albedo to droplet concentration on the order of 10%. Also, smaller droplets less effectively produce drizzle through collisions and coalescence, and it is widely expected (and found in large-scale models) that decreased precipitation leads to clouds with more cloud water on average (the so-called cloud lifetime, or second indirect, effect). Much of the uncertainty regarding the overall indirect aerosol effect stems from inadequate understanding of such changes in cloud water. Detailed simulations based on FIRE-I, ASTEX, and DYCOMS-II conditions show that suppression of precipitation from increased droplet concentrations leads to increased cloud water only when sufficient precipitation reaches the surface, a condition favored when the overlying air is-humid or droplet concentrations are very low. Otherwise, aerosol induced suppression of precipitation enhances entrainment of overlying dry air, thereby reducing cloud water and diminishing the indirect climate forcing.

  4. Grid-scale Indirect Radiative Forcing of Climate due to aerosols over the northern hemisphere simulated by the integrated WRF-CMAQ model: Preliminary results

    Science.gov (United States)

    In this study, indirect aerosol effects on grid-scale clouds were implemented in the integrated WRF3.3-CMAQ5.0 modeling system by including parameterizations for both cloud droplet and ice number concentrations calculated from the CMAQ-predicted aerosol particles. The resulting c...

  5. Importance of tropospheric volcanic aerosol for indirect radiative forcing of climate

    Directory of Open Access Journals (Sweden)

    A. Schmidt

    2012-03-01

    Full Text Available Observations and models have shown that continuously degassing volcanoes have a potentially large effect on the natural background aerosol loading and the radiative state of the atmosphere. Here, we use a global aerosol microphysics model to quantify the impact of these volcanic emissions on the cloud albedo radiative forcing under pre-industrial (PI and present-day (PD conditions. We find that volcanic degassing increases global annual mean cloud droplet number concentrations by 40% under PI conditions, but by only 10% under PD conditions. Consequently, volcanic degassing causes a global annual mean cloud albedo effect of −1.06 W m−2 in the PI era but only −0.56 W m−2 in the PD era. This non-equal effect is explained partly by the lower background aerosol concentrations in the PI era, but also because more aerosol particles are produced per unit of volcanic sulphur emission in the PI atmosphere. The higher sensitivity of the PI atmosphere to volcanic emissions has an important consequence for the anthropogenic cloud radiative forcing because the large uncertainty in volcanic emissions translates into an uncertainty in the PI baseline cloud radiative state. Assuming a −50/+100% uncertainty range in the volcanic sulphur flux, we estimate the annual mean anthropogenic cloud albedo forcing to lie between −1.16 W m−2 and −0.86 W m−2. Therefore, the volcanically induced uncertainty in the PI baseline cloud radiative state substantially adds to the already large uncertainty in the magnitude of the indirect radiative forcing of climate.

  6. Aerosol-cloud interactions in the NASA GMI: model development and indirect forcing assessments

    OpenAIRE

    N. Meskhidze; R. E. P. Sotiropoulou; Nenes, A.; J. Kouatchou; Das, B.; Rodriguez, J. M

    2007-01-01

    This study uses the NASA Global Modeling Initiative (GMI) 3-D chemical transport model (CTM) for assessments of indirect forcing and its sensitivity to the treatment of aerosol, aerosol-cloud interactions and meteorological fields. Three different meteorological datasets from NASA Data Assimilation Office (DAO), NASA finite volume GCM (FVGCM) and the Goddard Institute for Space Studies version II' (GISS II') GCM were used. GMI is ideal for this study as different model components (s...

  7. Can chemical effects on cloud droplet number rival the first indirect effect?

    OpenAIRE

    Nenes, Athanasios; Charlson, Robert J.; Facchini, M. Cristina; Kulmala, Markku; Laaksonen, Ari; Seinfeld, John H.

    2002-01-01

    An increase in cloud droplet number concentration resulting from an increase in ambient aerosol (and subsequent albedo increase) is typically identified as the first indirect (or “Twomey”) climatic effect of aerosols [Twomey, 1974]. A key question is whether chemical effects (dissolution of soluble gases and slightly soluble substances, surface tension depression by organic substances and accommodation coefficient changes) could potentially rival changes in droplet number from changes in aero...

  8. Indirect Network Effects in New Product Growth

    NARCIS (Netherlands)

    S. Stremersch (Stefan); G.J. Tellis (Gerard); Ph.H.B.F. Franses (Philip Hans); J.L.G. Binken (Jeroen)

    2007-01-01

    textabstractIndirect network effects are of prime interest to marketers because they affect the growth and takeoff of software availability for, and hardware sales of, a new product. While prior work on indirect network effects in the economics and marketing literature is valuable, these literatures

  9. The aerosol radiative effects of uncontrolled combustion of domestic waste

    Science.gov (United States)

    Kodros, John K.; Cucinotta, Rachel; Ridley, David A.; Wiedinmyer, Christine; Pierce, Jeffrey R.

    2016-06-01

    Open, uncontrolled combustion of domestic waste is a potentially significant source of aerosol; however, this aerosol source is not generally included in many global emissions inventories. To provide a first estimate of the aerosol radiative impacts from domestic-waste combustion, we incorporate the Wiedinmyer et al. (2014) emissions inventory into GEOS-Chem-TOMAS, a global chemical-transport model with online aerosol microphysics. We find domestic-waste combustion increases global-mean black carbon and organic aerosol concentrations by 8 and 6 %, respectively, and by greater than 40 % in some regions. Due to uncertainties regarding aerosol optical properties, we estimate the globally averaged aerosol direct radiative effect to range from -5 to -20 mW m-2; however, this range increases from -40 to +4 mW m-2 when we consider uncertainties in emission mass and size distribution. In some regions with significant waste combustion, such as India and China, the aerosol direct radiative effect may exceed -0.4 W m-2. Similarly, we estimate a cloud-albedo aerosol indirect effect of -13 mW m-2, with a range of -4 to -49 mW m-2 due to emission uncertainties. In the regions with significant waste combustion, the cloud-albedo aerosol indirect effect may exceed -0.4 W m-2.

  10. Indirect measurement of the electrocaloric effect

    OpenAIRE

    Young, James Scott

    2012-01-01

    Theoretical chapter resolving long-term dispute in thermodynamics over electrical work, followed by experimental analyses and exposure of inherent problems of indirect measurement of the electrocaloric effect, including misconceptions in electrocaloric literature and previously unexamined assumptions.

  11. Indirect Network Effects and Trade Patterns

    OpenAIRE

    Toru Kikuchi; Kazumichi Iwasa

    2007-01-01

    Indirect network effects exist when the utility of consumers is increasing in the variety of complementary products available for use with an electronic hardware device. In this note, we examine how indirect network effects work as a determinant of trade patterns. For these purposes we construct a simple two-country model of trade with incompatible country-specific hardware technologies. We show that trade patterns are determined by the interaction between hardware differentiation and indirec...

  12. Indirect Network Effects and Trade Liberalization

    OpenAIRE

    Iwasa, Kazumichi; Kikuchi, Toru

    2009-01-01

    Indirect network effects exist when the utility of consumers is increasing in the variety of complementary products available for use with an electronic hardware device. In this paper, we examine how trade liberalization affects production structure in the presence of indirect network effects. For these purposes we construct a simple two-country model of trade with incompatible country-specific hardware technologies. It is shown that, given that both countries' hardware devices remain in the ...

  13. Uncertainties in global aerosols and climate effects due to biofuel emissions

    OpenAIRE

    J. K. Kodros; Scott, C. E.; S. C. Farina; Lee, Y H; C. L'Orange; J. Volckens; Pierce, J. R.

    2015-01-01

    Aerosol emissions from biofuel combustion impact both health and climate; however, while reducing emissions through improvements to combustion technologies will improve health, the net effect on climate is largely unconstrained. In this study, we examine sensitivities in global aerosol concentration, direct radiative climate effect, and cloud-albedo aerosol indirect climate effect to uncertainties in biofuel emission factors, optical mixing-state, and model ...

  14. Indirect effects of recovery strategies

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Rice, Jake

    -based models of fish communities indicate that theserelationships have lawful dynamics that continue to be expressed, even when individualspecies become rarer - as predators or as prey. An ecosystem based management recoverystrategies of a given species or group of species should therefore not be seen......For a higher organism to grow another organism has to die. This obvious and fundamentalrelation means that if one species group increases in abundance, the prey species will sufferincreased mortality. One the other hand, the predators of said species will have a moreabundant food supply. Size...... in isolation,but the expected consequences for the rest of the ecosystem must be analyzed. We use ageneral size- and trait-based model to calculate the ecosystem effects of fishing andrecovery. We present a general analysis of a recovery strategies targeting either large fishes(consumer fishery), small fishes...

  15. Effective direct and indirect top constraints

    International Nuclear Information System (INIS)

    We use an effective field theory approach to study in a systematic way the effects of anomalous top couplings. We focus in particular on CP-violating operators and find constraints on them from direct and indirect measurements. This has important implications for new physics models and the search for their signatures at the LHC.

  16. A new chemistry option in WRF-Chem v. 3.4 for the simulation of direct and indirect aerosol effects using VBS: evaluation against IMPACT-EUCAARI data

    Science.gov (United States)

    Tuccella, P.; Curci, G.; Grell, G. A.; Visconti, G.; Crumeyrolle, S.; Schwarzenboeck, A.; Mensah, A. A.

    2015-09-01

    condensation nuclei (CCN) are also overestimated, but the bias is more contained with respect to that of CN. The CCN efficiency, which is a characterization of the ability of aerosol particles to nucleate cloud droplets, is underestimated by a factor of 1.5 and 3.8 in the PBL and FT, respectively. The comparison with MODIS data shows that the model overestimates the aerosol optical thickness (AOT). The domain averages (for 1 day) are 0.38 ± 0.12 and 0.42 ± 0.10 for MODIS and WRF-Chem data, respectively. The droplet effective radius (Re) in liquid-phase clouds is underestimated by a factor of 1.5; the cloud liquid water path (LWP) is overestimated by a factor of 1.1-1.6. The consequence is the overestimation of average liquid cloud optical thickness (COT) from a few percent up to 42 %. The predicted cloud water path (CWP) in all phases displays a bias in the range +41-80 %, whereas the bias of COT is about 15 %. In sensitivity tests where we excluded SOA, the skills of the model in reproducing the observed patterns and average values of the microphysical and optical properties of liquid and all phase clouds decreases. Moreover, the run without SOA (NOSOA) shows convective clouds with an enhanced content of liquid and frozen hydrometers, and stronger updrafts and downdrafts. Considering that the previous version of WRF-Chem coupled with a modal aerosol module predicted very low SOA content (secondary organic aerosol model (SORGAM) mechanism) the new proposed option may lead to a better characterization of aerosol-cloud feedbacks.

  17. Color indirect effects on melatonin regulation

    Science.gov (United States)

    Mian, Tian; Liu, Timon C.; Li, Yan

    2002-04-01

    Color indirect effect (CIE) is referred to as the physiological and psychological effects of color resulting from color vision. In previous papers, we have studied CIE from the viewpoints of the integrated western and Chinese traditional medicine, put forward the color-autonomic- nervous-subsystem model (CAM), and provided its time-theory foundation. In this paper, we applied it to study light effects on melatonin regulation in humans, and suggested that it is CIE that mediates light effects on melatonin suppression.

  18. Indirect radiative forcing of aerosols via water vapor above non-precipitating maritime cumulus clouds

    OpenAIRE

    Pfeffer, M.A; Kristjansson, J. E.; Stordal, F.; Berntsen, T.; J. Fast

    2011-01-01

    Aerosol-cloud-water vapor interactions in clean maritime air have been described for different aerosol sources using the WRF-Chem atmospheric model. The simulations were made over the Lesser Antilles in the region of the RICO measurement campaign where the clouds are low, patchy, typical trade-wind cumuli. In this very clean air, sea salt and DMS are found to have greater effects than anthropogenic pollution on the cloud droplets' effective radii and longwave and shortwave outgoing top of atm...

  19. Total aerosol effect: forcing or radiative flux perturbation?

    Energy Technology Data Exchange (ETDEWEB)

    Lohmann, Ulrike; Storelvmo, Trude; Jones, Andy; Rotstayn, Leon; Menon, Surabi; Quaas, Johannes; Ekman, Annica; Koch, Dorothy; Ruedy, Reto

    2009-09-25

    Uncertainties in aerosol forcings, especially those associated with clouds, contribute to a large extent to uncertainties in the total anthropogenic forcing. The interaction of aerosols with clouds and radiation introduces feedbacks which can affect the rate of rain formation. Traditionally these feedbacks were not included in estimates of total aerosol forcing. Here we argue that they should be included because these feedbacks act quickly compared with the time scale of global warming. We show that for different forcing agents (aerosols and greenhouse gases) the radiative forcings as traditionally defined agree rather well with estimates from a method, here referred to as radiative flux perturbations (RFP), that takes these fast feedbacks and interactions into account. Thus we propose replacing the direct and indirect aerosol forcing in the IPCC forcing chart with RFP estimates. This implies that it is better to evaluate the total anthropogenic aerosol effect as a whole.

  20. System markets: Indirect network effects in action, or inaction?

    NARCIS (Netherlands)

    J.L.G. Binken (Jeroen)

    2010-01-01

    textabstractIn this dissertation, I empirically examine system markets up close. More specifically I examine indirect network effects, both demand-side and supply-side indirect network effects. Indirect network effects are the source of positive feedback in system markets, or so network effect theo

  1. Indirect genetic effects and kin recognition

    DEFF Research Database (Denmark)

    Alemu, Setegn Worku; Berg, Peer; Janss, Luc;

    2014-01-01

    Social interactions among individuals are widespread, both in natural and domestic populations. As a result, trait values of individuals may be affected by genes in other individuals, a phenomenon known as indirect genetic effects (IGEs). IGEs can be estimated using linear mixed models. The...... develop models to estimate such parameters. First, we extend the definition of total breeding value and total heritable variance to cases where IGEs depend on relatedness. Next, we show that the full set of genetic parameters is not identifiable when IGEs differ between kin and strangers. Subsequently, we...... present a reduced model that yields estimates of the total heritable effects on kin, on non-kin and on all social partners of an individual, as well as the total heritable variance for response to selection. Finally we discuss the consequences of analysing data in which IGEs depend on relatedness using a...

  2. Effects of declining aerosols on projections of zonally averaged tropical precipitation

    International Nuclear Information System (INIS)

    All of the representative concentration pathways (RCPs) assume that future emissions of aerosols and aerosol precursors will decline sharply. There is considerable evidence that historically increasing aerosols have substantially affected tropical precipitation, but the effects of projected aerosol declines have received little attention. We compare projections forced by the medium-low RCP4.5 pathway in two subsets of models from the Coupled Model Intercomparison Project Phase 5 (CMIP5): one group (HiForc) includes treatments of indirect aerosol effects on cloud albedo and cloud lifetime as well as direct aerosol effects, while the other group (LoForc) only treats direct aerosol effects. In this scenario we find that models in the HiForc group consistently project larger increases in both the mean and inter-hemispheric (north minus south) asymmetry of tropical sea-surface temperature (SST) and precipitation than do models in the LoForc group. Earlier projections from CMIP3, in which future aerosol declines were assumed to be smaller, behave more like the CMIP5 LoForc group. These results show that projected tropical SST and precipitation changes are sensitive to assumptions about aerosol emissions and indirect aerosol effects. If the real world resembles the HiForc group, then future aerosol changes are likely to be an important (even dominant) driver of tropical precipitation changes under low to moderate forcing scenarios. (letter)

  3. Theoretical research on color indirect effects

    Science.gov (United States)

    Liu, T. C.; Liao, Changjun; Liu, Songhao

    1995-05-01

    Color indirect effects (CIE) means the physiological and psychological effects of color resulting from color vision. In this paper, we study CIE from the viewpoints of the integrated western and Chinese traditional medicine and the time quantum theory established by C. Y. Liu et al., respectively, and then put forward the color-automatic-nervous-subsystem model that could color excites parasympathetic subsystem and hot color excites sympathetic subsystem. Our theory is in agreement with modern color vision theory, and moreover, it leads to the resolution of the conflict between the color code theory and the time code theory oncolor vision. For the latitude phenomena on athlete stars number and the average lifespan, we also discuss the possibility of UV vision. The applications of our theory lead to our succeeding in explaining a number of physiological and psychological effects of color, in explaining the effects of age on color vision, and in explaining the Chinese chromophototherapy. We also discuss its application to neuroimmunology. This research provides the foundation of the clinical applications of chromophototherapy.

  4. The importance of interstitial particle scavenging by cloud droplets in shaping the remote aerosol size distribution and global aerosol-climate effects

    Directory of Open Access Journals (Sweden)

    J. R. Pierce

    2015-02-01

    Full Text Available In this paper, we investigate the coagulation of interstitial aerosol particles (particles too small to activate to cloud droplets with cloud drops, a process often ignored in aerosol-climate models. We use the GEOS-Chem-TOMAS global chemical transport model with aerosol microphysics to calculate the changes in the aerosol size distribution, cloud-albedo aerosol indirect effect, and direct aerosol effect due to the interstitial coagulation process. We find that inclusion of interstitial coagulation in clouds lowers total particle number concentrations by 15–21% globally, where the range is due to varying assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The interstitial coagulation process lowers the concentration of particles with dry diameters larger than 80 nm (a proxy for larger CCN by 10–12%. These 80 nm particles are not directly removed by the interstitial coagulation, but are reduced in concentration because fewer smaller particles grow to diameters larger than 80 nm. The global aerosol indirect effect of adding interstitial coagulation varies from +0.4 to +1.3 W m−2 where again the range depends on our cloud assumptions. Thus, the aerosol indirect effect of this process is significant, but the magnitude depends greatly on assumptions regarding activation diameter, cloud droplet size, and ice cloud physics. The aerosol direct effect of interstitial coagulation process is minor (−2 due to the shift in the aerosol size distribution at sizes where scattering is most effective being small. We recommend that this interstitial scavenging process be considered in aerosol models when the size distribution and aerosol indirect effects are important.

  5. System markets: Indirect network effects in action, or inaction?

    OpenAIRE

    Binken, Jeroen

    2010-01-01

    textabstractIn this dissertation, I empirically examine system markets up close. More specifically I examine indirect network effects, both demand-side and supply-side indirect network effects. Indirect network effects are the source of positive feedback in system markets, or so network effect theory tells us. Systems are composed of complementary and interdependent products, such as hardware and software. For instance, a video game system is composed of the video game console, on the one han...

  6. Indirect Effects of Environmental Change in Resource Competition Models.

    Science.gov (United States)

    Kleinhesselink, Andrew R; Adler, Peter B

    2015-12-01

    Anthropogenic environmental change can affect species directly by altering physiological rates or indirectly by changing competitive outcomes. The unknown strength of competition-mediated indirect effects makes it difficult to predict species abundances in the face of ongoing environmental change. Theory developed with phenomenological competition models shows that indirect effects are weak when coexistence is strongly stabilized, but these models lack a mechanistic link between environmental change and species performance. To extend existing theory, we examined the relationship between coexistence and indirect effects in mechanistic resource competition models. We defined environmental change as a change in resource supply points and quantified the resulting competition-mediated indirect effects on species abundances. We found that the magnitude of indirect effects increases in proportion to niche overlap. However, indirect effects also depend on differences in how competitors respond to the change in resource supply, an insight hidden in nonmechanistic models. Our analysis demonstrates the value of using niche overlap to predict the strength of indirect effects and clarifies the types of indirect effects that global change can have on competing species. PMID:26655983

  7. Reallocation in modal aerosol models: impacts on predicting aerosol radiative effects

    Directory of Open Access Journals (Sweden)

    T. Korhola

    2013-08-01

    Full Text Available In atmospheric modelling applications the aerosol particle size distribution is commonly represented by modal approach, in which particles in different size ranges are described with log-normal modes within predetermined size ranges. Such method includes numerical reallocation of particles from a mode to another for example during particle growth, leading to potentially artificial changes in the aerosol size distribution. In this study we analysed how this reallocation affects climatologically relevant parameters: cloud droplet number concentration, aerosol-cloud interaction coefficient and light extinction coefficient. We compared these parameters between a modal model with and without reallocation routines, and a high resolution sectional model that was considered as a reference model. We analysed the relative differences of the parameters in different experiments that were designed to cover a wide range of dynamic aerosol processes occurring in the atmosphere. According to our results, limiting the allowed size ranges of the modes and the following numerical remapping of the distribution by reallocation, leads on average to underestimation of cloud droplet number concentration (up to 100% and overestimation of light extinction (up to 20%. The analysis of aerosol first indirect effect is more complicated as the ACI parameter can be either over- or underestimated by the reallocating model, depending on the conditions. However, for example in the case of atmospheric new particle formation events followed by rapid particle growth, the reallocation can cause around average 10% overestimation of the ACI parameter. Thus it is shown that the reallocation affects the ability of a model to estimate aerosol climate effects accurately, and this should be taken into account when using and developing aerosol models.

  8. A new chemistry option in WRF/Chem v. 3.4 for the simulation of direct and indirect aerosol effects using VBS: evaluation against IMPACT-EUCAARI data

    Directory of Open Access Journals (Sweden)

    P. Tuccella

    2015-02-01

    Full Text Available A parameterization for secondary organic aerosol (SOA production based on the volatility basis set (VBS approach has been coupled with microphysics and radiative scheme in WRF/Chem model. The new chemistry option called "RACM/MADE/VBS" was evaluated on a cloud resolving scale against ground-based and aircraft measurements collected during the IMPACT-EUCAARI campaign, and complemented with satellite data from MODIS. The day-to-day variability and the diurnal cycle of ozone (O3 and nitrogen oxides (NOx at the surface is captured by the model. Surface aerosol mass of sulphate (SO4, nitrate (NO3, ammonium (NH4, and organic matter (OM is simulated with a correlation larger than 0.55. WRF/Chem captures the vertical profile of the aerosol mass in both the planetary boundary layer (PBL and free troposphere (FT as a function of the synoptic condition, but the model does not capture the full range of the measured concentrations. Predicted OM concentration is at the lower end of the observed mass. The bias may be attributable to the missing aqueous chemistry processes of organic compounds, the uncertainties in meteorological fields, the assumption on the deposition velocity of condensable organic vapours, and the uncertainties in the anthropogenic emissions of primary organic carbon. Aerosol particle number concentration (condensation nuclei, CN is overestimated by a factor 1.4 and 1.7 within PBL and FT, respectively. Model bias is most likely attributable to the uncertainties of primary particle emissions (mostly in the PBL and to the nucleation rate. The overestimation of simulated cloud condensation nuclei (CCN is more contained with respect to that of CN. The CCN efficiency, which is a measure of the ability of aerosol particles to nucleate cloud droplets, is underestimated by a factor of 1.5 and 3.8 in the PBL and FT, respectively. The comparison with MODIS data shows that the model overestimates the aerosol optical thickness (AOT. The domain averages

  9. Indirect Genetic Effects for group-housed animals

    DEFF Research Database (Denmark)

    Alemu, Setegn Worku

    This thesis investigated social interactions in group-housed animals. The main findings of this thesis: 1) Statistical methods to estimate indirect genetic effects when interactions differ between kin vs. non-kin were developed. 2) Indirect genetic effects contribute a substantial amount of...

  10. Aerosol effects over China investigated with a high resolution convection permitting weather model

    Science.gov (United States)

    Pagh Nielsen, Kristian; Mahura, Alexander; Yang, Xiaohua

    2016-04-01

    We investigate aerosol effects in the operational high resolution (2.5 km) convection permitting non-hydrostatical weather model HARMONIE (HIRLAM-ALADIN Regional Mesoscale Operational NWP in Euromed). Aerosol input from the global C-IFS model is downscaled and used. The impact of using realistic aerosols on both the direct and the indirect aerosol effects is studied and compared with default simulations that include only the direct aerosol effect of climatological aerosols. The study is performed as a part of the MarcoPolo FP7 project for a selected region of China during the months January and July 2010, where in particular January 2010 saw several cases of high anthropogenic aerosol loads. We also investigate the impact of accounting for realistic aerosol single scattering albedos and asymmetry factors in the simulations of the direct aerosol forcing. In many studies only variations in the aerosol optical depth are accounted for. We show this to be inadequate, when the assumed aerosol types have different optical properties than the actual aerosols.

  11. Impacts of emission reductions on aerosol radiative effects

    Science.gov (United States)

    Pietikainen, J.-P.; Kupiainen, K.; Klimont, Z.; Makkonen, R.; Korhonen, H.; Karinkanta, R.; Hyvarinen, A.-P.; Karvosenoja, N.; Laaksonen, A.; Lihavainen, H.; Kerminen, V.-M.

    2015-05-01

    The global aerosol-climate model ECHAM-HAMMOZ was used to investigate changes in the aerosol burden and aerosol radiative effects in the coming decades. Four different emissions scenarios were applied for 2030 (two of them applied also for 2020) and the results were compared against the reference year 2005. Two of the scenarios are based on current legislation reductions: one shows the maximum potential of reductions that can be achieved by technical measures, and the other is targeted to short-lived climate forcers (SLCFs). We have analyzed the results in terms of global means and additionally focused on eight subregions. Based on our results, aerosol burdens show an overall decreasing trend as they basically follow the changes in primary and precursor emissions. However, in some locations, such as India, the burdens could increase significantly. The declining emissions have an impact on the clear-sky direct aerosol effect (DRE), i.e. the cooling effect. The DRE could decrease globally 0.06-0.4 W m-2 by 2030 with some regional increases, for example, over India (up to 0.84 W m-2). The global changes in the DRE depend on the scenario and are smallest in the targeted SLCF simulation. The aerosol indirect radiative effect could decline 0.25-0.82 W m-2 by 2030. This decrease takes place mostly over the oceans, whereas the DRE changes are greatest over the continents. Our results show that targeted emission reduction measures can be a much better choice for the climate than overall high reductions globally. Our simulations also suggest that more than half of the near-future forcing change is due to the radiative effects associated with aerosol-cloud interactions.

  12. Potential climatic effects of anthropogenic aerosols

    International Nuclear Information System (INIS)

    Aerosols act as part of the climate system through their influence on solar and terrestrial radiation. The effect of anthropogenic aerosols on the reduction of visibility is explored in this chapter. Elemental carbon has been identified as the most effective visibility-reducing species. Most of the visibility reduction is due to particles with diameter smaller than 2.5 μm. Studies indicate that sulfate is also a very important aerosol species that results in low visibility and high turbidity. Radiative properties such as aerosol single-scattering albedo values and absorption-to-backscatter ratios purported to produce warming or cooling effects of aerosols are discussed. It is concluded that aerosol clouds have a tendency to cool when they are over a low-albedo surface and have a tendency to warm when they are over high-albedo surfaces such as snow. Anthropogenic aerosols have a tendency to warm the earth's atmospheric system, based on calculations and assumed aerosol optical properties. However, this effect is somewhat offset by the absorption and re-emission into space of infrared terrestrial radiation. The net effect depends on the ratio of the absorption coefficients in the visible and infrared and also on the surface albedo. The effects on infrared radiation are documented for two anthropogenic aerosol sources in the United States, the Denver metropolitan area and power plant plumes in New Mexico, through calculations and measurements. Measured cooling rates within an aerosol plume are not sufficient to offset the warming rate due to absorption of short-wave radiation. Research indicates that anthropogenic aerosols can possibly cause local-scale warming of the atmosphere, but global-scale climatic effects remain an open question

  13. Climatic effects of 1950–2050 changes in US anthropogenic aerosols – Part 1: Aerosol trends and radiative forcing

    Directory of Open Access Journals (Sweden)

    D. G. Streets

    2012-04-01

    Full Text Available We calculate decadal aerosol direct and indirect (warm cloud radiative forcings from US anthropogenic sources over the 1950–2050 period. Past and future aerosol distributions are constructed using GEOS-Chem and historical emission inventories and future projections from the IPCC A1B scenario. Aerosol simulations are evaluated with observed spatial distributions and 1980–2010 trends of aerosol concentrations and wet deposition in the contiguous US. Direct and indirect radiative forcing is calculated using the GISS general circulation model and monthly mean aerosol distributions from GEOS-Chem. The radiative forcing from US anthropogenic aerosols is strongly localized over the eastern US. We find that its magnitude peaked in 1970–1990, with values over the eastern US (east of 100° W of −2.0 W m−2 for direct forcing including contributions from sulfate (−2.0 W m−2, nitrate (−0.2 W m−2, organic carbon (−0.2 W m−2, and black carbon (+0.4 W m−2. The uncertainties in radiative forcing due to aerosol radiative properties are estimated to be about 50%. The aerosol indirect effect is estimated to be of comparable magnitude to the direct forcing. We find that the magnitude of the forcing declined sharply from 1990 to 2010 (by 0.8 W m−2 direct and 1.0 W m−2 indirect, mainly reflecting decreases in SO2 emissions, and project that it will continue declining post-2010 but at a much slower rate since US SO2 emissions have already declined by almost 60% from their peak. This suggests that much of the warming effect of reducing US anthropogenic aerosol sources has already been realized. The small positive radiative forcing from US BC emissions (+0.3 W m−2 over the eastern US in 2010; 5% of the global forcing from anthropogenic BC emissions worldwide suggests that a US emission control strategy focused on BC would have only limited climate benefit.

  14. Distributions and climate effects of atmospheric aerosols from the preindustrial era to 2100 along Representative Concentration Pathways (RCPs simulated using a global aerosol model SPRINTARS

    Directory of Open Access Journals (Sweden)

    T. Takemura

    2012-08-01

    Full Text Available Global distributions and associated climate effects of atmospheric aerosols were simulated using a global aerosol climate model, SPRINTARS, from 1850 to the present day and projected forward to 2100. Aerosol emission inventories used by the Coupled Model Intercomparison Project Phase 5 (CMIP5 were applied to this study. Scenarios based on the Representative Concentration Pathways (RCPs were used for the future projection. Aerosol loading in the atmosphere has already peaked and is now reducing in Europe and North America. However, in Asia where rapid economic growth is ongoing, aerosol loading is estimated to reach a maximum in the first half of this century. Atmospheric aerosols originating from the burning of biomass have maintained high loadings throughout the 21st century in Africa, according to the RCPs. Evolution of the adjusted forcing by direct and indirect aerosol effects over time generally correspond to the aerosol loading. The probable future pathways of global mean forcing differ based on the aerosol direct effect for different RCPs. Because aerosol forcing will be close to the preindustrial level by the end of the 21st century for all RCPs despite the continuous increases in greenhouse gases, global warming will be accelerated with reduced aerosol negative forcing.

  15. Distributions and climate effects of atmospheric aerosols from the preindustrial era to 2100 along Representative Concentration Pathways (RCPs simulated using the global aerosol model SPRINTARS

    Directory of Open Access Journals (Sweden)

    T. Takemura

    2012-12-01

    Full Text Available Global distributions and associated climate effects of atmospheric aerosols were simulated using a global aerosol climate model, SPRINTARS, from 1850 to the present day and projected forward to 2100. Aerosol emission inventories used by the Coupled Model Intercomparison Project Phase 5 (CMIP5 were applied to this study. Scenarios based on the Representative Concentration Pathways (RCPs were used for the future projection. Aerosol loading in the atmosphere has already peaked and is now reducing in Europe and North America. However, in Asia where rapid economic growth is ongoing, aerosol loading is estimated to reach a maximum in the first half of this century. Atmospheric aerosols originating from the burning of biomass have maintained high loadings throughout the 21st century in Africa, according to the RCPs. Evolution of the adjusted forcing by direct and indirect aerosol effects over time generally correspond to the aerosol loading. The probable future pathways of global mean forcing differ based on the aerosol direct effect for different RCPs. Because aerosol forcing will be close to the preindustrial level by the end of the 21st century for all RCPs despite the continuous increases in greenhouse gases, global warming will be accelerated with reduced aerosol negative forcing.

  16. Indirect Network Effects, Trade Liberalization, and Excess Standardization

    OpenAIRE

    Iwasa, Kazumichi; Kikuchi, Toru

    2007-01-01

    Indirect network effects exist when the utility of consumers is increasing in the variety of complementary software products available for use with an electronic hardware device. In this study, we examine how trade liberalization affects production structure in the presence of indirect network effects. For these purposes we construct a simple two-country model of trade with two incompatible hardware technologies. It is shown that, given that both types of hardware exist before trade liberaliz...

  17. Effects of absorbing aerosols in cloudy skies: a satellite study over the Atlantic Ocean

    Directory of Open Access Journals (Sweden)

    K. Peters

    2009-10-01

    Full Text Available Aerosol effects, direct as well as indirect, constitute one of the biggest sources of uncertainty when it comes to quantifying human forcing of climate change. Understanding these will thus increase the credibility of climate predictions. This study focuses on aerosol effects when absorbing aerosols reside in cloudy skies. In cloudfree conditions, aerosols usually exert a negative radiative forcing (RF at the top of the atmosphere (TOA due to their scattering properties. When located above clouds, absorbing aerosols can reduce the shortwave local planetary albedo α, resulting in an often significant local positive direct radiative forcing (DRF. A method for deriving the aerosol radiative effects of absorbing aerosols in cloudy situations from satellite retrievals is presented. Data of 2005 and 2006 from various sensors aboard satellites of the "A-Train" constellation, restricted to the tropical and subtropical Atlantic ocean, is used. A multiple linear regression is performed to identify the dependence of α in cloudy scenes on cloud liquid water path (LWP and aerosol optical depth (AOD, using the OMI UV-Aerosolindex (UV-AI as an indicator for absorbing aerosols. The results show an increase of α with increasing aerosol load, and a relative decrease of α with increasing amount of absorbing aerosols in cloudy scenes. This allows to derive the direct aerosol effect of absorbing aerosols above clouds, with the effect of aerosol absorption over clouds in the Atlantic contributing +0.08±1.2×10-3Wm-2 to the global TOA RF.

  18. Climatology Analysis of Aerosol Effect on Marine Water Cloud from Long-Term Satellite Climate Data Records

    OpenAIRE

    Xuepeng Zhao; Andrew K. Heidinger; Andi Walther

    2016-01-01

    Satellite aerosol and cloud climate data records (CDRs) have been used successfully to study the aerosol indirect effect (AIE). Data from the Advanced Very High Resolution Radiometer (AVHRR) now span more than 30 years and allow these studies to be conducted from a climatology perspective. In this paper, AVHRR data are used to study the AIE on water clouds over the global oceans. Correlation analysis between aerosol optical thickness (AOT) and cloud parameters, including cloud droplet effecti...

  19. Uncertainties in global aerosols and climate effects due to biofuel emissions

    Directory of Open Access Journals (Sweden)

    J. K. Kodros

    2015-04-01

    Full Text Available Aerosol emissions from biofuel combustion impact both health and climate; however, while reducing emissions through improvements to combustion technologies will improve health, the net effect on climate is largely unconstrained. In this study, we examine sensitivities in global aerosol concentration, direct radiative climate effect, and cloud-albedo aerosol indirect climate effect to uncertainties in biofuel emission factors, optical mixing-state, and model nucleation and background SOA. We use the Goddard Earth Observing System global chemical-transport model (GEOS-Chem with TwO Moment Aerosol Sectional (TOMAS microphysics. The emission factors include: amount, composition, size and hygroscopicity, as well as optical mixing-state properties. We also evaluate emissions from domestic coal use, which is not biofuel but is also frequently emitted from homes. We estimate the direct radiative effect assuming different mixing states (internal, core-shell, and external with and without absorptive organic aerosol (brown carbon. We find the global-mean direct radiative effect of biofuel emissions ranges from −0.02 to +0.06 W m−2 across all simulation/mixing state combinations with regional effects in source regions ranging from −0.2 to +1.2 W m−2. The global-mean cloud-albedo aerosol indirect effect ranges from +0.01 to −0.02 W m−2 with regional effects in source regions ranging from −1.0 to −0.05 W m−2. The direct radiative effect is strongly dependent on uncertainties in emissions mass, composition, emissions aerosol size distributions and assumed optical mixing state, while the indirect effect is dependent on the emissions mass, emissions aerosol size distribution and the choice of model nucleation and secondary organic aerosol schemes. The sign and magnitude of these effects have a strong regional dependence. We conclude that the climate effects of biofuel aerosols are largely unconstrained, and the overall sign of the aerosol

  20. Impacts of emission reductions on aerosol radiative effects

    Directory of Open Access Journals (Sweden)

    J.-P. Pietikäinen

    2015-05-01

    Full Text Available The global aerosol–climate model ECHAM-HAMMOZ was used to investigate changes in the aerosol burden and aerosol radiative effects in the coming decades. Four different emissions scenarios were applied for 2030 (two of them applied also for 2020 and the results were compared against the reference year 2005. Two of the scenarios are based on current legislation reductions: one shows the maximum potential of reductions that can be achieved by technical measures, and the other is targeted to short-lived climate forcers (SLCFs. We have analyzed the results in terms of global means and additionally focused on eight subregions. Based on our results, aerosol burdens show an overall decreasing trend as they basically follow the changes in primary and precursor emissions. However, in some locations, such as India, the burdens could increase significantly. The declining emissions have an impact on the clear-sky direct aerosol effect (DRE, i.e. the cooling effect. The DRE could decrease globally 0.06–0.4 W m−2 by 2030 with some regional increases, for example, over India (up to 0.84 W m−2. The global changes in the DRE depend on the scenario and are smallest in the targeted SLCF simulation. The aerosol indirect radiative effect could decline 0.25–0.82 W m−2 by 2030. This decrease takes place mostly over the oceans, whereas the DRE changes are greatest over the continents. Our results show that targeted emission reduction measures can be a much better choice for the climate than overall high reductions globally. Our simulations also suggest that more than half of the near-future forcing change is due to the radiative effects associated with aerosol–cloud interactions.

  1. Phenylketonuria: Direct and indirect effects of phenylalanine.

    Science.gov (United States)

    Schlegel, Gudrun; Scholz, Ralf; Ullrich, Kurt; Santer, René; Rune, Gabriele M

    2016-07-01

    High phenylalanine concentrations in the brain due to dysfunctional phenylalanine hydroxylase (Pah) are considered to account for mental retardation in phenylketonuria (PKU). In this study, we treated hippocampal cultures with the amino acid in order to determine the role of elevated levels of phenylalanine in PKU-related mental retardation. Synapse density and dendritic length were dramatically reduced in hippocampal cultures treated with phenylalanine. Changes in cofilin expression and phosphorylation status, which were restored by NMDA, as well as reduced activation of the small GTPase Rac1, likely underlie these structural alterations. In the Pah(enu2) mouse, which carries a mutated Pah gene, we previously found higher synaptic density due to delayed synaptic pruning in response to insufficient microglia function. Microglia activity and C3 complement expression, both of which were reduced in the Pah(enu2) mouse, however, were unaffected in hippocampal cultures treated with phenylalanine. The lack of a direct effect of phenylalanine on microglia is the key to the opposite effects regarding synapse stability in vitro and in the Pah(enu2) mouse. Judging from our data, it appears that another player is required for the inactivation of microglia in the Pah(enu2) mouse, rather than high concentrations of phenylalanine alone. Altogether, the data underscore the necessity of a lifelong phenylalanine-restricted diet. PMID:27091224

  2. Effect of aerosol sub-grid variability on aerosol optical depth and cloud condensation nuclei: Implications for global aerosol modelling

    OpenAIRE

    Weigum, N; Schutgens, N.; Stier, P.

    2016-01-01

    A fundamental limitation of grid-based models is their inability to resolve variability on scales smaller than a grid box. Past research has shown that significant aerosol variability exists on scales smaller than these grid-boxes, which can lead to discrepancies in simulated aerosol climate effects between high and low resolution models. This study investigates the impact of neglecting sub-grid variability in present-day global microphysical aerosol models on aerosol optical depth (AOD) and ...

  3. An on-line modelling study of the direct effect of atmospheric aerosols over Europe

    International Nuclear Information System (INIS)

    Atmospheric aerosols affect human health, ecosystems, materials, visibility and Earths climate. Those effects are studied in this present work and depend mainly on the aerosol optical properties and how they influence the Earths radiation budget. Such properties can be divided on direct and semi-direct effect, produced by the scattering and absorption of radiation; and indirect effect, which influences the aerosols-cloud interactions. The aim of this work is to assess the direct effect through the study of the mean temperature; the radiation that reaches the Earths surface and at the top of the atmosphere; and the interaction of these meteorological variables with particulate matter (PM10). Results indicate decreases in temperature and radiation that reaches the Earth's surface, together with increases in the outgoing radiation at top of the atmosphere, and changes in the particulate matter, thus proving a colder climate due to the direct effect of atmospheric aerosols. (Author)

  4. Effect of Increasing Temperature on Carbonaceous Aerosol Direct Radiative Effect over Southeastern US

    Science.gov (United States)

    Mielonen, Tero; Kokkola, Harri; Hienola, Anca; Kühn, Thomas; Merikanto, Joonas; Korhonen, Hannele; Arola, Antti; Kolmonen, Pekka; Sogacheva, Larisa; de Leeuw, Gerrit

    2016-04-01

    Aerosols are an important regulator of the Earth's climate. They scatter and absorb incoming solar radiation and thus cool the climate by reducing the amount of energy reaching the atmospheric layers and the surface below (direct effect). A certain subset of the particles can also act as initial formation sites for cloud droplets and thereby modify the microphysics, dynamics, radiative properties and lifetime of clouds (indirect effects). The magnitude of aerosol radiative effects remains the single largest uncertainty in current estimates of anthropogenic radiative forcing. One of the key quantities needed for accurate estimates of anthropogenic radiative forcing is an accurate estimate of the radiative effects from natural unperturbed aerosol. The dominant source of natural aerosols over Earth's vast forested regions are biogenic volatile organic compounds (BVOC) which, following oxidation in the atmosphere, can condense onto aerosol particles to form secondary organic aerosol (SOA) and significantly modify the particles' properties. In accordance with the expected positive temperature dependence of BVOC emissions, several previous studies have shown that some aerosol properties, such as mass concentration and ability to act as cloud condensation nuclei (CCN), also correlate positively with temperature at many forested sites. There is conflicting evidence as to whether the aerosol direct effects have a temperature dependence due to increased BVOC emissions. The main objective of this study is to investigate the causes of the observed effect of increasing temperatures on the aerosol direct radiative effect, and to provide a quantitative estimate of this effect and of the resulting negative feedback in a warming climate. More specifically, we will investigate the causes of the positive correlation between aerosol optical depth (AOD) and land surface temperature (LST) over southeastern US where biogenic emissions are a significant source of atmospheric particles. In

  5. Longwave indirect effect of mineral dusts on ice clouds

    Directory of Open Access Journals (Sweden)

    Q. Min

    2010-08-01

    Full Text Available In addition to microphysical changes in clouds, changes in nucleation processes of ice cloud due to aerosols would result in substantial changes in cloud top temperature as mildly supercooled clouds are glaciated through heterogenous nucleation processes. Measurements from multiple sensors on multiple observing platforms over the Atlantic Ocean show that the cloud effective temperature increases with mineral dust loading with a slope of +3.06 °C per unit aerosol optical depth. The macrophysical changes in ice cloud top distributions as a consequence of mineral dust-cloud interaction exert a strong cooling effect (up to 16 Wm−2 of thermal infrared radiation on cloud systems. Induced changes of ice particle size by mineral dusts influence cloud emissivity and play a minor role in modulating the outgoing longwave radiation for optically thin ice clouds. Such a strong cooling forcing of thermal infrared radiation would have significant impacts on cloud systems and subsequently on climate.

  6. From nanoclusters to climate forcers. Global modeling of aerosol climate effects

    Energy Technology Data Exchange (ETDEWEB)

    Makkonen, R.

    2012-11-01

    Atmospheric aerosol particles influence everyday life through their adverse health effects. Aerosols also affect the Earth's climate, directly by scattering and absorbing radiation and indirectly by acting as cloud condensation nuclei (CCN) and modifying cloud properties. The net effect of aerosols on climate is cooling. Although only a small fraction of atmospheric aerosol mass is of direct human origin, the anthropogenic aerosol climate forcing can be of same magnitude, but opposite in sign, as the anthropogenic forcing via CO{sub 2}. As aerosols are short-lived and respond rapidly to changes in emissions, they are an important factor in determining the future climate change. Aerosols are either emitted as primary particles or they are formed from gas-phase precursors. Atmospheric new particle formation is observed around the world. In this thesis, new particle formation is studied with a global aerosol-climate model. Several thermodynamic and semi- empirical parameterizations of nucleation are investigated. It is shown that in addition to the thermodynamic models, semi-empirical parameterizations are needed to explain the observed aerosol number concentrations. Volatile organic compounds (VOCs) can contribute to particle number, particle growth, and total aerosol mass. It was shown that biogenic VOCs have an important role in growing the freshly-nucleated particles to sizes capable of acting as CCN. It was also shown that the current atmospheric concentrations of nitric acid can greatly affect cloud droplet activation and increase the number of cloud droplets, making a large contribution to the indirect aerosols effect. With current scenarios for anthropogenic SO{sub 2} emissions, the formation of new particles will diminish significantly by the year 2100. Together with the predicted reductions in primary particles, the future cloud droplet number concentrations were shown to decrease close to pre-industrial levels. As a result, the anthropogenic aerosol

  7. Impact of the 1783-84 AD Laki Eruption on Cloud Condensation Nuclei, Cloud Droplet Concentrations and Aerosol Indirect Radiative Forcing

    Science.gov (United States)

    Schmidt, Anja; Mann, Graham; Carslaw, Kenneth; Wilson, Marjorie; Breider, Thomas; Thordarson, Thorvaldur; Forster, Piers

    2010-05-01

    The 1783-84 AD Laki flood lava eruption commenced on 8 June 1783 and released 122 Tg of sulphur dioxide gas over the course of 8 months into the upper troposphere and lower stratosphere above Iceland. Previous studies have examined the impact of the Laki eruption on sulphate aerosol and climate using general circulation models. Here, we study the impact on aerosol microphysical processes, including the nucleation of new particles, their growth to cloud condensation nuclei (CCN) and their subsequent activation into cloud droplets using a comprehensive global aerosol microphysics model (GLOMAP-mode). Our simulations show that the microphysical processes leading to the growth of particles to CCN sizes are fundamentally different during and after the eruption when compared to the unperturbed atmosphere. The simulations suggest that the Laki eruption completely dominated as a source of CCN in the pre-industrial atmosphere by increasing 3-month mean concentrations by up to a factor 65 in the upper troposphere. Averaged over the Northern Hemisphere, the eruption caused a factor 4 increase in CCN concentrations at low-level cloud altitude. The impact on CCN is very widespread, with CCN concentrations increasing by a factor ~6 in Europe and by a factor >14 in Asia due to the long range transport of nucleated particles. The impact on CCN and subsequently on cloud droplet number (CDN) concentrations is most substantial in the Northern Hemisphere. However, our simulations indicate that the Laki eruption can significantly affect CCN concentrations in the Southern Hemisphere. At 20S, the eruption increases CCN concentrations at low level cloud altitude by up to 35 cm-3 (factor 1.4). Although the mass of sulphate is quite small far from the eruption, it is present in a large number of small particles that are very effective CCN. We also show that there is a widespread impact of the Laki eruption on CDN concentrations and indirect forcing, which extends into the Southern

  8. Effective dose from direct and indirect digital panoramic units

    International Nuclear Information System (INIS)

    This study aimed to provide comparative measurements of the effective dose from direct and indirect digital panoramic units according to phantoms and exposure parameters. Dose measurements were carried out using a head phantom representing an average man (175 cm tall, 73.5 kg male) and a limbless whole body phantom representing an average woman (155 cm tall, 50 kg female). Lithium fluoride thermoluminescent dosimeter (TLD) chips were used for the dosimeter. Two direct and 2 indirect digital panoramic units were evaluated in this study. Effective doses were derived using 2007 International Commission on Radiological Protection (ICRP) recommendations. The effective doses of the 4 digital panoramic units ranged between 8.9 μSv and 37.8 μSv. By using the head phantom, the effective doses from the direct digital panoramic units (37.8 μSv, 27.6 μSv) were higher than those from the indirect units (8.9 μSv, 15.9 μSv). The same panoramic unit showed the difference in effective doses according to the gender of the phantom, numbers and locations of TLDs, and kVp. To reasonably assess the radiation risk from various dental radiographic units, the effective doses should be obtained with the same numbers and locations of TLDs, and with standard hospital exposure. After that, it is necessary to survey the effective doses from various dental radiographic units according to the gender with the corresponding phantom.

  9. Effective dose from direct and indirect digital panoramic units

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Gun Sun; Kim, Jin Soo; Seo, Yo Seob; Kim, Jae Duk [School of Dentistry, Oral Biology Research Institute, Chosun University, Gwangju (Korea, Republic of)

    2013-06-15

    This study aimed to provide comparative measurements of the effective dose from direct and indirect digital panoramic units according to phantoms and exposure parameters. Dose measurements were carried out using a head phantom representing an average man (175 cm tall, 73.5 kg male) and a limbless whole body phantom representing an average woman (155 cm tall, 50 kg female). Lithium fluoride thermoluminescent dosimeter (TLD) chips were used for the dosimeter. Two direct and 2 indirect digital panoramic units were evaluated in this study. Effective doses were derived using 2007 International Commission on Radiological Protection (ICRP) recommendations. The effective doses of the 4 digital panoramic units ranged between 8.9 {mu}Sv and 37.8 {mu}Sv. By using the head phantom, the effective doses from the direct digital panoramic units (37.8 {mu}Sv, 27.6 {mu}Sv) were higher than those from the indirect units (8.9 {mu}Sv, 15.9 {mu}Sv). The same panoramic unit showed the difference in effective doses according to the gender of the phantom, numbers and locations of TLDs, and kVp. To reasonably assess the radiation risk from various dental radiographic units, the effective doses should be obtained with the same numbers and locations of TLDs, and with standard hospital exposure. After that, it is necessary to survey the effective doses from various dental radiographic units according to the gender with the corresponding phantom.

  10. Indirect estimation of absorption properties for fine aerosol particles using AATSR observations: a case study of wildfires in Russia in 2010

    Science.gov (United States)

    Rodriguez, E.; Kolmonen, P.; Virtanen, T. H.; Sogacheva, L.; Sundstrom, A.-M.; de Leeuw, G.

    2015-08-01

    The Advanced Along-Track Scanning Radiometer (AATSR) on board the ENVISAT satellite is used to study aerosol properties. The retrieval of aerosol properties from satellite data is based on the optimized fit of simulated and measured reflectances at the top of the atmosphere (TOA). The simulations are made using a radiative transfer model with a variety of representative aerosol properties. The retrieval process utilizes a combination of four aerosol components, each of which is defined by their (lognormal) size distribution and a complex refractive index: a weakly and a strongly absorbing fine-mode component, coarse mode sea salt aerosol and coarse mode desert dust aerosol). These components are externally mixed to provide the aerosol model which in turn is used to calculate the aerosol optical depth (AOD). In the AATSR aerosol retrieval algorithm, the mixing of these components is decided by minimizing the error function given by the sum of the differences between measured and calculated path radiances at 3-4 wavelengths, where the path radiances are varied by varying the aerosol component mixing ratios. The continuous variation of the fine-mode components allows for the continuous variation of the fine-mode aerosol absorption. Assuming that the correct aerosol model (i.e. the correct mixing fractions of the four components) is selected during the retrieval process, also other aerosol properties could be computed such as the single scattering albedo (SSA). Implications of this assumption regarding the ratio of the weakly/strongly absorbing fine-mode fraction are investigated in this paper by evaluating the validity of the SSA thus obtained. The SSA is indirectly estimated for aerosol plumes with moderate-to-high AOD resulting from wildfires in Russia in the summer of 2010. Together with the AOD, the SSA provides the aerosol absorbing optical depth (AAOD). The results are compared with AERONET data, i.e. AOD level 2.0 and SSA and AAOD inversion products. The RMSE

  11. Effects of stratospheric sulfate aerosol geo-engineering on cirrus clouds

    Science.gov (United States)

    Kuebbeler, Miriam; Lohmann, Ulrike; Feichter, Johann

    2012-12-01

    Cooling the Earth through the injection of sulphate into the stratosphere is one of the most discussed geo-engineering (GE) schemes. Stratospheric aerosols can sediment into the troposphere, modify the aerosol composition and thus might impact cirrus clouds. We use a global climate model with a physically based parametrization for cirrus clouds in order to investigate possible microphysical and dynamical effects. We find that enhanced stratospheric aerosol loadings as proposed by several GE approaches will likely lead to a reduced ice crystal nucleation rate and thus optically thinner cirrus clouds. These optically thinner cirrus clouds exert a strong negative cloud forcing in the long-wave which contributes by 60% to the overall net GE forcing. This shows that indirect effects of stratospheric aerosols on cirrus clouds may be important and need to be considered in order to estimate the maximum cooling derived from stratospheric GE.

  12. Direct and Indirect Effects of Climate Change on Amphibian Populations

    OpenAIRE

    Stephanie S. Gervasi; Searle, Catherine L.; Lawler, Joshua J.; Betsy A. Bancroft; Walls, Susan C.; Blaustein, Andrew R

    2010-01-01

    As part of an overall decline in biodiversity, populations of many organisms are declining and species are being lost at unprecedented rates around the world. This includes many populations and species of amphibians. Although numerous factors are affecting amphibian populations, we show potential direct and indirect effects of climate change on amphibians at the individual, population and community level. Shifts in amphibian ranges are predicted. Changes in climate may affect survival, growth...

  13. PRINCIPLE OF LEGAL CERTAINTY AND (INDIRECT EFFECT OF DIRECTIVES

    Directory of Open Access Journals (Sweden)

    Aistė Samuilytė-Mamontovė

    2014-08-01

    Full Text Available Purpose – The research discloses problematic aspects of the case law of the European Court of Justice (ECJ denying direct effect of the directives between private parties and real effect of (indirect effect of the directives in the light of the principle of legal certainty. Design/methodology/approach – Research employs logical, systemic, teleological and comparative analysis methods. Findings – Though ECJ still explicitly refers to the ruling made in Marshall case prohibiting horizontal effect of directives, its practice in reality is quiet controversial, begging for discourse and suggestions capable to assist in assuring the respect to the principle of legal certainty. Research limitations/implications – The focus of this article is not to analyse and disclose classical ECJ cases on (indirect effect of the directives. Research is limited to analysis of exceptions to the rule that denies direct effect of directives and reveals their compatibility with the principle of legal certainty. Practical implications – Key users of rules formed in the case law of the ECJ are national courts that shall assure application of the principle of legal certainty and abstain from acting contra legem. Such research is important in forecasting evolution of the case law of the ECJ in this area for courts and legal advisors that face with doctrine on effects of the directives in practice. Originality/Value – Doctrines on the effect of the directives are of great interest to legal researchers. However, lately ECJ case law allows making more detailed generalizations, though it also leaves certain open questions on the importance of the principle of the legal certainty in relation to principles of effectiveness and supremacy of European Union law. Superior courts of Lithuania usually refer to these doctrines in pretty theoretical aspects, however it is very rarely applied in practice. Keywords: legal certainty, direct effect, indirect effect, consistent

  14. Observed aerosol effects on marine cloud nucleation and supersaturation

    Science.gov (United States)

    Russell, Lynn M.; Sorooshian, Armin; Seinfeld, John H.; Albrecht, Bruce A.; Nenes, Athanasios; Leaitch, W. Richard; Macdonald, Anne Marie; Ahlm, Lars; Chen, Yi-Chun; Coggon, Matthew; Corrigan, Ashley; Craven, Jill S.; Flagan, Richard C.; Frossard, Amanda A.; Hawkins, Lelia N.; Jonsson, Haflidi; Jung, Eunsil; Lin, Jack J.; Metcalf, Andrew R.; Modini, Robin; Mülmenstädt, Johannes; Roberts, Greg C.; Shingler, Taylor; Song, Siwon; Wang, Zhen; Wonaschütz, Anna

    2013-05-01

    Aerosol particles in the marine boundary layer include primary organic and salt particles from sea spray and combustion-derived particles from ships and coastal cities. These particle types serve as nuclei for marine cloud droplet activation, although the particles that activate depend on the particle size and composition as well as the supersaturation that results from cloud updraft velocities. The Eastern Pacific Emitted Aerosol Cloud Experiment (EPEACE) 2011 was a targeted aircraft campaign to assess how different particle types nucleate cloud droplets. As part of E-PEACE 2011, we studied the role of marine particles as cloud droplet nuclei and used emitted particle sources to separate particle-induced feedbacks from dynamical variability. The emitted particle sources included shipboard smoke-generated particles with 0.05-1 μm diameters (which produced tracks measured by satellite and had drop composition characteristic of organic smoke) and combustion particles from container ships with 0.05-0.2 μm diameters (which were measured in a variety of conditions with droplets containing both organic and sulfate components) [1]. Three central aspects of the collaborative E-PEACE results are: (1) the size and chemical composition of the emitted smoke particles compared to ship-track-forming cargo ship emissions as well as background marine particles, with particular attention to the role of organic particles, (2) the characteristics of cloud track formation for smoke and cargo ships, as well as the role of multi-layered low clouds, and (3) the implications of these findings for quantifying aerosol indirect effects. For comparison with the E-PEACE results, the preliminary results of the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets (SOLEDAD) 2012 provided evidence of the cloud-nucleating roles of both marine organic particles and coastal urban pollution, with simultaneous measurements of the effective supersaturations of the clouds in the

  15. A long-term satellite study of aerosol effects on convective clouds in Nordic background air

    Directory of Open Access Journals (Sweden)

    M. K. Sporre

    2013-05-01

    Full Text Available Aerosol-cloud interactions constitute a~major uncertainty in future climate predictions. This study combines 10 yr of ground-based aerosol particle measurements from 2 Nordic background stations (Vavihill and Hyytiälä with MODIS (Moderate Resolution Imaging Spectroradiometer satellite data of convective clouds. The merged data are used to examine the indirect aerosol effects on convective clouds over the Nordic countries. From the satellite scenes, vertical profiles of cloud droplet effective radius (re are created by plotting re against cloud top temperature. The profiles have been divided according to aerosol loading but also modeled meteorological parameters from the ECMWF (European Centre for Medium-Range Forecasts. Furthermore, weather radar data from the BALTEX (Baltic Sea Experiment and ground based precipitation measurements from several ground-based meteorological measurement stations have been investigated to determine whether aerosols affect precipitation intensity and amount. Higher aerosol number concentrations result in smaller re throughout the entire profiles at both stations. Profiles associated with no or little precipitation have smaller droplets than those associated with more precipitation. Furthermore, an increase in aerosol loadings results in a suppression of precipitation rates, when the vertical extent of the clouds has been taken into account. Clouds with greater vertical extent have the highest precipitation rates and are most sensitive to aerosol perturbations. Nevertheless, meteorological parameters such as the vertical extent of the clouds, the atmospheric instability and the relative humidity in the lower atmosphere affect the amount of precipitation that reaches the ground more than the aerosols do. The combination of these ground-based and remote sensing datasets provides a unique long-term study of the effects of aerosols on convective clouds over the Nordic countries.

  16. Climatic effects of 1950–2050 changes in US anthropogenic aerosols – Part 2: Climate response

    Directory of Open Access Journals (Sweden)

    E. M. Leibensperger

    2011-08-01

    Full Text Available We investigate the climate response to US anthropogenic aerosol sources over the 1950 to 2050 period by using the NASA GISS general circulation model (GCM and comparing to observed US temperature trends. Time-dependent aerosol distributions are generated from the GEOS-Chem chemical transport model applied to historical emission inventories and future projections. Radiative forcing from US anthropogenic aerosols peaked in 1970–1990 and has strongly declined since due to air quality regulations. We find that the regional radiative forcing from US anthropogenic aerosols elicits a strong regional climate response, cooling the central and eastern US by 0.5–1.0 °C on average during 1970–1990, with the strongest effects on maximum daytime temperatures in summer and autumn. Aerosol cooling reflects comparable contributions from direct and indirect (cloud-mediated radiative effects. Absorbing aerosol (mainly black carbon has negligible warming effect. Aerosol cooling reduces surface evaporation and thus decreases precipitation along the US east coast, but also increases the southerly flow of moisture from the Gulf of Mexico resulting in increased cloud cover and precipitation in the central US. Observations over the eastern US show a lack of warming in 1960–1980 followed by very rapid warming since, which we reproduce in the GCM and attribute to trends in US anthropogenic aerosol sources. Present US aerosol concentrations are sufficiently low that future air quality improvements are projected to cause little further warming in the US (0.1 °C over 2010–2050. We find that most of the potential warming from aerosol source controls in the US has already been realized over the 1980–2010 period.

  17. Cloud forming properties of ambient aerosol in the Netherlands and resultant shortwave radiative forcing of climate.

    OpenAIRE

    Khlystov, A.

    1998-01-01

    This thesis discusses properties of ambient aerosols in the Netherlands which are controlling the magnitude of the local aerosol radiative forcing. Anthropogenic aerosols influence climate by changing the radiative transfer through the atmosphere via two effects, one is direct and a second is indirect. Due to the scattering of solar light on aerosol particles the Earth surface receives less radiation and thus cools, which is called the direct aerosol effect.The indirect effect includes proces...

  18. An increase in aerosol burden and radiative effects in a warmer world

    Science.gov (United States)

    Allen, Robert J.; Landuyt, William; Rumbold, Steven T.

    2016-03-01

    Atmospheric aerosols are of significant environmental importance, due to their effects on air quality, as well as their ability to alter the planet’s radiative balance. Recent studies characterizing the effects of climate change on air quality and the broader distribution of aerosols in the atmosphere show significant, but inconsistent results, including the sign of the effect. Using a suite of state-of-the-art climate models, we show that climate change is associated with a negative aerosol-climate feedback of -0.02 to -0.09 W m-2 K-1 for direct radiative effects, with much larger values likely for indirect radiative effects. This is related to an increase in most aerosol species, particularly over the tropics and Northern Hemisphere midlatitudes, largely due to a decrease in wet deposition associated with less large-scale precipitation over land. Although simulation of aerosol processes in global climate models possesses uncertainty, we conclude that climate change may increase aerosol burden and surface concentration, which may have implications for future air quality.

  19. Effect of an aerosol- reduction device on spreading infected aerosols during ultrasonic scaling

    Directory of Open Access Journals (Sweden)

    Ghalyani Isfahani P. Assistant Professor"

    2003-07-01

    Full Text Available Statement of Problem: Ultrasonic Scaling is one of the main sources of producing infected aerosols in dentistry. These aerosols are able to spread pathogens such as microorganisms associated with tuberculosis, conjunctivitis, influenza and other respiratory diseases, herpetic and other skin diseases, ADIS and hepatitis B."nPurpose: The aim of this study was to investigate the clinical effectiveness of an aerosol- reduction device attaching to ultrasonic scaler handpiece."nMaterials and Methods: In this experimental study 18 patients participated. Randomly, mandibular and maxillary quadrants of one side, in each subject, were scaled using an ultrasonic scaler with aerosol-reduction device for 5 minutes. After 30 minutes, another quadrant was scaled by ultrasonic scaler without aerosol- reduction device. In order to determine the effectiveness of aerosol- reduction device, blood agar plates attached to the surgical mask of the operator, 30 cm far from the patient's mouth, were incubated in 37°c for three days and the colonies were counted. Median, Interquartile eange and Wilcoxon test, at the 0.05 level of significance, were used to analyze the data."nResults: The median and interquartile range for the number of colony forming units (CFUS without aerosol- reduction device was 17.5 (8, 24, while the median for the number of CFUS when using aerosol-reduction device was 0 (0, 1, indicating significant statistical difference (PO.001 Conclusion: The aerosol- reduction device significantly reduces the amount of aerosols produced during ultrasonic scaling.

  20. Aerosol radiative effects over BIMSTEC regions

    Science.gov (United States)

    Kumar, Sumit; Kar, S. C.; Mupparthy, Raghavendra S.

    Aerosols can have variety of shapes, composition, sizes and other properties that influence their optical characteristics and thus the radiative impact. The visible impact of aerosol is the formation of haze, a layer of particles from vehicular, industrial emissions and biomass burning. The characterization of these fine particles is important for regulators and researchers because of their potential impact on human health, their ability to travel thousands of kilometers crossing international borders, and their influence on climate forcing and global warming. The Bay of Bengal Initiative for Multi-Sectoral Technical and Economic Cooperation (BIMSTEC) with Member Countries Bangladesh, Bhutan, India, Myanmar, Nepal, Sri Lanka and Thailand has emerged as an important regional group for technical and economic Cooperation. Continuing the quest for a deeper understanding of BIMSTEC countries weather and climate, in this paper we focused on aerosols and their direct radiative effects. Because of various contrasts like geophysical, agricultural practices, heterogeneous land/ocean surface, population etc these regions present an excellent natural laboratory for studying aerosol-meteorology interactions in tropical to sub-tropical environments. We exploited data available on multiple platforms (such as MISR, MODIS etc) and models (OPAC, SBDART etc) to compute the results. Ten regions were selected with different surface characteristics, also having considerable differences in the long-term trends and seasonal distribution of aerosols. In a preliminary analysis pertaining to pre-monsoon (March-April-May) of 2013, AOD _{555nm} is found to be maximum over Bangladesh (>0.52) and minimum over Bhutan (0.22), whereas other regions have intermediate values. Concurrent to these variability of AOD we found a strong reduction in incoming flux at surface of all the regions (> -25 Wm (-2) ), except Bhutan and Sri Lanka (< -18Wm (-2) ). The top of the atmosphere (TOA) forcing values are

  1. Microphysical effects determine macrophysical response for aerosol impacts on deep convective clouds.

    Science.gov (United States)

    Fan, Jiwen; Leung, L Ruby; Rosenfeld, Daniel; Chen, Qian; Li, Zhanqing; Zhang, Jinqiang; Yan, Hongru

    2013-11-26

    Deep convective clouds (DCCs) play a crucial role in the general circulation, energy, and hydrological cycle of our climate system. Aerosol particles can influence DCCs by altering cloud properties, precipitation regimes, and radiation balance. Previous studies reported both invigoration and suppression of DCCs by aerosols, but few were concerned with the whole life cycle of DCC. By conducting multiple monthlong cloud-resolving simulations with spectral-bin cloud microphysics that capture the observed macrophysical and microphysical properties of summer convective clouds and precipitation in the tropics and midlatitudes, this study provides a comprehensive view of how aerosols affect cloud cover, cloud top height, and radiative forcing. We found that although the widely accepted theory of DCC invigoration due to aerosol's thermodynamic effect (additional latent heat release from freezing of greater amount of cloud water) may work during the growing stage, it is microphysical effect influenced by aerosols that drives the dramatic increase in cloud cover, cloud top height, and cloud thickness at the mature and dissipation stages by inducing larger amounts of smaller but longer-lasting ice particles in the stratiform/anvils of DCCs, even when thermodynamic invigoration of convection is absent. The thermodynamic invigoration effect contributes up to ~27% of total increase in cloud cover. The overall aerosol indirect effect is an atmospheric radiative warming (3-5 W m(-2)) and a surface cooling (-5 to -8 W m(-2)). The modeling findings are confirmed by the analyses of ample measurements made at three sites of distinctly different environments. PMID:24218569

  2. Effect of aerosols on evapo-transpiration

    Science.gov (United States)

    Murthy, B. S.; Latha, R.; Manoj, Kumar; Mahanti, N. C.

    2014-06-01

    Aerosol direct radiative forcing (ARF) at surface is estimated from instantaneous, simultaneous observations of global radiation and aerosol optical depth (AOD) during winter, pre-monsoon and monsoon seasons over a tropical Indian station at the south-eastern end of Indo Gangetic basin. A comparison of observed and model derived ARFs is made and possible reasons for mismatch are discussed. Aerosol-induced reduction in solar visible (0.4-0.7 μm) spectrum energy (SWvis), contributing 44% to total broad band (0.3-3.0 μm) energy (SW), and its effect on surface energy fluxes are discussed in this study. Aerosols on an average reduce SWvis at surface by ˜27%. SWvis reduces by 14.5 W m-2 for a 0.1 increase in AOD when single scattering albedo (SSA) is 0.979 where as it reduces by 67.5 W m-2 when SSA is 0.867 indicating the significant effect of absorbing aerosols. Effect of ARF on net radiation, Rn, sensible heat flux, H and latent heat flux/evapo-transpiration, LE are estimated using the observed ratios of Rn/SW, H/Rn and LE/Rn, having reasonably good correlation. Observed Rn/SW varies between 0.59 and 0.75 with a correlation of 0.99 between them. LE, calculated by energy balance method, varies from 56% to 74% of Rn but with a lesser correlation, the possible reasons are discussed. For a given ARF, LE decreases by ˜14% and Rn by ˜15% with respect to observed LE and Rn respectively. The reduction in LE increases from 37% to 54% of ARF when LE increases from 220 W m-2 to 440 W m-2, suggesting that wet soil induces relatively larger reduction in evaporation. The results agree with earlier model sensitivity studies that Rn reduces more with increase in aerosol absorption which is compensated by proportionate reductions in H and LE depending on soil and atmospheric conditions.

  3. Effects of seed aerosols on the growth of secondary organic aerosols from the photooxidation of toluene

    Institute of Scientific and Technical Information of China (English)

    HAO Li-qing; WANG Zhen-ya; HUANG Ming-qiang; FANG Li; ZHANG Wei-jun

    2007-01-01

    Hydroxyl radical (·OH)-initiated photooxidation reaction of toluene was carried out in a self-made smog chamber. Four individual seed aerosols such as ammonium sulfate, ammonium nitrate, sodium silicate and calcium chloride, were introduced into the chamber to assess their influence on the growth of secondary organic aerosols (SOA). It was found that the low concentration of seed aerosols might lead to high concentration of SOA particles. Seed aerosols would promote rates of SOA formation at the start of the reaction and inhibit its formation rate with prolonging the reaction time. In the case of cv. 9000 pt/cm3 seed aerosol load, the addition of sodium silicate induced a same effect on the SOA formation as ammonium nitrate. The influence of the four individual seed aerosols on the generation of SOA increased in the order of calcium chloride>sodium silicate and ammonium nitrate> ammonium sulfate.

  4. Potential sensitivity of photosynthesis and isoprene emission to direct radiative effects of atmospheric aerosol pollution

    Science.gov (United States)

    Strada, Susanna; Unger, Nadine

    2016-04-01

    A global Earth system model is applied to quantify the impacts of direct anthropogenic aerosol effective radiative forcing on gross primary productivity (GPP) and isoprene emission. The impacts of different pollution aerosol sources (anthropogenic, biomass burning, and non-biomass burning) are investigated by performing sensitivity experiments. The model framework includes all known light and meteorological responses of photosynthesis, but uses fixed canopy structures and phenology. On a global scale, our results show that global land carbon fluxes (GPP and isoprene emission) are not sensitive to pollution aerosols, even under a global decline in surface solar radiation (direct + diffuse) by ˜ 9 %. At a regional scale, GPP and isoprene emission show a robust but opposite sensitivity to pollution aerosols in regions where forested canopies dominate. In eastern North America and Eurasia, anthropogenic pollution aerosols (mainly from non-biomass burning sources) enhance GPP by +5-8 % on an annual average. In the northwestern Amazon Basin and central Africa, biomass burning aerosols increase GPP by +2-5 % on an annual average, with a peak in the northwestern Amazon Basin during the dry-fire season (+5-8 %). The prevailing mechanism varies across regions: light scattering dominates in eastern North America, while a reduction in direct radiation dominates in Europe and China. Aerosol-induced GPP productivity increases in the Amazon and central Africa include an additional positive feedback from reduced canopy temperatures in response to increases in canopy conductance. In Eurasia and northeastern China, anthropogenic pollution aerosols drive a decrease in isoprene emission of -2 to -12 % on an annual average. Future research needs to incorporate the indirect effects of aerosols and possible feedbacks from dynamic carbon allocation and phenology.

  5. Overview of ACE-Asia Spring 2001 Investigations on Aerosol Radiative Effects and Related Aerosol Properties

    Science.gov (United States)

    Russell, Philip B.; Valero, F. P. J.; Flatau, P. J.; Bergin, M.; Holben, B.; Nakajima, T.; Pilewskie, P.; Bergstrom, R.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    A primary, ACE-Asia objective was to quantify the interactions between aerosols and radiation in the Asia-Pacific region. Toward this end, radiometric and related aerosol measurements were made from ocean, land, air and space platforms. Models that predict aerosol fields guided the measurements and are helping integrate and interpret results. Companion overview's survey these measurement and modeling components. Here we illustrate how these components were combined to determine aerosol radiative. impacts and their relation to aerosol properties. Because clouds can obscure or change aerosol direct radiative effects, aircraft and ship sorties to measure these effects depended on predicting and finding cloud-free areas and times with interesting aerosols present. Pre-experiment satellite cloud climatologies, pre-flight aerosol and cloud forecasts, and in-flight guidance from satellite imagery all helped achieve this. Assessments of aerosol regional radiative impacts benefit from the spatiotemporal coverage of satellites, provided satellite-retrieved aerosol properties are accurate. Therefore, ACE-Asia included satellite retrieval tests, as part of many comparisons to judge the consistency (closure) among, diverse measurements. Early results include: (1) Solar spectrally resolved and broadband irradiances and optical depth measurements from the C-130 aircraft and at Kosan, Korea yielded aerosol radiative forcing efficiencies, permitting comparisons between efficiencies of ACE-Asia and INDOEX aerosols, and between dust and "pollution" aerosols. Detailed results will be presented in separate papers. (2) Based on measurements of wavelength dependent aerosol optical depth (AOD) and single scattering albedo the estimated 24-h a average aerosol radiative forcing efficiency at the surface for photosynthetically active radiation (400 - 700 nm) in Yulin, China is approx. 30 W sq m per AOD(500 nm). (3) The R/V Brown cruise from Honolulu to Sea of Japan sampled an aerosol optical

  6. Effect of aerosolization on subsequent bacterial survival.

    OpenAIRE

    Walter, M V; Marthi, B; Fieland, V P; Ganio, L M

    1990-01-01

    To determine whether aerosolization could impair bacterial survival, Pseudomonas syringae and Erwinia herbicola were aerosolized in a greenhouse, the aerosol was sampled at various distances from the site of release by using all-glass impingers, and bacterial survival was followed in the impingers for 6 h. Bacterial survival subsequent to aerosolization of P. syringae and E. herbicola was not impaired 1 m from the site of release. P. syringae aerosolized at 3 to 15 m from the site of release ...

  7. Relative humidity and its effect on aerosol optical depth in the vicinity of convective clouds

    International Nuclear Information System (INIS)

    The hygroscopic growth of aerosols is controlled by the relative humidity (RH) and changes the aerosols’ physical and hence optical properties. Observational studies of aerosol–cloud interactions evaluate the aerosol concentration using optical parameters, such as the aerosol optical depth (AOD), which can be affected by aerosol humidification. In this study we evaluate the RH background and variance values, in the lower cloudy atmosphere, an additional source of variance in AOD values beside the natural changes in aerosol concentration. In addition, we estimate the bias in RH and AOD, related to cloud thickness. This provides the much needed range of RH-related biases in studies of aerosol–cloud interaction. Twelve years of radiosonde measurements (June–August) in thirteen globally distributed stations are analyzed. The estimated non-biased AOD variance due to day-to-day changes in RH is found to be around 20% and the biases linked to cloud development around 10%. Such an effect is important and should be considered in direct and indirect aerosol effect estimations but it is inadequate to account for most of the AOD trend found in observational studies of aerosol–cloud interactions. (letter)

  8. Direct and Indirect Effects of Climate Change on Amphibian Populations

    Directory of Open Access Journals (Sweden)

    Stephanie S. Gervasi

    2010-02-01

    Full Text Available As part of an overall decline in biodiversity, populations of many organisms are declining and species are being lost at unprecedented rates around the world. This includes many populations and species of amphibians. Although numerous factors are affecting amphibian populations, we show potential direct and indirect effects of climate change on amphibians at the individual, population and community level. Shifts in amphibian ranges are predicted. Changes in climate may affect survival, growth, reproduction and dispersal capabilities. Moreover, climate change can alter amphibian habitats including vegetation, soil, and hydrology. Climate change can influence food availability, predator-prey relationships and competitive interactions which can alter community structure. Climate change can also alter pathogen-host dynamics and greatly influence how diseases are manifested. Changes in climate can interact with other stressors such as UV-B radiation and contaminants. The interactions among all these factors are complex and are probably driving some amphibian population declines and extinctions.

  9. Direct and indirect community effects of rebuilding plans

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Rice, Jack C.

    2010-01-01

    Many fish communities are heavily exploited and rebuilding plans need to be implemented for depleted species. Within an ecosystem approach to management, development of rebuilding plans should include consideration of the expected consequences of the rebuilding of the target species on the rest of...... the marine community. Using size- and trait-based single-species and community models, a general assessment is made of the direct and indirect ecological consequences of a rebuilding plan based on a reduction in fishing mortality. If fishing mortality is sufficiently reduced, the time-scale of...... of the neighbouring trophic levels is expected to be much smaller than the increase in the target species and to be largest in species on the trophic level above. We discuss which effects could be responsible when a rebuilding plan does not result in the expected increase and how our results could be...

  10. Ion irradiation and biomolecular radiation damage II. Indirect effect

    CERN Document Server

    Wang, Wei; Su, Wenhui

    2010-01-01

    It has been reported that damage of genome in a living cell by ionizing radiation is about one-third direct and two-thirds indirect. The former which has been introduced in our last paper, concerns direct energy deposition and ionizing reactions in the biomolecules; the latter results from radiation induced reactive species (mainly radicals) in the medium (mainly water) surrounding the biomolecules. In this review, a short description of ion implantation induced radical formation in water is presented. Then we summarize the aqueous radical reaction chemistry of DNA, protein and their components, followed by a brief introduction of biomolecular damage induced by secondary particles (ions and electron). Some downstream biological effects are also discussed.

  11. Negative indirect effects of neighbors on imperiled scleractinian corals

    Science.gov (United States)

    Johnston, Lyza; Miller, M. W.

    2014-12-01

    Predation pressure on an individual may be influenced by spatial associations with other organisms. In the case of rare and imperiled species, such indirect interactions may affect the persistence and recovery of local populations. This study examined the effects of coral neighborhood composition on the foraging behavior and impact of the corallivorous gastropod, Coralliophila abbreviata. We conducted a manipulative field experiment in which focal colonies of the threatened scleractinian coral Acropora cervicornis had no neighbors, conspecific neighbors, alternative prey ( Orbicella faveolata) neighbors, or non-prey ( Porites asteroides) neighbors. Individually tagged C. abbreviata were then seeded into the study area and allowed to colonize the experimental plots. Initial colonization was significantly affected by the species of neighboring corals and snail abundance after colonization was negatively correlated with focal colony growth. Snails exhibited a strong prey preference for A. cervicornis over O. faveolata and responded numerically to neighborhood quality (i.e., relative preference for neighboring corals). Thus, conspecific neighbors had the greatest predator-mediated negative effect on focal colony performance followed by O. faveolata neighbors. The results suggest that C. abbreviata mediate apparent competition between O. faveolata and A. cervicornis as both species contributed to the local abundance of their shared predator. Additionally, home range estimates for tagged C. abbreviata were calculated, compared among sexes, and found to be significantly greater for males than for females. Overall, this study sheds light on the foraging behavior of an important coral predator and highlights the potential importance of consumer-mediated indirect interactions in the dynamics of severely reduced populations. The results also have direct implications for conservation and population enhancement efforts.

  12. Metal complexation inhibits the effect of oxalic acid in aerosols as cloud condensation nuclei (CCN

    Directory of Open Access Journals (Sweden)

    T. Furukawa

    2010-11-01

    Full Text Available Atmospheric aerosols have both a direct and an indirect cooling effect that influences the radiative balance at the Earth's surface. It has been estimated that the degree of cooling is large enough to cancel the warming effect of carbon dioxide. Among the cooling factors, secondary organic aerosols (SOA play a key role in the solar radiation balance in the troposphere as SOA can act as cloud condensation nuclei (CCN and extend the lifespan of clouds because of their high hygroscopic and water soluble nature. Oxalic acid is one of the major components of SOA, and is produced via several formation pathways in the atmosphere. However, it is not certain whether oxalic acid exists as free oxalic acid or as metal oxalate complexes in aerosols, although there is a marked difference in their solubility in water and their hygroscopicity. We employed X-ray absorption fine structure spectroscopy to characterize the calcium (Ca and zinc (Zn in aerosols collected at Tsukuba in Japan with fractionation based on particle size using an impactor aerosol sampler. It was shown that 10–60% and 20–100% of the total Ca and Zn in the finer particles (<2.1 μm were present as Ca and Zn oxalate complexes, respectively. Oxalic acid can act as CCN because of its hygroscopic properties, while metal complexes are not hygroscopic, and so cannot be CCN. Based on the concentration of noncomplexed and metal-complexed oxalate species, we found that most of the oxalic acid is present as metal oxalate complexes in the aerosols, suggesting that oxalic acid does not act as CCN in the atmosphere. Similar results are expected for other dicarboxylic acids, such as malonic and succinic acids. Thus, it is possible that the cooling effect of organic aerosols assumed in various climate modeling studies is overestimated because of the lack of information on metal oxalate complexes in aerosols.

  13. Effects of aerosol emission pathways on future warming and human health

    Science.gov (United States)

    Partanen, Antti-Ilari; Matthews, Damon

    2016-04-01

    The peak global temperature is largely determined by cumulative emissions of long-lived greenhouse gases. However, anthropogenic emissions include also so-called short-lived climate forcers (SLCFs), which include aerosol particles and methane. Previous studies with simple models indicate that the timing of SLCF emission reductions has only a small effect on the rate of global warming and even less of an effect on global peak temperatures. However, these simple model analyses do not capture the spatial dynamics of aerosol-climate interactions, nor do they consider the additional effects of aerosol emissions on human health. There is therefore merit in assessing how the timing of aerosol emission reductions affects global temperature and premature mortality caused by elevated aerosol concentrations, using more comprehensive climate models. Here, we used an aerosol-climate model ECHAM-HAMMOZ to simulate the direct and indirect radiative forcing resulting from aerosol emissions. We simulated Representative Concentration Pathway (RCP) scenarios, and we also designed idealized low and high aerosol emission pathways based on RCP4.5 scenario (LOW and HIGH, respectively). From these simulations, we calculated the Effective Radiative Forcing (ERF) from aerosol emissions between 1850 and 2100, as well as aerosol concentrations used to estimate the premature mortality caused by particulate pollution. We then use the University of Victoria Earth System Climate Model to simulate the spatial and temporal pattern of climate response to these aerosol-forcing scenarios, in combination with prescribed emissions of both short and long-lived greenhouse gases according to the RCP4.5 scenario. In the RCP scenarios, global mean ERF declined during the 21st century from ‑1.3 W m‑2 to ‑0.4 W m‑2 (RCP8.5) and ‑0.2 W m‑2 (RCP2.6). In the sensitivity scenarios, the forcing at the end of the 21st century was ‑1.6 W m‑2 (HIGH) and practically zero (LOW). The difference in global

  14. The Indirect Effect of UV: Some Good News for Microbes?

    Science.gov (United States)

    Rothschild, Lynn J.; Purcell, Diane; Rogoff, Dana; Wilson, Cindy; Brass, James A. (Technical Monitor)

    2002-01-01

    Ultraviolet (UV) radiation is of great concern because its biological effects are predominantly harmful. UV damage may be direct or indirect, the latter mediated through the photochemical production of reactive oxygen species such as hydrogen peroxide. We measured the effect of H2O2 on various microbes both in the lab and in nature. At our study site in Yellowstone National Park, there is a UV-induced diurnal fluctuation of H2O2 extending up to one micron. Levels of DNA synthesis resulting from exposure to H2O2 were measured in several algal mats. Within naturally-occurring concentrations of H2O2, DNA synthesis increased. Laboratory studies showed that similar concentrations of H2O2 induce mitosis. We hypothesize that the low levels of H2O2 encountered in nature are inducing mitotic division. At higher levels of H2O2 a second peak in DNA synthesis was found which we interpret to represent DNA damage repair. These experiments suggest that in nature, the low levels of H2O2 produced may have a mitogenic rather than damaging effect. Assuming early levels of UV radiation were substantially higher at the time protists evolved, differential mitogenic effects could have influenced protistan evolution. With H2O2 likely to be present on such bodies as Mars and Europa, the response of organisms will be concentration-dependent and not linear.

  15. Aerosol climate effects and air quality impacts from 1980 to 2030

    International Nuclear Information System (INIS)

    We investigate aerosol effects on climate for 1980, 1995 (meant to reflect present day) and 2030 using the NASA Goddard Institute for Space Studies climate model coupled to an on-line aerosol source and transport model with interactive oxidant and aerosol chemistry. Aerosols simulated include sulfates, organic matter (OM), black carbon (BC), sea-salt and dust and, additionally, the amount of tropospheric ozone is calculated, allowing us to estimate both changes to air quality and climate for different time periods and emission amounts. We include both the direct aerosol effect and indirect aerosol effects for liquid-phase clouds. Future changes for the 2030 A1B scenario are examined, focusing on the Arctic and Asia, since changes are pronounced in these regions. Our results for the different time periods include both emission changes and physical climate changes. We find that the aerosol indirect effect (AIE) has a large impact on photochemical processing, decreasing ozone amount and ozone forcing, especially for the future (2030-1995). Ozone forcings increase from 0 to 0.12 W m-2 and the total aerosol forcing decreases from -0.10 to -0.94 W m-2 (AIE decreases from -0.13 to -0.68 W m-2) for 1995-1980 versus 2030-1995. Over the Arctic we find that compared to ozone and the direct aerosol effect, the AIE contributes the most to net radiative flux changes. The AIE, calculated for 1995-1980, is positive (1.0 W m-2), but the magnitude decreases (-0.3 W m-2) considerably for the future scenario. Over Asia, we evaluate the role of biofuel- and transportation-based emissions (for BC and OM) via a scenario (2030A) that includes a projected increase (factor of 2) in biofuel- and transport-based emissions for 2030 A1B over Asia. Projected changes from present day due to the 2030A emissions versus 2030 A1B are a factor of 4 decrease in summertime precipitation in Asia. Our results are sensitive to emissions used. Uncertainty in present-day emissions suggests that future

  16. Trait-Mediated Indirect Effects of Phorid Flies on Ants

    Directory of Open Access Journals (Sweden)

    Hsun-Yi Hsieh

    2012-01-01

    Full Text Available This paper provides a synthesis of the ecological impact of phorid fly parasitoids on ants. We find the most important impact of phorids on ants to be trait-mediated effects. Phorids diminish the foraging activity of ants, frequently reducing the number and average size of foragers and reducing the amount of food retrieved by a colony. However, ants' coping mechanisms include changing foraging site and time. Phorids can also affect competition, especially through changes in the ability of the host to win in exploitative competition. Factors such as microclimate, resource size, and habitat complexity interact with phorids to change their effect on competition. By being highly specific and attacking ants high in the competitive hierarchy, phorids can alter the linear nature of the competitive transitivity, and by reducing the number of foragers, they can change the discovery-dominance tradeoff that is observed in some ant communities. Trait-mediated effects of phorids also cascade to other trophic levels. As an example, we discuss the trait-mediated cascade of phorids on the Azteca instabilis system in coffee. In this system, by reducing the foraging activity of A. instabilis, phorids reduce the direct and indirect biological control impact of the ant in the coffee agroecosystem.

  17. Aircraft-measured indirect cloud effects from biomass burning smoke in the Arctic and subarctic

    Energy Technology Data Exchange (ETDEWEB)

    Zamora, Lauren M.; Kahn, Ralph; Cubison, Michael J.; Diskin, G. S.; Jimenez, J. L.; Kondo, Yutaka; McFarquhar, Greg; Nenes, Athanasios; Thornhill, K. L.; Wisthaler, Armin; Zelenyuk, Alla; Ziemba, L. D.

    2016-01-21

    The incidence of wildfires in the Arctic and subarctic is increasing; in boreal North 24 America, for example, the burned area is expected to increase by 200-300% over the next 50-100 years, which previous studies suggest could have a large effect on cloud 1 microphysics, lifetime, albedo, and precipitation. However, the interactions between smoke particles and clouds remain poorly quantified due to confounding meteorological influences and remote sensing limitations. Here, we use data from several aircraft campaigns in the Arctic and subarctic to explore cloud microphysics in liquid-phase clouds influenced by biomass burning. Median cloud droplet radii in smoky clouds were ~50% smaller than in background clouds. Based on the relationship between cloud droplet number (Nliq) and various biomass burning tracers (BBt) across the multi campaign dataset, we calculated the magnitude of subarctic and Arctic smoke aerosol cloud interactions (ACI, where ACI = (1/3)* d ln(Nliq)/d ln(BBt)) to be ~0.12 out of a maximum possible value of 0.33 that would be obtained if all aerosols were to nucleate cloud droplets. Interestingly, in a separate subarctic case study with low liquid water content (~0.02 g m-3) and very high aerosol concentrations (2000-3000 cm-3) in the most polluted clouds, the estimated ACI value was only 0.06. In this case, competition for water vapor by the high concentration of CCN strongly limited the formation of droplets and reduced the cloud albedo effect, which highlights the importance of cloud feedbacks across scales. Using our calculated ACI values, we estimate that the smoke-driven cloud albedo effect may decrease shortwave radiative flux by 2-4 W m-2 or more under some low and homogeneous cloud cover conditions in the subarctic, although the changes should be smaller in high surface albedo regions of the Arctic. We lastly show evidence to suggest that numerous northern latitude background Aitken particles can interact with combustion particles

  18. The contribution of aerosol hygroscopic growth to the modeled aerosol radiative effect

    Science.gov (United States)

    Kokkola, Harri; Kühn, Thomas; Kirkevåg, Alf; Romakkaniemi, Sami; Arola, Antti

    2016-04-01

    The hygroscopic growth of atmospheric aerosols can have a significant effect on the direct radiative effect of atmospheric aerosol. However, there are significant uncertainties concerning how much of the radiative forcing is due to different chemical compounds, especially water. For example, modeled optical depth of water in global aerosol-climate models varies by more than a factor of two. These differences can be attributed to differences in modeled 1) hygroscopicity, 2) ambient relative humidity, and/or 3) aerosol size distribution. In this study, we investigate which of these above-mentioned factors cause the largest variability in the modeled optical depth of water. In order to do this, we have developed a tool that calculates aerosol extinction using interchangeable global 3D data of aerosol composition, relative humidity, and aerosol size distribution fields. This data is obtained from models that have taken part in the open international initiative AeroCom (Aerosol Comparisons between Observations and Models). In addition, we use global 3D data for relative humidity from the Atmospheric Infrared Sounder (AIRS) flying on board NASA's Aqua satellite and the National Centers for Environmental Prediction (NCEP) reanalysis data. These observations are used to evaluate the modeled relative humidity fields. In the first stage of the study, we made a detailed investigation using the aerosol-chemistry-climate model ECHAM-HAMMOZ in which most of the aerosol optical depth is caused by water. Our results show that the model significantly overestimates the relative humidity over the oceans while over land, the overestimation is lower or it is underestimated. Since this overestimation occurs over the oceans, the water optical depth is amplified as the hygroscopic growth is very sensitive to changes in high relative humidities. Over land, error in modeled relative humidity is unlikely to cause significant errors in water optical depth as relative humidities are generally

  19. A review of measurement-based assessments of the aerosol direct radiative effect and forcing

    Directory of Open Access Journals (Sweden)

    H. Yu

    2006-01-01

    Full Text Available Aerosols affect the Earth's energy budget directly by scattering and absorbing radiation and indirectly by acting as cloud condensation nuclei and, thereby, affecting cloud properties. However, large uncertainties exist in current estimates of aerosol forcing because of incomplete knowledge concerning the distribution and the physical and chemical properties of aerosols as well as aerosol-cloud interactions. In recent years, a great deal of effort has gone into improving measurements and datasets. It is thus feasible to shift the estimates of aerosol forcing from largely model-based to increasingly measurement-based. Our goal is to assess current observational capabilities and identify uncertainties in the aerosol direct forcing through comparisons of different methods with independent sources of uncertainties. Here we assess the aerosol optical depth (τ, direct radiative effect (DRE by natural and anthropogenic aerosols, and direct climate forcing (DCF by anthropogenic aerosols, focusing on satellite and ground-based measurements supplemented by global chemical transport model (CTM simulations. The multi-spectral MODIS measures global distributions of aerosol optical depth (τ on a daily scale, with a high accuracy of ±0.03±0.05τ over ocean. The annual average τ is about 0.14 over global ocean, of which about 21%±7% is contributed by human activities, as estimated by MODIS fine-mode fraction. The multi-angle MISR derives an annual average AOD of 0.23 over global land with an uncertainty of ~20% or ±0.05. These high-accuracy aerosol products and broadband flux measurements from CERES make it feasible to obtain observational constraints for the aerosol direct effect, especially over global the ocean. A number of measurement-based approaches estimate the clear-sky DRE (on solar radiation at the top-of-atmosphere (TOA to be about -5.5±0.2 Wm-2 (median ± standard error from various methods over the global ocean. Accounting for thin cirrus

  20. Economic impact of indirects effects of tourism on the South Bohemian production

    OpenAIRE

    Michaela Antoušková

    2010-01-01

    Tourism is characterized as a sector of economy with high multiplier effect; tourism significantly influences other sectors of national economy. Through the multiplier the indirect effect of tourism might be measured. The value of tourist multiplier is a strongly discussed topic, especially in the Czech Republic. The indirect effects of tourism are commonly measured by multiplier in other countries. The article aims to quantify the indirect effects of tourism in the Southern Bohemia. To quant...

  1. Radiative Effects of Aerosols Generated from Biomass Burning, Dust Storms, and Forest Fires

    Science.gov (United States)

    Christopher Sundar A.; Vulcan, Donna V.; Welch, Ronald M.

    1996-01-01

    Atmospheric aerosol particles, both natural and anthropogenic, are important to the earth's radiative balance. They scatter the incoming solar radiation and modify the shortwave reflective properties of clouds by acting as Cloud Condensation Nuclei (CCN). Although it has been recognized that aerosols exert a net cooling influence on climate (Twomey et al. 1984), this effect has received much less attention than the radiative forcings due to clouds and greenhouse gases. The radiative forcing due to aerosols is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign (Houghton et al. 1990). Atmospheric aerosol particles generated from biomass burning, dust storms and forest fires are important regional climatic variables. A recent study by Penner et al. (1992) proposed that smoke particles from biomass burning may have a significant impact on the global radiation balance. They estimate that about 114 Tg of smoke is produced per year in the tropics through biomass burning. The direct and indirect effects of smoke aerosol due to biomass burning could add up globally to a cooling effect as large as 2 W/sq m. Ackerman and Chung (1992) used model calculations and the Earth Radiation Budget Experiment (ERBE) data to show that in comparison to clear days, the heavy dust loading over the Saudi Arabian peninsula can change the Top of the Atmosphere (TOA) clear sky shortwave and longwave radiant exitance by 40-90 W/sq m and 5-20 W/sq m, respectively. Large particle concentrations produced from these types of events often are found with optical thicknesses greater than one. These aerosol particles are transported across considerable distances from the source (Fraser et al. 1984). and they could perturb the radiative balance significantly. In this study, the regional radiative effects of aerosols produced from biomass burning, dust storms and forest fires are examined using the Advanced Very High Resolution Radiometer (AVHRR) Local Area

  2. Separating Real and Apparent Effects of Cloud, Humidity, and Dynamics on Aerosol Optical Thickness near Cloud Edges

    Science.gov (United States)

    Jeong, Myeong-Jae; Li, Zhanqing

    2010-01-01

    Aerosol optical thickness (AOT) is one of aerosol parameters that can be measured on a routine basis with reasonable accuracy from Sun-photometric observations at the surface. However, AOT-derived near clouds is fraught with various real effects and artifacts, posing a big challenge for studying aerosol and cloud interactions. Recently, several studies have reported correlations between AOT and cloud cover, pointing to potential cloud contamination and the aerosol humidification effect; however, not many quantitative assessments have been made. In this study, various potential causes of apparent correlations are investigated in order to separate the real effects from the artifacts, using well-maintained observations from the Aerosol Robotic Network, Total Sky Imager, airborne nephelometer, etc., over the Southern Great Plains site operated by the U.S. Department of Energy's Atmospheric Radiation Measurement Program. It was found that aerosol humidification effects can explain about one fourth of the correlation between the cloud cover and AOT. New particle genesis, cloud-processed particles, atmospheric dynamics, and aerosol indirect effects are likely to be contributing to as much as the remaining three fourth of the relationship between cloud cover and AOT.

  3. Effects of biomass burning aerosols on CO2 fluxes on Amazon Region

    Science.gov (United States)

    Soares Moreira, Demerval; Freitas, Saulo; Longo, Karla; Rosario, Nilton

    2015-04-01

    During the dry season in Central Brazil and Southern Amazon, there is an usually high concentration of aerosol particles associated with intense human activities, with extensive biomass burning. It has been observed through remote sensing that the smoke clouds in these areas often cover an area of about 4 to 5 million km2. Thus, the average aerosol optical depth of these regions at 500 ηm, is usually below 0.1 during the rainy season and can exceed 0.9 in the fire season. Aerosol particles act as condensation nuclei and also increase scattering and absorption of the incident radiation. Therefore, the layer of the aerosol alters the precipitation rate; reduces the amount of solar energy that reaches the surface, producing a cooling; and causes an increase of diffuse radiation. These factors directly and indirectly affect the CO2 fluxes at the surface. In this work, the chemical-atmospheric model CCATT-BRAMS (Coupled Chemistry-Aerosol-Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System) coupled to the surface model JULES (Joint UK Land Environment Simulator) was used to simulate the effects of biomass burning aerosols in CO2 fluxes in the Amazon region. Both the total effect of the aerosols and the contribution related only to the increase of the diffuse fraction caused by the their presence were analyzed. The results show that the effect of the scattered fraction is dominant over all other effects. It was also noted that the presence of aerosols from fires can substantially change biophysiological processes of the carbon cycle. In some situations, it can lead to a sign change in the net ecosystem exchange (NEE), turning it from a source of CO2 to the atmosphere, when the aerosol is not considered in the simulations, to a sink, when it is considered. Thus, this work demonstrates the importance of considering the presence of aerosols in numerical simulations of weather and climate, since carbon dioxide is a major

  4. Direct and semidirect aerosol effects of Southern African biomass burning aerosol

    Energy Technology Data Exchange (ETDEWEB)

    Sakaeda, Naoko; Wood, Robert; Rasch, Philip J.

    2011-06-21

    The direct and semi-direct radiative effects of biomass burning aerosols from Southern African fires during July-October are investigated using 20 year runs of the Community Atmospheric Model (CAM) coupled to a slab ocean model. The aerosol optical depth is constrained using observations in clear skies from MODIS and for aerosol layers above clouds from CALIPSO. Over the ocean, where the absorbing biomass burning aerosol layers are primarily located above cloud, negative top of atmosphere (TOA) semi-direct radiative effects associated with increased low cloud cover dominate over a weaker positive all-sky direct radiative effect (DRE). In contrast, over the land where the aerosols are often below or within cloud layers, reductions in cloud liquid water path (LWP) lead to a positive semi-direct radiative effect that dominates over a near-zero DRE. Over the ocean, the cloud response can be understood as a response to increased lower tropospheric stability (LTS) which is caused both by aerosol absorptive warming in overlying layers and surface cooling in response to direct aerosol forcing. The ocean cloud changes are robust to changes in the cloud parameterization (removal of the hard-wired dependence of clouds on LTS), suggesting that they are physically realistic. Over land where cloud cover changes are minimal, decreased LWP is consistent with weaker convection driven by increased static stability. Over the entire region the overall TOA radiative effect from the biomass burning aerosols is almost zero due to opposing effects over the land and ocean. However, the surface forcing is strongly negative requiring a reduction in precipitation. This is primarily realized through reductions in convective precipitation on both the southern and northern flanks of the convective precipitation region spanning the equatorial rainforest and the ITCZ in the southern Sahel. The changes are consistent with the low-level aerosol forced cooling pattern. The results highlight the

  5. The joint effects of kin, multilevel selection and indirect genetic effects on response to genetic selection

    NARCIS (Netherlands)

    Bijma, P.; Wade, M.J.

    2008-01-01

    Kin and levels-of-selection models are common approaches for modelling social evolution. Indirect genetic effect (IGE) models represent a different approach, specifying social effects on trait values rather than fitness. We investigate the joint effect of relatedness, multilevel selection and IGEs o

  6. Quantifying and Testing Indirect Effects in Simple Mediation Models when the Constituent Paths Are Nonlinear

    Science.gov (United States)

    Hayes, Andrew F.; Preacher, Kristopher J.

    2010-01-01

    Most treatments of indirect effects and mediation in the statistical methods literature and the corresponding methods used by behavioral scientists have assumed linear relationships between variables in the causal system. Here we describe and extend a method first introduced by Stolzenberg (1980) for estimating indirect effects in models of…

  7. Indirect economic effects of new infrastructure : A comparison of Dutch high speed rail variants

    NARCIS (Netherlands)

    Oosterhaven, J; Romp, WE

    2003-01-01

    New transport infrastructure has a myriad of direct and indirect effects. The indirect effects on population and economic activity are most difficult to estimate. This paper introduces three different models to estimate the impacts of new infrastructure on labour supply and demand, and carefully exp

  8. Reallocation in modal aerosol models: impacts on predicting aerosol radiative effects

    Science.gov (United States)

    Korhola, T.; Kokkola, H.; Korhonen, H.; Partanen, A.-I.; Laaksonen, A.; Lehtinen, K. E. J.; Romakkaniemi, S.

    2014-01-01

    Atmospheric models often represent the aerosol particle size distribution with a modal approach, in which particles are described with log-normal modes within predetermined size ranges. This approach reallocates particles numerically from one mode to another for example during particle growth, potentially leading to artificial changes in the aerosol size distribution. In this study we analysed how the modal reallocation affects climate-relevant variables: cloud droplet number concentration (CDNC), aerosol-cloud interaction parameter (ACI) and light extinction coefficient (qext). The ACI parameter gives the response of CDNC to a change in total aerosol number concentration. We compared these variables between a modal model (with and without reallocation routines) and a high resolution sectional model, which was considered a reference model. We analysed the relative differences in the chosen variables in four experiments designed to assess the influence of atmospheric aerosol processes. We find that limiting the allowed size ranges of the modes, and subsequent remapping of the distribution, leads almost always to an underestimation of cloud droplet number concentrations (by up to 100%) and an overestimation of light extinction (by up to 20%). On the other hand, the aerosol-cloud interaction parameter can be either over- or underestimated by the reallocating model, depending on the conditions. For example, in the case of atmospheric new particle formation events followed by rapid particle growth, the reallocation can cause on average a 10% overestimation of the ACI parameter. Thus it is shown that the reallocation affects the ability of a model to estimate aerosol climate effects accurately, and this should be taken into account when using and developing aerosol models.

  9. Aerosol composition and sources during the Chinese Spring Festival: fireworks, secondary aerosol, and holiday effects

    Science.gov (United States)

    Jiang, Q.; Sun, Y. L.; Wang, Z.; Yin, Y.

    2015-06-01

    Aerosol particles were characterized by an Aerodyne aerosol chemical speciation monitor along with various collocated instruments in Beijing, China, to investigate the role of fireworks (FW) and secondary aerosol in particulate pollution during the Chinese Spring Festival of 2013. Three FW events, exerting significant and short-term impacts on fine particles (PM2.5), were observed on the days of Lunar New Year, Lunar Fifth Day, and Lantern Festival. The FW were shown to have a large impact on non-refractory potassium, chloride, sulfate, and organics in submicron aerosol (PM1), of which FW organics appeared to be emitted mainly in secondary, with its mass spectrum resembling that of secondary organic aerosol (SOA). Pollution events (PEs) and clean periods (CPs) alternated routinely throughout the study. Secondary particulate matter (SPM = SOA + sulfate + nitrate + ammonium) dominated the total PM1 mass on average, accounting for 63-82% during nine PEs in this study. The elevated contributions of secondary species during PEs resulted in a higher mass extinction efficiency of PM1 (6.4 m2 g-1) than during CPs (4.4 m2 g-1). The Chinese Spring Festival also provides a unique opportunity to study the impact of reduced anthropogenic emissions on aerosol chemistry in the city. Primary species showed ubiquitous reductions during the holiday period with the largest reduction being in cooking organic aerosol (OA; 69%), in nitrogen monoxide (54%), and in coal combustion OA (28%). Secondary sulfate, however, remained only slightly changed, and the SOA and the total PM2.5 even slightly increased. Our results have significant implications for controlling local primary source emissions during PEs, e.g., cooking and traffic activities. Controlling these factors might have a limited effect on improving air quality in the megacity of Beijing, due to the dominance of SPM from regional transport in aerosol particle composition.

  10. Exploring Aerosol Effects on Rainfall for Brisbane, Australia

    Directory of Open Access Journals (Sweden)

    Michael Hewson

    2013-10-01

    Full Text Available The majority of studies assessing aerosol effects on rainfall use coarse spatial scale (1° latitude/longitude or more and multi-seasonal or decadal data sets. Here, we present results from a spatial correlation of aerosol size distribution and rain rate for selected stratiform and cumuliform precipitation events. The chemistry transport version of the Weather Research and Forecasting model was used to estimate aerosol parameters during rain events Aerosol maps were then compared with observations of rainfall using geostatistics for the first time. The cross-variogram analysis showed that anthropogenic aerosol was associated with areas of less intense rain within the stratiform system studied. For cumuliform systems, cross-variogram analysis found that anthropogenic emissions may be associated with enhanced rain downwind of aerosol emissions. We conclude that geostatistics provides a promising new technique to investigate relationships between aerosols and rainfall at spatial scales of 1 km which complements more commonly used methods to study aerosol effects on rainfall.

  11. Clinical side effects during aerosol therapy: cutaneous and ocular effects.

    Science.gov (United States)

    Geller, David E

    2007-01-01

    Aerosolized medications maximize clinical benefit by targeting the airways and minimize side effects by reducing (though not eliminating) systemic exposure. Aerosolized drugs delivered with a facemask may inadvertently deposit on the face and in the eyes, raising concerns about cutaneous and ocular side effects with these drugs. Cases of anisocoria have been reported from exposure of the eyes to aerosol bronchodilators. Whether inhaled corticosteroids (ICS) can cause skin and eye problems like those seen with systemic or topical steroids is more difficult to answer. Patients who take ICS may have other corticosteroid exposures, or have other conditions that predispose them to side effects, making the analysis of the ICS risk challenging. Also, many studies were not designed to search for cutaneous or ocular effects, or may have been too short to detect these effects. Nevertheless, ICS have been associated with an increased risk of skin thinning, bruising, cataracts and possibly glaucoma in adults, but not in children. The risks increase with advanced age, higher doses, and longer duration of use. In children, the risks of cataracts and glaucoma were negligible with ICS, whether a mouthpiece or a mask interface was used. Side effects like skin rash and conjunctivitis occurred at low frequencies similar to placebo or comparator drugs. We do not know whether exposed children will have increased risks from ICS later in life. Therefore, it is wise to avoid face and eye deposition when possible, and to use the minimally effective dose. PMID:17411401

  12. Evaluation of atmospheric aerosol and tropospheric ozone effects on global terrestrial ecosystem carbon dynamics

    Science.gov (United States)

    Chen, Min

    The increasing human activities have produced large amounts of air pollutants ejected into the atmosphere, in which atmospheric aerosols and tropospheric ozone are considered to be especially important because of their negative impacts on human health and their impacts on global climate through either their direct radiative effect or indirect effect on land-atmosphere CO2 exchange. This dissertation dedicates to quantifying and evaluating the aerosol and tropospheric ozone effects on global terrestrial ecosystem dynamics using a modeling approach. An ecosystem model, the integrated Terrestrial Ecosystem Model (iTem), is developed to simulate biophysical and biogeochemical processes in terrestrial ecosystems. A two-broad-band atmospheric radiative transfer model together with the Moderate-Resolution Imaging Spectroradiometer (MODIS) measured atmospheric parameters are used to well estimate global downward solar radiation and the direct and diffuse components in comparison with observations. The atmospheric radiative transfer modeling framework were used to quantify the aerosol direct radiative effect, showing that aerosol loadings cause 18.7 and 12.8 W m -2 decrease of direct-beam Photosynthetic Active Radiation (PAR) and Near Infrared Radiation (NIR) respectively, and 5.2 and 4.4 W m -2 increase of diffuse PAR and NIR, respectively, leading to a total 21.9 W m-2 decrease of total downward solar radiation over the global land surface during the period of 2003-2010. The results also suggested that the aerosol effect may be overwhelmed by clouds because of the stronger extinction and scattering ability of clouds. Applications of the iTem with solar radiation data and with or without considering the aerosol loadings shows that aerosol loading enhances the terrestrial productions [Gross Primary Production (GPP), Net Primary Production (NPP) and Net Ecosystem Production (NEP)] and carbon emissions through plant respiration (RA) in global terrestrial ecosystems over the

  13. Sensitive detection of aerosol effect on simulated IASI spectral radiance

    International Nuclear Information System (INIS)

    Guided by radiative transfer modeling of the effects of dust (aerosol) on satellite thermal infrared radiance by many different imaging radiometers, in this article, we present the aerosol-effected satellite radiative signal changes in the top of atmosphere (TOA). The simulation of TOA radiance for Infrared Atmospheric Sounding Interferometer (IASI) is performed by using the RTTOV fast radiative transfer model. The model computation is carried out with setting representative geographical atmospheric models and typical default aerosol climatological models under clear sky condition. The radiative differences (in units of equivalent black body brightness temperature differences (BTDs)) between simulated radiances without consideration of the impact of aerosol (Aerosol-free) and with various aerosol models (Aerosol-modified) are calculated for the whole IASI spectrum between 3.62 and 15.5 μm. The comparisons of BTDs are performed through 11 aerosol models in 5 classified atmospheric models. The results show that the Desert aerosol model has the most significant impact on IASI spectral simulated radiances than the other aerosol models (Continental, Urban, Maritime types and so on) in Mid-latitude Summer, contributing to the mineral aerosol components contained. The value of BTDs could reach up to 1 K at peak points. The atmospheric window spectral region between 900 and 1100 cm−1 (9.09–11.11 μm) is concentrated after the investigation for the largest values of aerosol-affected radiance differences. BTDs in IASI spectral region between 645 and 1200 cm−1 occupies the largest oscillation and the major part of the whole spectrum. The IASI highest window peak-points channels (such as 9.4 and 10.2 μm) are obtained finally, which are the most sensitive ones to the simulated IASI radiance. -- Highlights: ► Sensitive study of aerosol effect on simulated IASI spectral radiance is performed. ► The aerosol components have influenced IASI spectral regions significantly

  14. Profiling Transboundary Aerosols over Taiwan and Assessing Their Radiative Effects

    Science.gov (United States)

    Wang, Sheng-Hsiang; Lin, Neng-Huei; Chou, Ming-Dah; Tsay, Si-Chee; Welton, Ellsworth J.; Hsu, N. Christina; Giles, David M.; Liu, Gin-Rong; Holben, Brent N.

    2010-01-01

    A synergistic process was developed to study the vertical distributions of aerosol optical properties and their effects on solar heating using data retrieved from ground-based radiation measurements and radiative transfer simulations. Continuous MPLNET and AERONET observations were made at a rural site in northern Taiwan from 2005 to 2007. The aerosol vertical extinction profiles retrieved from ground-based lidar measurements were categorized into near-surface, mixed, and two-layer transport types, representing 76% of all cases. Fine-mode (Angstrom exponent, alpha, approx.1.4) and moderate-absorbing aerosols (columnar single-scattering albedo approx.0.93, asymmetry factor approx.0.73 at 440 nm wavelength) dominated in this region. The column-integrated aerosol optical thickness at 500 nm (tau(sub 500nm)) ranges from 0.1 to 0.6 for the near-surface transport type, but can be doubled in the presence of upper-layer aerosol transport. We utilize aerosol radiative efficiency (ARE; the impact on solar radiation per unit change of tau(sub 500nm)) to quantify the radiative effects due to different vertical distributions of aerosols. Our results show that the ARE at the top-of-atmosphere (-23 W/ sq m) is weakly sensitive to aerosol vertical distributions confined in the lower troposphere. On the other hand, values of the ARE at the surface are -44.3, -40.6 and -39.7 W/sq m 38 for near-surface, mixed, and two-layer transport types, respectively. Further analyses show that the impact of aerosols on the vertical profile of solar heating is larger for the near-surface transport type than that of two-layer transport type. The impacts of aerosol on the surface radiation and the solar heating profiles have implications for the stability and convection in the lower troposphere.

  15. Sensitivity of aerosol optical thickness and aerosol direct radiative effect to relative humidity

    Directory of Open Access Journals (Sweden)

    H. Bian

    2009-04-01

    Full Text Available We present a sensitivity study of the effects of spatial and temporal resolution of atmospheric relative humidity (RH on calculated aerosol optical thickness (AOT and the aerosol direct radiative effects (DRE in a global model. We carry out different modeling experiments using the same aerosol fields simulated in the Global Modeling Initiative (GMI model at a resolution of 2° latitude by 2.5° longitude, using time-averaged fields archived every three hours by the Goddard Earth Observation System Version 4 (GEOS-4, but we change the horizontal and temporal resolution of the relative humidity fields. We find that, on a global average, the AOT calculated using RH at a 1°×1.25° horizontal resolution is 11% higher than that using RH at a 2°×2.5° resolution, and the corresponding DRE at the top of the atmosphere is 8–9% and 15% more negative (i.e., more cooling for total aerosols and anthropogenic aerosol alone, respectively, in the finer spatial resolution case. The difference is largest over surface escarpment regions (e.g. >200% over the Andes Mountains where RH varies substantially with surface terrain. The largest zonal mean AOT difference occurs at 50–60° N (16–21%, where AOT is also relatively larger. A similar impact is also found when the time resolution of RH is increased. This increase of AOT and aerosol cooling with the increase of model resolution is due to the highly non-linear relationship between RH and the aerosol mass extinction efficiency (MEE at high RH (>80%. Our study is a specific example of the uncertainty in model results highlighted by multi-model comparisons such as AeroCom, and points out one of the many inter-model differences that can contribute to the overall spread among models.

  16. The Effect of Direct and Indirect Corrective Feedback on Iranian EFL Learners' Spelling Errors

    Science.gov (United States)

    Ghandi, Maryam; Maghsoudi, Mojtaba

    2014-01-01

    The aim of the current study was to investigate the impact of indirect corrective feedback on promoting Iranian high school students' spelling accuracy in English (as a foreign language). It compared the effect of direct feedback with indirect feedback on students' written work dictated by their teacher from Chicken Soup for the Mother and…

  17. Radiation monitoring by radiation effect of aerosol

    International Nuclear Information System (INIS)

    The high energy and high intensity accelerator facilities need the radiation monitoring with temporal and spatial resolutions. Numerical estimations are made for the radiation monitoring using the sampling method of aerosol Alanine. The aerosol Alanine put into the monitoring area through the duct. The intensity of radicals in the collected throughput Alanine of about 50 mg after passing through the monitoring area is measured by the ESR (Electron Spin Resonance) method. Key parameters in the system are the aerosol particle diameter and its intensity, the duct diameter and length, and the aerosol flow rate inside the duct. The maximum dose rate more than 108 Gy/h is possible to measure assuming the duct of 100 cm2 in area and 10 m in length, and the aerosol flow rate of 1000 L/min. The temporal resolution of the order of minutes is obtainable when the aerosol particle size is 0.1 μm. As a result of numerical estimation based on empirical simulations, it is to be promising to apply a proposed scheme to the radiation monitoring for accelerator fields. (Y. Tanaka)

  18. A case study on biomass burning aerosols: effects on aerosol optical properties and surface radiation levels

    Directory of Open Access Journals (Sweden)

    A. Arola

    2007-08-01

    Full Text Available In spring 2006, biomass burning aerosols from eastern Europe were transported extensively to Finland, and to other parts of northern Europe. They were observed as far as in the European Arctic. In the first part of this paper, temporal and spatial evolution and transport of these biomass burning aerosols are monitored with MODIS retrieved aerosol optical depth (AOD imagery at visible wavelengths (0.55 μm. Comparison of MODIS and AERONET AOD is conducted at Tõravere, Estonia. Then trajectory analyses, as well as MODIS Fire Mapper products are used to better understand the type and origin of the air masses. During the studied four-week period AOD values ranged from near zero up to 1.2 at 0.55 μm and the linear correlation between MODIS and AERONET was very high (~0.97. Temporal variability observed within this four-week period was also rather well explained by the trajectory analysis in conjunction with the fire detections produced by the MODIS Rapid Response System. In the second part of our study, the surface measurements of global and UV radiation at Jokioinen, Finland are used to study the effect of this haze episode on the levels of surface radiation. We found reductions up to 35% in noon-time surface UV irradiance (at 340 nm as compared to typical aerosol conditions. For global (total solar radiation, the reduction was always smaller, in line with the expected wavelength dependence of the aerosol effect.

  19. Effect of CALIPSO Cloud Aerosol Discrimination (CAD) Confidence Levels on Observations of Aerosol Properties near Clouds

    Science.gov (United States)

    Yang, Weidong; Marshak, Alexander; Varnai, Tamas; Liu, Zhaoyan

    2012-01-01

    CALIPSO aerosol backscatter enhancement in the transition zone between clouds and clear sky areas is revisited with particular attention to effects of data selection based on the confidence level of cloud-aerosol discrimination (CAD). The results show that backscatter behavior in the transition zone strongly depends on the CAD confidence level. Higher confidence level data has a flatter backscatter far away from clouds and a much sharper increase near clouds (within 4 km), thus a smaller transition zone. For high confidence level data it is shown that the overall backscatter enhancement is more pronounced for small clear-air segments and horizontally larger clouds. The results suggest that data selection based on CAD reduces the possible effects of cloud contamination when studying aerosol properties in the vicinity of clouds.

  20. Estimation of Asian Dust Aerosol Effect on Cloud Radiation Forcing Using Fu-Liou Radiative Model and CERES Measurements

    Science.gov (United States)

    Su, Jing; Huang, Jianping; Fu, Qiang; Minnis, Patrick; Ge, Jinming; Bi, Jianrong

    2008-01-01

    The impact of Asian dust on cloud radiative forcing during 2003-2006 is studied by using the Earth's Radiant Energy Budget Scanner (CERES) data and the Fu-Liou radiative transfer model. Analysis of satellite data shows that the dust aerosol significantly reduced the cloud cooling effect at TOA. In dust contaminated cloudy regions, the 4-year mean values of the instantaneous shortwave, longwave and net cloud radiative forcing are -138.9, 69.1, and -69.7 Wm(sup -2), which are 57.0, 74.2, and 46.3%, respectively, of the corresponding values in more pristine cloudy regions. The satellite-retrieved cloud properties are significantly different in the dusty regions and can influence the radiative forcing indirectly. The contributions to the cloud radiation forcing by the dust direct, indirect and semi-direct effects are estimated using combined satellite observations and Fu-Liou model simulation. The 4-year mean value of combination of indirect and semi-direct shortwave radiative forcing (SWRF) is 82.2 Wm(sup -2), which is 78.4% of the total dust effect. The direct effect is only 22.7 Wm(sup -2), which is 21.6% of the total effect. Because both first and second indirect effects enhance cloud cooling, the aerosol-induced cloud warming is mainly the result of the semi-direct effect of dust.

  1. Total aerosol effect: radiative forcing or radiative flux perturbation?

    Directory of Open Access Journals (Sweden)

    U. Lohmann

    2010-04-01

    Full Text Available Uncertainties in aerosol radiative forcings, especially those associated with clouds, contribute to a large extent to uncertainties in the total anthropogenic forcing. The interaction of aerosols with clouds and radiation introduces feedbacks which can affect the rate of precipitation formation. In former assessments of aerosol radiative forcings, these effects have not been quantified. Also, with global aerosol-climate models simulating interactively aerosols and cloud microphysical properties, a quantification of the aerosol forcings in the traditional way is difficult to define properly. Here we argue that fast feedbacks should be included because they act quickly compared with the time scale of global warming. We show that for different forcing agents (aerosols and greenhouse gases the radiative forcings as traditionally defined agree rather well with estimates from a method, here referred to as radiative flux perturbations (RFP, that takes these fast feedbacks and interactions into account. Based on our results, we recommend RFP as a valid option to compare different forcing agents, and to compare the effects of particular forcing agents in different models.

  2. Total aerosol effect: radiative forcing or radiative flux perturbation?

    Directory of Open Access Journals (Sweden)

    D. Koch

    2009-11-01

    Full Text Available Uncertainties in aerosol radiative forcings, especially those associated with clouds, contribute to a large extent to uncertainties in the total anthropogenic forcing. The interaction of aerosols with clouds and radiation introduces feedbacks which can affect the rate of rain formation. In former assessments of aerosol radiative forcings, these effects have not been quantified. Also, with global aerosol-climate models simulating interactively aerosols and cloud microphysical properties, a quantification of the aerosol forcings in the traditional way is difficult to properly define. Here we argue that fast feedbacks should be included because they act quickly compared with the time scale of global warming. We show that for different forcing agents (aerosols and greenhouse gases the radiative forcings as traditionally defined agree rather well with estimates from a method, here referred to as radiative flux perturbations (RFP, that takes these fast feedbacks and interactions into account. Based on our results, we recommend RFP as a valid option to compare different forcing agents, and to compare the effects of particular forcing agents in different models.

  3. Atmospheric impact of the 1783-1784 Laki Eruption: Part II Climatic effect of sulphate aerosol

    Science.gov (United States)

    Highwood, E. J.; Stevenson, D. S.

    2003-03-01

    The long 1783-1784 eruption of Laki, in southern Iceland, was one of the first eruptions to have been linked to an observed climate anomaly, having been held responsible for cold temperatures over much of the Northern Hemisphere in the period 1783-1785. Results from the first climate model simulation of the impact of the 1783-1784 fissure eruption are presented. Using sulphate aerosol fields produced in a companion chemical transport model simulation by Stevenson et al. (2003), the radiative forcing and climate response due to the aerosol are calculated here using the Reading Intermediate General Circulation Model (IGCM). The peak Northern Hemisphere mean direct radiative forcing is -5.5 Wm-2 in August 1783. The radiative forcing dies away quickly as the emissions from the volcano decrease; however, a small forcing remains over the Mediterranean until March 1784. There is little forcing in the Southern Hemisphere. There is shown to be an uncertainty of at least 50% in the direct radiative forcing due to assumptions concerning relative humidity and the sophistication of the radiative transfer code used. The indirect effects of the Laki aerosol are potentially large but essentially unquantifiable at the present time. In the IGCM at least, the aerosol from the eruption produces a climate response that is spatially very variable. The magnitude of the Northern Hemisphere annual mean anomaly for 1783 is -0.21 K, statistically significant at the 95% level and in reasonable agreement with the available observations.

  4. Indirect Cloud Effects from Biomass Burning Smoke in the Arctic and Subarctic: Insights from Multiple In-Situ Datasets

    Science.gov (United States)

    Zamora, L. M.; Kahn, R. A.; Anderson, B. E.; McFarquhar, G. M.; Wisthaler, A.; Zelenyuk, A.

    2014-12-01

    The incidence of wildfires in the Arctic and subarctic is increasing; in boreal North America, for example, the burned area is expected to increase by 200- 300% over the next 50-100 years. In some cases, local and long-range smoke transported to the Arctic has already increased aerosol concentrations twofold, which previous studies suggest could have a large effect on cloud microphysics, lifetime, albedo, and precipitation. However, the interactions between smoke particles and clouds remain poorly understood, in part due to the confounding influence of varying meteorological and surface conditions. Here, we use data from several aircraft campaigns in the Arctic and subarctic (the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites-B campaign (ARCTAS-B), the Indirect and Semi-Direct Aerosol Campaign (ISDAC), and the First ISCCP Regional Experiment Arctic Clouds Experiment (FIRE.ACE)) to compare cloud microphysics in liquid, ice, and mixed-phase clouds sampled at similar temperature and pressure in the presence and absence of biomass burning smoke. Care is taken to place findings in context of meteorological conditions. Preliminary data from the ARCTAS-B campaign suggest a noticeable impact of smoke on cloud properties in the liquid phase, consistent with the Twomey effect (smaller cloud droplet radius), and greater liquid water path and estimated cloud optical depth. Continuing work involves using the combination of field cases and satellite data from MISR, MODIS, CALIPSO, and other sources to more fully characterize the impact of smoke on Arctic clouds.

  5. Redistributive effects of the shift from personal income taxes to indirect taxes: Belgium 1988-93.

    OpenAIRE

    Andrá Decoster; Guy Van Camp

    2001-01-01

    Between 1988 and 1993, the Belgian personal income tax system and the indirect tax system were reformed to a considerable extent. We use microsimulation models to investigate the impact of the reform on the liability progression and the redistributive effect of the combined tax system. The redistributive effect of personal income taxes decreased, notwithstanding an increase in liability progression. For indirect taxes, both the liability regressivity and the reverse redistributive effect have...

  6. Extensive closed cell marine stratocumulus downwind of Europe—A large aerosol cloud mediated radiative effect or forcing?

    Science.gov (United States)

    Goren, Tom; Rosenfeld, Daniel

    2015-06-01

    Marine stratocumulus clouds (MSC) cover large areas over the oceans and possess super sensitivity of their cloud radiative effect to changes in aerosol concentrations. Aerosols can cause transitions between regimes of fully cloudy closed cells and open cells. The possible role of aerosols in cloud cover has a big impact on the amount of reflected solar radiation from the clouds, thus potentially constitutes very large aerosol indirect radiative effect, which can exceed 100 Wm-2. It is hypothesized that continentally polluted clouds remain in closed cells regime for longer time from leaving continent and hence for longer distance away from land, thus occupying larger ocean areas with full cloud cover. Attributing this to anthropogenic aerosols would imply a very large negative radiative forcing with a significant climate impact. This possibility is confirmed by analyzing a detailed case study based on geostationary and polar-orbiting satellite observations of the microphysical and dynamical evolution of MSC. We show that large area of closed cells was formed over the northeast Atlantic Ocean downwind of Europe in a continentally polluted air mass. The closed cells undergo cleansing process that was tracked for 3.5 days that resulted with a rapid transition from closed to open cells once the clouds started drizzling heavily. The mechanism leading to the eventual breakup of the clouds due to both meteorological and aerosol considerations is elucidated. We termed this cleansing and cloud breakup process maritimization. Further study is needed to assess the climatological significance of such situations.

  7. Modeling Trends in Aerosol Direct Radiative Effects over the Northern Hemisphere using a Coupled Meteorology-Chemistry Model

    Science.gov (United States)

    Mathur, R.; Pleim, J.; Wong, D.; Hogrefe, C.; Xing, J.; Wei, C.; Gan, M.

    2013-12-01

    While aerosol radiative effects have been recognized as some of the largest sources of uncertainty among the forcers of climate change, the verification of the spatial and temporal variability of the magnitude and directionality of aerosol radiative forcing has remained challenging. A detailed investigation of the processes regulating aerosol distributions, their optical properties, and their radiative effects and verification of their simulated effects for past conditions relative to measurements is needed in order to build confidence in the estimates of the projected impacts arising from changes in both anthropogenic forcing and climate change. Anthropogenic emissions of primary aerosol and gaseous precursors have witnessed dramatic changes over the past two decades across the northern hemisphere. During the period 1990-2010, SO2 and NOx emissions across the US have reduced by about 66% and 50%, respectively, mainly due to Title IV of the U.S. Clean Air Act Amendments (CAA). In contrast, anthropogenic emissions have increased dramatically in many developing regions during this period. We conduct a systematic investigation of changes in anthropogenic emissions of primary aerosols and gaseous precursors over the past two decades, their impacts on trends and spatial heterogeneity in anthropogenic aerosol loading across the northern hemisphere troposphere, and subsequent impacts on regional radiation budgets. The coupled WRF-CMAQ model is applied for selected time periods spanning the period 1990-2010 over a domain covering the northern hemisphere and a nested finer resolution continental U.S. domain. The model includes detailed treatment of direct effects of aerosols on photolysis rates as well as on shortwave radiation. Additionally, treatment of aerosol indirect effects on clouds has also recently been implemented. A methodology is developed to consistently estimate U.S. emission inventories for the 20-year period accounting for air quality regulations as well as

  8. Tropospheric Aerosols

    Science.gov (United States)

    Buseck, P. R.; Schwartz, S. E.

    2003-12-01

    m, PM10=1.1 μg m-3; estimated coefficient of light scattering by particulate matter, σep, at 570 nm=12 Mm-1). (b) High aerosol concentration (PM2.5=43.9 μg m-3; PM10=83.4 μg m-3; estimated σep at 570 nm=245 Mm-1) (reproduced by permission of National Park Service, 2002). Although comprising only a small fraction of the mass of Earth's atmosphere, aerosol particles are highly important constituents of the atmosphere. Special interest has focused on aerosols in the troposphere, the lowest part of the atmosphere, extending from the land or ocean surface typically to ˜8 km at high latitudes, ˜12 km in mid-latitudes, and ˜16 km at low latitudes. That interest arises in large part because of the importance of aerosol particles in geophysical processes, human health impairment through inhalation, environmental effects through deposition, visibility degradation, and influences on atmospheric radiation and climate.Anthropogenic aerosols are thought to exert a substantial influence on Earth's climate, and the need to quantify this influence has sparked much of the current interest in and research on tropospheric aerosols. The principal mechanisms by which aerosols influence the Earth radiation budget are scattering and absorbing solar radiation (the so-called "direct effects") and modifying clouds and precipitation, thereby affecting both radiation and hydrology (the so-called "indirect effects"). Light scattering by aerosols increases the brightness of the planet, producing a cooling influence. Light-absorbing aerosols such as black carbon exert a warming influence. Aerosols increase the reflectivity of clouds, another cooling influence. These radiative influences are quantified as forcings, where a forcing is a perturbation to the energy balance of the atmosphere-Earth system, expressed in units of watts per square meter, W m-2. A warming influence is denoted a positive forcing, and a cooling influence, negative. The radiative direct and indirect forcings by

  9. Effect of aging on morphology, hygroscopicity, and optical properties of soot aerosol

    Science.gov (United States)

    Khalizov, A. F.; Xue, H.; Pagels, J.; McMurry, P. H.; Zhang, R.

    2009-12-01

    Soot from incomplete combustion represents one of the major forms of particulate matter pollution, profoundly impacting human health, air quality, and climate. The direct and indirect radiative effects of soot aerosol depend on particle composition and morphology, which may vary significantly when aerosol is subjected to atmospheric aging. We will present an overview of a comprehensive set of experimental measurements performed in our laboratory at Texas A&M to study the effect of internal mixing with atmospheric species on morphology, hygroscopicity, and optical properties of combustion soot. In our experiments, size-classified soot aerosol was exposed to 0.1 - 1000 ppb (part per billion) mixing ratios of sulfuric acid and dicarboxylic organic acids and resulting changes particle morphology and mixing state under dry and humid conditions were characterized through mass-mobility measurements by aerosol particle mass analyzer (APM) and tandem differential mobility analyzer (TDMA). Light absorption and scattering cross-sections for well-characterized fresh and coated soot aerosol were derived using a cavity ring-down spectrometer and an integrating nephelometer in order to assess the effect of atmospheric processing on the radiative properties of atmospheric soot. Internally mixed soot shows significant changes in particle morphology, increasing with the mass fraction of the coating material and relative humidity. Restructuring was the strongest for aggregates coated by sulfuric and glutaric acids whereas succinic acid coating did not result in observable morphology change. Sulfuric acid - coated particles experienced large hygroscopic growth at sub-saturated conditions and activated to cloud droplets at atmospherically relevant supersaturations. Furthermore, coating and subsequent hygroscopic growth considerably altered the optical properties of soot aerosol, increasing light scattering and absorption cross-sections. We found that irreversible restructuring of soot

  10. Reflex effects of aerosolized histamine on phrenic nerve activity.

    OpenAIRE

    Pack, A I; Hertz, B C; Ledlie, J F; Fishman, A. P.

    1982-01-01

    Studies were conducted in anesthetized, paralyzed dogs on the effect of aerosolized histamine on phrenic nerve activity. The paralyzed dogs were ventilated in phase with their recorded phrenic nerve activity at a constant inspiratory flow-rate, using a cycle-triggered ventilator. Phrenic nerve activity was measured before and during administration of aerosolized histamine while the inspiratory flow-rate and arterial blood gases were kept constant. In addition, before and after histamine, phre...

  11. Effect of tropospheric aerosols on environment

    Energy Technology Data Exchange (ETDEWEB)

    Indira, K. [Indian Institute of Tropical Meterology, Pune (India)

    1995-12-31

    The primary mechanism by which aerosols influences the environment is through changes in the amount of energy reaching the ground and the energy diffusing back to space. Keeping the above in view, a study has been undertaken to observe the effect of fire from an oil well at Pasarlapudi near Amalapuram, situated almost in the middle of the coastal Andhra belt, on environment. Fire started from an oil well at Pasarlapudi (16{degrees}N 82{degrees}E) near Amalapuram in Andhra Pradesh on 8 January 1995 and continues till today. For the above study daily maximum and minimum temperatures in celsius and rainfall in mm were collected from India Meteorological Department for two stations Kakinada and Machilipatnam from 19 January 1995 to 1 March 1995. It is seen from the above data at both Kakinada and Machilipatnam from 19 January to 1 February 1995 a decrease in minimum temperature from 0.5{degrees}C to 1.0{degrees}C. There is not much change in maximum temperature. 35 mm of excess rainfall was reported in coastal Andhra Pradesh from 1 Jan. to 25 Jan 1995 when the fire from the oil well was at maximum intensity. Some places near the Pasarlapudi reported rain with black carbon particles during third week of January. Pictures of the raging fire show a jet of burning gas extending into the atmosphere. The accompanying heat and smoke from the oil well fire could have led to cloud formation and rain containing black carbon particles in coastal belt of Andhra Pradesh.

  12. Indirect effects of overfishing on Caribbean reefs: sponges overgrow reef-building corals

    OpenAIRE

    Tse-Lynn Loh; Steven E. McMurray; Henkel, Timothy P.; Jan Vicente; Joseph R Pawlik

    2015-01-01

    Consumer-mediated indirect effects at the community level are difficult to demonstrate empirically. Here, we show an explicit indirect effect of overfishing on competition between sponges and reef-building corals from surveys of 69 sites across the Caribbean. Leveraging the large-scale, long-term removal of sponge predators, we selected overfished sites where intensive methods, primarily fish-trapping, have been employed for decades or more, and compared them to sites in remote or marine prot...

  13. Indirect Network Effects and the Impact of Trade Liberalization: A Note

    OpenAIRE

    Kazumichi, Iwasa; Kikuchi, Toru

    2008-01-01

    Indirect network effects exist when the utility of consumers is increasing in the variety of complementary software products available for use with an electronic hardware device. In this note, we examine how trade liberalization affects production structure in the presence of indirect network effects. For these purposes we construct a simple two-country model of trade with two incompatible hardware technologies. It is shown that, given that both types of hardware exist before trade liberaliza...

  14. Spatially complex land change: The Indirect effect of Brazil's agricultural sector on land use in Amazonia

    OpenAIRE

    Richards, Peter D.; Walker, Robert T.; Arima, Eugenio Y.

    2014-01-01

    Soybean farming has brought economic development to parts of South America, as well as environmental hopes and concerns. A substantial hope resides in the decoupling of Brazil's agricultural sector from deforestation in the Amazon region, in which case expansive agriculture need not imply forest degradation. However, concerns have also been voiced about the potential indirect effects of agriculture. This article addresses these indirect effects forthe case of the Brazilian Amazon since 2002. ...

  15. Predicted climate change alters the indirect effect of predators on an ecosystem process.

    Science.gov (United States)

    Lensing, Janet R; Wise, David H

    2006-10-17

    Changes in rainfall predicted to occur with global climate change will likely alter rates of leaf-litter decomposition through direct effects on primary decomposers. In a field experiment replicated at two sites, we show that altered rainfall may also change how cascading trophic interactions initiated by arthropod predators in the leaf litter indirectly influence litter decomposition. On the drier site there was no interaction between rainfall and the indirect effect of predators on decomposition. In contrast, on the moister site spiders accelerated the disappearance rate of deciduous leaf litter under low rainfall, but had no, or possibly a negative, indirect effect under high rainfall. Thus, changes resulting from the more intense hydrological cycle expected to occur with climate change will likely influence how predators indirectly affect an essential ecosystem process. PMID:17023538

  16. Hidden risks and benefits of natural enemy-mediated indirect effects.

    Science.gov (United States)

    Kaser, Joe M; Ode, Paul J

    2016-04-01

    Polyphagous natural enemies can mediate a variety of indirect interactions between resource populations. Such indirect interactions are often reciprocally negative (i.e. apparent competition), but the sign of effects between resource populations can be any combination of positive (+), negative (-), or neutral (0). In this article we focus on parasitoids to illustrate the importance of natural enemy-mediated indirect interactions in predicting risk and efficacy in biological control. We review recent findings to illustrate how an improved understanding of parasitoid behavioral ecology may increase model accuracy. PMID:27436655

  17. Comprehensive tool for calculation of radiative fluxes: illustration of shortwave aerosol radiative effect sensitivities to the details in aerosol and underlying surface characteristics

    OpenAIRE

    Derimian, Yevgeny; Dubovik, Oleg; Huang, Xin; Lapyonok, Tatyana; Litvinov, Pavel; Kostinski, Alex B.; Dubuisson, Philippe; Ducos, Fabrice

    2016-01-01

    The evaluation of aerosol radiative effect on broadband hemispherical solar flux is often performed using simplified spectral and directional scattering characteristics of atmospheric aerosol and underlying surface reflectance. In this study we present a rigorous yet fast computational tool that accurately accounts for detailed variability of both spectral and angular scattering properties of aerosol and surface reflectance in calculation of direct aerosol radiative effect. ...

  18. Aerosol-radiation-cloud interactions in a regional coupled model: the effects of convective parameterisation and resolution

    Science.gov (United States)

    Archer-Nicholls, Scott; Lowe, Douglas; Schultz, David M.; McFiggans, Gordon

    2016-05-01

    concentration of clouds. However, the changes to cloud properties had negligible impact on the net radiative balance in either domain, with or without convective parameterisation. The sensitivity to the uncertainties relating to the semi-direct effect was greater than any other observable indirect effects. Although the version of WRF-Chem distributed to the community currently lacks aerosol-cloud interactions in parameterised clouds, the results of this study suggest a greater priority for the development is to improve the modelling of semi-direct effects by reducing the uncertainties relating to the use of convective parameterisation and resolution before WRF-Chem can reliably quantify the regional impacts of aerosols.

  19. Spatially complex land change: The Indirect effect of Brazil's agricultural sector on land use in Amazonia.

    Science.gov (United States)

    Richards, Peter D; Walker, Robert T; Arima, Eugenio Y

    2014-11-01

    Soybean farming has brought economic development to parts of South America, as well as environmental hopes and concerns. A substantial hope resides in the decoupling of Brazil's agricultural sector from deforestation in the Amazon region, in which case expansive agriculture need not imply forest degradation. However, concerns have also been voiced about the potential indirect effects of agriculture. This article addresses these indirect effects forthe case of the Brazilian Amazon since 2002. Our work finds that as much as thirty-two percent of deforestation, or the loss of more than 30,000 km(2) of Amazon forest, is attributable, indirectly, to Brazil's soybean sector. However, we also observe that the magnitude of the indirect impact of the agriculture sector on forest loss in the Amazon has declined markedly since 2006. We also find a shift in the underlying causes of indirect land use change in the Amazon, and suggest that land appreciation in agricultural regions has supplanted farm expansions as a source of indirect land use change. Our results are broadly congruent with recent work recognizing the success of policy changes in mitigating the impact of soybean expansion on forest loss in the Amazon. However, they also caution that the soybean sector may continue to incentivize land clearings through its impact on regional land markets. PMID:25492993

  20. Dust aerosol forward scattering effects on ground-based aerosol optical depth retrievals

    International Nuclear Information System (INIS)

    Monte Carlo radiative transfer calculations are performed to examine the forward scattering effects on retrievals of dust aerosol optical depth (AOD) from ground-based instruments. We consider dust aerosols with different AOD, effective radius and imaginary refractive index at 0.5 μm wavelength. The shape of dust aerosols is assumed to be spheroids and the equivalent spheres that preserve both volume and projected area (V/P) are also considered. The single-scattering albedos and asymmetry factors of spheroids and V/P-equivalent spheres have small differences, but the scattering phase functions are very different for the scattering angle range ∼90-180o. The relative errors of retrieved AOD caused by forward scattering effects due to the differences between the single-scattering properties of spheroids and spheres are similar. It is shown that at solar zenith angle (SZA) smaller than ∼70o the effect of the forward scattering is generally small although the relative errors in retrieved AOD can be as large as -10% when re=2. However, the largest relative errors, which can reach -40%, appear at high SZA (>∼70o) with AOD larger than 1. This is not caused by the increase of forward scattering intensity, but is due to the strong attenuation of solar direct beam.

  1. Direct and indirect effects of paliperidone extended-release tablets on negative symptoms of schizophrenia

    Science.gov (United States)

    Turkoz, Ibrahim; Bossie, Cynthia A; Dirks, Bryan; Canuso, Carla M

    2008-01-01

    Direct and indirect effects of the new psychotropic paliperidone extended-release (paliperidone ER) tablets on negative symptom improvement in schizophrenia were investigated using path analysis. A post hoc analysis of pooled data from three 6-week, double-blind, placebo-controlled studies of paliperidone ER in patients experiencing acute exacerbation was conducted. Regression analysis explored relationships between baseline/study characteristics and negative symptoms. Change in Positive and Negative Syndrome Scale (PANSS) negative factor score at endpoint was the dependent variable; explanatory variables included demographic and clinical characteristics. Path analysis determined direct and indirect effects of treatment on negative symptom change. Indirect mediators of negative symptom change in the model included changes in positive symptoms, anxiety/depression symptoms and movement disorders. Path analysis indicated that up to 33% of negative symptom improvement was a direct treatment effect. Indirect effects on negative symptoms were mediated through changes in positive symptoms (51%) and anxiety/depression symptoms (18%), whereas changes in movement disorders had a 2.1% inverse effect. Path analysis indicated that paliperidone ER has a direct effect on negative symptoms. Negative symptom improvement also was indirectly mediated via changes in positive and depressive symptoms. PMID:19183785

  2. Direct and indirect effects of paliperidone extended-release tablets on negative symptoms of schizophrenia

    Directory of Open Access Journals (Sweden)

    Ibrahim Turkoz

    2008-08-01

    Full Text Available Ibrahim Turkoz, Cynthia A Bossie, Bryan Dirks, Carla M CanusoOrtho-McNeil Janssen Scientific Affairs, LLC, Titusville, NJ, USAAbstract: Direct and indirect effects of the new psychotropic paliperidone extended-release (paliperidone ER tablets on negative symptom improvement in schizophrenia were investigated using path analysis. A post hoc analysis of pooled data from three 6-week, double-blind, placebo-controlled studies of paliperidone ER in patients experiencing acute exacerbation was conducted. Regression analysis explored relationships between baseline/study characteristics and negative symptoms. Change in Positive and Negative Syndrome Scale (PANSS negative factor score at endpoint was the dependent variable; explanatory variables included demographic and clinical characteristics. Path analysis determined direct and indirect effects of treatment on negative symptom change. Indirect mediators of negative symptom change in the model included changes in positive symptoms, anxiety/depression symptoms and movement disorders. Path analysis indicated that up to 33% of negative symptom improvement was a direct treatment effect. Indirect effects on negative symptoms were mediated through changes in positive symptoms (51% and anxiety/depression symptoms (18%, whereas changes in movement disorders had a 2.1% inverse effect. Path analysis indicated that paliperidone ER has a direct effect on negative symptoms. Negative symptom improvement also was indirectly mediated via changes in positive and depressive symptoms.Keywords: antipsychotic, paliperidone ER, path analysis, psychotropic, schizophrenia

  3. Organic photolysis reactions in tropospheric aerosols: effect on secondary organic aerosol formation and lifetime

    OpenAIRE

    Hodzic, A.; S. Madronich; Kasibhatla, P. S.; G. Tyndall; B. Aumont; Jimenez, J.L.; Lee-Taylor, J.; Orlando, J.

    2015-01-01

    This study presents the first modeling estimates of the potential effect of gas- and particle-phase organic photolysis reactions on the formation and lifetime of secondary organic aerosols (SOA). Typically only photolysis of smaller organic molecules (e.g. formaldehyde) for which explicit data exist is included in chemistry-climate models. Here, we specifically examine the photolysis of larger molecules that actively partition between the gas and particle phases. The chemical ...

  4. Organic photolysis reactions in tropospheric aerosols: effect on secondary organic aerosol formation and lifetime

    OpenAIRE

    Hodzic, A.; S. Madronich; Kasibhatla, P. S.; G. Tyndall; B. Aumont; Jimenez, J.L.; Lee-Taylor, J.; Orlando, J.

    2015-01-01

    This study presents the first modeling estimates of the potential effect of gas- and particle-phase organic photolysis reactions on the formation and lifetime of secondary organic aerosols (SOAs). Typically only photolysis of smaller organic molecules (e.g., formaldehyde) for which explicit data exist is included in chemistry–climate models. Here, we specifically examine the photolysis of larger molecules that actively partition between the gas and particle phases. The chemi...

  5. Direct and indirect effects of training vouchers for the unemployed

    OpenAIRE

    Huber, Martin; Lechner, Michael; Strittmatter, Anthony

    2015-01-01

    This paper evaluates the effect of a voucher award system for assignment into vocational training on the employment outcomes of unemployed voucher recipients in Germany, along with the causal mechanisms through which it operates. It assesses the direct effect of voucher assignment net of actual redemption, which may be driven by preference shaping/learning about (possibilities of) human capital investments or simply by costs of information gathering. Using a mediation analysis framework based...

  6. Direct and Indirect Effects of Training Vouchers for the Unemployed

    OpenAIRE

    Huber, Martin; Lechner, Michael; Strittmatter, Anthony

    2015-01-01

    This paper evaluates the effect of a voucher award system for assignment into vocational training on the employment outcomes of unemployed voucher recipients in Germany, along with the causal mechanisms through which it operates. It assesses the direct effect of voucher assignment net of actual redemption, which may be driven by preference shaping/learning about (possibilities of) human capital investments or simply by costs of information gathering. Using a mediation analysis framework based...

  7. Spatial distributions and seasonal cycles of aerosol climate effects in India seen in global climate-aerosol model

    Directory of Open Access Journals (Sweden)

    S. V. Henriksson

    2013-07-01

    Full Text Available Climate-aerosol interactions in India are studied by employing the global climate-aerosol model ECHAM5-HAM and the GAINS inventory for anthropogenic aerosol emissions. Seasonal cycles and spatial distributions of radiative forcing and the temperature and rainfall responses are presented for different model setups. While total aerosol radiative forcing is strongest in the summer, anthropogenic forcing is considerably stronger in winter than in summer. Local seasonal temperature anomalies caused by aerosols are mostly negative with some exceptions, e.g. Northern India in March–May and the eastern Himalayas in September–November. Rainfall increases due to the elevated heat pump (EHP mechanism and decreases due to solar dimming effects are studied. Aerosol light absorption does increase rainfall significantly in Northern India, but effects due to solar dimming and circulation work to cancel the increase. The total aerosol effect on rainfall is negative when considering all effects if assuming that aerosols have cooled the Northern Indian Ocean by 0.5 °K compared to the equator.

  8. A case study on biomass burning aerosols: effects on solar UV irradiance, retrieval of aerosol single scattering albedo

    Directory of Open Access Journals (Sweden)

    A. Bagheri

    2008-10-01

    Full Text Available The aerosol optical depth (AOD from biomass burning aerosols from eastern Europe was measured in Trondheim, Norway (63.43° N , 10.43° E in May 2006. The event was observed as far as the Arctic. In the first part of this paper, the surface measurements of direct and global UV radiation (and retrieved AOD are used to simulate the data using a radiative transfer model. Measured and simulated data were used to study the effect of biomass aerosol on the levels of surface UV radiation. We found reductions of up to 31%, 15% and 2% in direct, global and diffuse surface UV irradiance (at 350 nm, SZA=50°±0.5° as compared to typical aerosol conditions. In the second part of our study, surface measurements of global and direct irradiance at five wavelength in UVB and UVA (305, 313, 320, 340 and 380 nm were coupled with a radiative transfer model to produce values of aerosol single scattering albedo, ω. The aerosol single scattering albedo for biomass aerosols is compared to ω for background aerosols. The values of ω for biomass aerosols were 0.76 at 305 nm, 0.75 at 313 nm, 0.79 at 320 nm, 0.72 at 340 nm and 0.80 at 380 nm.

  9. Application of online-coupled WRF/Chem-MADRID in East Asia: Model evaluation and climatic effects of anthropogenic aerosols

    Science.gov (United States)

    Liu, Xu-Yan; Zhang, Yang; Zhang, Qiang; He, Ke-Bin

    2016-01-01

    The online-coupled Weather Research and Forecasting model with Chemistry with the Model of Aerosol Dynamics, Reaction, Ionization, and Dissolution (referred to as WRF/Chem-MADRID) is applied to simulate meteorological fields, air quality, and the direct and indirect effects of anthropogenic aerosols over East Asia in four months (January, April, July, and October) in 2008. Model evaluation against available surface and satellite measurements shows that despite some model biases, WRF/Chem-MADRID is able to reproduce reasonably well the spatial and seasonal variations of most meteorological fields and chemical concentrations. Large model biases for chemical concentrations are attributed to uncertainties in emissions and their spatial and vertical allocations, simulated meteorological fields, imperfectness of model representations of aerosol formation processes, uncertainties in the observations based on air pollution index, and the use of a coarse grid resolution. The results show that anthropogenic aerosols can reduce net shortwave flux at the surface by up to 40.5-57.2 W m-2, Temperature at 2-m by up to 0.5-0.8 °C, NO2 photolytic rates by up to 0.06-0.1 min-1 and the planetary boundary layer height by up to 83.6-130.4 m. Anthropogenic aerosols contribute to the number concentrations of aerosols by up to 6.2-8.6 × 104 cm-3 and the surface cloud concentration nuclei at a supersaturation of 0.5% by up to 1.0-1.6 × 104 cm-3. They increase the column cloud droplet number concentrations by up to 3.6-11.7 × 108 cm-2 and cloud optical thickness by up to 19.8-33.2. However, anthropogenic aerosols decrease daily precipitation in most areas by up to 3.9-18.6 mm during the 4 months. These results indicate the importance of anthropogenic aerosols in modulating regional climate changes in East Asia through aerosol direct and indirect effects, as well as the need to further improve the performance of online-coupled models.

  10. Importance of global aerosol modeling including secondary organic aerosol formed from monoterpene

    OpenAIRE

    Goto, Daisuke; Takemura, Toshihiko; Nakajima, Teruyuki

    2008-01-01

    A global three-dimensional aerosol transport-radiation model, coupled to an atmospheric general circulation model (AGCM), has been extended to improve the model process for organic aerosols, particularly secondary organic aerosols (SOA), and to estimate SOA contributions to direct and indirect radiative effects. Because the SOA formation process is complicated and unknown, the results in different model simulations include large differences. In this work, we simulate SOA production assuming v...

  11. Test Report: Direct and Indirect Lightning Effects on Composite Materials

    Science.gov (United States)

    Evans, R. W.

    1997-01-01

    Lightning tests were performed on composite materials as a part of an investigation of electromagnetic effects on the materials. Samples were subjected to direct and remote simulated lightning strikes. Samples included various thicknesses of graphite filament reinforced plastic (GFRP), material enhanced by expanded aluminum foil layers, and material with an aluminum honeycomb core. Shielding properties of the material and damage to the sample surfaces and joints were investigated. Adding expanded aluminum foil layers and increasing the thickness of GFRP improves the shielding effectiveness against lightning induced fields and the ability to withstand lightning strikes. A report describing the lightning strike tests performed by the U.S. Army Redstone Technical Test Center, Redstone Arsenal, AL, STERT-TE-E-EM, is included as an appendix.

  12. Indirect health effects of relative humidity in indoor environments.

    OpenAIRE

    Arundel, A.V.; Sterling, E M; Biggin, J H; Sterling, T.D.

    1986-01-01

    A review of the health effects of relative humidity in indoor environments suggests that relative humidity can affect the incidence of respiratory infections and allergies. Experimental studies on airborne-transmitted infectious bacteria and viruses have shown that the survival or infectivity of these organisms is minimized by exposure to relative humidities between 40 and 70%. Nine epidemiological studies examined the relationship between the number of respiratory infections or absenteeism a...

  13. Trait-Mediated Indirect Effects of Phorid Flies on Ants

    OpenAIRE

    Hsun-Yi Hsieh; Ivette Perfecto

    2012-01-01

    This paper provides a synthesis of the ecological impact of phorid fly parasitoids on ants. We find the most important impact of phorids on ants to be trait-mediated effects. Phorids diminish the foraging activity of ants, frequently reducing the number and average size of foragers and reducing the amount of food retrieved by a colony. However, ants' coping mechanisms include changing foraging site and time. Phorids can also affect competition, especially through changes in the ability of the...

  14. Climate change and wildlife health: direct and indirect effects

    Science.gov (United States)

    Hofmeister, Erik; Rogall, Gail Moede; eWsenberg, Kathy; Abbott, Rachel; Work, Thierry; Schuler, Krysten; Sleeman, Jonathan; Winton, James

    2010-01-01

    Climate change will have significant effects on the health of wildlife, domestic animals, and humans, according to scientists. The Intergovernmental Panel on Climate Change projects that unprecedented rates of climate change will result in increasing average global temperatures; rising sea levels; changing global precipitation patterns, including increasing amounts and variability; and increasing midcontinental summer drought (Intergovernmental Panel on Climate Change, 2007). Increasing temperatures, combined with changes in rainfall and humidity, may have significant impacts on wildlife, domestic animal, and human health and diseases. When combined with expanding human populations, these changes could increase demand on limited water resources, lead to more habitat destruction, and provide yet more opportunities for infectious diseases to cross from one species to another. Awareness has been growing in recent years about zoonotic diseases— that is, diseases that are transmissible between animals and humans, such as Lyme disease and West Nile virus. The rise of such diseases results from closer relationships among wildlife, domestic animals, and people, allowing more contact with diseased animals, organisms that carry and transmit a disease from one animal to another (vectors), and people. Disease vectors include insects, such as mosquitoes, and arachnids, such as ticks. Thus, it is impossible to separate the effects of global warming on wildlife from its effects on the health of domestic animals or people. Climate change, habitat destruction and urbanization, the introduction of exotic and invasive species, and pollution—all affect ecosystem and human health. Climate change can also be viewed within the context of other physical and climate cycles, such as the El Niño Southern Oscillation (El Niño), the North Atlantic Oscillation, and cycles in solar radiation that have profound effects on the Earth’s climate. The effects of climate change on wildlife

  15. The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer Monsoon

    Directory of Open Access Journals (Sweden)

    L. Guo

    2013-02-01

    Full Text Available The response of East Asian Summer Monsoon (EASM precipitation to long term changes in regional anthropogenic aerosols (sulphate and black carbon is explored in an atmospheric general circulation model, the atmospheric component of the UK High-Resolution Global Environment Model v1.2 (HiGAM. Separately, sulphur dioxide (SO2 and black carbon (BC emissions in 1950 and 2000 over East Asia are used to drive model simulations, while emissions are kept constant at year 2000 level outside this region. The response of the EASM is examined by comparing simulations driven by aerosol emissions representative of 1950 and 2000. The aerosol radiative effects are also determined using an off-line radiative transfer model. During June, July and August, the EASM was not significantly changed as either SO2 or BC emissions increased from 1950 to 2000 levels. However, in September, precipitation is significantly decreased by 26.4% for sulphate aerosol and 14.6% for black carbon when emissions are at the 2000 level. Over 80% of the decrease is attributed to changes in convective precipitation. The cooler land surface temperature over China in September (0.8 °C for sulphate and 0.5 °C for black carbon due to increased aerosols reduces the surface thermal contrast that supports the EASM circulation. However, mechanisms causing the surface temperature decrease in September are different between sulphate and BC experiments. In the sulphate experiment, the sulphate direct and the 1st indirect radiative effects contribute to the surface cooling. In the BC experiment, the BC direct effect is the main driver of the surface cooling, however, a decrease in low cloud cover due to the increased heating by BC absorption partially counteracts the direct effect. This results in a weaker land surface temperature response to BC changes than to sulphate changes. The resulting precipitation response is also weaker, and the responses of the monsoon circulation

  16. On the aerosol-cloud relationship at a high-alpine site

    Energy Technology Data Exchange (ETDEWEB)

    Baltensperger, U.; Schwikowski, M.; Jost, D.T.; Nyeki, S.; Gaeggeler, H.W. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    Field experiments at the Jungfraujoch showed that during the presence of a cloud, most of the aerosol mass is transferred into the cloud phase. This results in smaller cloud droplets for increasing aerosol concentration, which increases the albedo of clouds (known as the indirect effect of climate forcing by aerosol particles). (author) 1 fig., 4 refs.

  17. Aerosol Climate Effects: Local Radiative Forcing and Column Closure Experiments

    Science.gov (United States)

    Russell, P. B.; Bergstrom, Robert W.; Kinne, S. A.

    2000-01-01

    In an effort to reduce uncertainties in climate change predictions, experiments are being planned and conducted to measure anthropogenic aerosol properties and effects, including effects on radiative fields. The global average, direct anthropogenic aerosol effect on upwelling shortwave fluxes is estimated to be about +1/2 W/sq m, whereas errors in flux changes measured with airborne and spaceborne radiometers are 2 to 8 W/sq m or larger. This poses the question of whether flux changes expected in field experiments will be large enough to measure accurately. This paper obtains a new expression for the aerosol-induced change in upwelling flux, compares it to two-stream and adding-doubling (AD) results, and uses all three methods to estimate expected flux changes. The new expression accounts for the solar zenith angle dependences of aerosol transmission and reflection, as well as of surface albedo, all of which can have a strong effect in determining flux changes measured in field experiments. Despite its relative simplicity, the new expression gives results similar to previous two-stream results. Relative to AD results, it agrees within a few watts per square meter for the intermediate solar elevation angles where the flux changes peak (roughly 10 to 30 degrees), but it has negative errors for higher Sun and positive errors for lower Sun. All three techniques yield aerosol-induced changes in upwelling flux of +8 to +50 W/sq m for aerosol midvisible optical depths of 0.1 to 0.5. Because such aerosol optical depths occur frequently off the U.S. and European Atlantic coasts in summer, the flux changes they induce should be measurable by airborne, and possibly by spaceborne, radiometers, provided sufficient care is taken in experiment design (including measurements to separate aerosol radiative effects from those of absorbing gases). The expected flux changes are about 15 to 100 times larger than the global average flux change expected for the global average

  18. BAECC Biogenic Aerosols - Effects on Clouds and Climate

    Energy Technology Data Exchange (ETDEWEB)

    Petäjä, Tuukka [Univ. of Helsinki (Finland); Moisseev, Dmitri [Univ. of Helsinki (Finland); Sinclair, Victoria [Univ. of Helsinki (Finland); O' Connor, Ewan J. [Finnish Meteorological Institute, Helsinki (Finland); Manninen, Antti J. [Univ. of Helsinki (Finland); Levula, Janne [Univ. of Helsinki (Finland); Väänänen, Riikka [Univ. of Helsinki (Finland); Heikkinen, Liine [Univ. of Helsinki (Finland); Äijälä, Mikko [Univ. of Helsinki (Finland); Aalto, Juho [Univ. of Helsinki (Finland); Bäck, Jaana [University of Helsinki, Finland

    2015-11-01

    “Biogenic Aerosols - Effects on Clouds and Climate (BAECC)”, featured the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Program’s 2nd Mobile Facility (AMF2) in Hyytiälä, Finland. It operated for an 8-month intensive measurement campaign from February to September 2014. The main research goal was to understand the role of biogenic aerosols in cloud formation. One of the reasons to perform BAECC study in Hyytiälä was the fact that it hosts SMEAR-II (Station for Measuring Forest Ecosystem-Atmosphere Relations), which is one of the world’s most comprehensive surface in-situ observation sites in a boreal forest environment. The station has been measuring atmospheric aerosols, biogenic emissions and an extensive suite of parameters relevant to atmosphere-biosphere interactions continuously since 1996. The BAECC enables combining vertical profiles from AMF2 with surface-based in-situ SMEAR-II observations and allows the processes at the surface to be directly related to processes occurring throughout the entire tropospheric column. With the inclusion of extensive surface precipitation measurements, and intensive observation periods involving aircraft flights and novel radiosonde launches, the complementary observations of AMF2 and SMEAR-II provide a unique opportunity for investigating aerosol-cloud interactions, and cloud-to-precipitation processes. The BAECC dataset will initiate new opportunities for evaluating and improving models of aerosol sources and transport, cloud microphysical processes, and boundary-layer structures.

  19. Quantifying Aerosol influences on the Cloud Radiative Effect

    Science.gov (United States)

    Feingold, Graham; McComiskey, Allison; Sena, Elisa; Yamaguchi, Takanobu

    2016-04-01

    Although evidence of aerosol influences on the microphysical properties of shallow liquid cloud fields abounds, a rigorous assessment of aerosol effects on the radiative properties of these clouds has proved to be elusive because of adjustments in the evolving cloud system. We will demonstrate through large numbers of idealized large eddy simulation and 14 years of surface-based remote sensing at a continental US site that the existence of a detectable cloud microphysical response to aerosol perturbations is neither a necessary, nor a sufficient condition for detectability of a radiative response. We will use a new framework that focuses on the cloud field properties that most influence shortwave radiation, e.g., cloud fraction, albedo, and liquid water path. In this framework, scene albedo is shown to be a robust function of cloud fraction for a variety of cloud systems, and appears to be insensitive to averaging scale. The albedo-cloud fraction framework will be used to quantify the cloud radiative effect of shallow liquid clouds and to demonstrate (i) the primacy of cloud field properties such as cloud fraction and liquid water path for driving the cloud radiative effect; and (ii) that the co-variability between meteorological and aerosol drivers has a strong influence on the detectability of the cloud radiative effect, regardless of whether a microphysical response is detected. A broad methodology for systematically quantifying the cloud radiative effect will be presented.

  20. Behaviourally mediated indirect effects : interference competition increases predation mortality in foraging redshanks

    NARCIS (Netherlands)

    Minderman, J; Lind, J; Cresswell, W

    2006-01-01

    The effect of competition for a limiting resource on the population dynamics of competitors is usually assumed to operate directly through starvation, yet may also affect survival indirectly through behaviourally mediated effects that affect risk of predation. Thus, competition can affect more than

  1. Aerosol quantification with the Aerodyne Aerosol Mass Spectrometer: detection limits and ionizer background effects

    Directory of Open Access Journals (Sweden)

    F. Drewnick

    2008-10-01

    Full Text Available Systematic laboratory experiments were performed to investigate quantification of various species with two versions of the Aerodyne Aerosol Mass Spectrometer, a Q-AMS and a c-ToF-AMS. Here we present a new method to continuously determine the detection limits of the AMS analyzers during regular measurements, yielding DL information under various measurement conditions. Minimum detection limits range from 0.03 μg m−3 (nitrate, sulfate, and chloride up to 0.5 μg m−3 (organics for the Q-AMS. Those of the c-ToF-AMS are found between 0.003 μg m−3 (nitrate, sulfate and 0.03 μg m−3 (ammonium, organics. The DL values found for the c-ToF-AMS were ~10 times lower than those of the Q-AMS, mainly due to differences in ion duty cycle. Effects causing an increase of the detection limits include long-term instrument contamination, measurement of high aerosol mass concentrations and short-term instrument history. The self-cleaning processes which reduce the instrument background after measurement of large aerosol concentrations as well as the influences of increased instrument background on mass concentration measurements are discussed. Finally, improvement of detection limits by extension of averaging time intervals, selected or reduced ion monitoring, and variation of particle-to-background measurement ratio are investigated.

  2. Determining the Environmental Effects of Indirect Subsidies. A Methodological Approach with an Application to the Netherlands

    International Nuclear Information System (INIS)

    Up to now a clear theoretical and methodological framework for economic-environmental analysis of environmentally damaging subsidies is lacking. Environmentally damaging subsidies are all kinds of direct and indirect subsidies aimed at achieving a certain (often non-environmental) goal that produce negative external effects to the natural environment. This article develops a transparent method to determine the environmental impact of indirect government subsidies and derive policy lessons. This method has been applied to several major subsidies in the Netherlands, namely in agriculture, energy, and transport. The results reveal large environmental effects, which need to be taken seriously by policy makers. The method enables policy makers to evaluate the environmental impacts of indirect government subsidies

  3. Influence of observed diurnal cycles of aerosol optical depth on aerosol direct radiative effect

    Directory of Open Access Journals (Sweden)

    A. Arola

    2013-08-01

    Full Text Available The diurnal variability of aerosol optical depth (AOD can be significant, depending on location and dominant aerosol type. However, these diurnal cycles have rarely been taken into account in measurement-based estimates of aerosol direct radiative forcing (ADRF or aerosol direct radiative effect (ADRE. The objective of our study was to estimate the influence of diurnal aerosol variability at the top of the atmosphere ADRE estimates. By including all the possible AERONET sites, we wanted to assess the influence on global ADRE estimates. While focusing also in more detail on some selected sites of strongest impact, our goal was to also see the possible impact regionally. We calculated ADRE with different assumptions about the daily AOD variability: taking the observed daily AOD cycle into account and assuming diurnally constant AOD. Moreover, we estimated the corresponding differences in ADREs, if the single AOD value for the daily mean was taken from the the Moderate Resolution Imaging Spectroradiometer (MODIS Terra or Aqua overpass times, instead of accounting for the true observed daily variability. The mean impact of diurnal AOD variability on 24 h ADRE estimates, averaged over all AERONET sites, was rather small and it was relatively small even for the cases when AOD was chosen to correspond to the Terra or Aqua overpass time. This was true on average over all AERONET sites, while clearly there can be much stronger impact in individual sites. Examples of some selected sites demonstrated that the strongest observed AOD variability (the strongest morning afternoon contrast does not typically result in a significant impact on 24 h ADRE. In those cases, the morning and afternoon AOD patterns are opposite and thus the impact on 24 h ADRE, when integrated over all solar zenith angles, is reduced. The most significant effect on daily ADRE was induced by AOD cycles with either maximum or minimum AOD close to local noon. In these cases, the impact on

  4. Atmospheric impact of the 1783–1784 Laki Eruption: Part II Climatic effect of sulphate aerosol

    Directory of Open Access Journals (Sweden)

    E.-J. Highwood

    2003-01-01

    Full Text Available The long 1783-1784 eruption of Laki in southern Iceland, was one of the first eruptions to have been linked to an observed climate anomaly, having been held responsible for cold temperatures over much of the Northern Hemisphere in the period 1783-1785. Results from the first climate model simulation of the impact of a similar eruption to that of 1783-1784 are presented. Using sulphate aerosol fields produced in a companion chemical transport model simulation by Stevenson et al. (2003, the radiative forcing and climate response due to the aerosol are calculated here using the Reading Intermediate General Circulation Model (IGCM. The peak Northern Hemisphere mean direct radiative forcing is -5.5 Wm-2 in August 1783. The radiative forcing dies away quickly as the emissions from the volcano decrease; however, a small forcing remains over the Mediterranean until March 1784. There is little forcing in the Southern Hemisphere. There is shown to be an uncertainty of at least 50% in the direct radiative forcing due to assumptions concerning relative humidity and the sophistication of the radiative transfer code used. The indirect effects of the Laki aerosol are potentially large but essentially unquantifiable at the present time. In the IGCM at least, the aerosol from the eruption produces a climate response that is spatially very variable. The Northern Hemisphere mean temperature anomaly averaged over the whole of the calendar year containing most of the eruption is -0.21 K, statistically significant at the 95% level and in reasonable agreement with the available observations of the temperature during 1783.

  5. The effect of aerosol on radiation fog life-cycle

    Science.gov (United States)

    Romakkaniemi, Sami; Maalick, Zubair; Tonttila, Juha; Kuhn, Thomas; Kokkola, Harri

    2016-04-01

    Radiation fog is formed during the night under clear skies when emission of long wave radiation cools the surface and air above it. After formation, the development of fog is further influenced by longwave cooling and turbulence entrainment-detrainment at the top of the fog layer, and microphysical processes through droplet activation and sedimentation. After sunrise, the fog is dissipated due heating of the surface and the air above it. Like in the case of clouds, atmospheric aerosol particles also affect the properties of fog and together with meteorological conditions determine their life cycle from formation to dissipation. To explore how aerosols are affecting radiation fog properties and lifetime, we have used a Large Eddy Model with explicit representation of aerosol particles and aerosol-fog droplet interactions. Our results show that the fog droplet concentration increases with increasing aerosol concentration. In the early stages of fog formation the radiative cooling at the top of the fog controls the maximum water supersaturation and droplet formation in a similar manner than the updraft velocity does at the base of a cloud. The liquid water content in the fog is mainly determined by the droplet concentration as large droplets are efficiently removed through sedimentation. Thus, with increasing aerosol particle concentration, the more numerous, but smaller fog droplets increase the fog's optical depth and thereby delay the fog dissipation after sunrise, because the surface warms more slowly. This effect is further enhanced if turbulence inside the fog leads to secondary activation of droplets. Overall, the radiation fog dissipation in polluted conditions can be delayed up to hours when compared to clean conditions.

  6. Direct and indirect trophic effects of predator depletion on basal trophic levels.

    Science.gov (United States)

    Chen, Huili; Hagerty, Steven; Crotty, Sinead M; Bertness, Mark D

    2016-02-01

    Human population growth and development have heavily degraded coastal ecosystems with cascading impacts across multiple trophic levels. Understanding both the direct and indirect trophic effects of human activities is important for coastal conservation. In New England, recreational overfishing has triggered a regional trophic cascade. Predator depletion releases the herbivorous purple marsh crab from consumer control and leads to overgrazing of marsh cordgrass and salt marsh die-off. The direct and indirect trophic effects of predator depletion on basal trophic levels, however, are not understood. Using observational and experimental data, we examined the hypotheses that (1) direct trophic effects of predator depletion decrease meiofaunal abundance by releasing deposit feeding fiddler crabs from consumer control, and/or (2) indirect trophic effects of predator depletion increase meiofaunal abundance by releasing blue carbon via the erosion of centuries of accreted marsh peat. Experimental deposit feeder removal led to 23% higher meiofaunal density at die-off than at healthy sites, while reciprocally transplanting sediment from die-off and healthy sites revealed that carbon-rich die-off sediment increased meiofauna density by over 164%: six times stronger than direct trophic effects. Recovering sites had both carbon-rich sediment and reduced deposit feeding leading to higher meiofauna densities than both die-off and healthy sites. This suggests that consequences of the trophic downgrading of coastal habitats can be driven by both direct and indirect trophic mechanisms that may vary in direction and magnitude, making their elucidation dependent on experimental manipulations. PMID:27145609

  7. Possible effect of extreme solar energetic particle event of 20 January 2005 on polar stratospheric aerosols: direct observational evidence

    Directory of Open Access Journals (Sweden)

    I. A. Mironova

    2011-05-01

    Full Text Available Energetic cosmic rays are the main source of ionization of the low-middle atmosphere, leading to associated changes in atmospheric properties. Via the hypothetical influence of ionization on aerosol growth and facilitated formation of cloud condensation nuclei, this may be an important indirect link relating solar variability to climate. This effect is highly debated, however, since the proposed theoretical mechanisms still remain illusive and qualitative, and observational evidence is inconclusive and controversial. Therefore, important questions regarding the existence and magnitude of the effect, and particularly the fraction of aerosol particles that can be formed and grow large enough to influence cloud condensation nuclei (CCN, are still open. Here we present empirical evidence of the possible effect caused by cosmic rays upon polar stratospheric aerosols, based on a case study of an extreme solar energetic particle (SEP event of 20 January 2005. Using aerosol data obtained over polar regions from different satellites with optical instruments that were operating during January 2005, such as the Stratospheric Aerosol and Gas Experiment III (SAGE III, and Optical Spectrograph and Infrared Imaging System (OSIRIS, we found a significant simultaneous change in aerosol properties in both the southern and northern polar regions in temporal association with the SEP event. We speculate that ionization of the atmosphere, which was abnormally high during this extreme SEP event, might have led to formation of new particles and/or growth of preexisting ultrafine particles up to the size of CCN. However, a detailed interpretation of the effect is left for subsequent studies. This is the first time high vertical resolution measurements have been used to provide evidence for the probable production of stratospheric CCN from cosmic ray induced ionization.

  8. Novel Approaches to the Sampling of Atmospheric Aerosols and Determination of Chemical Composition

    OpenAIRE

    Parshintsev, Evgeny

    2011-01-01

    The Earth s climate is a highly dynamic and complex system in which atmospheric aerosols have been increasingly recognized to play a key role. Aerosol particles affect the climate through a multitude of processes, directly by absorbing and reflecting radiation and indirectly by changing the properties of clouds. Because of the complexity, quantification of the effects of aerosols continues to be a highly uncertain science. Better understanding of the effects of aerosols requires more informat...

  9. Regional and monthly and clear-sky aerosol direct radiative effect (and forcing derived from the GlobAEROSOL-AATSR satellite aerosol product

    Directory of Open Access Journals (Sweden)

    G. E. Thomas

    2012-07-01

    Full Text Available Using the GlobAEROSOL-AATSR dataset, estimates of the instantaneous, clear-sky, direct aerosol radiative effect and radiative forcing have been produced for the year 2006. Aerosol Robotic Network sun-photometer measurements have been used to characterise the random and systematic error in the GlobAEROSOL product for 22 regions covering the globe. Representative aerosol properties for each region have been derived from the results of a wide range of literature sources and, along with the de-biased GlobAEROSOL AODs, were used to drive an offline version of the Met Office unified model radiation scheme. In addition to the mean AOD, best-estimate run of the radiation scheme, a range of additional calculations were done to propagate uncertainty estimates in the AOD, optical properties, surface albedo and errors due to the temporal and spatial averaging of the AOD fields. This analysis produced monthly, regional estimates of the clear-sky aerosol radiative effect and its uncertainty, which produce annual, global mean values of (−6.7 ± 3.9 W m−2 at the top of atmosphere (TOA and (−12 ± 6 W m−2 at the surface. These results were then used to produce estimates of regional, clear-sky aerosol direct radiative forcing, using modelled pre-industrial AOD fields for 1750 calculated for the AEROCOM PRE experiment. However, as it was not possible to quantify the uncertainty in the pre-industrial aerosol loading, these figures can only be taken as indicative and their uncertainties as lower bounds on the likely errors. Although the uncertainty on aerosol radiative effect presented here is considerably larger than most previous estimates, the explicit inclusion of the major sources of error in the calculations suggest that they are closer to the true constraint on this figure from similar methodologies, and point to the need for more, improved estimates of both global aerosol loading and aerosol optical properties.

  10. Regional and monthly and clear-sky aerosol direct radiative effect (and forcing derived from the GlobAEROSOL-AATSR satellite aerosol product

    Directory of Open Access Journals (Sweden)

    G. E. Thomas

    2013-01-01

    Full Text Available Using the GlobAEROSOL-AATSR dataset, estimates of the instantaneous, clear-sky, direct aerosol radiative effect and radiative forcing have been produced for the year 2006. Aerosol Robotic Network sun-photometer measurements have been used to characterise the random and systematic error in the GlobAEROSOL product for 22 regions covering the globe. Representative aerosol properties for each region were derived from the results of a wide range of literature sources and, along with the de-biased GlobAEROSOL AODs, were used to drive an offline version of the Met Office unified model radiation scheme. In addition to the mean AOD, best-estimate run of the radiation scheme, a range of additional calculations were done to propagate uncertainty estimates in the AOD, optical properties, surface albedo and errors due to the temporal and spatial averaging of the AOD fields. This analysis produced monthly, regional estimates of the clear-sky aerosol radiative effect and its uncertainty, which were combined to produce annual, global mean values of (−6.7 ± 3.9 W m−2 at the top of atmosphere (TOA and (−12 ± 6 W m−2 at the surface. These results were then used to give estimates of regional, clear-sky aerosol direct radiative forcing, using modelled pre-industrial AOD fields for the year 1750 calculated for the AEROCOM PRE experiment. However, as it was not possible to quantify the uncertainty in the pre-industrial aerosol loading, these figures can only be taken as indicative and their uncertainties as lower bounds on the likely errors. Although the uncertainty on aerosol radiative effect presented here is considerably larger than most previous estimates, the explicit inclusion of the major sources of error in the calculations suggest that they are closer to the true constraint on this figure from similar methodologies, and point to the need for more, improved estimates of both global aerosol loading and aerosol optical properties.

  11. Aerosol properties and associated radiative effects over Cairo (Egypt)

    Science.gov (United States)

    El-Metwally, M.; Alfaro, S. C.; Wahab, M. M. Abdel; Favez, O.; Mohamed, Z.; Chatenet, B.

    2011-02-01

    Cairo is one of the largest megacities in the World and the particle load of its atmosphere is known to be particularly important. In this work we aim at assessing the temporal variability of the aerosol's characteristics and the magnitude of its impacts on the transfer of solar radiation. For this we use the level 2 quality assured products obtained by inversion of the instantaneous AERONET sunphotometer measurements performed in Cairo during the Cairo Aerosol CHaracterization Experiment (CACHE), which lasted from the end of October 2004 to the end of March 2006. The analysis of the temporal variation of the aerosol's optical depth (AOD) and spectral dependence suggests that the aerosol is generally a mixture of at least 3 main components differing in composition and size. This is confirmed by the detailed analysis of the monthly-averaged size distributions and associated optical properties (single scattering albedo and asymmetry parameter). The components of the aerosol are found to be 1) a highly absorbing background aerosol produced by daily activities (traffic, industry), 2) an additional, 'pollution' component produced by the burning of agricultural wastes in the Nile delta, and 3) a coarse desert dust component. In July, an enhancement of the accumulation mode is observed due to the atmospheric stability favoring its building up and possibly to secondary aerosols being produced by active photochemistry. More generally, the time variability of the aerosol's characteristics is due to the combined effects of meteorological factors and seasonal production processes. Because of the large values of the AOD achieved during the desert dust and biomass burning episodes, the instantaneous aerosol radiative forcing (RF) at both the top (TOA) and bottom (BOA) of the atmosphere is maximal during these events. For instance, during the desert dust storm of April 8, 2005 RF BOA, RF TOA, and the corresponding atmospheric heating rate peaked at - 161.7 W/m 2, - 65.8 W/m 2

  12. Indirect measurement of the magnetocaloric effect using a novel differential scanning calorimeter with magnetic field

    DEFF Research Database (Denmark)

    Jeppesen, Stinus; Linderoth, Søren; Pryds, Nini; Kuhn, Luise Theil; Jensen, Jesper Buch

    2008-01-01

    A simple and high-sensitivity differential scanning calorimeter (DSC) unit operating under magnetic field has been built for indirect determination of the magnetocaloric effect. The principle of the measuring unit in the calorimeter is based on Peltier elements as heat flow sensors. The high...

  13. Effects of Direct and Indirect Instruction on Fostering Decision-Making Competence in Socioscientific Issues

    Science.gov (United States)

    Bottcher, Florian; Meisert, Anke

    2013-01-01

    In this study the effects of different learning environments on the promotion of decision-making competence for the socioscientific issue of genetically modified crops is investigated. The comparison focuses on direct vs. indirect instructions. Therefore on the one hand a sophisticated decision-making strategy was presented to the directly…

  14. Living in a noisy world: indirect effects of noise on animal communication

    NARCIS (Netherlands)

    Naguib, M.

    2013-01-01

    Noise is a ubiquitous feature in natural as well as in urban habitats. The presence of noise can have multiple direct and indirect effects on communication. Noise can directly mask signals leading to reduced detection and recognition. Noise also affects internal physiological processes which can inf

  15. Effects of different surface treatments on bond strength of an indirect composite to bovine dentin

    Directory of Open Access Journals (Sweden)

    Laiza Tatiana Poskus

    2015-01-01

    Conclusions: Sandblasting was a safe surface treatment for the indirect composite, increasing the BS values. Hydrofluoric acid applied after sandblasting damaged the BS values and should not be recommended while ethanol and H2O2, when applied after sandblasting, were effective in increasing BS values.

  16. Neutrino oscillation effect on the indirect signal of neutralino dark matter from the Earth core

    CERN Document Server

    Fornengo, N

    1999-01-01

    We investigate the effect induced by neutrino oscillation on the dark matter indirect detection signal which consists in a muon neutrino flux produced by neutralino annihilation in the Earth core. We consider the neutrino oscillation parameters relevant to the atmosferic neutrino deficit, both in the nu_mu -> nu_tau and nu_mu -> nu_s cases.

  17. Changes in the North Sea fish community: evidence of indirect effects of fishing?

    NARCIS (Netherlands)

    Daan, N.; Gislason, H.; Pope, J.G.; Rice, J.C.

    2005-01-01

    We investigate changes in the North Sea fish community with particular reference to possible indirect effects of fishing, mediated through the ecosystem. In the past, long-term changes in the slope of size spectra of research vessel catches have been related to changes in fishing effort, but such ch

  18. Direct and Indirect Effects of Parental Influence upon Adolescent Alcohol Use: A Structural Equation Modeling Analysis

    Science.gov (United States)

    Kim, Young-Mi; Neff, James Alan

    2010-01-01

    A model incorporating the direct and indirect effects of parental monitoring on adolescent alcohol use was evaluated by applying structural equation modeling (SEM) techniques to data on 4,765 tenth-graders in the 2001 Monitoring the Future Study. Analyses indicated good fit of hypothesized measurement and structural models. Analyses supported both…

  19. Genetic and non-genetic indirect effects for bite mark traits in group housed mink

    DEFF Research Database (Denmark)

    Alemu, Setegn Worku; Berg, Peer; Janss, Luc;

    Social interactions among individuals are abundant, both in wild and domestic populations. With social interactions, genes of an individual may affect the trait values of other individuals, a phenomenon known as Indirect Genetic Effects (IGEs). IGEs can be estimated using linear mixed models. Here...... welfare in mink, and there are good prospects for genetic improvement....

  20. Components of the indirect effect in vaccine trials: identification of contagion and infectiousness effects.

    Science.gov (United States)

    Vanderweele, Tyler J; Tchetgen Tchetgen, Eric J; Halloran, M Elizabeth

    2012-09-01

    Vaccination of one person may prevent the infection of another either because the vaccine prevents the first from being infected and from infecting the second, or because, even if the first person is infected, the vaccine may render the infection less infectious. We might refer to the first of these mechanisms as a contagion effect and the second as an infectiousness effect. In the simple setting of a randomized vaccine trial with households of size two, we use counterfactual theory under interference to provide formal definitions of a contagion effect and an unconditional infectiousness effect. Using ideas analogous to mediation analysis, we show that the indirect effect (the effect of one person's vaccine on another's outcome) can be decomposed into a contagion effect and an unconditional infectiousness effect on the risk difference, risk ratio, odds ratio, and vaccine efficacy scales. We provide identification assumptions for such contagion and unconditional infectiousness effects and describe a simple statistical technique to estimate these effects when they are identified. We also give a sensitivity analysis technique to assess how inferences would change under violations of the identification assumptions. The concepts and results of this paper are illustrated with hypothetical vaccine trial data. PMID:22828661

  1. Global Aerosol Direct Radiative Effect from CALIOP and C3M

    OpenAIRE

    Winker Dave; Kato Seiji; Tackett Jason

    2016-01-01

    Aerosols are responsible for the largest uncertainties in current estimates of climate orcing. These uncertainties are due in part to the limited abilities of passive sensors to retrieve aerosols in cloudy skies. We use a dataset which merges CALIOP observations together with other A-train observations to estimate aerosol radiative effects in cloudy skies as well as in cloud-free skies. The results can be used to quantify the reduction of aerosol radiative effects in cloudy skies relative to ...

  2. Meteorological and aerosol effects on marine cloud microphysical properties

    Science.gov (United States)

    Sanchez, K. J.; Russell, L. M.; Modini, R. L.; Frossard, A. A.; Ahlm, L.; Corrigan, C. E.; Roberts, G. C.; Hawkins, L. N.; Schroder, J. C.; Bertram, A. K.; Zhao, R.; Lee, A. K. Y.; Lin, J. J.; Nenes, A.; Wang, Z.; Wonaschütz, A.; Sorooshian, A.; Noone, K. J.; Jonsson, H.; Toom, D.; Macdonald, A. M.; Leaitch, W. R.; Seinfeld, J. H.

    2016-04-01

    Meteorology and microphysics affect cloud formation, cloud droplet distributions, and shortwave reflectance. The Eastern Pacific Emitted Aerosol Cloud Experiment and the Stratocumulus Observations of Los-Angeles Emissions Derived Aerosol-Droplets studies provided measurements in six case studies of cloud thermodynamic properties, initial particle number distribution and composition, and cloud drop distribution. In this study, we use simulations from a chemical and microphysical aerosol-cloud parcel (ACP) model with explicit kinetic drop activation to reproduce observed cloud droplet distributions of the case studies. Four cases had subadiabatic lapse rates, resulting in fewer activated droplets, lower liquid water content, and higher cloud base height than an adiabatic lapse rate. A weighted ensemble of simulations that reflect measured variation in updraft velocity and cloud base height was used to reproduce observed droplet distributions. Simulations show that organic hygroscopicity in internally mixed cases causes small effects on cloud reflectivity (CR) (aerosol concentrations near the critical diameter (namely, polluted cases with a modal peak near 0.1 µm). Differences in simulated droplet spectral widths (k) caused larger differences in CR than organic hygroscopicity in cases with organic mass fractions of 60% or less for the cases shown. Finally, simulations from a numerical parameterization of cloud droplet activation suitable for general circulation models compared well with the ACP model, except under high organic mass fraction.

  3. Effects of Ocean Ecosystem on Marine Aerosol-Cloud Interaction

    Directory of Open Access Journals (Sweden)

    Nicholas Meskhidze

    2010-01-01

    Full Text Available Using satellite data for the surface ocean, aerosol optical depth (AOD, and cloud microphysical parameters, we show that statistically significant positive correlations exist between ocean ecosystem productivity, the abundance of submicron aerosols, and cloud microphysical properties over different parts of the remote oceans. The correlation coefficient for remotely sensed surface chlorophyll a concentration ([Chl-a] and liquid cloud effective radii over productive areas of the oceans varies between −0.2 and −0.6. Special attention is given to identifying (and addressing problems from correlation analysis used in the previous studies that can lead to erroneous conclusions. A new approach (using the difference between retrieved AOD and predicted sea salt aerosol optical depth, AODdiff is developed to explore causal links between ocean physical and biological systems and the abundance of cloud condensation nuclei (CCN in the remote marine atmosphere. We have found that over multiple time periods, 550 nm AODdiff (sensitive to accumulation mode aerosol, which is the prime contributor to CCN correlates well with [Chl-a] over the productive waters of the Southern Ocean. Since [Chl-a] can be used as a proxy of ocean biological productivity, our analysis demonstrates the role of ocean ecology in contributing CCN, thus shaping the microphysical properties of low-level marine clouds.

  4. Turning lights into flights: Estimating direct and indirect rebound effects for UK households

    International Nuclear Information System (INIS)

    Energy efficiency improvements by households lead to rebound effects that offset the potential energy and emissions savings. Direct rebound effects result from increased demand for cheaper energy services, while indirect rebound effects result from increased demand for other goods and services that also require energy to provide. Research to date has focused upon the former, but both are important for climate change. This study estimates the combined direct and indirect rebound effects from seven measures that improve the energy efficiency of UK dwellings. The methodology is based upon estimates of the income elasticity and greenhouse gas (GHG) intensity of 16 categories of household goods and services, and allows for the embodied emissions of the energy efficiency measures themselves, as well as the capital cost of the measures. Rebound effects are measured in GHG terms and relate to the adoption of these measures by an average UK household. The study finds that the rebound effects from these measures are typically in the range 5–15% and arise mostly from indirect effects. This is largely because expenditure on gas and electricity is more GHG-intensive than expenditure on other goods and services. However, the anticipated shift towards a low carbon electricity system in the UK may lead to much larger rebound effects. - Highlights: ► We estimate the direct and indirect rebound effects from energy efficiency improvements by UK households. ► We allow for the capital cost of the improvement, together with the emissions embodied in the relevant equipment. ► We find rebound effects to be relatively modest, in the range 5–15%. ► The anticipated shift towards a low carbon electricity system will lead to larger rebound effects

  5. Contribution of natural and anthropogenic aerosols to optical properties and radiative effects over an urban location

    International Nuclear Information System (INIS)

    A method to determine the contribution of natural and anthropogenic aerosol species to aerosol radiative forcing using surface-based, columnar and vertical profile measurements, optical properties and radiative transfer models is outlined. Aerosol optical properties and radiative fluxes measured during 2008 over Ahmedabad, an urban city located in western India are utilized. Mid-visible aerosol optical depth (AOD) does not show a strong seasonal variation, while α, the Ångström exponent, exhibits significant seasonal variation. α is higher during winter and post-monsoon, when fine mode aerosols are dominant, while α is lower during pre-monsoon and monsoon, when coarse mode aerosols are abundant. The contribution of mineral dust to the total aerosol mass is higher than 55% as the study location is in a semi-arid region. Natural aerosols (mineral dust and sea salt) dominate the aerosol mass concentration, while anthropogenic aerosols (water soluble aerosols and black carbon) dominate the aerosol optical depth. The percentage contribution of black carbon to the net atmospheric forcing is larger than 65% throughout the year, corroborating that black carbon aerosol is a strong contributor to global warming on regional scales. Black carbon aerosols contribute 50% or more to the aerosol radiative forcing at the surface, thus, significantly contributing to solar dimming. The large atmospheric warming and the surface forcing due to black carbon aerosols can influence the hydrological cycle. Results emphasize that aerosol radiative forcing is governed more by aerosol optical properties (aerosol optical depth and single scattering albedo) rather than their mass, and there exists no linear relation between mass, optical depth and radiative effects of different aerosol species. These results and the relationship can be used to delineate the anthropogenic influence of aerosols from their natural counterpart, because anthropogenic aerosols in the fine mode (lower mass) give

  6. Light absorption by secondary organic aerosol from α-pinene: Effects of oxidants, seed aerosol acidity, and relative humidity

    Energy Technology Data Exchange (ETDEWEB)

    Song, Chen [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Now at R. J. Reynolds Tobacco Company, Winston-Salem North Carolina USA; Gyawali, Madhu [Department of Physics, University of Nevada Reno, Nevada System of Higher Education, Reno Nevada USA; Now at Desert Research Institute, Nevada System of Higher Education, Reno Nevada USA; Zaveri, Rahul A. [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Shilling, John E. [Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Arnott, W. Patrick [Department of Physics, University of Nevada Reno, Nevada System of Higher Education, Reno Nevada USA

    2013-10-25

    It is well known that light absorption from dust and black carbon aerosols has a warming effect on climate while light scattering from sulfate, nitrate, and sea salt aerosols has a cooling effect. However, there are large uncertainties associated with light absorption and scattering by different types of organic aerosols, especially in the near-UV and UV spectral regions. In this paper, we present the results from a systematic laboratory study focused on measuring light absorption by secondary organic aerosols (SOAs) generated from dark α-pinene + O3 and α-pinene + NOx + O3 systems in the presence of neutral and acidic sulfate seed aerosols. Light absorption was monitored using photoacoustic spectrometers at four different wavelengths: 355, 405, 532, and 870 nm. Significant light absorption at 355 and 405 nm was observed for the SOA formed from α-pinene + O3 + NO3 system only in the presence of highly acidic sulfate seed aerosols under dry conditions. In contrast, no absorption was observed when the relative humidity was elevated to greater than 27% or in the presence of neutral sulfate seed aerosols. Organic nitrates in the SOA formed in the presence of neutral sulfate seed aerosols were found to be nonabsorbing, while the light-absorbing compounds are speculated to be aldol condensation oligomers with nitroxy organosulfate groups that are formed in highly acidic sulfate aerosols. Finally and overall, these results suggest that dark α-pinene + O3 and α-pinene + NOx + O3 systems do not form light-absorbing SOA under typical atmospheric conditions.

  7. Light absorption by secondary organic aerosol from α-pinene: Effects of oxidants, seed aerosol acidity, and relative humidity

    Science.gov (United States)

    Song, Chen; Gyawali, Madhu; Zaveri, Rahul A.; Shilling, John E.; Arnott, W. Patrick

    2013-10-01

    is well known that light absorption from dust and black carbon aerosols has a warming effect on climate while light scattering from sulfate, nitrate, and sea salt aerosols has a cooling effect. However, there are large uncertainties associated with light absorption and scattering by different types of organic aerosols, especially in the near-UV and UV spectral regions. In this paper, we present the results from a systematic laboratory study focused on measuring light absorption by secondary organic aerosols (SOAs) generated from dark α-pinene + O3 and α-pinene + NOx + O3 systems in the presence of neutral and acidic sulfate seed aerosols. Light absorption was monitored using photoacoustic spectrometers at four different wavelengths: 355, 405, 532, and 870 nm. Significant light absorption at 355 and 405 nm was observed for the SOA formed from α-pinene + O3 + NO3 system only in the presence of highly acidic sulfate seed aerosols under dry conditions. In contrast, no absorption was observed when the relative humidity was elevated to greater than 27% or in the presence of neutral sulfate seed aerosols. Organic nitrates in the SOA formed in the presence of neutral sulfate seed aerosols were found to be nonabsorbing, while the light-absorbing compounds are speculated to be aldol condensation oligomers with nitroxy organosulfate groups that are formed in highly acidic sulfate aerosols. Overall, these results suggest that dark α-pinene + O3 and α-pinene + NOx + O3 systems do not form light-absorbing SOA under typical atmospheric conditions.

  8. Does primary productivity modulate the indirect effects of large herbivores? A global meta-analysis.

    Science.gov (United States)

    Daskin, Joshua H; Pringle, Robert M

    2016-07-01

    Indirect effects of large mammalian herbivores (LMH), while much less studied than those of apex predators, are increasingly recognized to exert powerful influences on communities and ecosystems. The strength of these effects is spatiotemporally variable, and several sets of authors have suggested that they are governed in part by primary productivity. However, prior theoretical and field studies have generated conflicting results and predictions, underscoring the need for a synthetic global analysis. We conducted a meta-analysis of the direction and magnitude of large mammalian herbivore-initiated indirect interactions using 67 published studies comprising 456 individual responses. We georeferenced 41 of these studies (comprising 253 responses from 33 locations on five continents) to a satellite-derived map of primary productivity. Because predator assemblages might also influence the impact of large herbivores, we conducted a similar analysis using a global map of large carnivore species richness. In general, LMH reduced the abundance of other consumer species and also tended to reduce consumer richness, although the latter effect was only marginally significant. There was a pronounced reduction in the strength of negative (i.e. suppressive, due e.g., to competition) indirect effects of LMH on consumer abundance in more productive ecosystems. In contrast, positive (facilitative) indirect effects were not significantly correlated with productivity, likely because these comprised a more heterogeneous array of mechanisms. We found no effect of carnivore species richness on herbivore-initiated indirect effect strength. Our findings help to resolve the fundamental problem of ecological contingency as it pertains to the strength of an understudied class of multitrophic interactions. Moreover, these results will aid in predicting the indirect effects of anthropogenic wildlife declines and irruptions, and how these effects might be mediated by climatically driven shifts

  9. Aerosol/Cloud Measurements Using Coherent Wind Doppler Lidars

    Science.gov (United States)

    Royer, Philippe; Boquet, Matthieu; Cariou, Jean-Pierre; Sauvage, Laurent; Parmentier, Rémy

    2016-06-01

    The accurate localization and characterization of aerosol and cloud layers is crucial for climate studies (aerosol indirect effect), meteorology (Planetary Boundary Layer PBL height), site monitoring (industrial emissions, mining,…) and natural hazards (thunderstorms, volcanic eruptions). LEOSPHERE has recently developed aerosol/cloud detection and characterization on WINDCUBE long range Coherent Wind Doppler Lidars (CWDL). These new features combine wind and backscatter intensity informations (Carrier-to-Noise Ratio CNR) in order to detect (aerosol/cloud base and top, PBL height) and to characterize atmospheric structures (attenuated backscatter, depolarization ratio). For each aerosol/cloud functionality the method is described, limitations are discussed and examples are given to illustrate the performances.

  10. Linking Mother and Youth Parenting Attitudes: Indirect Effects via Maltreatment, Parent Involvement, and Youth Functioning

    OpenAIRE

    Thompson, Richard; Jones, Deborah J.; Litrownik, Alan J.; English, Diana J.; Kotch, Jonathan B.; Lewis, Terri; DUBOWITZ, HOWARD

    2014-01-01

    Evidence suggests that parenting attitudes are transmitted within families. However, limited research has examined this prospectively. The current prospective study examined direct effects of early maternal attitudes toward parenting (as measured at child age 4 by the Adult-Adolescent Parenting Inventory [AAPI]) on later youth parenting attitudes (as measured by the AAPI at youth age 18). Indirect effects via child maltreatment (physical abuse, sexual abuse, neglect, and emotional maltreatmen...

  11. Protection of electrical and electronic equipment against lightning indirect effects on the Airbus A340 wing

    Science.gov (United States)

    Spiller, Olaf

    1991-01-01

    The provisions applied to the Airbus A340 wing wiring against lightning indirect effects are presented. The construction and installation of the wiring's shielding systems are described, and the analysis and tests performed to determine the effectiveness of the measures taken are discussed. A first evaluation of the results of the theoretical analysis together with the provisional results of tests indicate a sufficient safety margin between required and achieved protection levels.

  12. Direct and Indirect Effects of UV-B Exposure on Litter Decomposition: A Meta-Analysis

    OpenAIRE

    Song, Xinzhang; Peng, Changhui; Jiang, Hong; Zhu, Qiuan; Wang, Weifeng

    2013-01-01

    Ultraviolet-B (UV-B) exposure in the course of litter decomposition may have a direct effect on decomposition rates via changing states of photodegradation or decomposer constitution in litter while UV-B exposure during growth periods may alter chemical compositions and physical properties of plants. Consequently, these changes will indirectly affect subsequent litter decomposition processes in soil. Although studies are available on both the positive and negative effects (including no observ...

  13. Predator crypsis enhances behaviourally mediated indirect effects on plants by altering bumblebee foraging preferences

    OpenAIRE

    Ings, Thomas C.; Chittka, Lars

    2009-01-01

    Predators of pollinators can influence pollination services and plant fitness via both consumptive (reducing pollinator density) and non-consumptive (altering pollinator behaviour) effects. However, a better knowledge of the mechanisms underlying behaviourally mediated indirect effects of predators is necessary to properly understand their role in community dynamics. We used the tripartite relationship between bumblebees, predatory crab spiders and flowers to ask whether behaviourally mediate...

  14. Influence of Size Effects on Concentration of Impurity (Dopant) in Aerosol Nanoparticles Growing in Supersaturated Vapor

    Czech Academy of Sciences Publication Activity Database

    Levdansky, Valerij Vladimirovič; Smolík, Jiří; Ždímal, Vladimír; Moravec, Pavel

    -: Italian Aerosol Society, 2015. ISBN N. [European Aerosol Conference EAC 2015. Milano (IT), 06.09.2015-11.09.2015] R&D Projects: GA ČR(CZ) GBP503/12/G147 Institutional support: RVO:67985858 Keywords : aerosol * nanoparticles * size effects Subject RIV: DN - Health Impact of the Environment Quality

  15. Global Aerosol Direct Radiative Effect from CALIOP and C3M

    Science.gov (United States)

    Winker, Dave; Kato, Seiji; Tackett, Jason

    2016-06-01

    Aerosols are responsible for the largest uncertainties in current estimates of climate orcing. These uncertainties are due in part to the limited abilities of passive sensors to retrieve aerosols in cloudy skies. We use a dataset which merges CALIOP observations together with other A-train observations to estimate aerosol radiative effects in cloudy skies as well as in cloud-free skies. The results can be used to quantify the reduction of aerosol radiative effects in cloudy skies relative to clear skies and to reduce current uncertainties in aerosol radiative effects.

  16. SCAM simuleringer av aerosolers effekt på skydråper : sammenligning med MODIS

    OpenAIRE

    2007-01-01

    Aerosol particles , such as sulfate aerosols, can act as cloud condensation nuclei (CCN). The CCN spectrum and water vapor supply in a cloud determine the cloud droplet number concentration (CDNC) and hence shortwave optical properties of liquid clouds. The capability of aerosols to increase cloud reflectivity and thereby cool the Earths surface is referred to as the indirect effect. The goal of this study is to compare different cases which relate aerosol mass concentration and cloud dr...

  17. Effect of aerosol concentration and absorbing aerosol on the radiation fog life cycle

    Science.gov (United States)

    Maalick, Z.; Kühn, T.; Korhonen, H.; Kokkola, H.; Laaksonen, A.; Romakkaniemi, S.

    2016-05-01

    Analogous to cloud formation, the formation and life cycle of fogs is largely influenced by aerosol particles. The objective of this work is to analyze how changes in aerosol properties affect the fog life cycle, with special emphasis on how droplet concentrations change with cloud condensation nuclei (CCN) concentrations and on the effect that absorbing black carbon (BC) particles have on fog dissipation. For our simulation case study, we chose a typical fall time radiation fog at mid-latitudes (45° north) in fairly highly polluted conditions. Our results show that CCN concentrations have a strong influence on the fog lifetime. This is because the immediate effect of CCN on cloud droplet number concentrations (CDNC) is enhanced through two positive feedback loops: (1) Higher CDNC leads to more radiative cooling at the fog top, which leads to even stronger activation and (2) if CDNC is higher, the average droplet size is smaller, which slows down droplet removal through sedimentation. The effect that radiation fogs have on solar surface irradiation is large - the daily mean can change by 50% if CCN concentrations are doubled or halved (considering a reference CCN mixing ratio of 800 #/mg). With the same changes in CCN, the total fog lifetime increases 160 min or decreases 65 min, respectively. Although BC has a noticeable effect on fog height and dissipation time, its relative effect compared to CCN is small, even if BC concentrations are high. The fog formation is very sensitive to initial meteorological conditions which may be altered considerably if fog was present the previous day. This effect was neglected here, and future simulations, which span several days, may thus be a valuable extension of this study.

  18. Influence of Size Effect on Evaporation of Aerosol Nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Levdansky, V.V.; Smolík, Jiří; Ždímal, Vladimír

    Praha : Czech Aerosol Society , 2013 - (Zíková, N.), s. 23-24 ISBN 978-80-86186-52-8. [Výroční konference České aerosolové společnosti /14./. Nový Smokovec, High Tatras (SK), 23.10.2013-25.10.2013] R&D Projects: GA AV ČR IAA200760905 Institutional support: RVO:67985858 Keywords : nanoparticles * size effect * evaporation Subject RIV: CF - Physical ; Theoretical Chemistry

  19. ‘Fungicide application method’ and the interpretation of mycorrhizal fungus insect indirect effects

    Science.gov (United States)

    Laird, Robert A.; Addicott, John F.

    2008-09-01

    Mycorrhizal fungi, by altering their host plant's physiology, can have indirect effects on insect herbivores. The 'fungicide application method' is a common approach used to investigate the indirect effects of mycorrhizal fungi on insects. This approach works by using initially mycorrhizal plants, and then generating a subset of these plants that are free of mycorrhizal fungi by applying fungicide to their roots. When insect feeding-bioassays are conducted using the resulting mycorrhizal and non-mycorrhizal plants, differences in insect performance are typically attributed to differences in mycorrhizal colonization per se, rather than the application of the fungicide. Thus, the fungicide application method relies on the assumption that there is no direct toxicity of the fungicide on the focal insect species, and no indirect effects on the focal insect resulting from effects of the fungicide on the host plant or on non-target soil micro-organisms. We tested this critical assumption by feeding Zygogramma exclamationis (Chrysomelidae) larvae on non-mycorrhizal Helianthus annuus (Asteraceae) plants whose roots were treated with a solution of the fungicide benomyl or with a distilled water control. Larvae fed on benomyl-treated plants had reduced survival, lower relative growth rate, and lower food conversion efficiency, compared to larvae fed on control plants. Hence, fungicides applied to roots can affect herbivorous insect performance even in the absence of the possibility of mycorrhizal fungi-mediated effects. We recommend caution when using fungicide application and suggest that selective inoculation is a preferable method of generating mycorrhizal and non-mycorrhizal plants when studying mycorrhizal fungi-insect indirect effects.

  20. Direct and indirect effects of UV-B exposure on litter decomposition: a meta-analysis.

    Directory of Open Access Journals (Sweden)

    Xinzhang Song

    Full Text Available Ultraviolet-B (UV-B exposure in the course of litter decomposition may have a direct effect on decomposition rates via changing states of photodegradation or decomposer constitution in litter while UV-B exposure during growth periods may alter chemical compositions and physical properties of plants. Consequently, these changes will indirectly affect subsequent litter decomposition processes in soil. Although studies are available on both the positive and negative effects (including no observable effects of UV-B exposure on litter decomposition, a comprehensive analysis leading to an adequate understanding remains unresolved. Using data from 93 studies across six biomes, this introductory meta-analysis found that elevated UV-B directly increased litter decomposition rates by 7% and indirectly by 12% while attenuated UV-B directly decreased litter decomposition rates by 23% and indirectly increased litter decomposition rates by 7%. However, neither positive nor negative effects were statistically significant. Woody plant litter decomposition seemed more sensitive to UV-B than herbaceous plant litter except under conditions of indirect effects of elevated UV-B. Furthermore, levels of UV-B intensity significantly affected litter decomposition response to UV-B (P<0.05. UV-B effects on litter decomposition were to a large degree compounded by climatic factors (e.g., MAP and MAT (P<0.05 and litter chemistry (e.g., lignin content (P<0.01. Results suggest these factors likely have a bearing on masking the important role of UV-B on litter decomposition. No significant differences in UV-B effects on litter decomposition were found between study types (field experiment vs. laboratory incubation, litter forms (leaf vs. needle, and decay duration. Indirect effects of elevated UV-B on litter decomposition significantly increased with decay duration (P<0.001. Additionally, relatively small changes in UV-B exposure intensity (30% had significant direct effects

  1. Bald eagles and sea otters in the Aleutian Archipelago: indirect effects of trophic cascades.

    Science.gov (United States)

    Anthony, R.G.; Estes, J.A.; Ricca, M.A.; Miles, A.K.; Forsman, E.D.

    2008-01-01

    Because sea otters (Enhydra lutris) exert a wide array of direct and indirect effects on coastal marine ecosystems throughout their geographic range, we investigated the potential influence of sea otters on the ecology of Bald Eagles (Haliaeetus leucocephalus) in the Aleutian Islands, Alaska, USA. We studied the diets, productivity, and density of breeding Bald Eagles on four islands during 1993-1994 and 2000-2002, when sea otters were abundant and scarce, respectively. Bald Eagles depend on nearshore marine communities for most of their prey in this ecosystem, so we predicted that the recent decline in otter populations would have an indirect negative effect on diets and demography of Bald Eagles. Contrary to our predictions, we found no effects on density of breeding pairs on four islands from 1993-1994 to 2000-2002. In contrast, diets and diet diversity of Bald Eagles changed considerably between the two time periods, likely reflecting a change in prey availability resulting from the increase and subsequent decline in sea otter populations. The frequency of sea otter pups, rock greenling (Hexagammus lagocephalus), and smooth lumpsuckers (Aptocyclus ventricosus) in the eagle's diet declined with corresponding increases in Rock Ptarmigan (Lagopus mutus), Glaucous-winged Gulls (Larus glaucescens), Atka mackerel (Pleurogrammus monopterygius), and various species of seabirds during the period of the recent otter population decline. Breeding success and productivity of Bald Eagles also increased during this time period, which may be due to the higher nutritional quality of avian prey consumed in later years. Our results provide further evidence of the wide-ranging indirect effects of sea otter predation on nearshore marine communities and another apex predator, the Bald Eagle. Although the indirect effects of sea otters are widely known, this example is unique because the food-web pathway transcended five species and several trophic levels in linking one apex predator

  2. Direct and indirect effects of ants on a forest-floor food web.

    Science.gov (United States)

    Moya-Laraño, Jordi; Wise, David H

    2007-06-01

    Interactions among predators that prey on each other and are potential competitors for shared prey (intraguild [IG] predators) are widespread in terrestrial ecosystems and have the potential to strongly influence the dynamics of terrestrial food webs. Ants and spiders are abundant and ubiquitous terrestrial IG predators, yet the strength and consequences of interactions between them are largely unknown. In the leaf-litter food web of a deciduous forest in Kentucky (USA), we tested the direct and indirect effects of ants on spiders and a category of shared prey (Collembola) by experimentally subsidizing ants in open plots in two field experiments. In the first experiment, ant activity was increased, and the density of ants in the litter was doubled, by placing carbohydrate and protein baits in the center of each plot. Gnaphosa spiders were almost twice as abundant and Schizocosa spiders were half as abundant in baited plots relative to controls. There were more tomocerid Collembola in baited plots, suggesting possible indirect effects on Collembola caused by ant-spider interactions. The second experiment, in which screening of two mesh sizes selectively excluded large and small worker ants from a sugar bait, revealed that the large ants, primarily Camponotus, could alone induce similar effects on spiders. Gnaphosa biomass density was almost twice as high in the plots where large ants were more active, whereas Schizocosa biomass density was reduced by half in these plots. Although tomocerid densities did not differ between treatments, tomocerid numbers were negatively correlated with the activity of Formica, another large ant species. Path analysis failed to support the hypothesis that the ant Camponotus indirectly affected tomocerid Collembola through effects on densities of spiders. However, path analysis also revealed other indirect effects of Camponotus affecting tomocerids. These results illustrate the complexity of interactions between and within two major IG

  3. Modeling the indirect effect of Wolbachia on the infection dynamics of horizontally transmitted viruses.

    Science.gov (United States)

    Strauß, Jakob F; Telschow, Arndt

    2015-01-01

    Intracellular bacteria of the genus Wolbachia are widely distributed in arthropods. There is growing empirical evidence that Wolbachia directly interacts with viruses and other parasites inside the arthropod host, sometimes resulting in low or no pathogen replication. Previous theoretical studies showed that this direct effect of Wolbachia can result in a reduced virus prevalence (within the population), suggesting that Wolbachia could be used in the biological control of vector-borne diseases (e.g., dengue fever). However, Wolbachia might also indirectly affect virus dynamics because Wolbachia-induced reproductive phenotypes (cytoplasmic incompatibility or male killing) increase the larval mortality of hosts and thus alter the age structure of populations. We investigated this indirect effect using mathematical models with overlapping generations, and found the results to depend strongly on the host's life history. In general, the indirect effect can result in two different outcomes: (1) reduced virus prevalence and virus invasion ability, and (2) increased virus prevalence and virus invasion ability. The former occurs for host species with larval competition and undercompensation, the latter for hosts with either adult competition or larval competition and overcompensation. These findings suggest that the effect of Wolbachia on a specific virus is sensitive to the host's life history. We discuss the results with respect to biocontrol programs using Wolbachia. PMID:25972858

  4. Modeling the indirect effect of Wolbachia on the infection dynamics of horizontally transmitted viruses.

    Directory of Open Access Journals (Sweden)

    Jakob Friedrich Strauß

    2015-04-01

    Full Text Available Intracellular bacteria of the genus Wolbachia are widely distributed in arthropods. There is growing empirical evidence that Wolbachia directly interacts with viruses and other parasites inside the arthropod host, sometimes resulting in low or no pathogen replication. Previous theoretical studies showed that this direct effect of Wolbachia can result in a reduced virus prevalence (within the population, suggesting that Wolbachia could be used in the biological control of vector-borne diseases (e.g., dengue fever. However, Wolbachia might also indirectly affect virus dynamics because Wolbachia-induced reproductive phenotypes (cytoplasmic incompatibility or male killing increase the larval mortality of hosts and thus alter the age structure of populations. We investigated this indirect effect using mathematical models with overlapping generations, and found the results to depend strongly on the host's life history. In general, the indirect effect can result in two different outcomes: (1 reduced virus prevalence and virus invasion ability, and (2 increased virus prevalence and virus invasion ability. The former occurs for host species with larval competition and undercompensation, the latter for hosts with either adult competition or larval competition and overcompensation. These findings suggest that the effect of Wolbachia on a specific virus is sensitive to the host's life history. We discuss the results with respect to biocontrol programs using Wolbachia.

  5. Direct and indirect genetic effects of sex-specific mitonuclear epistasis on reproductive ageing

    DEFF Research Database (Denmark)

    Immonen, Elina; Collet, Marie; Goenaga, Julieta;

    2016-01-01

    Mitochondria are involved in ageing and their function requires coordinated action of both mitochondrial and nuclear genes. Epistasis between the two genomes can influence lifespan but whether this also holds for reproductive senescence is unclear. Maternal inheritance of mitochondria predicts sex...... to slower senescence relative to novel mitonuclear combinations. We found no evidence for mitonuclear coadaptation in males. Mitonuclear epistasis not only affected age-specific ejaculate weight, but also influenced male age-dependent indirect effects on traits expressed by their female partners...... beetle Callosobruchus maculatus, using introgression lines harbouring distinct mitonuclear genotypes. Our results reveal both direct and indirect sex-specific effects of mitonuclear epistasis on reproductive ageing. Females harbouring coadapted mitonuclear genotypes showed higher lifetime fecundity due...

  6. Investigation of Multi-decadal Trends in Aerosol Direct Radiative Effects over North America using a Coupled Meteorology-Chemistry Model

    Science.gov (United States)

    Mathur, R.; Pleim, J.; Wong, D.; Wei, C.; Xing, J.; Gan, M.; Yu, S.; Binkowski, F.

    2012-12-01

    -wave. New algorithms for the calculation of aerosol optical properties and radiation have been developed by considering both computational efficiency and more realistic aerosol states. Additionally, treatment of aerosol indirect effects on clouds has also recently been implemented. Analysis of measurements of aerosol composition, radiation, and associated variables, over the past two decades will be presented which indicate significant reductions in the tropospheric aerosol burden as well as an increase in down-welling shortwave radiation at numerous sites across the U.S. Initial applications of the coupled WRF-CMAQ model for time-periods pre and post the implementation of Title IV of the CAA will be discussed and comparisons with measurements to assess the model's ability to capture trends in aerosol burden, composition, and direct aerosol effects on surface shortwave radiation will be presented.

  7. Effect of mineral dust aerosol aspect ratio on polarized reflectance

    International Nuclear Information System (INIS)

    The effects of dust particle aspect ratios on single- and multiple-scattering processes are studied using the spheroidal model in order to obtain a better understanding of the radiance and polarization signals at the top of the atmosphere (TOA) under various dust-aerosol-loading conditions. Specifically, the impact of the particle aspect ratio on the polarization state of the TOA radiation field is demonstrated by comparing the normalized polarized radiances observed by the POLDER (POLarization and Directionality of the Earth's Reflectances) instrument on board the PARASOL (Polarisation et Anisotropie des Reflectances au sommet de l'Atmosphère, couples avec un Satellite d'Observation emportant un Lidar) satellite with the corresponding theoretical counterparts. Furthermore, presented are the aspect ratio values inferred from multi-angular polarized radiance measurements of Saharan and Asian dust by the POLDER/PARASOL. - Highlights: • The radiative effect of dust aerosol aspect ratio is investigated. • A computational efficient vector radiative transfer model is developed. • Spaceborne Polarimetric measurements are used to retrieve aerosol properties. • A case study of Saharan dust shows a mean aspect ratio of 2.5. • Asian dust exhibits two aspect ratio values, 2.5 and 1.25

  8. Indirect global warming effects of ozone and stratospheric water vapor induced by surface methane emission

    International Nuclear Information System (INIS)

    Methane has indirect effects on climate due to chemical interactions as well as direct radiative forcing effects as a greenhouse gas. We have calculated the indirect, time-varying tropospheric radiative forcing and GWP of O3 and stratospheric H2O due to an impulse of CH4. This impulse, applied to the lowest layer of the atmosphere, is the increase of the atmospheric mass of CH4 resulting from a 25 percent steady state increase in the current emissions as a function of latitude. The direct CH4 radiative forcing and GWP are also calculated. The LLNL 2-D radiative-chemistry-transport model is used to evaluate the resulting changes in the O3, H2O and CH4 atmospheric profiles as a function of time. A correlated k-distribution radiative transfer model is used to calculate the radiative forcing at the tropopause of the globally-averaged atmosphere profiles. The O3 indirect GWPs vary from ∼27 after a 20 yr integration to ∼4 after 500 years, agreeing with the previous estimates to within about 10 percent. The H2O indirect GWPs vary from ∼2 after a 20 yr integration to ∼0.3 after 500 years, and are in close agreement with other estimates. The CH4 GWPs vary from ∼53 at 20 yrs to ∼7 at 500 yrs. The 20 year CH4 GWP is ∼20% larger than previous estimates of the direct CH4 GWP due to a CH4 response time (∼17 yrs) that is much longer than the overall lifetime (10 yrs). The increased CH4 response time results from changes in the OH abundances caused by the CH4 impulse. The CH4 radiative forcing results are consistent with IPCC values. Estimates are made of latitude effects in the radiative forcing calculations, and UV effects on the O3 radiative forcing calculations (10%)

  9. A review of the direct and indirect effects of neonicotinoids and fipronil on vertebrate wildlife

    OpenAIRE

    Gibbons, David; Morrissey, Christy; Mineau, Pierre

    2014-01-01

    Concerns over the role of pesticides affecting vertebrate wildlife populations have recently focussed on systemic products which exert broad-spectrum toxicity. Given that the neonicotinoids have become the fastest-growing class of insecticides globally, we review here 150 studies of their direct (toxic) and indirect (e.g. food chain) effects on vertebrate wildlife—mammals, birds, fish, amphibians and reptiles. We focus on two neonicotinoids, imidacloprid and clothianidin, and a third insectic...

  10. Conversion degree of indirect resin composites and effect of thermocycling on their physical properties

    OpenAIRE

    Souza, R O

    2010-01-01

    PURPOSE: This study evaluated the degree of conversion (DC) of four indirect resin composites (IRCs) with various compositions processed in different polymerization units and investigated the effect of thermal aging on the flexural strength and Vicker's microhardness. MATERIALS AND METHODS: Specimens were prepared from four IRC materials, namely Gr 1: Resilab (Wilcos); Gr2: Sinfony (3M ESPE); Gr3: VITA VMLC (VITA Zahnfabrik); Gr4: VITA Zeta (VITA Zahnfabrik) using special molds for flexur...

  11. Direct and indirect effects of paliperidone extended-release tablets on negative symptoms of schizophrenia

    OpenAIRE

    Ibrahim Turkoz; Bossie, Cynthia A; Bryan Dirks; Canuso, Carla M

    2008-01-01

    Ibrahim Turkoz, Cynthia A Bossie, Bryan Dirks, Carla M CanusoOrtho-McNeil Janssen Scientific Affairs, LLC, Titusville, NJ, USAAbstract: Direct and indirect effects of the new psychotropic paliperidone extended-release (paliperidone ER) tablets on negative symptom improvement in schizophrenia were investigated using path analysis. A post hoc analysis of pooled data from three 6-week, double-blind, placebo-controlled studies of paliperidone ER in patients experiencing acute exacerbation was con...

  12. Application of PIXE technique to studies on global warming/cooling effect of atmospheric aerosols

    International Nuclear Information System (INIS)

    During the last decade, the importance of global warming has been recognized worldwide. Atmospheric aerosols play an important role in the global warming/cooling effects. The physicochemical properties of aerosol particles are fundamental to understanding such effects. In this study, the PIXE technique was applied to measure the average chemical properties of aerosols. Micro-PIXE was also applied to investigate the mixing state of the individual aerosol particle. The chemical composition data were used to estimate the optical properties of aerosols. The average values of aerosol radiative forcing were -1.53 w/m2 in Kyoto and +3.3 w/m2 in Nagoya, indicating cooling and warming effects respectively. The difference of radiative forcing in the two cities may be caused by the large difference in chemical composition of aerosols

  13. Direct and indirect genetic effects of sex-specific mitonuclear epistasis on reproductive ageing.

    Science.gov (United States)

    Immonen, E; Collet, M; Goenaga, J; Arnqvist, G

    2016-01-01

    Mitochondria are involved in ageing and their function requires coordinated action of both mitochondrial and nuclear genes. Epistasis between the two genomes can influence lifespan but whether this also holds for reproductive senescence is unclear. Maternal inheritance of mitochondria predicts sex differences in the efficacy of selection on mitonuclear genotypes that should result in differences between females and males in mitochondrial genetic effects. Mitonuclear genotype of a focal individual may also indirectly affect trait expression in the mating partner. We tested these predictions in the seed beetle Callosobruchus maculatus, using introgression lines harbouring distinct mitonuclear genotypes. Our results reveal both direct and indirect sex-specific effects of mitonuclear epistasis on reproductive ageing. Females harbouring coadapted mitonuclear genotypes showed higher lifetime fecundity due to slower senescence relative to novel mitonuclear combinations. We found no evidence for mitonuclear coadaptation in males. Mitonuclear epistasis not only affected age-specific ejaculate weight, but also influenced male age-dependent indirect effects on traits expressed by their female partners (fecundity, egg size, longevity). These results demonstrate important consequences of sex-specific mitonuclear epistasis for both mating partners, consistent with a role for mitonuclear genetic constraints upon sex-specific adaptive evolution. PMID:26732015

  14. The impact of aerosol optical depth assimilation on aerosol forecasts and radiative effects during a wild fire event over the United States

    Science.gov (United States)

    Chen, D.; Liu, Z.; Schwartz, C. S.; Lin, H.-C.; Cetola, J. D.; Gu, Y.; Xue, L.

    2014-11-01

    The Gridpoint Statistical Interpolation three-dimensional variational data assimilation (DA) system coupled with the Weather Research and Forecasting/Chemistry (WRF/Chem) model was utilized to improve aerosol forecasts and study aerosol direct and semi-direct radiative feedbacks during a US wild fire event. Assimilation of MODIS total 550 nm aerosol optical depth (AOD) retrievals clearly improved WRF/Chem forecasts of surface PM2.5 and organic carbon (OC) compared to the corresponding forecasts without aerosol data assimilation. The scattering aerosols in the fire downwind region typically cooled layers both above and below the aerosol layer and suppressed convection and clouds, which led to an average of 2% precipitation decrease during the fire week. This study demonstrated that, even with no input of fire emissions, AOD DA improved the aerosol forecasts and allowed a more realistic model simulation of aerosol radiative effects.

  15. Aerosol radiative effects over global arid and semi-arid regions based on MODIS Deep Blue satellite observations

    Science.gov (United States)

    Hatzianastassiou, Nikolaos; Papadimas, Christos D.; Gkikas, Antonis; Matsoukas, Christos; Sayer, Andrew M.; Hsu, N. Christina; Vardavas, Ilias

    2014-05-01

    Aerosols are a key parameter for several atmospheric processes related to weather and climate of our planet. Specifically, the aerosol impact on Earth's climate is exerted and quantified through their radiative effects, which are induced by their direct, indirect and semi-direct interactions with radiation, in particular at short wavelengths (solar). It is acknowledged that the uncertainty of present and future climate assessments is mainly associated with aerosols and that a better understanding of their physico-chemical, optical and radiative effects is needed. The contribution of satellites to this aim is important as a complementary tool to climate and radiative transfer models, as well as to surface measurements, since space observations of aerosol properties offer an extended spatial coverage. However, such satellite based aerosol properties and associated model radiation computations have suffered from unavailability over highly reflecting surfaces, namely polar and desert areas. This is also the case for MODIS which, onboard the Terra and Aqua satellites, has been providing high quality aerosol data since 2000 and 2002, respectively. These data, more specifically the aerosol optical depth (AOD) which is the most important optical property used in radiative and climate models, are considered to be of best quality. In order to address this problem, the MODIS Deep Blue (DB) algorithm has been developed which enables the retrieval of AOD above arid and semi-arid areas of the globe, including the major deserts. In the present study we make use of the FORTH detailed spectral radiative transfer model (RTM) with MODIS DB AOD data, supplemented with single scattering albedo (SSA) and asymmetry parameter (AP) aerosol data from the Global Aerosol DataSet (GADS) to estimate the aerosol DREs over the arid and semi-arid regions of the globe. The RTM is run using surface and atmospheric data from the ISCCP-D2 dataset and the NCEP global reanalysis project and computes the

  16. Direct and indirect effects of climate change on a prairie plant community.

    Directory of Open Access Journals (Sweden)

    Peter B Adler

    Full Text Available BACKGROUND: Climate change directly affects species by altering their physical environment and indirectly affects species by altering interspecific interactions such as predation and competition. Recent studies have shown that the indirect effects of climate change may amplify or counteract the direct effects. However, little is known about the the relative strength of direct and indirect effects or their potential to impact population persistence. METHODOLOGY/PRINCIPAL FINDINGS: We studied the effects of altered precipitation and interspecific interactions on the low-density tiller growth rates and biomass production of three perennial grass species in a Kansas, USA mixed prairie. We transplanted plugs of each species into local neighborhoods of heterospecific competitors and then exposed the plugs to a factorial manipulation of growing season precipitation and neighbor removal. Precipitation treatments had significant direct effects on two of the three species. Interspecific competition also had strong effects, reducing low-density tiller growth rates and aboveground biomass production for all three species. In fact, in the presence of competitors, (log tiller growth rates were close to or below zero for all three species. However, we found no convincing evidence that per capita competitive effects changed with precipitation, as shown by a lack of significant precipitation x competition interactions. CONCLUSIONS/SIGNIFICANCE: We found little evidence that altered precipitation will influence per capita competitive effects. However, based on species' very low growth rates in the presence of competitors in some precipitation treatments, interspecific interactions appear strong enough to affect the balance between population persistence and local extinction. Therefore, ecological forecasting models should include the effect of interspecific interactions on population growth, even if such interaction coefficients are treated as constants.

  17. Global fine-mode aerosol radiative effect, as constrained by comprehensive observations

    Science.gov (United States)

    Chung, Chul E.; Chu, Jung-Eun; Lee, Yunha; van Noije, Twan; Jeoung, Hwayoung; Ha, Kyung-Ja; Marks, Marguerite

    2016-07-01

    Aerosols directly affect the radiative balance of the Earth through the absorption and scattering of solar radiation. Although the contributions of absorption (heating) and scattering (cooling) of sunlight have proved difficult to quantify, the consensus is that anthropogenic aerosols cool the climate, partially offsetting the warming by rising greenhouse gas concentrations. Recent estimates of global direct anthropogenic aerosol radiative forcing (i.e., global radiative forcing due to aerosol-radiation interactions) are -0.35 ± 0.5 W m-2, and these estimates depend heavily on aerosol simulation. Here, we integrate a comprehensive suite of satellite and ground-based observations to constrain total aerosol optical depth (AOD), its fine-mode fraction, the vertical distribution of aerosols and clouds, and the collocation of clouds and overlying aerosols. We find that the direct fine-mode aerosol radiative effect is -0.46 W m-2 (-0.54 to -0.39 W m-2). Fine-mode aerosols include sea salt and dust aerosols, and we find that these natural aerosols result in a very large cooling (-0.44 to -0.26 W m-2) when constrained by observations. When the contribution of these natural aerosols is subtracted from the fine-mode radiative effect, the net becomes -0.11 (-0.28 to +0.05) W m-2. This net arises from total (natural + anthropogenic) carbonaceous, sulfate and nitrate aerosols, which suggests that global direct anthropogenic aerosol radiative forcing is less negative than -0.35 W m-2.

  18. Aerosol Effect on the Mobility of Cloud Droplets

    CERN Document Server

    Koren, Ilan; Dagan, Guy

    2015-01-01

    Cloud droplet mobility is referred here as a measure of the droplets' ability to move with ambient air. We claim that an important part of the aerosol effect on convective clouds is driven by changes in droplet mobility. We show that the mass-averaged droplet terminal velocity ({\\eta}) and spread ({\\sigma}_{\\eta}) serve as direct measures of this effect. Moreover, we develop analytical estimations for {\\eta} and {\\sigma}_{\\eta} to show that changes in the relative dispersion of {\\eta} ({\\epsilon}_{\\eta}={\\sigma}_{\\eta}/{\\eta}) can serve as a sensitive predictor of the onset of droplet-collection processes.

  19. Effect of Aerosol Size and Hygroscopicity on Aerosol Optical Depth in the Southeastern United States

    Science.gov (United States)

    Brock, Charles; Wagner, Nick; Gordon, Timothy

    2016-04-01

    Aerosol optical depth (AOD) is affected by the size, optical characteristics, and hygroscopicity of particles, confounding attempts to link remote sensing observations of AOD to measured or modeled aerosol mass concentrations. In situ airborne observations of aerosol optical, chemical, microphysical and hygroscopic properties were made in the southeastern United States in the daytime in summer 2013. We use these observations to constrain a simple model that is used to test the sensitivity of AOD to the various measured parameters. As expected, the AOD was found to be most sensitive to aerosol mass concentration and to aerosol water content, which is controlled by aerosol hygroscopicity and the ambient relative humidity. However, AOD was also fairly sensitive to the mean particle diameter and the width of the size distribution. These parameters are often prescribed in global models that use simplified modal parameterizations to describe the aerosol, suggesting that the values chosen could substantially bias the calculated relationship between aerosol mass and optical extinction, AOD, and radiative forcing.

  20. Effects of aerosol on evaporation, freezing and precipitation in a multiple cloud system

    Science.gov (United States)

    Lee, Seoung Soo; Kim, Byung-Gon; Yum, Seong Soo; Seo, Kyong-Hwan; Jung, Chang-Hoon; Um, Jun Shik; Li, Zhanqing; Hong, JinKyu; Chang, Ki-Ho; Jeong, Jin-Yim

    2016-04-01

    Aerosol effects on clouds and precipitation account for a large portion of uncertainties in the prediction of the future course of global hydrologic circulations and climate. As a process of a better understanding of interactions between aerosol, clouds and precipitation, simulations are performed for a mixed-phase convective multiple-cloud system over the tropics. Studies on single-cloud systems have shown that aerosol-induced increases in freezing, associated increases in parcel buoyancy and thus the intensity of clouds (or updrafts) are a main mechanism which controls aerosol-cloud-precipitation interactions in convective clouds. However, in the multiple-cloud system that plays much more important roles in global hydrologic circulations and thus climate than single-cloud systems, aerosol effects on condensation play the most important role in aerosol-induced changes in the intensity of clouds and the effects on freezing play a negligible role in those changes. Aerosol-induced enhancement in evaporation intensifies gust fronts and increases the number of subsequently developing clouds, which leads to the substantial increases in condensation and associated intensity of convection. Although aerosol-induced enhancement in freezing takes part in the increases in condensation by inducing stronger convergence around cloud bottom, the increases in condensation are ~one order of magnitude larger than those in freezing. It is found that while aerosol-induced increases in freezing create intermittent extremely heavy precipitation, aerosol-induced increases in evaporation enhance light and medium precipitation in the multiple-cloud system here. This increase in light and medium precipitation makes it possible that cumulative precipitation increases with increasing aerosol concentration, although the increase is small. It is interesting that the altitude of the maximum of the time- and domain-averaged hydrometeor mass densities is quite robust to increases in aerosol

  1. Global cloud condensation nuclei influenced by carbonaceous combustion aerosol

    Science.gov (United States)

    Spracklen, D. V.; Carslaw, K. S.; Pöschl, U.; Rap, A.; Forster, P. M.

    2011-09-01

    Black carbon in carbonaceous combustion aerosol warms the climate by absorbing solar radiation, meaning reductions in black carbon emissions are often perceived as an attractive global warming mitigation option. However, carbonaceous combustion aerosol can also act as cloud condensation nuclei (CCN) so they also cool the climate by increasing cloud albedo. The net radiative effect of carbonaceous combustion aerosol is uncertain because their contribution to CCN has not been evaluated on the global scale. By combining extensive observations of CCN concentrations with the GLOMAP global aerosol model, we find that the model is biased low (normalised mean bias = -77 %) unless carbonaceous combustion aerosol act as CCN. We show that carbonaceous combustion aerosol accounts for more than half (52-64 %) of global CCN with the range due to uncertainty in the emitted size distribution of carbonaceous combustion particles. The model predicts that wildfire and pollution (fossil fuel and biofuel) carbonaceous combustion aerosol causes a global mean cloud albedo aerosol indirect effect of -0.34 W m-2, with stronger cooling if we assume smaller particle emission size. We calculate that carbonaceous combustion aerosol from pollution sources cause a global mean aerosol indirect effect of -0.23 W m-2. The small size of carbonaceous combustion particles from fossil fuel sources means that whilst pollution sources account for only one-third of the emitted mass they cause two-thirds of the cloud albedo aerosol indirect effect that is due to carbonaceous combustion aerosol. This cooling effect must be accounted for, along with other cloud effects not studied here, to ensure that black carbon emissions controls that reduce the high number concentrations of fossil fuel particles have the desired net effect on climate.

  2. Microphysical and radiative effects of aerosols on warm clouds during the Amazon biomass burning season as observed by MODIS: impacts of water vapor and land cover

    Directory of Open Access Journals (Sweden)

    J. E. Ten Hoeve

    2011-04-01

    Full Text Available Aerosol, cloud, water vapor, and temperature profile data from the Moderate Resolution Imaging Spectroradiometer (MODIS are utilized to examine the impact of aerosols on clouds during the Amazonian biomass burning season in Rondônia, Brazil. It is found that increasing background column water vapor (CWV throughout this transition season between the Amazon dry and wet seasons likely exerts a strong effect on cloud properties. As a result, proper analysis of aerosol-cloud relationships requires that data be stratified by CWV to account better for the influence of background meteorological variation. Many previous studies of aerosol-cloud interactions over Amazonia have ignored the systematic changes to meteorological factors during the transition season, leading to possible misinterpretation of their results. Cloud fraction (CF is shown to increase or remain constant with aerosol optical depth (AOD, depending on the value of CWV, whereas the relationship between cloud optical depth (COD and AOD is quite different. COD increases with AOD until AOD ~ 0.3, which is assumed to be due to the first indirect (microphysical effect. At higher values of AOD, COD is found to decrease with increasing AOD, which may be due to: (1 the inhibition of cloud development by absorbing aerosols (radiative effect/semi-direct effect and/or (2 a possible retrieval artifact in which the measured reflectance in the visible is less than expected from a cloud top either from the darkening of clouds through the addition of carbonaceous biomass burning aerosols within or above clouds or subpixel dark surface contamination in the measured cloud reflectance. If (1 is a contributing mechanism, as we suspect, then an empirically-derived increasing function between cloud drop number and aerosol concentration, assumed in a majority of global climate models, is inaccurate since these models do not include treatment of aerosol absorption in and around clouds. The relationship between

  3. Combined effects of organic aerosol loading and fog processing on organic aerosols oxidation and composition

    Science.gov (United States)

    Chakraborty, Abhishek; Tripathi, Sachchida; Gupta, Tarun

    2016-04-01

    Fog is a natural meteorological phenomenon that occurs throughout the world, it contains substantial quantity of liquid water and generally seen as a natural cleansing agent but it also has the potential to form highly oxidized secondary organic aerosols (SOA) via aqueous processing of ambient aerosols. On the other hand higher organic aerosols (OA) loading tend to decrease the overall oxidation level (O/C) of the particle phase organics, due to enhanced partitioning of less oxidized organics from gas to particle phase. However, combined impact of these two parameters; aqueous oxidation and OA loading, on the overall oxidation ratio (O/C) of ambient OA has never been studied. To assess this, real time ambient sampling using HR-ToF-AMS was carried out at Kanpur, India from 15 December 2014 - 10 February 2015. In first 3 weeks of this campaign, very high OA loading is (134 ± 42 μg/m3) observed (termed as high loading or HL period) while loading is substantially reduced from 2nd January, 2016 (56 ± 20 μg/m3, termed as low loading or LL period) . However, both the loading period was affected by several fog episodes (10 in HL and 7 in LL), thus providing the opportunity of studying the combined effects of fog and OA loading on OA oxidation. It is found that O/C ratio is very strongly anti-correlated with OA loading in both the loading period, however, slope of this ant-correlation is much steep during HL period than in LL period. Source apportionment of OA revealed that there is drastic change in the types of OA from HL to LL period, clearly indicating difference in OA composition from HL to LL period. During foggy night continuous oxidation of OA is observed from early evening to early morning with 15-20% enhancement in O/C ratio, while the same is absent during non-foggy period, clearly indicating the efficient fog processing of ambient OA. It is also found that night time fog aqueous oxidation can be as effective as daytime photo chemistry in oxidation of OA. Fog

  4. Effects of tropospheric aerosols on radiative flux calculations at UV and visible wavelengths

    International Nuclear Information System (INIS)

    The surface fluxes in the wavelength range 175 to 735nm have been calculated for an atmosphere which contains a uniformly mixed aerosol layer of thickness 1km at the earth's surface. Two different aerosol types were considered, a rural aerosol, and an urban aerosol. The visibility range for the aerosol layers was 95 to 15 km. Surface flux ratios (15km/95km) were in agreement with previously published results for the rural aerosol layer to within about 2%. The surface flux ratios vary from 7 to 14% for the rural aerosol layer and from 13 to 23% for the urban aerosol layer over the wavelength range. A tropospheric radiative forcing of about 1.3% of the total tropospheric flux was determined for the 95km to 15km visibility change in the rural aerosol layer, indicating the potential of tropospheric feedback effects on the surface flux changes. This effect was found to be negligible for the urban aerosol layer. Stratospheric layer heating rate changes due to visibility changes in either the rural or urban aerosol layer were found to be negligible

  5. Impact of aerosol vertical distribution on aerosol direct radiative effect and heating rate in the Mediterranean region

    Science.gov (United States)

    Pappas, Vasileios; Hatzianastassiou, Nikolaos; Matsoukas, Christos; Koras Carracca, Mario; Kinne, Stefan; Vardavas, Ilias

    2015-04-01

    It is now well-established that aerosols cause an overall cooling effect at the surface and a warming effect within the atmosphere. At the top of the atmosphere (TOA), both positive and negative forcing can be found, depending on a number of other factors, such as surface albedo and relative position of clouds and aerosols. Whilst aerosol surface cooling is important due to its relation with surface temperature and other bio-environmental reasons, atmospheric heating is of special interest as well having significant impacts on atmospheric dynamics, such as formation of clouds and subsequent precipitation. The actual position of aerosols and their altitude relative to clouds is of major importance as certain types of aerosol, such as black carbon (BC) above clouds can have a significant impact on planetary albedo. The vertical distribution of aerosols and clouds has recently drawn the attention of the aerosol community, because partially can account for the differences between simulated aerosol radiative forcing with various models, and therefore decrease the level of our uncertainty regarding aerosol forcing, which is one of our priorities set by IPCC. The vertical profiles of aerosol optical and physical properties have been studied by various research groups around the world, following different methodologies and using various indices in order to present the impact of aerosols on radiation on different altitudes above the surface. However, there is still variability between the published results as to the actual effect of aerosols on shortwave radiation and on heating rate within the atmosphere. This study uses vertical information on aerosols from the Max Planck Aerosol Climatology (MAC-v1) global dataset, which is a combination of model output with quality ground-based measurements, in order to provide useful insight into the vertical profile of atmospheric heating for the Mediterranean region. MAC-v1 and the science behind this aerosol dataset have already

  6. Atmospheric aerosols: Their Optical Properties and Effects (supplement)

    Science.gov (United States)

    1976-01-01

    A digest of technical papers is presented. Topics include aerosol size distribution from spectral attenuation with scattering measurements; comparison of extinction and backscattering coefficients for measured and analytic stratospheric aerosol size distributions; using hybrid methods to solve problems in radiative transfer and in multiple scattering; blue moon phenomena; absorption refractive index of aerosols in the Denver pollution cloud; a two dimensional stratospheric model of the dispersion of aerosols from the Fuego volcanic eruption; the variation of the aerosol volume to light scattering coefficient; spectrophone in situ measurements of the absorption of visible light by aerosols; a reassessment of the Krakatoa volcanic turbidity, and multiple scattering in the sky radiance.

  7. Indirect fluorometric detection techniques on thin layer chromatography and effect of ultrasound on gel electrophoresis

    Energy Technology Data Exchange (ETDEWEB)

    Yinfa, Ma.

    1990-12-10

    Thin-layer chromatography (TLC) is a broadly applicable separation technique. It offers many advantages over high performance liquid chromatography (HPLC), such as easily adapted for two-dimensional separation, for whole-column'' detection and for handling multiple samples, etc. However, due to its draggy development of detection techniques comparing with HPLC, TLC has not received the attention it deserves. Therefore, exploring new detection techniques is very important to the development of TLC. It is the principal of this dissertation to present a new detection method for TLC -- indirect fluorometric detection method. This detection technique is universal sensitive, nondestructive, and simple. This will be described in detail from Sections 1 through Section 5. Section 1 and 3 describe the indirect fluorometric detection of anions and nonelectrolytes in TLC. In Section 2, a detection method for cations based on fluorescence quenching of ethidium bromide is presented. In Section 4, a simple and interesting TLC experiment is designed, three different fluorescence detection principles are used for the determination of caffeine, saccharin and sodium benzoate in beverages. A laser-based indirect fluorometric detection technique in TLC is developed in Section 5. Section 6 is totally different from Sections 1 through 5. An ultrasonic effect on the separation of DNA fragments in agarose gel electrophoresis is investigated. 262 refs.

  8. Effects of long-range aerosol transport on the microphysical properties of low-level liquid clouds in the Arctic

    Science.gov (United States)

    Coopman, Q.; Garrett, T. J.; Riedi, J.; Eckhardt, S.; Stohl, A.

    2015-11-01

    The properties of clouds in the Arctic can be altered by long-range aerosol transport to the region. The goal of this study is to use satellite, tracer transport model, and meteorological data sets to determine the effects of pollution on cloud microphysics due only to pollution itself and not to the meteorological state. Here, A-Train, POLDER-3 and MODIS satellite instruments are used to retrieve low-level liquid cloud microphysical properties over the Arctic between 2008 and 2010. Cloud retrievals are co-located with simulated pollution represented by carbon-monoxide concentrations from the FLEXPART tracer transport model. The sensitivity of clouds to pollution plumes - including aerosols - is constrained for cloud liquid water path, temperature, altitude, specific humidity, and lower tropospheric stability (LTS). We define an Indirect Effect (IE) parameter from the ratio of relative changes in cloud microphysical properties to relative variations in pollution concentrations. Retrievals indicate that, depending on the meteorological regime, IE parameters range between 0 and 0.34 for the cloud droplet effective radius, and between -0.10 and 0.35 for the optical depth, with average values of 0.12 ± 0.02 and 0.15 ± 0.02 respectively. The IE parameter increases with increasing specific humidity and LTS. Further, the results suggest that for a given set of meteorological conditions, the liquid water path of arctic clouds does not respond strongly to pollution. Or, not constraining sufficiently for meteorology may lead to artifacts that exaggerate the magnitude of the aerosol indirect effect. The converse is that the response of arctic clouds to pollution does depend on the meteorologic state. Finally, we find that IE values are highest when pollution concentrations are low, and that they depend on the source of pollution.

  9. The direct and indirect effects of corruption on motor vehicle crash deaths.

    Science.gov (United States)

    Hua, Law Teik; Noland, Robert B; Evans, Andrew W

    2010-11-01

    Recent empirical research has found that there is an inverted U-shaped or Kuznets relationship between income and motor vehicle crash (MVC) deaths, such that MVC deaths increase as national income increases and decrease after reaching a critical level. Corruption has been identified as one of the underlying factors that could affect this relationship, primarily by undermining institutional development and effective enforcement schemes. The total effect of corruption can be decomposed into two components, a direct and an indirect effect. The direct effect measures the immediate impact of corruption on MVC deaths by undermining effective enforcement and regulations, while the indirect effect captures the impact of corruption on hindering increases in per capita income and the consequent impact of reduced income on MVC deaths. By influencing economic growth, corruption can lead to an increase or decrease in MVC deaths depending on the income level. Using data from 60 countries between 1982 and 2003, these effects are estimated using linear panel and fixed effects negative binomial models. The estimation results suggest that corruption has different direct effects for less developed and highly developed countries. It has a negative (decreasing) effect on MVC deaths for less developed countries and a positive (increasing) effect on MVC deaths for highly developed countries. For highly developed countries, the total effect is positive at lower per capita income levels, but decreases with per capita income and becomes negative at per capita income levels of about US$ 38,248. For less developed countries, the total effect is negative within the sample range and decreases with increased per capita income. In summary, the results of this study suggest that reduction of corruption is likely a necessary condition to effectively tackle road safety problems. PMID:20728645

  10. Effect of Aerosol and Ocean Representation on Simulated Climate Responses

    Science.gov (United States)

    Dallafior, Tanja; Folini, Doris; Knutti, Reto; Wild, Martin

    2016-04-01

    It is still debated to what extent anthropogenic aerosols shaped 20th century surface temperatures, especially sea surface temperatures (SSTs), through alteration of surface solar radiation (SSR). SSTs, in turn, are crucial in the context of atmospheric circulation and ocean heat uptake. Uncertainty considering anthropogenic aerosol forcing thus translates into uncertainty regarding ocean heat uptake and, ultimately, climate responses towards anthropogenic influences. We use the global climate model ECHAM to analyse the 20th century climate response towards either anthropogenic aerosols or well-mixed greenhouse gases or both with different representations of ocean and aerosols: atmosphere-only with prescribed SSTs and interactive aerosols; mixed-layer ocean and interactive or prescribed aerosols; fully coupled with prescribed aerosols. For interactive aerosols we use the Hamburg Aerosol Module (HAM). Our results suggest that up to 15% of global ocean surfaces undergo an SSR reduction of at least -4W/m² in the year 2000, due to anthropogenic aerosols. The area affected depends on how aerosols are represented and whether clear sky or all sky SSR is considered. In MLO equilibria with interactive aerosols, anthropogenic aerosols clearly shape surface temperature response patterns. This is to a lesser degree the case for the transient fully coupled case. Additivity of global mean temperature responses towards single forcings - an assumption often made in the literature - is not fulfilled for the MLO experiments, but for the fully coupled experiments. While some of these differences can be attributed to the differing ocean representation, it is implied that differing aerosol representation may play an even more relevant role. Thus, our results corroborate not only the relevance of anthropogenic aerosols for surface temperature responses, but also highlight the relevance of choice of aerosol representation.

  11. A New Neighboring Pixels Method for Reducing Aerosol Effects on the NDVI Images

    OpenAIRE

    Dandan Wang; Yunhao Chen; Mengjie Wang; Jingling Quan; Tao Jiang

    2016-01-01

    A new algorithm was developed in this research to minimize aerosol effects on the normalized difference vegetation index (NDVI). Simulation results show that in red-NIR reflectance space, variations in red and NIR channels to aerosol optical depth (AOD) follow a specific pattern. Based on this rational, the apparent reflectance in these two bands of neighboring pixels were used to reduce aerosol effects on NDVI values of the central pixel. We call this method the neighboring pixels (NP) algor...

  12. Calculation of effective absorption coefficient for aerosols of internal mixture

    International Nuclear Information System (INIS)

    The effective absorption coefficient with time of strong absorbing aerosol made of carbon dusts and water of internal mixture is analyzed, and the influence of different wavelengths and radius ratios on it is discussed. The shorter the wavelength is, the larger the effective absorption coefficient is , and more quickly it increases during 1-100 μs, and the largest increase if 132.65% during 1-100 μs. Different ratios between inner and outer radius have large influence on the effective absorption coefficient. The larger the ratio is, the larger the effective absorption coefficient is, and more quickly it increases during 1-100 μs. The increase of the effective absorption coefficient during 1-100 μs is larger than that during 100-1000 μs, and the largest increase is 138.66% during 1-100 μs. (authors)

  13. THE EFFECT OF AEROSOLIZATION ON SUBSEQUENT BACTERIAL SURVIVAL

    Science.gov (United States)

    To determine whether aerosolization could impair baterial survival, Pseudomonas syringae and Erwinia herbicola were aerosolized in a greenhouse, the aerosol was sampled at various distances from the site of release by using all-glass impingers, and bacterial survival was followed...

  14. Linking mother and youth parenting attitudes: indirect effects via maltreatment, parent involvement, and youth functioning.

    Science.gov (United States)

    Thompson, Richard; Jones, Deborah J; Litrownik, Alan J; English, Diana J; Kotch, Jonathan B; Lewis, Terri; Dubowitz, Howard

    2014-01-01

    Evidence suggests that parenting attitudes are transmitted within families. However, limited research has examined this prospectively. The current prospective study examined direct effects of early maternal attitudes toward parenting (as measured at child age 4 by the Adult-Adolescent Parenting Inventory [AAPI]) on later youth parenting attitudes (as measured by the AAPI at youth age 18). Indirect effects via child maltreatment (physical abuse, sexual abuse, neglect, and emotional maltreatment), parent involvement, and youth functioning (internalizing and externalizing problems) were also assessed. Analyses were conducted on data from 412 families enrolled in the Longitudinal Studies of Child Abuse and Neglect (LONGSCAN). There were significant direct effects for three of the four classes of mother parenting attitudes (appropriate developmental expectations of children, empathy toward children, and appropriate family roles) on youth attitudes but not for rejection of punishment. In addition, the following indirect effects were obtained: Mother expectations influenced youth expectations via neglect; mother empathy influenced youth empathy via both parental involvement and youth externalizing problems; and mother rejection of punishment influenced youth rejection of punishment via youth internalizing problems. None of the child or family process variables, however, affected the link between mother and youth attitudes about roles. PMID:25113632

  15. OMI tropospheric NO2 air mass factors over South America: effects of biomass burning aerosols

    Directory of Open Access Journals (Sweden)

    P. Castellanos

    2015-03-01

    Full Text Available Biomass burning is an important and uncertain source of aerosols and NOx (NO + NO2 to the atmosphere. OMI observations of tropospheric NO2 are essential for characterizing this emissions source, but inaccuracies in the retrieval of NO2 tropospheric columns due to the radiative effects of aerosols, especially light-absorbing carbonaceous aerosols, are not well understood. It has been shown that the O2–O2 effective cloud fraction and pressure retrieval is sensitive to aerosol optical and physical properties, including aerosol optical depth (AOD. Aerosols implicitly influence the tropospheric air mass factor (AMF calculations used in the NO2 retrieval through the effective cloud parameters used in the independent pixel approximation. In this work, we explicitly account for the effects of biomass burning aerosols in the tropospheric NO2 AMF calculation by including collocated aerosol extinction vertical profile observations from the CALIOP instrument, and aerosol optical depth (AOD and single scattering albedo (SSA retrieved by the OMI near-UV aerosol algorithm (OMAERUV in the DISAMAR radiative transfer model for cloud-free scenes. Tropospheric AMFs calculated with DISAMAR were benchmarked against AMFs reported in the Dutch OMI NO2 (DOMINO retrieval; the mean and standard deviation (SD of the difference was 0.6 ± 8%. Averaged over three successive South American biomass burning seasons (2006–2008, the spatial correlation in the 500 nm AOD retrieved by OMI and the 532 nm AOD retrieved by CALIOP was 0.6, and 72% of the daily OMAERUV AOD observations were within 0.3 of the CALIOP observations. Overall, tropospheric AMFs calculated with observed aerosol parameters were on average 10% higher than AMFs calculated with effective cloud parameters. For effective cloud radiance fractions less than 30%, or effective cloud pressures greater than 800 hPa, the difference between tropospheric AMFs based on implicit and explicit aerosol parameters is on

  16. Direct and Indirect Effects of Marketing Effort on Brand Awareness and Brand Image.

    OpenAIRE

    Villarejo Ramos, Ángel Francisco; Rondán Cataluña, Francisco Javier; Sánchez Franco, Manuel Jesús

    2008-01-01

    The marketing effort orientated to towards strengthening the brand means to increase the degree of knowledge of the brand name. In this paper we want to show the relationship between brand awareness and brand image. Starting out from a theoretical review, we set out a model of direct and indirect effects of the marketing effort-as the brand's antecedents-on brand awareness and brand image. Via the empirical support used, a questionnaire of a sample of consumers, we try to find out how the mar...

  17. Comprehensive tool for calculation of radiative fluxes: illustration of shortwave aerosol radiative effect sensitivities to the details in aerosol and underlying surface characteristics

    Science.gov (United States)

    Derimian, Yevgeny; Dubovik, Oleg; Huang, Xin; Lapyonok, Tatyana; Litvinov, Pavel; Kostinski, Alex B.; Dubuisson, Philippe; Ducos, Fabrice

    2016-05-01

    The evaluation of aerosol radiative effect on broadband hemispherical solar flux is often performed using simplified spectral and directional scattering characteristics of atmospheric aerosol and underlying surface reflectance. In this study we present a rigorous yet fast computational tool that accurately accounts for detailed variability of both spectral and angular scattering properties of aerosol and surface reflectance in calculation of direct aerosol radiative effect. The tool is developed as part of the GRASP (Generalized Retrieval of Aerosol and Surface Properties) project. We use the tool to evaluate instantaneous and daily average radiative efficiencies (radiative effect per unit aerosol optical thickness) of several key atmospheric aerosol models over different surface types. We then examine the differences due to neglect of surface reflectance anisotropy, nonsphericity of aerosol particle shape and accounting only for aerosol angular scattering asymmetry instead of using full phase function. For example, it is shown that neglecting aerosol particle nonsphericity causes mainly overestimation of the aerosol cooling effect and that magnitude of this overestimate changes significantly as a function of solar zenith angle (SZA) if the asymmetry parameter is used instead of detailed phase function. It was also found that the nonspherical-spherical differences in the calculated aerosol radiative effect are not modified significantly if detailed BRDF (bidirectional reflectance distribution function) is used instead of Lambertian approximation of surface reflectance. Additionally, calculations show that usage of only angular scattering asymmetry, even for the case of spherical aerosols, modifies the dependence of instantaneous aerosol radiative effect on SZA. This effect can be canceled for daily average values, but only if sun reaches the zenith; otherwise a systematic bias remains. Since the daily average radiative effect is obtained by integration over a range

  18. The effect of changes in humidity on the size of submicron aerosols

    International Nuclear Information System (INIS)

    The effect of humidity on inhaled aerosols in the respiratory tract is to cause an increase in particle size of up to several times if the aerosol particle is hygroscopic. The presence of ionizing radiation and air ions (for example, from uranium and radon/thoron) increases the tendency of water vapour to nucleate. The desposition of particles in the lung is enhanced by high charge density (>10 charges/particle). Radon has been reported to play an important role in the formation of sulphate and nitrate particles in the atmosphere. A detailed overview of the effect of humidity on aerosols is presented in the present work. Results of experimental measurements made on NaCl (hygroscopic) and kerosene combustion (hydrophobic) aerosols under ambient and humid conditions are reported. Initial aerosol conditions were 20 degrees C and 35% R.H. Final aerosol conditions were maintained at 37 degrees C and 100% R.H. in order to simulate the conditions inside the respiratory tract. An average growth factor of 1.9 ± 0.4 (standard deviation) was observed for the NaCl aerosol and 1.3 ± 0.2 (standard deviation) for the kerosene aerosol. For the activity size distribution, however, the NaCl aerosols were observed to grow by an average factor of only 1.2 ± 0.1 (standard deviation) whereas the kerosene aerosols grew by a factor of 1.3 ± 0.2 (standard deviation)

  19. Reallocation in modal aerosol models: impacts on predicting aerosol radiative effects

    OpenAIRE

    Korhola, T.; H. Kokkola; Korhonen, H.; A.-I. Partanen; Laaksonen, A.; Lehtinen, K. E. J.; S. Romakkaniemi

    2013-01-01

    In atmospheric modelling applications the aerosol particle size distribution is commonly represented by modal approach, in which particles in different size ranges are described with log-normal modes within predetermined size ranges. Such method includes numerical reallocation of particles from a mode to another for example during particle growth, leading to potentially artificial changes in the aerosol size distribution. In this study we analysed how this reallocation affects climatologicall...

  20. Reallocation in modal aerosol models: impacts on predicting aerosol radiative effects

    OpenAIRE

    Korhola, T.; H. Kokkola; Korhonen, H.; Partanen, A.-I.; Laaksonen, A.; Lehtinen, K. E. J.; S. Romakkaniemi

    2014-01-01

    Atmospheric models often represent the aerosol particle size distribution with a modal approach, in which particles are described with log-normal modes within predetermined size ranges. This approach reallocates particles numerically from one mode to another for example during particle growth, potentially leading to artificial changes in the aerosol size distribution. In this study we analysed how the modal reallocation affects climate-relevant variables: cloud droplet numbe...

  1. Effects of atmospheric water on the optical properties of soot aerosols with different mixing states

    International Nuclear Information System (INIS)

    Soot aerosols have become the second most important contributor to global warming after carbon dioxide in terms of direct forcing, which is the dominant absorber of visible solar radiation. The optical properties of soot aerosols depend strongly on the mixing mechanism of black carbon with other aerosol components and its hygroscopic properties. In this study, the effects of atmospheric water on the optical properties of soot aerosols have been investigated using a superposition T-matrix method that accounts for the mixing mechanism of soot aerosols with atmospheric water. The dramatic changes in the optical properties of soot aerosols were attributed to its different mixing states with atmospheric water (externally mixed, semi-embedded mixed, and internally mixed). Increased absorption is accompanied by a larger increase in scattering, which is reflected by the increased single scattering albedo. The asymmetry parameter also increased when increasing the atmospheric water content. Moreover, atmospheric water intensified the radiative absorption enhancement attributed to the mixing states of the soot aerosols, with values ranging from 1.5 to 2.5 on average at 0.870 μm. The increased absorption and scattering ability of soot aerosols, which is attributed to atmospheric water, exerted an opposing effect on climate change. These findings should improve our understanding of the effects of atmospheric water on the optical properties of soot aerosols and their effects on climate. The mixing mechanism for soot aerosols and atmospheric water is important when evaluating the climate effects of soot aerosols, which should be explicitly considered in radiative forcing models. - Highlights: • Effects of atmospheric water on optical properties of soot aerosols are investigated. • Increased absorption is accompanied by a larger increase in scattering. • Atmospheric water intensified the absorption enhancement due the mixing states

  2. Dust aerosol impact on North Africa climate: a GCM investigation of aerosol-cloud-radiation interactions using A-Train satellite data

    Directory of Open Access Journals (Sweden)

    Y. Gu

    2012-02-01

    Full Text Available The climatic effects of dust aerosols in North Africa have been investigated using the atmospheric general circulation model (AGCM developed at the University of California, Los Angeles (UCLA. The model includes an efficient and physically based radiation parameterization scheme developed specifically for application to clouds and aerosols. Parameterization of the effective ice particle size in association with the aerosol first indirect effect based on ice cloud and aerosol data retrieved from A-Train satellite observations have been employed in climate model simulations. Offline simulations reveal that the direct solar, IR, and net forcings by dust aerosols at the top of the atmosphere (TOA generally increase with increasing aerosol optical depth. When the dust semi-direct effect is included with the presence of ice clouds, positive IR radiative forcing is enhanced since ice clouds trap substantial IR radiation, while the positive solar forcing with dust aerosols alone has been changed to negative values due to the strong reflection of solar radiation by clouds, indicating that cloud forcing associated with aerosol semi-direct effect could exceed direct aerosol forcing. With the aerosol first indirect effect, the net cloud forcing is generally reduced in the case for an ice water path (IWP larger than 20 g m−2. The magnitude of the reduction increases with IWP.

    AGCM simulations show that the reduced ice crystal mean effective size due to the aerosol first indirect effect results in less OLR and net solar flux at TOA over the cloudy area of the North Africa region because ice clouds with smaller size trap more IR radiation and reflect more solar radiation. The precipitation in the same area, however, increases due to the aerosol indirect effect on ice clouds, corresponding to the enhanced convection as indicated by reduced OLR. Adding the aerosol direct effect into the model simulation reduces the precipitation in the

  3. Factoring out natural and indirect human effects on terrestrial carbon sources and sinks

    International Nuclear Information System (INIS)

    The capacity to partition natural, indirect, and direct human-induced effects on terrestrial carbon (C) sources and sinks is necessary to be able to predict future terrestrial C dynamics and thus their influence on atmospheric CO2 growth. However, it will take a number of years before we can better attribute quantitative estimates of the contribution of various C processes to the net C balance. In a policy context, factoring out natural and indirect human-induced effects on C sources and sinks from the direct human-induced influences, is seen as a requirement of a C accounting approach that establishes a clear and unambiguous connection between human activities and the assignment of C credits and debits. We present options for factoring out various groups of influences including climate variability, CO2 and N fertilization, and legacies from forest management. These are: (1) selecting longer accounting or measurement periods to reduce the effects of inter-annual variability; (2) correction of national inventories for inter-annual variability; (3) use of activity-based accounting and C response curves; (4) use of baseline scenarios or benchmarks at the national level; (5) stratification of the landscape into units with distinct average C stocks. Other, more sophisticated modeling approaches (e.g., demographic models in combination with forest inventories; process-based models) are possible options for future C accounting systems but their complexity and data requirements make their present adoption more difficult in an inclusive international C accounting system

  4. Role of indirect radiation effects on cell membranes in the immune response

    International Nuclear Information System (INIS)

    Recent work by Petkau indicates that, in sharp contrast to the case of damage to the genes, the doubling dose for indirect radiation damage to cell membranes decreases as the dose rate declines, apparently as the result of a free-radical-mediated oxidative reaction involving O2-. These findings explain the earlier results of Stokke, who observed significant declines in bone-marrow cellularity of the hematopoietic stem cells involved in the immune processes at dose rates below 10-4 rad/min for total doses of only 0.1 to 2000 mrads, the doubling dose declining with total dose administered over periods of 6 to 18 weeks in a manner similar to that observed by Petkau. These observations, furthermore, explain the fact that erythrocyte permeability to monovalent cations can be significantly increased in occupationally exposed individuals at total doses of only 10 to 30 mR in 1 month, whereas thousands of rads are required at therapeutic dose rates. Evidence is presented suggesting the dominance of indirect, free-radical-mediated radiation effects over direct somatic mutation effects at background radiation rates on the development of cancer, leukemia, and infectious diseases from small radiation exposures encountered in the environment. The implications or the relative biological effect on the immune system of radiation at high and low dose rates are discussed

  5. Indirect wrist MR arthrography: the effects of passive motion versus active exercise

    International Nuclear Information System (INIS)

    Purpose. In the wrist, to determine whether passive motion or active exercise yields a better indirect MR arthrographic effect following intravenous gadolinium administration.Design and patients. Twenty-six consecutive patients were studied by indirect wrist MR arthrography. In half active exercise and in half passive motion was performed. Four regions of interest were studied including the distal radioulnar joint, the radiocarpal joint, the midcarpal joint, and the triangular fibrocartilage. Ranges and means of signal intensity were calculated. Surgical follow-up was performed in 22 patients.Results. The joint fluid intensity was greatest in the distal radioulnar joint. Fluid signal intensity was greater and more consistent in the passive motion group although the results did not achieve statistical significance. Imaging accuracy appeared similar in the two groups and was excellent for the triangular fibrocartilage (100%) and scapholunate ligaments (96%).Conclusion. Active exercise and passive motion yield similar degrees of wrist arthrographic effect, but the effect of passive motion is somewhat more consistent. Preliminary data show good accuracy for internal derangements. (orig.)

  6. A simple unified approach for estimating natural direct and indirect effects.

    Science.gov (United States)

    Lange, Theis; Vansteelandt, Stijn; Bekaert, Maarten

    2012-08-01

    An important problem within both epidemiology and many social sciences is to break down the effect of a given treatment into different causal pathways and to quantify the importance of each pathway. Formal mediation analysis based on counterfactuals is a key tool when addressing this problem. During the last decade, the theoretical framework for mediation analysis has been greatly extended to enable the use of arbitrary statistical models for outcome and mediator. However, the researcher attempting to use these techniques in practice will often find implementation a daunting task, as it tends to require special statistical programming. In this paper, the authors introduce a simple procedure based on marginal structural models that directly parameterize the natural direct and indirect effects of interest. It tends to produce more parsimonious results than current techniques, greatly simplifies testing for the presence of a direct or an indirect effect, and has the advantage that it can be conducted in standard software. However, its simplicity comes at the price of relying on correct specification of models for the distribution of mediator (and exposure) and accepting some loss of precision compared with more complex methods. Web Appendixes 1 and 2, which are posted on the Journal's Web site (http://aje.oupjournals.org/), contain implementation examples in SAS software (SAS Institute, Inc., Cary, North Carolina) and R language (R Foundation for Statistical Computing, Vienna, Austria). PMID:22781427

  7. Biphasic effects of direct, but not indirect, GABA mimetics and antagonists on haloperidol-induced catalepsy.

    Science.gov (United States)

    Worms, P; Lloyd, K G

    1980-03-01

    At very low doses the GABA agonists SL 76002 and muscimol diminish haloperidol-induced catalepsy. At somewhat higher doses these compounds potentiate catalepsy. Biphasic effects on DA-receptor mediated functions have previously been noted with bicuculline and picrotoxinin. In contrast, manipulation of GABA levels by enzyme inhibition induced only a monophasic effect on dopamine-mediated behaviour. The potentiation of GABA levels by enzyme inhibition induced only a monophasic effect on dopamine-mediated behaviour. The potentiation of haloperidol-induced catalepsy by GABA mimetics is also observed with dipropylacetate, delta-aminovaleric acid and gamma-acetylenic GABA. This GABA-mimetic potentiation of catakepsy was blocked by the coadministration of bicuculline. These results confirm and extend the hypothesis that GABA-neurons influence DA neuron function. Furthermore they suggest that more than one group of GABA receptors influence directly and/or indirectly DA neuronal function, with different resultant effects. PMID:7189827

  8. The relative importance of direct and indirect effects of hunting mortality on the population dynamics of brown bears

    OpenAIRE

    Gosselin, Jacinthe; Zedrosser, Andreas; Swenson, Jon; Pelletier, Fanie

    2014-01-01

    There is increasing evidence of indirect effects of hunting on populations. In species with sexually selected infanticide (SSI), hunting may decrease juvenile survival by increasing male turnover.We aimed to evaluate the relative importance of direct and indirect effects of hunting via SSI on the population dynamics of the Scandinavian brown bear (Ursus arctos). We performed prospective and retrospective demographic perturbation analyses for periods with low and high hunting...

  9. Aircraft-Measured Indirect Cloud Effects from Biomass Burning Smoke in the Arctic and Subarctic

    Science.gov (United States)

    Zamora, L. M.; Kahn, R. A.; Cubison, M. J.; Diskin, G. S.; Jimenez, J. L.; Kondo, Y.; McFarquhar, G. M.; Nenes, A.; Thornhill, K. L.; Wisthaler, A.; Zelenyuk, A.; Ziemba, L. D.

    2016-01-01

    The incidence of wildfires in the Arctic and subarctic is increasing; in boreal North America, for example, the burned area is expected to increase by 200-300% over the next 50-100 years, which previous studies suggest could have a large effect on cloud microphysics, lifetime, albedo, and precipitation. However, the interactions between smoke particles and clouds remain poorly quantified due to confounding meteorological influences and remote sensing limitations. Here, we use data from several aircraft campaigns in the Arctic and subarctic to explore cloud microphysics in liquid-phase clouds influenced by biomass burning. Median cloud droplet radii in smoky clouds were approx. 40- 60% smaller than in background clouds. Based on the relationship between cloud droplet number (N(liq)/ and various biomass burning tracers (BBt/ across the multi-campaign data set, we calculated the magnitude of subarctic and Arctic smoke aerosol-cloud interactions (ACIs, where ACI = (1/3) x dln(N(liq))/dln(BBt)) to be approx. 0.16 out of a maximum possible value of 0.33 that would be obtained if all aerosols were to nucleate cloud droplets. Interestingly, in a separate subarctic case study with low liquid water content (0.02 gm/cu m and very high aerosol concentrations (2000- 3000/ cu cm in the most polluted clouds, the estimated ACI value was only 0.05. In this case, competition for water vapor by the high concentration of cloud condensation nuclei (CCN) strongly limited the formation of droplets and reduced the cloud albedo effect, which highlights the importance of cloud feedbacks across scales. Using our calculated ACI values, we estimate that the smoke-driven cloud albedo effect may decrease local summertime short-wave radiative flux by between 2 and 4 W/sq m or more under some low and homogeneous cloud cover conditions in the subarctic, although the changes should be smaller in high surface albedo regions of the Arctic.We lastly explore evidence suggesting that numerous northern

  10. Aircraft-measured indirect cloud effects from biomass burning smoke in the Arctic and subarctic

    Science.gov (United States)

    Zamora, L. M.; Kahn, R. A.; Cubison, M. J.; Diskin, G. S.; Jimenez, J. L.; Kondo, Y.; McFarquhar, G. M.; Nenes, A.; Thornhill, K. L.; Wisthaler, A.; Zelenyuk, A.; Ziemba, L. D.

    2016-01-01

    The incidence of wildfires in the Arctic and subarctic is increasing; in boreal North America, for example, the burned area is expected to increase by 200-300 % over the next 50-100 years, which previous studies suggest could have a large effect on cloud microphysics, lifetime, albedo, and precipitation. However, the interactions between smoke particles and clouds remain poorly quantified due to confounding meteorological influences and remote sensing limitations. Here, we use data from several aircraft campaigns in the Arctic and subarctic to explore cloud microphysics in liquid-phase clouds influenced by biomass burning. Median cloud droplet radii in smoky clouds were ˜ 40-60 % smaller than in background clouds. Based on the relationship between cloud droplet number (Nliq) and various biomass burning tracers (BBt) across the multi-campaign data set, we calculated the magnitude of subarctic and Arctic smoke aerosol-cloud interactions (ACIs, where ACI = (1/3) × dln(Nliq)/dln(BBt)) to be ˜ 0.16 out of a maximum possible value of 0.33 that would be obtained if all aerosols were to nucleate cloud droplets. Interestingly, in a separate subarctic case study with low liquid water content ( ˜ 0.02 g m-3) and very high aerosol concentrations (2000-3000 cm-3) in the most polluted clouds, the estimated ACI value was only 0.05. In this case, competition for water vapor by the high concentration of cloud condensation nuclei (CCN) strongly limited the formation of droplets and reduced the cloud albedo effect, which highlights the importance of cloud feedbacks across scales. Using our calculated ACI values, we estimate that the smoke-driven cloud albedo effect may decrease local summertime short-wave radiative flux by between 2 and 4 W m-2 or more under some low and homogeneous cloud cover conditions in the subarctic, although the changes should be smaller in high surface albedo regions of the Arctic. We lastly explore evidence suggesting that numerous northern

  11. Potential sensitivity of photosynthesis and isoprene emission to direct radiative effects of atmospheric aerosol pollution

    OpenAIRE

    2015-01-01

    A global Earth system model is applied to quantify the impacts of direct anthropogenic aerosol effective radiative forcing on gross primary productivity (GPP) and isoprene emission. The impacts of different pollution aerosol sources (all anthropogenic, biomass burning and non-biomass burning) are investigated by performing sensitivity experiments. On the global scale, our results show that land carbon fluxes (GPP and isoprene emission) are not sensitive to pollution aerosols...

  12. Effects of stratospheric sulfate aerosol geo-engineering on cirrus clouds

    OpenAIRE

    M. Kuebbeler; U. Lohmann; J. Feichter

    2012-01-01

    Cooling the Earth through the injection of sulphate into the stratosphere is one of the most discussed geo-engineering (GE) schemes. Stratospheric aerosols can sediment into the troposphere, modify the aerosol composition and thus might impact cirrus clouds. We use a global climate model with a physically based parametrization for cirrus clouds in order to investigate possible microphysical and dynamical effects. We find that enhanced stratospheric aerosol loadings as proposed by several GE a...

  13. Exploring the Longwave Radiative Effects of Dust Aerosols

    Science.gov (United States)

    Hansell, Richard A., Jr.

    2012-01-01

    Dust aerosols not only affect air quality and visibility where they pose a significant health and safety risk, but they can also play a role in modulating the energy balance of the Earth-atmosphere system by directly interacting with local radiative fields. Consequently, dust aerosols can impact regional climate patterns such as changes in precipitation and the evolution of the hydrological cycle. Assessing the direct effect of dust aerosols at the solar wavelengths is fairly straightforward due in part to the relatively large signal-to-noise ratio in broadband irradiance measurements. The longwave (LW) impacts, on the other hand, are rather difficult to ascertain since the measured dust signal level (10 Wm-2) is on the same order as the instrumental uncertainties. Moreover, compared to the shortwave (SW), limited experimental data on the LW optical properties of dust makes it a difficult challenge for constraining the LW impacts. Owing to the strong absorption features found in many terrestrial minerals (e.g., silicates and clays), the LW effects, although much smaller in magnitude compared to the SW, can still have a sizeable impact on the energetics of the Earth-atmosphere system, which can potentially trigger changes in the heat and moisture surface budgets, and dynamics of the atmosphere. The current endeavor is an integral part of an on-going research study to perform detailed assessments of dust direct aerosol radiative effects (DARE) using comprehensive global datasets from NASA Goddards mobile ground-based facility (cf. http://smartlabs.gsfc.nasa.gov/) during previous field experiments near key dust source regions. Here we examine and compare the results from two of these studies: the 2006 NASA African Monsoon Multidisciplinary Activities and the 2008 Asian Monsoon Years. The former study focused on transported Saharan dust at Sal Island (16.73N, 22.93W), Cape Verde along the west coast of Africa while the latter focused on Asian dust at Zhangye China (39

  14. Linking social anxiety and adolescent romantic relationship functioning: indirect effects and the importance of peers.

    Science.gov (United States)

    Hebert, Karen R; Fales, Jessica; Nangle, Douglas W; Papadakis, Alison A; Grover, Rachel L

    2013-11-01

    Peer relationships undergo dramatic shifts in form and function during adolescence, at the same time the incidence of socially evaluative fears sharply rises. Despite well-established links between social anxiety and broader interpersonal functioning, there is a dearth of research evaluating the impact of social anxiety on functioning in close relationships during this developmental stage. The present study examines the impact of social anxiety on functioning in close friendships and romantic relationships during adolescence. From a developmental psychopathology perspective, it was expected that social anxiety would influence functioning (quality, length, satisfaction) in romantic relationships through its influence on functioning in same- and other-sex friendships. Participants included 314 adolescents (60.5% female, 14-19 years of age) with a prior or current history of romantic relationship involvement. Structural equation modeling was used to test a mediation model positing an indirect pathway from social anxiety to romantic relationship functioning through functioning in close same- and other-sex friendships. Given known gender differences in social anxiety and relationship functioning, gender also was explored as a potential moderator. Results supported the hypothesized indirect pathway whereby social anxiety was associated with impairment in same-sex friendships; functioning in same-sex friendships was associated with functioning in other-sex friendships, which was associated, in turn, with functioning in romantic relationships. While the hypothesized indirect pathway was significant among both boys and girls, there was greater continuity of functioning between same- and other-sex friendships for girls. These findings highlight the importance of examining the multiple downstream effects of social anxiety on perceived social functioning in adolescence, and suggest that continuity may exist for maladaptive patterns of socialization, particularly across

  15. Pecularities of mutagenesis of T4Br bacteriophage under the direct and indirect radiation effects

    International Nuclear Information System (INIS)

    Different lethal and mutagenic effects were shown when bacteriophage T4Br+ (470 r/min) was irradiated in broth (direct effect) and a buffer solution (direct and indirect action). The survival rate of the bacteriophage in the buffer solution was 0.1 percent for a dose rate of 60 kr; in the broth it was 10 percent. The frequency of mutation of the bacteriophage also showed the greater effect of the irradiation in the buffer solution than in the broth (25 and 5 r-mutants respectively at a dose rate of 10 kr). An analysis of the ratio of the r-groups when the bacteriophage was treated in various ways revealed differences between mutagenesis produced in the broth and the buffer, and spontaneous mutagenesis. (V.A.P.)

  16. Life-Cycle Costing of Food Waste Management in Denmark: Importance of Indirect Effects

    DEFF Research Database (Denmark)

    Martinez Sanchez, Veronica; Tonini, Davide; Møller, Flemming;

    2016-01-01

    Prevention has been suggested as the preferred food waste management solution compared to alternatives such as conversion to animal fodder or to energy. In this study we used societal life-cycle costing, as a welfare economic assessment, and environmental life-cycle costing, as a financial...... assessment combined with life-cycle assessment, to evaluate food waste management. Both life-cycle costing assessments included direct and indirect effects. The latter are related to income effects, accounting for the marginal consumption induced when alternative scenarios lead to different household...... unpurchased food commodities were spent on goods/services with a more environmentally damaging production than that of the (prevented) food. This was not the case when savings were used, e.g., for health care, education, and insurances. This study demonstrates that income effects, although uncertain, should...

  17. The relationship between aerosol and cloud drop number concentrations in a global aerosol microphysics model

    Directory of Open Access Journals (Sweden)

    K. J. Pringle

    2009-06-01

    Full Text Available Empirical relationships that link cloud droplet number (CDN to aerosol number or mass are commonly used to calculate global fields of CDN for climate forcing assessments. In this work we use a sectional global model of sulfate and sea-salt aerosol coupled to a mechanistic aerosol activation scheme to explore the limitations of this approach. We find that a given aerosol number concentration produces a wide range of CDN concentrations due to variations in the shape of the aerosol size distribution. On a global scale, the dependence of CDN on the size distribution results in regional biases in predicted CDN (for a given aerosol number. Empirical relationships between aerosol number and CDN are often derived from regional data but applied to the entire globe. In an analogous process, we derive regional "correlation-relations" between aerosol number and CDN and apply these regional relations to calculations of CDN on the global scale. The global mean percentage error in CDN caused by using regionally derived CDN-aerosol relations is 20 to 26%, which is about half the global mean percentage change in CDN caused by doubling the updraft velocity. However, the error is as much as 25–75% in the Southern Ocean, the Arctic and regions of persistent stratocumulus when an aerosol-CDN correlation relation from the North Atlantic is used. These regions produce much higher CDN concentrations (for a given aerosol number than predicted by the globally uniform empirical relations. CDN-aerosol number relations from different regions also show very different sensitivity to changing aerosol. The magnitude of the rate of change of CDN with particle number, a measure of the aerosol efficacy, varies by a factor 4. CDN in cloud processed regions of persistent stratocumulus is particularly sensitive to changing aerosol number. It is therefore likely that the indirect effect will be underestimated in these important regions.

  18. The relationship between aerosol and cloud drop number concentrations in a global aerosol microphysics model

    Directory of Open Access Journals (Sweden)

    K. J. Pringle

    2009-01-01

    Full Text Available Empirical relationships that link cloud droplet number (CDN to aerosol number or mass are commonly used to calculate global fields of CDN for climate forcing assessments. In this work we use a sectional global model of sulfate and sea-salt aerosol coupled to a mechanistic aerosol activation scheme to explore the limitations of this approach. We find that a given aerosol number concentration produces a wide range of CDN concentrations due to variations in the shape of the aerosol size distribution. On a global scale, the dependence of CDN on the size distribution results in regional biases in predicted CDN (for a given aerosol number. Empirical relationships between aerosol number and CDN are often derived from regional data but applied to the entire globe. In an analogous process, we derive regional "correlation-relations" between aerosol number and CDN and apply these regional relations to calculations of CDN on the global scale. The global mean percentage error in CDN caused by using regionally derived CDN-aerosol relations is 20 to 26%, which is about half the global mean percentage change in CDN caused by doubling the updraft velocity. However, the error is as much as 25–75% in the Southern Ocean, the Arctic and regions of persistent stratocumulus when an aerosol-CDN correlation relation from the North Atlantic is used. These regions produce much higher CDN concentrations (for a given aerosol number than predicted by the globally uniform empirical relations. CDN-aerosol number relations from different regions also show very different sensitivity to changing aerosol. The magnitude of the rate of change of CDN with particle number, a measure of the aerosol efficacy, varies by a factor 4. CDN in cloud processed regions of persistent stratocumulus is particularly sensitive to changing aerosol number. It is therefore likely that the indirect effect will be underestimated in these important regions.

  19. Effects of aerosol sources and chemical compositions on cloud drop sizes and glaciation temperatures

    Science.gov (United States)

    Zipori, Assaf; Rosenfeld, Daniel; Tirosh, Ofir; Teutsch, Nadya; Erel, Yigal

    2015-09-01

    The effect of aerosols on cloud properties, such as its droplet sizes and its glaciation temperatures, depends on their compositions and concentrations. In order to examine these effects, we collected rain samples in northern Israel during five winters (2008-2011 and 2013) and determined their chemical composition, which was later used to identify the aerosols' sources. By combining the chemical data with satellite-retrieved cloud properties, we linked the aerosol types, sources, and concentrations with the cloud glaciation temperatures (Tg). The presence of dust increased Tg from -26°C to -12°C already at relatively low dust concentrations. This result is in agreement with the conventional wisdom that desert dust serves as good ice nuclei (INs). With higher dust concentrations, Tg saturated at -12°C, even though cloud droplet sizes decreased as a result of the cloud condensation nucleating (CCN) activity of the dust. Marine air masses also encouraged freezing, but in this case, freezing was enhanced by the larger cloud droplet sizes in the air masses (caused by low CCN concentrations) and not by IN concentrations or by aerosol type. An increased fraction of anthropogenic aerosols in marine air masses caused a decrease in Tg, indicating that these aerosols served as poor IN. Anthropogenic aerosols reduced cloud droplet sizes, which further decreased Tg. Our results could be useful in climate models for aerosol-cloud interactions, as we investigated the effects of aerosols of different sources on cloud properties. Such parameterization can simplify these models substantially.

  20. Maritime Aerosol Network (MAN) as a Component of AERONET

    Science.gov (United States)

    Smirnov, A.; Holben, B. N.; Slutsker, I.; Giles, D. M.; McClain, C. R.; Eck, T. F.; Sakerin, S. M.; Macke, A.; Croot, P.; Zibordi, G.; Quinn, P. K.

    2008-01-01

    The World Ocean produces a large amount of natural aerosols that have all impact on the Earth's albedo and climate. Sea-salt is the major contributor to aerosol optical depth over the oceans. [Mahowald et al. 2006; Chin et al. 2002; Satheesh et al. 1999; Winter and Chylek, 1997] and therefore affects the radiative balance over the ocean through the direct [Haywood et al. 1999] and indirect aerosol effect [O'Dowd et al. 1999]. Aerosols over the oceans (produced marine and advected from land sources) are important for various atmospheric processes [Lewis and Schwartz, 2004] and remote sensing studies [Gordon, 1997].

  1. Educational Tracking and Juvenile Deviance in Taiwan: Direct Effect, Indirect Effect, or Both.

    Science.gov (United States)

    Lin, Wen-Hsu; Yi, Chin-Chun

    2016-02-01

    Educational tracking in Chinese society is quite different from that in Western society, in that the allocation to either the vocational or academic track is based on a national entrance examination, which happens at ninth grade (age 14-15). Hence, students in many Asian countries (e.g., China and Taiwan) have to face academic tracking in early adolescence. Because of cultural emphasis on education in Taiwan, the impact of tracking on deviance is profound and can be seen as a crucial life-event. With this concept in mind, we examine how educational tracking influences adolescent deviance during high school. In addition, we also examine how educational tracking may indirectly influence deviance through other life domains, including depression, delinquent peer association, and school attachment. By using longitudinal data (the Taiwan Youth Project), we find that educational tracking increases deviance not only directly but also indirectly through delinquent peers and low school attachment. Some implications and limitations are also discussed. PMID:25189700

  2. Importance of Raman Lidar Aerosol Extinction Measurements for Aerosol-Cloud Interaction Studies

    Directory of Open Access Journals (Sweden)

    Han Zaw

    2016-01-01

    Full Text Available Using a UV Raman Lidar for aerosol extinction, and combining Microwave Radiometer derived Liquid Water Path (LWP with Multifilter Rotating Shadowband Radiometer derived Cloud Optical depth, to get cloud effective radius (Reff, we observe under certain specialized conditions, clear signatures of the Twomey Aerosol Indirect effect on cloud droplet properties which are consistent with the theoretical bounds. We also show that the measurement is very sensitive to how far the aerosol layer is from the cloud base and demonstrate that surface PM25 is far less useful. Measurements from both the DOE ARM site and new results at CCNY are presented.

  3. Quantifying the effect of organic aerosol aging and intermediate-volatility emissions on regional-scale aerosol pollution in China.

    Science.gov (United States)

    Zhao, Bin; Wang, Shuxiao; Donahue, Neil M; Jathar, Shantanu H; Huang, Xiaofeng; Wu, Wenjing; Hao, Jiming; Robinson, Allen L

    2016-01-01

    Secondary organic aerosol (SOA) is one of the least understood constituents of fine particles; current widely-used models cannot predict its loadings or oxidation state. Recent laboratory experiments demonstrated the importance of several new processes, including aging of SOA from traditional precursors, aging of primary organic aerosol (POA), and photo-oxidation of intermediate volatility organic compounds (IVOCs). However, evaluating the effect of these processes in the real atmosphere is challenging. Most models used in previous studies are over-simplified and some key reaction trajectories are not captured, and model parameters are usually phenomenological and lack experimental constraints. Here we comprehensively assess the effect of organic aerosol (OA) aging and intermediate-volatility emissions on regional-scale OA pollution with a state-of-the-art model framework and experimentally constrained parameters. We find that OA aging and intermediate-volatility emissions together increase OA and SOA concentrations in Eastern China by about 40% and a factor of 10, respectively, thereby improving model-measurement agreement significantly. POA and IVOCs both constitute over 40% of OA concentrations, and IVOCs constitute over half of SOA concentrations; this differs significantly from previous apportionment of SOA sources. This study facilitates an improved estimate of aerosol-induced climate and health impacts, and implies a shift from current fine-particle control policies. PMID:27350423

  4. The Impact of Different Regimes in Estimating the Effects of Aerosols on Clouds. A Case Study over the Baltic Sea Countries.

    Science.gov (United States)

    Saponaro, G.

    2015-12-01

    The present study investigates the use of long-term satellite data to assess the influence of aerosols upon cloud parameters over the Baltic Sea region. This particular area offers the contrast of a very clean environment (Fennoscandia) against a more polluted one (Germany, Poland). The datasets used in this study consist of Collection 6 Level 3 daily observations from 2002 to 2014 retrieved from observations by the NASA's Moderate-Resolution Imaging Spectrometer (MODIS) instrument on-board the Aqua platform. The MODIS aerosol optical depth (AOD) and aerosol index (AI) products are used as a proxy for the number concentration of aerosol particles while the cloud effective radius (CER) and cloud optical thickness (COT) describe cloud microphysical and optical properties respectively. Through the analysis of a 12-years dataset, distribution maps provide information on a regional scale about the first aerosol indirect effect (AIE) by determining the aerosol-cloud interaction (ACI). The ACI is defined as the change in cloud optical depth or effective radius as a function of aerosol load, for which AI is used as a proxy, for a fixed liquid water path (LWP). Reanalysis data from ECMWF, namely ERA-Interim, are used to estimate meteorological settings on a regional scale. The relative humidity (RH) and specific humidity (SH) are chosen at the pressure level of 950 hPa and they are linearly interpolated to match MODIS resolution of 1 x 1 deg. The Lower Tropospheric Stability (LTS) is computed from the ERA- Interim reanalysis data as the difference between the potential temperature at 700hPa and the surface. In order to better identify and interpret the AIE, this study proposes a framework where the interactions between aerosols and clouds are estimated by dividing the dataset into different regimes. Regimes are defined by: Liquid Water Path (LWP). The discrimination by LWP allows assessing the Twomey effect. The AIE is more evident when the LWP is lower. Aerosol loading

  5. Climate response due to carbonaceous aerosols and aerosol-induced SST effects in NCAR community atmospheric model CAM3.5

    Directory of Open Access Journals (Sweden)

    W.-C. Hsieh

    2013-08-01

    Full Text Available This study used the Community Atmospheric Model 3.5 (CAM3.5 to investigate the effects of carbonaceous aerosols on climate. The simulations include control runs with 3 times the mass of carbonaceous aerosols as compared to the model's default carbonaceous aerosol mass, as well as no-carbon runs in which carbonaceous aerosols were removed. The slab ocean model (SOM and the fixed sea surface temperature (SST were used to examine effects of ocean boundary conditions. Throughout this study, climate response induced by aerosol forcing was mainly analyzed in the following three terms: (1 aerosol radiative effects under fixed SST, (2 effects of aerosol-induced SST feedbacks, and (3 total effects including effects of aerosol forcing and SST feedbacks. The change of SST induced by aerosols has large impacts on distribution of climate response; the magnitudes in response patterns such as temperature, precipitation, zonal winds, mean meridional circulation, radiative fluxes, and cloud coverage are different between the SOM and fixed SST runs. Moreover, different spatial responses between the SOM and fixed SST runs can also be seen in some local areas. This implies the importance of SST feedbacks on simulated climate response. The aerosol dimming effects cause a cooling predicted at low layers near the surface in most carbonaceous aerosol source regions. The temperature response shows a warming (cooling predicted in the north (south high latitudes, suggesting that aerosol forcing can cause climate change in regions far away from its origins. Our simulation results show that direct and semidirect radiative forcing due to carbonaceous aerosols decreases rainfall in the tropics. This implies that carbonaceous aerosols have possibly strong influence on weakening of the tropical circulation. Most changes in precipitation are negatively correlated with changes of radiative fluxes at the top of model. The changes in radiative fluxes at top of model are physically

  6. Observed correlations between aerosol and cloud properties in an Indian Ocean trade cumulus regime

    OpenAIRE

    K. Pistone; P. S. Praveen; R. M. Thomas; Ramanathan, V.; Wilcox, E; F. A.-M. Bender

    2015-01-01

    There are many contributing factors which determine the micro- and macrophysical properties of clouds, including atmospheric structure, dominant meteorological conditions, and aerosol concentration, all of which may be coupled to one another. In the quest to determine aerosol effects on clouds, these potential relationships must be understood, as changes in atmospheric conditions due to aerosol may change the expected magnitude of indirect effects by altering cl...

  7. Effects of DTPA aerosol on lung contamination by lanthanum

    International Nuclear Information System (INIS)

    Applying DTPA aerosol for the treatment of lung contamination by lanthanum we were able to determine its effectiveness as a function of time. Provided it was administered early during the two hours after exposure, over 50 per cent could be removed using lower therapeutic doses than those prescribed for other routes of administration. Its association with some enzymes did not enhance the chelator therapeutic effect. We also calculated the constant of passage of lanthanum through the alveolar wall and found a value of 0.016 mn-1. Finally, as we have discovered a large part cannot be mobilized by DTPA, we shall now study the physico-chemical mechanisms involved in this protection. (authors)

  8. Indirect effects of sea otters on rockfish (Sebastes spp.) in giant kelp forests.

    Science.gov (United States)

    Markel, Russell W; Shurin, Jonathan B

    2015-11-01

    Sea otters are a classic example of a predator controlling ecosystem productivity through cascading effects on basal, habitat-forming kelp species. However, their indirect effects on other kelp-associated taxa like fishes are poorly understood. We examined the effects of sea otter (Enhydra lutris) reintroduction along the west coast of Vancouver Island, Canada on giant kelp (Macrocystis pyrifera) distributions and the trophic niches and growth of two common kelp forest fishes, black (Sebastes melanops) and copper (S. caurinus) rockfishes. We sampled 47 kelp forests, and found that red sea urchins (Strongylocentrotus franciscanus) were eliminated in the presence of otters, and that kelp forests were 3.7 times deeper and 18.8 times larger. Despite order-of-magnitude differences in kelp forest size, adult black and copper rockfishes contained less kelp-derived carbon in their tissues (as measured by stable isotopes of C and N) in regions with otters. Adults of both species had higher mean trophic positions in the presence of otters, indicating more frequent consumption of higher trophic level prey such as fishes. Smaller trophic niche space of rockfishes in the presence of otters indicated a higher degree of trophic specialization. Juvenile black rockfishes rapidly shifted to higher kelp-carbon contents, trophic positions, and body condition factors after settling in kelp forests. The relationships of growth to length, percentage of kelp carbon, and trophic position varied between the two regions, indicating that potential effects of kelp forest size on trophic ontogeny may also affect individual performance. Our results provide evidence that the indirect effects of otters on rockfishes arise largely through the creation of habitat for fishes and other prey rather than a direct trophic connection through invertebrates or other consumers of kelp productivity. PMID:27070008

  9. The effects of reactor core-simulant aerosols on hydrogen/air combustion

    International Nuclear Information System (INIS)

    Three representative reactor core-simulant aerosols were dispersed, just before ignition, into combustible hydrogen-air mixtures contained in 5.1 and 0.18 m/sup 3/ chambers. Oxidic aerosols (Al/sub 2/O/sub 3/, Fe/sub 2/O/sub 3/) produced only minor changes in the burns. A metallic aerosol (Fe) ignited along with the hydrogen, producing more complete combustion of the hydrogen and substantially increased overpressures and thermal effects compared to control experiments performed identically without the aerosols

  10. Interpersonal communication as an indirect pathway for the effect of antismoking media content on smoking cessation.

    Science.gov (United States)

    van den Putte, Bas; Yzer, Marco; Southwell, Brian G; de Bruijn, Gert-Jan; Willemsen, Marc C

    2011-05-01

    In the context of health campaigns, interpersonal communication can serve at least 2 functions: (a) to stimulate change through social interaction and (b) in a secondary diffusion process, to further disseminate message content. In a 3-wave prospective study of 1,079 smokers, the authors demonstrate that mass media messages (antismoking campaigns and news coverage relevant to smoking cessation) have an indirect effect on smoking cessation intention and behavior via interpersonal communication. Exposure to campaigns and news coverage prompts discussion about the campaigns, and, in turn, about smoking cessation. Interpersonal communication regarding smoking cessation then influences intention to quit smoking and attempts to quit smoking. The study finds evidence not only for the social interaction function of interpersonal communication, but also for the secondary diffusion function. A substantial number of smokers who are not directly exposed to the antismoking campaigns are nevertheless indirectly exposed via communication with people who have seen these campaigns. These results imply that encouragement of interpersonal communication can be an important campaign objective. PMID:21337250

  11. Electro-Weak Dark Matter: Non-perturbative effect confronting indirect detections

    Directory of Open Access Journals (Sweden)

    Eung Jin Chun

    2015-11-01

    Full Text Available We update indirect constraints on Electro-Weak Dark Matter (EWDM considering the Sommerfeld–Ramsauer–Townsend (SRT effect for its annihilations into a pair of standard model gauge bosons assuming that EWDM accounts for the observed dark matter (DM relic density for a given DM mass and mass gaps among the multiplet components. For the radiative or smaller mass splitting, the hypercharged triplet and higher multiplet EWDMs are ruled out up to the DM mass ≈10–20 TeV by the combination of the most recent data from AMS-02 (antiproton, Fermi-LAT (gamma-ray, and HESS (gamma-line. The Majorana triplet (wino-like EWDM can evade all the indirect constraints only around Ramsauer–Townsend dips which can occur for a tiny mass splitting of order 10 MeV or less. In the case of the doublet (Higgsino-like EWDM, a wide range of its mass ≳500 GeV is allowed except Sommerfeld peak regions. Such a stringent limit on the triplet DM can be evaded by employing a larger mass gap of the order of 10 GeV which allows its mass larger than about 1 TeV. However, the future CTA experiment will be able to cover most of the unconstrained parameter space.

  12. Comparison of direct and indirect measurement of the elastocaloric effect in natural rubber

    Science.gov (United States)

    Xie, Zhongjian; Sebald, Gael; Guyomar, Daniel

    2016-01-01

    The directly measured temperature change Δ T upon deformation (elastocaloric effect) of natural rubber was compared with indirect method, which is deduced from the Clausius-Clapeyron factor ( ∂ σ / ∂ T ) ɛ , where σ is the stress and ɛ is the strain. The factor ( ∂ σ / ∂ T ) ɛ can be measured by two different methods. One is to measure the stress vs. strain behavior at different static temperatures. It is found that the Δ T deduction is underestimated or even of opposite sign compared with the directly measured one. These behaviors are different from elastocaloric effect of shape memory alloys. An interpretation based on strain-induced crystallite is proposed. The other characterization is to measure the stress vs. temperature at constant strain. It results in a prediction, which is in good quantitative agreement with the directly measured one. The stress appears then to be a non-state variable, thus questioning the ergodicity of the material.

  13. Longitudinal Pathways from Marital Hostility to Child Anger During Toddlerhood: Genetic Susceptibility and Indirect Effects via Harsh Parenting

    OpenAIRE

    Rhoades, Kimberly A.; Leve, Leslie D.; Harold, Gordon T.; Neiderhiser, Jenae M.; Shaw, Daniel S.; Reiss, David

    2011-01-01

    We examined direct and indirect pathways from marital hostility to toddler anger/frustration via harsh parenting and parental depressive symptoms, with an additional focus on the moderating role of genetic influences as inferred from birth parent anger/frustration. Participants were 361 linked triads of birth mothers, adoptive parents, and adopted children who were 9 (T1) and 18 (T2) months old across the study period. Results indicated an indirect effect from T1 marital hostility to T2 toddl...

  14. The relative clinical effectiveness of ranibizumab and bevacizumab in diabetic macular oedema: an indirect comparison in a systematic review

    OpenAIRE

    Ford, John A; Elders, Andrew; Shyangdan, Deepson; Royle, Pamela; Waugh, Norman

    2012-01-01

    Objective To indirectly compare the effectiveness of ranibizumab and bevacizumab in the treatment of diabetic macular oedema. Design Systematic review and indirect comparison. Data sources Medline (1996–September 2011), Embase (1996–September 2011), and the Cochrane Central Register of Controlled Trials (Issue 4, 2011). Selection criteria for studies Randomised trials evaluating ranibizumab or bevacizumab in diabetic macular oedema with a common comparator and sufficient methodological simila...

  15. Organic photolysis reactions in tropospheric aerosols: effect on secondary organic aerosol formation and lifetime

    Directory of Open Access Journals (Sweden)

    A. Hodzic

    2015-03-01

    Full Text Available This study presents the first modeling estimates of the potential effect of gas- and particle-phase organic photolysis reactions on the formation and lifetime of secondary organic aerosols (SOA. Typically only photolysis of smaller organic molecules (e.g. formaldehyde for which explicit data exist is included in chemistry-climate models. Here, we specifically examine the photolysis of larger molecules that actively partition between the gas and particle phases. The chemical mechanism generator GECKO-A is used to explicitly model SOA formation from α-pinene, toluene, and C12 and C16 n-alkane reactions with OH at low- and high-NOx. Simulations are conducted for typical mid-latitude conditions and a solar zenith angle of 45° (permanent daylight. The results show that after four days of chemical aging under those conditions (equivalent to eight days in the summer mid-latitudes, gas-phase photolysis leads to a moderate decrease in SOA yields i.e ~15% (low-NOx to ~45% (high-NOx for α-pinene, ~15% for toluene, ~25% for C12-alkane, and ~10% for C16-alkane. The small effect on low volatility n-alkanes such as C16-alkane is due to the rapid partitioning of early-generation products to the particle phase where they are assumed to be protected from gas-phase photolysis. Minor changes are found in the volatility distribution of organic products and in oxygen to carbon ratios. The decrease in SOA mass seems increasingly more important after a day of chemical processing, suggesting that most laboratory experiments are likely too short to quantify the effect of gas-phase photolysis on SOA yields. Our results also suggest that many molecules containing chromophores are preferentially partitioned into the particle phase before they can be photolyzed in the gas-phase. Given the growing experimental evidence that these molecules can undergo in-particle photolysis, we performed sensitivity simulations using an estimated SOA photolysis rate of JSOA=4 x 10-4JNO2

  16. Organic photolysis reactions in tropospheric aerosols: effect on secondary organic aerosol formation and lifetime

    Science.gov (United States)

    Hodzic, A.; Madronich, S.; Kasibhatla, P. S.; Tyndall, G.; Aumont, B.; Jimenez, J. L.; Lee-Taylor, J.; Orlando, J.

    2015-08-01

    This study presents the first modeling estimates of the potential effect of gas- and particle-phase organic photolysis reactions on the formation and lifetime of secondary organic aerosols (SOAs). Typically only photolysis of smaller organic molecules (e.g., formaldehyde) for which explicit data exist is included in chemistry-climate models. Here, we specifically examine the photolysis of larger molecules that actively partition between the gas and particle phases. The chemical mechanism generator GECKO-A is used to explicitly model SOA formation from α-pinene, toluene, and C12 and C16 n-alkane reactions with OH at low and high NOx. Simulations are conducted for typical mid-latitude conditions and a solar zenith angle of 45° (permanent daylight). The results show that after 4 days of chemical aging under those conditions (equivalent to 8 days in the summer mid-latitudes), gas-phase photolysis leads to a moderate decrease in SOA yields, i.e., ~15 % (low NOx) to ~45 % (high NOx) for α-pinene, ~15 % for toluene, ~25 % for C12 n-alkane, and ~10 % for C16 n-alkane. The small effect of gas-phase photolysis on low-volatility n-alkanes such as C16 n-alkane is due to the rapid partitioning of early-generation products to the particle phase, where they are protected from gas-phase photolysis. Minor changes are found in the volatility distribution of organic products and in oxygen to carbon ratios. The decrease in SOA mass is increasingly more important after a day of chemical processing, suggesting that most laboratory experiments are likely too short to quantify the effect of gas-phase photolysis on SOA yields. Our results also suggest that many molecules containing chromophores are preferentially partitioned into the particle phase before they can be photolyzed in the gas phase. Given the growing experimental evidence that these molecules can undergo in-particle photolysis, we performed sensitivity simulations using an empirically estimated SOA photolysis rate of JSOA

  17. Histamine bronchial challenge: effect on regional ventilation and aerosol deposition.

    OpenAIRE

    Clague, H.; Ahmad, D.; Chamberlain, M. J.; Morgan, W K; Vinitski, S

    1983-01-01

    We studied regional changes in ventilation and aerosol deposition after histamine challenge in six patients with asthma and two with rhinitis and a history of wheezing. All were known to have bronchial hyperreactivity and all showed an increased response to histamine. Ventilation and aerosol deposition studies, using xenon-133 and an aerosol of sulphur colloid tagged with technetium 99m, were performed while they were sitting. Before administration of histamine radioaerosol scintiscans were a...

  18. Effects of aerosols on clear-sky solar radiation in the ALADIN-HIRLAM NWP system

    Science.gov (United States)

    Gleeson, Emily; Toll, Velle; Pagh Nielsen, Kristian; Rontu, Laura; Masek, Jan

    2016-05-01

    The direct shortwave radiative effect of aerosols under clear-sky conditions in the Aire Limitee Adaptation dynamique Developpement InterNational - High Resolution Limited Area Model (ALADIN-HIRLAM) numerical weather prediction system was investigated using three shortwave radiation schemes in diagnostic single-column experiments: the Integrated Forecast System (IFS), acraneb2 and the hlradia radiation schemes. The multi-band IFS scheme was formerly used operationally by the European Centre for Medium Range Weather Forecasts (ECMWF) whereas hlradia and acraneb2 are broadband schemes. The former is a new version of the HIRLAM radiation scheme while acraneb2 is the radiation scheme in the ALARO-1 physics package. The aim was to evaluate the strengths and weaknesses of the numerical weather prediction (NWP) system regarding aerosols and to prepare it for use of real-time aerosol information. The experiments were run with particular focus on the August 2010 Russian wildfire case. Each of the three radiation schemes accurately (within ±4 % at midday) simulates the direct shortwave aerosol effect when observed aerosol optical properties are used. When the aerosols were excluded from the simulations, errors of more than +15 % in global shortwave irradiance were found at midday, with the error reduced to +10 % when standard climatological aerosols were used. An error of -11 % was seen at midday if only observed aerosol optical depths at 550 nm, and not observation-based spectral dependence of aerosol optical depth, single scattering albedos and asymmetry factors, were included in the simulations. This demonstrates the importance of using the correct aerosol optical properties. The dependency of the direct radiative effect of aerosols on relative humidity was tested and shown to be within ±6 % in this case. By modifying the assumptions about the shape of the IFS climatological vertical aerosol profile, the inherent uncertainties associated with assuming fixed vertical

  19. Climatic response to anthropogenic sulphate aerosols versus well-mixed greenhouse gases from 1850 to 2000 AD in CLIMBER-2

    OpenAIRE

    Bauer, Eva; Petoukhov, Vladimir; Ganopolski, Andrey; Eliseev, Alexey V.

    2011-01-01

    The Earth system model CLIMBER-2 is extended by a scheme for calculating the climatic response to anthropogenic sulphur dioxide emissions. The scheme calculates the direct radiative forcing, the first indirect cloud albedo effect, and the second indirect cloud lifetime effect induced by geographically resolved sulphate aerosol burden. The simulated anthropogenic sulphate aerosol burden in the year 2000 amounts to 0.47 TgS. The best guesses for the radiative forcing due to the direct effect ar...

  20. Weekly periodicities of aerosol optical thickness over Central Europe – evidence of an anthropogenic direct aerosol effect

    Directory of Open Access Journals (Sweden)

    B. Vogel

    2007-08-01

    Full Text Available Statistical analyses of data from 14 ground-based sun photometer stations all over Central Europe are presented. All stations are part of the Aerosol Robotic Network (AERONET, and only data of the highest data quality level 2.0 had been applied. The averages by weekday of aerosol optical thickness (AOT at a wavelength of 440 nm of 12 of the 14 stations show a weekly periodicity with lowest values on Sunday and Monday, but greatest values from Wednesday until Saturday, that is significant at least on a 90% level. The stations in Germany and in Greater Paris show weekly cycles with ranges of about 20% on average. In Northern Italy and Switzerland this range is about 10% on average. The corresponding weekly cycle of anthropogenic gaseous and particulate emissions leads us to the conclusion of the anthropogenic origin of the weekly AOT cycle. Since these AOT patterns are derived from the reduction of the direct sun radiation by the columnar atmospheric aerosol, this result represents strong evidence for an anthropogenic direct aerosol effect on shortwave radiation. Furthermore, this study makes a first contribution to the understanding and explanation of recently observed weekly periodicities in meteorological variables as temperature in Germany.

  1. Aerosol chemical characterization and role of carbonaceous aerosol on radiative effect over Varanasi in central Indo-Gangetic Plain

    Science.gov (United States)

    Tiwari, S.; Dumka, U. C.; Kaskaoutis, D. G.; Ram, Kirpa; Panicker, A. S.; Srivastava, M. K.; Tiwari, Shani; Attri, S. D.; Soni, V. K.; Pandey, A. K.

    2016-01-01

    This study investigates the chemical composition of PM10 aerosols at Varanasi, in the central Indo-Gangetic Plain (IGP) during April to July 2011, with emphasis on examining the contribution of elemental carbon (EC) to the estimates of direct aerosol radiative effect (DARE). PM10 samples are analysed for carbonaceous aerosols (Organic Carbon, OC and EC) and water-soluble ionic species (WSIS: Cl-, SO42-, NO3-, PO42- NH4+, Na+, K+, Mg2+ and Ca2+) and several diagnostic ratios (OC/EC, K+/EC, etc) have been also used for studying the aerosol sources at Varanasi. PM10 mass concentration varies between 53 and 310 μg m-3 (mean of 168 ± 73 μg m-3), which is much higher than the National and International air quality standards. The OC mass concentration varies from 6 μg m-3 to 24 μg m-3 (mean of 12 ± 5 μg m-3; 7% of PM10 mass), whereas EC ranges between 1.0 and 14.3 μg m-3 (4.4 ± 3.9 μg m-3; ˜3% of PM10 mass). The relative low OC/EC of 3.9 ± 2.0 and strong correlation (R2 = 0.82) between them suggest the dominance of primary carbonaceous aerosols. The contribution of WSIS to PM10 is found to be ˜12%, out of which ˜57% and 43% are anions and cations, respectively. The composite DARE estimates via SBDART model reveal significant radiative effect and atmospheric heating rates (0.9-2.3 K day-1). Although the EC contributes only ˜3% to the PM10 mass, its contribution to the surface and atmospheric forcing is significantly high (37-63% and 54-77%, respectively), thus playing a major role in climate implications over Varanasi.

  2. A Case Study of Urbanization Impact on Summer Precipitation in the Greater Beijing Metropolitan Area. Urban Heat Island Versus Aerosol Effects

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Shi [Nanjing Univ. (China); Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qian, Yun [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhao, Chun [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Leung, Lai-Yung R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Yang, Xiuqun [Nanjing Univ. (China)

    2015-10-23

    Convection-resolving ensemble simulations using the WRF-Chem model coupled with a single-layer Urban Canopy Model (UCM) are conducted to investigate the individual and combined impacts of land use and anthropogenic pollutant emissions from urbanization on a heavy rainfall event in the Greater Beijing Metropolitan Area (GBMA) in China. The simulation with the urbanization effect included generally captures the spatial pattern and temporal variation of the rainfall event. An improvement of precipitation is found in the experiment including aerosol effect on both clouds and radiation. The expanded urban land cover and increased aerosols have an opposite effect on precipitation processes, with the latter playing a more dominant role, leading to suppressed convection and rainfall over the upstream (northwest) area, and enhanced convection and more precipitation in the downstream (southeast) region of the GBMA. In addition, the influence of aerosol indirect effect is found to overwhelm that of direct effect on precipitation in this rainfall event. Increased aerosols induce more cloud droplets with smaller size, which favors evaporative cooling and reduce updrafts and suppress convection over the upstream (northwest) region in the early stage of the rainfall event. As the rainfall system propagates southeastward, more latent heat is released due to the freezing of larger number of smaller cloud drops that are lofted above the freezing level, which is responsible for the increased updraft strength and convective invigoration over the downstream (southeast) area.

  3. Direct and indirect effects of the glyphosate formulation Glifosato Atanor® on freshwater microbial communities.

    Science.gov (United States)

    Vera, María Solange; Di Fiori, Eugenia; Lagomarsino, Leonardo; Sinistro, Rodrigo; Escaray, Roberto; Iummato, María Mercedes; Juárez, Angela; Ríos de Molina, María del Carmen; Tell, Guillermo; Pizarro, Haydée

    2012-10-01

    Glyphosate-based formulations are among the most widely used herbicides in the world. The effect of the formulation Glifosato Atanor(®) on freshwater microbial communities (phytoplankton, bacterioplankton, periphyton and zooplankton) was assessed through a manipulative experiment using six small outdoor microcosms of small volume. Three of the microcosms were added with 3.5 mg l(-1) of glyphosate whereas the other three were left as controls without the herbicide. The treated microcosms showed a significant increase in total phosphorus, not fully explained by the glyphosate present in the Glifosato Atanor(®). Therefore, part of the phosphorus should have come from the surfactants of the formulation. The results showed significant direct and indirect effects of Glifosato Atanor(®) on the microbial communities. A single application of the herbicide caused a fast increase both in the abundance of bacterioplankton and planktonic picocyanobacteria and in chlorophyll a concentration in the water column. Although metabolic alterations related to oxidative stress were induced in the periphyton community, the herbicide favored its development, with a large contribution of filamentous algae typical of nutrient-rich systems, with shallow and calm waters. An indirect effect of the herbicide on the zooplankton was observed due to the increase in the abundance of the rotifer Lecane spp. as a consequence of the improved food availability given by picocyanobacteria and bacteria. The formulation affected directly a fraction of copepods as a target. It was concluded that the Glifosato Atanor(®) accelerates the deterioration of the water quality, especially when considering small-volume water systems. PMID:22539117

  4. Effects of Aerosol on Atmospheric Dynamics and Hydrologic Processes During Boreal Spring and Summer

    Science.gov (United States)

    Lau, William K. M.; Kim, M. K.; Kim, K. M.; Chin, Mian

    2005-01-01

    Global and regional climate impacts of present-day aerosol loading during boreal spring are investigated using the NASA finite volume General Circulation Model (fvGCM). Three-dimensional distributions of loadings of five species of tropospheric aerosols, i.e., sulfate, black carbon, organic carbon, soil dust, and sea salt are prescribed from outputs of the Goddard Ozone Chemistry Aerosol Radiation and Transport model (GOCART). The aerosol loadings are used to calculate the extinction coefficient, single scattering albedo, and asymmetric factor at eleven spectral wavelengths in the radiative transfer code. We find that aerosol-radiative forcing during boreal spring excites a wavetrain-like pattern in tropospheric temperature and geopotential height that emanates from Northern Africa, through Eurasia, to northeastern Pacific. Associated with the teleconnection is strong surface cooling over regions with large aerosol loading, i.e., China, India, and Africa. Low-to-mid tropospheric heating due to shortwave absorption is found in regions with large loading of dust (Northern Africa, and central East Asia), and black carbon (South and East Asia). In addition pronounced surface cooling is found over the Caspian Sea and warming over Eurasian and northeastern Asia, where aerosol loadings are relatively low. These warming and cooling are components of teleconnection pattern produced primarily by atmospheric heating from absorbing aerosols, i.e., dust from North Africa and black carbon from South and East Asia. Effects of aerosols on atmospheric hydrologic cycle in the Asian monsoon region are also investigated. Results show that absorbing aerosols, i.e., black carbon and dust, induce large-scale upper-level heating anomaly over the Tibetan Plateau in April and May, ushering in an early onset of the Indian summer monsoon. Absorbing aerosols also enhance lower-level heating and anomalous ascent over northern India, intensifying the Indian monsoon. Overall, the aerosol

  5. The Invigoration of Deep Convective Clouds Over the Atlantic: Aerosol Effect, Meteorology or Retrieval Artifact?

    Science.gov (United States)

    Koren, Ilan; Feingold, Graham; Remer, Lorraine A.

    2010-01-01

    Associations between cloud properties and aerosol loading are frequently observed in products derived from satellite measurements. These observed trends between clouds and aerosol optical depth suggest aerosol modification of cloud dynamics, yet there are uncertainties involved in satellite retrievals that have the potential to lead to incorrect conclusions. Two of the most challenging problems are addressed here: the potential for retrieved aerosol optical depth to be cloud-contaminated, and as a result, artificially correlated with cloud parameters; and the potential for correlations between aerosol and cloud parameters to be erroneously considered to be causal. Here these issues are tackled directly by studying the effects of the aerosol on convective clouds in the tropical Atlantic Ocean using satellite remote sensing, a chemical transport model, and a reanalysis of meteorological fields. Results show that there is a robust positive correlation between cloud fraction or cloud top height and the aerosol optical depth, regardless of whether a stringent filtering of aerosol measurements in the vicinity of clouds is applied, or not. These same positive correlations emerge when replacing the observed aerosol field with that derived from a chemical transport model. Model-reanalysis data is used to address the causality question by providing meteorological context for the satellite observations. A correlation exercise between the full suite of meteorological fields derived from model reanalysis and satellite-derived cloud fields shows that observed cloud top height and cloud fraction correlate best with model pressure updraft velocity and relative humidity. Observed aerosol optical depth does correlate with meteorological parameters but usually different parameters from those that correlate with observed cloud fields. The result is a near-orthogonal influence of aerosol and meteorological fields on cloud top height and cloud fraction. The results strengthen the case

  6. The invigoration of deep convective clouds over the Atlantic: aerosol effect, meteorology or retrieval artifact?

    Directory of Open Access Journals (Sweden)

    I. Koren

    2010-09-01

    Full Text Available Associations between cloud properties and aerosol loading are frequently observed in products derived from satellite measurements. These observed trends between clouds and aerosol optical depth suggest aerosol modification of cloud dynamics, yet there are uncertainties involved in satellite retrievals that have the potential to lead to incorrect conclusions. Two of the most challenging problems are addressed here: the potential for retrieved aerosol optical depth to be cloud-contaminated, and as a result, artificially correlated with cloud parameters; and the potential for correlations between aerosol and cloud parameters to be erroneously considered to be causal. Here these issues are tackled directly by studying the effects of the aerosol on convective clouds in the tropical Atlantic Ocean using satellite remote sensing, a chemical transport model, and a reanalysis of meteorological fields. Results show that there is a robust positive correlation between cloud fraction or cloud top height and the aerosol optical depth, regardless of whether a stringent filtering of aerosol measurements in the vicinity of clouds is applied, or not. These same positive correlations emerge when replacing the observed aerosol field with that derived from a chemical transport model. Model-reanalysis data is used to address the causality question by providing meteorological context for the satellite observations. A correlation exercise between the full suite of meteorological fields derived from model reanalysis and satellite-derived cloud fields shows that observed cloud top height and cloud fraction correlate best with model pressure updraft velocity and relative humidity. Observed aerosol optical depth does correlate with meteorological parameters but usually different parameters from those that correlate with observed cloud fields. The result is a near-orthogonal influence of aerosol and meteorological fields on cloud top height and cloud fraction. The results

  7. Assessing the Effects of Anthropogenic Aerosols on Pacific Storm Track Using a Multiscale Global Climate Model

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yuan; Wang, Minghuai; Zhang, Renyi; Ghan, Steven J.; Lin, Yun; Hu, Jiaxi; Pan, Bowen; Levy, Misti; Jiang, Jonathan; Molina, Mario J.

    2014-05-13

    Atmospheric aerosols impact weather and global general circulation by modifying cloud and precipitation processes, but the magnitude of cloud adjustment by aerosols remains poorly quantified and represents the largest uncertainty in estimated forcing of climate change. Here we assess the impacts of anthropogenic aerosols on the Pacific storm track using a multi-scale global aerosol-climate model (GCM). Simulations of two aerosol scenarios corresponding to the present day and pre-industrial conditions reveal long-range transport of anthropogenic aerosols across the north Pacific and large resulting changes in the aerosol optical depth, cloud droplet number concentration, and cloud and ice water paths. Shortwave and longwave cloud radiative forcing at the top of atmosphere are changed by - 2.5 and + 1.3 W m-2, respectively, by emission changes from pre-industrial to present day, and an increased cloud-top height indicates invigorated mid-latitude cyclones. The overall increased precipitation and poleward heat transport reflect intensification of the Pacific storm track by anthropogenic aerosols. Hence, this work provides for the first time a global perspective of the impacts of Asian pollution outflows from GCMs. Furthermore, our results suggest that the multi-scale modeling framework is essential in producing the aerosol invigoration effect of deep convective clouds on the global scale.

  8. The invigoration of deep convective clouds over the Atlantic: aerosol effect, meteorology or retrieval artifact?

    Directory of Open Access Journals (Sweden)

    I. Koren

    2010-02-01

    Full Text Available The effects of the aerosol on convective clouds in the tropical Atlantic Ocean are explored using satellite remote sensing, a chemical transport model, and a reanalysis of meteorological fields. Two of the most challenging problems are addressed: the potential for elements of the cloud field to be erroneously ascribed to aerosol optical depth; and the potential for correlations between aerosol and cloud parameters to be erroneously considered to be causal. Results show that there is a robust positive correlation between cloud fraction or cloud top height and the aerosol optical depth, regardless of whether a stringent filtering of aerosol measurements in the vicinity of clouds is applied, or not. These same positive correlations emerge when replacing the observed aerosol field with that derived from a chemical transport model. A correlation exercise between the full suite of meteorological fields derived from model reanalysis and satellite-derived cloud fields shows that observed cloud top height and cloud fraction correlate best with pressure updraft velocity and relative humidity. Observed aerosol optical depth does correlate with meteorological parameters but usually different parameters from those that correlate with observed cloud fields. The result is a near-orthogonal influence of aerosol and meteorological fields on cloud top height and cloud fraction. The results strengthen the case that the aerosol does play a role in invigorating convective clouds.

  9. Ocean Emission Effects on Aerosol-Cloud Interactions: Insights from Two Case Studies

    Directory of Open Access Journals (Sweden)

    Armin Sorooshian

    2010-01-01

    Full Text Available Two case studies are discussed that evaluate the effect of ocean emissions on aerosol-cloud interactions. A review of the first case study from the eastern Pacific Ocean shows that simultaneous aircraft and space-borne observations are valuable in detecting links between ocean biota emissions and marine aerosols, but that the effect of the former on cloud microphysics is less clear owing to interference from background anthropogenic pollution and the difficulty with field experiments in obtaining a wide range of aerosol conditions to robustly quantify ocean effects on aerosol-cloud interactions. To address these limitations, a second case was investigated using remote sensing data over the less polluted Southern Ocean region. The results indicate that cloud drop size is reduced more for a fixed increase in aerosol particles during periods of higher ocean chlorophyll A. Potential biases in the results owing to statistical issues in the data analysis are discussed.

  10. Estimation of the Treatment Effects of Ownership on the Indirect Financing of Small- and Medium-Sized Enterprises

    Directory of Open Access Journals (Sweden)

    Xiuzhen Wang

    2014-01-01

    Full Text Available Small- and medium-sized enterprises (SMEs are the important driving forces for the growth of China’s economy. However, financing difficulty has always been the important problem besetting the development of SMEs for a long time. In particular, in recent years, US subprime crisis in 2008 caused a heavy blow to the development of some externally oriented SMEs. Thus, how to effectively overcome financing predicament for the SMEs is crucial for Chinese government. In this paper, based on microdata from China Industrial Enterprise Database, propensity score matching (PSM method is adopted to conduct empirical analysis about the treatment effects of indirect financing level of SMEs under different systems. Empirical results reveal that state-owned enterprises enjoy indirect financing advantages compared with other enterprises and there is certain ownership discrimination against foreign-funded enterprises and private enterprises. In particular, the indirect financing rate of state-owned enterprises is 1.4% higher than that of other enterprises, and the indirect financing rate of foreign-funded enterprises is 6% lower than that of other enterprises; private enterprises are advantageous in indirect financing compared with other enterprises; however, indirect financing rate of private enterprises is 1.8% lower than that of state-owned enterprises, which also reveals ownership discrimination to certain extent.

  11. Atmospheric impact of the 1783A~é 1784 Laki Eruption: Part II Climatic effect of sulphate aerosol

    Science.gov (United States)

    Highwood, E.-J.; Stevenson, D. S.

    2003-08-01

    The long 1783-1784 eruption of Laki in southern Iceland, was one of the first eruptions to have been linked to an observed climate anomaly, having been held responsible for cold temperatures over much of the Northern Hemisphere in the period 1783-1785. Results from the first climate model simulation of the impact of a similar eruption to that of 1783-1784 are presented. Using sulphate aerosol fields produced in a companion chemical transport model simulation by Stevenson et al. (2003), the radiative forcing and climate response due to the aerosol are calculated here using the Reading Intermediate General Circulation Model (IGCM). The peak Northern Hemisphere mean direct radiative forcing is -5.5 Wm-2 in August 1783. The radiative forcing dies away quickly as the emissions from the volcano decrease; however, a small forcing remains over the Mediterranean until March 1784. There is little forcing in the Southern Hemisphere. There is shown to be an uncertainty of at least 50% in the direct radiative forcing due to assumptions concerning relative humidity and the sophistication of the radiative transfer code used. The indirect effects of the Laki aerosol are potentially large but essentially unquantifiable at the present time. In the IGCM at least, the aerosol from the eruption produces a climate response that is spatially very variable. The Northern Hemisphere mean temperature anomaly averaged over the whole of the calendar year containing most of the eruption is -0.21 K, statistically significant at the 95% level and in reasonable agreement with the available observations of the temperature during 1783.

  12. Direct and indirect antimicrobial effects of α-mangostin on pathogenic microorganisms

    Institute of Scientific and Technical Information of China (English)

    Nurul Huda Syed Ibrahim; Muhammad Taher; Deny Susanti; Qamar Uddin Ahmed

    2014-01-01

    Objective: To test direct and indirect antimicrobial properties of α-mangostin towards a number of bacteria and fungi.Methods:Activity of α-mangostin paired with an antibiotic was studied by calculating its fractional inhibitory concentration (FIC).Results:The experiment was carried out using broth microdilution and checkerboards methods. tetracycline showed no interaction with the combination with α-mangostin where the FIC indexes were between the range of 0.54. Activity of doxycycline on Pseudomonas aeruginosa fell into other set of range, FICindex≥4 which is an antagonism. The activity of all four bacteria towards ampicillin, penicillin G, streptomycin and Conclusions: The FIC index is far away in the range. The coupled antibiotic and α-mangostin is considered synergy in action if it lies in FICindex≤0.5 and it was found that the isolated compound,α-mangostin revealed very low synergistic antimicrobial effects when coupled with antibiotics.

  13. COATING AND MANDREL EFFECTS ON FABRICATION OF GLOW DISCHARGE POLYMER NIF SCALE INDIRECT DRIVE CAPSULES

    International Nuclear Information System (INIS)

    OAK A271 COATING AND MANDREL EFFECTS ON FABRICATION OF GLOW DISCHARGE POLYMER NIF SCALE INDIRECT DRIVE CAPSULES. Targets for the National Ignition Facility (NIF) need to be about 200 (micro)m thick and 2 mm in diameter. These dimensions are well beyond those currently fabricated on a routine basis. They have investigated fabrication of near NIF scale targets using the depolymerizable mandrel technique. Poly-alpha-methylstyrene (PAMS) mandrels, about 2 mm in diameter, of varying qualities were coated with as much as 125 (micro)m of glow discharge polymer (GDP). The surface finish of the final shells was examined using a variety of techniques. A clear dependence of the modal spectrum of final GDP shell on the quality of the initial PAMS mandrels was observed. isolated features were found to be the greatest cause for a shell not meeting the NIF standard

  14. Indirect effects of overfishing on Caribbean reefs: sponges overgrow reef-building corals

    Directory of Open Access Journals (Sweden)

    Tse-Lynn Loh

    2015-04-01

    Full Text Available Consumer-mediated indirect effects at the community level are difficult to demonstrate empirically. Here, we show an explicit indirect effect of overfishing on competition between sponges and reef-building corals from surveys of 69 sites across the Caribbean. Leveraging the large-scale, long-term removal of sponge predators, we selected overfished sites where intensive methods, primarily fish-trapping, have been employed for decades or more, and compared them to sites in remote or marine protected areas (MPAs with variable levels of enforcement. Sponge-eating fishes (angelfishes and parrotfishes were counted at each site, and the benthos surveyed, with coral colonies scored for interaction with sponges. Overfished sites had >3 fold more overgrowth of corals by sponges, and mean coral contact with sponges was 25.6%, compared with 12.0% at less-fished sites. Greater contact with corals by sponges at overfished sites was mostly by sponge species palatable to sponge predators. Palatable species have faster rates of growth or reproduction than defended sponge species, which instead make metabolically expensive chemical defenses. These results validate the top-down conceptual model of sponge community ecology for Caribbean reefs, as well as provide an unambiguous justification for MPAs to protect threatened reef-building corals. An unanticipated outcome of the benthic survey component of this study was that overfished sites had lower mean macroalgal cover (23.1% vs. 38.1% for less-fished sites, a result that is contrary to prevailing assumptions about seaweed control by herbivorous fishes. Because we did not quantify herbivores for this study, we interpret this result with caution, but suggest that additional large-scale studies comparing intensively overfished and MPA sites are warranted to examine the relative impacts of herbivorous fishes and urchins on Caribbean reefs.

  15. Does personality influence eating styles and food choices? Direct and indirect effects.

    Science.gov (United States)

    Keller, Carmen; Siegrist, Michael

    2015-01-01

    In a random sample (N = 951) from the general population, direct and indirect effects of the Big Five personality traits on eating styles and food choices were examined. Path models revealed that high openness to experience were associated with higher fruit, vegetable and salad and lower meat and soft drink consumption. High agreeableness was associated with low meat consumption. Neuroticism, conscientiousness and extraversion significantly and directly influenced eating styles and significantly indirectly influenced food choices. Conscientiousness mainly promoted fruit consumption by promoting restrained eating and prevented meat consumption by reducing external eating. Conscientiousness prevented consumption of sweet and savory foods, and of sugar-sweetened soft drinks by promoting restrained eating and reducing external eating, and consumption of sweet and savory foods also by reducing emotional eating. Neuroticism promoted consumption of sweet and savory foods by promoting emotional and external eating. Extraversion promoted sweet and savory, meat and soft drink consumption via promoting external eating. Results suggest that neurotic and emotionally unstable individuals seem to adopt counter-regulatory external or emotional eating and eat high-energy dense sweet and savory foods. Highly conscientious individuals adopt regulatory dietary restraint and practice counter-regulatory emotional or external eating less, resulting in more consumption of recommended and less consumption of not recommended food. The higher sociability of extraverted people, which is basically a health beneficial psychological resource, seems to have health-averse effects. Personality traits are stable; however, the resulting more proximal, counter-regulatory eating styles such as emotional or external eating might be more successfully addressed in interventions to prevent overeating and overweight. PMID:25308432

  16. Indirect effects of overfishing on Caribbean reefs: sponges overgrow reef-building corals.

    Science.gov (United States)

    Loh, Tse-Lynn; McMurray, Steven E; Henkel, Timothy P; Vicente, Jan; Pawlik, Joseph R

    2015-01-01

    Consumer-mediated indirect effects at the community level are difficult to demonstrate empirically. Here, we show an explicit indirect effect of overfishing on competition between sponges and reef-building corals from surveys of 69 sites across the Caribbean. Leveraging the large-scale, long-term removal of sponge predators, we selected overfished sites where intensive methods, primarily fish-trapping, have been employed for decades or more, and compared them to sites in remote or marine protected areas (MPAs) with variable levels of enforcement. Sponge-eating fishes (angelfishes and parrotfishes) were counted at each site, and the benthos surveyed, with coral colonies scored for interaction with sponges. Overfished sites had >3 fold more overgrowth of corals by sponges, and mean coral contact with sponges was 25.6%, compared with 12.0% at less-fished sites. Greater contact with corals by sponges at overfished sites was mostly by sponge species palatable to sponge predators. Palatable species have faster rates of growth or reproduction than defended sponge species, which instead make metabolically expensive chemical defenses. These results validate the top-down conceptual model of sponge community ecology for Caribbean reefs, as well as provide an unambiguous justification for MPAs to protect threatened reef-building corals. An unanticipated outcome of the benthic survey component of this study was that overfished sites had lower mean macroalgal cover (23.1% vs. 38.1% for less-fished sites), a result that is contrary to prevailing assumptions about seaweed control by herbivorous fishes. Because we did not quantify herbivores for this study, we interpret this result with caution, but suggest that additional large-scale studies comparing intensively overfished and MPA sites are warranted to examine the relative impacts of herbivorous fishes and urchins on Caribbean reefs. PMID:25945305

  17. Indirection and computer security.

    Energy Technology Data Exchange (ETDEWEB)

    Berg, Michael J.

    2011-09-01

    The discipline of computer science is built on indirection. David Wheeler famously said, 'All problems in computer science can be solved by another layer of indirection. But that usually will create another problem'. We propose that every computer security vulnerability is yet another problem created by the indirections in system designs and that focusing on the indirections involved is a better way to design, evaluate, and compare security solutions. We are not proposing that indirection be avoided when solving problems, but that understanding the relationships between indirections and vulnerabilities is key to securing computer systems. Using this perspective, we analyze common vulnerabilities that plague our computer systems, consider the effectiveness of currently available security solutions, and propose several new security solutions.

  18. Effects of aerosols on solar radiation in the ALADIN-HIRLAM NWP system

    Science.gov (United States)

    Gleeson, E.; Toll, V.; Nielsen, K. P.; Rontu, L.; Mašek, J.

    2015-11-01

    The direct shortwave radiative effect of aerosols in the ALADIN-HIRLAM numerical weather prediction system was investigated using three different shortwave radiation schemes in diagnostic single-column experiments. The aim was to evaluate the strengths and weaknesses of the model in this regard and to prepare the model for eventual use of real-time aerosol information. Experiments were run using observed, climatologically-averaged and zero aerosols, with particular focus on the August 2010 Russian wildfire case. One of these schemes is a revised version of the HLRADIA scheme with improved treatment of aerosols. Each radiation scheme accurately simulates the direct shortwave effect when observed aerosol optical properties are used rather than climatological-averages or no aerosols which result in large errors, particularly for heavy pollution scenarios. The dependencies of the direct radiative effect of aerosols on relative humidity and the vertical profile of the aerosols on the shortwave heating rates were also investigated and shown to be non-negligible.

  19. Boar taint in entire male pigs: A genomewide association study for direct and indirect genetic effects on androstenone.

    NARCIS (Netherlands)

    Duijvestein, N.; Knol, E.F.; Bijma, P.

    2014-01-01

    Androstenone is one of the compounds causing boar taint of pork and is highly heritable (approximately 0.6). Recently, indirect genetic effects (IGE; also known as associative effects or social genetic effects) were found for androstenone, meaning that pen mates (boars) affect each other’s androsten

  20. The relative importance of direct and indirect effects of hunting mortality on the population dynamics of brown bears.

    Science.gov (United States)

    Gosselin, Jacinthe; Zedrosser, Andreas; Swenson, Jon E; Pelletier, Fanie

    2015-01-01

    There is increasing evidence of indirect effects of hunting on populations. In species with sexually selected infanticide (SSI), hunting may decrease juvenile survival by increasing male turnover. We aimed to evaluate the relative importance of direct and indirect effects of hunting via SSI on the population dynamics of the Scandinavian brown bear (Ursus arctos). We performed prospective and retrospective demographic perturbation analyses for periods with low and high hunting pressures. All demographic rates, except yearling survival, were lower under high hunting pressure, which led to a decline in population growth under high hunting pressure (λ = 0.975; 95% CI = 0.914-1.011). Hunting had negative indirect effects on the population through an increase in SSI, which lowered cub survival and possibly also fecundity rates. Our study suggests that SSI could explain 13.6% of the variation in population growth. Hunting also affected the relative importance of survival and fecundity of adult females for population growth, with fecundity being more important under low hunting pressure and survival more important under high hunting pressure. Our study sheds light on the importance of direct and indirect effects of hunting on population dynamics, and supports the contention that hunting can have indirect negative effects on populations through SSI. PMID:25392469

  1. Climatic impacts of anthropogenic aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Iversen, T. [Oslo Univ. (Norway)

    1996-03-01

    This paper was read at the workshop ``The Norwegian Climate and Ozone Research Programme`` held on 11-12 March 1996. Anthropogenic production of aerosols is mainly connected with combustion of fossil fuel. Measured by particulate mass, the anthropogenic sulphate production is the dominating source of aerosols in the Northern Hemisphere. Particles emitted in mechanical processes, fly ash etc. are less important because of their shorter atmospheric residence time. Possible climatological effects of anthropogenic aerosols are usually classified in two groups: direct and indirect. Direct effects are alterations of the radiative heating budget due to the aerosol particles in clear air. Indirect effects involve the interaction between particles and cloud processes. A simplified one-layer radiation model gave cooling in the most polluted mid-latitude areas and heating due to soot absorption in the Arctic. This differential trend in heating rates may have significant effects on atmospheric meridional circulations, which is important for the atmosphere as a thermodynamic system. Recently the description of sulphur chemistry in the hemispheric scale dispersion model has been improved and will be used in a model for Mie scattering and absorption

  2. A case study of the radiative effect of aerosols over Europe: EUCAARI-LONGREX

    Science.gov (United States)

    Esteve, Anna R.; Highwood, Eleanor J.; Ryder, Claire L.

    2016-06-01

    The radiative effect of anthropogenic aerosols over Europe during the 2008 European Integrated Project on Aerosol Cloud Climate and Air Quality Interactions Long Range Experiment (EUCAARI-LONGREX) campaign has been calculated using measurements collected by the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft and radiative transfer modelling. The aircraft sampled anthropogenically perturbed air masses across north-western Europe under anticyclonic conditions with aerosol optical depths ranging from 0.047 to 0.357. For one specially designed "radiative closure" flight, simulated irradiances have been compared to radiation measurements for a case of aged European aerosol in order to explore the validity of model assumptions and the degree of radiative closure that can be attained given the spatial and temporal variability of the observations and their measurement uncertainties. Secondly, the diurnally averaged aerosol radiative effect throughout EUCAARI-LONGREX has been calculated. The surface radiative effect ranged between -3.9 and -22.8 W m-2 (mean -11 ± 5 W m-2), whilst top-of-the-atmosphere (TOA) values were between -2.1 and -12.0 W m-2 (mean -5 ± 3 W m-2). We have quantified the uncertainties in our calculations due to the way in which aerosols and other parameters are represented in a radiative transfer model. The largest uncertainty in the aerosol radiative effect at both the surface and the TOA comes from the spectral resolution of the information used in the radiative transfer model (˜ 17 %) and the aerosol description (composition and size distribution) used in the Mie calculations of the aerosol optical properties included in the radiative transfer model (˜ 7 %). The aerosol radiative effect at the TOA is also highly sensitive to the surface albedo (˜ 12 %).

  3. The effects of mineral dust particles, aerosol regeneration and ice nucleation parameterizations on clouds and precipitation

    Directory of Open Access Journals (Sweden)

    A. Teller

    2012-03-01

    Full Text Available This study focuses on the effects of aerosol particles on the formation of convective clouds and precipitation in the Eastern Mediterranean sea with a special emphasis on the role of mineral dust particles in these processes. We used a new detailed numerical cloud microphysics scheme that has been implemented in the Weather Research and Forecast (WRF model in order to study aerosol-cloud interaction in 3-D configuration based on realistic meteorological data. Using a number of case studies we tested the contribution of mineral dust particles and different ice nucleation parameterizations to precipitation development. In this study we also investigated the importance of recycled (regenerated aerosols that had been released to the atmosphere following the evaporation of cloud droplets.

    The results showed that increased aerosol concentration due to the presence of mineral dust enhanced the formation of ice crystals. The dynamic evolution of the cloud system sets the time periods and regions in which heavy or light precipitation occurred in the domain. The precipitation rate, the time and duration of precipitation were affected by the aerosol properties only at small area scales (with areas of about 20 km2. Changes of the ice nucleation scheme from ice supersaturation dependent parameterization to a recent approach of aerosol concentration and temperature dependent parameterization modified the ice crystals concentrations but did not affect the total precipitation in the domain. Aerosol regeneration modified the concentration of cloud droplets at cloud base by dynamic recirculation of the aerosols but also had only a minor effect on precipitation.

    The major conclusion from this study is that the effect of mineral dust particles on clouds and total precipitation is limited by the properties of the atmospheric dynamics and the only effect of aerosol on precipitation may come from significant increase in the concentration

  4. Influence of organic films on the evaporation and condensation of water in aerosol

    OpenAIRE

    Davies, James F.; Miles, Rachael E H; Haddrell, Allen E; Reid, Jonathan P.

    2013-01-01

    Uncertainties in quantifying the kinetics of evaporation and condensation of water fromatmospheric aerosol are a significant contributor to the uncertainty in predicting cloud droplet number and the indirect effect of aerosols on climate. The influence of aerosol particle surface composition, particularly the impact of surface active organic films, on the condensation and evaporation coefficients remains ambiguous. Here, we report measurements of the influence of organic films on the evaporat...

  5. Impacts of increasing the aerosol complexity in the Met Office global numerical weather prediction model

    OpenAIRE

    J. P. Mulcahy; Walters, D. N.; Bellouin, N.; S. F. Milton

    2014-01-01

    The inclusion of the direct and indirect radiative effects of aerosols in high-resolution global numerical weather prediction (NWP) models is being increasingly recognised as important for the improved accuracy of short-range weather forecasts. In this study the impacts of increasing the aerosol complexity in the global NWP configuration of the Met Office Unified Model (MetUM) are investigated. A hierarchy of aerosol representations are evaluated including three-dimensional...

  6. Aerosol Effects on Radiation and Climate: Column Closure Experiments with Towers, Aircraft, and Satellites

    Science.gov (United States)

    Russell, Philip B.

    1994-01-01

    Many theoretical studies have shown that anthropogenic aerosol particles can change the radiation balance in an atmospheric column and might thereby exert a significant effect on the Earth's climate. In particular, recent calculations have shown that sulfate particles from anthropogenic combustion may already exert a cooling influence on the Earth that partially offsets the warming caused by the greenhouse gases from the same combustion. Despite the potential climatic importance of anthropogenic aerosols, simultaneous measurements of anthropogenic aerosol properties and their effect on atmospheric radiation have been very rare. Successful comparisons of measured radiation fields with those calculated from aerosol measurements - now referred to as column closure comparisons - are required to improve the accuracy and credibility of climate predictions. This paper reviews the column closure experiment performed at the Mt. Sutro Tower in San Francisco in 1975, in which elevated radiometers measured the change in Earth-plus-atmosphere albedo caused by an aerosol layer, while a lidar, sunphotometer, nephelometer, and other radiometers measured properties of the responsible aerosol. The time-dependent albedo calculated from the measured aerosol properties agreed with that measured by the tower radiometers. Also presented are designs for future column closure studies using radiometers and aerosol instruments on the ground, aircraft, and satellites. These designs draw upon algorithms and experience developed in the Sutro Tower study, as well as more recent experience with current measurement and analysis capabilities.

  7. Life-Cycle Costing of Food Waste Management in Denmark: Importance of Indirect Effects.

    Science.gov (United States)

    Martinez-Sanchez, Veronica; Tonini, Davide; Møller, Flemming; Astrup, Thomas Fruergaard

    2016-04-19

    Prevention has been suggested as the preferred food waste management solution compared to alternatives such as conversion to animal fodder or to energy. In this study we used societal life-cycle costing, as a welfare economic assessment, and environmental life-cycle costing, as a financial assessment combined with life-cycle assessment, to evaluate food waste management. Both life-cycle costing assessments included direct and indirect effects. The latter are related to income effects, accounting for the marginal consumption induced when alternative scenarios lead to different household expenses, and the land-use-changes effect, associated with food production. The results highlighted that prevention, while providing the highest welfare gains as more services/goods could be consumed with the same income, could also incur the highest environmental impacts if the monetary savings from unpurchased food commodities were spent on goods/services with a more environmentally damaging production than that of the (prevented) food. This was not the case when savings were used, e.g., for health care, education, and insurances. This study demonstrates that income effects, although uncertain, should be included whenever alternative scenarios incur different financial costs. Furthermore, it highlights that food prevention measures should not only demote the purchase of unconsumed food but also promote a low-impact use of the savings generated. PMID:26978648

  8. Indirect genetic effects for growth rate in domestic pigs alter aggressive and manipulative biting behaviour.

    Science.gov (United States)

    Camerlink, Irene; Ursinus, Winanda W; Bijma, Piter; Kemp, Bas; Bolhuis, J Elizabeth

    2015-01-01

    Indirect genetic effects (IGEs) are heritable effects of an individual on phenotypic values of others, and may result from social interactions. We determined the behavioural consequences of selection for IGEs for growth (IGEg) in pigs in a G × E treatment design. Pigs (n = 480) were selected for high versus low IGEg with a contrast of 14 g average daily gain and were housed in either barren or straw-enriched pens (n = 80). High IGEg pigs showed from 8 to 23 weeks age 40% less aggressive biting (P = 0.006), 27% less ear biting (P = 0.03), and 40% less biting on enrichment material (P = 0.005). High IGEg pigs had a lower tail damage score (high 2.0; low 2.2; P = 0.004), and consumed 30 % less jute sacks (P = 0.002). Selection on high IGEg reduced biting behaviours additive to the, generally much larger, effects of straw-bedding (P biting behaviours in pigs. PMID:25227986

  9. The Direct and Indirect Effects of Parental Bonds, Parental Drug Use, and Self-Control on Adolescent Substance Use

    Science.gov (United States)

    Hope,Trina L.; Whiteford, Scott W.

    2005-01-01

    Research indicates that parenting has important effects on adolescent substance use. However, the indirect effect of parenting on adolescent substance use via self-control is less understood. Gottfredson and Hirschi's General Theory of Crime has been extensively tested by researchers in the field of criminology, but the theory rarely has been used…

  10. The genetics of maternal care: direct and indirect genetic effects on phenotype in the dung beetle Onthophagus taurus.

    Science.gov (United States)

    Hunt, John; Simmons, Leigh W

    2002-05-14

    While theoretical models of the evolution of parental care are based on the assumption of underlying genetic variance, surprisingly few quantitative genetic studies of this life-history trait exist. Estimation of the degree of genetic variance in parental care is important because it can be a significant source of maternal effects, which, if genetically based, represent indirect genetic effects. A major prediction of indirect genetic effect theory is that traits without heritable variation can evolve because of the heritable environmental variation that indirect genetic effects provide. In the dung beetle, Onthophagus taurus, females provide care to offspring by provisioning a brood mass. The size of the brood mass has pronounced effects on offspring phenotype. Using a half-sib breeding design we show that the weight of the brood mass females produce exhibits significant levels of additive genetic variance due to sires. However, variance caused by dams is considerably larger, demonstrating that maternal effects are also important. Body size exhibited low additive genetic variance. However, body size exerts a strong maternal influence on the weight of brood masses produced, accounting for 22% of the nongenetic variance in offspring body size. Maternal body size also influenced the number of offspring produced but there was no genetic variance for this trait. Offspring body size and brood mass weight exhibited positive genetic and phenotypic correlations. We conclude that both indirect genetic effects, via maternal care, and nongenetic maternal effects, via female size, play important roles in the evolution of phenotype in this species. PMID:11983863

  11. The Indirect Effect of Alcohol Use on GPA in First-Semester College Students: The Mediating Role of Academic Effort

    Science.gov (United States)

    Conway, James M.; DiPlacido, Joanne

    2015-01-01

    This study focused on first-semester college students, investigating (a) indirect effects of aggregate alcohol use on grade point average (GPA) through academic effort (skipping class and time on schoolwork) and (b) daily effects of alcohol use on reduced effort. Eighty students reported daily alcohol use and academic effort (skipping class and…

  12. Pneumococcal transmission and disease in silico: a microsimulation model of the indirect effects of vaccination.

    Directory of Open Access Journals (Sweden)

    Markku Nurhonen

    Full Text Available BACKGROUND: The degree and time frame of indirect effects of vaccination (serotype replacement and herd immunity are key determinants in assessing the net effectiveness of vaccination with pneumococcal conjugate vaccines (PCV in control of pneumococcal disease. Using modelling, we aimed to quantify these effects and their dependence on coverage of vaccination and the vaccine's efficacy against susceptibility to pneumococcal carriage. METHODS AND FINDINGS: We constructed an individual-based simulation model that explores the effects of large-scale PCV programmes and applied it in a developed country setting (Finland. A population structure with transmission of carriage taking place within relevant mixing groups (families, day care groups, schools and neighbourhoods was considered in order to properly assess the dependency of herd immunity on coverage of vaccination and vaccine efficacy against carriage. Issues regarding potential serotype replacement were addressed by employing a novel competition structure between multiple pneumococcal serotypes. Model parameters were calibrated from pre-vaccination data about the age-specific carriage prevalence and serotype distribution. The model predicts that elimination of vaccine-type carriage and disease among those vaccinated and, due to a substantial herd effect, also among the general population takes place within 5-10 years since the onset of a PCV programme with high (90% coverage of vaccination and moderate (50% vaccine efficacy against acquisition of carriage. A near-complete replacement of vaccine-type carriage by non-vaccine-type carriage occurs within the same time frame. CONCLUSIONS: The changed patterns in pneumococcal carriage after PCV vaccination predicted by the model are unequivocal. The overall effect on disease incidence depends crucially on the magnitude of age- and serotype-specific case-to-carrier ratios of the remaining serotypes relative to those of the vaccine types. Thus the

  13. Potential sensitivity of photosynthesis and isoprene emission to direct radiative effects of atmospheric aerosol pollution

    Science.gov (United States)

    Strada, S.; Unger, N.

    2015-09-01

    A global Earth system model is applied to quantify the impacts of direct anthropogenic aerosol effective radiative forcing on gross primary productivity (GPP) and isoprene emission. The impacts of different pollution aerosol sources (all anthropogenic, biomass burning and non-biomass burning) are investigated by performing sensitivity experiments. On the global scale, our results show that land carbon fluxes (GPP and isoprene emission) are not sensitive to pollution aerosols, even under a global decline in surface solar radiation (direct + diffuse) by ~ 9 %. At the regional scale, plant productivity (GPP) and isoprene emission show a robust but opposite sensitivity to pollution aerosols, in regions where complex canopies dominate. In eastern North America and Europe, anthropogenic pollution aerosols (mainly from non-biomass burning sources) enhance GPP by +8-12 % on an annual average, with a stronger increase during the growing season (> 12 %). In the Amazon basin and central Africa, biomass burning aerosols increase GPP by +2-5 % on an annual average, with a peak in the Amazon basin during the dry-fire season (+5-8 %). In Europe and China, anthropogenic pollution aerosols drive a decrease in isoprene emission of -2 to -12 % on the annual average. Anthropogenic aerosols affect land carbon fluxes via different mechanisms and we suggest that the dominant mechanism varies across regions: (1) light scattering dominates in the eastern US; (2) cooling in the Amazon basin; and (3) reduction in direct radiation in Europe and China.

  14. Effects of reactor core-simulant aerosols on hydrogen/air combustion

    International Nuclear Information System (INIS)

    Three representative reactor core-simulant aerosols were dispersed, just before ignition, into combustible hydrogen-air mixtures contained in 5.1 and 0.18 m3 chambers. Oxidic aerosols (Al2O3, Fe2O3) produced only minor changes in the burns. A metallic aerosol (Fe) ignited along with the hydrogen, producing more complete combustion of the hydrogen and substantially increased overpressures and thermal effects compared to control experiments performed identically without the aerosols. We attempted to use the rule of Le Chatelier to correlate flammability limits in the iron aerosol-hydrogen-air system determined in both experimental chambers. We showed that the rule does not apply well to hybrid mixtures such as these. We also showed that results obtained in small-scale apparatus may be misleading for metallic aerosols, where the flame thicknesses (approx.1 m) may be larger than the vessel dimensions. We recommend that large-scale apparatus be used whenever possible when studying lean flammability limits of either aerosols alone or hybrid aerosol-gas mixtures. 3 refs., 2 figs

  15. Climate response due to carbonaceous aerosols and aerosol-induced SST effects in NCAR community atmospheric model CAM3.5

    Directory of Open Access Journals (Sweden)

    W.-C. Hsieh

    2013-03-01

    Full Text Available This study used Community Atmospheric Model 3.5 (CAM3.5 to investigate the effects of carbonaceous aerosols on climate. The simulations include control runs with carbonaceous aerosols and no carbon runs in which carbonaceous aerosols were removed. The Slab Ocean Model (SOM and the fixed Sea Surface Temperature (SST were used to examine effects of ocean boundary conditions. Throughout this study, climate response induced by aerosol forcing was mainly analyzed in the following three terms: (1 aerosol radiative effects under fixed SST, (2 effects of aerosol-induced SST feedbacks , and (3 total effects including effects of aerosol forcing and SST feedbacks. The change of SST induced by aerosols has large impacts on distribution of climate response, the magnitudes in response patterns such as temperature, precipitation, zonal winds, mean meridional circulation, radiative fluxes and cloud coverage are different between the SOM and fixed SST runs. Moreover, different spatial responses between the SOM and fixed SST runs can also be seen in some local areas. This implies the importance of SST feedbacks on simulated climate response. The aerosol dimming effects cause a cooling predicted at low layers near the surface in most of carbonaceous aerosol source regions. The temperature response shows a warming (cooling predicted in the north (south high latitudes, suggesting that aerosol forcing can cause climate change in regions far away from its origins. Our simulation results show that warming of the troposphere due to black carbon decreases rainfall in the tropics. This implies that black carbon has possibly strong influence on weakening of the tropical circulation. Most of these changes in precipitation are negatively correlated with changes of radiative fluxes at the top of model. The changes in radiative fluxes at top of model are physically consistent with the response patterns in cloud fields. On global average, low-level cloud coverage increases, mid

  16. Role of clouds, aerosols, and aerosol-cloud interaction in 20th century simulations with GISS ModelE2

    Science.gov (United States)

    Nazarenko, L.; Rind, D. H.; Bauer, S.; Del Genio, A. D.

    2015-12-01

    Simulations of aerosols, clouds and their interaction contribute to the major source of uncertainty in predicting the changing Earth's energy and in estimating future climate. Anthropogenic contribution of aerosols affects the properties of clouds through aerosol indirect effects. Three different versions of NASA GISS global climate model are presented for simulation of the twentieth century climate change. All versions have fully interactive tracers of aerosols and chemistry in both the troposphere and stratosphere. All chemical species are simulated prognostically consistent with atmospheric physics in the model and the emissions of short-lived precursors [Shindell et al., 2006]. One version does not include the aerosol indirect effect on clouds. The other two versions include a parameterization of the interactive first indirect aerosol effect on clouds following Menon et al. [2010]. One of these two models has the Multiconfiguration Aerosol Tracker of Mixing state (MATRIX) that permits detailed treatment of aerosol mixing state, size, and aerosol-cloud activation. The main purpose of this study is evaluation of aerosol-clouds interactions and feedbacks, as well as cloud and aerosol radiative forcings, for the twentieth century climate under different assumptions and parameterizations for aerosol, clouds and their interactions in the climate models. The change of global surface air temperature based on linear trend ranges from +0.8°C to +1.2°C between 1850 and 2012. Water cloud optical thickness increases with increasing temperature in all versions with the largest increase in models with interactive indirect effect of aerosols on clouds, which leads to the total (shortwave and longwave) cloud radiative cooling trend at the top of the atmosphere. Menon, S., D. Koch, G. Beig, S. Sahu, J. Fasullo, and D. Orlikowski (2010), Black carbon aerosols and the third polar ice cap, Atmos. Chem. Phys., 10,4559-4571, doi:10.5194/acp-10-4559-2010. Shindell, D., G. Faluvegi

  17. Absorbing aerosol radiative effects in the limb-scatter viewing geometry

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    A. Wiacek

    2013-02-01

    Full Text Available The limb-scatter satellite viewing geometry is well suited to detecting low-concentration aerosols in the upper troposphere due to its long observation path length (~ 50–100 km, high vertical resolution (~ 1–2 km and good geographic coverage. We use the fully three-dimensional radiative transfer code SASKTRAN to simulate the sensitivity of limb-scatter viewing Odin/OSIRIS satellite measurements to absorbing mineral dust and carbonaceous aerosols (smoke and pure soot, as well as to non-absorbing sulfate aerosols and ice in the upper troposphere.

    At long wavelengths (813 nm the addition of all aerosols (except soot to an air only atmosphere produced a radiance increase as compared to air only, on account of the low Rayleigh scattering in air only at 813 nm. The radiance reduction due to soot aerosol was negligible (< 0.1% at all heights (0–100 km.

    At short wavelengths (337, 377, 452 nm, we found that the addition of any aerosol species to an air only atmosphere caused a decrease in single-scattered radiation due to an extinction of Rayleigh scattering in the direction of OSIRIS. The reduction was clearly related to particle size first, with absorption responsible for second-order effects only. Multiple-scattered radiation could either increase or decrease in the presence of an aerosol species, depending both on particle size and absorption. Large scatterers (ice, mineral dust all increased multiple-scattered radiation within, below and above the aerosol layer. Small, highly absorbing pure soot particles produced a negligible multiple-scattering response (< 0.1% at all heights, primarily confined to within and below the soot layer. Medium-sized scatterers produced a multiple-scattering response that depended on their absorbing properties. Increased radiances were simulated as compared to air only at all short wavelengths (337, 377 and 452 nm for sulfate aerosol particles (non-absorbing while decreased radiances were

  18. The effect of radioactive aerosols on fog formation

    International Nuclear Information System (INIS)

    This research study has been carried out to explore the dependence of fog formation on radioactive aerosols. The aerosols containing radioactive nuclides are called radioactive aerosols. A large number of radioactive nuclides are present in the atmosphere among which the two most important nuclides, 7Be and 210Pb are considered here in this study. Results for Activity Concentrations of these radio-nuclides in air samples in clear and foggy conditions were comparatively analyzed. About 19% increase in Activity concentration for 210Pb and about 23% increase in Activity Concentration for 7Be was recorded during fog as compared to clear conditions. This increase in Activity Concentration during fog indicates that the presence of aerosols laden with these radio-nuclides is also one of the so many factors responsible for fog formation

  19. Indirect effect of conjugate pneumococcal vaccination in a 2+1 dose schedule.

    Science.gov (United States)

    Vestrheim, Didrik F; Høiby, E Arne; Bergsaker, Marianne R; Rønning, Karin; Aaberge, Ingeborg S; Caugant, Dominique A

    2010-03-01

    In 2006, the heptavalent pneumococcal conjugate vaccine (PCV7) was introduced in the Norwegian Childhood Vaccination Programme in a 2+1 dose schedule; immunisations are administered at 3, 5 and 12 months. Changes in invasive pneumococcal disease in all ages from the baseline years 2004-2005 to 2008 were assessed, focusing on the indirect effect in the unvaccinated population. Following the introduction of PCV7, incidence rates of IPD caused by vaccine serotypes declined across all age groups, the decline being statistically significant for the age groups or = 65 years. In the unvaccinated population aged > or = 5 years the incidence rate of IPD caused by PCV7 serotypes declined by 48% from 12.34 cases/100,000 population to 6.44 cases/100,000 population, accounting for 74% of prevented cases of IPD in 2008. Among the adults aged > or = 65 years the incidence rate of IPD caused by serotypes not included in PCV7 increased. No vaccine failure was identified, indicating a very high effectiveness of the 2+1 dose schedule vaccination programme. PMID:20056192

  20. A Global Circuit Tool for Modeling Lightning Indirect Effects on Aircraft

    Science.gov (United States)

    Moussa, H.; Abdi, M.; Issac, F.; Prost, D.

    The topic of this study is electromagnetic environment and electromagnetic interference (EMI) effects, specifically the modeling of lightning indirect effects on aircraft electrical systems present on embedded and highly exposed equipments, such as nose landing gear (NLG) and nacelles, through a circuit approach. The main goal of the presented work, funded by a French national project, PREFACE, is to propose a simple equivalent electrical circuit to represent a geometrical structure, taking into account mutual, self-inductances, and resistances, which play a fundamental role in the lightning current distribution. Then this model is intended to be coupled to a functional one, describing a power train chain composed of a converter, a shielded power harness, and a motor or a set of resistors used as a load for the converter. The novelty here is to provide a pre-sizing qualitative approach allowing playing on integration in pre-design phases. This tool intends to offer a user-friendly way for replying rapidly to calls for tender, taking into account the lightning constraints.

  1. Indirect effects of cigarette butt waste on the dengue vector Aedes aegypti (Diptera: Culicidae).

    Science.gov (United States)

    Dieng, Hamady; Rajasaygar, Sudha; Ahmad, Abu Hassan; Rawi, Che Salmah Md; Ahmad, Hamdan; Satho, Tomomitsu; Miake, Fumio; Zuharah, Wan Fatma; Fukumitsu, Yuki; Saad, Ahmad Ramli; Abdul Hamid, Suhaila; Vargas, Ronald Enrique Morales; Ab Majid, Abdul Hafiz; Fadzly, Nik; Abu Kassim, Nur Faeza; Hashim, Nur Aida; Abd Ghani, Idris; Abang, Fatimah Bt; AbuBakar, Sazaly

    2014-02-01

    Despite major insecticide-based vector control programs, dengue continues to be a major threat to public health in urban areas. The reasons for this failure include the emergence of insecticide resistance and the narrowing of the spectrum of efficient products. Cigarette butts (CBs), the most commonly discarded piece of waste, also represent a major health hazard to human and animal life. CBs are impregnated with thousands of chemical compounds, many of which are highly toxic and none of which has history of resistance in mosquitoes. This study was performed to examine whether exposure to CB alters various biological parameters of parents and their progeny. We examined whether the mosquito changes its ovipositional behaviors, egg hatching, reproductive capacity, longevity and fecundity in response to CB exposure at three different concentrations. Females tended to prefer microcosms containing CBs for egg deposition than those with water only. There were equivalent rates of eclosion success among larvae from eggs that matured in CB and water environments. We also observed decreased life span among adults that survived CB exposure. Extracts of CB waste have detrimental effects on the fecundity and longevity of its offspring, while being attractive to its gravid females. These results altogether indicate that CB waste indirectly affect key adult life traits of Aedes aegypti and could conceivably be developed as a novel dengue vector control strategy, referring to previously documented direct toxicity on the larval stage. But this will require further research on CB waste effects on non-target organisms including humans. PMID:24239749

  2. THE DIRECT AND INDIRECT EFFECTS OF CUSTOMER FOCUS ON PERFORMANCE IN PUBLIC FIRMS

    Directory of Open Access Journals (Sweden)

    Zulnaidi Yaacob

    2014-06-01

    Full Text Available It has been demonstrated within the literature that the practice of customer focus is significantly associated with customer satisfaction. However, the possibility that the construct of customer focus may affect other relevant measures remains underexplored. As such, this paper discusses the effect that customer focus has on organizational performance, operating upon the premise that customer satisfaction is an end result of other relevant performance measures such as employee satisfaction, innovation, and cost benefits. Data were collected from 205 managers within the public service sector, all of whom were directly involved with the process of customer focus. The results of this study revealed that customer focus is a significant predictor of employee satisfaction, innovation, and customer satisfaction. The structural model developed also indicated that there is an indirect relationship between customer focus and customer satisfaction, as determined by employee satisfaction. In addition, the effect of customer focus on innovation is mediated by employee satisfaction. Therefore, this model implies that the practice of customer focus may enable public firms to increase their levels of performance.

  3. Explanations for religious influence on adolescent sexual behavior in Brazil: direct and indirect effects

    Directory of Open Access Journals (Sweden)

    Ana Paula de Andrade Verona

    2011-06-01

    Full Text Available Religion is becoming an important and highly present factor in the lives of many adolescents and young adults in Brazil. In addition to creating more space for them to maintain close relationships and participate actively in a religious environment, some religions have promoted the dissemination of clearer standards and objectives, as well as punitive sanctions, with respect to many aspects of their younger followers' lives, including their sexual behavior. This article examines how religion can affect, direct and indirectly, the sexual behavior of Brazilian adolescents. The main objective of this study is to look for a connection between Christian Smith's theoretical framework, which suggests several mechanisms through which religion can influence the lives of American adolescents, and ethnographic studies conducted in Brazil, as well as quantitative works that have brought attention to social and demographic consequences of recent religious transformations. Even though there is limited empirical evidence as to how the mechanisms of religious involvement work in Brazil, this study concludes that each of Smith's pathways can also be used to explain potential effects of religion on sexual behavior of Brazilian adolescents. This research should encourage empirical studies on such effects in Brazil. Besides the importance of examining the impact of the recent transformations in Brazil religious landscape on demographic phenomena, this topic deserves further consideration from Brazilian demographers because religion is a primary socialization agent of adolescents, and sexual activity is a sphere of human behavior of high importance in its religious applicability.

  4. Direct and indirect effects of kisspeptin on liver oxidant and antioxidant systems in young male rats.

    Science.gov (United States)

    Aydin, M; Oktar, S; Yonden, Z; Ozturk, O H; Yilmaz, B

    2010-06-01

    Kisspeptin is a recently discovered hypothalamic peptide which plays an important role in the central control of reproductive functions. We have investigated direct and indirect effects of kisspeptin on the liver oxidative stress in young male rats. Twenty-four rats were divided into four groups (n = 6/group). First group served as control and received saline. Kisspeptin-10 was administered to the animals in the second group (20 nmol/rat/day), for a period of 7 days. Rats were given only one dose gosereline (0.9 mg/rat), a GnRH agonist in the third group. The last group received kisspeptin-10 with gosereline. The activities of catalase, superoxide dismutase (SOD), xanthine oxidase (XO), adenosine deaminase (AD) and level of malondialdehyde were studied in liver tissue. Serum samples were separated for total antioxidant capacity (TAC), total oxidant status (TOS), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase, blood urea nitrogen (BUN), colesterol, high-density lipoprotein (HDL) and triglyceride. Kisspeptin increased the activities of SOD and catalase (p < 0.05). When compared to the control group, the levels of malondialdehyde, TOS and AST were lower, but levels of BUN, cholesterole, HDL and AD were higher in the other three groups (p < 0.05). In conclusion, our findings suggest that kisspeptin may have antioxidant and thus protective effects on the liver tissue. PMID:20517893

  5. Study of a ring-effect ions generator efficiency. Application to the charge and the neutralization of an aerosol cloud

    International Nuclear Information System (INIS)

    The knowledge of the aerosols electric charge is fundamental in the aerosols technology. The aerosols win an electric charge during their generation or in presence of a ionized medium. Facing the regulation hardening in matter of radioactive sources, the author developed a ring-effect ions generator. Tis study presents the first experimental results and discusses the generator performances. (A.L.B.)

  6. Quantitative analysis of the direct effect of aerosols over decadal scale by using ECHAM6-standalone

    Science.gov (United States)

    Muhammad, K.; Bott, A.; Hense, A.

    2013-12-01

    The influence of aerosols on climate is an important but still highly uncertain aspect in climate research. By using atmospheric general circulation model ECHAM6 our objective is to quantify the direct effect of aerosols over decadal time scale in comparison to the variability induced by the varying sea surface temperatures (SST) and sea ice concentrations (SIC) taken by the AMIP-II data base and the inevitable internal and unpredictable climate noise. We integrated the model with prescribed SST/SIC along with observed green house gases and aerosols concentrations for ten year period 1995-2004. Two ensembles with sample size ten, each have been created by starting the integrations on January 1st, 1995 with ten different initial conditions derived from two control runs over 15-years. These ensembles differ for tropospheric aerosols (TA): the non-aerosol case (NAC) is without any TA and aerosol case (AC) is utilizing a time variable data set of aerosols optical properties for input into the solar part of the ECHAM6 radiation code (Kinne et al, 2006). This set-up allows for a quantitative estimation and separation of the stationary and transient aerosol effects, the SST/SIC induced variability and the internal variability due to large scale atmospheric instabilities and non-linearities with the help of a two-way analysis of variance. We analyzed ensemble data for top of atmosphere (TOA) energy balance and temperature at 850 hPa. In the NAC, the ensemble exhibits a global and annual mean 3 W/m2 imbalance of the TOA radiation balance whereas the AC shows only 0.6 W/m2 being much closer in radiative balance over ten year period. The aerosols increase global planetary albedo from 0.29 (non-aerosol) to 0.30 for aerosol case. Extending the analysis to regional values of annual mean TOA radiation balance components, we find that the changes in TOA solar radiation budget are highly significant for static direct aerosol effect with local contributions to the total variability

  7. Aerosols in the Convective Boundary Layer: Radiation Effects on the Coupled Land-Atmosphere System

    Science.gov (United States)

    Barbaro, E.; Vila-Guerau Arellano, J.; Ouwersloot, H. G.; Schroter, J.; Donovan, D. P.; Krol, M. C.

    2013-12-01

    We investigate the responses of the surface energy budget and the convective boundary-layer (CBL) dynamics to the presence of aerosols using a combination of observations and numerical simulations. A detailed observational dataset containing (thermo)dynamic variables observed at CESAR (Cabauw Experimental Site for Atmospheric Research) and aerosol information from the European Integrated Project on Aerosol, Cloud, Climate, and Air Quality Interactions (IMPACT/EUCAARI) campaign is employed to design numerical experiments reproducing two prototype clear-sky days characterized by: (i) a well-mixed residual layer above a ground inversion and (ii) a continuously growing CBL. A large-eddy simulation (LES) model and a mixed-layer (MXL) model, both coupled to a broadband radiative transfer code and a land-surface model, are used to study the impacts of aerosol scattering and absorption of shortwave radiation on the land-atmosphere system. We successfully validate our model results using the measurements of (thermo)dynamic variables and aerosol properties for the two different CBL prototypes studied here. Our findings indicate that in order to reproduce the observed surface energy budget and CBL dynamics, information of the vertical structure and temporal evolution of the aerosols is necessary. Given the good agreement between the LES and the MXL model results, we use the MXL model to explore the aerosol effect on the land-atmosphere system for a wide range of optical depths and single scattering albedos. Our results show that higher loads of aerosols decrease irradiance, imposing an energy restriction at the surface. Over the studied well-watered grassland, aerosols reduce the sensible heat flux more than the latent heat flux. As a result, aerosols increase the evaporative fraction. Moreover, aerosols also delay the CBL morning onset and anticipate its afternoon collapse. If also present above the CBL during the morning transition, aerosols maintain a persistent near

  8. Effects of different surface treatments on bond strength of an indirect composite to bovine dentin

    OpenAIRE

    Laiza Tatiana Poskus; Rosana Sampaio Meirelles; Victor Blunck Schuina; Liana Matos Ferreira; Eduardo Moreira da Silva; Jose Guilherme Antunes Guimarães

    2015-01-01

    Background: Several surface treatments could be used to improve the bond strength (BS) between indirect composites and cement. Aim: To evaluate the BS of an indirect composite submitted to different surface treatments, cemented to bovine dentin. Settings and Design: One hundred and fifty conical cavities were prepared in slices of bovine dentin and bulk filled with the composite. Materials and Methods: After curing and removal from the cavity, the restorations were treated according ...

  9. Impacts of 20th century aerosol emissions on the South Asian monsoon in the CMIP5 models

    Directory of Open Access Journals (Sweden)

    L. Guo

    2014-12-01

    Full Text Available Comparison of single-forcing varieties of 20th century historical experiments in a subset of models from the Fifth Coupled Model Intercomparison Project (CMIP5 reveals that South Asian summer monsoon rainfall increases towards the present day in Greenhouse Gas (GHG-only experiments with respect to pre-industrial levels, while it decreases in anthropogenic aerosol-only experiments. Comparison of these single-forcing experiments with the all-forcings historical experiment suggests aerosol emissions have dominated South Asian monsoon rainfall trends in recent decades, especially during the 1950s to 1970s. The variations in South Asian monsoon rainfall in these experiments follows approximately the time-evolution of inter-hemispheric temperature gradient over the same period, suggesting a contribution from the large-scale background state relating to the asymmetric distribution of aerosol emissions about the equator. By examining the twenty-five available all-forcings historical experiments, we show that models including aerosol indirect effects dominate the negative rainfall trend. Indeed, models including only the direct radiative effect of aerosol show an increase in monsoon rainfall, consistent with the dominance of increasing greenhouse gas emissions and planetary warming on monsoon rainfall in those models. For South Asia, reduced rainfall in the models with indirect effects is related to decreased evaporation at the land surface rather than from anomalies in horizontal moisture flux, suggesting the impact of indirect effects on local aerosol emissions. This is confirmed by examination of aerosol loading and cloud droplet number trends over the South Asia region. Thus while remote aerosols and their asymmetric distribution about the equator play a role in setting the inter-hemispheric temperature distribution on which the South Asian monsoon, as one of the global monsoons, operates, the addition of indirect aerosol effects acting on very local

  10. Impacts of 20th century aerosol emissions on the South Asian monsoon in the CMIP5 models

    Science.gov (United States)

    Guo, L.; Turner, A. G.; Highwood, E. J.

    2015-06-01

    Comparison of single-forcing varieties of 20th century historical experiments in a subset of models from the Fifth Coupled Model Intercomparison Project (CMIP5) reveals that South Asian summer monsoon rainfall increases towards the present day in Greenhouse Gas (GHG)-only experiments with respect to pre-industrial levels, while it decreases in anthropogenic aerosol-only experiments. Comparison of these single-forcing experiments with the all-forcings historical experiment suggests aerosol emissions have dominated South Asian monsoon rainfall trends in recent decades, especially during the 1950s to 1970s. The variations in South Asian monsoon rainfall in these experiments follows approximately the time evolution of inter-hemispheric temperature gradient over the same period, suggesting a contribution from the large-scale background state relating to the asymmetric distribution of aerosol emissions about the equator. By examining the 24 available all-forcings historical experiments, we show that models including aerosol indirect effects dominate the negative rainfall trend. Indeed, models including only the direct radiative effect of aerosol show an increase in monsoon rainfall, consistent with the dominance of increasing greenhouse gas emissions and planetary warming on monsoon rainfall in those models. For South Asia, reduced rainfall in the models with indirect effects is related to decreased evaporation at the land surface rather than from anomalies in horizontal moisture flux, suggesting the impact of indirect effects on local aerosol emissions. This is confirmed by examination of aerosol loading and cloud droplet number trends over the South Asia region. Thus, while remote aerosols and their asymmetric distribution about the equator play a role in setting the inter-hemispheric temperature distribution on which the South Asian monsoon, as one of the global monsoons, operates, the addition of indirect aerosol effects acting on very local aerosol emissions also

  11. Characteristics and direct radiative effect of mid-latitude continental aerosols: the ARM case

    Directory of Open Access Journals (Sweden)

    M. G. Iziomon

    2003-01-01

    Full Text Available A multi-year field measurement analysis of the characteristics and direct radiative effect of aerosols at the Southern Great Plains (SGP central facility of the Atmospheric Radiation Measurement (ARM Program is presented. Inter-annual mean and standard deviation of submicrometer scattering fraction (at 550 nm and Ångström exponent å (450 nm, 700 nm at the mid-latitude continental site are indicative of the scattering dominance of fine mode aerosol particles, being 0.84±0.03 and 2.25±0.09, respectively. We attribute the diurnal variation of submicron aerosol concentration to coagulation, photochemistry and the evolution of the boundary layer. Precipitation does not seem to play a role in the observed afternoon maximum in aerosol concentration. Submicron aerosol mass at the site peaks in the summer (12.1±6.7mg m-3, with the summer value being twice that in the winter. Of the chemically analyzed ionic components (which exclude carbonaceous aerosols, SO4= and NH4+ constitute the dominant species at the SGP seasonally, contributing 23-30% and 9-12% of the submicron aerosol mass, respectively. Although a minor species, there is a notable rise in NO3- mass fraction in winter. We contrast the optical properties of dust and smoke haze. The single scattering albedo w0 shows the most remarkable distinction between the two aerosol constituents. We also present aircraft measurements of vertical profiles of aerosol optical properties at the site. Annually, the lowest 1.2 km contributes 70% to the column total light scattering coefficient. Column-averaged and surface annual mean values of hemispheric backscatter fraction (at 550 nm, w0 (at 550 nm and å (450 nm, 700 nm agree to within 5% in 2001. Aerosols produce a net cooling (most pronounced in the spring at the ARM site

  12. Susceptibility of Stored-Product Psocids to Aerosol Insecticides

    OpenAIRE

    Opit, George P.; Arthur, Frank H.; Throne, James E.; Payton, Mark E.

    2012-01-01

    The efficacies of commercial methoprene and esfenvalerate aerosols for control of stored-product psocid pests were evaluated in simulated field studies. The efficacies of methoprene, esfenvalerate EC, the carrier Isopar-M™, and a combination of methoprene and esfenvalerate aerosols for control of Liposcelis decolor (Pearman) (Psocoptera: Liposcelididae) and Liposcelis entomophila (Enderlein) nymphs were assessed, and the effects of direct and indirect exposure of Liposcelis bostrychophila Bad...

  13. Assessment of multi-decadal WRF-CMAQ simulations for understanding direct aerosol effects on radiation "brightening" in the United States

    Directory of Open Access Journals (Sweden)

    C.-M. Gan

    2015-07-01

    Full Text Available Multi-decadal simulations with the coupled WRF-CMAQ model have been conducted to systematically investigate the changes in anthropogenic emissions of SO2 and NOx over the past 21 years (1990–2010 across the United States (US, their impacts on anthropogenic aerosol loading over North America, and subsequent impacts on regional radiation budgets. In particular, this study attempts to determine the consequences of the changes in tropospheric aerosol burden arising from substantial reductions in emissions of SO2 and NOx associated with control measures under the Clean Air Act (CAA especially on trends in solar radiation. Extensive analyses conducted by Gan et al. (2014 utilizing observations (e.g. SURFRAD, CASTNET, IMPROVE and ARM over the past 16 years (1995–2010 indicate a shortwave (SW radiation (both all-sky and clear-sky "brightening" in the US. The relationship of the radiation brightening trend with decreases in the aerosol burden is less apparent in the western US. One of the main reasons for this is that the emission controls under the CAA were aimed primarily at reducing pollutants in areas violating national air quality standards, most of which were located in the eastern US while the relatively less populated areas in the western US were less polluted at the beginning of this study period. Comparisons of model results with observations of aerosol optical depth (AOD, aerosol concentration, and radiation demonstrate that the coupled WRF-CMAQ model is capable of replicating the trends well even through it tends to underestimate the AOD. In particular, the sulfate concentration predictions were well matched with the observations. The discrenpancies found in the clear-sky diffuse SW radiation are likely due to several factors such as potential increase of ice particles associated with increasing air traffic, the definition of "clear-sky" in the radiation retrieval methodology and aerosol semi-direct and/or indirect effects which cannot be

  14. Assessment of multi-decadal WRF-CMAQ simulations for understanding direct aerosol effects on radiation "brightening" in the United States

    Science.gov (United States)

    Gan, C.-M.; Pleim, J.; Mathur, R.; Hogrefe, C.; Long, C. N.; Xing, J.; Wong, D.; Gilliam, R.; Wei, C.

    2015-07-01

    Multi-decadal simulations with the coupled WRF-CMAQ model have been conducted to systematically investigate the changes in anthropogenic emissions of SO2 and NOx over the past 21 years (1990-2010) across the United States (US), their impacts on anthropogenic aerosol loading over North America, and subsequent impacts on regional radiation budgets. In particular, this study attempts to determine the consequences of the changes in tropospheric aerosol burden arising from substantial reductions in emissions of SO2 and NOx associated with control measures under the Clean Air Act (CAA) especially on trends in solar radiation. Extensive analyses conducted by Gan et al. (2014) utilizing observations (e.g. SURFRAD, CASTNET, IMPROVE and ARM) over the past 16 years (1995-2010) indicate a shortwave (SW) radiation (both all-sky and clear-sky) "brightening" in the US. The relationship of the radiation brightening trend with decreases in the aerosol burden is less apparent in the western US. One of the main reasons for this is that the emission controls under the CAA were aimed primarily at reducing pollutants in areas violating national air quality standards, most of which were located in the eastern US while the relatively less populated areas in the western US were less polluted at the beginning of this study period. Comparisons of model results with observations of aerosol optical depth (AOD), aerosol concentration, and radiation demonstrate that the coupled WRF-CMAQ model is capable of replicating the trends well even through it tends to underestimate the AOD. In particular, the sulfate concentration predictions were well matched with the observations. The discrenpancies found in the clear-sky diffuse SW radiation are likely due to several factors such as potential increase of ice particles associated with increasing air traffic, the definition of "clear-sky" in the radiation retrieval methodology and aerosol semi-direct and/or indirect effects which cannot be readily

  15. Projected effects of declining anthropogenic aerosols on the southern annular mode

    International Nuclear Information System (INIS)

    Declining emissions of anthropogenic aerosols have been shown to contribute to global warming in climate projections from the Coupled Model Intercomparison Project Phase 5 (CMIP5). This study considers the response of the southern annular mode (SAM) in austral summer to declining aerosols in simulations forced by Representative Concentration Pathway 4.5 (RCP4.5) using CSIRO-Mk3.6, a CMIP5-generation model. A ten-member ensemble forced by RCP4.5 for the period 2006–2100 is compared with another experiment, which is identical except that emissions of anthropogenic aerosols are held fixed at their 2005 values. With fixed aerosol emissions, the model simulates a negative (but statistically insignificant) ensemble-mean SAM trend in austral summer, suggesting that the effects of recovering stratospheric ozone slightly outweigh the effects of increasing long-lived greenhouse gases (GHGs). In contrast, the standard RCP4.5 experiment (including additional warming due to declining aerosols) simulates a positive ensemble-mean SAM trend, and the difference between the two trends is significant at 5%. The response of Southern Hemisphere zonal-mean atmospheric circulation and temperature to declining aerosols resembles the response to increasing GHGs; this suggests that the positive SAM trend due to declining aerosols may be driven by mechanisms that are similar to those that cause the positive SAM trend in response to increasing GHGs. (letter)

  16. Climate implications of carbonaceous aerosols: An aerosol microphysical study using the GISS/MATRIX climate model

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Susanne E.; Menon, Surabi; Koch, Dorothy; Bond, Tami; Tsigaridis, Kostas

    2010-04-09

    Recently, attention has been drawn towards black carbon aerosols as a likely short-term climate warming mitigation candidate. However the global and regional impacts of the direct, cloud-indirect and semi-direct forcing effects are highly uncertain, due to the complex nature of aerosol evolution and its climate interactions. Black carbon is directly released as particle into the atmosphere, but then interacts with other gases and particles through condensation and coagulation processes leading to further aerosol growth, aging and internal mixing. A detailed aerosol microphysical scheme, MATRIX, embedded within the global GISS modelE includes the above processes that determine the lifecycle and climate impact of aerosols. This study presents a quantitative assessment of the impact of microphysical processes involving black carbon, such as emission size distributions and optical properties on aerosol cloud activation and radiative forcing. Our best estimate for net direct and indirect aerosol radiative forcing change is -0.56 W/m{sup 2} between 1750 and 2000. However, the direct and indirect aerosol effects are very sensitive to the black and organic carbon size distribution and consequential mixing state. The net radiative forcing change can vary between -0.32 to -0.75 W/m{sup 2} depending on these carbonaceous particle properties. Assuming that sulfates, nitrates and secondary organics form a coating shell around a black carbon core, rather than forming a uniformly mixed particles, changes the overall net radiative forcing from a negative to a positive number. Black carbon mitigation scenarios showed generally a benefit when mainly black carbon sources such as diesel emissions are reduced, reducing organic and black carbon sources such as bio-fuels, does not lead to reduced warming.

  17. Parental, peer, school, and neighborhood influences on adolescent substance use: direct and indirect effects and ethnic variations.

    Science.gov (United States)

    Su, Jinni; Supple, Andrew J

    2014-01-01

    The current study examined how contextual influences are related to adolescent substance use using an ethnically diverse sample of adolescents. A total of 5,992 adolescents (5,185 European American, 330 African American, 160 Hispanic American, 179 Asian American, and 138 Southeast Asian American) from Dane county, Wisconsin, completed surveys at school. Structural equation modeling was conducted to examine direct versus indirect effects of parental, peer, school, and neighborhood influences and differences in associations across ethnicity. Results indicated that contextual influences on adolescent substance use were both direct and indirect; the strength of associations between contextual influences and adolescent substance use varied across ethnic groups. PMID:25176117

  18. A satellite view of the direct effect of aerosols on solar radiation at global scale

    Science.gov (United States)

    Hatzianastassiou, Nikolaos; Papadimas, Christos D.; Matsoukas, Christos; Fotiadi, Aggeliki; Benas, Nikolaos; Vardavas, Ilias

    2016-04-01

    Aerosols are a key parameter for better understanding and predicting current and future climate change. They are determining, apart from clouds, patterns of solar radiation through scattering and absorption processes. Especially, under cloud-free skies, aerosols are the major modulator of the solar radiation budget of the Earth-atmosphere system. Although significant improvement has been made as to better understanding the direct radiative effect (DRE) of aerosols, there is still a need for further improvement in our knowledge of the DRE spatial and temporal patterns, in particular with respect to extended spatial and temporal coverage of relevant information. In an ongoing rapidly evolving era of great satellite-based achievements, concerning the knowledge of solar radiation budget and its modulators, and with the great progress in obtaining significant information on key aerosol optical properties needed for modeling DRE, it is a great challenge to use all this new aerosol information and to see what is the new acquired scientific knowledge. The objective of this study is to obtain an improved view of global aerosol DRE effects using contemporary accurate data for the important atmospheric and surface parameters determining the solar radiation budget, with emphasis to state of the art aerosol data. Thus, a synergy is made of different datasets providing the necessary input data and of a detailed spectral radiative transfer model (RTM) to compute spectral globally distributed aerosol DREs. Emphasis is given on using highly accurate and well-tested aerosol optical properties. Spectral information on aerosol optical depth (AOD) is taken from retrieved products of the MODerate resolution Imaging Spectroradiometer (MODIS) instrument, while similar information is taken from MODIS for the aerosol asymmetry parameter (AP) over ocean. Information from MODIS is also taken for the aerosol single scattering albedo (SSA). All this information comes from the latest Collection

  19. Aerosol radiative effects in the ultraviolet, visible, and near-infrared spectral ranges using long-term aerosol data series over the Iberian Peninsula

    Directory of Open Access Journals (Sweden)

    D. Mateos

    2014-04-01

    Full Text Available A better understanding of the aerosol radiative properties is a crucial challenge for climate change studies. This study aims to provide a complete characterization of aerosol radiative effects in different spectral ranges within the shortwave (SW solar spectrum. For this purpose, long-term datasets of aerosol properties from six AERONET stations located in the Iberian Peninsula (Southwestern Europe are analyzed in term of climatology characterization and trends. Aerosol information is used as input to the libRadtran model in order to determine the aerosol radiative effect at the surface in the ultraviolet (AREUV, visible (AREVIS, near-infrared (ARENIR, and the entire SW range (ARESW under cloud-free conditions. Over the whole Iberian Peninsula, aerosol radiative effects in the different spectral ranges are: −1.1 UV −2, −5.7 VIS −2, −2.8 NIR −2, and −9.5 SW −2. The four variables showed positive statistically significant trends between 2004 and 2012, e.g., ARESW increased +3.6 W m−2 per decade. This fact is linked to the decrease in the aerosol load, which presents a trend of −0.04 per unit of aerosol optical depth at 500 nm per decade, hence a reduction of aerosol effect on solar radiation at the surface is seen. Monthly means of ARE show a seasonal pattern with larger values in spring and summer. The aerosol forcing efficiency (AFE, ARE per unit of aerosol optical depth, is also evaluated in the four spectral ranges. AFE exhibits a dependence on single scattering albedo and a weaker one on Ångström exponent. AFE is larger (in absolute value for small and absorbing particles. The contributions of the UV, VIS, and NIR ranges to the SW efficiency vary with the aerosol types. Aerosol size determines the fractions of AFEVIS/AFESW and AFENIR/AFESW. VIS range is the dominant region for all types, although non-absorbing large particles cause a more equal contribution of VIS and NIR intervals. The AFEUV / AFESW ratio shows a

  20. Indirect effects of bioinsecticides on the nontarget fauna: The Camargue experiment calls for future research

    Science.gov (United States)

    Poulin, Brigitte

    2012-10-01

    Following its high selectivity and low toxicity to nontarget organisms, Bacillus thuringiensis var. israelensis (Bti) has become the most commonly used microbial agent to control mosquitoes worldwide. Considered non-toxic to mammals, birds, fish, plants and most aquatic organisms, Bti direct effects on the nontarget fauna are largely limited to non-biting midges (Chironomidae). Studies addressing the indirect effects of Bti through food web perturbations are scanty and showed no significant results. Mosquito-control in southern France was implemented in 1965 using various insecticides over 400 km of coast. In spite of a high mosquito nuisance, the Camargue wetlands were excluded from this control programme to preserve biodiversity. The expanding use of Bti has prompted the implementation of an experimental mosquito control in 2006 involving 2500 of the 25,000 ha of larval biotopes of the Camargue, accompanied by impact studies on the nontarget fauna. Using birds from natural and human-inhabited areas as model species, we assessed trophic perturbations caused by three years of Bti applications. The preliminary results of this 5-yr programme revealed significant effects of Bti spraying on abundance of reed-dwelling invertebrates serving as food to passerines, as well as on the diet and breeding success of house martins nesting in rural estates and small towns. Very few studies (if any) have provided such compelling evidence of an insecticide affecting vertebrate populations, putting into question the environmental-friendly character of Bti, at least in some areas. The significance of these results are discussed within a wider context and completed with an analysis of the current Bti bibliography to highlight and orient priorities for future research on this topic.

  1. Indirect Effects in the Peer Victimization-Academic Achievement Relation: The Role of Academic Self-Concept and Gender

    Science.gov (United States)

    Jenkins, Lyndsay N.; Demaray, Michelle Kilpatrick

    2015-01-01

    Peer victimization is a concern because victimized youth are more likely to have social, emotional, and academic difficulties. The current study examined the link between peer victimization and academic achievement by exploring the indirect effect of academic self-concept on two variables. The sample consisted of 140 middle school students (40%…

  2. Drawbacks of the use of indirect estimates of renal function to evaluate the effect of risk factors on renal function

    NARCIS (Netherlands)

    Verhave, JC; Gansevoort, RT; Hillege, HL; De Zeeuw, D; Curhan, GC; De Jong, PE

    2004-01-01

    Many epidemiologic studies presently aim to evaluate the effect of risk factors on renal function. As direct measurement of renal function is cumbersome to perform, epidentiologic studies generally use an indirect estimate of renal function. The consequences of using different methods of renal funct

  3. An Indirect Effects Model of the Association between Poverty and Child Functioning: The Role of Children's Poverty-Related Stress

    Science.gov (United States)

    Wadsworth, Martha E.; Raviv, Tali; Reinhard, Christine; Wolff, Brian; Santiago, Catherine DeCarlo; Einhorn, Lindsey

    2008-01-01

    The authors tested a theoretical model positing that poverty has an indirect effect on child and adolescent functioning through children's poverty-related stress. Path analyses with a multiethnic sample of 164 children aged 6 to 18 revealed that the stress associated with poverty, such as economic strain, family conflict, violence/trauma, and…

  4. The Direct and Indirect Effects of Paliperidone Extended-release on Depressive Symptoms in Schizoaffective Disorder: A Path Analysis

    OpenAIRE

    Turkoz, Ibrahim; Fu, Dong-Jing; Bossie, Cynthia A; Alphs, Larry

    2015-01-01

    Background: This analysis evaluates improvement in symptoms of depression in patients with schizoaffective disorder administered oral paliperidone extended-release by accounting for the magnitude of direct and indirect (changes in negative and positive symptoms and worsening of extrapyramidal symptoms) treatment effects on depressive symptoms.

  5. Future aerosol reductions and widening of the northern tropical belt

    Science.gov (United States)

    Allen, Robert J.; Ajoku, Osinachi

    2016-06-01

    Observations show that the tropical belt has widened over the past few decades, a phenomenon associated with poleward migration of subtropical dry zones and large-scale atmospheric circulation. Although part of this signal is related to natural climate variability, studies have identified an externally forced contribution primarily associated with greenhouse gases (GHGs) and stratospheric ozone loss. Here we show that the increase in aerosols over the twentieth century has led to contraction of the northern tropical belt, thereby offsetting part of the widening associated with the increase in GHGs. Over the 21st century, however, when aerosol emissions are projected to decrease, the effects of aerosols and GHGs reinforce one another, both contributing to widening of the northern tropical belt. Models that have larger aerosol forcing, by including aerosol indirect effects on cloud albedo and lifetime, yield significantly larger Northern Hemisphere (NH) tropical widening than models with direct aerosol effects only. More targeted simulations show that future reductions in aerosols can drive NH tropical widening as large as greenhouse gases, and idealized simulations show the importance of NH midlatitude aerosol forcing. Mechanistically, the 21st century reduction in aerosols peaks near 40°N, which results in a corresponding maximum increase in surface solar radiation, NH midlatitude tropospheric warming amplification, and a poleward shift in the latitude of maximum baroclinicity, implying a corresponding shift in atmospheric circulation. If models with aerosol indirect effects better represent the real world, then future aerosol changes are likely to be an important -- if not dominant -- driver of NH tropical belt widening.

  6. Combustion aerosols from municipal waste incineration - Effect of fuel feedstock and plant operation

    DEFF Research Database (Denmark)

    Zeuthen, J.H.; Pedersen, Anne Juul; Hansen, Jørn;

    2007-01-01

    Combustion aerosols were measured in a 22MW ( thermal energy) municipal waste incinerator. Different types of waste fractions were added to a base- load waste and the effect on aerosol formation was measured. The waste fractions applied were: PVC plastic, pressure- impregnated wood, shoes, salt...... concentration was stable and close to the reference PM2.5- value of 252 +/- 21mg= m(3) ( std. T, P). The total number concentration deviated during runs and between runs spanning from 43.10(6) to 87 . 10(6)#/cm(3)( std. T, P). The aerosols formed were mixtures of dense and aggregated particles in all tests. The...

  7. Distinct effects of anthropogenic aerosols on the East Asian summer monsoon between multidecadal strong and weak monsoon stages

    Science.gov (United States)

    Xie, Xiaoning; Wang, Hongli; Liu, Xiaodong; Li, Jiandong; Wang, Zhaosheng; Liu, Yangang

    2016-06-01

    Because industrial emissions of anthropogenic aerosols over East Asia have greatly increased in recent decades, the interactions between atmospheric aerosols and the East Asian summer monsoon (EASM) have attracted enormous attention. To further understand the aerosol-EASM interaction, we investigate the impacts of anthropogenic aerosols on the EASM during the multidecadal strong (1950-1977) and weak (1978-2000) EASM stages using the Community Atmospheric Model 5.1. Numerical experiments are conducted for the whole period, including the two different EASM stages, with present day (PD, year 2000) and preindustrial (PI, year 1850) aerosol emissions, as well as the observed time-varying aerosol emissions. A comparison of the results from PD and PI shows that, with the increase in anthropogenic aerosols, the large-scale EASM intensity is weakened to a greater degree (-9.8%) during the weak EASM stage compared with the strong EASM stage (-4.4%). The increased anthropogenic aerosols also result in a significant reduction in precipitation over North China during the weak EASM stage, as opposed to a statistically insignificant change during the strong EASM stage. Because of greater aerosol loading and the larger sensitivity of the climate system during weak EASM stages, the aerosol effects are more significant during these EASM stages. These results suggest that anthropogenic aerosols from the same aerosol emissions have distinct effects on the EASM and the associated precipitation between the multidecadal weak and strong EASM stages.

  8. Aerosol studies

    International Nuclear Information System (INIS)

    As part of the continuing studies of the effects of very severe reactor accidents, an effort was made to develop, test, and improve simple, effective, and inexpensive methods by which the average citizen, using only materials readily available, could protect his residence, himself, and his family from injury by toxic aerosols. The methods for protection against radioactive aerosols should be equally effective against a clandestine biological attack by terrorists. The results of the tests to date are limited to showing that spores of the harmless bacterium, bacillus globegii (BG), can be used as a simulant for the radioactive aerosols. An aerosol generator of Lauterbach type was developed which will produce an essentially monodisperse aerosol at the rate of 109 spores/min. Analytical techniques have been established which give reproducible results. Preliminary field tests have been conducted to check out the components of the system. Preliminary tests of protective devices, such as ordinary vacuum sweepers, have given protection factors of over 1000

  9. Estimating Direct and Indirect Effects of Foreign Direct Investment on Firm Productivity in the Presence of Interactions between Firms

    OpenAIRE

    Girma, Sourafel; Gong, Yundan; Görg, Holger; Lancheros, Sandra

    2014-01-01

    We implement a method to estimate the direct effects of foreign-ownership on foreign firms' productivity and the indirect effects (or spillovers) from the presence of foreign-owned firms on other foreign and domestic firms' productivity in a unifying framework, taking interactions between firms into account. To do so, we relax a fundamental assumption made in empirical studies examining a direct causal effect of foreign ownership on firm productivity, namely that of no interactions between fi...

  10. High plant species diversity indirectly mitigates CO 2- and N-induced effects on grasshopper growth

    Science.gov (United States)

    Strengbom, Joachim; Reich, Peter B.; Ritchie, Mark E.

    2008-09-01

    We examined how elevated atmospheric [CO 2] and higher rate of nitrogen (N) input may influence grasshopper growth by changing food plant quality and how such effects may be modified by species diversity of the plant community. We reared grasshopper nymphs ( Melanoplus femurrubrum) on Poa pratensis from field-grown monocultures or polycultures (16 species) that were subjected to either ambient or elevated levels of CO 2 and N. Grasshopper growth rate was higher on P. pratensis leaves grown in monocultures than in polycultures, higher on P. pratensis grown under elevated than under ambient [CO 2], and higher on P. pratensis grown under elevated than under ambient [N]. The higher growth rate observed on P. pratensis exposed to elevated [CO 2] was, however, less pronounced for polyculture- than monoculture-grown P. pratensis. Growth rate of the grasshoppers was positively correlated with leaf [N], [C], and concentration of soluble carbohydrates + lipids. Concentration of non-structural carbohydrates + lipids was higher in leaves grown under elevated than under ambient [CO 2], and the difference between P. pratensis grown under ambient and elevated [CO 2] was greater for monoculture- than polyculture-grown P. pratensis. In addition, leaf N concentration was higher in P. pratensis grown in monocultures than in polycultures, suggesting that plant species richness, indirectly, may influence insect performance by changed nutritional value of the plants. Because we found interactive effects between all factors included ([CO 2], [N], and plant species diversity), our results suggest that these parameters may influence plant-insect interactions in a complex way that is not predictable from the sum of single factor manipulations.

  11. Population-Level Impact of Ontario's Infant Rotavirus Immunization Program: Evidence of Direct and Indirect Effects.

    Directory of Open Access Journals (Sweden)

    Sarah E Wilson

    Full Text Available To evaluate the direct and indirect population impact of rotavirus (RV immunization on hospitalizations and emergency department (ED visits for acute gastroenteritis (AGE in Ontario before and after the publicly-funded RV immunization program.Administrative data was used to identify ED visits and hospitalizations for all Ontarians using ICD-10 codes. We used two outcome definitions: RV-specific AGE (RV-AGE and codes representing RV-, other viral and cause unspecified AGE ("overall AGE". The pre-program and public program periods were August 1, 2005 to July 31, 2011; and August 1, 2011 to March 31, 2013, respectively. A negative binominal regression model that included the effect of time was used to calculate rates and rate ratios (RRs and 95% confidence intervals (CIs for RV-AGE and overall AGE between periods, after adjusting for age, seasonality and secular trends. Analyses were conducted for all ages combined and age stratified.Relative to the pre-program period, the adjusted RRs for RV-AGE and overall AGE hospitalizations in the public program period were 0.29 (95%CI: 0.22-0.39 and 0.68 (95%CI: 0.62-0.75, respectively. Significant reductions in RV-AGE hospitalizations were noted overall and for the following age bands: = 65 years (RR 0.80, 95%CI: 0.72-0.90. The program was associated with adjusted RRs of 0.32 (95% CI: 0.20-0.52 for RV-AGE ED visits and 0.90 (95% CI: 0.85-0.96 for overall AGE ED visits.This large, population-based study provides evidence of the impact of RV vaccine in preventing hospitalizations and ED visits for RV-AGE and overall AGE, including herd effects.

  12. Comparative effects of biomass pre-treatments for direct and indirect transesterification to enhance microalgal lipid recovery

    Directory of Open Access Journals (Sweden)

    Forough eGhasemi Naghdi

    2014-12-01

    Full Text Available Microalgal lipid recovery for biodiesel production is currently considered suboptimal, but pre-treatment of algal biomass, the use of solvent mixtures and the positioning of transesterification can lead to increased yields. Here, the effect of various reportedly successful pre-treatments and solvent mixtures were directly compared to each other and combined with direct and indirect transesterification methods using the oleaginous microalga Tetraselmis sp. M8. Microwave and thermal pre-treatments were applied and the total lipid and fatty acid methyl ester (FAME recoveries were investigated. The application of pre-treatments increased FAME recovery through indirect transesterification when a Soxhlet system was used but they had no significant effect for direct transesterification. Gravimetric analyses of total lipids revealed that lipid recovery was highest when utilizing the chloroform-based Bligh and Dyer extraction method; however FAME yield was the highest when applying a Soxhlet system utilizing a solvent mixture of hexane-ethanol (3:1. Total lipid recovery did not necessarily correlate with the recovery of FAMEs. The highest FAME recovery was achieved from thermal or microwave pre-treated biomass followed by indirect transesterification through Soxhlet extraction. FAME recovery could be more than doubled (increase of up to 171% under these conditions. We conclude that a simple thermal pre-treatment (80°C for 10 min in combination with solvent mixture extraction through indirect transesterification may present a cost-effective and scalable option for large-scale lipid extraction from microalgae.

  13. An effective model for fermion dark matter. Indirect detection of supersymmetric dark matter in astronomy with the CELESTE Telescope

    International Nuclear Information System (INIS)

    The purpose of this thesis is to discuss both phenomenological and experimental aspects of Dark Matter, related to its indirect detection with gamma-ray astronomy. In the MSSM framework, neutralinos arise as natural candidates to non-baryonic and Cold Dark Matter, whose gravitational effects manifest in the Universe at different scales. As they are Majorana particles, they may in principle annihilate in high density regions, as the centres of galaxies, and produce gamma rays. Nevertheless, the expected fluxes are basically low compared to experimental sensitivities. After estimating gamma fluxes from M31 and Draco galaxies in the MSSM scheme, we first generalize the MSSM couplings by studying an effective Lagrangian. We show that the only constraint of imposing a relic abundance compatible with recent measurements obviously deplete significantly the gamma ray production, but also that predictions in this effective approach are more optimistic for indirect detection than the MSSM. In a second part, we present the indirect searches for Dark Matter performed with the CELESTE Cherenkov telescope towards the galaxy M31. We propose a statistical method to reconstruct spectra, mandatory to discriminate classical and exotic spectra. The M31 data analysis enables the extraction of an upper limit on the gamma ray flux, which is the first worldwide for a galaxy in the energy range 50-500 GeV, and whose astrophysical interest goes beyond indirect searches for Dark Matter. (author)

  14. A Simple Model for the Cloud Adjacency Effect and the Apparent Bluing of Aerosols Near Clouds

    Science.gov (United States)

    Marshak, Alexander; Wen, Guoyong; Coakley, James A., Jr.; Remer, Lorraine A.; Loeb,Norman G.; Cahalan, Robert F.

    2008-01-01

    In determining aerosol-cloud interactions, the properties of aerosols must be characterized in the vicinity of clouds. Numerous studies based on satellite observations have reported that aerosol optical depths increase with increasing cloud cover. Part of the increase comes from the humidification and consequent growth of aerosol particles in the moist cloud environment, but part comes from 3D cloud-radiative transfer effects on the retrieved aerosol properties. Often, discerning whether the observed increases in aerosol optical depths are artifacts or real proves difficult. The paper provides a simple model that quantifies the enhanced illumination of cloud-free columns in the vicinity of clouds that are used in the aerosol retrievals. This model is based on the assumption that the enhancement in the cloud-free column radiance comes from enhanced Rayleigh scattering that results from the presence of the nearby clouds. The enhancement in Rayleigh scattering is estimated using a stochastic cloud model to obtain the radiative flux reflected by broken clouds and comparing this flux with that obtained with the molecules in the atmosphere causing extinction, but no scattering.

  15. Effects of aerosol particle size on dispersion and continuous air monitor response in a plutonium laboratory

    International Nuclear Information System (INIS)

    The effectiveness of continuous air monitors (CAMs) in protecting plutonium workers depends on the efficiency of aerosol transport from the release point to the CAM. The main processes for aerosol transport are diffusion, forced convection, and gravitational settling. The transport of particles relative to each of these processes depends on particle size. Studies have shown that activity median aerodynamic diameters for plutonium aerosols can range from less than 0.1 μm to greater than 10 μm. The purpose of this study was to characterize the influence of particle size on aerosol transport and CAM response in a plutonium laboratory. Polydisperse dioctyl sebacate oil aerosols were released from multiple locations within a plutonium laboratory at Los Alamos National Laboratory. An array of Laser Particle counters (LPCs) positioned in the laboratory measured time resolved aerosol dispersion. Aerosol concentrations were binned into two size ranges: (1) 0.5 μm to 5.0 μm, and (2) those greater than 5.0 μm. Statistical comparisons were done and the results suggested that transport efficiency was greater for smaller particles than larger particles in this laboratory. This result suggested the importance of using particles of similar physical characteristics to those of the source when doing tests to decide optimal placement of CAMs

  16. Effect Size Measures for Mediation Models: Quantitative Strategies for Communicating Indirect Effects

    Science.gov (United States)

    Preacher, Kristopher J.; Kelley, Ken

    2011-01-01

    The statistical analysis of mediation effects has become an indispensable tool for helping scientists investigate processes thought to be causal. Yet, in spite of many recent advances in the estimation and testing of mediation effects, little attention has been given to methods for communicating effect size and the practical importance of those…

  17. Educational Differences in Postmenopausal Breast Cancer - Quantifying Indirect Effects through Health Behaviors, Body Mass Index and Reproductive Patterns

    DEFF Research Database (Denmark)

    Hvidtfeldt, Ulla Arthur; Lange, Theis; Andersen, Ingelise;

    2013-01-01

    100,000 person-years at risk. Of these, 26% (95% CI 14%-69%) could be attributed to alcohol consumption. Similar effects wereobserved for age at first birth (32%; 95% CI 10%-257%), parity (19%; 95%CI 10%-45%), and hormone therapy use (10%; 95% CI 6%-18%). Educational level modified the effect of......Studying mechanisms underlying social inequality in postmenopausal breast cancer is important in order to develop prevention strategies. Standard methods for investigating indirect effects, by comparing crude models to adjusted, are often biased. We applied a new method enabling the decomposition...... of the effect of educational level on breast cancer incidence into indirect effects through reproductive patterns (parity and age at first birth), body mass index and health behavior (alcohol consumption, physical inactivity, and hormone therapy use). The study was based on a pooled cohort of 6...

  18. Direct Climatic Effect of Aerosols and Interdecadal Variations over East Asia Investigated by a Regional Coupled Climate-Chemistry/Aerosol Model

    Institute of Scientific and Technical Information of China (English)

    HAN Zhi-Wei; XIONG Zhe; LI Jia-Wei

    2011-01-01

    The direct climatic effect of aerosols for the 1980-2000 period over East Asia was numerically investigated by a regional scale coupled climate-chemistry/ aerosol model, which includes major anthropogenic aerosols (sulfate, black carbon, and organic carbon) and natural aerosols (soil dust and sea salt). Anthropogenic emissions used in model simulation are from a global emission inventory prepared for the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5), whereas natural aerosols are calculated online in the model. The simulated 20-year average direct solar radiative effect due to aerosols at the surface was estimated to be in a range of-9- -33 W m-2 over most areas of China, with maxima over the Gobi desert of West China, and-12 W m-2 to -24 W m-2 over the Sichuan Basin, the middle and lower reaches of the Yellow River and the Yangtze River. Aerosols caused surface cooling in most areas of East Asia, with maxima of-0.8℃ to -1.6℃ over the deserts of West China, the Sichuan Basin, portions of central China, and the middle reaches of the Yangtze River. Aerosols induced a precipitation decrease over almost the entire East China, with maxima of-90 mm/year to -150 mm/year over the Sichuan Basin, the middle reaches of the Yangtze River and the lower reaches of the Yellow River. Interdecadal variation of the climate response to the aerosol direct radiative effect is evident, indicating larger decrease in surface air temperature and stronger per- turbation to precipitation in the 1990s than that in the 1980s, which could be due to the interdecadal variation of anthropogenic emissions.

  19. Potential sensitivity of photosynthesis and isoprene emission to direct radiative effects of atmospheric aerosol pollution

    OpenAIRE

    Strada, Susanna; Unger, Nadine

    2016-01-01

    A global Earth system model is applied to quantify the impacts of direct anthropogenic aerosol effective radiative forcing on gross primary productivity (GPP) and isoprene emission. The impacts of different pollution aerosol sources (anthropogenic, biomass burning, and non-biomass burning) are investigated by performing sensitivity experiments. The model framework includes all known light and meteorological responses of photosynthesis, but uses fixed canopy structures and ph...

  20. Integration of the Equations of Classical Electrode-Effect Theory with Aerosols

    Science.gov (United States)

    Kalinin, A. V.; Leont'ev, N. V.; Terent'ev, A. M.; Umnikov, E. D.

    2016-04-01

    This paper is devoted to an analytical study of the one-dimensional stationary system of equations for modeling of the electrode effect in the Earth's atmospheric layer with aerosols. New integrals of the system are derived. Using these integrals, the expressions for solutions of the system and estimates of the electrode layer's thickness as a function of the aerosol concentration are obtained for numerical parameters close to real.

  1. A case study of the radiative effect of aerosols over Europe: EUCAARI-LONGREX

    OpenAIRE

    Esteve, Anna R.; Highwood, Eleanor J.; Ryder, Claire L.

    2016-01-01

    The radiative effect of anthropogenic aerosols over Europe during the 2008 European Integrated Project on Aerosol Cloud Climate and Air Quality Interactions Long Range Experiment (EUCAARI-LONGREX) campaign has been calculated using measurements collected by the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft and radiative transfer modelling. The aircraft sampled anthropogenically perturbed air masses across north-western Europe under anticyclonic conditio...

  2. Effect of lactose solid-state on the aerosolization performance of drug-carrier mixtures

    OpenAIRE

    Della Bella, Andrea

    2016-01-01

    Lactose, in particular α-lactose monohydrate, is the most used carrier for inhalation. Its surface and solid-state properties are of paramount importance in determining drug aerosolization performance. However, these properties may be altered by processing, such as micronization, thus affecting the product performance and stability. The present research project focused on the study of the effect of lactose solid-state on the aerosolization performance of drug-carrier mixtures, giving parti...

  3. Effects of stratospheric aerosol surface processes on the LLNL two-dimensional zonally averaged model

    International Nuclear Information System (INIS)

    We have investigated the effects of incorporating representations of heterogeneous chemical processes associated with stratospheric sulfuric acid aerosol into the LLNL two-dimensional, zonally averaged, model of the troposphere and stratosphere. Using distributions of aerosol surface area and volume density derived from SAGE 11 satellite observations, we were primarily interested in changes in partitioning within the Cl- and N- families in the lower stratosphere, compared to a model including only gas phase photochemical reactions

  4. Assessments of urban aerosol pollution in Moscow and its radiative effects

    OpenAIRE

    N. Ye. Chubarova; M. A. Sviridenkov; A. Smirnov; Holben, B. N.

    2010-01-01

    Simultaneous long-term measurements by the collocated AERONET CIMEL sun/sky photometers at the Moscow State University Meteorological Observatory (MSU MO) and at the Zvenigorod Scientific Station (ZSS) of the A. M. Obukhov Institute of Atmospheric Physics during September 2006–April 2009 provide the estimates of the effects of urban pollution on different aerosol properties in different seasons. The average difference in aerosol optical thickness between MO MSU and ZSS, which can characterize...

  5. Assessments of urban aerosol pollution in Moscow and its radiative effects

    OpenAIRE

    Chubarova, N. Y.; M. A. Sviridenkov; A. Smirnov; Holben, B. N.

    2011-01-01

    Simultaneous measurements by the collocated AERONET CIMEL sun/sky photometers at the Moscow State University Meteorological Observatory (MSU MO) and at the Zvenigorod Scientific Station (ZSS) of the A. M. Obukhov Institute of Atmospheric Physics during September 2006���April 2009 provide the estimates of the effects of urban pollution on various aerosol properties in different seasons. The average difference in aerosol optical thickness between MO MSU and ZSS, which can characterize the effec...

  6. Overview of the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES)

    Energy Technology Data Exchange (ETDEWEB)

    Zaveri, R. A.; Shaw, W. J.; Cziczo, D. J.; Schmid, B.; Ferrare, R. A.; Alexander, M. L.; Alexandrov, M.; Alvarez, R. J.; Arnott, W. P.; Atkinson, D. B.; Baidar, S.; Banta, R. M.; Barnard, J. C.; Beranek, J.; Berg, L. K.; Brechtel, F.; Brewer, W. A.; Cahill, J. F.; Cairns, B.; Cappa, C. D.; Chand, D.; China, S.; Comstock, J. M.; Dubey, M. K.; Easter, R. C.; Erickson, M. H.; Fast, J. D.; Floerchinger, C.; Flowers, B. A.; Fortner, E.; Gaffney, J. S.; Gilles, M. K.; Gorkowski, K.; Gustafson, W. I.; Gyawali, M.; Hair, J.; Hardesty, R. M.; Harworth, J. W.; Herndon, S.; Hiranuma, N.; Hostetler, C.; Hubbe, J. M.; Jayne, J. T.; Jeong, H.; Jobson, B. T.; Kassianov, E. I.; Kleinman, L. I.; Kluzek, C.; Knighton, B.; Kolesar, K. R.; Kuang, C.; Kubátová, A.; Langford, A. O.; Laskin, A.; Laulainen, N.; Marchbanks, R. D.; Mazzoleni, C.; Mei, F.; Moffet, R. C.; Nelson, D.; Obland, M. D.; Oetjen, H.; Onasch, T. B.; Ortega, I.; Ottaviani, M.; Pekour, M.; Prather, K. A.; Radney, J. G.; Rogers, R. R.; Sandberg, S. P.; Sedlacek, A.; Senff, C. J.; Senum, G.; Setyan, A.; Shilling, J. E.; Shrivastava, M.; Song, C.; Springston, S. R.; Subramanian, R.; Suski, K.; Tomlinson, J.; Volkamer, R.; Wallace, H. W.; Wang, J.; Weickmann, A. M.; Worsnop, D. R.; Yu, X. -Y.; Zelenyuk, A.; Zhang, Q.

    2012-01-01

    Substantial uncertainties still exist in the scientific understanding of the possible interactions between urban and natural (biogenic) emissions in the production and transformation of atmospheric aerosol and the resulting impact on climate change. The U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program’s Carbonaceous Aerosol and Radiative Effects Study (CARES) carried out in June 2010 in Central Valley, California, was a comprehensive effort designed to improve this understanding. The primary objective of the field study was to investigate the evolution of secondary organic and black carbon aerosols and their climate-related properties in the Sacramento urban plume as it was routinely transported into the forested Sierra Nevada foothills area. Urban aerosols and trace gases experienced significant physical and chemical transformations as they mixed with the reactive biogenic hydrocarbons emitted from the forest. Two heavily-instrumented ground sites – one within the Sacramento urban area and another about 40 km to the northeast in the foothills area – were set up to characterize the evolution of meteorological variables, trace gases, aerosol precursors, aerosol size, composition, and climate-related properties in freshly polluted and “aged” urban air. On selected days, the DOE G-1 aircraft was deployed to make similar measurements upwind and across the evolving Sacramento plume in the morning and again in the afternoon. The NASA B-200 aircraft, carrying remote sensing instruments, was also deployed to characterize the vertical and horizontal distribution of aerosols and aerosol optical properties within and around the plume. This overview provides: a) the scientific background and motivation for the study, b) the operational and logistical information pertinent to the execution of the study, c) an overview of key observations and initial findings from the aircraft and ground-based sampling platforms, and d) a roadmap of

  7. Effect of aerosol particle size on bronchodilatation with nebulised terbutaline in asthmatic subjects.

    Science.gov (United States)

    Clay, M M; Pavia, D; Clarke, S W

    1986-05-01

    The bronchodilatation achieved by the beta 2 agonist terbutaline sulphate given as nebulised aerosol from different devices has been measured in seven patients with mild asthma (mean FEV1 76% predicted) over two hours after inhalation. The subjects were studied on four occasions. On three visits they received 2.5 mg terbutaline delivered from three different types of nebuliser, selected on the basis of the size distribution of the aerosols generated; and on a fourth (control) visit no aerosol was given. The size distributions of the aerosols expressed in terms of their mass median diameter (MMD) were: A: MMD 1.8 microns; B: 4.6 microns; C: 10.3 microns. The aerosols were given under controlled conditions of respiratory rate and tidal volume to minimise intertreatment variation. Bronchodilator response was assessed by changes in FEV1, forced vital capacity (FVC), peak expiratory flow (PEF), and maximal flow after expiration of 50% and 75% FVC (Vmax50, Vmax25) from baseline (before aerosol) and control run values. For each pulmonary function index all three aerosols gave significantly better improvement over baseline than was seen in the control (p less than 0.05) and had an equipotent effect on FEV1, FVC, and PEF. Aerosol A (MMD 1.8 microns) produced significantly greater improvements in Vmax50 and Vmax25 than did B or C (p less than 0.05). These results suggest that for beta 2 agonists small aerosols (MMD less than 2 microns) might be advantageous in the treatment of asthma. PMID:3750243

  8. Amplification of ENSO effects on Indian summer monsoon by absorbing aerosols

    Science.gov (United States)

    Kim, Maeng-Ki; Lau, William K. M.; Kim, Kyu-Myong; Sang, Jeong; Kim, Yeon-Hee; Lee, Woo-Seop

    2016-04-01

    In this study, we present observational evidence, based on satellite aerosol measurements and MERRA reanalysis data for the period 1979-2011, indicating that absorbing aerosols can have strong influence on seasonal-to-interannual variability of the Indian summer monsoon rainfall, including amplification of ENSO effects. We find a significant correlation between ENSO (El Nino Southern Oscillation) and aerosol loading in April-May, with La Nina (El Nino) conditions favoring increased (decreased) aerosol accumulation over northern India, with maximum aerosol optical depth over the Arabian Sea and Northwestern India, indicative of strong concentration of dust aerosols transported from West Asia and Middle East deserts. Composite analyses based on a normalized aerosol index (NAI) show that high concentration of aerosol over northern India in April-May is associated with increased moisture transport, enhanced dynamically induced warming of the upper troposphere over the Tibetan Plateau, and enhanced rainfall over northern India and the Himalayan foothills during May-June, followed by a subsequent suppressed monsoon rainfall over all India, consistent with the elevated heat pump (EHP) hypothesis (Lau et al. in Clim Dyn 26:855-864, 2006. doi: 10.1007/s00382-006-0114-z). Further analyses from sub-sampling of ENSO years, with normal (1-σ) NAI over northern India respectively show that the EHP may lead to an amplification of the Indian summer monsoon response to ENSO forcing, particularly with respect to the increased rainfall over the Himalayan foothills, and the warming of the upper troposphere over the Tibetan Plateau. Our results suggest that absorbing aerosol, particular desert dusts can strongly modulate ENSO influence, and possibly play important roles as a feedback agent in climate change in Asian monsoon regions.

  9. DIRECT AND INDIRECT EFFECTS OF MICROBES ON TECHNETIUM INSOLUBILIZATION IN PADDY FIELDS

    Energy Technology Data Exchange (ETDEWEB)

    Ishii, N.; Tagami, K.; Uchida, S.

    2003-02-27

    Direct and indirect effects of microorganisms on technetium insolubilization in water covering waterlogged soils were studied. Seven soils were waterlogged and then the water covering the soils were collected for further tracer experiments. The samples in contact with air were incubated with 95mTcO4--at 25 C for 4 to 5 days. After incubation, the samples were sequentially separated into four fractions: one insoluble fraction (> 0.2 {micro}m) and three soluble fractions (TcO4 -, cationic, and other forms). The radioactivity of 95mTc in each fraction was measured with a NaI (Tl) scintillation counter. The insolubility of Tc was observed in the untreated samples. The maximum insolubilization radioactivity was 37% of the total radioactivity in P38, which was collected from a paddy field, gray lowland soil. Microscopic observations revealed that bacteria were the dominant species in the insoluble fraction of P38. For the other samples, less than 9% of the Tc was found in insoluble form. In order to clarify biological and nonbiological factor affecting the insolubility, a reducing agent or nutrients were added to the P38 sample. The amount of insoluble Tc was enhanced by the addition of nutrients, while the addition of the reducing agent resulted in a dramatic decrease in the amount of the insoluble Tc. Most of the 95mTcO4 - added to the filtered or autoclaved samples was present in the form of the pertechnetate anion, even in P38. The filtered and autoclaved samples contained metabolites and dead cell particles, respectively. These materials, therefore, did not affect the physicochemical changes in Tc. These results suggest that specific bacteria having the ability to render Tc insoluble even under not strictly anaerobic conditions directly contribute to the insolubility of Tc.

  10. Bio-aerosols in indoor environment: Composition, health effects and analysis

    Directory of Open Access Journals (Sweden)

    Srikanth Padma

    2008-01-01

    Full Text Available Bio-aerosols are airborne particles that are living (bacteria, viruses and fungi or originate from living organisms. Their presence in air is the result of dispersal from a site of colonization or growth. The health effects of bio-aerosols including infectious diseases, acute toxic effects, allergies and cancer coupled with the threat of bioterrorism and SARS have led to increased awareness on the importance of bio-aerosols. The evaluation of bio-aerosols includes use of variety of methods for sampling depending on the concentration of microorganisms expected. There have been problems in developing standard sampling methods, in proving a causal relationship and in establishing threshold limit values for exposures due to the complexity of composition of bio-aerosols, variations in human response to their exposure and difficulties in recovering microorganisms. Currently bio-aerosol monitoring in hospitals is carried out for epidemiological investigation of nosocomial infectious diseases, research into airborne microorganism spread and control, monitoring biohazardous procedures and use as a quality control measure. In India there is little awareness regarding the quality of indoor air, mould contamination in indoor environments, potential source for transmission of nosocomial infections in health care facilities. There is an urgent need to undertake study of indoor air, to generate baseline data and explore the link to nosocomial infections. This article is a review on composition, sources, modes of transmission, health effects and sampling methods used for evaluation of bio-aerosols, and also suggests control measures to reduce the loads of bio-aerosols.

  11. Bio-aerosols in indoor environment: composition, health effects and analysis.

    Science.gov (United States)

    Srikanth, Padma; Sudharsanam, Suchithra; Steinberg, Ralf

    2008-01-01

    Bio-aerosols are airborne particles that are living (bacteria, viruses and fungi) or originate from living organisms. Their presence in air is the result of dispersal from a site of colonization or growth. The health effects of bio-aerosols including infectious diseases, acute toxic effects, allergies and cancer coupled with the threat of bioterrorism and SARS have led to increased awareness on the importance of bio-aerosols. The evaluation of bio-aerosols includes use of variety of methods for sampling depending on the concentration of microorganisms expected. There have been problems in developing standard sampling methods, in proving a causal relationship and in establishing threshold limit values for exposures due to the complexity of composition of bio-aerosols, variations in human response to their exposure and difficulties in recovering microorganisms. Currently bio-aerosol monitoring in hospitals is carried out for epidemiological investigation of nosocomial infectious diseases, research into airborne microorganism spread and control, monitoring biohazardous procedures and use as a quality control measure. In India there is little awareness regarding the quality of indoor air, mould contamination in indoor environments, potential source for transmission of nosocomial infections in health care facilities. There is an urgent need to undertake study of indoor air, to generate baseline data and explore the link to nosocomial infections. This article is a review on composition, sources, modes of transmission, health effects and sampling methods used for evaluation of bio-aerosols, and also suggests control measures to reduce the loads of bio-aerosols. PMID:18974481

  12. Future vegetation-climate interactions in Eastern Siberia: an assessment of the competing effects of CO2 and secondary organic aerosols

    Science.gov (United States)

    Arneth, Almut; Makkonen, Risto; Olin, Stefan; Paasonen, Pauli; Holst, Thomas; Kajos, Maija K.; Kulmala, Markku; Maximov, Trofim; Miller, Paul A.; Schurgers, Guy

    2016-04-01

    Disproportional warming in the northern high latitudes and large carbon stocks in boreal and (sub)arctic ecosystems have raised concerns as to whether substantial positive climate feedbacks from biogeochemical process responses should be expected. Such feedbacks occur when increasing temperatures lead, for example, to a net release of CO2 or CH4. However, temperature-enhanced emissions of biogenic volatile organic compounds (BVOCs) have been shown to contribute to the growth of secondary organic aerosol (SOA), which is known to have a negative radiative climate effect. Combining measurements in Eastern Siberia with model-based estimates of vegetation and permafrost dynamics, BVOC emissions, and aerosol growth, we assess here possible future changes in ecosystem CO2 balance and BVOC-SOA interactions and discuss these changes in terms of possible climate effects. Globally, the effects of changes in Siberian ecosystem CO2 balance and SOA formation are small, but when concentrating on Siberia and the Northern Hemisphere the negative forcing from changed aerosol direct and indirect effects become notable - even though the associated temperature response would not necessarily follow a similar spatial pattern. While our analysis does not include other important processes that are of relevance for the climate system, the CO2 and BVOC-SOA interplay serves as an example for the complexity of the interactions between emissions and vegetation dynamics that underlie individual terrestrial processes and highlights the importance of addressing ecosystem-climate feedbacks in consistent, process-based model frameworks.

  13. Individual variation in behavioural plasticity: direct and indirect effects of boldness, exploration and sociability on habituation to predators in lizards

    OpenAIRE

    Rodríguez-Prieto, Iñaki; Martín, José; Fernández-Juricic, Esteban

    2010-01-01

    Little is known about the factors causing variation in behavioural plasticity and the interplay between personality and plasticity. Habituation to predators is a special case of behavioural plasticity. We investigated the direct and indirect effects of boldness, exploration and sociability traits on the habituation ability of Iberian wall lizards, considering exposure and sex effects. Individual boldness was consistent across several non-habituation contexts, but it did not significantly affe...

  14. Direct and indirect effects of invasion by the alien tree Ailanthus altissima on riparian plant communities and ecosystem multifunctionality

    OpenAIRE

    Constán Nava, Soraya; Soliveres, Santiago; Torices, Rubén; Serra, Lluís; Bonet Jornet, Andreu

    2015-01-01

    Most existing studies addressing the effects of invasive species on biodiversity focus on species richness ignoring better indicators of biodiversity and better predictors of ecosystem functioning such as the diversity of evolutionary histories (phylodiversity). Moreover, no previous study has separated the direct effect of alien plants on multiple ecosystem functions simultaneously (multifunctionality) from those indirect ones mediated by the decrease on biodiversity caused by alien plants. ...

  15. Components of the indirect effect in vaccine trials: identification of contagion and infectiousness effects

    OpenAIRE

    VanderWeele, Tyler J; Tchetgen Tchetgen, Eric J.; Halloran, M. Elizabeth

    2012-01-01

    Vaccination of one person may prevent the infection of another either because the vaccine prevents the first from being infected and from infecting the second, or because, even if the first person is infected, the vaccine may render the infection less infectious. We might refer to the first of these mechanisms as a contagion effect and the second as an infectiousness effect. In the simple setting of a randomized vaccine trial with households of size two, we use counterfactual theory under int...

  16. Absorption of aerosols above clouds from POLDER/PARASOL measurements and estimation of their Direct Radiative Effect

    Directory of Open Access Journals (Sweden)

    F. Peers

    2014-10-01

    Full Text Available The albedo of clouds and the aerosol absorption are key parameters to evaluate the direct radiative effect of an aerosol layer above clouds. While most of the retrievals of above clouds aerosol characteristics rely on assumptions on the aerosol properties, this study offers a new method to evaluate aerosol and cloud optical properties simultaneously (i.e. aerosol and cloud optical thickness, aerosol single scattering albedo and angström exponent. It is based on multi-angle total and polarized radiances both provided by the A-train satellite instrument POLDER – Polarization and Directionality of Earth Reflectances. The sensitivities brought by each kind of measurements are used in a complementary way. Polarization mostly translates scattering processes and is thus used to estimate the scattering aerosol optical thickness and the aerosol size. On the other hand, total radiances, together with the scattering properties of aerosols, are used to evaluate the absorption optical thickness of aerosols and the cloud optical thickness. In addition, a procedure has been developed to process the shortwave direct radiative effect of aerosols above clouds based on exact modeling. Besides the three case studies (i.e. biomass burning aerosols from Africa and Siberia and Saharan dust, both algorithms have been applied on the South East Atlantic Ocean and results have been averaged through August 2006. The mean direct radiative effect is found to be 33.5 W m−2. Finally, the effect of the heterogeneity of clouds has been investigated and reveals that it affects mostly the retrieval of the cloud optical thickness and not much the aerosols properties. The homogenous cloud assumption used in both the properties retrieval and the DRE processing leads to a slight underestimation of the DRE.

  17. Effects of reclaimed asphalt pavement on indirect tensile strength test of conditioned foamed asphalt mix

    International Nuclear Information System (INIS)

    This paper presents the results of Indirect Tensile Strength (ITS) Test for samples prepared with reclaimed asphalt pavement (RAP). Samples were conditioned in water at 25°C for 24 hours prior to testing. Results show that recycled aggregate from reclaimed asphalt pavement performs as well as virgin aggregate.

  18. Effects of reclaimed asphalt pavement on indirect tensile strength test of conditioned foamed asphalt mix

    Science.gov (United States)

    Yati Katman, Herda; Rasdan Ibrahim, Mohd; Yazip Matori, Mohd; Norhisham, Shuhairy; Ismail, Norlela

    2013-06-01

    This paper presents the results of Indirect Tensile Strength (ITS) Test for samples prepared with reclaimed asphalt pavement (RAP). Samples were conditioned in water at 25°C for 24 hours prior to testing. Results show that recycled aggregate from reclaimed asphalt pavement performs as well as virgin aggregate.

  19. Determination of aerosol properties from MAX-DOAS observations of the Ring effect

    Directory of Open Access Journals (Sweden)

    T. Wagner

    2009-03-01

    Full Text Available The first quantitative comparison of MAX-DOAS observations of the Ring effect with model simulations is presented. It is performed for a large variety of viewing geometries (solar zenith angles: 45° to 90°, elevation angles: 3°, 6°, 10°, 18°, 90°; three different azimuth angles, which allows a comprehensive test of our capabilities to measure and simulate the Ring effect. In addition to the Ring effect, also the observed O4 absorptions (optical densities and radiances are compared with model simulations. In general good agreement is found for all measured quantities. From several sensitivity studies it is found that for most measurement situations the aerosol optical depth has usually the strongest influence on the observed quantities, but also other aerosol properties like e.g. the vertical distribution have a significant effect. Typically, the qualitative dependence of the Ring effect on aerosol properties is very similar to that of the O4 absorption. This can be understood, since both quantities depend strongly on the light path length in the lower atmosphere. However, in specific cases, the observation of the Ring effect can provide complementary information to that retrieved from the O4 observations. This is e.g. possible for measurements at small relative azimuth angles, from which information on the asymmetry parameter can be derived. Observations at large solar zenith angle allow the retrieval of stratospheric aerosol properties, even in cases with very low aerosol optical depths. In addition, Ring effect observations in zenith direction are rather sensitive to the aerosol optical depth (in contrast to O4 observations, which might allow to retrieve information on aerosol properties from existing zenith UV data sets prior to the MAX-DOAS era.

  20. Aerosol activation properties and CCN closure during TCAP

    Science.gov (United States)

    Mei, F.; Tomlinson, J. M.; Shilling, J. E.; Wilson, J. M.; Zelenyuk, A.; Chand, D.; Comstock, J. M.; Hubbe, J.; Berg, L. K.; Schmid, B.

    2013-12-01

    The indirect effects of atmospheric aerosols currently remain the most uncertain components in forcing of climate change over the industrial period (IPCC, 2007). This large uncertainty is partially due to our incomplete understanding of the ability of particles to form cloud droplets under atmospherically relevant supersaturation. In addition, there is a large uncertainty in the aerosol optical depth (AOD) simulated by climate models near the North American coast and a wide variety in the types of clouds are observed over this region. The goal of the US Department of Energy Two Column Aerosol Project (TCAP) is to understand the processes responsible for producing and maintaining aerosol distributions and associated radiative and cloud forcing off the coast of North America. During the TCAP study, aerosol total number concentration, cloud condensation nuclei (CCN) spectra and aerosol chemical composition were in-situ measured from the DOE Gulfstream 1 (G-1) research aircraft during two Intensive Operations Periods (IOPs), one conducted in July 2012 and the other in February 2013. An overall aerosol size distribution was achieved by merging the observations from several instruments, including Ultra High Sensitivity Aerosol Spectrometer - Airborne (UHSAS-A, DMT), Passive Cavity Aerosol Spectrometer Probe (PCASP-200, DMT), and Cloud Aerosol Spectrometer (CAS, DMT). Aerosol chemical composition was characterized using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS, Aerodyne Inc.) and single particle mass spectrometer, mini-SPLAT. Based on the aerosol size distribution, CCN number concentration (characterized by a DMT dual column CCN counter with a range from 0.1% to 0.4%), and chemical composition, a CCN closure was obtained. The sensitivity of CCN closure to organic hygroscopicity was investigated. The differences in aerosol/CCN properties between two columns, and between two phases, will be discussed.

  1. Multi-wavelength measurements of aerosol optical absorption coefficients using a photoacoustic spectrometer

    International Nuclear Information System (INIS)

    The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on climate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength (405 nm, 532 nm, 780 nm) aerosol absorption meter based on photoacoustic spectroscopy (PAS) invovling a single cylindrical acoustic resonator is developed for measuring the aerosol optical absorption coefficients (OACs). A sensitivity of 1.3 Mm−1 (at 532 nm) is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Ångström exponent (AAE) for ambient aerosol are determined for characterizing the component of the ambient aerosol

  2. Aerosols, clouds and their climatic impacts

    Energy Technology Data Exchange (ETDEWEB)

    Kulmala, M.; Laaksonen, A.; Korhonen, P. [Helsinki Univ. (Finland). Dept. of Physics

    1995-12-31

    The increasing atmospheric concentrations of greenhouse gases such as carbon dioxide and methane may drive a significant warming of the earth`s climate. However, a topic of more recent attention is the possibility that increased atmospheric concentrations of aerosol particles might drive a cooling of the planet. There are two distinct cooling mechanisms related to the enhanced concentrations of aerosol particles: the increase in the direct reflection of solar radiation (the direct effect), and the increase in cloud reflectivity caused by greater numbers of cloud condensation nuclei available (the indirect effect). Aerosols and clouds play a major role in the scattering and absorption of radiation in the Earth`s atmosphere. Locally the net effect can vary because of different kinds of surfaces. But according to measurements, the global net effect of clouds (and aerosols) on the atmosphere is net cooling and thus in opposition to the effect of greenhouse gases. The prediction of the future evolution of the climate involves substantial uncertainties. Clouds have a major effect on the radiation balance of the Earth and the prediction of amount and radiative properties of clouds is very difficult. Also the formation mechanisms and residence times of aerosol particles in the atmosphere involve large uncertainties. Thus the most serious difficulties arise in the area of the physics of clouds and aerosols

  3. Global two-channel AVHRR aerosol climatology: effects of stratospheric aerosols and preliminary comparisons with MODIS and MISR retrievals

    Energy Technology Data Exchange (ETDEWEB)

    Geogdzhayev, Igor V. [Department of Applied Physics and Applied Mathematics, Columbia University, 2880 Broadway, New York, NY 10025 (United States); NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 (United States); Mishchenko, Michael I. [NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 (United States)]. E-mail: crmim@giss.nasa.gov; Liu Li [NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 (United States); Department of Earth and Environmental Sciences, Columbia University, 2880 Broadway, New York, NY 10025 (United States); Remer, Lorraine [NASA Goddard Space Flight Center, Code 913, Greenbelt, MD 20771 (United States)

    2004-10-15

    We present an update on the status of the global climatology of the aerosol column optical thickness and Angstrom exponent derived from channel-1 and -2 radiances of the Advanced Very High Resolution Radiometer (AVHRR) in the framework of the Global Aerosol Climatology Project (GACP). The latest version of the climatology covers the period from July 1983 to September 2001 and is based on an adjusted value of the diffuse component of the ocean reflectance as derived from extensive comparisons with ship sun-photometer data. We use the updated GACP climatology and Stratospheric Aerosol and Gas Experiment (SAGE) data to analyze how stratospheric aerosols from major volcanic eruptions can affect the GACP aerosol product. One possible retrieval strategy based on the AVHRR channel-1 and -2 data alone is to infer both the stratospheric and the tropospheric aerosol optical thickness while assuming fixed microphysical models for both aerosol components. The second approach is to use the SAGE stratospheric aerosol data in order to constrain the AVHRR retrieval algorithm. We demonstrate that the second approach yields a consistent long-term record of the tropospheric aerosol optical thickness and Angstrom exponent. Preliminary comparisons of the GACP aerosol product with MODerate resolution Imaging Spectrometer (MODIS) and Multiangle Imaging Spectro-Radiometer aerosol retrievals show reasonable agreement, the GACP global monthly optical thickness being lower than the MODIS one by approximately 0.03. Larger differences are observed on a regional scale. Comparisons of the GACP and MODIS Angstrom exponent records are less conclusive and require further analysis.

  4. Indirect effects of TiO2 nanoparticle on neuron-glial cell interactions.

    Science.gov (United States)

    Hsiao, I-Lun; Chang, Chia-Cheng; Wu, Chung-Yi; Hsieh, Yi-Kong; Chuang, Chun-Yu; Wang, Chu-Fang; Huang, Yuh-Jeen

    2016-07-25

    Although, titanium dioxide nanoparticles (TiO2NPs) are nanomaterials commonly used in consumer products, little is known about their hazardous effects, especially on central nervous systems. To examine this issue, ALT astrocyte-like, BV-2 microglia and differentiated N2a neuroblastoma cells were exposed to 6 nm of 100% anatase TiO2NPs. A lipopolysaccharide (LPS) was pre-treated to activate glial cells before NP treatment for mimicking NP exposure under brain injury. We found that ALT and BV-2 cells took up more NPs than N2a cells and caused lower cell viability. TiO2NPs induced IL-1β in the three cell lines and IL-6 in N2a. LPS-activated BV-2 took up more TiO2NPs than normal BV-2 and released more intra/extracellular reactive oxygen species (ROS), IL-1β, IL-6 and MCP-1 than did activated BV-2. Involvement of clathrin- and caveolae-dependent endocytosis in ALT and clathrin-dependent endocytosis and phagocytosis in BV-2 both had a slow NP translocation rate to lysosome, which may cause slow ROS production (after 24 h). Although TiO2NPs did not directly cause N2a viability loss, by indirect NP exposure to the bottom chamber of LPS-activated BV-2 in the Transwell system, they caused late apoptosis and loss of cell viability in the upper N2a chamber due to H2O2 and/or TNF-α release from BV-2. However, none of the adverse effects in N2a or BV-2 cells was observed when TiO2NPs were exposed to ALT-N2a or ALT-BV-2 co-culture. These results demonstrate that neuron damage can result from TiO2NP-mediated ROS and/or cytokines release from microglia, but not from astrocytes. PMID:27216632

  5. Direct and indirect effects of ammonia, ammonium and nitrate on phosphatase activity and carbon fluxes from decomposing litter in peatland

    International Nuclear Information System (INIS)

    Here we investigate the response of soils and litter to 5 years of experimental additions of ammonium (NH4), nitrate (NO3), and ammonia (NH3) to an ombrotrophic peatland. We test the importance of direct (via soil) and indirect (via litter) effects on phosphatase activity and efflux of CO2. We also determined how species representing different functional types responded to the nitrogen treatments. Our results demonstrate that additions of NO3, NH4 and NH3 all stimulated phosphatase activity but the effects were dependent on species of litter and mechanism (direct or indirect). Deposition of NH3 had no effect on efflux of CO2 from Calluna vulgaris litter, despite it showing signs of stress in the field, whereas both NO3 and NH4 reduced CO2 fluxes. Our results show that the collective impacts on peatlands of the three principal forms of nitrogen in atmospheric deposition are a result of differential effects and mechanisms on individual components. - We found that nitrogen deposition affects microbial activity associated with litter through both indirect and direct mechanisms, but these effects were dependent on the chemical form of inorganic nitrogen compounds.

  6. Indirect effects of predators control herbivore richness and abundance in a benthic eelgrass (Zostera marina) mesograzer community.

    Science.gov (United States)

    Amundrud, Sarah L; Srivastava, Diane S; O'Connor, Mary I

    2015-07-01

    Herbivore communities can be sensitive to changes in predator pressure (top-down effects) and resource availability (bottom-up effects) in a wide range of systems. However, it remains unclear whether such top-down and bottom-up effects reflect direct impacts of predators and/or resources on herbivores, or are indirect, reflecting altered interactions among herbivore species. We quantified direct and indirect effects of bottom-up and top-down processes on an eelgrass (Zostera marina) herbivore assemblage. In a field experiment, we factorially manipulated water column nutrients (with Osmocote(™) slow-release fertilizer) and predation pressure (with predator exclusion cages) and measured the effects on herbivore abundance, richness and beta diversity. We examined likely mechanisms of community responses by statistically exploring the response of individual herbivore species to trophic manipulations. Predators increased herbivore richness and total abundance, in both cases through indirect shifts in community composition. Increases in richness occurred through predator suppression of common gammarid amphipod species (Monocorophium acherusicum and Photis brevipes), permitting the inclusion of rarer gammarid species (Aoroides columbiae and Pontogeneia rostrata). Increased total herbivore abundance reflected increased abundance of a caprellid amphipod species (Caprella sp.), concurrent with declines in the abundance of other common species. Furthermore, predators decreased beta diversity by decreasing variability in Caprella sp. abundance among habitat patches. Osmocote(™) fertilization increased nutrient concentrations locally, but nutrients dissipated to background levels within 3 m of the fertilizer. Nutrient addition weakly affected the herbivore assemblage, not affecting richness and increasing total abundance by increasing one herbivore species (Caprella sp.). Nutrient addition did not affect beta diversity. We demonstrated that assemblage-level effects of

  7. Satellite-based estimate of aerosol direct radiative effect over the South-East Atlantic

    Directory of Open Access Journals (Sweden)

    L. Costantino

    2013-09-01

    Full Text Available The net effect of aerosol Direct Radiative Forcing (DRF is the balance between the scattering effect that reflects solar radiation back to space (cooling, and the absorption that decreases the reflected sunlight (warming. The amplitude of these two effects and their balance depends on the aerosol load, its absorptivity, the cloud fraction and the respective position of aerosol and cloud layers. In this study, we use the information provided by CALIOP (CALIPSO satellite and MODIS (AQUA satellite instruments as input data to a Rapid Radiative Transfer Model (RRTM and quantify the shortwave (SW aerosol direct atmospheric forcing, over the South-East Atlantic. The combination of the passive and active measurements allows estimates of the horizontal and vertical distributions of the aerosol and cloud parameters. We use a parametrization of the Single Scattering Albedo (SSA based on the satellite-derived Angstrom coefficient. The South East Atlantic is a particular region, where bright stratocumulus clouds are often topped by absorbing smoke particles. Results from radiative transfer simulations confirm the similar amplitude of the cooling effect, due to light scattering by the aerosols, and the warming effect, due to the absorption by the same particles. Over six years of satellite retrievals, from 2005 to 2010, the South-East Atlantic all-sky SW DRF is −0.03 W m−2, with a spatial standard deviation of 8.03 W m−2. In good agreement with previous estimates, statistics show that a cloud fraction larger than 0.5 is generally associated with positive all-sky DRF. In case of cloudy-sky and aerosol located only above the cloud top, a SSA larger than 0.91 and cloud optical thickness larger than 4 can be considered as threshold values, beyond which the resulting radiative forcing becomes positive.

  8. A Thermal Desorption Chemical Ionization Mass Spectrometer for the In Situ Measurement of Aerosol Organic Compounds

    Science.gov (United States)

    Thornberry, T.; Murphy, D. M.; Lovejoy, E. R.

    2005-12-01

    Organic material has been observed to comprise a significant fraction of organic aerosol mass in many regions of the troposphere. The organic compounds that comprise the organic fraction of atmospheric aerosol have the potential to affect the radiative and microphysical properties of the aerosol, with concomitant impacts on the role of the aerosol in climate forcing through direct and indirect effects. Knowledge of the organic compounds in atmospheric aerosols and their spatial distribution is needed to determine their effect on aerosol properties as well as to elucidate the role of aerosols in the chemistry of the atmosphere. The speciated measurement of aerosol organic compounds poses a significant experimental challenge due to the complexity and large number of organic species, and the low concentration at which individual species are present. A prototype instrument has been designed and built to make in situ speciated measurements of aerosol organic compounds. The instrument is composed of an aerosol collection/thermal desorption inlet coupled to a custom chemical ionization ion trap mass spectrometer. Aerosols are collected over a variable time by impaction on a target stage. The stage is then rapidly heated to volatilize the organic compounds into a small flow of helium carrier gas and conveyed to an ion-molecule reaction drift tube where proton transfer from H3O+ is used to softly ionize organic species. The ionized analyte molecules are then trapped and mass analyzed using a quadrupole ion trap. Results from preliminary experiments using laboratory-generated aerosol will be discussed

  9. Characteristics of regional aerosols: Southern Arizona and eastern Pacific Ocean

    Science.gov (United States)

    Prabhakar, Gouri

    Atmospheric aerosols impact the quality of our life in many direct and indirect ways. Inhalation of aerosols can have harmful effects on human health. Aerosols also have climatic impacts by absorbing or scattering solar radiation, or more indirectly through their interactions with clouds. Despite a better understanding of several relevant aerosol properties and processes in the past years, they remain the largest uncertainty in the estimate of global radiative forcing. The uncertainties arise because although aerosols are ubiquitous in the Earth's atmosphere they are highly variable in space, time and their physicochemical properties. This makes in-situ measurements of aerosols vital in our effort towards reducing uncertainties in the estimate of global radiative forcing due to aerosols. This study is an effort to characterize atmospheric aerosols at a regional scale, in southern Arizona and eastern Pacific Ocean, based on ground and airborne observations of aerosols. Metals and metalloids in particles with aerodynamic diameter (Dp) smaller than 2.5 μm are found to be ubiquitous in southern Arizona. The major sources of the elements considered in the study are identified to be crustal dust, smelting/mining activities and fuel combustion. The spatial and temporal variability in the mass concentrations of these elements depend both on the source strength and meteorological conditions. Aircraft measurements of aerosol and cloud properties collected during various field campaigns over the eastern Pacific Ocean are used to study the sources of nitrate in stratocumulus cloud water and the relevant processes. The major sources of nitrate in cloud water in the region are emissions from ships and wildfires. Different pathways for nitrate to enter cloud water and the role of meteorology in these processes are examined. Observations of microphysical properties of ambient aerosols in ship plumes are examined. The study shows that there is an enhancement in the number

  10. Incremental Reactivity Effects on Secondary Organic Aerosol Formation in Urban Atmospheres with and without Biogenic Influence

    Science.gov (United States)

    Kacarab, Mary; Li, Lijie; Carter, William P. L.; Cocker, David R., III

    2016-04-01

    Two different surrogate mixtures of anthropogenic and biogenic volatile organic compounds (VOCs) were developed to study secondary organic aerosol (SOA) formation at atmospheric reactivities similar to urban regions with varying biogenic influence levels. Environmental chamber simulations were designed to enable the study of the incremental aerosol formation from select anthropogenic (m‑Xylene, 1,2,4-Trimethylbenzene, and 1-Methylnaphthalene) and biogenic (α-pinene) precursors under the chemical reactivity set by the two different surrogate mixtures. The surrogate reactive organic gas (ROG) mixtures were based on that used to develop the maximum incremental reactivity (MIR) factors for evaluation of O3 forming potential. Multiple incremental aerosol formation experiments were performed in the University of California Riverside (UCR) College of Engineering Center for Environmental Research and Technology (CE-CERT) dual 90m3 environmental chambers. Incremental aerosol yields were determined for each of the VOCs studied and compared to yields found from single precursor studies. Aerosol physical properties of density, volatility, and hygroscopicity were monitored throughout experiments. Bulk elemental chemical composition from high-resolution time of flight aerosol mass spectrometer (HR-ToF-AMS) data will also be presented. Incremental yields and SOA chemical and physical characteristics will be compared with data from previous single VOC studies conducted for these aerosol precursors following traditional VOC/NOx chamber experiments. Evaluation of the incremental effects of VOCs on SOA formation and properties are paramount in evaluating how to best extrapolate environmental chamber observations to the ambient atmosphere and provides useful insights into current SOA formation models. Further, the comparison of incremental SOA from VOCs in varying surrogate urban atmospheres (with and without strong biogenic influence) allows for a unique perspective on the impacts

  11. Near ultraviolet radiation (280-400 nm): Direct and indirect effects on microbial pathogens

    International Nuclear Information System (INIS)

    Responses of pigmented pathogenic fungi and E. coli strains differing in DNA repair and catalase proficiency to direct and indirect effects of ultraviolet radiation were evaluated. Pigments in the four fungal pathogens of Citrus differed in their ability to protect against direct UV and damage by UV-A -mediated phototoxins of both host and non-host origin. UV-A and UV-B did not inactivate the fungal species. Differential protection in wild type strains of the two Fusarium spp. and in the wild type strains of the two Penicilium spp. against UV-C was observed. Wild type and mutants with altered coloration in Penicilium spp. protected to varying extent against both α-T and 8-MOP in the presence of UV-A. UV-B irradiation of E. coli resulted in inactivation of strains deficient in DNA excision repair. Plasmid DNA damaged in vitro by UV-B from lamp systems as well as by sunlight, and transformed in vivo into bacterial cells lacking specific nucleases showed reduced transformation in DNA excision repair strains. UV-B enriched wavelengths isolated from a solar simulator affected plasmid DNA in a similar manner as UV-B from lamp systems. Sunlight, however affected the membrane of whole cells. Concentration of foliar furanocoumarins of Citrus jambhiri decreased with UV-B irradiation. Phototoxicity to Fusarium spp. was accounted for, in part, by furanocoumarins, psoralen and bergapten (5-MOP) and others. Pure psoralen and 5-MOP affected both Fusarium spp. similarly and carotenoids protected only partially in the wild type strains. Citrus targetted the cell membrane in Fusarium spp.l and in E. coli strains; carotenoids in both of which protected against such damage. Loss in structural integrity of plasmid DNA when treated with citral and UV-A correlated with loss in transforming activity. Biological damage to membrane and DNA was due to the production of hydrogen peroxide. Fruit-rot pathogens Penicilium spp. were not affected by either furanocoumarins or citrals

  12. Effective aerosol optical depth from pyranometer measurements of surface solar radiation (global radiation at Thessaloniki, Greece

    Directory of Open Access Journals (Sweden)

    A. V. Lindfors

    2013-04-01

    Full Text Available Pyranometer measurements of the solar surface radiation (SSR are available at many locations worldwide, often as long time series covering several decades into the past. These data constitute a potential source of information on the atmospheric aerosol load. Here, we present a method for estimating the aerosol optical depth (AOD using pyranometer measurements of the SSR together with total water vapor column information. The method, which is based on radiative transfer simulations, was developed and tested using recent data from Thessaloniki, Greece. The effective AOD calculated using this method was found to agree well with co-located AERONET measurements, exhibiting a correlation coefficient of 0.9 with 2/3 of the data found within ±20% or ±0.05 of the AERONET AOD. This is similar to the performance of current satellite aerosol methods. Differences in the AOD as compared to AERONET can be explained by variations in the aerosol properties of the atmosphere that are not accounted for in the idealized settings used in the radiative transfer simulations, such as variations in the single scattering albedo and Ångström exponent. Furthermore, the method is sensitive to calibration offsets between the radiative transfer simulations and the pyranometer SSR. The method provides an opportunity of extending our knowledge of the atmospheric aerosol load to locations and times not covered by dedicated aerosol measurements.

  13. Effective aerosol optical depth from pyranometer measurements of surface solar radiation (global radiation at Thessaloniki, Greece

    Directory of Open Access Journals (Sweden)

    A. V. Lindfors

    2012-12-01

    Full Text Available Pyranometer measurements of the solar surface radiation (SSR are available at many locations worldwide, often as long time series covering several decades into the past. These data constitute a potential source of information on the atmospheric aerosol load. Here, we present a method for estimating the aerosol optical depth (AOD using pyranometer measurements of the SSR together with total water vapor column information. The method, which is based on radiative transfer simulations, was developed and tested using recent data from Thessaloniki, Greece. The effective AOD calculated using this method was found to agree well with co-located AERONET measurements, exhibiting a correlation coefficient of 0.9 with 2/3 of the data found within ±20% or ±0.05 of the AERONET AOD. This is similar to the performance of current satellite aerosol methods. Differences in the AOD as compared to AERONET can be explained by variations in the aerosol properties of the atmosphere that are not accounted for in the idealized settings used in the radiative transfer simulations, such as variations in the single scattering albedo and Ångström exponent. Furthermore, the method is sensitive to calibration offsets between the radiative transfer simulations and the pyranometer SSR. The method provides an opportunity of extending our knowledge of the atmospheric aerosol load to locations and times not covered by dedicated aerosol measurements.

  14. Effectiveness of direct and indirect radionuclide cystography in detecting vesicoureteral reflux

    International Nuclear Information System (INIS)

    A modified of the direct radionuclide cystography technique to include filling, voiding, and postvoiding phases of the examination permitted a simulated comparison between direct and indirect radionuclide cystography. One hundred thirty-seven examples of reflux were documented with this technique. Of these, 96 instances of reflux (70 percent) were recorded during two or more phases and thus would have been detected by either technique. Twenty-nine examples (21 percent) were only detected during filling and thus would have been missed by the indirect radionuclide technique and by some roentgenographic techniques. Only 12 examples (9 percent) were detected during the voiding phase only. The modified direct method of radionuclide cystography, which continuously monitors the urinary tracts during filling, voiding, and postvoiding, is offered as the best current technique for assessing visicoureteral reflus

  15. The Indirect Effects of Maternal Emotion Socialization on Friendship Quality in Middle Childhood

    OpenAIRE

    Blair, Bethany L.; Perry, Nicole B.; O’Brien, Marion; Calkins, Susan D.; Keane, Susan P.; Shanahan, Lilly

    2013-01-01

    Emotion development processes have long been linked to social competence in early childhood but rarely have these associations been examined in middle childhood or with relational outcomes. Guided by theories of interpersonal relationships and emotion socialization, the current study was designed to fill these gaps by examining a longitudinal process model indirectly linking emotion development to friendship quality. Data were drawn from 336 children (179 girls, 65% White), their mothers, and...

  16. Indirect and direct business models and their effects on performance in IT companies

    OpenAIRE

    Sthen, Kristoffer

    2014-01-01

    This thesis studies financial performance data for Swedish publically traded information technology companies over five years beginning 2008 to 2012. This thesis examines performance for two types of business models: so called direct business models and indirect business models. The performance data is used to determine if there are any differences in financial performance. The analysis shows that companies using direct business models have a significantly lower financial performance than com...

  17. Direct and Indirect Effects of Psychological Contract Breach on Academicians’ Turnover Intention in Turkey

    OpenAIRE

    Buyukyilmaz, Ozan; Ahmet F. CAKMAK

    2013-01-01

    This study aims to investigate the assumed direct and indirect relationships between psychological contract breach and turnover intention through psychological contract violation and perceived organizational support. Data for the sample was collected from 570 academicians from a variety of universities in Turkey. Hierarchical regression analyses were conducted to test the hypotheses. The results show that psychological contract breach was positively related to turnover intention and psycholog...

  18. Fertilizer management effects on nitrate leaching and indirect nitrous oxide emissions in irrigated potato production.

    Science.gov (United States)

    Venterea, Rodney T; Hyatt, Charles R; Rosen, Carl J

    2011-01-01

    Potato ( L.) is a N-intensive crop, with high potential for nitrate (NO) leaching, which can contribute to both water contamination and indirect nitrous oxide (NO) emissions. Two approaches that have been considered for reducing N losses include conventional split application (CSA) of soluble fertilizers and single application of polymer-coated urea (PCU). The objectives of this study were to: (i) compare NO leaching using CSA and two PCUs (PCU-1 and PCU-2), which differed in their polymer formulations, and (ii) use measured NO leaching rates and published emissions factors to estimate indirect NO emissions. Averaged over three growing seasons (2007-2009), NO leaching rates were not significantly different among the three fertilizer treatments. Using previously reported direct NO emissions data from the same experiment, total direct plus indirect growing season NO emissions with PCU-1 were estimated to be 30 to 40% less than with CSA. However, PCU-1 also resulted in greater residual soil N after harvest in 2007 and greater soil-water NO in the spring following the 2008 growing season. These results provide evidence that single PCU applications for irrigated potato production do not increase growing season NO leaching compared with multiple split applications of soluble fertilizers, but have the potential to increase N losses after the growing season and into the following year. Estimates of indirect NO emissions ranged from 0.8 to 64% of direct emissions, depending on what value was assumed for the emission factor describing off-site conversion of NO to NO. Thus, our results also demonstrate how more robust models are needed to account for off-site conversion of NO to NO, since current emission factor models have an enormous degree of uncertainty. PMID:21712579

  19. Diversification Effects of Indirect Real Estate In A Mixed Asset Portfolio - The Malaysia Experience

    OpenAIRE

    A. Mohd Nasir

    2009-01-01

    "The high percentage of world investable wealth held in property coupled with price volatility and poor returns in the equity trading market have make investors turn to property for higher return. With the introduction of Modern Portfolio Theory, portfolio investments have become the norm whereby investors seek to achieve higher portfolio returns at a given risk level or lowest risk at a given level of return. The intent of this study is to present the benefits of including indirect real esta...

  20. Dynamics and Biocontrol: The Indirect Effects of a Predator Population on a Host-Vector Disease Model

    OpenAIRE

    Fengyan Zhou; Hongxing Yao

    2014-01-01

    A model of the interactions among a host population, an insect-vector population, which transmits virus from hosts to hosts, and a vector predator population is proposed based on virus-host, host-vector, and prey (vector)-enemy theories. The model is investigated to explore the indirect effect of natural enemies on host-virus dynamics by reducing the vector densities, which shows the basic reproduction numbers ${R}_{01}$ (without predators) and ${R}_{02}$ (with predators) that provide thresho...

  1. Effect of indirect ohmic heating on quality of ready-to-eat pineapple packed in plastic pouch

    OpenAIRE

    Hoang Pham; Weerachet Jittanit; Tanaboon Sajjaanantakul

    2014-01-01

    Ready-to-eat fruits packed in sealed containers are highly perishable due to their intrinsic characteristics and lack of full thermal process. Ohmic heating has the advantages of rapid liquid heating through electrical current. The aim of this research was to investigate the effect of indirect ohmic heating on pH, total soluble solids, polyphenol oxidase activity, color and texture of ready-to-eat pineapple packed in a polypropylene pouch with 1% calcium chloride and 0.3% ascorbic ac...

  2. Enhancement factors for resuspended aerosol radioactivity: Effects of topsoil disturbance

    International Nuclear Information System (INIS)

    The enhancement factor for airborne radionuclides resuspended by wind is defined as the ratio of the activity density (Bq g-1) in the aerosol to the activity density in the underlying surface of contaminated soil. Enhancement factors are useful for assessment of worst-case exposure scenarios and transport conditions, and are one of the criteria for setting environmental standards for radioactivity in soil. This paper presents results of experimental studies where resuspension of 239Pu was measured when air concentrations were equilibrated to the soil surface. Enhancement factors were observed for several types of man-made disturbances (bulldozer-blading, soil raking, vacuum-cleaning) and natural disturbances (springtime thaw, soil-drying, wildfire). For some cases, enhancement factors are compared over range of geographical locations (Bikini Atoll, California, Nevada, and South Carolina). The particle-size distributions of aerosol activity are compared to particle-size distributions of the underlying soil

  3. Interaction effects between sender and receiver processes in indirect transmission of Campylobacter jejuni between broilers

    Directory of Open Access Journals (Sweden)

    van Bunnik Bram AD

    2012-07-01

    Full Text Available Abstract Background Infectious diseases in plants, animals and humans are often transmitted indirectly between hosts (or between groups of hosts, i.e. via some route through the environment instead of via direct contacts between these hosts. Here we study indirect transmission experimentally, using transmission of Campylobacter jejuni (C. jejuni between spatially separated broilers as a model system. We distinguish three stages in the process of indirect transmission; (1 an infectious “sender” excretes the agent, after which (2 the agent is transported via some route to a susceptible “receiver”, and subsequently (3 the receiver becomes colonised by the agent. The role of the sender and receiver side (stage 1 and stage 3 was studied here by using acidification of the drinking water as a modulation mechanism. Results In the experiment one control group and three treatment groups were monitored for the presence of C. jejuni by taking daily cloacal swabs. The three treatments consisted of acidification of the drinking water of the inoculated animals (the senders, acidification of the drinking water of the susceptible animals (the receivers or acidification of the drinking water of both inoculated and susceptible animals. In the control group 12 animals got colonised out of a possible 40, in each treatment groups 3 animals out of a possible 40 were found colonised with C. jejuni. Conclusions The results of the experiments show a significant decrease in transmission rate (β between the control groups and treatment groups (p

  4. Effect of humidity on aerosolization of micronized drugs.

    Science.gov (United States)

    Young, Paul M; Price, Robert; Tobyn, Michael J; Buttrum, Mark; Dey, Fiona

    2003-10-01

    The variation of aerosolization with humidity for three micronized drugs used in the treatment of asthma was evaluated by using in vitro methods. Micronized samples of disodium cromoglycate (DSCG), salbutamol sulphate, and triamcinolone acetonide (TAA) were stored for 12hr at 15, 30, 45, 60, and 75% relative humidity (RH). A suitable "reservoir" dry powder inhaler was loaded and tested by using a twin-stage impinger at each specific humidity. The aerosolization efficiency of all three micronized drugs was affected by variations in humidity. The percentage of the delivered dose and the fine particle fraction of the loaded dose (FPFLD) for both DSCG and salbutamol sulphate decreased with increasing humidity; with the largest decrease in FPFLD occurring between 45% and 60% RH for DSCG and 60% to 75% RH for salbutamol sulphate. These observations suggest that the adhesion properties for both DSCG and salbutamol sulphate, which govern the aerosolization efficiency, are predominately influenced by capillary interactions. In contrast, the FPFLD for TAA significantly increased as the humidity increased over the range 15% to 75% RH, suggesting that triboelectric forces predominate particle-particle interactions. These variations in drug particulate behavior highlight the importance of an individual formulation approach when developing dry powder inhalation systems. PMID:14606660

  5. Radiative effects of tropospheric aerosols on the evolution of the atmospheric boundary layer and its feedback on the haze formation

    Science.gov (United States)

    Wei, Chao; Su, Hang; Cheng, Yafang

    2016-04-01

    Planetary boundary layer (PBL) plays a key role in air pollution dispersion and influences day-to-day air quality. Some studies suggest that high aerosol loadings during severe haze events may modify PBL dynamics by radiative effects and hence enhance the development of haze. This study mainly investigates the radiative effects of tropospheric aerosols on the evolution of the atmospheric boundary layer by conducting simulations with Weather Research and Forecasting single-column model (WRF-SCM). We find that high aerosol loading in PBL depressed boundary layer height (PBLH). But the magnitude of the changes of PBLH after adding aerosol loadings in our simulations are small and can't explain extreme high aerosol concentrations observed. We also investigate the impacts of the initial temperature and moisture profiles on the evolution of PBL. Our studies show that the impact of the vertical profile of moisture is comparable with aerosol effects.

  6. Impacts of increasing the aerosol complexity in the Met Office global numerical weather prediction model

    Science.gov (United States)

    Mulcahy, J. P.; Walters, D. N.; Bellouin, N.; Milton, S. F.

    2014-05-01

    The inclusion of the direct and indirect radiative effects of aerosols in high-resolution global numerical weather prediction (NWP) models is being increasingly recognised as important for the improved accuracy of short-range weather forecasts. In this study the impacts of increasing the aerosol complexity in the global NWP configuration of the Met Office Unified Model (MetUM) are investigated. A hierarchy of aerosol representations are evaluated including three-dimensional monthly mean speciated aerosol climatologies, fully prognostic aerosols modelled using the CLASSIC aerosol scheme and finally, initialised aerosols using assimilated aerosol fields from the GEMS project. The prognostic aerosol schemes are better able to predict the temporal and spatial variation of atmospheric aerosol optical depth, which is particularly important in cases of large sporadic aerosol events such as large dust storms or forest fires. Including the direct effect of aerosols improves model biases in outgoing long-wave radiation over West Africa due to a better representation of dust. However, uncertainties in dust optical properties propagate to its direct effect and the subsequent model response. Inclusion of the indirect aerosol effects improves surface radiation biases at the North Slope of Alaska ARM site due to lower cloud amounts in high-latitude clean-air regions. This leads to improved temperature and height forecasts in this region. Impacts on the global mean model precipitation and large-scale circulation fields were found to be generally small in the short-range forecasts. However, the indirect aerosol effect leads to a strengthening of the low-level monsoon flow over the Arabian Sea and Bay of Bengal and an increase in precipitation over Southeast Asia. Regional impacts on the African Easterly Jet (AEJ) are also presented with the large dust loading in the aerosol climatology enhancing of the heat low over West Africa and weakening the AEJ. This study highlights the

  7. Impacts of increasing the aerosol complexity in the Met Office global NWP model

    Science.gov (United States)

    Mulcahy, J. P.; Walters, D. N.; Bellouin, N.; Milton, S. F.

    2013-11-01

    Inclusion of the direct and indirect radiative effects of aerosols in high resolution global numerical weather prediction (NWP) models is being increasingly recognised as important for the improved accuracy of short-range weather forecasts. In this study the impacts of increasing the aerosol complexity in the global NWP configuration of the Met Office Unified Model (MetUM) are investigated. A hierarchy of aerosol representations are evaluated including three dimensional monthly mean speciated aerosol climatologies, fully prognostic aerosols modelled using the CLASSIC aerosol scheme and finally, initialised aerosols using assimilated aerosol fields from the GEMS project. The prognostic aerosol schemes are better able to predict the temporal and spatial variation of atmospheric aerosol optical depth, which is particularly important in cases of large sporadic aerosol events such as large dust storms or forest fires. Including the direct effect of aerosols improves model biases in outgoing longwave radiation over West Africa due to a better representation of dust. However, uncertainties in dust optical properties propogate to its direct effect and the subsequent model response. Inclusion of the indirect aerosol effects improves surface radiation biases at the North Slope of Alaska ARM site due to lower cloud amounts in high latitude clean air regions. This leads to improved temperature and height forecasts in this region. Impacts on the global mean model precipitation and large-scale circulation fields were found to be generally small in the short range forecasts. However, the indirect aerosol effect leads to a strengthening of the low level monsoon flow over the Arabian Sea and Bay of Bengal and an increase in precipitation over Southeast Asia. Regional impacts on the African Easterly Jet (AEJ) are also presented with the large dust loading in the aerosol climatology enhancing of the heat low over West Africa and weakening the AEJ. This study highlights the importance

  8. Evaluate and characterize mechanisms controlling transport, fate, and effects of army smokes in the aerosol wind tunnel: Transport, transformations, fate, and terrestrial ecological effects of hexachloroethane obscurant smokes

    Energy Technology Data Exchange (ETDEWEB)

    Cataldo, D.A.; Ligotke, M.W.; Bolton, H. Jr.; Fellows, R.J.; Van Voris, P.; McVeety, B.D.; Li, Shu-mei W.; McFadden, K.M.

    1989-09-01

    The terrestrial transport, chemical fate, and ecological effects of hexachloroethane (HC) smoke were evaluated under controlled wind tunnel conditions. The primary objectives of this research program are to characterize and assess the impacts of smoke and obscurants on: (1) natural vegetation characteristic of US Army training sites in the United States; (2) physical and chemical properties of soils representative of these training sites; and (3) soil microbiological and invertebrate communities. Impacts and dose/responses were evaluated based on exposure scenarios, including exposure duration, exposure rate, and sequential cumulative dosing. Key to understanding the environmental impacts of HC smoke/obscurants is establishing the importance of environmental parameters such as relative humidity and wind speed on airborne aerosol characteristics and deposition to receptor surfaces. Direct and indirect biotic effects were evaluated using five plant species and two soil types. HC aerosols were generated in a controlled atmosphere wind tunnel by combustion of hexachloroethane mixtures prepared to simulate normal pot burn rates and conditions. The aerosol was characterized and used to expose plant, soil, and other test systems. Particle sizes of airborne HC ranged from 1.3 to 2.1 {mu}m mass median aerodynamic diameter (MMAD), and particle size was affected by relative humidity over a range of 20% to 85%. Air concentrations employed ranged from 130 to 680 mg/m{sup 3}, depending on exposure scenario. Chlorocarbon concentrations within smokes, deposition rates for plant and soil surfaces, and persistence were determined. The fate of principal inorganic species (Zn, Al, and Cl) in a range of soils was assessed.

  9. Analyzing indirect effects in cluster randomized trials. The effect of estimation method, number of groups and group sizes on accuracy and power

    NARCIS (Netherlands)

    Hox, Joop J.; Moerbeek, Mirjam; Kluytmans, Anouck; van de Schoot, Rens

    2014-01-01

    Cluster randomized trials assess the effect of an intervention that is carried out at the group or cluster level. Ajzen's theory of planned behavior is often used to model the effect of the intervention as an indirect effect mediated in turn by attitude, norms and behavioral intention. Structural eq

  10. The potential for indirect effects between co-flowering plants via shared pollinators depends on resource abundance, accessibility and relatedness.

    Science.gov (United States)

    Carvalheiro, Luísa Gigante; Biesmeijer, Jacobus Christiaan; Benadi, Gita; Fründ, Jochen; Stang, Martina; Bartomeus, Ignasi; Kaiser-Bunbury, Christopher N; Baude, Mathilde; Gomes, Sofia I F; Merckx, Vincent; Baldock, Katherine C R; Bennett, Andrew T D; Boada, Ruth; Bommarco, Riccardo; Cartar, Ralph; Chacoff, Natacha; Dänhardt, Juliana; Dicks, Lynn V; Dormann, Carsten F; Ekroos, Johan; Henson, Kate S E; Holzschuh, Andrea; Junker, Robert R; Lopezaraiza-Mikel, Martha; Memmott, Jane; Montero-Castaño, Ana; Nelson, Isabel L; Petanidou, Theodora; Power, Eileen F; Rundlöf, Maj; Smith, Henrik G; Stout, Jane C; Temitope, Kehinde; Tscharntke, Teja; Tscheulin, Thomas; Vilà, Montserrat; Kunin, William E

    2014-11-01

    Co-flowering plant species commonly share flower visitors, and thus have the potential to influence each other's pollination. In this study we analysed 750 quantitative plant-pollinator networks from 28 studies representing diverse biomes worldwide. We show that the potential for one plant species to influence another indirectly via shared pollinators was greater for plants whose resources were more abundant (higher floral unit number and nectar sugar content) and more accessible. The potential indirect influence was also stronger between phylogenetically closer plant species and was independent of plant geographic origin (native vs. non-native). The positive effect of nectar sugar content and phylogenetic proximity was much more accentuated for bees than for other groups. Consequently, the impact of these factors depends on the pollination mode of plants, e.g. bee or fly pollinated. Our findings may help predict which plant species have the greatest importance in the functioning of plant-pollination networks. PMID:25167890

  11. Effects of two transition metal sulfate salts on secondary organic aerosol formation in toluene/NOx photooxidation

    Institute of Scientific and Technical Information of China (English)

    Biwu CHU; Jiming HAO; Junhua LI; Hideto TAKEKAWA; Kun WANG; Jingkun JIANG

    2013-01-01

    Aerosol phase reactions play a very important role on secondary organic aerosol (SOA) formation, and metal-containing aerosols are important components in the atmosphere. In this study, we tested the effects of two transition metal sulfate salts, manganese sulfate (MnSO4) and zinc sulfate (ZnSO4), on the photochemical reactions of a toluene/NOx photooxidation system in a 2 m3 smog chamber. By comparing photochemical reaction products of experiments with and without transition metal sulfate seed aerosols, we evaluated the effects of transition metal sulfate seed aerosols on toluene consumption, NOx conversion and the formation of ozone and SOA. MnSO4 and ZnSO4 seed aerosols were found to have similar effects on photochemical reactions, both enhance the SOA production, while showing negligible effects on the gas phase compounds. These observations are consistent when varying metal sulfate aerosol concentrations. This is attributed to the catalytic effects of MnSO4 and ZnSO4 seed aerosols which may enhance the formation of condensable semivolatile compounds. Their subsequent partitioning into the aerosol phase leads to the observed SOA formation enhancement.

  12. Radiative Forcing of the Direct Aerosol Effect from AeroCom Phase II Simulations

    Science.gov (United States)

    Myhre, G.; Samset, B. H.; Schulz, M.; Balkanski, Y.; Bauer, S.; Berntsen, T. K.; Bian, H.; Bellouin, N.; Chin, M.; Diehl, T.; Easter, R. C.; Feichter, J.; Ghan, S. J.; Hauglustaine, D.; Iversen, T.; Kinne, S.; Kirkevag, A.; Lamarque, J.-F.; Lin, G.; Liu, X.; Lund, M. T.; Luo, G.; Ma, X.; vanNoije, T.; Penner, J. E.; Rasch, P. J.; Ruiz, A.; Seland, O.; Skeie, R. B.; Stier, P.; Takemura, T.; Tsigaridis, K.; Wang, P.; Wang, Z.; Xu, L.; Yu, H.; Yu, F.; Yoon, J. -H.; Zhang, K.; Zhang, H.; Zhou, C.

    2013-01-01

    We report on the AeroCom Phase II direct aerosol effect (DAE) experiment where 16 detailed global aerosol models have been used to simulate the changes in the aerosol distribution over the industrial era. All 16 models have estimated the radiative forcing (RF) of the anthropogenic DAE, and have taken into account anthropogenic sulphate, black carbon (BC) and organic aerosols (OA) from fossil fuel, biofuel, and biomass burning emissions. In addition several models have simulated the DAE of anthropogenic nitrate and anthropogenic influenced secondary organic aerosols (SOA). The model simulated all-sky RF of the DAE from total anthropogenic aerosols has a range from -0.58 to -0.02 W m(sup-2), with a mean of -0.27 W m(sup-2 for the 16 models. Several models did not include nitrate or SOA and modifying the estimate by accounting for this with information slightly strengthens the mean. Modifying the model estimates for missing aerosol components and for the time period 1750 to 2010 results in a mean RF for the DAE of -0.35 W m(sup-2). Compared to AeroCom Phase I (Schulz et al., 2006) we find very similar spreads in both total DAE and aerosol component RF. However, the RF of the total DAE is stronger negative and RF from BC from fossil fuel and biofuel emissions are stronger positive in the present study than in the previous AeroCom study.We find a tendency for models having a strong (positive) BC RF to also have strong (negative) sulphate or OA RF. This relationship leads to smaller uncertainty in the total RF of the DAE compared to the RF of the sum of the individual aerosol components. The spread in results for the individual aerosol components is substantial, and can be divided into diversities in burden, mass extinction coefficient (MEC), and normalized RF with respect to AOD. We find that these three factors give similar contributions to the spread in results

  13. Observations of relative humidity effects on aerosol light scattering in the Yangtze River Delta of China

    Science.gov (United States)

    Zhang, L.; Sun, J. Y.; Shen, X. J.; Zhang, Y. M.; Che, H. C.; Ma, Q. L.; Zhang, Y. W.; Zhang, X. Y.; Ogren, J. A.

    2015-01-01

    Scattering of solar radiation by aerosol particles is highly dependent on relative humidity (RH) as hygroscopic particles take up water with increasing RH. To achieve a better understanding of the effect of aerosol hygroscopic growth on light scattering properties and radiative forcing, a field campaign was carried out in the Yangtze River Delta of China in March 2013. During the observation period, the mean and standard deviation of enhancement factors at RH=85% for the scattering coefficient (f(85%)), backscattering coefficient (fb(85%)) and hemispheric backscatter fraction (fβ(85%)) were 1.58 ± 0.12, 1.25 ± 0.07 and 0.79 ± 0.04, respectively, i.e. aerosol scattering coefficient and backscattering coefficient increased by 58 and 25% as the RH increased from 40 to 85%. Meanwhile, the aerosol hemispheric backscatter fraction decreased by 21%. The relative amount of organic matter (OM) and inorganics in PM1 was found to be a main factor determining the magnitude of f(RH), the highest values of f(RH) corresponded to the aerosols with a small fraction of organic matter (OM), and vice versa. The relative amount of NO3- in fine particles was strongly correlated to f(85%), which suggests NO3- played a vital role in aerosol hygroscopic growth during this study. The mass percentage of nitrate also had a close relation to the curvature of humidograms, namely, the higher the nitrate concentration is, the straighter the humidogram will be. Air masses that arrived at LinAn in March can be classified into northerly-polluted, locally-polluted and dust-influenced types, the scattering enhancement factors at 85% RH were 1.52 ± 0.10, 1.64 ± 0.09 and 1.48 ± 0.05, respectively. The sensitivity of the aerosol radiative forcing to f(RH) at the measured mean ambient RH 67% for various aerosol types was also estimated. The direct radiative forcing increased by 11.8, 19.5, and 10.5%, respectively, for locally-polluted, northerly-polluted and dust-influenced aerosols due to aerosol

  14. Digital terrain model evaluation and computation of the terrain correction and indirect effect in South America

    Directory of Open Access Journals (Sweden)

    Denizar Blitzkow

    2009-12-01

    Full Text Available The main objectives of this paper are to compare digital terrain models, to show the generated models for South America and to present two applications. Shuttle Radar Topography Mission (SRTM produced the most important and updated height information in the world. This paper addresses the attention to comparisons of the following models: SRTM3, DTM2002, GLOBE, GTOPO30, ETOPO2 and ETOPO5, at the common points of the grid. The comparisons are limited by latitudes 60º S and 25 º N and longitudes 100 º W and 25 º W. All these data, after some analysis, have been used to create three models for South America: SAM_1mv1, SAM_1mv2 (both of 1' grid spacing and SAM_30s (30" grid spacing. Besides this effort, the three models as well as STRM were evaluated using Bench Marks (BM in Brazil and Argentina. This paper also shows two important geodesy and geophysics applications using the SAM_1mv1: terrain correction (one of the reductions applied to the gravity acceleration and indirect effect (a consequence of the reduction of the external mass to the geoid. These are important at Andes for a precise geoid computation.Los objetivos principales de este documento son comparar modelos digitales del continente; enseñar los modelos generados para Sudamérica y presentar dos aplicaciones. Shuttle Radar Topography Mission (SRTM produjo la información más importante y más actualizada de las altitudes del mundo. Este trabajo centra su atención en las comparaciones de los modelos siguientes: SRTM3, DTM2002, GLOBO, GTOPO30, ETOPO2 y ETOPO5, en los puntos comunes de la rejilla. Las comparaciones son limitadas por las latitudes 60º S y 25 º N y longitudes 100 º W y 25 º W. Todos estos datos, después de los análisis, se han utilizado para crear tres modelos para Sudamérica: SAM_1mv1, SAM_1mv2 (1' de espaciamiento de la rejilla y SAM_30s (30" de espaciamiento de la rejilla. Los tres modelos bien como el STRM fueron evaluados usando puntos de referencia de

  15. Effects of DTPA aerosol on lung contamination by lanthanum; Influence du DTPA en aerosol sur les contaminations pulmonaires au lanthane

    Energy Technology Data Exchange (ETDEWEB)

    Pasquier, C.; Voisin, D.; Thieblement, P.; Perrault, G.; Bayard, J. [Commissariat a l' Energie Atomique, Fontenay-aux-Roses (France). Centre d' Etudes Nucleaires

    1969-07-01

    Applying DTPA aerosol for the treatment of lung contamination by lanthanum we were able to determine its effectiveness as a function of time. Provided it was administered early during the two hours after exposure, over 50 per cent could be removed using lower therapeutic doses than those prescribed for other routes of administration. Its association with some enzymes did not enhance the chelator therapeutic effect. We also calculated the constant of passage of lanthanum through the alveolar wall and found a value of 0.016 mn{sup -1}. Finally, as we have discovered a large part cannot be mobilized by DTPA, we shall now study the physico-chemical mechanisms involved in this protection. (authors) [French] L'emploi du DTPA en aerosol dans le traitement des contaminations pulmonaires par le lanthane, nous a permis d'etablir et d'evaluer son efficacite en fonction du temps. A condition d'etre utilise precocement, dans les deux heures qui suivent la contamination, une fraction superieure a 50 pour cent peut etre eliminee et ceci avec des doses therapeutiques inferieures a celles preconisees pour les autres voies d'administration. L'association avec quelques autres enzymes n'a pas permis d'ameliorer l'effet therapeutique de ce chelateur. Nous avons egalement chiffre la constante de passage du lanthane a travers la barriere alveolaire dont la valeur est de l'ordre de 0.016 mn{sup -1} Enfin, la decouverte d'une importante partie non piegeable par le DTPA nous amene maintenant a etudier les mecanismes physico-chimiques de cette protection. (auteurs)

  16. The effect of varying levels of surfactant on the reactive uptake of N2O5 to aqueous aerosol

    OpenAIRE

    V. F. McNeill; Patterson, J; Wolfe, G. M.; Thornton, J. A.

    2006-01-01

    Recent observations have detected surface active organics in atmospheric aerosols. We have studied the reaction of N2O5 on aqueous natural seawater and NaCl aerosols as a function of sodium dodecyl sulfate (SDS) concentration to test the effect of varying levels of surfactant on gas-aerosol reaction rates. SDS was chosen as a proxy for naturally occurring long chain monocarboxylic acid molecules, such as palmitic or stearic acid, because of its solubility in water and well-c...

  17. An effective model for fermion dark matter. Indirect detection of supersymmetric dark matter in astronomy with the CELESTE Telescope; Modele effectif de matiere noire fermionique. Detection indirecte de matiere noir supersymetrique en astronomie avec le Telescope CELESTE

    Energy Technology Data Exchange (ETDEWEB)

    Lavalle, Julien [Ecole Doctorale des Sciences Fondamentales, Universite Blaise Pascal, Aubiere (France)

    2004-07-01

    The purpose of this thesis is to discuss both phenomenological and experimental aspects of Dark Matter, related to its indirect detection with gamma-ray astronomy. In the MSSM framework, neutralinos arise as natural candidates to non-baryonic and Cold Dark Matter, whose gravitational effects manifest in the Universe at different scales. As they are Majorana particles, they may in principle annihilate in high density regions, as the centres of galaxies, and produce gamma rays. Nevertheless, the expected fluxes are basically low compared to experimental sensitivities. After estimating gamma fluxes from M31 and Draco galaxies in the MSSM scheme, we first generalize the MSSM couplings by studying an effective Lagrangian. We show that the only constraint of imposing a relic abundance compatible with recent measurements obviously deplete significantly the gamma ray production, but also that predictions in this effective approach are more optimistic for indirect detection than the MSSM. In a second part, we present the indirect searches for Dark Matter performed with the CELESTE Cherenkov telescope towards the galaxy M31. We propose a statistical method to reconstruct spectra, mandatory to discriminate classical and exotic spectra. The M31 data analysis enables the extraction of an upper limit on the gamma ray flux, which is the first worldwide for a galaxy in the energy range 50-500 GeV, and whose astrophysical interest goes beyond indirect searches for Dark Matter. (author)

  18. Dust aerosol impact on North Africa climate: a GCM investigation of aerosol-cloud-radiation interactions using A-Train satellite data

    Directory of Open Access Journals (Sweden)

    Y. Gu

    2011-12-01

    Full Text Available The climatic effects of dust aerosols in North Africa have been investigated using the atmospheric general circulation model (AGCM developed at the University of California, Los Angeles (UCLA. The model includes an efficient and physically based radiation parameterization scheme developed specifically for application to clouds and aerosols. Parameterization of the effective ice particle size in association with the aerosol first indirect effect based on ice cloud and aerosol data retrieved from A-Train satellite observations have been employed in climate model simulations. Offline simulations reveal that the direct solar, IR, and net forcings by dust aerosols at the top of the atmosphere (TOA generally increase with increasing aerosol optical depth (AOD. When the dust semi-direct effect is included with the presence of ice clouds, positive IR radiative forcing is enhanced since ice clouds trap substantial IR radiation, while the positive solar forcing with dust aerosols alone has been changed to negative values due to the strong reflection of solar radiation by clouds, indicating that cloud forcing associated with aerosol semi-direct effect could exceed direct aerosol forcing. With the aerosol first indirect effect, the net cloud forcing is generally reduced for an ice water path (IWP larger than 20 g m−2. The magnitude of the reduction increases with IWP.

    AGCM simulations show that the reduced ice crystal mean effective size due to the aerosol first indirect effect results in less OLR and net solar flux at the top of the atmosphere over the cloudy area of the North Africa region because ice clouds with smaller size trap more IR radiation and reflect more solar radiation. The precipitation in the same area, however, increases due to the aerosol indirect effect on ice clouds, corresponding to the enhanced convection as indicated by reduced OLR. The increased precipitation appears to be associated with enhanced ice water

  19. Determining the effect of turbulent shear on containment aerosol dynamics using microgravity experiments

    International Nuclear Information System (INIS)

    Determining the characteristics of large aerosol aggregates 'clusters' under turbulent conditions is fundamental for predicting the behaviour of radioactive aerosols inside the reactor containment following a severe accident. Studying such rapidly settling clusters is extremely difficult in ground-based experiments due to the effect of the earth's gravity. In this study, the microgravity environment is exploited to investigate the effect of turbulent shear on the aggregation and breakage of clusters by examining their structure and measuring their strength parameters while suspended under weightlessness conditions. A parametric model is introduced to correlate the experimental results over into nuclear aerosol models. It was demonstrated that the cluster parameters depend mainly on the turbulent field intensity as well as initial powder conditions. (author)

  20. Effects of Microbial Aerosol in Poultry House on Meat Ducks' Immune Function.

    Science.gov (United States)

    Yu, Guanliu; Wang, Yao; Wang, Shouguo; Duan, Changmin; Wei, Liangmeng; Gao, Jing; Chai, Tongjie; Cai, Yumei

    2016-01-01

    The aim of this study was to evaluate effects of microbial aerosols on immune function of ducks and shed light on the establishment of microbial aerosol concentration standards for poultry. A total of 1800 1-d-old cherry valley ducks were randomly divided into five groups (A, B, C, D, and E) with 360 ducks in each. To obtain objective data, each group had three replications. Concentrations of airborne bacteria, fungi, endotoxin in different groups were created by controlling ventilation and bedding cleaning frequency. Group A was the control group and hygienic conditions deteriorated progressively from group B to E. A 6-stage Andersen impactor was used to detect the aerosol concentration of aerobes, gram-negative bacteria, fungi, and AGI-30 microbial air sampler detect the endotoxin, and Composite Gas Detector detect the noxious gas. In order to assess the immune function of meat ducks, immune indicators including H5 AIV antibody titer, IgG, IL-2, T-lymphocyte transformation rate, lysozyme and immune organ indexes were evaluated. Correlation coefficients were also calculated to evaluate the relationships among airborne bacteria, fungi, endotoxin, and immune indicators. The results showed that the concentration of airborne aerobe, gram-negative bacteria, fungi, endotoxin have a strong correlation to H5 AIV antibody titer, IgG, IL-2, T-lymphocyte transformation rate, lysozyme, and immune organ indexes, respectively. In addition, when the concentration of microbial aerosol reach the level of group D, serum IgG (6-8 weeks), lysozyme (4 week) were significantly higher than in group A (P aerosol adversely affected the immune level of meat ducks. The microbial aerosol values in group D provide a basis for recommending upper limit concentrations of microbial aerosols for healthy meat ducks. PMID:27582731

  1. Why Is the Climate Forcing of Sulfate Aerosols So Uncertain?

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Sulfate aerosol particles have strong scattering effect on the solar radiation transfer which results in increasing the planet albedo and, hence, tend to cool the earth-atmosphere system. Also, aerosols can act as the cloud condensation nuclei (CCN) which tend to increase the albedo of clouds and cool the global warming. The ARPEGE-Climat version 3 AGCM with FMR radiation scheme is used to estimate the direct and indirect radiative forcing of sulfate aerosols. For minimizing the uncertainties in assessing this kind of cooling effect, all kinds of factors are analyzed which have been mixed in the assessment process and may lead to the different results of the radiative forcing of aerosols. It is noticed that one of the uncertainties to assess the climate forcing of aerosols by GCM results from the different definition of radiative forcing that was used. In order to clarify this vague idea, the off-line case for considering no feedbacks and on-line case for including all the feedbacks have been used for assessment. The direct forcing of sulfate aerosols in off-line case is -0.57 W/m2 and -0.38 W/m2 for the clear sky and all sky respectively. The value of on-line case appears to be a little larger than that in off-line case chiefly due to the feedback of clouds. The indirect forcing of sulfate aerosols in off-line case is -1.4 W / m2 and -1.0 W / m2 in on-line case. The radiative forcing of sulfate aerosols has obvious regional characteristics. There is a larger negative radiative forcing over North America, Europe and East Asia. If the direct and indirect forcing are added together, it is enough to offset the positive radiative forcing induced by the greenhouse gases in these regions.

  2. Effectiveness of indirect evaporative cooling and thermal mass in a hot arid climate

    Energy Technology Data Exchange (ETDEWEB)

    Krueger, Eduardo [Programa de Pos-Graduacao em Tecnologia/Programa de Pos-Graduacao em Engenharia Civil, Departamento de Construcao Civil, Universidade Tecnologica Federal do Parana - UTFPR, Av. Sete de Setembro, 3165. Curitiba PR, CEP. 80230-901 (Brazil); Gonzalez Cruz, Eduardo [Instituto de Investigaciones de la Facultad de Arquitectura y Diseno (IFAD), Universidad del Zulia, Nucleo Tecnico de LUZ, Av. Goajira (16) con Calle 67, Maracaibo, CP 4011-A-526 (Venezuela); Givoni, Baruch [Department of Architecture, School of Arts and Architecture, UCLA, Los Angeles CA, USA, and Ben Gurion University (Israel)

    2010-06-15

    In this paper, we compare results of a long-term temperature monitoring in a building with high thermal mass to indoor temperature predictions of a second building that uses an indirect evaporative cooling system as a means of passive cooling (Vivienda Bioclimatica Prototipo -VBP-1), for the climatic conditions of Sde Boqer, Negev region of Israel (local latitude 30 52'N, longitude 34 46'E, ap