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Sample records for aerosol forcing efficiency

  1. Spatially Refined Aerosol Direct Radiative Forcing Efficiencies

    EPA Science Inventory

    Global aerosol direct radiative forcing (DRF) is an important metric for assessing potential climate impacts of future emissions changes. However, the radiative consequences of emissions perturbations are not readily quantified nor well understood at the level of detail necessary...

  2. Spatially Refined Aerosol Direct Radiative Forcing Efficiencies

    NASA Technical Reports Server (NTRS)

    Henze, Daven K.; Shindell, Drew Todd; Akhtar, Farhan; Spurr, Robert J. D.; Pinder, Robert W.; Loughlin, Dan; Kopacz, Monika; Singh, Kumaresh; Shim, Changsub

    2012-01-01

    Global aerosol direct radiative forcing (DRF) is an important metric for assessing potential climate impacts of future emissions changes. However, the radiative consequences of emissions perturbations are not readily quantified nor well understood at the level of detail necessary to assess realistic policy options. To address this challenge, here we show how adjoint model sensitivities can be used to provide highly spatially resolved estimates of the DRF from emissions of black carbon (BC), primary organic carbon (OC), sulfur dioxide (SO2), and ammonia (NH3), using the example of emissions from each sector and country following multiple Representative Concentration Pathway (RCPs). The radiative forcing efficiencies of many individual emissions are found to differ considerably from regional or sectoral averages for NH3, SO2 from the power sector, and BC from domestic, industrial, transportation and biomass burning sources. Consequently, the amount of emissions controls required to attain a specific DRF varies at intracontinental scales by up to a factor of 4. These results thus demonstrate both a need and means for incorporating spatially refined aerosol DRF into analysis of future emissions scenario and design of air quality and climate change mitigation policies.

  3. Aerosol Direct Radiative Forcing and Forcing Efficiencies at Surface from the shortwave Irradiance Measurements in Abu Dhabi, UAE

    NASA Astrophysics Data System (ADS)

    Beegum S, N.; Ben Romdhane, H.; Ghedira, H.

    2013-12-01

    Atmospheric aerosols are known to affect the radiation balance of the Earth-Atmospheric system directly by scattering and absorbing the solar and terrestrial radiation, and indirectly by affecting the lifetime and albedo of the clouds. Continuous and simultaneous measurements of short wave global irradiance in combination with synchronous spectral aerosol optical depth (AOD) measurements (from 340 nm to 1640 nm in 8 channels), for a period of 1 year from June 2012 to May 2013, were used for the determination of the surface direct aerosol radiative forcing and forcing efficiencies under cloud free conditions in Abu Dhabi (24.42°N, 54.61o E, 7m MSL), a coastal location in United Arab Emirates (UAE) in the Arabian Peninsula. The Rotating Shadow band Pyranometer (RSP, LI-COR) was used for the irradiance measurements (in the spectral region 400-1100 nm), whereas the AOD measurements were carried out using CIMEL Sunphotometer (CE 318-2, under AERONET program). The differential method, which is neither sensitive to calibration uncertainties nor model assumptions, has been employed for estimating forcing efficiencies from the changes in the measured fluxes. The forcing efficiency, which quantifies the net change in irradiance per unit change in AOD, is an appropriate parameter for the characterization of the aerosol radiative effects even if the microphysical and optical properties of the aerosols are not completely understood. The corresponding forcing values were estimated from the forcing efficiencies. The estimated radiative forcing and forcing efficiencies exhibited strong monthly variations. The forcing efficiencies (absolute magnitudes) were highest during March, and showed continuous decrease thereafter to reach the lowest value during September. In contrast, the forcing followed a slightly different pattern of variability, with the highest solar dimming during April ( -60 W m-2) and the minimum during February ( -20 W m-2). The results indicate that the aerosol

  4. Shortwave radiative forcing and efficiency of key aerosol types using AERONET data

    NASA Astrophysics Data System (ADS)

    García, O. E.; Díaz, J. P.; Expósito, F. J.; Díaz, A. M.; Dubovik, O.; Derimian, Y.; Dubuisson, P.; Roger, J.-C.

    2011-12-01

    The shortwave radiative forcing (ΔF) and the radiative forcing efficiency (ΔFeff) of natural and anthropogenic aerosols have been analyzed using estimates of radiation both at the top (TOA) and at the bottom of atmosphere (BOA) modeled based on AERONET aerosol retrievals. In this study we have considered six main types of atmospheric aerosols: desert mineral dust, biomass burning, urban-industrial, continental background, oceanic and free troposphere. The ΔF averages obtained vary from -148 ± 44 Wm-2 (aerosol optical depth, AOD, at 0.55 μm, 0.85 ± 0.45) at the BOA for the mixture of desert mineral dust and biomass burning aerosols in Central Africa and -42 ± 22 Wm-2 (AOD = 0.86 ± 0.51) at the TOA for the pure mineral dust also in this region up to -6 ± 3 Wm-2 and -4 ± 2 Wm-2 (AOD = 0.03 ± 0.02) at the BOA and the TOA, respectively, for free troposphere conditions. This last result may be taken as reference on a global scale. Furthermore, we observe that the more absorbing aerosols are overall more efficient at the BOA in contrast to at the TOA, where they backscatter less solar energy into the space. The analysis of the radiative balance at the TOA shows that, together with the amount of aerosols and their absorptive capacity, it is essential to consider the surface albedo of the region on which they are. Thus, we document that in regions with high surface reflectivity (deserts and snow conditions) atmospheric aerosols lead to a warming of the Earth-atmosphere system, contributing to the greenhouse gas effect.

  5. Shortwave radiative forcing and efficiency of key aerosol types using AERONET data

    NASA Astrophysics Data System (ADS)

    García, O. E.; Díaz, J. P.; Expósito, F. J.; Díaz, A. M.; Dubovik, O.; Derimian, Y.; Dubuisson, P.; Roger, J.-C.

    2012-06-01

    The shortwave radiative forcing (ΔF) and the radiative forcing efficiency (ΔFeff) of natural and anthropogenic aerosols have been analyzed using estimates of radiation both at the Top (TOA) and at the Bottom Of Atmosphere (BOA) modeled based on AERONET aerosol retrievals. Six main types of atmospheric aerosols have been compared (desert mineral dust, biomass burning, urban-industrial, continental background, oceanic and free troposphere) in similar observational conditions (i.e., for solar zenith angles between 55° and 65°) in order to compare the nearly same solar geometry. The instantaneous ΔF averages obtained vary from -122 ± 37 Wm-2 (aerosol optical depth, AOD, at 0.55 μm, 0.85 ± 0.45) at the BOA for the mixture of desert mineral dust and biomass burning aerosols in West Africa and -42 ± 22 Wm-2 (AOD = 0.9 ± 0.5) at the TOA for the pure mineral dust also in this region up to -6 ± 3 Wm-2 and -4 ± 2 Wm-2 (AOD = 0.03 ± 0.02) at the BOA and the TOA, respectively, for free troposphere conditions. This last result may be taken as reference on a global scale. Furthermore, we observe that the more absorbing aerosols are overall more efficient at the BOA in contrast to at the TOA, where they backscatter less solar energy into the space. The analysis of the radiative balance at the TOA shows that, together with the amount of aerosols and their absorptive capacity, it is essential to consider the surface albedo of the region on which they are. Thus, we document that in regions with high surface reflectivity (deserts and snow conditions) atmospheric aerosols lead to a warming of the Earth-atmosphere system.

  6. Aerosol radiative forcing efficiency in the UV-B region over central Argentina

    NASA Astrophysics Data System (ADS)

    Palancar, Gustavo G.; Olcese, Luis E.; Lanzaco, Bethania L.; Achad, Mariana; López, María Laura; Toselli, Beatriz M.

    2016-07-01

    AEROSOL Robotic Network (AERONET), Moderate Resolution Imaging Spectroradiometer (MODIS) and global UV-B (280-315 nm) irradiance measurements and calculations were combined to investigate the effects of aerosol loading on the ultraviolet B radiation (UV-B) reaching the surface under cloudless conditions in Córdoba, Argentina. The aerosol radiative forcing (ARF) and the aerosol forcing efficiency (ARFE) were calculated for an extended period of time (2000-2013) at a ground-based monitoring site affected by different types and loading of aerosols. The ARFE was evaluated by using the aerosol optical depth (AOD) at 340 nm retrieved by AERONET at the Cordoba CETT site. The individual and combined effects of the single scattering albedo (SSA) and the solar zenith angle (SZA) on the ARFE were also analyzed. In addition, and for comparison purposes, the MODIS AOD at 550 nm was used as input in a machine learning method to better characterize the aerosol load at 340 nm and evaluate the ARFE retrieved from AOD satellite measurements. The ARFE at the surface calculated using AOD data from AERONET ranged from (-0.11 ± 0.01) to (-1.76 ± 0.20) Wm-2 with an average of -0.61 Wm-2; however, when using AOD data from MODIS (TERRA/AQUA satellites), it ranged from (-0.22 ± 0.03) to (-0.65 ± 0.07) Wm-2 with an average value of -0.43 Wm-2. At the same SZA and SSA, the maximum difference between ground and satellite-based was 0.22 Wm-2.

  7. Direct Aerosol Forcing Uncertainty

    DOE Data Explorer

    Mccomiskey, Allison

    2008-01-15

    Understanding sources of uncertainty in aerosol direct radiative forcing (DRF), the difference in a given radiative flux component with and without aerosol, is essential to quantifying changes in Earth's radiation budget. We examine the uncertainty in DRF due to measurement uncertainty in the quantities on which it depends: aerosol optical depth, single scattering albedo, asymmetry parameter, solar geometry, and surface albedo. Direct radiative forcing at the top of the atmosphere and at the surface as well as sensitivities, the changes in DRF in response to unit changes in individual aerosol or surface properties, are calculated at three locations representing distinct aerosol types and radiative environments. The uncertainty in DRF associated with a given property is computed as the product of the sensitivity and typical measurement uncertainty in the respective aerosol or surface property. Sensitivity and uncertainty values permit estimation of total uncertainty in calculated DRF and identification of properties that most limit accuracy in estimating forcing. Total uncertainties in modeled local diurnally averaged forcing range from 0.2 to 1.3 W m-2 (42 to 20%) depending on location (from tropical to polar sites), solar zenith angle, surface reflectance, aerosol type, and aerosol optical depth. The largest contributor to total uncertainty in DRF is usually single scattering albedo; however decreasing measurement uncertainties for any property would increase accuracy in DRF. Comparison of two radiative transfer models suggests the contribution of modeling error is small compared to the total uncertainty although comparable to uncertainty arising from some individual properties.

  8. Factors Affecting Aerosol Radiative Forcing

    NASA Astrophysics Data System (ADS)

    Wang, Jingxu; Lin, Jintai; Ni, Ruijing

    2016-04-01

    Rapid industrial and economic growth has meant a large amount of aerosols in the atmosphere with strong radiative forcing (RF) upon the climate system. Over parts of the globe, the negative forcing of aerosols has overcompensated for the positive forcing of greenhouse gases. Aerosol RF is determined by emissions and various chemical-transport-radiative processes in the atmosphere, a multi-factor problem whose individual contributors have not been well quantified. In this study, we analyze the major factors affecting RF of secondary inorganic aerosols (SIOAs, including sulfate, nitrate and ammonium), primary organic aerosol (POA), and black carbon (BC). We analyze the RF of aerosols produced by 11 major regions across the globe, including but not limited to East Asia, Southeast Asia, South Asia, North America, and Western Europe. Factors analyzed include population size, per capita gross domestic production (GDP), emission intensity (i.e., emissions per unit GDP), chemical efficiency (i.e., mass per unit emissions) and radiative efficiency (i.e., RF per unit mass). We find that among the 11 regions, East Asia produces the largest emissions and aerosol RF, due to relatively high emission intensity and a tremendous population size. South Asia produce the second largest RF of SIOA and BC and the highest RF of POA, in part due to its highest chemical efficiency among all regions. Although Southeast Asia also has large emissions, its aerosol RF is alleviated by its lowest chemical efficiency. The chemical efficiency and radiative efficiency of BC produced by the Middle East-North Africa are the highest across the regions, whereas its RF is lowered by a small per capita GDP. Both North America and Western Europe have low emission intensity, compensating for the effects on RF of large population sizes and per capita GDP. There has been a momentum to transfer industries to Southeast Asia and South Asia, and such transition is expected to continue in the coming years. The

  9. Climate forcing by anthropogenic aerosols.

    PubMed

    Charlson, R J; Schwartz, S E; Hales, J M; Cess, R D; Coakley, J A; Hansen, J E; Hofmann, D J

    1992-01-24

    Although long considered to be of marginal importance to global climate change, tropospheric aerosol contributes substantially to radiative forcing, and anthropogenic sulfate aerosol in particular has imposed a major perturbation to this forcing. Both the direct scattering of shortwavelength solar radiation and the modification of the shortwave reflective properties of clouds by sulfate aerosol particles increase planetary albedo, thereby exerting a cooling influence on the planet. Current climate forcing due to anthropogenic sulfate is estimated to be -1 to -2 watts per square meter, globally averaged. This perturbation is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign. Thus, the aerosol forcing has likely offset global greenhouse warming to a substantial degree. However, differences in geographical and seasonal distributions of these forcings preclude any simple compensation. Aerosol effects must be taken into account in evaluating anthropogenic influences on past, current, and projected future climate and in formulating policy regarding controls on emission of greenhouse gases and sulfur dioxide. Resolution of such policy issues requires integrated research on the magnitude and geographical distribution of aerosol climate forcing and on the controlling chemical and physical processes.

  10. Climate Forcing by Anthropogenic Aerosols

    NASA Astrophysics Data System (ADS)

    Charlson, R. J.; Schwartz, S. E.; Hales, J. M.; Cess, R. D.; Coakley, J. A., Jr.; Hansen, J. E.; Hofmann, D. J.

    1992-01-01

    Although long considered to be of marginal importance to global climate change, tropospheric aerosol contributes substantially to radiative forcing, and anthropogenic sulfate aerosol in particular has imposed a major perturbation to this forcing. Both the direct scattering of short-wavelength solar radiation and the modification of the shortwave reflective properties of clouds by sulfate aerosol particles increase planetary albedo, thereby exerting a cooling influence on the planet. Current climate forcing due to anthropogenic sulfate is estimated to be -1 to -2 watts per square meter, globally averaged. This perturbation is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign. Thus, the aerosol forcing has likely offset global greenhouse warming to a substantial degree. However, differences in geographical and seasonal distributions of these forcings preclude any simple compensation. Aerosol effects must be taken into account in evaluating anthropogenic influences on past, current, and projected future climate and in formulating policy regarding controls on emission of greenhouse gases and sulfur dioxide. Resolution of such policy issues requires integrated research on the magnitude and geographical distribution of aerosol climate forcing and on the controlling chemical and physical processes.

  11. Climate forcing by anthropogenic aerosols

    NASA Technical Reports Server (NTRS)

    Charlson, R. J.; Schwartz, S. E.; Hales, J. M.; Cess, R. D.; Coakley, J. A., Jr.; Hansen, J. E.; Hofmann, D. J.

    1992-01-01

    Although long considered to be of marginal importance to global climate change, tropospheric aerosol contributes substantially to radiative forcing, and anthropogenic sulfate aerosol, in particular, has imposed a major perturbation to this forcing. Both the direct scattering of short-wavelength solar radiation and the modification of the shortwave reflective properties of clouds by sulfate aerosol particles increase planetary albedo, thereby exerting a cooling influence on the planet. Current climate forcing due to anthropogenic sulfate is estimated to be -1 to -2 watts per square meter, globally averaged. This perturbation is comparable in magnitude to current anthropogenic greenhouse gas forcing but opposite in sign. Thus, the aerosol forcing has likely offset global greenhouse warming to a substantial degree. However, differences in geographical and seasonal distributions of these forcings preclude any simple compensation. Aerosol effects must be taken into account in evaluating anthropogenic influences on past, current, and projected future climate and in formulating policy regarding controls on emission of greenhouse gases and sulfur dioxide. Resolution of such policy issues requires integrated research on the magnitude and geographical distribution of aerosol climate forcing and on the controlling chemical and physical processes.

  12. Global Aerosol Radiative Forcing using Satellite and Surface Measurements

    NASA Astrophysics Data System (ADS)

    Patadia, F.; Christopher, S. A.

    2007-12-01

    Over the industrial period, aerosols have increased due to human activities and their effects on climate are the largest source of uncertainty in the current IPCC estimates of global climate forcing due to human activities. Inhomogeneous distribution of aerosols in space and time poses a challenge in their characterization and requires global measurements to assess their effects and reduce the associated uncertainties. In this paper we use global measurements from both satellite and ground based observations for one year time period to estimate the shortwave aerosol radiative forcing (SWARF) at the top-of-atmosphere (TOA) and discuss the associated uncertainties. For this, aerosol properties (optical depth) derived from AErosol RObotic NETwork (AERONET), a federation of ground-based remote sensing instruments, are used in this paper in conjunction with measurements of the TOA shortwave flux from CERES instrument (onboard Terra satellite). High spectral and spatial resolution observations from Imager (MODIS) will be used to identify clear sky conditions within CERES foot print and GOCART results will also be used for separating aerosol types. Global aerosol forcing and corresponding radiative forcing efficiencies will be presented as a function of major aerosol types [including anthropogenic (sulfate, soot, black carbon) and natural (dust) aerosols], region and season. This study should serve as a useful constraint for both numerical modeling simulations and satellite based estimates of SWARF.

  13. Global Aerosol Radiative Forcing Using Satellite and Surface Measurements

    NASA Astrophysics Data System (ADS)

    Patadia, F.; Christopher, S. A.

    2008-05-01

    Over the industrial period, aerosols have increased due to human activities and their effects on climate are the largest source of uncertainty in the current IPCC estimates of global climate forcing due to human activities. Inhomogeneous distribution of aerosols in space and time poses a challenge in characterizing their properties and requires global measurements to assess their effects and reduce the associated uncertainties. In this paper we use global measurements from both satellite and ground based observations for one year time period to estimate the shortwave aerosol radiative forcing (SWARF) at the top-of-atmosphere (TOA) and discuss the associated uncertainties. For this, aerosol properties (optical depth) derived from AErosol RObotic NETwork (AERONET), a federation of ground-based remote sensing instruments, are used in this paper in conjunction with measurements of the TOA shortwave flux from CERES instrument (onboard Terra satellite). High spectral and spatial resolution observations from Imager (MODIS) is used to identify clear sky conditions within CERES foot print and GOCART results will also be used for separating aerosol types. Global aerosol forcing and corresponding radiative forcing efficiencies will be presented as a function of major aerosol types [including anthropogenic (sulfate, soot, black carbon) and natural (dust) aerosols], region and season. This study should serve as a useful constraint for both numerical modeling simulations and satellite based estimates of SWARF.

  14. Thermal Infrared Radiative Forcing By Atmospheric Aerosol

    NASA Astrophysics Data System (ADS)

    Adhikari, Narayan

    The work mainly focuses on the study of thermal infrared (IR) properties of atmospheric greenhouse gases and aerosols, and the estimation of the aerosol-induced direct longwave (LW) radiative forcing in the spectral region 5-20 mum at the Earth's surface (BOA; bottom of the atmosphere) and the top of the atmosphere (TOA) in cloud-free atmospheric conditions. These objectives were accomplished by conducting case studies on clear sky, smoky, and dusty conditions that took place in the Great Basin of the USA in 2013. Both the solar and thermal IR measurements and a state-of-the-science radiative transfer model, the LBLDIS, a combination of the Line-By-Line Radiative Transfer Model and the Discrete Ordinate Radiative Transfer (DISORT) solver were employed for the study. The LW aerosol forcing is often not included in climate models because the aerosol effect on the LW is often assumed to be negligible. We lack knowledge of aerosol characteristics in the LW region, and aerosol properties exhibit high variability. We have found that the LW TOA radiative forcing due to fine mode aerosols, mainly associated with small biomass burning smoke particles, is + 0.4 W/m2 which seems to be small, but it is similar to the LW radiative forcing due to increase in CO2 concentration in the Earth's atmosphere since the preindustrial era of 1750 (+ 1.6 W/m 2). The LW radiative forcing due to coarse mode aerosols, associated with large airborne mineral dust particles, was found to be as much as + 5.02 W/m2 at the surface and + 1.71 W/m2 at the TOA. All of these significant positive values of the aerosol radiative forcing both at the BOA and TOA indicate that the aerosols have a heating effect in the LW range, which contributes to counterbalancing the cooling effect associated with the aerosol radiative forcing in the shortwave (SW) spectral region. In the meantime, we have found that LW radiative forcing by aerosols is highly sensitive to particle size and complex refractive indices of

  15. Longwave radiative forcing by aqueous aerosols

    SciTech Connect

    Gaffney, J.S.; Marley, N.A.

    1995-01-01

    Recently, a great deal of interest has been focused on the role of aerosols in climatic change because of their potential cooling impacts due to light scattering. Recent advances in infrared spectroscopy using cylindrical internal reflectance have allowed the longwave absorption of dissolved aerosol species and the associated liquid water to be accurately determined and evaluated. Experimental measurements using these techniques have shown that dissolved sulfate, nitrate, and numerous other aerosol species will act to cause greenhouse effects. Preliminary calculations indicate that the longwave climate forcing (i.e., heating) for sulfate aerosol will be comparable in magnitude to the cooling effect produced by light scattering. However, more detailed modeling will clearly be needed to address the impact of the longwave forcing due to aerosols as a function of atmospheric height and composition. Their work has shown that aerosol composition will be important in determining longwave forcing, while shortwave forcing will be more related to the physical size of the aerosol droplets. On the basis of these studies, it is increasingly apparent that aerosols, fogs, and clouds play a key role in determining the radiative balance of the atmosphere and in controlling regional and global climates.

  16. Simulation of Climate Forcing by Aerosols

    SciTech Connect

    Ghan, Steven J.; Bian, Xindi; Chapman, Elaine G.; Easter, Richard C.; Fann, George I.; Kothari, Suraj C.; Zaveri, Rahul A.; Zhang, Yang

    2004-05-03

    The largest source of uncertainty in estimates of the radiative forcing governing climate change is in the radiative forcing due to anthropogenic aerosols. Current estimates of the global mean of the aerosol radiative forcing range from –0.3 to –3.0 watts per square meter (Wm-2 ) which is opposite in sign and possibly comparable in magnitude to the +2 Wm-2 forcing due to increasing greenhouse gases. We have developed a global aerosol and climate modeling system that provides arguably the most detailed treatment of aerosols and their impact on the planetary radiation balance of any model, but our estimates of radiative forcing have been hindered by our lack of access to high performance computing resources. We propose to use the MSCF to conduct a series of simulations with and without emissions of a variety of aerosol particles and aerosol precursors. These extensive simulations will enable us to produce much more refined estimates of the impact of anthropogenic emissions on radiative forcing of climate change. To take full advantage of the parallelism available on the MSCF MPP1, we will apply the Global Array Toolkit to dynamically load balance the reactive chemistry component of our model. We will adapt our modifications of the serial NCAR Community Climate Model CCM2 to the parallel NCAR CCM3.10.

  17. How Important Is Organic Aerosol Hygroscopicity to Aerosol Indirect Forcing?

    SciTech Connect

    Liu, Xiaohong; Wang, Jian

    2010-12-07

    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 and yield 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 (“κ” value) of POA and SOA. Our model simulation indicates that in the present-day condition changing “κ” value of POA from 0 to 0.1 increases the number concentration of cloud condensational nuclei (CCN) at supersaturation S=0.1% by 40-60% over the POA source regions, while changing “κ” value of SOA by ±50% (from 0.14 to 0.07 and 0.21) changes the CCN within 30%. Changes in the in-cloud droplet number concentrations (CDNC) are within 20% in most locations on the globe with the above changes in “κ” value of POA and SOA. Global annual mean anthropogenic aerosol indirect forcing (AIF) between present-day (PD) and pre-industrial (PI) conditions change by 0.4 W m-2 with the control run of -1.3 W m-2. AIF reduces with the increase hygroscopicity of organic aerosol, indicating the important role of natural organic aerosol in buffering the relative change of CDNC from PI to PD.

  18. Radiative forcing under mixed aerosol conditions

    NASA Astrophysics Data System (ADS)

    GarcíA, O. E.; Expósito, F. J.; DíAz, J. P.; DíAz, A. M.

    2011-01-01

    The mixture of mineral dust with biomass burning or urban-industrial aerosols presents significant differences in optical properties when compared to those of the individual constituents, leading to different impacts on solar radiation levels. This effect is assessed by estimating the direct radiative forcing (ΔF) of these aerosols from solar flux models using the radiative parameters derived from the Aerosol Robotic Network (AERONET). These data reveal that, in oceanic and vegetative covers (surface albedo (SA) < 0.30), the aerosol effect at the top of atmosphere (TOA) is always cooling the Earth-atmosphere system, regardless of the aerosol type. The obtained average values of ΔF range between -27 ± 15 Wm-2 (aerosol optical depth (AOD) at 0.55 μm, 0.3 ± 0.3) for mineral dust mixed with urban-industrial aerosols, registered in the East Asia region, and -34 ± 18 Wm-2 (AOD = 0.8 ± 0.4) for the mixture of the mineral dust and biomass burning particles, observed in the Central Africa region. In the intermediate SA range (0.30-0.50) the TOA radiative effect depends on the aerosol absorption properties. Thus, aerosols with single scattering albedo at 0.55 μm lower than ˜0.88 lead to a warming of the system, with ΔF of 10 ± 11 Wm-2 for the mixture of mineral dust and biomass burning. Cases with SA > 0.30 are not present in East Asia region. At the bottom of atmosphere (BOA) the maximum ΔF values are associated with the highest AOD levels obtained for the mixture of mineral dust and biomass burning aerosols (-130 ± 44 Wm-2 with AOD = 0.8 ± 0.4 for SA < 0.30).

  19. Saharan Dust Aerosol Radiative Forcing Measured from Space.

    NASA Astrophysics Data System (ADS)

    Li, F.; Vogelmann, A. M.; Ramanathan, V.

    2004-07-01

    This study uses data collected from the Clouds and the Earth's Radiant Energy System (CERES) and the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments to determine Saharan dust broadband shortwave aerosol radiative forcing over the Atlantic Ocean near the African coast (15° 25°N, 45° 15°W). The clear-sky aerosol forcing is derived directly from these data, without requiring detailed information about the aerosol properties that are not routinely observed such as chemical composition, microphysical properties, and their height variations. To determine the diurnally averaged Saharan dust radiative forcing efficiency (i.e., broadband shortwave forcing per unit optical depth at 550 nm, W m-2 τ-1a), two extreme seasons are juxtaposed: the high-dust months [June August (JJA)] and the low-dust months [November January (NDJ)]. It is found that the top-of-atmosphere (TOA) diurnal mean forcing efficiency is -35 ± 3 W m-2 τ-1a for JJA, and -26 ± 3 W m-2 τ-1a for NDJ. These efficiencies can be fit by reducing the spectrally varying aerosol single-scattering albedo such that its value at 550 nm is reduced from 0.95 ± 0.04 for JJA to about 0.86 ± 0.04 for NDJ. The lower value for the low-dust months might be influenced by biomass-burning aerosols that were transported into the study region from equatorial Africa. Although the high-dust season has a greater (absolute value of the) TOA forcing efficiency, the low-dust season may have a greater surface forcing efficiency. Extrapolations based on model calculations suggest the surface forcing efficiencies to be about -65 W m-2 τ-1a for the high-dust season versus -81 W m-2 τ-1a for the low-dust season. These observations indicate that the aerosol character within a region can be readily modified, even immediately adjacent to a powerful source region such as the Sahara. This study provides important observational constraints for models of dust radiative forcing.


  20. Infrared Aerosol Radiative Forcing at the Surface and the Top of the Atmosphere

    NASA Technical Reports Server (NTRS)

    Markowicz, Krzysztof M.; Flatau, Piotr J.; Vogelmann, Andrew M.; Quinn, Patricia K.; Welton, Ellsworth J.

    2003-01-01

    We study the clear-sky aerosol radiative forcing at infrared wavelengths using data from the Aerosol Characterization Experiment (ACE-Asia) cruise of the NOAA R/V Ronald H. Brown. Limited number of data points is analyzed mostly from ship and collocated satellite values. An optical model is derived from chemical measurements, lidar profiles, and visible extinction measurements which is used to and estimate the infrared aerosol optical thickness and the single scattering albedo. The IR model results are compared to detailed Fourier Transform Interferometer based infrared aerosol forcing estimates, pyrgeometer based infrared downward fluxes, and against the direct solar forcing observations. This combined approach attests for the self-consistency of the optical model and allows to derive quantities such as the infrared forcing at the top of the atmosphere or the infrared optical thickness. The mean infrared aerosol optical thickness at 10 microns is 0.08 and the single scattering albedo is 0.55. The modeled infrared aerosol forcing reaches 10 W/sq m during the cruise, which is a significant contribution to the total direct aerosol forcing. The surface infrared aerosol radiative forcing is between 10 to 25% of the shortwave aerosol forcing. The infrared aerosol forcing at the top of the atmosphere can go up to 19% of the solar aerosol forcing. We show good agreement between satellite (CERES instrument) retrievals and model results at the top of the atmosphere. Over the Sea of Japan, the average infrared radiative forcing is 4.6 W/sq m in the window region at the surface and it is 1.5 W/sq m at top of the atmosphere. The top of the atmosphere IR forcing efficiency is a strong function of aerosol temperature while the surface IR forcing efficiency varies between 37 and 55 W/sq m (per infrared optical depth unit). and changes between 10 to 18 W/sq m (per infrared optical depth unit).

  1. Analyzing Atmospheric Aerosol with Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Kong, W.; Hawkins, L. N.

    2013-12-01

    Aerosol-water interactions are poorly understood for complex organic particles and may be important for determining the radiative forcing of atmospheric aerosol. One factor that may limit water uptake by organic aerosol is the viscosity of the particles. High viscosity particles may have very low diffusion coefficients for water vapor (and VOCs), which may inhibit deliquescence on the timescale of cloud and fog formation. This may be especially true for oligomeric material formed in aqueous reactions. Atomic force microscopy (AFM) is a powerful technique that can measure morphology and material properties at high spatial resolution. We have used AFM to probe the material properties of atmospheric particles as well as simulated brown carbon particles to determine if either type of particle shows high viscosity behavior. AFM works by rastering across a small area (less than 100 microns) of the sample slides and recording the heights of the sample as well as the forces on the tip as it approaches the sample and retracts away. Using this information, we can determine the shape, volume, stiffness, adhesiveness, and viscosity of the particles. Using these methods, we were able to show that, in general, both synthetic brown carbon compounds-formed in aqueous reactions-and submicron size atmospheric aerosol particles are adhesive, stiff, and semi-solid, which indicates that the simulated brown carbon compounds are good proxies of aerosol particles in atmosphere. In addition, based on the force data from AFM, we found that molecules that compose these particles are rather large and that there are a good amount of interactions like attractions between them.

  2. Spatially Refined Aerosol Direct Radiative Focusing Efficiencies

    EPA Science Inventory

    Global aerosol direct radiative forcing (DRF) is an important metric for assessing potential climate impacts of future emissions changes. However, the radiative consequences of emissions perturbations are not readily quantified nor well understood at the level of detail necessary...

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

    SciTech Connect

    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.

  4. Technical Note: Estimating Aerosol Effects on Cloud Radiative Forcing

    SciTech Connect

    Ghan, Steven J.

    2013-10-09

    Estimating anthropogenic aerosol effects on the planetary energy balance through the aerosol influence on clouds using the difference in cloud radiative forcing from simulations with and without anthropogenic emissions produces estimates that are positively biased. A more representative method is suggested using the difference in cloud radiative forcing calculated with aerosol radiative effects neglected. The method also yields an aerosol radiative forcing decomposition that includes a term quantifying the impact of changes in surface albedo. The method requires only two additional diagnostic calculations: the whole-sky and clear-sky top-of-atmosphere radiative flux with aerosol radiative effects neglected.

  5. Longwave Radiative Forcing of Saharan Dust Aerosols Estimated from MODIS, MISR and CERES Observations on Terra

    NASA Technical Reports Server (NTRS)

    Zhang, Jiang-Long; Christopher, Sundar A.

    2003-01-01

    Using observations from the Multi-angle Imaging Spectroradiometer (MISR), the Moderate Resolution Imaging Spectroradiometer (MODIS), and the Clouds and the Earth's Radiant Energy System (CERES) instruments onboard the Terra satellite; we present a new technique for studying longwave (LW) radiative forcing of dust aerosols over the Saharan desert for cloud-free conditions. The monthly-mean LW forcing for September 2000 is 7 W/sq m and the LW forcing efficiency' (LW(sub eff)) is 15 W/sq m. Using radiative transfer calculations, we also show that the vertical distribution of aerosols and water vapor are critical to the understanding of dust aerosol forcing. Using well calibrated, spatially and temporally collocated data sets, we have combined the strengths of three sensors from the same satellite to quantify the LW radiative forcing, and show that dust aerosols have a "warming" effect over the Saharan desert that will counteract the shortwave "cooling effect" of aerosols.

  6. Global climate forcing of aerosols embodied in international trade

    NASA Astrophysics Data System (ADS)

    Lin, Jintai; Tong, Dan; Davis, Steven; Ni, Ruijing; Tan, Xiaoxiao; Pan, Da; Zhao, Hongyan; Lu, Zifeng; Streets, David; Feng, Tong; Zhang, Qiang; Yan, Yingying; Hu, Yongyun; Li, Jing; Liu, Zhu; Jiang, Xujia; Geng, Guannan; He, Kebin; Huang, Yi; Guan, Dabo

    2016-10-01

    International trade separates regions consuming goods and services from regions where goods and related aerosol pollution are produced. Yet the role of trade in aerosol climate forcing attributed to different regions has never been quantified. Here, we contrast the direct radiative forcing of aerosols related to regions' consumption of goods and services against the forcing due to emissions produced in each region. Aerosols assessed include black carbon, primary organic aerosol, and secondary inorganic aerosols, including sulfate, nitrate and ammonium. We find that global aerosol radiative forcing due to emissions produced in East Asia is much stronger than the forcing related to goods and services ultimately consumed in that region because of its large net export of emissions-intensive goods. The opposite is true for net importers such as Western Europe and North America: global radiative forcing related to consumption is much greater than the forcing due to emissions produced in these regions. Overall, trade is associated with a shift of radiative forcing from net importing to net exporting regions. Compared to greenhouse gases such as carbon dioxide, the short atmospheric lifetimes of aerosols cause large localized differences between consumption- and production-related radiative forcing. International efforts to reduce emissions in the exporting countries will help alleviate trade-related climate and health impacts of aerosols while lowering global emissions.

  7. Aerosol Forcing of Climate Change and Anomalous Atmospheric Absorption

    NASA Technical Reports Server (NTRS)

    Hansen, James E.

    2000-01-01

    The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change, Anthropogenic greenhouse gases (GHGs), which are well-measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. We will focus on the role of aerosols as a climate forcing mechanism and the contribution that aerosols might make to the so-called "anomalous" atmospheric absorption that has been inferred from some atmospheric measurements.

  8. Aerosol Forcing of Climate Change and "Anomalous" Atmospheric Absorption

    NASA Technical Reports Server (NTRS)

    Hansen, James E.

    1999-01-01

    The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases (GHGs), which are well-measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. We will focus on the role of aerosols as a climate forcing mechanism and the contribution that aerosols might make to the so- called "anomalous" atmospheric absorption that has been inferred from some atmospheric measurements.

  9. Characterization of Speciated Aerosol Direct Radiative Forcing Over California

    SciTech Connect

    Zhao, Chun; Leung, Lai-Yung R.; Easter, Richard C.; Hand, Jenny; Avise, J.

    2013-03-16

    A fully coupled meteorology-chemistry model (WRF-Chem) with added capability of diagnosing the spatial and seasonal distribution of radiative forcings for individual aerosol species over California is used to characterize the radiative forcing of speciated aerosols in California. Model simulations for the year of 2005 are evaluated with various observations including meteorological data from California Irrigation Management Information System (CIMIS), aerosol mass concentrations from US EPA Chemical Speciation Network (CSN) and Interagency Monitoring of Protected Visual Environments (IMPROVE), and aerosol optical depth from AErosol RObotic NETwork (AERONET) and satellites. The model well captures the observed seasonal meteorological conditions over California. Overall, the simulation is able to reproduce the observed spatial and seasonal distribution of mass concentration of total PM2.5 and the relative contribution from individual aerosol species, except the model significantly underestimates the surface concentrations of organic matter (OM) and elemental carbon (EC), potentially due to uncertainty in the anthropogenic emissions of OM and EC and the outdated secondary organic aerosol mechanism used in the model. A sensitivity simulation with anthropogenic EC emission doubled significantly reduces the model low bias of EC. The simulation reveals high anthropogenic aerosol loading over the Central Valley and the Los Angeles metropolitan regions and high natural aerosol (dust) loading over southeastern California. The seasonality of aerosol surface concentration is mainly determined by vertical turbulent mixing, ventilation, and photochemical activity, with distinct characteristics for individual aerosol species and between urban and rural areas. The simulations show that anthropogenic aerosols dominate the aerosol optical depth (AOD). The ratio of AOD to AAOD (aerosol absorption optical depth) shows distinct seasonality with a winter maximum and a summer minimum

  10. Modeling Radiative Forcing by Aerosols: How Good is Good Enough?

    NASA Astrophysics Data System (ADS)

    Schwartz, S. E.

    2003-12-01

    Radiative forcing of climate change by anthropogenic aerosols is now recognized as the largest uncertainty in climate forcing F over the industrial period. This uncertainty limits inference of Earth's climate sensitivity λ either empirically or by comparison of observed temperature change over the industrial period Δ T with modeled temperature change obtained by imposing a time-dependent forcing in a climate model. Either way, for a desired uncertainty in λ of, say, 30% (e.g., temperature increase resulting from doubling atmospheric CO2 Δ T2x = 3 +/- 1 K), the required uncertainty in F is about 20%. The resultant required uncertainty in aerosol forcing depends on the magnitude of this for cing. If total aerosol forcing is small, the requisite uncertainty can be quite large, e.g., a factor of 2 for aerosol forcing -0.4 W m-2. However as aerosol forcing magnitude increases the requirement is much more stringent, e.g., for aerosol for c ing -1.2 W m-2, 10%, comparable to present uncertainty in greenhouse gas forcing. This talk examines quantifiable uncertainties in aerosol forcing and apportions them between contributions from atmospheric chemistry, atmospheric radiation, and c l ou d microphysics. Unless and until present uncertainties are greatly reduced it will not be possible to place confident limits on Earth's climate sensitivity, limiting society's ability to confidently plan to adapt to or mitigate future climate chang e arising from increasing atmospheric concentrations of greenhouse gases. n

  11. Climate Implications of the Heterogeneity of Anthropogenic Aerosol Forcing

    NASA Astrophysics Data System (ADS)

    Persad, Geeta Gayatri

    Short-lived anthropogenic aerosols are concentrated in regions of high human activity, where they interact with radiation and clouds, causing horizontally heterogeneous radiative forcing between polluted and unpolluted regions. Aerosols can absorb shortwave energy in the atmosphere, but deplete it at the surface, producing opposite radiative perturbations between the surface and atmosphere. This thesis investigates climate and policy implications of this horizontal and vertical heterogeneity of anthropogenic aerosol forcing, employing the Geophysical Fluid Dynamics Laboratory's AM2.1 and AM3 models, both at a global scale and using East Asia as a regional case study. The degree of difference between spatial patterns of climate change due to heterogeneous aerosol forcing versus homogeneous greenhouse gas forcing deeply impacts the detection, attribution, and prediction of regional climate change. This dissertation addresses a gap in current understanding of these two forcings' response pattern development, using AM2.1 historical forcing simulations. The results indicate that fast atmospheric and land-surface processes alone substantially homogenize the global pattern of surface energy flux response to heterogeneous aerosol forcing. Aerosols' vertical redistribution of energy significantly impacts regional climate, but is incompletely understood. It is newly identified here, via observations and historical and idealized forcing simulations, that increased aerosol-driven atmospheric absorption may explain half of East Asia's recent surface insolation decline. Further, aerosols' surface and atmospheric effects counteract each other regionally---atmospheric heating enhances summer monsoon circulation, while surface dimming suppresses it---but absorbing aerosols' combined effects reduce summer monsoon rainfall. This thesis constitutes the first vertical decomposition of aerosols' impacts in this high-emissions region and elucidates the monsoonal response to aerosols

  12. Do Diurnal Aerosol Changes Affect Daily Average Radiative Forcing?

    SciTech Connect

    Kassianov, Evgueni I.; Barnard, James C.; Pekour, Mikhail S.; Berg, Larry K.; Michalsky, Joseph J.; Lantz, K.; Hodges, G. B.

    2013-06-17

    Strong diurnal variability of aerosol has been observed frequently for many urban/industrial regions. How this variability may alter the direct aerosol radiative forcing (DARF), however, is largely unknown. To quantify changes in the time-averaged DARF, we perform an assessment of 29 days of high temporal resolution ground-based data collected during the Two-Column Aerosol Project (TCAP) on Cape Cod, which is downwind of metropolitan areas. We demonstrate that strong diurnal changes of aerosol loading (about 20% on average) have a negligible impact on the 24-h average DARF, when daily averaged optical properties are used to find this quantity. However, when there is a sparse temporal sampling of aerosol properties, which may preclude the calculation of daily averaged optical properties, large errors (up to 100%) in the computed DARF may occur. We describe a simple way of reducing these errors, which suggests the minimal temporal sampling needed to accurately find the forcing.

  13. Satellite Remote Sensing of Aerosol Forcing

    NASA Technical Reports Server (NTRS)

    Remer, Lorraine; Kaufman, Yoram; Ramaprasad, Jaya; Procopio, Aline; Levin, Zev

    1999-01-01

    Aerosol and cloud impacts on the earth's climate become a recent hot topic in climate studies. Having near future earth observing satellites, EOS-AM1 (Earth Observing System-AM1), ENVISAT (Environmental Satellites) and ADEOS-2 (Advanced Earth Observation Satellite-2), it will be a good timing to discuss how to obtain and use the microphysical parameters of aerosols and clouds for studying their climate impacts. Center for Climate System Research (CCSR) of the University of Tokyo invites you to 'Symposium on synergy between satellite-remote sensing and climate modeling in aerosol and cloud issues.' Here, we like to discuss the current and future issues in the remote sensing of aerosol and cloud microphysical parameters and their climate modeling studies. This workshop is also one of workshop series on aerosol remote sensing held in 1996, Washington D. C., and Meribel, France in 1999. It should be reminded that NASDA/ADEOS-1 & -2 (National Space Development Agency of Japan/Advanced Earth Observation Satellite-1 & -2) Workshop will be held in the following week (Dec. 6-10, 1999), so that this opportunity will be a perfect period for you to attend two meetings for satellite remote sensing in Japan. A weekend in Kyoto, the old capital of Japan, will add a nice memory to your visiting Japan. *Issues in the symposium: 1) most recent topics in aerosol and cloud remot sensing, and 2) utility of satellite products on climate modeling of cloud-aerosol effects.

  14. Global simulation of chemistry and radiative forcing of mineral aerosols

    SciTech Connect

    Zhang, Yang; Easter, R.C.; Ghan, S.J.; Leung, L.R.

    1996-12-31

    Mineral aerosols are increasingly gaining attention because of their roles in atmospheric chemistry and climate system. A global three-dimensional aerosol/chemistry model (GChM) coupled with a general circulation model (GCM) is used to simulate the sources/sinks, chemistry and radiative forcing of mineral aerosols. Regional and seasonal variations in distribution of mineral aerosols are predicted based on vegetation types, threshold wind velocities and soil moisture data. The role of mineral aerosols as a reactive surface available for heterogeneous uptake of gas-phase species in the global atmosphere is investigated along with their impact on the tropospheric sulfur cycle and the photochemical oxidant cycle. In particular, the heterogeneous surface reactions of SO{sub 2}, H{sub 2}SO{sub 4}, NO{sub 3}, N{sub 2}O{sub 5}, HNO{sub 3}, O{sub 3}, OH, HO{sub 2}, H{sub 2}O{sub 2} and CH{sub 3}O{sub 2} on mineral aerosols are simulated. The direct radiative forcing by mineral aerosols and the indirect forcing through influencing droplet number concentration are further estimated. The model simulation results are analyzed and compared against the available observational data.

  15. Anthropogenic Aerosol Radiative Forcing in Asia Derived From Regional Models With Atmospheric and Aerosol Data Assimilation

    SciTech Connect

    Chung, Chul Eddy; Ramanathan, V.; Carmichael, Gregory; Kulkarni, S.; Tang, Youhua; Adhikary, Bhupesh; Leung, Lai-Yung R.; Qian, Yun

    2010-07-05

    A high-resolution estimate of monthly 3D aerosol solar heating rates and surface solar fluxes in Asia from 2001 to 2004 is described here. This product stems from an Asian aerosol assimilation project, in which a) the PNNL regional model bounded by the NCEP reanalyses was used to provide meteorology, b) MODIS and AERONET data were integrated for aerosol observations, c) the Iowa aerosol/chemistry model STEM-2K1 used the PNNL meteorology and assimilated aerosol observations, and d) 3D (X-Y-Z) aerosol simulations from the STEM-2K1 were used in the Scripps Monte-Carlo Aerosol Cloud Radiation (MACR) model to produce total and anthropogenic aerosol direct solar forcing for average cloudy skies. The MACR model and STEM both used the PNNL model resolution of 0.45º×0.4º in the horizontal and of 23 layers in the troposphere. The 2001–2004 averaged anthropogenic all-sky aerosol forcing is -1.3 Wm-2 (TOA), +7.3 Wm-2 (atmosphere) and -8.6 Wm-2 (surface) averaged in Asia (60-138°E & Eq. -45°N). In the absence of AERONET SSA assimilation, absorbing aerosol concentration (especially BC aerosol) is much smaller, giving -2.3 Wm-2 (TOA), +4.5 Wm-2 (atmosphere) and -6.8 Wm-2 (surface), averaged in Asia. In the vertical, monthly forcing is mainly concentrated below 600hPa with maxima around 800hPa. Seasonally, low-level forcing is far larger in dry season than in wet season in South Asia, whereas the wet season forcing exceeds the dry season forcing in East Asia. The anthropogenic forcing in the present study is similar to that in Chung et al.’s [2005] in overall magnitude but the former offers fine-scale features and simulated vertical profiles. The interannual variability of the computed anthropogenic forcing is significant and extremely large over major emission outflow areas. In view of this, the present study’s estimate is within the implicated range of the 1999 INDOEX result. However, NCAR/CCSM3

  16. Aerosol types and radiative forcing estimates over East Asia

    NASA Astrophysics Data System (ADS)

    Bhawar, Rohini L.; Lee, Woo-Seop; Rahul, P. R. C.

    2016-09-01

    Using the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) and MODIS (Moderate Resolution Imaging Spectroradiometer) satellite data sets along with the CSIRO-MK 3.6.0 model simulations, we analyzed the aerosol optical depth (AOD) variability during March-May (MAM), June-August (JJA) along with their annual mean variability over East Asia for the period 2006-2012. The CALIPSO measurements correlated well with the MODIS measurements and the CSIRO-MK 3.6.0 model simulations over the spatial distribution patterns of the aerosols, but CALIPSO underestimated the magnitudes of the AOD. Maximum smoke aerosol loading is observed to occur during JJA, as a result of wind transport from Southern China while dust loading dominated during MAM via the transport from desert region. The vertical distribution profiles revealed that there is uniform distribution of smoke aerosols during both MAM and JJA, only differing at the altitude at which they peak; while the dust aerosols during MAM showed a significant distribution from the surface to 10 km altitude and JJA was marked with lower dust loading at the same altitudes. Both dust and smoke aerosols warm the atmosphere in MAM but due to the absorbing nature of smoke aerosols, they cause considerable cooling at the surface which is double when compared to the dust aerosols. The top of the atmosphere aerosol radiative forcing (ARF) due to smoke and dust aerosols is positive in MAM which indicates warming over East Asia. During MAM a consistent declining trend of the surface ARF due to smoke aerosols persisted over the last three decades as conspicuously evidenced from model analysis; the decline is ∼10 W/m2 from 1980 to 2012.

  17. Simulated 2050 aviation radiative forcing from contrails and aerosols

    NASA Astrophysics Data System (ADS)

    Chen, Chih-Chieh; Gettelman, Andrew

    2016-06-01

    The radiative forcing from aviation-induced cloudiness is investigated by using the Community Atmosphere Model Version 5 (CAM5) in the present (2006) and the future (through 2050). Global flight distance is projected to increase by a factor of 4 between 2006 and 2050. However, simulated contrail cirrus radiative forcing in 2050 can reach 87 mW m-2, an increase by a factor of 7 from 2006, and thus does not scale linearly with fuel emission mass. This is due to non-uniform regional increase in air traffic and different sensitivities for contrail radiative forcing in different regions. CAM5 simulations indicate that negative radiative forcing induced by the indirect effect of aviation sulfate aerosols on liquid clouds in 2050 can be as large as -160 mW m-2, an increase by a factor of 4 from 2006. As a result, the net 2050 radiative forcing of contrail cirrus and aviation aerosols may have a cooling effect on the planet. Aviation sulfate aerosols emitted at cruise altitude can be transported down to the lower troposphere, increasing the aerosol concentration, thus increasing the cloud drop number concentration and persistence of low-level clouds. Aviation black carbon aerosols produce a negligible net forcing globally in 2006 and 2050 in this model study. Uncertainties in the methodology and the modeling are significant and discussed in detail. Nevertheless, the projected percentage increase in contrail radiative forcing is important for future aviation impacts. In addition, the role of aviation aerosols in the cloud nucleation processes can greatly influence on the simulated radiative forcing from aircraft-induced cloudiness and even change its sign. Future research to confirm these results is necessary.

  18. Evaluation of Aerosol Indirect Radiative Forcing in MIRAGE

    SciTech Connect

    Ghan, Steven J.; Easter, Richard C.; Hudson, J D.; Breon, Francois

    2001-04-01

    We evaluate aerosol indirect radiative forcing simulated by the Model for Integrated Research on Atmospheric Global Exchanges (MIRAGE). Although explicit measurements of aerosol indirect radiative forcing do not exist, measurements of many of the links between aerosols and indirect radiative forcing are available and can be used for evaluation. These links include the cloud condensation nuclei concentration, the ratio of droplet number to aerosol number, the droplet number concentration, the column droplet number, the column cloud water, the droplet effective radius, the cloud optical depth, the correlation between cloud albedo and droplet effective radius, and the cloud radiative forcing. The CCN concentration simulated by MIRAGE agrees with measurements for supersaturations larger than 0.1%, but not for smaller supersaturations. Simulated droplet number concentrations are too low in most, but not all, locations with available measurements, even when normalized by aerosol number. MIRA GE correctly simulates the higher droplet numbers and smaller droplet sizes over continents and in the Northern Hemisphere. Biases in column cloud water, cloud optical depth, and shortwave cloud radiative forcing are evident in the Intertropical Convergence Zone and in the subtropical oceans. MIRAGE correctly simulates a negative correlation between cloud albedo and droplet size over remote oceans for cloud optical depths greater than 15 and a positive correlation for cloud optical depths less than 15, but fails to simulate a negative correlation over land.

  19. Evaluation of Aerosol Direct Radiative Forcing in MIRAGE

    SciTech Connect

    Ghan, Steven J.; Laulainen, Nels S.; Easter, Richard C.; Wagener, Richard; Nemesure, Seth; Chapman, Elaine G.; Zhang, Yang; Leung, Lai-Yung R.

    2001-04-01

    A variety of measurements have been used to evaluate the treatment of aerosol radiative properties and radiative impacts of aerosols simulated by the Model for Integrated Research on Atmospheric Global Exchanges (MIRAGE). The treatment of water uptake in MIRAGE agrees with laboratory measurements for the aerosol components that have been measured. The simulated frequency of relative humidity near 100% is about twice that of European Center for Medium-range Weather Forecasts analyzed relative humidity. When the analyzed relative humidity is used to calculate aerosol water uptake in MIRAGE, the simulated aerosol optical depth agrees with most surface measurements after cloudy conditions are filtered out and differences between model and station elevations are accounted for. Simulated optical depths are low over sites in Brazil during the biomass burning season and over sites in central Canada during the wildfire season, which can be attributed to limitations in the organic and black car bon emissions data used by MIRAGE. The simulated aerosol optical depths are mostly within a factor of two of satellite estimates, but MIRAGE simulates excessively high aerosol optical depths off the east coast of the US and China, and too little dust off the coast of West Africa and in the Arabian Sea. The simulated distribution of single-scatter albedo is consistent with the available in situ surface measurements. The simulated sensitivity of radiative forcing to aerosol optical depth is consistent with estimates from measurements where available. The simulated spatial distribution of aerosol radiance is broadly consistent with estimates from satellite measurements, but with the same errors as the aerosol optical depth. The simulated direct forcing is within the uncertainty of estimates from measurements in the North Atlantic.

  20. Aerosol characteristics and surface radiative forcing components during a dust outbreak in Gwangju, Republic of Korea.

    PubMed

    Ogunjobi, K O; Kim, Y J

    2008-02-01

    Atmospheric surface aerosol radiative forcing (SARF) DeltaF, forcing efficiency DeltaF(e) and fractional forcing efficiency DeltaFF(e) evaluated from cloud-screened narrowband spectral and thermal-offset-corrected radiometric observations during the Asia dust outbreak episodes in Gwangju, Republic of Korea are reported in this study. Columnar aerosol optical properties (aerosol optical depth (AOD), tau (alambda), Angstrom exponent alpha, mass concentration of fine and coarse mode particles) were also reported for the station between January 2000 and May 2001 consisting of 211cloud-free days. Results indicate that majority of the AOD were within the range 0.25-0.45 while some high aerosol events in which AODs > or = 0.6 were observed during the severe dust episodes. For example, AOD increases from annual average value of 0.34 +/- 0.13 at 501 nm to values >0.60 during the major dust events of March 27-30 and April 7-9, 2000, respectively. The alpha (501-870 nm) which is often used as a qualitative indicator of aerosol particle size had values ranging from 0.01 to 1.77. The diurnal forcing efficiency DeltaDF(e) at Gwangju was estimated to be -81.10 +/- 5.14 W m (-2)/tau (501 nm) and -47.09 +/- 2.20 W m (-2)/tau (501 nm) for the total solar broadband and visible band pass, respectively while the fractional diurnal forcing efficiency DeltaFDF(e) were -15.8 +/- 0.64%/tau (501 nm) and -22.87 +/- 1.13%/tau (501 nm) for the same band passes. Analyses of the 5-day air-mass back trajectories were further developed for Gwangju in order to classify the air-mass and types of aerosol reaching the site during the Asia dust episodes.

  1. The Indian ocean experiment: aerosol forcing obtained from satellite data

    NASA Astrophysics Data System (ADS)

    Rajeev, K.; Ramanathan, V.

    The tropical Indian Ocean provides an ideal and unique natural laboratory to observe and understand the role of anthropogenic aerosols in climate forcing. Since 1996, an international team of American, European and Indian scientists have been collecting aerosol, chemical and radiation data from ships and surface stations, which culminated in a multi-platform field experiment conducted during January to March of 1999. A persistent haze layer that spread over most of the northern Indian Ocean during wintertime was discovered. The layer, a complex mix of organics, black carbon, sulfates, nitrates and other species, subjects the lower atmosphere to a strong radiative heating and a larger reduction in the solar heating of the ocean. We present here the regional distribution of aerosols and the resulting clear sky aerosol radiative forcing at top-of-atmosphere (TOA) observed over the Indian Ocean during the winter months of 1997, 1998 and 1999 based on the aerosol optical depth (AOD) estimated using NOAA14-AVHRR and the TOA radiation budget data from CERES on board TRMM. Using the ratio of surface to TOA clear sky aerosol radiative forcing observed during the same period over the Indian Ocean island of Kaashidhoo (Satheesh and Ramanathan, 2000), the clear sky aerosol radiative forcing at the surface and the atmosphere are discussed. The regional maps of AVHRR derived AOD show abnormally large aerosol concentration during the winter of 1999 which is about 1.5 to 2 times larger than the AOD during the corresponding period of 1997 and 1998. A large latitudinal gradient in AOD is observed during all the three years of observation, with maximum AOD in the northern hemisphere. The diurnal mean clear sky aerosol forcing at TOA in the northern hemisphere Indian Ocean is in the range of -4 to -16 Wm -2 and had large spatio-temporal variations while in the southern hemisphere Indian Ocean it is in the range of 0 to -6Wm -2. The importance of integrating in-situ data with satellite

  2. Large contribution of natural aerosols to uncertainty in indirect forcing.

    PubMed

    Carslaw, K S; Lee, L A; Reddington, C L; Pringle, K J; Rap, A; Forster, P M; Mann, G W; Spracklen, D V; Woodhouse, M T; Regayre, L A; Pierce, J R

    2013-11-01

    The effect of anthropogenic aerosols on cloud droplet concentrations and radiative properties is the source of one of the largest uncertainties in the radiative forcing of climate over the industrial period. This uncertainty affects our ability to estimate how sensitive the climate is to greenhouse gas emissions. Here we perform a sensitivity analysis on a global model to quantify the uncertainty in cloud radiative forcing over the industrial period caused by uncertainties in aerosol emissions and processes. Our results show that 45 per cent of the variance of aerosol forcing since about 1750 arises from uncertainties in natural emissions of volcanic sulphur dioxide, marine dimethylsulphide, biogenic volatile organic carbon, biomass burning and sea spray. Only 34 per cent of the variance is associated with anthropogenic emissions. The results point to the importance of understanding pristine pre-industrial-like environments, with natural aerosols only, and suggest that improved measurements and evaluation of simulated aerosols in polluted present-day conditions will not necessarily result in commensurate reductions in the uncertainty of forcing estimates.

  3. Aerosol Forcing During INDOEX and ACE-Asia as Determined From Aircraft and Grou nd Measurements

    NASA Astrophysics Data System (ADS)

    Marsden, D. C.; Valero, F. P.; Bush, B. C.; Pope, S. K.; Leitner, A. S.

    2002-12-01

    A suite of radiometers was flown on the NCAR C-130 aircraft throughout the INDOEX and ACE-Asia experiments to measure broadband and spectral irradiances. Identical instruments were placed in the zenith and nadir positions, allowing net flux and optical depth to be determined. The radiative forcing efficiency (aerosol forcing per unit optical depth) was determined below the aerosol layer, i.e. at an altitude of about 40 meters. This was measured in the spectral range s 220 to 3910 nm (total solar forcing) and 680 to 3300 nm (near infrared) and in seven spectral channels covering contiguously the visible range from 400 to 700 nm. Surface measurements of solar insolation as well as aerosol column optical depth were made at Kaashidoo, Maldives (INDOEX) and at Cheju Island, South Korea (ACE-Asia). These measurements, in conjunction with aerosol-free model simulations, are used to determine the radiative forcing at the surface for the visible, near-infrared, and total solar spectral bandpasses. During INDOEX the diurnally averaged broadband surface aerosol radiative forcing was -72.2+/- 5.5 W m-2 per unit optical depth at 500 nm with roughly half being contributed from the visible (-38.5+/- 4.0 W m-2). The corresponding results during ACE-Asia were: broadband -73.1+/- 9.7 W m-2, visible -41.7+/- 4.7 W m-2, and near infrared -36.3+/- -5.6 W m-2.

  4. Global Aerosol Radiative Forcing Derived from Sea WiFS-Inferred Aerosol Optical Properties

    NASA Technical Reports Server (NTRS)

    Chou, Ming-Dah; Chan, Pui-King; Wang, Menghua

    1999-01-01

    Aerosol optical properties inferred from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) radiance measurements are used to compute the aerosol shortwave radiative forcing using a radiative transfer model. The aerosol optical thickness at the wavelength of 865-nm is taken from the SeaWIFS archive. It is found that the nominal optical thickness over oceans ranges from 0.1 to 0.2. Using a maritime aerosol model and the radiances measured at the various SeaWiFS channels, the Angstrom exponent is determined to be 0.2174, the single-scattering albedo to be 0.995, and the asymmetry factor to be 0.786. The radiative transfer model has eight bands in the visible and ultraviolet spectral regions and three bands in the near infrared. It includes the absorption due to aerosols, water vapor, carbon dioxide, and oxygen, and the scattering due to aerosols and gases (Rayleigh scattering). The radiative forcing is computed over global oceans for four months (January, April, July, and October, 1998) to represent four seasons. It is found that the aerosol radiative forcing is large and changes significantly with seasons near the continents with large-scale forest fires and desert dust. Averaged over oceans and the four months, the aerosol radiative forcing is approximately 7 W/sq m at the top of the atmosphere. This large radiative forcing is expected to have a significant cooling effect on the Earth's climate as implied from simulations of a number of general circulation models.

  5. High efficiency CIP 10-I personal inhalable aerosol sampler

    NASA Astrophysics Data System (ADS)

    Görner, P.; Wrobel, R.; Simon, X.

    2009-02-01

    The CIP 10 personal aerosol sampler was first developed by Courbon for sampling the respirable fraction of mining dust. This respirable aerosol sampler was further improved by Fabries, then selectors for sampling thoracic and inhalable aerosols were designed. Kenny et al. evaluated the particle-size dependent sampling efficiency of the inhalable version in a large-scale wind tunnel using a life-size dummy. The authors found that the overall sampling efficiency decreases more rapidly than the CEN-ISO-ACGIH target efficiency curve. Görner and Witschger measured the aspiration efficiency of the CIP 10 omni-directional inlet. They found that the aspiration efficiency was high enough for inhalable aerosol sampling. This result led to the conclusion that the low sampling efficiency is due to some internal losses of the aspirated particles before they reach the final sampling stage, namely the CIP 10 rotating filter. Based on the assumption that the inhalable particles are selected at selector aspiration level, an experimental research project was conducted to improve particle transmission to the collection stage of the sampler. Two different inhalable selectors were designed by Görner and tested in a laboratory wind tunnel. The transmission efficiency of both models was measured by Roger following an experimental protocol described by Witschger. The T-shaped air flow circuit was finally adopted to draw the aspirated particles into the final collection stage of the CIP 10. Actually, in this selector, the almost horizontally aspirated particles should be conducted vertically to the rotating cup. In two previous prototypes, particles could be deposited in certain places by inertia (where the aerosol was forced to deviate drastically) or by sedimentation (where the aerosol decelerated). The aerodynamic behaviour of the adopted solution causes the particles to accelerate radially between two horizontal plates before they enter a vertical tube. This acceleration avoids the

  6. WRF-Chem Simulations of Aerosols and Anthropogenic Aerosol Radiative Forcing in East Asia

    SciTech Connect

    Gao, Yi; Zhao, Chun; Liu, Xiaohong; Zhang, Meigen; Leung, Lai-Yung R.

    2014-08-01

    This study aims to provide a first comprehensive evaluation of WRF-Chem for modeling aerosols and anthropogenic aerosol radiative forcing (RF) over East Asia. Several numerical experiments were conducted from November 2007 to December 2008. Comparison between model results and observations shows that the model can generally reproduce the observed spatial distributions of aerosol concentration, aerosol optical depth (AOD) and single scattering albedo (SSA) from measurements at different sites, including the relatively higher aerosol concentration and AOD over East China and the relatively lower AOD over Southeast Asia, Korean, and Japan. The model also depicts the seasonal variation and transport of pollutions over East Asia. Particulate matter of 10 um or less in the aerodynamic diameter (PM10), black carbon (BC), sulfate (SO42-), nitrate (NO3-) and ammonium (NH4+) concentrations are higher in spring than other seasons in Japan due to the pollutant transport from polluted area of East Asia. AOD is high over Southwest and Central China in winter, spring and autumn and over North China in summer while is low over South China in summer due to monsoon precipitation. SSA is lowest in winter and highest in summer. The model also captures the dust events at the Zhangye site in the semi-arid region of China. Anthropogenic aerosol RF is estimated to range from -5 to -20 W m-2 over land and -20 to -40 W m-2 over ocean at the top of atmosphere (TOA), 5 to 30 W m-2 in the atmosphere (ATM) and -15 to -40 W m-2 at the bottom (BOT). The warming effect of anthropogenic aerosol in ATM results from BC aerosol while the negative aerosol RF at TOA is caused by scattering aerosols such as SO4 2-, NO3 - and NH4+. Positive BC RF at TOA compensates 40~50% of the TOA cooling associated with anthropogenic aerosol.

  7. Observations of the spectral clear-sky aerosol forcing over the tropical Indian Ocean

    NASA Astrophysics Data System (ADS)

    Meywerk, Jens; Ramanathan, V.

    1999-10-01

    During the first field phase (FFP) of the Indian Ocean Experiment (INDOEX) in February and March, 1998, the spectral global and direct beam irradiance have been measured between 350 and 1050 nm wavelengths using a 512-channel, fixed grating, photodiode array spectroradiometer. A detailed analysis of the instrument's reliability, the absolute calibration, and the corrections for deviation from the ideal cosine response are presented. For most of the spectral region the total uncertainty is shown to be <2%. The spectral optical depth, the spectral aerosol forcing, and the aerosol forcing for the photosynthetically active radiation have been derived from direct beam measurements and global irradiance measurements. The optical depth at 500 nm wavelength decreases from ˜0.5 in the northern Arabian Sea to as low as 0.05 south of the Intertropical Convergence Zone (ITCZ) near ˜15°S latitude. The surface aerosol forcing efficiency is defined as the rate of change of net irradiance at the surface due to an increase by 1 in optical depth at 500 nm. The normalization procedure we adopt to determine the aerosol forcing efficiency with respect to a reference pristine day in the Southern Hemisphere eliminates most of the radiometric calibration uncertainties. The continental aerosol south of the ITCZ shifts the peak in the direct solar radiation from 470 nm (for pristine conditions) to ˜580 nm for the polluted region. The spectral aerosol forcing efficiency peaks around 460 nm, with -1.2, -0.6, and +0.6 W m-2 nm-1 for the direct, global, and diffuse irradiance, dropping for the lower and higher wavelengths to about -0.3, -0.25, and 0.05 W m-2 nm-1 at 350 nm and -0.3, -0.1, and +0.2 at 1050 nm. Integrated over 400-700 nm, the aerosols decrease the noontime solar flux by as much as -38 W m-2 in the Arabian Sea to as little as -2 W m-2 south of the ITCZ. This introduces a strong north to south gradient in the climate forcing of the ocean. In addition, the strong aerosol

  8. A new method for evaluating the impact of vertical distribution on aerosol radiative forcing in general circulation models

    NASA Astrophysics Data System (ADS)

    Vuolo, M. R.; Schulz, M.; Balkanski, Y.; Takemura, T.

    2013-07-01

    enhancement when BC is found within clouds. BC forcing efficiency amounts to 44, 171, 333 and 178 W m-2 per unit optical depth for BC below, within, above clouds and for the 3-D BC distribution, respectively. The different behaviour of forcing nonlinearities for these three components of the atmospheric column suggests that, an important reason for differences between cloudy-sky aerosol forcings from different models may come from different aerosol and clouds vertical distributions. Our method allows to evaluate the contribution to model differences due to aerosol and clouds radiative interactions only, by reading 3-D aerosol and cloud fields from different GCMs, into the same model. This method avoids differences in calculating optical aerosol properties and forcing to enter into the discussion of inter-model differences. It appears that the above and in-cloud amount of BC is larger for SPRINTARS (190 compared to 179), increasing its cloudy-sky forcing efficiency with respect to LMDz, being thus potentially an important factor for inter-model differences.

  9. A Computationally Efficient Algorithm for Aerosol Phase Equilibrium

    SciTech Connect

    Zaveri, Rahul A.; Easter, Richard C.; Peters, Len K.; Wexler, Anthony S.

    2004-10-04

    Three-dimensional models of atmospheric inorganic aerosols need an accurate yet computationally efficient thermodynamic module that is repeatedly used to compute internal aerosol phase state equilibrium. In this paper, we describe the development and evaluation of a computationally efficient numerical solver called MESA (Multicomponent Equilibrium Solver for Aerosols). The unique formulation of MESA allows iteration of all the equilibrium equations simultaneously while maintaining overall mass conservation and electroneutrality in both the solid and liquid phases. MESA is unconditionally stable, shows robust convergence, and typically requires only 10 to 20 single-level iterations (where all activity coefficients and aerosol water content are updated) per internal aerosol phase equilibrium calculation. Accuracy of MESA is comparable to that of the highly accurate Aerosol Inorganics Model (AIM), which uses a rigorous Gibbs free energy minimization approach. Performance evaluation will be presented for a number of complex multicomponent mixtures commonly found in urban and marine tropospheric aerosols.

  10. Variability of aerosol optical depth and aerosol radiative forcing over Northwest Himalayan region

    NASA Astrophysics Data System (ADS)

    Saheb, Shaik Darga; Kant, Yogesh; Mitra, D.

    2016-05-01

    In recent years, the aerosol loading in India is increasing that has significant impact on the weather/climatic conditions. The present study discusses the analysis of temporal (monthly and seasonal) variation of aerosol optical depth(AOD) by the ground based observations from sun photometer and estimate the aerosol radiative forcing and heating rate over selected station Dehradun in North western Himalayas, India during 2015. The in-situ measurements data illustrate that the maximum seasonal average AOD observed during summer season AOD at 500nm ≍ 0.59+/-0.27 with an average angstrom exponent, α ≍0.86 while minimum during winter season AOD at 500nm ≍ 0.33+/-0.10 with angstrom exponent, α ≍1.18. The MODIS and MISR derived AOD was also compared with the ground measured values and are good to be in good agreement. Analysis of air mass back trajectories using HYSPLIT model reveal that the transportation of desert dust during summer months. The Optical Properties of Aerosols and clouds (OPAC) model was used to compute the aerosol optical properties like single scattering albedo (SSA), Angstrom coefficient (α) and Asymmetry(g) parameter for each day of measurement and they are incorporated in a Discrete Ordinate Radiative Transfer model, i.e Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) to estimate the direct short-wave (0.25 to 4 μm) Aerosol Radiative forcing at the Surface (SUR), the top-of-atmosphere (TOA) and Atmosphere (ATM). The maximum Aerosol Radiative Forcing (ARF) was observed during summer months at SUR ≍ -56.42 w/m2, at TOA ≍-21.62 w/m2 whereas in ATM ≍+34.79 w/m2 with corresponding to heating rate 1.24°C/day with in lower atmosphere.

  11. Aerosol Properties and Radiative Forcing over Kanpur during Severe Aerosol Loading Conditions

    SciTech Connect

    Kaskaoutis, D. G.; Sinha, P. R.; Vinoj, V.; Kosmopoulos, P. G.; Tripathi, S. N.; Misra, Amit; Sharma, M.; Singh, R. P.

    2013-11-01

    Atmospheric aerosols over India exhibit large spatio-temporal fluctuation driven by the local monsoon system, emission rates and seasonally-changed air masses. The northern part of India is well-known for its high aerosol loading throughout the year due to anthropogenic emissions, dust influence and biomass burning. On certain circumstances and, under favorable weather conditions, the aerosol load can be severe, causing significant health concerns and climate implications. The present work analyzes the aerosol episode (AE) days and examines the modification in aerosol properties and radiative forcing during the period 2001-2010 based on Kanpur-AERONET sun photometer data. As AEs are considered the days having daily-mean aerosol optical depth (AOD) above the decadal mean + 1 STD (standard deviation); the threshold value is defined at 0.928. The results identify 277 out of 2095 days (13.2%) of AEs over Kanpur, which are most frequently observed during post-monsoon (78 cases, 18.6%) and monsoon (76, 14.7%) seasons due to biomass-burning episodes and dust influence, respectively. On the other hand, the AEs in winter and pre-monsoon are lower in both absolute and percentage values (65, 12.5% and 58, 9.1%, respectively). The modification in aerosol properties on the AE days is strongly related to season. Thus, in post-monsoon and winter the AEs are associated with enhanced presence of fine-mode aerosols and Black Carbon from anthropogenic pollution and any kind of burning, while in pre-monsoon and monsoon seasons they are mostly associated with transported dust. Aerosol radiative forcing (ARF) calculated using SBDART shows much more surface (~-69 to -97 Wm-2) and Top of Atmosphere cooling (-20 to -30 Wm-2) as well as atmospheric heating (~43 to 71 Wm-2) during the AE days compared to seasonal means. These forcing values are mainly controlled by the higher AODs and the modified aerosol characteristics (Angstrom α, SSA) during the AE days in each season and may cause

  12. WRF-Chem simulations of aerosols and anthropogenic aerosol radiative forcing in East Asia

    NASA Astrophysics Data System (ADS)

    Gao, Yi; Zhao, Chun; Liu, Xiaohong; Zhang, Meigen; Leung, L. Ruby

    2014-08-01

    This study aims to provide a first comprehensive evaluation of WRF-Chem for modeling aerosols and anthropogenic aerosol radiative forcing (RF, including direct, semi-direct and indirect forcing) over East Asia. Several numerical experiments were conducted from November 2007 to December 2008. Comparison between model results and observations shows that the model can generally reproduce the observed spatial distributions of aerosol concentration, aerosol optical depth (AOD) and single scattering albedo (SSA) from measurements at many sites, including the relatively higher aerosol concentration and AOD over East China and the relatively lower AOD over Southeast Asia, Korea, and Japan. The model also depicts the seasonal variation and transport of pollutions over East Asia. Particulate matter of 10 μm or less in the aerodynamic diameter (PM10), black carbon (BC), sulfate (SO42-), nitrate (NO3-) and ammonium (NH4+) concentrations are higher in spring than other seasons in Japan, which indicates the possible influence of pollutant transport from polluted area of East Asia. The model underestimates SO42- and organic carbon (OC) concentrations over mainland China by about a factor of 2, while overestimates NO3- concentration in autumn along the Yangtze River. The model captures the dust events at the Zhangye site in the semi-arid region of China. AOD is high over Southwest and Central China in winter and spring and over North China in winter, spring and summer while is low over South China in summer due to monsoon precipitation. SSA is lowest in winter and highest in summer. Anthropogenic aerosol RF is estimated to range from -5 to -20 W m-2 over land and -20 to -40 W m-2 over adjacent oceans at the top of atmosphere (TOA), 5-30 W m-2 in the atmosphere (ATM) and -15 to -40 W m-2 at the bottom (BOT). The warming effect of anthropogenic aerosol in ATM results from BC aerosol while the negative aerosol RF at TOA is caused by scattering aerosols such as SO42-, NO3- and NH4

  13. Historical anthropogenic radiative forcing of changes in biogenic secondary aerosol

    NASA Astrophysics Data System (ADS)

    Acosta Navarro, Juan; D'Andrea, Stephen; Pierce, Jeffrey; Ekman, Annica; Struthers, Hamish; Zorita, Eduardo; Guenther, Alex; Arneth, Almut; Smolander, Sampo; Kaplan, Jed; Farina, Salvatore; Scott, Catherine; Rap, Alexandru; Farmer, Delphine; Spracklen, Domink; Riipinen, Ilona

    2016-04-01

    Human activities have lead to changes in the energy balance of the Earth and the global climate. Changes in atmospheric aerosols are the second largest contributor to climate change after greenhouse gases since 1750 A.D. Land-use practices and other environmental drivers have caused changes in the emission of biogenic volatile organic compounds (BVOCs) and secondary organic aerosol (SOA) well before 1750 A.D, possibly causing climate effects through aerosol-radiation and aerosol-cloud interactions. Two numerical emission models LPJ-GUESS and MEGAN were used to quantify the changes in aerosol forming BVOC emissions in the past millennium. A chemical transport model of the atmosphere (GEOS-Chem-TOMAS) was driven with those BVOC emissions to quantify the effects on radiation caused by millennial changes in SOA. We found that global isoprene emissions decreased after 1800 A.D. by about 12% - 15%. This decrease was dominated by losses of natural vegetation, whereas monoterpene and sesquiterpene emissions increased by about 2% - 10%, driven mostly by rising surface air temperatures. From 1000 A.D. to 1800 A.D, isoprene, monoterpene and sesquiterpene emissions decline by 3% - 8% driven by both, natural vegetation losses, and the moderate global cooling between the medieval climate anomaly and the little ice age. The millennial reduction in BVOC emissions lead to a 0.5% to 2% reduction in climatically relevant aerosol particles (> 80 nm) and cause a direct radiative forcing between +0.02 W/m² and +0.07 W/m², and an indirect radiative forcing between -0.02 W/m² and +0.02 W/m².

  14. Aerosol and ozone radiative forcing 1990-2015

    NASA Astrophysics Data System (ADS)

    Myhre, Cathrine Lund; Myhre, Gunnar; Samset, Bjørn H.; Schulz, Michael

    2016-04-01

    The regional changes in economic growth and pollution regulations have caused large changes in the geographical distribution of emissions of precursors and components affecting the radiation balance. Here we use recently updated emission data over the 1990-2015 period in eight global aerosol models to simulate aerosol and ozone changes and their radiative forcing. The models reproduce the general large-scale changes in aerosol and ozone changes over this period. The surface particle mass changes is simulated to 2-3 %/yr for the total fine particle concentration over main industrialized regions. Six models simulated changes in PM2.5 (particulate matter with aerodynamic diameters less 2.5 μm) over the 1990-2015 period. Observations of changes in PM2.5 are available for selected regions and time periods. The available PM2.5 trends from observations and model mean results are compared and for Europe the observed trend is 20% stronger than the model-mean over the 2000-2010 period. Over the 1990-2010 period the US observed changes are 13% lower than the simulated changes. Despite this relatively promising result, the agreement over US for the 2000-2010 period is poor. The reasons for this will be further explored. The forcing for ozone and aerosols increase over the 1990-2015 period and more positive relative to results in IPCC AR5. The main reason for a positive aerosol forcing over this period is explained by a substantial reduction of global mean SO2 emissions, in parallel with increasing black carbon emissions.

  15. New liquid aerosol generation devices: systems that force pressurized liquids through nozzles.

    PubMed

    Geller, David E

    2002-12-01

    Over the past few decades, aerosol delivery devices have been relatively inefficient, wasteful, and difficult for patients to use. These drawbacks have been tolerated because the drugs available for inhalation have wide therapeutic margins and steep dose-response curves at low doses. Recently several forces have converged to drive innovation in the aerosol device industry: the ban on chlorofluorocarbon propellants in metered-dose inhalers, the need for more user-friendly devices, and the invention of expensive inhalable therapies for topical and systemic lung delivery. Numerous devices are in development to improve the efficiency, ease of use, and reproducibility of aerosol delivery to the lung, including systems that force liquid through a nozzle to form the aerosol cloud. The Respimat is a novel, compact, propellant-free, multi-dose inhaler that employs a spring to push drug solution through a nozzle, which generates a slow-moving aerosol. Deposition studies show that the Respimat can deliver 39-44% of a dose to the lungs. Clinical asthma and chronic obstructive pulmonary disease trials with bronchodilators show that the Respimat is 2-8 times as effective as a metered-dose inhaler. Respimat has been tested with bronchodilators and inhaled corticosteroids. The AERx device uses sophisticated electronics to deliver aerosol from a single-dose blister, using an integral, disposable nozzle array. The electronics control dose expression and titration, timing of aerosol generation with the breath, and provide feedback for proper inhalation technique. Lung deposition ranges from 50 to 80% of the loaded dose, with remarkable reproducibility. AERx has been tested with a variety of drugs, for both topical and systemic delivery, including rhDNase (dornase alfa), insulin, and opioids. These novel devices face competition from other technologies as well as financial and regulatory hurdles, but they both offer a marked improvement in the efficiency of pulmonary drug delivery.

  16. Observationally constrained estimates of carbonaceous aerosol radiative forcing.

    PubMed

    Chung, Chul E; Ramanathan, V; Decremer, Damien

    2012-07-17

    Carbonaceous aerosols (CA) emitted by fossil and biomass fuels consist of black carbon (BC), a strong absorber of solar radiation, and organic matter (OM). OM scatters as well as absorbs solar radiation. The absorbing component of OM, which is ignored in most climate models, is referred to as brown carbon (BrC). Model estimates of the global CA radiative forcing range from 0 to 0.7 Wm(-2), to be compared with the Intergovernmental Panel on Climate Change's estimate for the pre-Industrial to the present net radiative forcing of about 1.6 Wm(-2). This study provides a model-independent, observationally based estimate of the CA direct radiative forcing. Ground-based aerosol network data is integrated with field data and satellite-based aerosol observations to provide a decadal (2001 through 2009) global view of the CA optical properties and direct radiative forcing. The estimated global CA direct radiative effect is about 0.75 Wm(-2) (0.5 to 1.0). This study identifies the global importance of BrC, which is shown to contribute about 20% to 550-nm CA solar absorption globally. Because of the inclusion of BrC, the net effect of OM is close to zero and the CA forcing is nearly equal to that of BC. The CA direct radiative forcing is estimated to be about 0.65 (0.5 to about 0.8) Wm(-2), thus comparable to or exceeding that by methane. Caused in part by BrC absorption, CAs have a net warming effect even over open biomass-burning regions in Africa and the Amazon. PMID:22753522

  17. Observationally constrained estimates of carbonaceous aerosol radiative forcing.

    PubMed

    Chung, Chul E; Ramanathan, V; Decremer, Damien

    2012-07-17

    Carbonaceous aerosols (CA) emitted by fossil and biomass fuels consist of black carbon (BC), a strong absorber of solar radiation, and organic matter (OM). OM scatters as well as absorbs solar radiation. The absorbing component of OM, which is ignored in most climate models, is referred to as brown carbon (BrC). Model estimates of the global CA radiative forcing range from 0 to 0.7 Wm(-2), to be compared with the Intergovernmental Panel on Climate Change's estimate for the pre-Industrial to the present net radiative forcing of about 1.6 Wm(-2). This study provides a model-independent, observationally based estimate of the CA direct radiative forcing. Ground-based aerosol network data is integrated with field data and satellite-based aerosol observations to provide a decadal (2001 through 2009) global view of the CA optical properties and direct radiative forcing. The estimated global CA direct radiative effect is about 0.75 Wm(-2) (0.5 to 1.0). This study identifies the global importance of BrC, which is shown to contribute about 20% to 550-nm CA solar absorption globally. Because of the inclusion of BrC, the net effect of OM is close to zero and the CA forcing is nearly equal to that of BC. The CA direct radiative forcing is estimated to be about 0.65 (0.5 to about 0.8) Wm(-2), thus comparable to or exceeding that by methane. Caused in part by BrC absorption, CAs have a net warming effect even over open biomass-burning regions in Africa and the Amazon.

  18. Aerosol Radiative Forcing Derived From SeaWIFS - Retrieved Aerosol Optical Properties

    NASA Technical Reports Server (NTRS)

    Chou, Mong-Dah; Chan, Pui-King; Wang, Menghua; Einaudi, Franco (Technical Monitor)

    2000-01-01

    To understand climatic implications of aerosols over global oceans, the aerosol optical properties retrieved from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) are analyzed, and the effects of the aerosols on the Earth's radiation budgets (aerosol radiative forcing, ARF) are computed using a radiative transfer model. It is found that the distribution of the SeaWiFS-retrieved aerosol optical thickness is distinctively zonal. The maximum in the equatorial region coincides with the Intertropical Convergence Zone, and the maximum in the Southern Hemispheric high latitudes coincides with the region of prevailing westerlies. The minimum aerosol optical thickness is found in the subtropical high pressure regions, especially in the Southern Hemisphere. These zonal patterns clearly demonstrate the influence of atmospheric circulation on the oceanic aerosol distribution. Over global oceans, aerosols reduce the annual mean net downward solar flux by 5.4 W m-2 at the top of the atmosphere and by 6.1 W m-2 at the surface. The largest ARF is found in the tropical Atlantic, Arabian Sea, Bay of Bengal, the coastal regions of Southeast and East Asia, and the Southern Hemispheric high latitudes. During the period of the Indonesian big fires (September-December 1997), the cooling due to aerosols is greater than 15 W m-2 at the top of the atmosphere and greater than 30 W m(exp -1) at the surface in the vicinity of the maritime continents. The atmosphere receives extra solar radiation by greater than 15 W m(exp -1) over a large area. These large changes in radiative fluxes are expected to have enhanced the atmospheric stability, weakened the atmospheric circulation, and augmented the drought condition during that period. It would be very instructive to simulate the regional climatic. The model-calculated clear sky solar flux at the top of the atmosphere is compared with that derived from the Clouds and the Earth's Radiant Energy System (CERES). The net downward solar flux of

  19. New Directions: Emerging Satellite Observations of Above-cloud Aerosols and Direct Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Yu, Hongbin; Zhang, Zhibo

    2013-01-01

    Spaceborne lidar and passive sensors with multi-wavelength and polarization capabilities onboard the A-Train provide unprecedented opportunities of observing above-cloud aerosols and direct radiative forcing. Significant progress has been made in recent years in exploring these new aerosol remote sensing capabilities and generating unique datasets. The emerging observations will advance the understanding of aerosol climate forcing.

  20. Microphysical and compositional influences on shortwave radiative forcing of climate by sulfate aerosols

    SciTech Connect

    Schwartz, S.E.; Wagener, R.; Nemesure, S.

    1995-02-01

    Anthropogenic sulfate aerosols scatter shortwave (solar) radiation iincident upon the atmosphere, thereby exerting a cooling influence on climate relative to pre-industrial times. Previous estimates of this forcing place its global and annual average value at about {minus}1 W M{sup {minus}2}, uncertain to a factor of somewhat more than 2, comparable in magnitude to greenhouse gas forcing over the same period but opposite in sign and much more uncertain. Key sources of uncertainty are atmospheric chemistry factors (yield, residence time), and microphysical factors (scattering efficiency, upscatter fraction, and the dependence of these quantities on particle size and relative humidity, RH). This paper examines these microphysical influences to indentify properties required to obtain more a accurate description of this forcing. The mass scattering efficiency exhibits a maximum at a particle diameter ({approximately}0.5 {mu}m) roughly equal to the wavelength of maximum power in the solar spectrum and roughly equal to diameter typical of anthropogenic sulfate aerosols. Particle size, and hence mass scattering efficiency, increase with increasing on RH because of accretion of water by deliquescent salt aerosols.

  1. Evapo-transpiration, role of aerosol radiative forcing: a study over a dense canopy

    NASA Astrophysics Data System (ADS)

    Bhanage, VInayak; Latha, R.; Murthy, B. S.

    2016-05-01

    Current study uses Satellite and Reanalysis data to quantify the effect of aerosol on ET at various space and time scales. All the data are obtained for the period June 2008 to May 2009 over Dibrugarh district, Assam, Indi a where NDVI has limited change of through the year. Monthly Evapo-Transpiration (ET, cumulative), Normalized Difference Vegetation Index (NDVI) and Aerosol Optical Depth (AOD) are retrieved from satellite images of Terra-MODIS. The AOD data are evaluated against in-situ observations. Maximum values of AOD are observed in the pre-monsoon season while minimum AOD values are perceived in October and November. Aerosol Radiative Forcing (ARF) is calculated by using the MERRA data sets of `clean-clear radiation' and `clear-radiation' at surface over the study area. Maximum aerosol radiative forcing is observed during the pre-monsoon season; this is in tune with ground observations. Strong positive correlation (r=0.75) between ET and NDVI is observed and it is found that the dense vegetative surfaces exhibit higher rate of evapo-transpiration. A strong positive correlation (r= -0.85) between ARF at surface and AOD is observed with radiative forcing efficiency of 35 W/m2. A statistical regression equation of ET a s a function of NDVI and AOD i.e. ET = 0.25 + (-84.27) * AOD + (131.51) * NDVI, is obtained that shows a correlation of 0.824.

  2. Modeling of aerosol properties related to direct climate forcing

    NASA Astrophysics Data System (ADS)

    Koloutsou-Vakakis, Sotiria; Rood, Mark J.; Nenes, Athanasios; Pilinis, Christodoulos

    1998-07-01

    A long-term local experiment was designed with the purpose to accurately quantify aerosol parameters needed in order to estimate aerosol climate forcing at an anthropogenically perturbed continental site. Total light-scattering σλ,sp and backscattering σλ,bsp coefficients at wavelength λ, the hygroscopic growth factors with respect to scattering, ƒ(RH)λ,s, and the backscatter ratio bλ are the parameters considered in the paper. Reference and controlled relative humidity nephelometry measurements were taken at a ground level field sampling station, located near Bondville Illinois (40°03'12″N, W 88°22'19″W). Aerosol particle chemical composition and mass particle size distributions were also measured. The target parameters were also estimated from models. The modeling approach involved a two-step process. In the first step, aerosol properties were parameterized with an approach that made use of a modified thermodynamic equilibrium model, published laboratory measurements of single hygroscopic particle properties, and empirical mixing rules. In the second step, the parameterized aerosol properties were used as inputs into a code that calculate σλ,sp and σλ,bsp as functions of λ, RH, particle size, and composition. Comparison between the measured and the modeled results showed that depending on the assumptions, the differences between the modeled and observed results were within 5 to 28% for ƒ(RH)λ,s and within 22-35% for bλ at low RH and 0-20% for bλ at high RH. The temporal variation of the particle size distribution, the equilibrium state of the particles, and the hygroscopicity of the material characterized as residual were the major factors limiting the predictive ability of the models.

  3. The relative roles of sulfate aerosols and greenhouse gases in climate forcing

    NASA Technical Reports Server (NTRS)

    Kiehl, J. T.; Briegleb, B. P.

    1993-01-01

    Calculations of the effects of both natural and anthropogenic tropospheric sulfate aerosols indicate that the aerosol climate forcing is sufficiently large in a number of regions of the Northern Hemisphere to reduce significantly the positive forcing from increased greenhouse gases. Summer sulfate aerosol forcing in the Northern Hemisphere completely offsets the greenhouse forcing over the eastern United States and central Europe. Anthropogenic sulfate aerosols contribute a globally averaged annual forcing of -0.3 watt per square meter as compared with +2.1 watts per square meter for greenhouse gases. Sources of the difference in magnitude with the previous estimate of Charlson et al. (1992) are discussed.

  4. The Impact of humidity above stratiform clouds on indirect aerosol climate forcing

    SciTech Connect

    Ackerman, A S; Kirkpatrick, M P; Stevens, D E; Toon, O B

    2004-12-20

    Some of the global warming effect of anthropogenic greenhouse gases is offset by increased solar reflection from clouds with smaller droplets that form on increased numbers of cloud condensation nuclei in polluted air. The global magnitude of the resulting indirect aerosol climate forcing is estimated to be comparable (and opposed) to the anthropogenic carbon dioxide forcing, but estimates are highly uncertain because of complexities in characterizing the physical process that determine global aerosol and cloud populations and their interactions. Beyond reflecting sunlight more effectively, smaller droplets are less efficient at producing precipitation, and decreased precipitation is expected to result in increased cloud water and cloud cover, further increasing the indirect forcing. Yet polluted marine boundary-layer clouds are not generally observed to hold more water. Here we use model simulations of stratocumulus clouds to 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 moist. Otherwise, aerosol induced suppression of precipitation enhances entrainment of overlying dry air, thereby reducing cloud water and diminishing the indirect climate forcing.

  5. EVALUATION OF ACOUSTIC FORCES ON A PARTICLE IN AEROSOL MEDIUM

    SciTech Connect

    Lee, S; Richard Dimenna, R

    2007-09-27

    The acoustic force exerted on a solid particle was evaluated to develop a fundamental understanding of the critical physical parameters or constraints affecting particle motion and capture in a collecting device. The application of an acoustic force to the collection of a range of submicron-to-micron particles in a highly turbulent airflow stream laden with solid particles was evaluated in the presence of other assisting and competing forces. This scoping estimate was based on the primary acoustic force acting directly on particles in a dilute aerosol system, neglecting secondary interparticle effects such as agglomeration of the sub-micron particles. A simplified analysis assuming a stable acoustic equilibrium with an infinite sound speed in the solid shows that for a solid-laden air flow in the presence of a standing wave, particles will move toward the nearest node. The results also show that the turbulent drag force on a 1-{micro}m particle resulting from eddy motion is dominant when compared with the electrostatic force or the ultrasonic acoustic force. At least 180 dB acoustic pressure level at 1 MHz is required for the acoustic force to be comparable to the electrostatic or turbulent drag forces in a high-speed air stream. It is noted that particle size and pressure amplitude are dominant parameters for the acoustic force. When acoustic pressure level becomes very large, the acoustic energy will heat up the surrounding air medium, which may cause air to expand. With an acoustic power of about 600 watts applied to a 2000-lpm air flow, the air temperature can increase by as much as 15 C at the exit of the collector.

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

    SciTech Connect

    Yu, Fangqun; Luo, Gan; Liu, Xiaohong; Easter, Richard C.; Ma, Xiaoyan; Ghan, Steven J.

    2012-12-03

    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 for the first time a physically based treatment of IMN into the Community Atmosphere Model version 5. Our simulations show that, compared to globally averaged results based on 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 by 3.67 W/m2 (more negative) and longwave cloud forcing by 1.78 W/m2 (more positive), resulting in a -1.9 W/m2 net change in cloud radiative forcing associated with IMN. The significant impacts of ionization on global aerosol formation, CCN abundance, and cloud radiative forcing may provide an important physical mechanism linking the global energy balance to various processes affecting atmospheric ionization, which should be properly represented in climate models.

  7. Aerosol detection efficiency in inductively coupled plasma mass spectrometry

    DOE PAGES

    Hubbard, Joshua A.; Zigmond, Joseph A.

    2016-03-02

    We used an electrostatic size classification technique to segregate particles of known composition prior to being injected into an inductively coupled plasma mass spectrometer (ICP-MS). Moreover, we counted size-segregated particles with a condensation nuclei counter as well as sampled with an ICP-MS. By injecting particles of known size, composition, and aerosol concentration into the ICP-MS, efficiencies of the order of magnitude aerosol detection were calculated, and the particle size dependencies for volatile and refractory species were quantified. Similar to laser ablation ICP-MS, aerosol detection efficiency was defined as the rate at which atoms were detected in the ICP-MS normalized bymore » the rate at which atoms were injected in the form of particles. This method adds valuable insight into the development of technologies like laser ablation ICP-MS where aerosol particles (of relatively unknown size and gas concentration) are generated during ablation and then transported into the plasma of an ICP-MS. In this study, we characterized aerosol detection efficiencies of volatile species gold and silver along with refractory species aluminum oxide, cerium oxide, and yttrium oxide. Aerosols were generated with electrical mobility diameters ranging from 100 to 1000 nm. In general, it was observed that refractory species had lower aerosol detection efficiencies than volatile species, and there were strong dependencies on particle size and plasma torch residence time. Volatile species showed a distinct transition point at which aerosol detection efficiency began decreasing with increasing particle size. This critical diameter indicated the largest particle size for which complete particle detection should be expected and agreed with theories published in other works. Aerosol detection efficiencies also displayed power law dependencies on particle size. Aerosol detection efficiencies ranged from 10-5 to 10-11. Free molecular heat and mass transfer theory was

  8. Aerosol detection efficiency in inductively coupled plasma mass spectrometry

    NASA Astrophysics Data System (ADS)

    Hubbard, Joshua A.; Zigmond, Joseph A.

    2016-05-01

    An electrostatic size classification technique was used to segregate particles of known composition prior to being injected into an inductively coupled plasma mass spectrometer (ICP-MS). Size-segregated particles were counted with a condensation nuclei counter as well as sampled with an ICP-MS. By injecting particles of known size, composition, and aerosol concentration into the ICP-MS, efficiencies of the order of magnitude aerosol detection were calculated, and the particle size dependencies for volatile and refractory species were quantified. Similar to laser ablation ICP-MS, aerosol detection efficiency was defined as the rate at which atoms were detected in the ICP-MS normalized by the rate at which atoms were injected in the form of particles. This method adds valuable insight into the development of technologies like laser ablation ICP-MS where aerosol particles (of relatively unknown size and gas concentration) are generated during ablation and then transported into the plasma of an ICP-MS. In this study, we characterized aerosol detection efficiencies of volatile species gold and silver along with refractory species aluminum oxide, cerium oxide, and yttrium oxide. Aerosols were generated with electrical mobility diameters ranging from 100 to 1000 nm. In general, it was observed that refractory species had lower aerosol detection efficiencies than volatile species, and there were strong dependencies on particle size and plasma torch residence time. Volatile species showed a distinct transition point at which aerosol detection efficiency began decreasing with increasing particle size. This critical diameter indicated the largest particle size for which complete particle detection should be expected and agreed with theories published in other works. Aerosol detection efficiencies also displayed power law dependencies on particle size. Aerosol detection efficiencies ranged from 10- 5 to 10- 11. Free molecular heat and mass transfer theory was applied, but

  9. Detecting cross-equatorial wind change as a fingerprint of climate response to anthropogenic aerosol forcing

    NASA Astrophysics Data System (ADS)

    Wang, Hai; Xie, Shang-Ping; Tokinaga, Hiroki; Liu, Qinyu; Kosaka, Yu

    2016-04-01

    Anthropogenic aerosols are a major driver of the twetieth century climate change. In climate models, the aerosol forcing, larger in the Northern than Southern Hemispheres, induces an interhemispheric Hadley circulation. In support of the model result, we detected a robust change in the zonal mean cross-equatorial wind over the past 60 years from ship observations and reanalyses, accompanied by physically consistent changes in atmospheric pressure and marine cloud cover. Single-forcing experiments indicate that the observed change in cross-equatorial wind is a fingerprint of aerosol forcing. This zonal mean mode follows the evolution of global aerosol forcing that is distinct from regional changes in the Atlantic sector. Atmospheric simulations successfully reproduce this interhemispheric mode, indicating the importance of sea surface temperature mediation in response to anthropogenic aerosol forcing. As societies awaken to reduce aerosol emissions, a phase reversal of this interhemispheric mode is expected in the 21st century.

  10. Can satellite-derived aerosol optical depth quantify the surface aerosol radiative forcing?

    NASA Astrophysics Data System (ADS)

    Xu, Hui; Ceamanos, Xavier; Roujean, Jean-Louis; Carrer, Dominique; Xue, Yong

    2014-12-01

    Aerosols play an important role in the climate of the Earth through aerosol radiative forcing (ARF). Nowadays, aerosol particles are detected, quantified and monitored by remote sensing techniques using low Earth orbit (LEO) and geostationary (GEO) satellites. In the present article, the use of satellite-derived AOD (aerosol optical depth) products is investigated in order to quantify on a daily basis the ARF at the surface level (SARF). By daily basis we mean that an average SARF value is computed every day based upon the available AOD satellite measurements for each station. In the first part of the study, the performance of four state-of-art different AOD products (MODIS-DT, MODIS-DB, MISR, and SEVIRI) is assessed through comparison against ground-based AOD measurements from 24 AERONET stations located in Europe and Africa during a 6-month period. While all AOD products are found to be comparable in terms of measured value (RMSE of 0.1 for low and average AOD values), a higher number of AOD estimates is made available by GEO satellites due to their enhanced frequency of scan. Experiments show a general lower agreement of AOD estimates over the African sites (RMSE of 0.2), which show the highest aerosol concentrations along with the occurrence of dust aerosols, coarse particles, and bright surfaces. In the second part of this study, the lessons learned about the confidence in aerosol burden derived from satellites are used to estimate SARF under clear sky conditions. While the use of AOD products issued from GEO observations like SEVIRI brings improvement in the SARF estimates with regard to LEO-based AOD products, the resulting absolute bias (13 W/m2 in average when AERONET AOD is used as reference) is judged to be still high in comparison with the average values of SARF found in this study (from - 25 W/m2 to - 43 W/m2) and also in the literature (from - 10 W/m2 to - 47 W/m2).

  11. A Physically-Based Estimate of Radiative Forcing by Anthropogenic Sulfate Aerosol

    SciTech Connect

    Ghan, Steven J. ); Easter, Richard C. ); Chapman, Elaine G. ); Abdul-Razzak, Hayder; Zhang, Yang ); Leung, Ruby ); Laulainen, Nels S. ); Saylor, Rick D. ); Zaveri, Rahul A. )

    2001-04-01

    Estimates of direct and indirect radiative forcing by anthropogenic sulfate aerosols from an integrated global aerosol and climate modeling system are presented. A detailed global tropospheric chemistry and aerosol model that predicts concentrations of oxidants as well as aerosols and aerosol precursors, is coupled to a general circulation model that predicts both cloud water mass and cloud droplet number. Both number and mass of several externally-mixed aerosol size modes are predicted, with internal mixing assumed for the different aerosol components within each mode. Predicted aerosol species include sulfate, organic and black carbon, soil dust, and sea salt. The models use physically-based treatments of aerosol radiative properties (including dependence on relative humidity) and aerosol activation as cloud condensation nuclei. Parallel simulations with and without anthropogenic sulfate aerosol are performed for a global domain. The global and annual mean direct and indirect radiative forcing due to anthropogenic sulfate are estimated to be -0.3 to -0.5 and -1.5 to -3.0 W m-2, respectively. The radiative forcing is sensitive to the model's horizontal resolution, the use of predicted vs. analyzed relative humidity, the prediction vs. diagnosis of aerosol number and droplet number, and the parameterization of droplet collision/coalescence. About half of the indirect radiative forcing is due to changes in droplet radius and half to increased cloud liquid water.

  12. Experimental Assessment of Collection Efficiency of Submicron Aerosol Particles by Cloud Droplets

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Ardon-Dryer, K.; Cziczo, D. J.

    2013-12-01

    The interplay between aerosol particles and water droplets in the atmosphere, especially in clouds, influences both aerosol and cloud properties. The major uncertainty in our understanding of climate arises in the indirect effect of aerosol and their ability to impact cloud formation and consequently alter the global radiative balance. The collision between a water droplet and aerosol particles that results in coalescence is termed 'collection' or 'coagulation'. Coagulation can lead to aerosol removal from the atmosphere or induce ice nucleation via contact freezing at temperatures below 0 C. Theoretical studies have shown that for aerosol particles smaller than 0.1 micrometers, Brownian motion is important, and for particles with diameters larger than 1 micrometer, inertial force dominates. There is a collection efficiency minimum for particles between 0.1-2 micrometers, called the 'Greenfield Gap'. Experimental efforts, however, have been limited to very large drizzle and rain drops until recently, and constrained parameters necessary to describe particle collection efficiency by cloud droplets have not been available. One reason is that laboratory setups that allow for coagulation to be observed on a single-particle basis have been lacking. Collection efficiency is also an important parameter for studying and assessing contact ice nucleation. Contact ice nucleation is currently the least understood ice nucleation mechanism and can be potentially important for mixed-phase cloud formation. The significance of experimentally assessing collection efficiency is therefore two-fold: to first understand the frequency of contacts and to then understand the fraction that lead to ice nucleation. We have constructed the MIT-Contact Freezing Chamber (MIT-CFC) to study collection efficiency of submicron aerosol particles by cloud droplets and contact freezing. A stream of 30-micron cloud droplets fall freely into the chamber and collide with aerosol particles. The outflow

  13. On the relationship between aerosol model uncertainty and radiative forcing uncertainty

    PubMed Central

    Reddington, Carly L.; Carslaw, Kenneth S.

    2016-01-01

    The largest uncertainty in the historical radiative forcing of climate is caused by the interaction of aerosols with clouds. Historical forcing is not a directly measurable quantity, so reliable assessments depend on the development of global models of aerosols and clouds that are well constrained by observations. However, there has been no systematic assessment of how reduction in the uncertainty of global aerosol models will feed through to the uncertainty in the predicted forcing. We use a global model perturbed parameter ensemble to show that tight observational constraint of aerosol concentrations in the model has a relatively small effect on the aerosol-related uncertainty in the calculated forcing between preindustrial and present-day periods. One factor is the low sensitivity of present-day aerosol to natural emissions that determine the preindustrial aerosol state. However, the major cause of the weak constraint is that the full uncertainty space of the model generates a large number of model variants that are equally acceptable compared to present-day aerosol observations. The narrow range of aerosol concentrations in the observationally constrained model gives the impression of low aerosol model uncertainty. However, these multiple “equifinal” models predict a wide range of forcings. To make progress, we need to develop a much deeper understanding of model uncertainty and ways to use observations to constrain it. Equifinality in the aerosol model means that tuning of a small number of model processes to achieve model−observation agreement could give a misleading impression of model robustness. PMID:26848136

  14. On the relationship between aerosol model uncertainty and radiative forcing uncertainty.

    PubMed

    Lee, Lindsay A; Reddington, Carly L; Carslaw, Kenneth S

    2016-05-24

    The largest uncertainty in the historical radiative forcing of climate is caused by the interaction of aerosols with clouds. Historical forcing is not a directly measurable quantity, so reliable assessments depend on the development of global models of aerosols and clouds that are well constrained by observations. However, there has been no systematic assessment of how reduction in the uncertainty of global aerosol models will feed through to the uncertainty in the predicted forcing. We use a global model perturbed parameter ensemble to show that tight observational constraint of aerosol concentrations in the model has a relatively small effect on the aerosol-related uncertainty in the calculated forcing between preindustrial and present-day periods. One factor is the low sensitivity of present-day aerosol to natural emissions that determine the preindustrial aerosol state. However, the major cause of the weak constraint is that the full uncertainty space of the model generates a large number of model variants that are equally acceptable compared to present-day aerosol observations. The narrow range of aerosol concentrations in the observationally constrained model gives the impression of low aerosol model uncertainty. However, these multiple "equifinal" models predict a wide range of forcings. To make progress, we need to develop a much deeper understanding of model uncertainty and ways to use observations to constrain it. Equifinality in the aerosol model means that tuning of a small number of model processes to achieve model-observation agreement could give a misleading impression of model robustness.

  15. An observational approach for determining aerosol surface radiative forcing: Results from the first field phase of INDOEX

    NASA Astrophysics Data System (ADS)

    Conant, William C.

    2000-06-01

    This paper presents one of the few quantitative estimates of surface aerosol forcing made directly from surface irradiance observations. The method described within yields estimates of the forcing accurate to 20%. The study was conducted from February to March 1998 at the Kaashidhoo Climate Observatory (KCO) during the First Field Phase of the Indian Ocean Experiment (INDOEX-FFP). For the 400-700 nm region studied here, the forcing is -7.6±1.5 W m-2. The data are obtained from two photodiode radiometers measuring global and diffuse irradiance in five channels in the visible and ultraviolet. The instruments were chosen, calibrated, and deployed specifically for a precise measurement of aerosol forcing. The angular, spectral, and absolute response characteristics of the instruments are determined in the laboratory and used to calibrate the data, as described here. The accuracy in the calibrated data is 2.4% for the global irradiance and 1.8% for the diffuse irradiance. Direct aerosol forcing is obtained from the measured aerosol forcing efficiency, which is determined by two methods: hybrid and differential. The hybrid method uses a radiative transfer model to subtract out the contribution from the aerosol-free atmosphere. The differential method assumes that changes in 400-700 nm solar flux are forced by changes in aerosol optical depth. By using flux changes, the differential method is not sensitive to the small calibration uncertainties, and is independent of model assumptions about the single-scatter properties of the aerosol. For this soot-laden marine region south of India, a 0.1 change in aerosol optical depth produces a -4.0±0.8 W m-2; change in the 400-700 nm surface flux; 55% of this forcing is observed in the 400-540 nm region. The global and diffuse data agree to within 5 W m-2 of results calculated by a Monte Carlo radiative transfer model. The model assumes an aerosol consistent with the spectral optical depth, lidar vertical profiles, and surface

  16. Global Radiative Forcing of Coupled Tropospheric Ozone and Aerosols in a Unified General Circulation Model

    NASA Technical Reports Server (NTRS)

    Liao, Hong; Seinfeld, John H.; Adams, Peter J.; Mickley, Loretta J.

    2008-01-01

    Global simulations of sea salt and mineral dust aerosols are integrated into a previously developed unified general circulation model (GCM), the Goddard Institute for Space Studies (GISS) GCM II', that simulates coupled tropospheric ozone-NOx-hydrocarbon chemistry and sulfate, nitrate, ammonium, black carbon, primary organic carbon, and secondary organic carbon aerosols. The fully coupled gas-aerosol unified GCM allows one to evaluate the extent to which global burdens, radiative forcing, and eventually climate feedbacks of ozone and aerosols are influenced by gas-aerosol chemical interactions. Estimated present-day global burdens of sea salt and mineral dust are 6.93 and 18.1 Tg with lifetimes of 0.4 and 3.9 days, respectively. The GCM is applied to estimate current top of atmosphere (TOA) and surface radiative forcing by tropospheric ozone and all natural and anthropogenic aerosol components. The global annual mean value of the radiative forcing by tropospheric ozone is estimated to be +0.53 W m(sup -2) at TOA and +0.07 W m(sup -2) at the Earth's surface. Global, annual average TOA and surface radiative forcing by all aerosols are estimated as -0.72 and -4.04 W m(sup -2), respectively. While the predicted highest aerosol cooling and heating at TOA are -10 and +12 W m(sup -2) respectively, surface forcing can reach values as high as -30 W m(sup -2), mainly caused by the absorption by black carbon, mineral dust, and OC. We also estimate the effects of chemistry-aerosol coupling on forcing estimates based on currently available understanding of heterogeneous reactions on aerosols. Through altering the burdens of sulfate, nitrate, and ozone, heterogeneous reactions are predicted to change the global mean TOA forcing of aerosols by 17% and influence global mean TOA forcing of tropospheric ozone by 15%.

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

    NASA Astrophysics Data System (ADS)

    Yu, F.; Luo, G.; Liu, X.; Easter, R. C.; Ma, X.; Ghan, S. J.

    2012-12-01

    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.

  18. Estimation of aerosol direct forcing by Asian dust using sun/sky radiometer and lidar measurement

    NASA Astrophysics Data System (ADS)

    Won, J. G.; Yoon, S. C.; Holben, B.

    2002-12-01

    Appropriate optical parameters of aerosols are critical part for estimating aerosol direct forcing. We suggest a method of determining aerosol parameters for the radiative transfer model, CRM released by NCAR, from AERONET inversion data set. AERONET inversion provides size distribution and complex refractive indices at 4 wavelengths, 440, 670, 870 and 1020nm. Mie calculation can produce the aerosol optical parameters, such as aerosol optical thickness (AOT), single scattering albedo (SSA), asymmetry factor(g) and by using regression fitting method on log-log plane, the parameters at 19 channels of short wavelength region can be retrieved. With this method, it becomes possible to use ground-base solar radiance measurement data for calculating aerosol direct forcing without assuming the specific aerosol type in advance. We investigated the differences of aerosol forcing by dust and non-dust aerosols. Out of AERONET data collected in Apr. 2001, the properties of Asian dust aerosols were examined, which have the characteristics of bigger AOT, bigger SSA (bigger solar radiance reflection) and less wavelength dependence of SSA and g. This difference makes larger aerosol direct forcing at TOA and less atmospheric absorption. The aerosol profiles measured by lidar are also applied for radiative transfer calculation. The profiles of short wave radiation flux and heating rate by dust were investigated for two Asian dust events, one was elevated dust event and the other was dust event settling into the PBL. Instantaneous heating rate larger than 2K/day was estimated within dust aerosol layer and several differences of radiation flux profiles due to the aerosol profiles were investigated.

  19. Optical characteristics of the aerosol in Spain and Austria and its effect on radiative forcing

    NASA Astrophysics Data System (ADS)

    Horvath, H.; Alados Arboledas, L.; Olmo, F. J.; Jovanović, O.; Gangl, M.; Kaller, W.; SáNchez, C.; Sauerzopf, H.; Seidl, S.

    2002-10-01

    The horizontal and vertical attenuation of the aerosol, the sky radiance, and the light absorption coefficient of the aerosol have been determined at wavelengths in the visible. From this set of data the following optical characteristics of the atmospheric aerosol could be derived: vertical optical depth, horizontal extinction and absorption coefficient, scattering phase function, asymmetry parameter, and single scattering albedo. Campaigns have been performed in Almería, Spain, and Vienna, Austria. The aerosol undergoes a considerable variation, as experienced by many other studies. Sometimes the vertical and the horizontal measurements gave similar data; on other days the aerosol at the surface and the aerosol aloft were completely different. The "clearest" aerosol always had the smallest single scattering albedo and thus relatively the highest light absorption. The optical characteristics of the aerosol in the two very different locations were very similar. Using the measured optical data, a radiative transfer calculation was performed, and the radiation reaching the ground was calculated. Comparing the values for the clear aerosol and the days with higher aerosol load, the radiative forcing due to the additional aerosol particles could be determined. The forcing of the aerosol at the ground is always negative, and at the top of the atmosphere it is close to zero or slightly negative. Its dependence on wavelength and zenith angle is presented. The preindustrial aerosol in Europe was estimated, and the forcing due to the present-day aerosol was determined. At the surface it is negative, but at the top of the atmosphere it is close to zero or positive. This is caused by the light absorption of the European aerosol, which is higher than in most other locations.

  20. Large atmospheric shortwave radiative forcing by Mediterranean aerosols derived from simultaneous ground-based and spaceborne observations and dependence on the aerosol type and single scattering albedo

    NASA Astrophysics Data System (ADS)

    di Biagio, Claudia; di Sarra, Alcide; Meloni, Daniela

    2010-05-01

    Aerosol optical properties and shortwave irradiance measurements at the island of Lampedusa (central Mediterranean) during 2004-2007 are combined with Clouds and the Earth's Radiant Energy System observations of the outgoing shortwave flux at the top of the atmosphere (TOA). The measurements are used to estimate the surface (FES), the top of the atmosphere (FETOA), and the atmospheric (FEATM) shortwave aerosol forcing efficiencies for solar zenith angle (θ) between 15° and 55° for desert dust (DD), urban/industrial-biomass burning aerosols (UI-BB), and mixed aerosols (MA). The forcing efficiency at the different atmospheric levels is derived by applying the direct method, that is, as the derivative of the shortwave net flux versus the aerosol optical depth at fixed θ. The diurnal average forcing efficiency at the surface/TOA at the equinox is (-68.9 ± 4.0)/(-45.5 ± 5.4) W m-2 for DD, (-59.0 ± 4.3)/(-19.2 ± 3.3) W m-2 for UI-BB, and (-94.9 ± 5.1)/(-36.2 ± 1.7) W m-2 for MA. The diurnal average atmospheric radiative forcing at the equinox is (+7.3 ± 2.5) W m-2 for DD, (+8.4 ± 1.9) W m-2 for UI-BB, and (+8.2 ± 1.9) W m-2 for MA, suggesting that the mean atmospheric forcing is almost independent of the aerosol type. The largest values of the atmospheric forcing may reach +35 W m-2 for DD, +23 W m-2 for UI-BB, and +34 W m-2 for MA. FETOA is calculated for MA and 25° ≤ θ ≤ 35° for three classes of single scattering albedo (0.7 ≤ ω < 0.8, 0.8 ≤ ω < 0.9, and 0.9 ≤ ω ≤ 1) at 415.6 and 868.7 nm: FETOA increases, in absolute value, for increasing ω. A 0.1 increment in ω determines an increase in FETOA by 10-20 W m-2.

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

    NASA Astrophysics Data System (ADS)

    Thomas, G. E.; Chalmers, N.; Harris, B.; Grainger, R. G.; Highwood, E. J.

    2013-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Thomas, G. E.; Chalmers, N.; Harris, B.; Grainger, R. G.; Highwood, E. J.

    2012-07-01

    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.

  3. Tropospheric Aerosol Climate Forcing in Clear-Sky Satellite Observations over the Oceans.

    PubMed

    Haywood; Ramaswamy; Soden

    1999-02-26

    Tropospheric aerosols affect the radiative forcing of Earth's climate, but their variable concentrations complicate an understanding of their global influence. Model-based estimates of aerosol distributions helped reveal spatial patterns indicative of the presence of tropospheric aerosols in the satellite-observed clear-sky solar radiation budget over the world's oceans. The results show that, although geographical signatures due to both natural and anthropogenic aerosols are manifest in the satellite observations, the naturally occurring sea-salt is the leading aerosol contributor to the global-mean clear-sky radiation balance over oceans. PMID:10037595

  4. Climatic Effects of 1950-2050 Changes in US Anthropogenic Aerosols. Part 1; Aerosol Trends and Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Leibensperger, E. M.; Mickley, L. J.; Jacob, D. J.; Chen, W.-T.; Seinfeld, J. H.; Nenes, A.; Adams, P. J.; Streets, D. G.; Kumar, N.; Rind, D.

    2012-01-01

    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 deg W) of -2.0Wm(exp-2 for direct forcing including contributions from sulfate (-2.0Wm-2), nitrate (-0.2Wm(exp-2), organic carbon (-0.2Wm(exp-2), and black carbon (+0.4Wm(exp-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 0.8Wm(exp-2) direct and 1.0Wm(exp-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 (+0.3Wm(exp-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.

  5. Sensitivity of precipitation extremes to radiative forcing of greenhouse gases and aerosols

    NASA Astrophysics Data System (ADS)

    Lin, Lei; Wang, Zhili; Xu, Yangyang; Fu, Qiang

    2016-09-01

    Greenhouse gases (GHGs) and aerosols are the two most important anthropogenic forcing agents in the 21st century. The expected declines of anthropogenic aerosols in the 21st century from present-day levels would cause an additional warming of the Earth's climate system, which would aggravate the climate extremes caused by GHG warming. We examine the increased rate of precipitation extremes with global mean surface warming in the 21st century caused by anthropogenic GHGs and aerosols, using an Earth system model ensemble simulation. Similar to mean precipitation, the increased rate of precipitation extremes caused by aerosol forcing is significantly larger than that caused by GHG forcing. The aerosol forcing in the coming decades can play a critical role in inducing change in precipitation extremes if a lower GHG emission pathway is adopted. Our results have implications for policy-making on climate adaptation to extreme precipitation events.

  6. First Estimates of the Radiative Forcing of Aerosols Generated from Biomass Burning using Satellite Data

    NASA Technical Reports Server (NTRS)

    Chistopher, Sundar A.; Kliche, Donna V.; Chou, Joyce; Welch, Ronald M.

    1996-01-01

    Collocated measurements from the Advanced Very High Resolution Radiometer (AVHRR) and the Earth Radiation Budget Experiment (ERBE) scanner are used to examine the radiative forcing of atmospheric aerosols generated from biomass burning for 13 images in South America. Using the AVHRR, Local Area Coverage (LAC) data, a new technique based on a combination of spectral and textural measures is developed for detecting these aerosols. Then, the instantaneous shortwave, longwave, and net radiative forcing values are computed from the ERBE instantaneous scanner data. Results for the selected samples from 13 images show that the mean instantaneous net radiative forcing for areas with heavy aerosol loading is about -36 W/sq m and that for the optically thin aerosols are about -16 W/sq m. These results, although preliminary, provide the first estimates of radiative forcing of atmospheric aerosols from biomass burning using satellite data.

  7. First Estimates of the Radiative Forcing of Aerosols Generated from Biomass Burning Using Satellite Data

    NASA Technical Reports Server (NTRS)

    Christopher, Sundar A.; Kliche, Donna A.; Chou, Joyce; Welch, Ronald M.

    1996-01-01

    Collocated measurements from the Advanced Very High Resolution Radiometer (AVHRR) and the Earth Radiation Budget Experiment (ERBE) scanner are used to examine the radiative forcing of atmospheric aerosols generated from biomass burning for 13 images in South America. Using the AVHRR, Local Area Coverage (LAC) data, a new technique based on a combination of spectral and textural measures is developed for detecting these aerosols. Then, the instantaneous shortwave, longwave, and net radiative forcing values are computed from the ERBE instantaneous scanner data. Results for the selected samples from 13 images show that the mean instantaneous net radiative forcing for areas with heavy aerosol loading is about -36 W/sq m and that for the optically thin aerosols are about -16 W/sq m. These results, although preliminary, provide the first estimates of radiative forcing of atmospheric aerosols from biomass burning using satellite data.

  8. Different responses of Sea Surface Temperature in the North Pacific to greenhouse gas and aerosol forcing

    NASA Astrophysics Data System (ADS)

    Wang, Liyi; Liu, Qinyu

    2015-12-01

    The responses of Sea Surface Temperature (SST) to greenhouse gas (GHG) and anthropogenic aerosol in the North Pacific are compared based on the historical single and all-forcing simulations with Geophysical Fluid Dynamics Laboratory Climate Model version 3 (GFDL CM3). During 1860-2005, the effect of GHG forcing on the North Pacific SST is opposite to that of the aerosol forcing. Specifically, the aerosol cooling effect exceeds the GHG warming effect in the Kuroshio Extension (KE) region during 1950-2004 in the CM3 single forcing. The mid-latitude response of ocean circulation to the GHG (aerosol) forcing is to enhance (weaken) the Subtropical Gyre. Then the SST warming (cooling) lies on the zonal band of 40°N because of the increased (reduced) KE warm advection effect in the GHG (aerosol) forcing simulations, and the cooling effect to SST will surpass the warming effect in the KE region in the historical all-forcing simulations. Besides, the positive feedback between cold SST and cloud can also strengthen the aerosol cooling effect in the KE region during boreal summer, when the mixed layer depth is shallow. In the GHG (aerosol) forcing simulations, corresponding to warming (cooling) SST in the KE region, the weakened (enhanced) Aleutian Low appears in the Northeast Pacific. Consequently, the SST responses to all-forcing in the historical simulations are similar to the responses to aerosol forcing in sign and spatial pattern, hence the aerosol effect is quite important to the SST cooling in the mid-latitude North Pacific during the past 55 years.

  9. How Well Will MODIS Measure Top of Atmosphere Aerosol Direct Radiative Forcing?

    NASA Technical Reports Server (NTRS)

    Remer, Lorraine A.; Kaufman, Yoram J.; Levin, Zev; Ghan, Stephen; Einaudi, Franco (Technical Monitor)

    2000-01-01

    The new generation of satellite sensors such as the Moderate Resolution Imaging Spectroradiometer (MODIS) will be able to detect and characterize global aerosols with an unprecedented accuracy. The question remains whether this accuracy will be sufficient to narrow the uncertainties in our estimates of aerosol radiative forcing at the top of the atmosphere. Satellite remote sensing detects aerosol optical thickness with the least amount of relative error when aerosol loading is high. Satellites are less effective when aerosol loading is low. We use the monthly mean results of two global aerosol transport models to simulate the spatial distribution of smoke aerosol in the Southern Hemisphere during the tropical biomass burning season. This spatial distribution allows us to determine that 87-94% of the smoke aerosol forcing at the top of the atmosphere occurs in grid squares with sufficient signal to noise ratio to be detectable from space. The uncertainty of quantifying the smoke aerosol forcing in the Southern Hemisphere depends on the uncertainty introduced by errors in estimating the background aerosol, errors resulting from uncertainties in surface properties and errors resulting from uncertainties in assumptions of aerosol properties. These three errors combine to give overall uncertainties of 1.5 to 2.2 Wm-2 (21-56%) in determining the Southern Hemisphere smoke aerosol forcing at the top of the atmosphere. The range of values depend on which estimate of MODIS retrieval uncertainty is used, either the theoretical calculation (upper bound) or the empirical estimate (lower bound). Strategies that use the satellite data to derive flux directly or use the data in conjunction with ground-based remote sensing and aerosol transport models can reduce these uncertainties.

  10. Asian Monsoon Changes and the Role of Aerosol and Greenhouse Gas Forcing

    NASA Astrophysics Data System (ADS)

    Ting, M.; Li, X.

    2015-12-01

    Changes in Asian summer (June to August) monsoon in response to aerosol and greenhouse gas forcing are examined using observations and the Coupled Model Intercomparison Project - Phase 5 (CMIP5) multi-model, multi-realization ensemble. Results show that during the historical period, CMIP5 models show a predominantly drying trend in Asian monsoon, while in the 21st Century under representative concentration pathway 8.5 (rcp8.5) scenario, monsoon rainfall enhances across the entire Asian domain. The thermodynamic and dynamic mechanisms causing the changes are evaluated using the moisture budget analysis. The drying trend in the CMIP5 historical simulations and the wetting trend in the rcp8.5 projections can be explained by the relative importance of dynamical and thermodynamical contributions to the total moisture convergence. While thermodynamic mechanism dominates in the future, the historical rainfall changes are dominated by the changes in circulation. The relative contributions of aerosols and greenhouse gases (GHGs) on the historical monsoon change are further examined using CMIP5 single-forcing simulations. Rainfall reduces under aerosol forcing and increases under greenhouse gas (GHG) forcing. Aerosol forcing dominates over the greenhouse effect during the historical period, leading to the general drying trend in the all-forcing simulations. While the thermodynamic change of mean moisture convergence in the all-forcing case is dominated by the GHG forcing, the dynamic change in mean moisture convergence in the all-forcing case is dominated by the aerosol forcing. Further analysis using atmospheric GCM with prescribed aerosol and GHG radiative forcing versus those with the prescribed sea surface temperature (SST) warming suggests that the weak circulation changes due to GHG forcing is a result of the cancellation between CO2 radiative forcing and the SST warming, while aerosol radiative effect tends to enhance the circulation response due to SST forcing.

  11. Aerosols: Non-CO2 Non-Greenhouse Non-Gas Forcing

    NASA Astrophysics Data System (ADS)

    Schwartz, S. E.

    2005-05-01

    Tropospheric aerosols influence Earth's radiation budget and climate by scattering and absorbing solar radiation (direct effects) and by modifying the reflectivity and extent of clouds (indirect effects). While aerosol forcing is arguably less important from a policy perspective than greenhouse gas forcing because of the short residence times of these aerosols (about a week) compared to the lifetimes of the well mixed greenhouse gases (decades to centuries), knowledge of aerosol forcing over the industrial period is essential to empirical inference of Earth's climate sensitivity from temperature change over this period and to evaluation of the performance of climate model simulations over this period. Accuracy in global-average forcing by anthropogenic aerosols required for these purposes is estimated to be ~0.5 w m-2 [Schwartz, J. Air Waste Management Assoc. 54, 1351-1359 (2004)]. For an accumulation-mode (radius 50-1000 nm) scattering aerosol above a dark surface the forcing per optical depth (at 550 nm) during daylight hours for cloud-free sky is 50 to 100 W m-2. Such a forcing intensity implies, taking into account 50% nighttime and ~50% cloud cover, that global average optical depth of anthropogenic aerosol must be known to 0.02 - 0.04, an accuracy achievable by careful ground-based measurements, but which would be difficult to achieve globally because of high spatial and temporal variation. Top-of-atmosphere forcing for a given optical depth is sensitive also to single scattering albedo, size distribution (as manifested in asymmetry parameter, backscatter fraction, or Angstrom exponent) and surface reflectance; these sensitivities are examined here. It is necessary as well to determine the fraction of forcing that is due to anthropogenic aerosol. Similar considerations apply to aerosol indirect forcing, which depends to first approximation on the number concentration of cloud condensation nuclei as a function of applied supersaturation, which depends on the

  12. Modeling South America regional smoke plume: aerosol optical depth variability and shortwave surface forcing

    NASA Astrophysics Data System (ADS)

    Rosário, N. E.; Longo, K. M.; Freitas, S. R.; Yamasoe, M. A.; Fonseca, R. M.

    2012-07-01

    Amazon Basin produced a radiative forcing efficiency (RFE) of -158 W m-2/AOD550 nm at noon. This value is in between -154 W m-2/AOD550 nm and -187 W m-2/AOD550 nm, the range obtained when spatial varying optical models were considered. The average 24 h surface forcing over the biomass burning season varied from -55 W m-2 close to smoke sources in the southern part of the Amazon Basin and cerrado to -10 W m-2 in remote regions of the Southeast Brazilian coast.

  13. Response of North Pacific eastern subtropical mode water to greenhouse gas versus aerosol forcing

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Luo, Yiyong

    2016-04-01

    Mode water is a distinct water mass characterized by a near vertical homogeneous layer or low potential vorticity, and is considered essential for understanding ocean climate variability. Based on the output of GFDL CM3, this study investigates the response of eastern subtropical mode water (ESTMW) in the North Pacific to two different single forcings: greenhouse gases (GHGs) and aerosol. Under GHG forcing, ESTMW is produced on lighter isopycnal surfaces and is decreased in volume. Under aerosol forcing, in sharp contrast, it is produced on denser isopycnal surfaces and is increased in volume. The main reason for the opposite response is because surface ocean-to-atmosphere latent heat flux change over the ESTMW formation region shoals the mixed layer and thus weakens the lateral induction under GHG forcing, but deepens the mixed layer and thus strengthens the lateral induction under aerosol forcing. In addition, local wind changes are also favorable to the opposite response of ESTMW production to GHG versus aerosol.

  14. Global Distribution and Climate Forcing of Marine Organic Aerosol - Part 2: Effects on Cloud Properties and Radiative Forcing

    SciTech Connect

    Gantt, Brett; Xu, Jun; Meskhidze, N.; Zhang, Yang; Nenes, Athanasios; Ghan, Steven J.; Liu, Xiaohong; Easter, Richard C.; Zaveri, Rahul A.

    2012-07-25

    A series of simulations with the Community Atmosphere Model version 5 (CAM5) with a 7-mode Modal Aerosol Model were conducted to assess the changes in cloud microphysical properties and radiative forcing resulting from marine organic aerosols. Model simulations show that the anthropogenic aerosol indirect forcing (AIF) predicted by CAM5 is decreased in absolute magnitude by up to 0.09 Wm{sup -2} (7 %) when marine organic aerosols are included. Changes in the AIF from marine organic aerosols are associated with small global increases in low-level incloud droplet number concentration and liquid water path of 1.3 cm{sup -3} (1.5 %) and 0.22 gm{sup -2} (0.5 %), respectively. Areas especially sensitive to changes in cloud properties due to marine organic aerosol include the Southern Ocean, North Pacific Ocean, and North Atlantic Ocean, all of which are characterized by high marine organic emission rates. As climate models are particularly sensitive to the background aerosol concentration, this small but non-negligible change in the AIF due to marine organic aerosols provides a notable link for ocean-ecosystem marine low-level cloud interactions and may be a candidate for consideration in future earth system models.

  15. Characteristics of Carbonaceous and Ionic Species and Direct Aerosol Forcing of the Aerosols over Gosan, Jeju, Korea

    NASA Astrophysics Data System (ADS)

    Kim, N.; Kim, Y.; Kang, C.

    2010-12-01

    Carbonaceous aerosols, consisting of elemental carbon (EC) are emitted into the atmosphere through incomplete combustion of biomass and fossil fuel. It directly warms the air by absorbing solar radiation. Another major pollutant emitted by fossil fuel combustion is SO2, which result in the formation of particulate sulfate (SO42-) compounds, contribute substantially to cool the air by scattering solar radiation. Therefore, carbonaceous and sulfate aerosols play an important role in regulating the amount of solar radiation absorbed by the earth atmosphere. (Charlson et al. 1992; Jacobson, 2004; Khan et al., 2010) Carbonaceous and sulfate aerosols are both temporally and spatially variable. Northeast Asia is characterized by high energy consumption. China, Japan, and South Korea have consumed 16.8%, 4.7%, and 2.1% of the world total primary energy, respectively in 2007 (BP, 2008). Consequently, there are resultant huge emissions of anthropogenic air pollutants. Therefore, the effect on climate forcing by carbonaceous and sulfate aerosols are even more important in this region. In this study, PM2.5 intensive measurement data for 18 separate periods at Gosan, Jeju, Korea from 1994 to 2006 were analyzed. Gosan is one of the cleanest areas in Korea and an excellent location to study the ambient aerosols in Northeast Asia (Kim et al., 2009). The characteristics of carbonaceous aerosols and anthropogenic ions such as SO42-, NO3-, NH4+ were analyzed. Also, direct aerosol forcing due to EC and SO42- were calculated. The net aerosol forcing were about -0.5 W m-2 to -0.1 W m-2 at Gosan. References BP, www.bp.com/statisticalreview, 2008. Charlson, R.J., Schwartz, S.E., Hales, J.M., Cess, R.D., Coakley, J.A.Jr., Hansen, J.E., and Hofmann, D.J. (1992) Climate Forcing by Anthropogenic Aerosols, Science, 255, 423-430. Jacobson, M.Z. (2004) Climate response of fossil fuel and biofuel soot, accounting for soot's feedback to snow and sea ice albedo and emissivity, Journal of

  16. Possible Influence of Anthropogenic Aerosols on Cirrus Clouds and Anthropogenic Forcing

    SciTech Connect

    Penner, Joyce E.; Chen, Yang; Wang, Minghuai; Liu, Xiaohong

    2009-02-03

    Cirrus clouds have a net warming effect on the atmosphere and cover about 30% of the Earth’s area. Aerosol particles initiate ice formation in the upper troposphere through modes of action that include homogeneous freezing of solution droplets, heterogeneous nucleation on solid particles immersed in a solution, and deposition nucleation of vapor onto solid particles. Here, we examine the possible change in ice number concentration from anthropogenic soot originating from surface sources of fossil fuel and biomass burning, from anthropogenic sulfate aerosols, and from aircraft that deposit their aerosols directly in the upper troposphere. We find that fossil fuel and biomass burning soot aerosols exert a radiative forcing of -0.68 to 0.01 Wm-2 while anthropogenic sulfate aerosols exert a forcing of -0.01 to 0.18 Wm-2. Our calculations show that the sign of the forcing by aircraft soot depends on the model configuration and can be both positive or negative, ranging from -0.16 to 0.02 Wm-2. The magnitude of the forcing in cirrus clouds can be comparable to the forcing exerted by anthropogenic aerosols on warm clouds, but this forcing has not been included in past assessments of the total anthropogenic radiative forcing of climate.

  17. Global Impacts of Gas-Phase Chemistry-Aerosol Interactions on Direct Radiative Forcing by Anthropogenic Aerosols and Ozone

    NASA Technical Reports Server (NTRS)

    Liao, Hong; Seinfeld, John H.

    2005-01-01

    We present here a first global modeling study on the influence of gas-phase chemistry/aerosol interactions on estimates of anthropogenic forcing by tropospheric O3 and aerosols. Concentrations of gas-phase species and sulfate, nitrate, ammonium, black carbon, primary organic carbon, secondary organic carbon, sea salt, and mineral dust aerosols in the preindustrial, present-day, and year 2100 (IPCC SRES A2) atmospheres are simulated online in the Goddard Institute for Space Studies general circulation model II' (GISS GCM II'). With fully coupled chemistry and aerosols, the preindustrial, presentday, and year 2100 global burdens of tropospheric ozone are predicted to be 190, 319, and 519 Tg, respectively. The burdens of sulfate, nitrate, black carbon, and organic carbon are predicted respectively to be 0.32. 0.18, 0.01, 0.33 Tg in preindustrial time, 1.40, 0.48, 0.23, 1.60 Tg in presentday, and 1.37, 1.97, 0.54, 3.31 Tg in year 2100. Anthropogenic O3 is predicted to have a globally and annually averaged present-day forcing of +0.22 W m(sup -2) and year 2100 forcing of +0.57 W m(sup -2) at the top of the atmosphere (TOA). Net anthropogenic TOA forcing by internally mixed sulfate, nitrate, organic carbon, and black carbon aerosols is estimated to be virtually zero in the present-day and +0.34 W m(sup -2) in year 2100, whereas it is predicted to be -0.39 W m(sup -2) in present-day and -0.61 W m(sup -2) in year 2100 if the aerosols are externally mixed. Heterogeneous reactions are shown to be important in affecting anthropogenic forcing. When reactions of N2O5, NO3, NO2, and HO2 on aerosols are accounted for, TOA anthropogenic O3 forcing is less by 20-45% in present-day and by 20-32% in year 2100 at mid to high latitudes in the Northern Hemisphere, as compared with values predicted in the absence of heterogeneous gas aerosol reactions. Mineral dust uptake of HNO3 and O3 is shown to have practically no influence on anthropogenic O3 forcing. Heterogeneous reactions of N2Os

  18. Mixing state of aerosols over the Indo-Gangetic Plain: Radiative forcing and heating rate

    NASA Astrophysics Data System (ADS)

    Srivastava, R.; Ramachandran, S.

    2012-12-01

    Aerosols are a major atmospheric variable which perturb the Earth-atmosphere radiation balance by absorbing and scattering the solar and terrestrial radiation. Aerosols are produced by natural and anthropogenic processes. The presence of different types of aerosol over a location and aerosols transported from long-range can give rise to different mixing states because of aging and interaction among the different aerosol species. Knowledge of the mixing state of aerosols is important for an accurate assessment of aerosols in climate forcing, as assumptions regarding the mixing state of aerosol and its effect on optical properties can give rise to uncertainties in modeling their direct and indirect effects [1]. Seasonal variations in mixing states of aerosols over an urban (Kanpur) and a rural location (Gandhi College) in the Indo-Gangetic Plain (IGP) are determined using the measured and modeled aerosol optical properties, and the impact of aerosol mixing state on aerosol radiative forcing are investigated. IGP is one of the most populated and polluted river basins in the world, rich in fertile lands and agricultural production. Kanpur is an urban, industrial and densely populated city, and has several large/small scale industries and vehicles, while Gandhi College in IGP is a rural village, located southeast of Kanpur. Aerosol optical properties obtained from Aerosol Robotic Network sun/sky radiometers [2] over these two environmentally distinct locations in Indo-Gangetic Plain are used in the study, along with aerosol vertical profiles obtained from CALIPSO (Cloud- Aerosol Lidar and Infrared Pathfinder Satellite Observations) lidar observations. Probable mixing state of aerosols is determined utilizing the aerosol optical properties viz., aerosol optical depth, single scattering albedo and asymmetry parameter. The coated-sphere Mie calculation requires the refractive index of core and shell species, and the radius of core and shell particles. Core to shell radius

  19. Multidecadal solar radiation trends in the United States and Germany and direct tropospheric aerosol forcing

    NASA Astrophysics Data System (ADS)

    Liepert, Beate; Tegen, Ina

    2002-06-01

    In recent studies, anthropogenic aerosols have been recognized as important radiative forcing factors of climate because of their ability to scatter and/or absorb sunlight. At clear-sky conditions the direct aerosol forcing at ground is negative and implies less solar heating of the surface because of aerosols. In this study, an intensified direct aerosol forcing of -7 to -8 W/m2 has been detected in the United States for the interval from 1960 to 1990. In Germany a weakened aerosol forcing of +3 W/m2 was observed during the same time period. Even though the aerosol forcing is stronger in the eastern United States compared to the western United States, the positive trend is almost equal. We attained these results by scrutinizing clear-sky global solar radiation recordings for these regions and this time period. Additionally, the diurnal cycle and the direct to diffuse ratio of solar radiation were used for constraining the observed trends. Increased absorption and declined light scattering are presumably responsible for the intensified direct aerosol forcing in the United States. While at the same time in Germany, both aerosol absorption and scattering must have declined to explain the parallel weakened aerosol forcing and the increased direct/diffuse ratio. To estimate the possible anthropogenic portion of these observed changes, we compared the observational results with modeled aerosol forcing scenarios retrieved from the Goddard Institute for Space Studies general circulation model (GISS GCM). Modeled surface solar radiation, aerosol optical thickness, and single-scattering albedo are derived from emission trends of anthropogenic sulfate and carbonaceous aerosols. The emission distributions are calculated from fossil fuel consumption databases. On the basis of these simulations we suspect that the declining trend of sulfate burden over Germany between 1960 and 1990 was stronger than estimated with the model. Over the United States the simulated small increase

  20. Stratospheric aerosol forcing for climate modeling: 1850-1978

    NASA Astrophysics Data System (ADS)

    Arfeuille, Florian; Luo, Beiping; Thomason, Larry; Vernier, Jean-Paul; Peter, Thomas

    2016-04-01

    We present here a stratospheric aerosol dataset produced using the available aerosol optical depth observations from the pre-satellite period. The scarce atmospheric observations are supplemented by additional information from an aerosol microphysical model, initialized by ice-core derived sulfur emissions. The model is used to derive extinctions at all altitudes, latitudes and times when sulfur injections are known for specific volcanic eruptions. The simulated extinction coefficients are then scaled to match the observed optical depths. In order to produce the complete optical properties at all wavelengths (and the aerosol surface area and volume densities) needed by climate models, we assume a lognormal size distribution of the aerosols. Correlations between the extinctions in the visible and the effective radius and distribution width parameters are taken from the better constrained SAGE II period. The aerosol number densities are then fitted to match the derived extinctions in the 1850-1978 period. From these aerosol size distributions, we then calculate extinction coefficients, single scattering albedos and asymmetry factors at all wavelengths using the Mie theory. The aerosol surface area densities and volume densities are also provided.

  1. Satellite Estimates of the Direct Radiative Forcing of Biomass Burning Aerosols Over South America and Africa

    NASA Technical Reports Server (NTRS)

    Christopher, Sundar A.; Wang, Min; Kliche, Donna V.; Berendes, Todd; Welch, Ronald M.; Yang, S.K.

    1997-01-01

    Atmospheric aerosol particles, both natural and anthropogenic are important to the earth's radiative balance. Therefore it is important to provide adequate validation information on the spatial, temporal and radiative properties of aerosols. This will enable us to predict realistic global estimates of aerosol radiative effects more confidently. The current study utilizes 66 AVHRR LAC (Local Area Coverage) and coincident Earth Radiation Budget Experiment (ERBE) images to characterize the fires, smoke and radiative forcings of biomass burning aerosols over four major ecosystems of South America.

  2. Aerosol size distribution and radiative forcing response to anthropogenically driven historical changes in biogenic secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    D'Andrea, S. D.; Acosta Navarro, J. C.; Farina, S. C.; Scott, C. E.; Rap, A.; Farmer, D. K.; Spracklen, D. V.; Riipinen, I.; Pierce, J. R.

    2015-03-01

    Emissions of biogenic volatile organic compounds (BVOCs) have changed in the past millennium due to changes in land use, temperature, and CO2 concentrations. Recent reconstructions of BVOC emissions have predicted that global isoprene emissions have decreased, while monoterpene and sesquiterpene emissions have increased; however, all three show regional variability due to competition between the various influencing factors. In this work, we use two modeled estimates of BVOC emissions from the years 1000 to 2000 to test the effect of anthropogenic changes to BVOC emissions on secondary organic aerosol (SOA) formation, global aerosol size distributions, and radiative effects using the GEOS-Chem-TOMAS (Goddard Earth Observing System; TwO-Moment Aerosol Sectional) global aerosol microphysics model. With anthropogenic emissions (e.g., SO2, NOx, primary aerosols) turned off and BVOC emissions changed from year 1000 to year 2000 values, decreases in the number concentration of particles of size Dp > 80 nm (N80) of > 25% in year 2000 relative to year 1000 were predicted in regions with extensive land-use changes since year 1000 which led to regional increases in the combined aerosol radiative effect (direct and indirect) of > 0.5 W m-2 in these regions. We test the sensitivity of our results to BVOC emissions inventory, SOA yields, and the presence of anthropogenic emissions; however, the qualitative response of the model to historic BVOC changes remains the same in all cases. Accounting for these uncertainties, we estimate millennial changes in BVOC emissions cause a global mean direct effect of between +0.022 and +0.163 W m-2 and the global mean cloud-albedo aerosol indirect effect of between -0.008 and -0.056 W m-2. This change in aerosols, and the associated radiative forcing, could be a largely overlooked and important anthropogenic aerosol effect on regional climates.

  3. Toward a Minimal Representation of Aerosols in Climate Models: Comparative Decomposition of Aerosol Direct, Semidirect, and Indirect Radiative Forcing

    SciTech Connect

    Ghan, Steven J.; Liu, Xiaohong; Easter, Richard C.; Zaveri, Rahul A.; Rasch, Philip J.; Yoon, Jin-Ho; Eaton, Brian

    2012-10-01

    The authors have decomposed the anthropogenic aerosol radiative forcing into direct contributions from each aerosol species to the planetary energy balance through absorption and scattering of solar radiation, indirect effects of anthropogenic aerosol on solar and infrared radiation through droplet and crystal nucleation on aerosol, and semidirect effects through the influence of solar absorption on the distribution of clouds. A three-mode representation of the aerosol in version 5.1 of the Community Atmosphere Model (CAM5.1) yields global annual mean radiative forcing estimates for each of these forcing mechanisms that are within 0.1 W m–2 of estimates using a more complex seven-mode representation that distinguishes between fresh and aged black carbon and primary organic matter. Simulating fresh black carbon particles separately from internally mixed accumulation mode particles is found to be important only near fossil fuel sources. In addition to the usual large indirect effect on solar radiation, this study finds an unexpectedly large positive longwave indirect effect (because of enhanced cirrus produced by homogenous nucleation of ice crystals on anthropogenic sulfate), small shortwave and longwave semidirect effects, and a small direct effect (because of cancelation and interactions of direct effects of black carbon and sulfate). Differences between the threemode and seven-mode versions are significantly larger (up to 0.2 W m–2) when the hygroscopicity of primary organic matter is decreased from 0.1 to 0 and transfer of the primary carbonaceous aerosol to the accumulation mode in the seven-mode version requires more hygroscopic material coating the primary particles. Radiative forcing by cloudborne anthropogenic black carbon is only 20.07 W m–2.

  4. Reducing the Uncertainties in Direct Aerosol Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Kahn, Ralph A.

    2011-01-01

    Airborne particles, which include desert and soil dust, wildfire smoke, sea salt, volcanic ash, black carbon, natural and anthropogenic sulfate, nitrate, and organic aerosol, affect Earth's climate, in part by reflecting and absorbing sunlight. This paper reviews current status, and evaluates future prospects for reducing the uncertainty aerosols contribute to the energy budget of Earth, which at present represents a leading factor limiting the quality of climate predictions. Information from satellites is critical for this work, because they provide frequent, global coverage of the diverse and variable atmospheric aerosol load. Both aerosol amount and type must be determined. Satellites are very close to measuring aerosol amount at the level-of-accuracy needed, but aerosol type, especially how bright the airborne particles are, cannot be constrained adequately by current techniques. However, satellite instruments can map out aerosol air mass type, which is a qualitative classification rather than a quantitative measurement, and targeted suborbital measurements can provide the required particle property detail. So combining satellite and suborbital measurements, and then using this combination to constrain climate models, will produce a major advance in climate prediction.

  5. Simulating contemporary and preindustrial atmospheric chemistry and aerosol radiative forcing in the Southeast Pacific (Invited)

    NASA Astrophysics Data System (ADS)

    Spak, S.; Mena-Carrasco, M.; Carmichael, G. R.

    2010-12-01

    Accurately quantifying the aerosol burden and resultant radiative impacts over the Southeast Pacific presents a critical challenge in constraining the region's upper ocean heat budget and sea surface temperatures. Recent observations and preliminary modeling studies have found consistent aerosol transport above the region's extensive stratoculumus, indicating the need to consider aerosol composition and direct radiative effects in addition to indirect effects on clouds. We simulate regional chemical transport of aerosols and trace gases during VOCALS REx, identifying contributions from coastal anthropogenic emissions, biogenic emissions, biomass burning, and long-range transport to aerosol mass and composition. We evaluate a new emissions inventory through comparison with in-situ observations. Spatial and temporal variability in transport from these varied emissions sources provide insights into land-ocean-atmosphere coupling. We will compare aerosol radiative forcing under present day and preindustrial emissions rates.

  6. Aerosol single scattering albedo and its contribution to radiative forcing dung EAST- AIRE

    NASA Astrophysics Data System (ADS)

    Lee, K.; Li, Z.

    2007-12-01

    Quantification of aerosol single scattering albedo (SSA) can improve determining aerosol radiative property. Combination technique using MODIS and ground-based Hazemeter measurement data by the East Asian Study of Tropospheric Aerosols: an International Regional Experiment (EAST-AIRE) over China is proposed to retrieve SSA. The accuracy of the retrieval of SSA increases with the aerosol loading and the uncertainties in the SSA retrieval are 0.02~0.03 (AOT=1.0) and up to 0.03~0.05 (AOT=0.5) at 0.47¥ìm, respectively. The comparison of one- year data of retrieved SSA values with those from AERONET inversion product are ~0.03 (RMSD) and ~0.02 (mean bias), respectively. Estimated SSA values were range from 0.89 to 0.93 over the study area. Since SSA is an important factor of aerosol radiative forcing, these will help to understood the study of aerosol climate effects.

  7. Simulation of aerosol direct radiative forcing with RAMS-CMAQ in East Asia

    NASA Astrophysics Data System (ADS)

    Zhang, M.; Han, X.; Liu, X.

    2011-12-01

    The air quality modeling system RAMS-CMAQ is developed to assess aerosol direct radiative forcing by linking simulated meteorological parameters and aerosol mass concentration with the aerosol optical properties/radiative transfer module in this study. The module is capable of accounting for important factors that affect aerosol optical properties and radiative effect, such as incident wave length, aerosol size distribution, water uptake, and internal mixture. Subsequently, the modeling system is applied to simulate the temporal and spatial variations in mass burden, optical properties, and direct radiative forcing of diverse aerosols, including sulfate, nitrate, ammonium, black carbon, organic carbon, dust, and sea salt over East Asia throughout 2005. Model performance is fully evaluated using various observational data, including satellite monitoring of MODIS and surface measurements of EANET (Acid Deposition Monitoring Network), AERONET (Aerosol Robotic Network), and CSHNET (Chinese Sun Hazemeter Network). The correlation coefficients of the comparisons of daily average mass concentrations of sulfate, PM2.5, and PM10 between simulations and EANET measurements are 0.70, 0.61, and 0.64, respectively. It is also determined that the modeled aerosol optical depth (AOD) is in congruence with the observed results from the AERONET, the CSHNET, and the MODIS. The model results suggest that the high AOD values ranging from 0.8 to 1.2 are mainly distributed over the Sichuan Basin as well as over central and southeastern China, in East Asia. The aerosol direct radiative forcing patterns generally followed the AOD patterns. The strongest forcing effect ranging from -12 to -8 W/m2 was mainly distributed over the Sichuan Basin and the eastern China's coastal regions in the all-sky case at TOA, and the forcing effect ranging from -8 to -4 W/m2 could be found over entire eastern China, Korea, Japan, East China Sea, and the sea areas of Japan.

  8. Simulation of aerosol direct radiative forcing with RAMS-CMAQ in East Asia

    NASA Astrophysics Data System (ADS)

    Han, Xiao; Zhang, Meigen; Han, Zhiwei; Xin, Jinyuan; Liu, Xiaohong

    2011-11-01

    The air quality modeling system RAMS-CMAQ is developed to assess aerosol direct radiative forcing by linking simulated meteorological parameters and aerosol mass concentration with the aerosol optical properties/radiative transfer module in this study. The module is capable of accounting for important factors that affect aerosol optical properties and radiative effect, such as incident wave length, aerosol size distribution, water uptake, and internal mixture. Subsequently, the modeling system is applied to simulate the temporal and spatial variations in mass burden, optical properties, and direct radiative forcing of diverse aerosols, including sulfate, nitrate, ammonium, black carbon, organic carbon, dust, and sea salt over East Asia throughout 2005. Model performance is fully evaluated using various observational data, including satellite monitoring of MODIS and surface measurements of EANET (Acid Deposition Monitoring Network), AERONET (Aerosol Robotic Network), and CSHNET (Chinese Sun Hazemeter Network). The correlation coefficients of the comparisons of daily average mass concentrations of sulfate, PM2.5, and PM10 between simulations and EANET measurements are 0.70, 0.61, and 0.64, respectively. It is also determined that the modeled aerosol optical depth (AOD) is in congruence with the observed results from the AERONET, the CSHNET, and the MODIS. The model results suggest that the high AOD values ranging from 0.8 to 1.2 are mainly distributed over the Sichuan Basin as well as over central and southeastern China, in East Asia. The aerosol direct radiative forcing patterns generally followed the AOD patterns. The strongest forcing effect ranging from -12 to -8 W m -2 was mainly distributed over the Sichuan Basin and the eastern China's coastal regions in the all-sky case at TOA, and the forcing effect ranging from -8 to -4 W m -2 could be found over entire eastern China, Korea, Japan, East China Sea, and the sea areas of Japan

  9. Simulation of aerosol direct radiative forcing with RAMS-CMAQ in East Asia

    SciTech Connect

    Han, Xiao; Zhang, Meigen; Han, Zhiewi; Xin, Jin-Yuan; Liu, Xiaohong

    2011-11-14

    The air quality modeling system RAMS-CMAQ is developed to assess aerosol direct radiative forcing by linking simulated meteorological parameters and aerosol mass concentration with the aerosol optical properties/radiative transfer module in this study. The module is capable of accounting for important factors that affect aerosol optical properties and radiative effect, such as incident wave length, aerosol size distribution, water uptake, and internal mixture. Subsequently, the modeling system is applied to simulate the temporal and spatial variations in mass burden, optical properties, and direct radiative forcing of diverse aerosols, including sulfate, nitrate, ammonium, black carbon, organic carbon, dust, and sea salt over East Asia throughout 2005. Model performance is fully evaluated using various observational data, including satellite monitoring of MODIS and surface measurements of EANET (Acid Deposition Monitoring Network), AERONET (Aerosol Robotic Network), and CSHNET (Chinese Sun Hazemeter Network). The correlation coefficients of the comparisons of daily average mass concentrations of sulfate, PM2.5, and PM10 between simulations and EANET measurements are 0.70, 0.61, and 0.64, respectively. It is also determined that the modeled aerosol optical depth (AOD) is in congruence with the observed results from the AERONET, the CSHNET, and the MODIS. The model results suggest that the high AOD values ranging from 0.8 to 1.2 are mainly distributed over the Sichuan Basin as well as over central and southeastern China, in East Asia. The aerosol direct radiative forcing patterns generally followed the AOD patterns. The strongest forcing effect ranging from -12 to -8 W m-2 was mainly distributed over the Sichuan Basin and the eastern China's coastal regions in the all-sky case at TOA, and the forcing effect ranging from -8 to -4 W m-2 could be found over entire eastern China, Korea, Japan, East China Sea, and the sea areas of Japan

  10. Large differences in tropical aerosol forcing at the top of the atmosphere and Earth's surface

    PubMed

    Satheesh; Ramanathan

    2000-05-01

    The effect of radiative forcing by anthropogenic aerosols is one of the largest sources of uncertainty in climate predictions. Direct observations of the forcing are therefore needed, particularly for the poorly understood tropical aerosols. Here we present an observational method for quantifying aerosol forcing to within +/-5 per cent. We use calibrated satellite radiation measurements and five independent surface radiometers to quantify the aerosol forcing simultaneously at the Earth's surface and the top of the atmosphere over the tropical northern Indian Ocean. In winter, this region is covered by anthropogenic aerosols of sulphate, nitrate, organics, soot and fly ash from the south Asian continent. Accordingly, mean clear-sky solar radiative heating for the winters of 1998 and 1999 decreased at the ocean surface by 12 to 30 Wm(-2), but only by 4 to 10 Wm(-2) at the top of the atmosphere. This threefold difference (due largely to solar absorption by soot) and the large magnitude of the observed surface forcing both imply that tropical aerosols might slow down the hydrological cycle.

  11. Experimental studies of silver iodide pyrotechnic aerosol ice forming efficiency dynamics

    NASA Astrophysics Data System (ADS)

    Shilin, A. G.; Drofa, A. S.; Ivanov, V. N.; Savchenko, A. V.; Shilin, V. A.

    2013-05-01

    The study concerns the problems connected with the temporal variability of aerosol ice forming activity at introduction into the sub-cloud layer and the comparison of aerosol efficiency of produced pyrotechnic mixtures with different silver contents.

  12. Optical properties and radiative forcing of urban aerosols in Nanjing, China

    NASA Astrophysics Data System (ADS)

    Zhuang, B. L.; Wang, T. J.; Li, S.; Liu, J.; Talbot, R.; Mao, H. T.; Yang, X. Q.; Fu, C. B.; Yin, C. Q.; Zhu, J. L.; Che, H. Z.; Zhang, X. Y.

    2014-02-01

    Continuous measurements of atmospheric aerosols were made in Nanjing, a megacity in China, from 18 January to 18 April, 2011 (Phase 1) and from 22 April 2011 to 21 April 2012 (Phase 2). Aerosol characteristics, optical properties, and direct radiative forcing (DRF) were studied through interpretations of these measurements. We found that during Phase 1, mean PM2.5, black carbon (BC), and aerosol scattering coefficient (Bsp) in Nanjing were 76.1 ± 59.3 μg m-3, 4.1 ± 2.2 μg m-3, and 170.9 ± 105.8 M m-1, respectively. High pollution episodes occurred during Spring and Lantern Festivals when hourly PM2.5 concentrations reached 440 μg m-3, possibly due to significant discharge of fireworks. Temporal variations of PM2.5, BC, and Bsp were similar to each other. It is estimated that inorganic scattering aerosols account for about 49 ± 8.6% of total aerosols while BC only accounted for 6.6 ± 2.9%, and nitrate was larger than sulfate. In Phase 2, optical properties of aerosols show great seasonality. High relative humidity (RH) in summer (June, July, August) likely attributed to large optical depth (AOD) and small Angstrom exponent (AE) of aerosols. Due to dust storms, AE of total aerosols was the smallest in spring (March, April, May). Annual mean 550-nm AOD and 675/440-nm AE were 0.6 ± 0.3 and 1.25 ± 0.29 for total aerosols, 0.04 ± 0.02 and 1.44 ± 0.50 for absorbing aerosols, 0.48 ± 0.29 and 1.64 ± 0.29 for fine aerosols, respectively. Annual single scattering albedo of aerosols ranged from 0.90 to 0.92. Real time wavelength-dependent surface albedo from the Moderate Resolution Imaging Spectroradiometer (MODIS) was used to assess aerosol DRFs. Both total and absorbing aerosol DRFs had significant seasonal variations in Nanjing and they were the strongest in summer. Annual mean clear sky TOA DRF (including daytime and nighttime) of total and absorbing aerosols was about -6.9 and +4.5 W m-2, respectively. Aerosol DRFs were found to be sensitive to surface

  13. Estimating the Radiative Forcing of Carbonaceous Aerosols over California based on Satellite and Ground Observations

    SciTech Connect

    Xu, Yangyang; Bahadur, R.; Zhao, Chun; Leung, Lai-Yung R.

    2013-10-04

    Carbonaceous aerosols have the potential to impact climate both through directly absorbing incoming solar radiation, and by indirectly affecting the cloud layer. To quantify this impact recent modeling studies have made great efforts to simulate both the spatial and temporal distribution of carbonaceous aerosols and their associated radiative forcing. This study makes the first observationally constrained assessment of the direct radiative forcing of carbonaceous aerosols at a regional scale over California. By exploiting multiple observations (including ground sites and satellites), we constructed the distribution of aerosol optical depths and aerosol absorption optical depths over California for a ten-year period (2000-2010). The total solar absorption was then partitioned into contributions from elemental carbon (EC), organic carbon (OC) and dust aerosols using a newly developed scheme. Aerosol absorption optical depth due to carbonaceous aerosols (EC and OC) at 440 nm is 50%-200% larger than natural dust, with EC contributing the bulk (70%-90%). Observationally constrained EC absorption agrees reasonably well with estimates from regional transport models, but the model underestimates the OC AAOD by at least 50%. We estimate that the TOA warming from carbonaceous aerosols is 0.7 W/m2 and the TOA forcing due to OC is close to zero. The atmospheric heating of carbonaceous aerosols is 2.2-2.9 W/m2, of which EC contributed about 80-90%. The atmospheric heating due to OC is estimated to be 0.1 to 0.4 W/m2, larger than model simulations. The surface brightening due to EC reduction over the last two decades is estimated to be 1.5-3.5 W/m2.

  14. Evolution of ozone, particulates, and aerosol direct radiative forcing in the vicinity of Houston using a fully coupled meteorology-chemistry-aerosol model

    NASA Astrophysics Data System (ADS)

    Fast, Jerome D.; Gustafson, William I.; Easter, Richard C.; Zaveri, Rahul A.; Barnard, James C.; Chapman, Elaine G.; Grell, Georg A.; Peckham, Steven E.

    2006-11-01

    A new fully coupled meteorology-chemistry-aerosol model is used to simulate the urban- to regional-scale variations in trace gases, particulates, and aerosol direct radiative forcing in the vicinity of Houston over a 5 day summer period. Model performance is evaluated using a wide range of meteorological, chemistry, and particulate measurements obtained during the 2000 Texas Air Quality Study. The predicted trace gas and particulate distributions were qualitatively similar to the surface and aircraft measurements with considerable spatial variations resulting from urban, power plant, and industrial sources of primary pollutants. Sulfate, organic carbon, and other inorganics were the largest constituents of the predicted particulates. The predicted shortwave radiation was 30 to 40 W m-2 closer to the observations when the aerosol optical properties were incorporated into the shortwave radiation scheme; however, the predicted hourly aerosol radiative forcing was still underestimated by 10 to 50 W m-2. The predicted aerosol radiative forcing was larger over Houston and the industrial ship channel than over the rural areas, consistent with surface measurements. The differences between the observed and simulated aerosol radiative forcing resulted from transport errors, relative humidity errors in the upper convective boundary layer that affect aerosol water content, secondary organic aerosols that were not yet included in the model, and uncertainties in the primary particulate emission rates. The current model was run in a predictive mode and demonstrates the challenges of accurately simulating all of the meteorological, chemical, and aerosol parameters over urban to regional scales that can affect aerosol radiative forcing.

  15. Distinct Patterns of Climate Response to Anthropogenic Aerosol Versus Greenhouse Gas Forcing

    NASA Astrophysics Data System (ADS)

    WANG, H.; Xie, S. P.; Liu, Q.

    2015-12-01

    Patterns of climate response to anthropogenic aerosols and well-mixed greenhouse gas (GHG) changes are investigated using eight models from Phase 5 of the Coupled Model Intercomparison Project. In the 20th century, the principal climate response patterns show both similarities and differences between aerosol and GHG runs. This paper focuses on distinct patterns of climate response to aerosol and GHG changes, while a recent companion study discussed the similarities. The GHG induced radiative forcing gives rise to amplified warming in the tropical upper troposphere and intensified mid-latitude jets in both hemispheres. However, for the anthropogenic aerosols, they are concentrated in the Northern Hemisphere and the temperature change shows a deep cooling structure in the troposphere around 40°N. Consistent with thermal wind balance, the cooling anchors a westerly acceleration to its south in aerosol runs. The response to aerosol induced inter-hemispheric asymmetry is also interpreted in terms of an anomalous Hadley circulation across the equator. Careful comparison indicates that the aerosol forcing dominates the Northern Hemisphere response in atmospheric circulation and precipitation, including a southward shift of the Inter Tropical Convergence Zone, the drying trend over the East Asia monsoon region, the southward shift of the East Asia westerly jet and the North Pacific cooling. The GHG forcing dominates the tropical Pacific rainfall increase mediated by the sea surface temperature pattern. Several climate response pattern indices are evaluated for the relative importance of aerosol and GHG forcing. The aerosol induced inter-hemisphere thermal contrast plays a key role in inducing climate response patterns that are quite different from the results in GHG runs.

  16. Satellite-derived aerosol radiative forcing from the 2004 British Columbia wildfires

    USGS Publications Warehouse

    Guo, S.; Leighton, H.

    2008-01-01

    The British Columbia wildfires of 2004 was one of the largest wildfire events in the last ten years in Canada. Both the shortwave and longwave smoke aerosol radiative forcing at the top-of-atmosphere (TOA) are investigated using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Clouds and the Earth's Radiant Energy System (CERES) instruments. Relationships between the radiative forcing fluxes (??F) and wildfire aerosol optical thickness (AOT) at 0.55 ??m (??0.55) are deduced for both noontime instantaneous forcing and diurnally averaged forcing. The noontime averaged instantaneous shortwave and longwave smoke aerosol radiative forcing at the TOA are 45.8??27.5 W m-2 and -12.6??6.9 W m-2, respectively for a selected study area between 62??N and 68??N in latitude and 125??W and 145??W in longitude over three mainly clear-sky days (23-25 June). The derived diurnally averaged smoke aerosol shortwave radiative forcing is 19.9??12.1 W m-2 for a mean ??0.55 of 1.88??0.71 over the same time period. The derived ??F-?? relationship can be implemented in the radiation scheme used in regional climate models to assess the effect of wildfire aerosols.

  17. Uncertainty in the magnitude of aerosol-cloud radiative forcing over recent decades

    NASA Astrophysics Data System (ADS)

    Regayre, L. A.; Pringle, K. J.; Booth, B. B. B.; Lee, L. A.; Mann, G. W.; Browse, J.; Woodhouse, M. T.; Rap, A.; Reddington, C. L.; Carslaw, K. S.

    2014-12-01

    Aerosols and their effect on the radiative properties of clouds are one of the largest sources of uncertainty in calculations of the Earth's energy budget. Here the sensitivity of aerosol-cloud albedo effect forcing to 31 aerosol parameters is quantified. Sensitivities are compared over three periods; 1850-2008, 1978-2008, and 1998-2008. Despite declining global anthropogenic SO2 emissions during 1978-2008, a cancelation of regional positive and negative forcings leads to a near-zero global mean cloud albedo effect forcing. In contrast to existing negative estimates, our results suggest that the aerosol-cloud albedo effect was likely positive (0.006 to 0.028Wm-2) in the recent decade, making it harder to explain the temperature hiatus as a forced response. Proportional contributions to forcing variance from aerosol processes and natural and anthropogenic emissions are found to be period dependent. To better constrain forcing estimates, the processes that dominate uncertainty on the timescale of interest must be better understood.

  18. Wet removal of black carbon in Asian outflow: Aerosol Radiative Forcing in East Asia (A-FORCE) aircraft campaign

    NASA Astrophysics Data System (ADS)

    Oshima, N.; Kondo, Y.; Moteki, N.; Takegawa, N.; Koike, M.; Kita, K.; Matsui, H.; Kajino, M.; Nakamura, H.; Jung, J. S.; Kim, Y. J.

    2012-02-01

    The Aerosol Radiative Forcing in East Asia (A-FORCE) aircraft campaign was conducted over East Asia in March-April 2009. During the A-FORCE campaign, 120 vertical profiles of black carbon (BC) and carbon monoxide (CO) were obtained in the planetary boundary layer (PBL) and the free troposphere. This study examines the wet removal of BC in Asian outflow using the A-FORCE data. The concentrations of BC and CO were greatly enhanced in air parcels sampled at 3-6 km in altitude over the Yellow Sea on 30 March 2009, associated with upward transport due to a cyclone with modest amounts of precipitation over northern China. In contrast, high CO concentrations without substantial enhancements of BC concentrations were observed in air parcels sampled at 5-6 km over the East China Sea on 23 April 2009, caused by uplifting due to cumulus convection with large amounts of precipitation over central China. The transport efficiency of BC (TEBC, namely the fraction of BC particles not removed during transport) in air parcels sampled above 2 km during the entire A-FORCE period decreased primarily with the increase in the precipitation amount that air parcels experienced during vertical transport, although their correlation was modest (r2 = 0.43). TEBC also depended on the altitude to which air parcels were transported from the PBL and the latitude where they were uplifted locally over source regions. The median values of TEBC for air parcels originating from northern China (north of 33°N) and sampled at 2-4 km and 4-9 km levels were 86% and 49%, respectively, during the A-FORCE period. These median values were systematically greater than the corresponding median values (69% and 32%, respectively) for air parcels originating from southern China (south of 33°N). Use of the A-FORCE data set will contribute to the reduction of large uncertainties in wet removal process of BC in global- and regional-scale models.

  19. Aerosol direct radiative forcing in desert and semi-desert regions of northwestern China

    NASA Astrophysics Data System (ADS)

    Xin, Jinyuan; Gong, Chongshui; Wang, Shigong; Wang, Yuesi

    2016-05-01

    The optical properties of dust aerosols were measured using narrow-band data from a portable sun photometer at four desert and semi-desert stations in northwestern China from 2004 to 2007. Ground-based and satellite observations indicated absorbing dust aerosol loading over the region surrounded by eight large-scale deserts. Radiation forcing was identified by using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model. The ranges of annual mean aerosol optical depth (AOD), Angström exponents, and single-scattering albedo (SSA) were from 0.25 to 0.35, from - 0.73 to 1.18, and from 0.77 to 0.86, respectively. The ranges of annual mean aerosol direct radiative forcing values at the top of the atmosphere (TOA), mid-atmosphere, and on the surface were from 3.9 to 12.0, from 50.0 to 53.1, and from - 39.1 to - 48.1 W/m2, respectively. The aerosols' optical properties and radiative characteristics showed strong seasonal variations in both the desert and semi-desert regions. Strong winds and relatively low humidity will lead dust aerosols in the atmosphere to an increase, which played greatly affected these optical properties during spring and winter in northwestern China. Based on long-term observations and retrieved data, aerosol direct radiative forcing was confirmed to heat the atmosphere (50-53 W/m2) and cool the surface (- 39 to - 48 W/m2) above the analyzed desert. Radiative forcing in the atmosphere in spring and winter was 18 to 21 W/m2 higher than other two seasons. Based on the dust sources around the sites, the greater the AOD, the more negative the forcing. The annual averaged heating rates for aerosols close to the ground (1 km) were approximately 0.80-0.85 K/day.

  20. Evaluation of a size-resolved aerosol model based on satellite and ground observations and its implication on aerosol forcing

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoyan; Yu, Fangqun

    2016-04-01

    The latest AeroCom phase II experiments have showed a large diversity in the simulations of aerosol concentrations, size distribution, vertical profile, and optical properties among 16 detailed global aerosol microphysics models, which contribute to the large uncertainty in the predicted aerosol radiative forcing and possibly induce the distinct climate change in the future. In the last few years, we have developed and improved a global size-resolved aerosol model (Yu and Luo, 2009; Ma et al., 2012; Yu et al., 2012), GEOS-Chem-APM, which is a prognostic multi-type, multi-component, size-resolved aerosol microphysics model, including state-of-the-art nucleation schemes and condensation of low volatile secondary organic compounds from successive oxidation aging. The model is one of 16 global models for AeroCom phase II and participated in a couple of model inter-comparison experiments. In this study, we employed multi-year aerosol optical depth (AOD) data from 2004 to 2012 taken from ground-based Aerosol Robotic Network (AERONET) measurements and Moderate Resolution Imaging Spectroradiometer (MODIS), Multiangle Imaging SpectroRadiometer (MISR) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite retrievals to evaluate the performance of the GEOS-Chem-APM in predicting aerosol optical depth, including spatial distribution, reginal variation and seasonal variabilities. Compared to the observations, the modelled AOD is overall good over land, but quite low over ocean possibly due to low sea salt emission in the model and/or higher AOD in satellite retrievals, specifically MODIS and MISR. We chose 72 AERONET sites having at least 36 months data available and representative of high spatial domain to compare with the model and satellite data. Comparisons in various representative regions show that the model overall agrees well in the major anthropogenic emission regions, such as Europe, East Asia and North America. Relative to the observations, the modelled AOD is

  1. The Effect of Non-Lambertian Surface Reflectance on Aerosol Radiative Forcing

    SciTech Connect

    Ricchiazzi, P.; O'Hirok, W.; Gautier, C.

    2005-03-18

    Surface reflectance is an important factor in determining the strength of aerosol radiative forcing. Previous studies of radiative forcing assumed that the reflected surface radiance is isotropic and does not depend on incident illumination angle. This Lambertian reflection model is not a very good descriptor of reflectance from real land and ocean surfaces. In this study we present computational results for the seasonal average of short and long wave aerosol radiative forcing at the top of the atmosphere and at the surface. The effect of the Lambertian assumption is found through comparison with calculations using a more detailed bi-direction reflectance distribution function (BRDF).

  2. Atmospheric Teleconnection over Eurasia Induced by Aerosol Radiative Forcing During Boreal Spring

    NASA Technical Reports Server (NTRS)

    Kim, Maeng-Ki; Lau, K. M.; Chin, Mian; Kim, Kyu-Myong; Sud, Y. C.; Walker, Greg K.

    2005-01-01

    The direct effects of aerosols on global and regional climate during boreal spring are investigated based on simulations using the NASA Global Modeling and Assimilation Office (GMAO) finite-volume general circulation model (fvGCM) with Microphyics of clouds in Relaxed Arakawa Schubert Scheme (McRAS). The aerosol loading are prescribed from three-dimensional monthly distribution of tropospheric aerosols viz., sulfate, black carbon, organic carbon, soil dust, and sea salt from output of the Goddard Ozone Chemistry Aerosol Radiation and Transport model (GOCART). The aerosol extinction coefficient, single scattering albedo, and asymmetric factor are computed as wavelength-dependent radiative forcing in the radiative transfer scheme of the fvGCM, and as a function of the aerosol loading and ambient relative humidity. We find that anomalous atmospheric heat sources induced by absorbing aerosols (dust and black carbon) excites a planetary scale teleconnection pattern in sea level pressure, temperature and geopotential height spanning North Africa through Eurasia to the North Pacific. Surface cooling due to direct effects of aerosols is found in the vicinity and downstream of the aerosol source regions, i.e., South Asia, East Asia, and northern and western Africa. Additionally, atmospheric heating is found in regions with large loading of dust (over Northern Africa, and Middle East), and black carbon (over South-East Asia). Paradoxically, the most pronounced feature in aerosol-induced surface temperature is an east-west dipole anomaly with strong cooling over the Caspian Sea, and warming over central and northeastern Asia, where aerosol concentration are low. Analyses of circulation anomalies show that the dipole anomaly is a part of an atmospheric teleconnection driven by atmospheric heating anomalies induced by absorbing aerosols in the source regions, but the influence was conveyed globally through barotropic energy dispersion and sustained by feedback processes

  3. Radiative forcing and climate response to projected 21st century aerosol decreases

    NASA Astrophysics Data System (ADS)

    Westervelt, D. M.; Horowitz, L. W.; Naik, V.; Golaz, J.-C.; Mauzerall, D. L.

    2015-11-01

    It is widely expected that global emissions of atmospheric aerosols and their precursors will decrease strongly throughout the remainder of the 21st century, due to emission reduction policies enacted to protect human health. For instance, global emissions of aerosols and their precursors are projected to decrease by as much as 80 % by the year 2100, according to the four Representative Concentration Pathway (RCP) scenarios. The removal of aerosols will cause unintended climate consequences, including an unmasking of global warming from long-lived greenhouse gases. We use the Geophysical Fluid Dynamics Laboratory Coupled Climate Model version 3 (GFDL CM3) to simulate future climate over the 21st century with and without the aerosol emission changes projected by each of the RCPs in order to isolate the radiative forcing and climate response resulting from the aerosol reductions. We find that the projected global radiative forcing and climate response due to aerosol decreases do not vary significantly across the four RCPs by 2100, although there is some mid-century variation, especially in cloud droplet effective radius, that closely follows the RCP emissions and energy consumption projections. Up to 1 W m-2 of radiative forcing may be unmasked globally from 2005 to 2100 due to reductions in aerosol and precursor emissions, leading to average global temperature increases up to 1 K and global precipitation rate increases up to 0.09 mm day-1. However, when using a version of CM3 with reduced present-day aerosol radiative forcing (-1.0 W m-2), the global temperature increase for RCP8.5 is about 0.5 K, with similar magnitude decreases in other climate response parameters as well. Regionally and locally, climate impacts can be much larger than the global mean, with a 2.1 K warming projected over China, Japan, and Korea due to the reduced aerosol emissions in RCP8.5, as well as nearly a 0.2 mm day-1 precipitation increase, a 7 g m-2 LWP decrease, and a 2 μm increase in

  4. Towards a Global Aerosol Climatology: Preliminary Trends in Tropospheric Aerosol Amounts and Corresponding Impact on Radiative Forcing between 1950 and 1990

    NASA Technical Reports Server (NTRS)

    Tegen, Ina; Koch, Dorothy; Lacis, Andrew A.; Sato, Makiko

    1999-01-01

    A global aerosol climatology is needed in the study of decadal temperature change due to natural and anthropogenic forcing of global climate change. A preliminary aerosol climatology has been developed from global transport models for a mixture of sulfate and carbonaceous aerosols from fossil fuel burning, including also contributions from other major aerosol types such as soil dust and sea salt. The aerosol distributions change for the period of 1950 to 1990 due to changes in emissions of SO2 and carbon particles from fossil fuel burning. The optical thickness of fossil fuel derived aerosols increased by nearly a factor of 3 during this period, with particularly strong increase in eastern Asia over the whole time period. In countries where environmental laws came into effect since the early 1980s (e.g. US and western Europe), emissions and consequently aerosol optical thicknesses did not increase considerably after 1980, resulting in a shift in the global distribution pattern over this period. In addition to the optical thickness, aerosol single scattering albedos may have changed during this period due to different trends in absorbing black carbon and reflecting sulfate aerosols. However, due to the uncertainties in the emission trends, this change cannot be determined with any confidence. Radiative forcing of this aerosol distribution is calculated for several scenarios, resulting in a wide range of uncertainties for top-of-atmosphere (TOA) forcings. Uncertainties in the contribution of the strongly absorbing black carbon aerosol leads to a range in TOA forcings of ca. -0.5 to + 0.1 Wm (exp. -2), while the change in aerosol distributions between 1950 to 1990 leads to a change of -0.1 to -0.3 Wm (exp. -2), for fossil fuel derived aerosol with a "moderate" contribution of black carbon aerosol.

  5. Design of Aerosol Particle Coating: Thickness, Texture and Efficiency

    PubMed Central

    Buesser, B.; Pratsinis, S.E.

    2013-01-01

    Core-shell particles preserve the performance (e.g. magnetic, plasmonic or opacifying) of a core material while modifying its surface with a shell that facilitates (e.g. by blocking its reactivity) their incorporation into a host liquid or polymer matrix. Here coating of titania (core) aerosol particles with thin silica shells (films or layers) is investigated at non-isothermal conditions by a trimodal aerosol dynamics model, accounting for SiO2 generation by gas phase and surface oxidation of hexamethyldisiloxane (HMDSO) vapor, coagulation and sintering. After TiO2 particles have reached their final primary particle size (e.g. upon completion of sintering during their flame synthesis), coating starts by uniformly mixing them with HMDSO vapor that is oxidized either in the gas phase or on the particles’ surface resulting in SiO2 aerosols or deposits, respectively. Sintering of SiO2 deposited onto the core TiO2 particles takes place transforming rough into smooth coating shells depending on process conditions. The core-shell characteristics (thickness, texture and efficiency) are calculated for two limiting cases of coating shells: perfectly smooth (e.g. hermetic) and fractal-like. At constant TiO2 core particle production rate, the influence of coating weight fraction, surface oxidation and core particle size on coating shell characteristics is investigated and compared to pertinent experimental data through coating diagrams. With an optimal temperature profile for complete precursor conversion, the TiO2 aerosol and SiO2-precursor (HMDSO) vapor concentrations have the strongest influence on product coating shell characteristics. PMID:23729833

  6. Efficiency tests of samplers for microbiological aerosols, a review

    NASA Technical Reports Server (NTRS)

    Henningson, E.; Faengmark, I.

    1984-01-01

    To obtain comparable results from studies using a variety of samplers of microbiological aerosols with different collection performances for various particle sizes, methods reported in the literature were surveyed, evaluated, and tabulated for testing the efficiency of the samplers. It is concluded that these samplers were not thoroughly tested, using reliable methods. Tests were conducted in static air chambers and in various outdoor and work environments. Results are not reliable as it is difficult to achieve stable and reproducible conditions in these test systems. Testing in a wind tunnel is recommended.

  7. Investigating the Internal Structure of Individual Aerosol Particles Using Atomic Force and Raman Microscopies

    NASA Astrophysics Data System (ADS)

    Freedman, M. A.; Baustian, K. J.; Wise, M. E.; Tolbert, M. A.

    2009-12-01

    We have used Atomic Force Microscopy (AFM) and Raman Microscopy to probe aerosol internal structures in order to understand the optical properties of aerosols composed of mixtures of organic and inorganic components. While AFM gives only topographical information about the particles, indirect chemical information can be obtained by using substrates with different surface properties. With Raman microscopy, chemical signatures of the components of the aerosol are obtained, but we have limited spatial resolution. We have explored the use of these two techniques to look at aerosol internal structure using a range of different model aerosols composed of mixtures of ammonium sulfate with organic compounds of various solubilities such as sucrose, succinic acid, and palmitic acid. At the extremes of solubility, AFM provides suitable information for interpreting aerosol microstructure. For example, AFM clearly shows the presence of core-shell structures for aerosol particles composed of palmitic acid and ammonium sulfate, while the results for aerosol particles composed of succinic acid and ammonium sulfate are more difficult to interpret. Information about size and shape can be obtained when hydrophilic particles are impacted on hydrophobic substrates and vise versa. With Raman microscopy, core-shell structures were readily identified for ammonium sulfate with palmitic acid or succinic acid coatings. For the case of succinic acid and ammonium sulfate mixtures, we are using microscopy results to aid in interpreting the refractive indices we retrieved from cavity ring-down studies.

  8. A Strategy to Assess Aerosol Direct Radiative Forcing of Climate Using Satellite Radiation Measurements

    NASA Technical Reports Server (NTRS)

    Kaufman, Yoram J.; Tanre, Didier; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Atmospheric aerosols have a complex internal chemical composition and optical properties. Therefore it is difficult to model their impact on redistribution and absorption of solar radiation, and the consequent impact on atmospheric dynamics and climate. The use in climate models of isolated aerosol parameters retrieved from satellite data (e.g. optical thickness) may result in inconsistent calculations, if the model assumptions differ from these of the satellite retrieval schemes. Here we suggest a strategy to assess the direct impact of aerosol on the radiation budget at the top and bottom of the atmosphere using satellite and ground based measurements of the spectral solar radiation scattered by the aerosol. This method ensures consistent use of the satellite data and increases its accuracy. For Kaufman and Tanre: Strategy for aerosol direct forcing anthropogenic aerosol in the fine mode (e.g. biomass burning smoke and urban pollution) consistent use of satellite derived optical thickness can yield the aerosol impact on the spectral solar flux with accuracy an order of magnitude better than the optical thickness itself. For example, a simulated monthly average smoke optical thickness of 0.5 at 0.55 microns (forcing of 40-50 W/sq m) derived with an error of 20%, while the forcing can be measured directly with an error of only 0-2 W/sq m. Another example, the effect of large dust particles on reflection of solar flux can be derived three times better than retrievals of optical thickness. Since aerosol impacts not only the top of the atmosphere but also the surface irradiation, a combination of satellite and ground based measurements of the spectral flux, can be the most direct mechanism to evaluate the aerosol effect on climate and assimilate it in climate models. The strategy is applied to measurements from SCAR-B and the Tarfox experiments. In SCAR-B aircraft spectral data are used to derive the 24 hour radiative forcing of smoke at the top of the atmosphere of

  9. Leaks in nuclear grade high efficiency aerosol filters

    SciTech Connect

    Scripsick, R.C.

    1994-07-01

    Nuclear grade high efficiency aerosol filters, also known as high efficiency particulate air (HEPA) filters, are commonly used in air cleaning systems for removal of hazardous aerosols. Performance of the filter units is important in assuring health and environmental protection. The filter units are constructed from pleated packs of fiberglass filter media sealed into rigid frames. Results of previous studies on such filter units indicate that their performance may not be completely predicted by ideal performance of the fibrous filter media. In this study, departure from ideal performance is linked to leaks existing in filter units and overall filter unit performance is derived from independent performance of the individual filter unit components. The performance of 14 nuclear grade HEPA filter units (size 1, 25 cfm) with plywood frames was evaluated with a test system that permitted independent determination of penetration as a function of particle size for the whole filter unit, the filter unit frame, and the filter media pack. Tests were performed using a polydisperse aerosol of di-2-ethylhexyl phthalate with a count median diameter of 0.2 {mu}m and geometric standard deviation of 1.6. Flow rate and differential pressure were controlled from 1% to 100% of design values. Particle counts were made upstream and downstream of the filter unit with an optical particle counter (OPC). The OPC provided count information in 28 size channels over the particle diameter range from 0.1 to 0.7 {mu}m. Results provide evidence for a two component leak model of filler unit performance with: (1) external leaks through filter unit frames, and (2) internal leaks through defects in the media and through the seal between the media pack and frame. For the filter units evaluated, these leaks dominate overall filter unit performance over much of the flow rate and particle size ranges tested.

  10. Aerosol transport and deposition efficiency in the respiratory airways

    NASA Astrophysics Data System (ADS)

    Nicolaou, Laura; Zaki, Tamer

    2015-11-01

    Prediction of aerosol deposition in the respiratory system is important for improving the efficiency of inhaled drug delivery and for assessing the toxicity of airborne pollutants. Particle deposition in the airways is typically described as a function of the Stokes number based on a reference flow timescale. This choice leads to significant scatter in deposition data since the velocity and length scales experienced by the particles as they are advected through the flow deviate considerably from the reference values in many sections of the airways. Therefore, the use of an instantaneous Stokes number based on the local properties of the flow field is proposed instead. We define the effective Stokes number as the time-average of the instantaneous value. Our results demonstrate that this average, or effective, Stokes number can deviate significantly from the reference value particularly in the intermediate Stokes number range. In addition, the effective Stokes number shows a very clear correlation with deposition efficiency, and is therefore a more appropriate parameter to describe aerosol transport.

  11. Coupling Satellite and Ground-Based Instruments to Map Climate Forcing by Anthropogenic Aerosols

    NASA Technical Reports Server (NTRS)

    Charlson, Robert J.; Anderson, Theodore L.; Hostetler, Chris (Technical Monitor)

    2000-01-01

    Climate forcing by anthropogenic aerosols is a significant but highly uncertain factor in global climate change. Only satellites can offer the global coverage essential to reducing this uncertainty; however, satellite measurements must be coupled with correlative, in situ measurements both to constrain the aerosol optical properties required in satellite retrieval algorithms and to provide chemical identification of aerosol sources. This grant funded the first two years of a three-year project which seeks to develop methodologies for combining spaceborne lidar with in-situ aerosol data sets to improve estimates of direct aerosol climate forcing. Progress under this two-year grant consisted in the development and deployment of a new in-situ capability for measuring aerosol 180' backscatter and the extinction-to-backscatter ratio. This new measurement capacity allows definitive lidar/in-situ comparisons and improves our ability to interpret lidar data in terms of climatically relevant quantities such as the extinction coefficient and optical depth. Measurements were made along the coast of Washington State, in Central Illinois, over the Indian Ocean, and in the Central Pacific. Thus, this research, combined with previous measurements by others, is rapidly building toward a global data set of extinction-to-backscatter ratio for key aerosol types. Such information will be critical to interpreting lidar data from the upcoming PICASSO-CENA, or P-C, satellite mission. Another aspect of this project is to investigate innovative ways to couple the lidar-satellite signal with targeted in-situ measurements toward a direct determination of aerosol forcing. This aspect is progressing in collaboration with NASA Langley's P-C lidar simulator and radiative transfer modeling by the University of Lille, France.

  12. Coupling Satellite and Ground-Based Instruments to Map Climate Forcing by Anthropogenic Aerosol

    NASA Technical Reports Server (NTRS)

    Charlson, Robert J.; Anderson, Theodore L.; Hostetler, Chris (Technical Monitor)

    2000-01-01

    Climate forcing by anthropogenic aerosols is a significant but highly uncertain factor in global climate change. Only satellites can offer the global coverage essential to reducing this uncertainty; however, satellite measurements must be coupled with correlative, in situ measurements both to constrain the aerosol optical properties required in satellite retrieval algorithms and to provide chemical identification of aerosol sources. This grant funded the third year of a three-year project which seeks to develop methodologies for combining spaceborne lidar with in-situ aerosol data sets to improve estimates of direct aerosol climate forcing. Progress under this one-year grant consisted in analysis and publication of field studies using a new in-situ capability for measuring aerosol 180 deg backscatter and the extinction-to-backscatter ratio. This new measurement capacity allows definitive lidar/in-situ comparisons and improves our ability to interpret lidar data in terms of climatically relevant quantities such as the extinction coefficient and optical depth. Analyzed data consisted of measurements made along the coast of Washington State, in Central Illinois, over the Indian Ocean, and in the Central Pacific. Thus, this research, combined with previous measurements by others, is rapidly building toward a global data set of extinction-to-backscatter ratio for key aerosol types. Such information will be critical to interpreting lidar data from the upcoming PICASSO-CENA, or P-C, satellite mission. Another aspect of this project is to investigate innovative ways to couple the lidar-satellite signal with target in-situ measurements toward a direct determination of aerosol forcing. This aspect is progressing in collaboration with NASA Langley's P-C lidar simulator.

  13. Host Model Uncertainties in Aerosol Radiative Forcing Estimates: Results from the AeroCom Prescribed Intercomparison Study

    SciTech Connect

    Stier, Phillip; Schutgens, Nick A.; Bellouin, N.; Bian, Huisheng; Boucher, Olivier; Chin, Mian; Ghan, Steven J.; Huneeus, N.; Kinne, Stefan; Lin, G.; Ma, Xiaoyan; Myhre, G.; Penner, J. E.; Randles, Cynthia; Samset, B. H.; Schulz, M.; Takemura, T.; Yu, Fangqun; Yu, Hongbin; Zhou, Cheng

    2013-03-20

    Simulated multi-model "diversity" in aerosol direct radiative forcing estimates is often perceived as mea- sure of aerosol uncertainty. However, current models used for aerosol radiative forcing calculations vary considerably in model components relevant for forcing calculations and the associated "host-model uncertainties" are generally convoluted with the actual aerosol uncertainty. In this AeroCom Prescribed intercomparison study we systematically isolate and quantify host model uncertainties on aerosol forcing experiments through prescription of identical aerosol radiative properties in nine participating models. Even with prescribed aerosol radiative properties,simulated clear-sky and all-sky aerosol radiative forcings show significant diversity. For a purely scattering case with globally constant optical depth of 0.2, the global-mean all-sky top-of-atmosphere radiative forcing is -4.51 Wm-2 and the inter-model standard deviation is 0.70 Wm-2, corresponding to a relative standard deviation of 15%. For a case with partially absorbing aerosol with an aerosol optical depth of 0.2 and single scattering albedo of 0.8, the forcing changes to 1.26 Wm-2, and the standard deviation increases to 1.21 W-2, corresponding to a significant relative standard deviation of 96%. However, the top-of-atmosphere forcing variability owing to absorption is low, with relative standard deviations of 9% clear-sky and 12% all-sky. Scaling the forcing standard deviation for a purely scattering case to match the sulfate radiative in the AeroCom Direct Effect experiment, demonstrates that host model uncertain- ties could explain about half of the overall sulfate forcing diversity of 0.13 Wm-2 in the AeroCom Direct Radiative Effect experiment. Host model errors in aerosol radiative forcing are largest in regions of uncertain host model components, such as stratocumulus cloud decks or areas with poorly constrained.

  14. Column-integrated aerosol optical properties and direct radiative forcing over the urban-industrial megacity Nanjing in the Yangtze River Delta, China.

    PubMed

    Kang, Na; Kumar, K Raghavendra; Yu, Xingna; Yin, Yan

    2016-09-01

    Aerosol optical properties were measured and analyzed through the ground-based remote sensing Aerosol Robotic Network (AERONET) over an urban-industrial site, Nanjing (32.21° N, 118.72° E, and 62 m above sea level), in the Yangtze River Delta, China, during September 2007-August 2008. The annual averaged values of aerosol optical depth (AOD500) and the Ångström exponent (AE440-870) were measured to be 0.94 ± 0.52 and 1.10 ± 0.21, respectively. The seasonal averaged values of AOD500 (AE440-870) were noticed to be high in summer (autumn) and low in autumn (spring). The characterization of aerosol types showed the dominance of mixed type followed by the biomass burning and urban-industrial type of aerosol at Nanjing. Subsequently, the curvature (a 2) obtained from the second-order polynomial fit and the second derivative of AE (α') were also analyzed to understand the dominant aerosol type. The single scattering albedo at 440 nm (SSA440) varied from 0.88 to 0.93 with relatively lower (higher) values during the summer (spring), suggesting an increase in black carbon and mineral dust (desert dust) aerosols of absorbing (scattering) nature. The averaged monthly and seasonal evolutions of shortwave (0.3-4.0 μm) direct aerosol radiative forcing (DARF) values were computed from the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model both at the top of atmosphere (TOA) and bottom of atmosphere (SUR) during the study period. Further, the aerosol forcing efficiency (AFE) and the corresponding atmospheric heating rates (AHR) were also estimated from the forcing within the atmosphere (ATM). The derived DARF values, therefore, produced a warming effect within the atmosphere due to strong absorption of solar radiation.

  15. Column-integrated aerosol optical properties and direct radiative forcing over the urban-industrial megacity Nanjing in the Yangtze River Delta, China.

    PubMed

    Kang, Na; Kumar, K Raghavendra; Yu, Xingna; Yin, Yan

    2016-09-01

    Aerosol optical properties were measured and analyzed through the ground-based remote sensing Aerosol Robotic Network (AERONET) over an urban-industrial site, Nanjing (32.21° N, 118.72° E, and 62 m above sea level), in the Yangtze River Delta, China, during September 2007-August 2008. The annual averaged values of aerosol optical depth (AOD500) and the Ångström exponent (AE440-870) were measured to be 0.94 ± 0.52 and 1.10 ± 0.21, respectively. The seasonal averaged values of AOD500 (AE440-870) were noticed to be high in summer (autumn) and low in autumn (spring). The characterization of aerosol types showed the dominance of mixed type followed by the biomass burning and urban-industrial type of aerosol at Nanjing. Subsequently, the curvature (a 2) obtained from the second-order polynomial fit and the second derivative of AE (α') were also analyzed to understand the dominant aerosol type. The single scattering albedo at 440 nm (SSA440) varied from 0.88 to 0.93 with relatively lower (higher) values during the summer (spring), suggesting an increase in black carbon and mineral dust (desert dust) aerosols of absorbing (scattering) nature. The averaged monthly and seasonal evolutions of shortwave (0.3-4.0 μm) direct aerosol radiative forcing (DARF) values were computed from the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model both at the top of atmosphere (TOA) and bottom of atmosphere (SUR) during the study period. Further, the aerosol forcing efficiency (AFE) and the corresponding atmospheric heating rates (AHR) were also estimated from the forcing within the atmosphere (ATM). The derived DARF values, therefore, produced a warming effect within the atmosphere due to strong absorption of solar radiation. PMID:27234827

  16. Aerosol sampling and Transport Efficiency Calculation (ASTEC) and application to surtsey/DCH aerosol sampling system: Code version 1. 0: Code description and user's manual

    SciTech Connect

    Yamano, N.; Brockmann, J.E.

    1989-05-01

    This report describes the features and use of the Aerosol Sampling and Transport Efficiency Calculation (ASTEC) Code. The ASTEC code has been developed to assess aerosol transport efficiency source term experiments at Sandia National Laboratories. This code also has broad application for aerosol sampling and transport efficiency calculations in general as well as for aerosol transport considerations in nuclear reactor safety issues. 32 refs., 31 figs., 7 tabs.

  17. Aerosol size distribution and radiative forcing response to anthropogenically driven historical changes in biogenic secondary organic aerosol formation

    NASA Astrophysics Data System (ADS)

    D'Andrea, S. D.; Acosta Navarro, J. C.; Farina, S. C.; Scott, C. E.; Rap, A.; Farmer, D. K.; Spracklen, D. V.; Riipinen, I.; Pierce, J. R.

    2014-10-01

    and the global mean cloud-albedo aerosol indirect effect of between -0.008 and -0.056 W m-2. This change in aerosols, and the associated radiative forcing, could be a~largely overlooked and important anthropogenic aerosol effect on regional climates.

  18. Direct observations of shortwave aerosol radiative forcing at surface and its diurnal variation during the Asian dry season at southwest Indian peninsula

    NASA Astrophysics Data System (ADS)

    Mishra, Manoj Kumar; Rajeev, K.

    2016-08-01

    The Arabian Sea witnesses consistent occurrence of a large-scale aerosol plume transported by the northerlies from the Asian region during the dry season (December-April). This paper presents direct observations of the diurnal variation (and dependence on solar zenith angle, SZA) of instantaneous aerosol direct radiative forcing efficiency (IADRFE) and aerosol direct radiative forcing (ADRF) at surface during the period from December to March of 2010-2013 at Thiruvananthapuram (8.5°N, 77°E), an Indian peninsular station adjoining the Arabian Sea coast, which resides well within this aerosol plume. Magnitude of the IADRFE increases with SZA from -75 ± 20 W m-2 τ 500 -1 at SZA of ~80° to attain a peak value of -170 ± 30 W m-2 τ 500 -1 at SZA ~60° in March (~3 h before and after the local noon). Absolute magnitudes and SZA dependence of the observed seasonal mean IADRFE are in agreement (within 16 % of the absolute magnitudes) with those estimated using radiation transfer computations employing an aerosol model with visible band single-scattering albedo of ~0.90 ± 0.03. Observed values of the diurnal mean aerosol radiative forcing efficiency (ADRFE) averaged during the season (December-March) vary between -71 and -76.5 W m-2 τ 500 -1 , which is in agreement with the model estimate of -71 W m-2 τ 500 -1 . The present observations show that the seasonal mean ADRF at surface (-25 to -28 W m-2) is about 10 % of the diurnal mean downwelling shortwave flux reaching the surface (in the absence of aerosols) during dry season at this location, indicating the major role of aerosols in regulating surface energetics.

  19. Effects of sulfate aerosol forcing on East Asian summer monsoon for 1985-2010

    NASA Astrophysics Data System (ADS)

    Kim, Minjoong J.; Yeh, Sang-Wook; Park, Rokjin J.

    2016-02-01

    We examine the effect of anthropogenic aerosol forcing on the East Asian summer monsoon (EASM) using the Community Atmosphere Model version 5.1.1. One control and two sensitivity model experiments were conducted in order to diagnose the separate roles played by sea surface temperature (SST) variations and anthropogenic sulfate aerosol forcing changes in East Asia. We find that the SST variation has been a major driver for the observed weakening of the EASM, whereas the effect of the anthropogenic aerosol forcing has been opposite and has slightly intensified the EASM over the recent decades. The reinforcement of the EASM results from radiative cooling by the sulfate aerosol forcing, which decelerates the jet stream around the jet's exit region. Subsequently, the secondary circulation induced by such a change in the jet stream leads to the increase in precipitation around 18-23°N. This result indicates that the increase in anthropogenic emissions over East Asia may play a role in compensating for the weakening of the EASM caused by the SST forcing.

  20. Challenges in constraining anthropogenic aerosol effects on cloud radiative forcing using present-day spatiotemporal variability.

    PubMed

    Ghan, Steven; Wang, Minghuai; Zhang, Shipeng; Ferrachat, Sylvaine; Gettelman, Andrew; Griesfeller, Jan; Kipling, Zak; Lohmann, Ulrike; Morrison, Hugh; Neubauer, David; Partridge, Daniel G; Stier, Philip; Takemura, Toshihiko; Wang, Hailong; Zhang, Kai

    2016-05-24

    A large number of processes are involved in the chain from emissions of aerosol precursor gases and primary particles to impacts on cloud radiative forcing. Those processes are manifest in a number of relationships that can be expressed as factors dlnX/dlnY driving aerosol effects on cloud radiative forcing. These factors include the relationships between cloud condensation nuclei (CCN) concentration and emissions, droplet number and CCN concentration, cloud fraction and droplet number, cloud optical depth and droplet number, and cloud radiative forcing and cloud optical depth. The relationship between cloud optical depth and droplet number can be further decomposed into the sum of two terms involving the relationship of droplet effective radius and cloud liquid water path with droplet number. These relationships can be constrained using observations of recent spatial and temporal variability of these quantities. However, we are most interested in the radiative forcing since the preindustrial era. Because few relevant measurements are available from that era, relationships from recent variability have been assumed to be applicable to the preindustrial to present-day change. Our analysis of Aerosol Comparisons between Observations and Models (AeroCom) model simulations suggests that estimates of relationships from recent variability are poor constraints on relationships from anthropogenic change for some terms, with even the sign of some relationships differing in many regions. Proxies connecting recent spatial/temporal variability to anthropogenic change, or sustained measurements in regions where emissions have changed, are needed to constrain estimates of anthropogenic aerosol impacts on cloud radiative forcing.

  1. Aerosol Properties and Radiative Forcing over Mega-cities in China

    NASA Astrophysics Data System (ADS)

    Li, Z.

    2007-12-01

    As the fastest and largest developing country in the world, China is experiencing rapid environmental changes. High concentrations of aerosols with diverse properties are emitted in the region, providing a unique opportunity for understanding the impact of environmental changes on climate. Until very recently, few observational studies were conducted in this important source region. The East Asian Study of Tropospheric Aerosols: an International Regional Experiment (EAST-AIRE) attempts to characterize the physical, optical and chemical properties of the aerosols and their effects on climate over China. Some preliminary results will be presented using continuous high-quality measurements of aerosol, cloud and radiative quantities made at the EAST-AIRE baseline stations near two mega cities (Beijing and Shanhai) in northern and southern China. Both regions are often covered by a thick layer of haze (with a yearly mean aerosol optical depth 0.7-0.8) due primarily to anthropogenic emissions of moderately strong absorbing aerosols, leading exceptionally large aerosol radiative forcing.

  2. Direct and semi-direct radiative forcing of smoke aerosols over clouds

    NASA Astrophysics Data System (ADS)

    Wilcox, E. M.

    2012-01-01

    Observations from Earth observing satellites indicate that dark carbonaceous aerosols that absorb solar radiation are widespread in the tropics and subtropics. When these aerosols mix with clouds, there is generally a reduction of cloudiness owing to absorption of solar energy in the aerosol layer. Over the subtropical South Atlantic Ocean, where smoke from savannah burning in southern Africa resides above a persistent deck of marine stratocumulus clouds, radiative heating of the smoke layer leads to a thickening of the cloud layer. Here, satellite observations of the albedo of overcast scenes of 25 km2 size or larger are combined with additional satellite observations of clouds and aerosols to estimate the top-of-atmosphere direct radiative forcing attributable to presence of dark aerosol above bright cloud, and the negative semi-direct forcing attributable to the thickening of the cloud layer. The average positive direct radiative forcing by smoke over an overcast scene is 9.2±6.6 W m-2 for cases with an unambiguous signal of absorbing aerosol over cloud in passive ultraviolet remote sensing observations. However, cloud liquid water path is enhanced by 16.3±7.7 g m-2 across the range of values for sea surface temperature for cases of smoke over cloud. The negative radiative forcing associated with this semi-direct effect of smoke over clouds is estimated to be -5.9±3.5 W m-2. Therefore, the cooling associated with the semi-direct cloud thickening effect compensates for greater than 60 % of the direct radiative effect. Accounting for the frequency of occurrence of significant absorbing aerosol above overcast scenes leads to an estimate of the average direct forcing of 1.0±0.7 W m-2 contributed by these scenes averaged over the subtropical southeast Atlantic Ocean during austral winter. The regional average of the negative semi-direct forcing is -0.7±0.4 W m-2. Therefore, smoke aerosols overlaying the decks of overcast marine stratocumulus clouds considered

  3. Direct and semi-direct radiative forcing of smoke aerosols over clouds

    NASA Astrophysics Data System (ADS)

    Wilcox, E. M.

    2011-07-01

    Observations from Earth observing satellites indicate that dark carbonaceous aerosols that absorb solar radiation are widespread in the tropics and subtropics. When these aerosols mix with clouds, there is generally a reduction of cloudiness owing to absorption of solar energy in the aerosol layer. Over the subtropical South Atlantic Ocean, where smoke from savannah burning in southern Africa resides above a persistent deck of marine stratocumulus clouds, radiative heating of the smoke layer leads to a thickening of the cloud layer. Here, satellite observations of the albedo of overcast scenes of 25 km2 size or larger are combined with additional satellite observations of clouds and aerosols to estimate the top-of-atmosphere direct radiative forcing attributable to presence of dark aerosol above bright cloud, and the negative semi-direct forcing attributable to the thickening of the cloud layer. The average positive direct radiative forcing by smoke over an overcast scene is 9.2±6.6 W m-2 for cases with an unambiguous signal of absorbing aerosol over cloud in passive ultraviolet remote sensing observations. However, cloud liquid water path is enhanced by 16.3±7.7 g m-2 across the range of values for sea surface temperature for cases of smoke over cloud. The negative radiative forcing associated with this semi-direct effect of smoke over clouds is estimated to be -5.9±3.5 W m-2. Therefore, the cooling associated with the semi-direct cloud thickening effect compensates for greater than 60 % of the direct radiative effect. Accounting for the frequency of occurrence of significant absorbing aerosol above overcast scenes leads to an estimate of the average direct forcing of 1.0±0.7 W m-2 contributed by these scenes averaged over the subtropical southeast Atlantic Ocean during austral winter. The regional average of the negative semi-direct forcing is -0.7±0.4 W m-2. Therefore, smoke aerosols overlaying the decks of overcast marine stratocumulus clouds considered

  4. Aerosol and ozone changes as forcing for climate evolution between 1850 and 2100

    NASA Astrophysics Data System (ADS)

    Szopa, Sophie; Balkanski, Y.; Schulz, M.; Bekki, S.; Cugnet, D.; Fortems-Cheiney, A.; Turquety, S.; Cozic, A.; Déandreis, C.; Hauglustaine, D.; Idelkadi, A.; Lathière, J.; Lefevre, F.; Marchand, M.; Vuolo, R.; Yan, N.; Dufresne, J.-L.

    2013-05-01

    Global aerosol and ozone distributions and their associated radiative forcings were simulated between 1850 and 2100 following a recent historical emission dataset and under the representative concentration pathways (RCP) for the future. These simulations were used in an Earth System Model to account for the changes in both radiatively and chemically active compounds, when simulating the climate evolution. The past negative stratospheric ozone trends result in a negative climate forcing culminating at -0.15 W m-2 in the 1990s. In the meantime, the tropospheric ozone burden increase generates a positive climate forcing peaking at 0.41 W m-2. The future evolution of ozone strongly depends on the RCP scenario considered. In RCP4.5 and RCP6.0, the evolution of both stratospheric and tropospheric ozone generate relatively weak radiative forcing changes until 2060-2070 followed by a relative 30 % decrease in radiative forcing by 2100. In contrast, RCP8.5 and RCP2.6 model projections exhibit strongly different ozone radiative forcing trajectories. In the RCP2.6 scenario, both effects (stratospheric ozone, a negative forcing, and tropospheric ozone, a positive forcing) decline towards 1950s values while they both get stronger in the RCP8.5 scenario. Over the twentieth century, the evolution of the total aerosol burden is characterized by a strong increase after World War II until the middle of the 1980s followed by a stabilization during the last decade due to the strong decrease in sulfates in OECD countries since the 1970s. The cooling effects reach their maximal values in 1980, with -0.34 and -0.28 W m-2 respectively for direct and indirect total radiative forcings. According to the RCP scenarios, the aerosol content, after peaking around 2010, is projected to decline strongly and monotonically during the twenty-first century for the RCP8.5, 4.5 and 2.6 scenarios. While for RCP6.0 the decline occurs later, after peaking around 2050. As a consequence the relative

  5. Influence of atmospheric relative humidity on ultraviolet flux and aerosol direct radiative forcing: Observation and simulation

    NASA Astrophysics Data System (ADS)

    Xia, Dong; Chen, Ling; Chen, Huizhong; Luo, Xuyu; Deng, Tao

    2016-08-01

    The atmospheric aerosols can absorb moisture from the environment due to their hydrophilicity and thus affect atmospheric radiation fluxes. In this article, the ultraviolet radiation and relative humidity (RH) data from ground observations and a radiative transfer model were used to examine the influence of RH on ultraviolet radiation flux and aerosol direct radiative forcing under the clear-sky conditions. The results show that RH has a significant influence on ultraviolet radiation because of aerosol hygroscopicity. The relationship between attenuation rate and RH can be fitted logarithmically and all of the R2 of the 4 sets of samples are high, i.e. 0.87, 0.96, 0.9, and 0.9, respectively. When the RH is 60%, 70%, 80% and 90%, the mean aerosol direct radiative forcing in ultraviolet is -4.22W m-2, -4.5W m-2, -4.82W m-2 and -5.4W m-2, respectively. For the selected polluted air samples the growth factor for computing aerosol direct radiative forcing in the ultraviolet for the RH of 80% varies from 1.19 to 1.53, with an average of 1.31.

  6. Radiative Forcing Due to Major Aerosol Emitting Sectors in China and India

    NASA Technical Reports Server (NTRS)

    Streets, David G.; Shindell, Drew Todd; Lu, Zifeng; Faluvegi, Greg

    2013-01-01

    Understanding the radiative forcing caused by anthropogenic aerosol sources is essential for making effective emission control decisions to mitigate climate change. We examined the net direct plus indirect radiative forcing caused by carbonaceous aerosol and sulfur emissions in key sectors of China and India using the GISS-E2 chemistry-climate model. Diesel trucks and buses (67 mW/ sq. m) and residential biofuel combustion (52 mW/ sq. m) in India have the largest global mean, annual average forcings due mainly to the direct and indirect effects of BC. Emissions from these two sectors in China have near-zero net global forcings. Coal-fired power plants in both countries exert a negative forcing of about -30 mW/ sq. m from production of sulfate. Aerosol forcings are largest locally, with direct forcings due to residential biofuel combustion of 580 mW/ sq. m over India and 416 mW/ sq. m over China, but they extend as far as North America, Europe, and the Arctic

  7. Aerosol and Cloud Radiative Forcing in China: Preliminary Results from the EAST-AIRE

    NASA Astrophysics Data System (ADS)

    Li, Z.; Cribb, M.; Xia, X.; Chen, H.; Wang, P.

    2005-12-01

    East Asia, and China in particular, is a region that can provide crucial and unique information concerning natural and anthropogenic aerosols and their impact on fundamental climate issues. Until very recently, few observational studies were conducted in this region of heavy aerosol loading and unique properties. The East Asian Study of Tropospheric Aerosols: an International Regional Experiment (EAST-AIRE) is an attempt to more fully characterize the physical, optical and chemical properties of these aerosols in different parts of China. Currently, three ground observation stations have been established under the aegis of this experiment. They include Xianghe (70 km southeast of Beijing), Liaozhong (50 km west of Shenyang), and Tai Lake (central to three mega-cities Shanghai, Hangzhou and Nanjing). Measurements have been taken continuously over different periods of time. The measurements include radiative quantities (for example, longwave and shortwave broadband and narrowband irradiances, etc.), the sky condition from a total sky imager, and aerosol quantities such as optical depth and single-scattering albedo. A preliminary analysis of the data with regards to the aerosol radiative forcing at the top of the atmosphere and at the surface will be presented. Critical to this analysis is the identification of clear skies, which is problematic in this region due to the ubiquitous presence of aerosol in the atmosphere. Another challenge is the discrimination between haze and cloud. The synergy of multiple data sources from the ground and from satellite is shown to help in identifying sky condition so that aerosol and cloud forcing can be determined.

  8. Temporal Variability of Aerosol Properties during TCAP: Impact on Radiative Forcing

    SciTech Connect

    Kassianov, Evgueni I.; Barnard, James C.; Pekour, Mikhail S.; Berg, Larry K.; Fast, Jerome D.; Michalsky, Joseph J.; Lantz, K.; Hodges, G. B.

    2013-11-01

    Ground-based remote sensing and in situ observations of aerosol microphysical and optical properties have been collected during summertime (June-August, 2012) as part of the Two-Column Aerosol Project (TCAP; http://campaign.arm.gov/tcap/), which was supported by the U.S. Department of Energy’s (DOE’s) Atmospheric Radiation Measurement (ARM) Program (http://www.arm.gov/). The overall goal of the TCAP field campaign is to study the evolution of optical and microphysical properties of atmospheric aerosol transported from North America to the Atlantic and their impact on the radiation energy budget. During TCAP, the ground-based ARM Mobile Facility (AMF) was deployed on Cape Cod, an arm-shaped peninsula situated on the easternmost portion of Massachusetts (along the east coast of the United States) and that is generally downwind of large metropolitan areas. The AMF site was equipped with numerous instruments for sampling aerosol, cloud and radiative properties, including a Multi-Filter Rotating Shadowband Radiometer (MFRSR), a Scanning Mobility Particle Sizer (SMPS), an Aerodynamic Particle Sizer (APS), and a three-wavelength nephelometer. In this study we present an analysis of diurnal and day-to-day variability of the column and near-surface aerosol properties obtained from remote sensing (MFRSR data) and ground-based in situ measurements (SMPS, APS, and nephelometer data). In particular, we show that the observed diurnal variability of the MFRSR aerosol optical depth is strong and comparable with that obtained previously from the AERONET climatology in Mexico City, which has a larger aerosol loading. Moreover, we illustrate how the variability of aerosol properties impacts the direct aerosol radiative forcing at different time scales.

  9. Radiative forcing and climate response to projected 21st century aerosol decreases

    NASA Astrophysics Data System (ADS)

    Westervelt, D. M.; Horowitz, L. W.; Naik, V.; Mauzerall, D. L.

    2015-03-01

    It is widely expected that global emissions of atmospheric aerosols and their precursors will decrease strongly throughout the remainder of the 21st century, due to emission reduction policies enacted to protect human health. For instance, global emissions of aerosols and their precursors are projected to decrease by as much as 80% by the year 2100, according to the four Representative Concentration Pathway (RCP) scenarios. The removal of aerosols will cause unintended climate consequences, including an unmasking of global warming from long-lived greenhouse gases. We use the Geophysical Fluid Dynamics Laboratory Climate Model version 3 (GFDL CM3) to simulate future climate over the 21st century with and without the aerosol emission changes projected by each of the RCPs in order to isolate the radiative forcing and climate response resulting from the aerosol reductions. We find that the projected global radiative forcing and climate response due to aerosol decreases do not vary significantly across the four RCPs by 2100, although there is some mid-century variation, especially in cloud droplet effective radius, that closely follows the RCP emissions and energy consumption projections. Up to 1 W m-2 of radiative forcing may be unmasked globally from 2005 to 2100 due to reductions in aerosol and precursor emissions, leading to average global temperature increases up to 1 K and global precipitation rate increases up to 0.09 mm d-1. Regionally and locally, climate impacts can be much larger, with a 2.1 K warming projected over China, Japan, and Korea due to the reduced aerosol emissions in RCP8.5, as well as nearly a 0.2 mm d-1 precipitation increase, a 7 g m-2 LWP decrease, and a 2 μm increase in cloud droplet effective radius. Future aerosol decreases could be responsible for 30-40% of total climate warming by 2100 in East Asia, even under the high greenhouse gas emissions scenario (RCP8.5). The expected unmasking of global warming caused by aerosol reductions will

  10. A computationally efficient Multicomponent Equilibrium Solver for Aerosols (MESA)

    NASA Astrophysics Data System (ADS)

    Zaveri, Rahul A.; Easter, Richard C.; Peters, Leonard K.

    2005-12-01

    Development and application of a new Multicomponent Equilibrium Solver for Aerosols (MESA) is described for systems containing H+, NH4+, Na+, Ca2+, SO42-, HSO4-, NO3-, and Cl- ions. The equilibrium solution is obtained by integrating a set of pseudo-transient ordinary differential equations describing the precipitation and dissolution reactions for all the possible salts to steady state. A comprehensive temperature dependent mutual deliquescence relative humidity (MDRH) parameterization is developed for all the possible salt mixtures, thereby eliminating the need for a rigorous numerical solution when ambient RH is less than MDRH(T). The solver is unconditionally stable, mass conserving, and shows robust convergence. Performance of MESA was evaluated against the Web-based AIM Model III, which served as a benchmark for accuracy, and the EQUISOLV II solver for speed. Important differences in the convergence and thermodynamic errors in MESA and EQUISOLV II are discussed. The average ratios of speeds of MESA over EQUISOLV II ranged between 1.4 and 5.8, with minimum and maximum ratios of 0.6 and 17, respectively. Because MESA directly diagnoses MDRH, it is significantly more efficient when RH < MDRH. MESA's superior performance is partially due to its "hard-wired" code for the present system as opposed to EQUISOLV II, which has a more generalized structure for solving any number and type of reactions at temperatures down to 190 K. These considerations suggest that MESA is highly attractive for use in 3-D aerosol/air-quality models for lower tropospheric applications (T > 240 K) in which both accuracy and computational efficiency are critical.

  11. FRACTIONAL AEROSOL FILTRATION EFFICIENCY OF IN-DUCT VENTILATION AIR CLEANERS

    EPA Science Inventory

    The filtration efficiency of ventilation air cleaners is highly particle-size dependent over the 0.01 to 3 μm diameter size range. Current standardized test methods, which determine only overall efficiencies for ambient aerosol or other test aerosols, provide data of limited util...

  12. Evolution of Ozone, Particulates, and Aerosol Direct Radiative Forcing in the Vicinity of Houston Using a Fully Coupled Meteorology-Chemistry-Aerosol Model

    SciTech Connect

    Fast, Jerome D.; Gustafson, William I.; Easter, Richard C.; Zaveri, Rahul A.; Barnard, James C.; Chapman, Elaine G.; Grell, Georg; Peckham, S. E.

    2006-11-11

    A new fully-coupled meteorology-chemistry-aerosol model is used to simulate the urban to regional scale variations in trace gases, particulates, and aerosol direct radiative forcing in the vicinity of Houston over a five day summer period. Model performance is evaluated using a wide range of meteorological, chemistry, and particulate measurements obtained during 2000 Texas Air Quality Study. The predicted trace gas and particulate distributions were qualitatively similar to the surface and aircraft measurements with considerable spatial variations resulting from urban, power plant, and industrial sources of primary pollutants. Sulfate, organic carbon, and other inorganics were the largest constituents of the predicted particulates. The predicted shortwave radiation was 30 to 40 W m-2 closer to the observations when the aerosol optical properties were incorporated into the shortwave radiation scheme; however, the predicted hourly aerosol radiative forcing was still under-estimated by 10 to 50 W m-2. The predicted aerosol radiative forcing was larger over Houston and the industrial ship channel than over the rural areas, consistent with surface measurements. The differences between the observed and simulated aerosol radiative forcing resulted from transport errors, relative humidity errors in the upper convective boundary layer that affect aerosol water content, secondary organic aerosols that were not yet included in the model, and uncertainties in the primary particulate emission rates. The current model was run in a predictive mode and demonstrates the challenges of accurately simulating all of the meteorological, chemical, and aerosol parameters over urban to regional scales that can affect aerosol radiative forcing.

  13. The Spatial and Temporal Heterogeneity of Precipitation and Aerosol-Cloud Radiative Forcing Uncertainty in Climatically Important Regions

    NASA Astrophysics Data System (ADS)

    Regayre, L.; Pringle, K.; Lee, L.; Booth, B.; Browse, J.; Mann, G.; Woodhouse, M. T.; Reddington, C.; Carslaw, K. S.; Rap, A.

    2015-12-01

    Aerosol-cloud radiative forcing and precipitation sensitivities are quantified within climatically important regions, where surface temperatures and moisture availability are thought to influence large-scale climatic effects. The sensitivity of precipitation and the balance of incoming and outgoing radiation to uncertain historical aerosol emission fluxes and aerosol-cloud parametrisations are quantified and their climatic importance considered. The predictability of monsoon onset and intensity, position of the inter-tropical convergence zone, tropical storm frequency and intensity, heat transport to the Arctic and changes in the mode of the El Niño Southern Oscillation are all limited by the parametric uncertainties examined here. Precipitation and aerosol-cloud radiative forcing sensitivities are found to be both spatially and temporally heterogeneous. Statistical analysis highlights aspects of aerosol-climate research and model development that should be prioritised in order to reduce the impact of uncertainty in regional precipitation and aerosol-cloud forcing on near-term climate projections.

  14. Parameterization of the cloud-mediated radiative forcing of climate due to aerosols in the two-way coupled WRF-CMAQ over the continental United States

    NASA Astrophysics Data System (ADS)

    Yu, S.; Mathur, R.; Pleim, J.; Wong, D.; Carlton, A. G.; Roselle, S. J.; Rao, S.

    2010-12-01

    Atmospheric emissions resulting from consumption of fossil fuels by human activities contribute to global warming and degrade air quality. The IPCC (2007) concludes that the total direct aerosol radiative forcing is estimated to be -0.5 [±0.4] W m-2, with a medium-low level of scientific understanding, while the radiative forcing due to the cloud albedo effect (also referred to as first indirect), is estimated to be -0.7 [-1.1, +0.4] W m-2, with a low level of scientific understanding. For a given cloud liquid water content, an increase in the cloud droplet number concentration implies a decrease in the effective radius, thus increasing the cloud reflectivity; this is know as the first indirect aerosol effect. The second indirect aerosol effect is based on the idea that decreasing the mean droplet size in the presence of enhanced aerosols decreases the cloud precipitation efficiency, producing clouds with a larger liquid water content and longer lifetime. In this study, the indirect aerosol effect is estimated with the newly developed two-way coupled WRF-CMAQ over the continental United States. The cloud droplet number concentrations are diagnosed from the activation of CMAQ-predicted aerosol. The resulting cloud droplet number is used to calculate variations in droplet effective radius, which in turn allows us to estimate aerosol effects on cloud optical depth and microphysical processes using a two-moment treatment of cloud water (cloud water mass and cloud droplet number) to model effects on precipitation. With the satellite observation data such as CERES, MODIS and CALIPSO, we will evaluate the cloud properties such as cloud optical depth, cloud droplet effective radius, and liquid water content and indirect aerosol forcing in the newly-developed coupled WRF-CMAQ.

  15. A New Electrospray Aerosol Generator with High Particle Transmission Efficiency.

    PubMed

    Fu, Huijing; Patel, Anand C; Holtzman, Michael J; Chen, Da-Ren

    2011-01-01

    A new single-capillary electrospray (ES) aerosol generator has been developed for monodisperse particle production with maximal transmission efficiency. The new generator consists of both a spray chamber in a point-to-orifice-plate configuration and a charge reduction chamber that can hold up to 4 Nuclespot ionizers (Model P-2042, NRD Inc.). The 2 chambers are partitioned by an orifice plate. To optimize the particle transmission efficiency of the prototype, a systematic study was performed on the generator by varying the system setup and operation. Two key dimensions of the generator setup, the orifice diameter and the distance from the capillary tip to the orifice plate, were varied. Fluorescence analysis was applied to characterize the loss of ES-generated particles at different locations of the prototype. It was found that particle loss in the generator could be reduced by either increasing the orifice diameter or decreasing the distance between the capillary tip and the orifice plate. Increasing either the total radioactivity of the ionizers or the flowrate of the particle carrier gas also further decreased the particle loss in the system. The maximum particle transmission efficiency of 88.0% was obtained with the spray chamber fully opened to the charge reduction chamber, the capillary tip at the same level as the orifice plate, and 4 bipolar ionizers installed.

  16. A New Electrospray Aerosol Generator with High Particle Transmission Efficiency.

    PubMed

    Fu, Huijing; Patel, Anand C; Holtzman, Michael J; Chen, Da-Ren

    2011-01-01

    A new single-capillary electrospray (ES) aerosol generator has been developed for monodisperse particle production with maximal transmission efficiency. The new generator consists of both a spray chamber in a point-to-orifice-plate configuration and a charge reduction chamber that can hold up to 4 Nuclespot ionizers (Model P-2042, NRD Inc.). The 2 chambers are partitioned by an orifice plate. To optimize the particle transmission efficiency of the prototype, a systematic study was performed on the generator by varying the system setup and operation. Two key dimensions of the generator setup, the orifice diameter and the distance from the capillary tip to the orifice plate, were varied. Fluorescence analysis was applied to characterize the loss of ES-generated particles at different locations of the prototype. It was found that particle loss in the generator could be reduced by either increasing the orifice diameter or decreasing the distance between the capillary tip and the orifice plate. Increasing either the total radioactivity of the ionizers or the flowrate of the particle carrier gas also further decreased the particle loss in the system. The maximum particle transmission efficiency of 88.0% was obtained with the spray chamber fully opened to the charge reduction chamber, the capillary tip at the same level as the orifice plate, and 4 bipolar ionizers installed. PMID:22829715

  17. Past and future direct radiative forcing of nitrate aerosol in East Asia

    NASA Astrophysics Data System (ADS)

    Li, Jiandong; Wang, Wei-Chyung; Liao, Hong; Chang, Wenyuan

    2015-08-01

    Nitrate as a rapidly increasing aerosol species in recent years affects the present climate and potentially has large implications on the future climate. In this study, the long-term direct radiative forcing (DRF) of nitrate aerosol is investigated using State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG) atmospheric general circulation model (AGCM) and the aerosol dataset simulated by a chemical transport model with focus on East Asia. The DRF due to other aerosols, especially sulfate, is also evaluated for comparisons. Although the chemical transport model underestimates the magnitudes of nitrate and sulfate aerosols when compared with Chinese site observations, some insights into the significances of nitrate climate effects still emerge. The present-day global annual mean all-sky DRF of nitrate is calculated to be -0.025 W m-2 relative to the preindustrial era, which is much weaker than -0.37 W m-2 for sulfate. However, nitrate DRF may become increasingly important in the future especially over East Asia, given the expectation that decreasing trend in global sulfate continues while the projected nitrate maintains at the present level for a mid-range forcing scenario and even be a factor of two larger by the end of the 21st century for high emission scenarios. For example, the anthropogenic nitrate DRF of -2.0 W m-2 over eastern China could persist until the 2050s, and nitrate is projected to account for over 60 % of total anthropogenic aerosol DRF over East Asia by 2100. In addition, we illustrate that the regional nitrate DRF and its seasonal variation are sensitive to meteorological parameters, in particular the relative humidity and cloud amount. It thus remains a need for climate models to include more realistically nitrate aerosol in projecting future climate changes.

  18. Absorbing Aerosols Above Cloud: Detection, Quantitative Retrieval, and Radiative Forcing from Satellite-based Passive Sensors

    NASA Astrophysics Data System (ADS)

    Jethva, H.; Torres, O.; Remer, L. A.; Bhartia, P. K.

    2012-12-01

    , respectively. This study constitutes the first attempt to use non-polarized and non-lidar reflectance observations-both of them shown to have above-cloud aerosols retrieval capability, to retrieve above-cloud AOT by a passive non-polarized sensor. The uncertainty analysis suggests that the present method should retrieve above-cloud AOT within -10% to 50% which mainly arises due to uncertainty associated with the single-scattering albedo assumption. Although, currently tested by making use of OMI and MODIS measurements, the present color ratio method can be equally applied to the other satellite measurements that carry similar or near-by channels in VIS region of the spectrum such as MISR and NPP/VIIRS. The capability of quantifying the above-cloud aerosol load will facilitate several aspects of cloud-aerosol interaction research such as estimation of the direct radiative forcing of aerosols above clouds; the sign of which can be opposite (warming) to cloud-free aerosol forcing (cooling), aerosol transport, indirect effects of aerosols on clouds, and hydrological cycle.

  19. On the influence of the diurnal variations of aerosol content to estimate direct aerosol radiative forcing using MODIS data

    NASA Astrophysics Data System (ADS)

    Xu, Hui; Guo, Jianping; Ceamanos, Xavier; Roujean, Jean-Louis; Min, Min; Carrer, Dominique

    2016-09-01

    Long-term measurements of aerosol optical depth (AOD) from the Aerosol Robotic Network (AERONET) located in Beijing reveal a strong diurnal cycle of aerosol load staged by seasonal patterns. Such pronounced variability is matter of importance in respect to the estimation of daily averaged direct aerosol radiative forcing (DARF). Polar-orbiting satellites could only offer a daily revisit, which turns in fact to be even much less in case of frequent cloudiness. Indeed, this places a severe limit to properly capture the diurnal variations of AOD and thus estimate daily DARF. Bearing this in mind, the objective of the present study is however to evaluate the impact of AOD diurnal variations for conducting quantitative assessment of DARF using Moderate Resolution Imaging Spectroradiometer (MODIS) AOD data over Beijing. We provide assessments of DARF with two different assumptions about diurnal AOD variability: taking the observed hourly-averaged AOD cycle into account and assuming constant MODIS (including Terra and Aqua) AOD value throughout the daytime. Due to the AOD diurnal variability, the absolute differences in annual daily mean DARFs, if the constant MODIS/Terra (MODIS/Aqua) AOD value is used instead of accounting for the observed hourly-averaged daily variability, is 1.2 (1.3) Wm-2 at the top of the atmosphere, 27.5 (30.6) Wm-2 at the surface, and 26.4 (29.3) Wm-2 in the atmosphere, respectively. During the summertime, the impact of the diurnal AOD variability on seasonal daily mean DARF estimates using MODIS Terra (Aqua) data can reach up to 2.2 (3.9) Wm-2 at the top of the atmosphere, 43.7 (72.7) Wm-2 at the surface, and 41.4 (68.8) Wm-2 in the atmosphere, respectively. Overall, the diurnal variation in AOD tends to cause large bias in the estimated DARF on both seasonal and annual scales. In summertime, the higher the surface albedo, the stronger impact on DARF at the top of the atmosphere caused by dust and biomass burning (continental) aerosol. This

  20. A Computationally Efficient Multicomponent Equilibrium Solver for Aerosols (MESA)

    SciTech Connect

    Zaveri, Rahul A.; Easter, Richard C.; Peters, Len K.

    2005-12-23

    deliquescence points as well as mass growth factors for the sulfate-rich systems. The MESA-MTEM configuration required only 5 to 10 single-level iterations to obtain the equilibrium solution for ~44% of the 328 multiphase problems solved in the 16 test cases at RH values ranging between 20% and 90%, while ~85% of the problems solved required less than 20 iterations. Based on the accuracy and computational efficiency considerations, the MESA-MTEM configuration is attractive for use in 3-D aerosol/air quality models.

  1. Direct radiative forcing properties of atmospheric aerosols over semi-arid region, Anantapur in India.

    PubMed

    Kalluri, Raja Obul Reddy; Gugamsetty, Balakrishnaiah; Kotalo, Rama Gopal; Nagireddy, Siva Kumar Reddy; Tandule, Chakradhar Rao; Thotli, Lokeswara Reddy; Rajuru Ramakrishna, Reddy; Surendranair, Suresh Babu

    2016-10-01

    This paper describes the aerosols optical, physical characteristics and the aerosol radiative forcing pertaining to semi-arid region, Anantapur for the period January 2013-December 2014. Collocated measurements of Aerosol Optical Depth (AOD) and Black Carbon mass concentration (BC) are carried out by using MICROTOPS II and Aethalometer and estimated the aerosol radiative forcing over this location. The mean values of AOD at 500nm are found to be 0.47±0.09, 0.34±0.08, 0.29±0.06 and 0.30±0.07 during summer, winter, monsoon and post-monsoon respectively. The Angstrom exponent (α380-1020) value is observed maximum in March (1.25±0.19) and which indicates the predominance of fine - mode aerosols and lowest in the month of July (0.33±0.14) and may be due to the dominance of coarse-mode aerosols. The diurnal variation of BC is exhibited two height peaks during morning 07:00-08:00 (IST) and evening 19:00-21:00 (IST) hours and one minima noticed during afternoon (13:00-16:00). The highest monthly mean BC concentration is observed in the month of January (3.4±1.2μgm(-3)) and the lowest in July (1.1±0.2μgm(-3)). The estimated Aerosol Direct Radiative Forcing (ADRF) in the atmosphere is found to be +36.8±1.7Wm(-2), +26.9±0.2Wm(-2), +18.0±0.6Wm(-2) and +18.5±3.1Wm(-2) during summer, winter, monsoon and post-monsoon seasons, respectively. Large difference between TOA and BOA forcing is observed during summer which indicate the large absorption of radiant energy (36.80Wm(-2)) which contributes more increase in atmospheric heating by ~1K/day. The BC contribution on an average is found to be 64% and is responsible for aerosol atmospheric heating.

  2. Direct radiative forcing properties of atmospheric aerosols over semi-arid region, Anantapur in India.

    PubMed

    Kalluri, Raja Obul Reddy; Gugamsetty, Balakrishnaiah; Kotalo, Rama Gopal; Nagireddy, Siva Kumar Reddy; Tandule, Chakradhar Rao; Thotli, Lokeswara Reddy; Rajuru Ramakrishna, Reddy; Surendranair, Suresh Babu

    2016-10-01

    This paper describes the aerosols optical, physical characteristics and the aerosol radiative forcing pertaining to semi-arid region, Anantapur for the period January 2013-December 2014. Collocated measurements of Aerosol Optical Depth (AOD) and Black Carbon mass concentration (BC) are carried out by using MICROTOPS II and Aethalometer and estimated the aerosol radiative forcing over this location. The mean values of AOD at 500nm are found to be 0.47±0.09, 0.34±0.08, 0.29±0.06 and 0.30±0.07 during summer, winter, monsoon and post-monsoon respectively. The Angstrom exponent (α380-1020) value is observed maximum in March (1.25±0.19) and which indicates the predominance of fine - mode aerosols and lowest in the month of July (0.33±0.14) and may be due to the dominance of coarse-mode aerosols. The diurnal variation of BC is exhibited two height peaks during morning 07:00-08:00 (IST) and evening 19:00-21:00 (IST) hours and one minima noticed during afternoon (13:00-16:00). The highest monthly mean BC concentration is observed in the month of January (3.4±1.2μgm(-3)) and the lowest in July (1.1±0.2μgm(-3)). The estimated Aerosol Direct Radiative Forcing (ADRF) in the atmosphere is found to be +36.8±1.7Wm(-2), +26.9±0.2Wm(-2), +18.0±0.6Wm(-2) and +18.5±3.1Wm(-2) during summer, winter, monsoon and post-monsoon seasons, respectively. Large difference between TOA and BOA forcing is observed during summer which indicate the large absorption of radiant energy (36.80Wm(-2)) which contributes more increase in atmospheric heating by ~1K/day. The BC contribution on an average is found to be 64% and is responsible for aerosol atmospheric heating. PMID:27344510

  3. Asymmetric forcing from stratospheric aerosols impacts Sahelian rainfall

    NASA Astrophysics Data System (ADS)

    Haywood, Jim M.; Jones, Andy; Bellouin, Nicolas; Stephenson, David

    2013-07-01

    The Sahelian drought of the 1970s-1990s was one of the largest humanitarian disasters of the past 50 years, causing up to 250,000 deaths and creating 10 million refugees. It has been attributed to natural variability, over-grazing and the impact of industrial emissions of sulphur dioxide. Each mechanism can influence the Atlantic sea surface temperature gradient, which is strongly coupled to Sahelian precipitation. We suggest that sporadic volcanic eruptions in the Northern Hemisphere also strongly influence this gradient and cause Sahelian drought. Using de-trended observations from 1900 to 2010, we show that three of the four driest Sahelian summers were preceded by substantial Northern Hemisphere volcanic eruptions. We use a state-of-the-art coupled global atmosphere-ocean model to simulate both episodic volcanic eruptions and geoengineering by continuous deliberate injection into the stratosphere. In either case, large asymmetric stratospheric aerosol loadings concentrated in the Northern Hemisphere are a harbinger of Sahelian drought whereas those concentrated in the Southern Hemisphere induce a greening of the Sahel. Further studies of the detailed regional impacts on the Sahel and other vulnerable areas are required to inform policymakers in developing careful consensual global governance before any practical solar radiation management geoengineering scheme is implemented.

  4. Brown carbon aerosols from burning of boreal peatlands: microphysical properties, emission factors, and implications for direct radiative forcing

    NASA Astrophysics Data System (ADS)

    Chakrabarty, Rajan K.; Gyawali, Madhu; Yatavelli, Reddy L. N.; Pandey, Apoorva; Watts, Adam C.; Knue, Joseph; Chen, Lung-Wen A.; Pattison, Robert R.; Tsibart, Anna; Samburova, Vera; Moosmüller, Hans

    2016-03-01

    The surface air warming over the Arctic has been almost twice as much as the global average in recent decades. In this region, unprecedented amounts of smoldering peat fires have been identified as a major emission source of climate-warming agents. While much is known about greenhouse gas emissions from these fires, there is a knowledge gap on the nature of particulate emissions and their potential role in atmospheric warming. Here, we show that aerosols emitted from burning of Alaskan and Siberian peatlands are predominantly brown carbon (BrC) - a class of visible light-absorbing organic carbon (OC) - with a negligible amount of black carbon content. The mean fuel-based emission factors for OC aerosols ranged from 3.8 to 16.6 g kg-1. Their mass absorption efficiencies were in the range of 0.2-0.8 m2 g-1 at 405 nm (violet) and dropped sharply to 0.03-0.07 m2 g-1 at 532 nm (green), characterized by a mean Ångström exponent of ≈ 9. Electron microscopy images of the particles revealed their morphologies to be either single sphere or agglomerated "tar balls". The shortwave top-of-atmosphere aerosol radiative forcing per unit optical depth under clear-sky conditions was estimated as a function of surface albedo. Only over bright surfaces with albedo greater than 0.6, such as snow cover and low-level clouds, the emitted aerosols could result in a net warming (positive forcing) of the atmosphere.

  5. Dust aerosol properties and radiative forcing observed in spring during 2001-2014 over urban Beijing, China.

    PubMed

    Yu, Xingna; Lü, Rui; Kumar, K Raghavendra; Ma, Jia; Zhang, Qiuju; Jiang, Yilun; Kang, Na; Yang, Suying; Wang, Jing; Li, Mei

    2016-08-01

    The ground-based characteristics (optical and radiative properties) of dust aerosols measured during the springtime between 2001 and 2014 were investigated over urban Beijing, China. The seasonal averaged aerosol optical depth (AOD) during spring of 2001-2014 was about 0.78 at 440 nm. During dust days, higher AOD occurred associated with lower Ångström exponent (AE). The mean AE440-870 in the springtime was about 1.0, indicating dominance of fine particles over the region. The back-trajectory analysis revealed that the dust was transported from the deserts of Inner Mongolia and Mongolia arid regions to Beijing. The aerosol volume size distribution showed a bimodal distribution pattern, with its highest peak observed in coarse mode for all episodes (especially for dust days with increased volume concentration). The single scattering albedo (SSA) increased with wavelength on dust days, indicating the presence of more scattering particles. Furthermore, the complex parts (real and imaginary) of refractive index showed distinct characteristics with lower imaginary values (also scattering) on dust days. The shortwave (SW; 0.2-4.0 μm) and longwave (LW; 4-100 μm) aerosol radiative forcing (ARF) values were computed from the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model both at the top of atmosphere (TOA) and the bottom of atmosphere (BOA) during dust and non-dust (dust free) days, and the corresponding heating rates and forcing efficiencies were also estimated. The SW (LW) ARF, therefore, produced significant cooling (warming) effects at both the TOA and the BOA over Beijing.

  6. The impact of humidity above stratiform clouds on indirect aerosol climate forcing.

    PubMed

    Ackerman, Andrew S; Kirkpatrick, Michael P; Stevens, David E; Toon, Owen B

    2004-12-23

    Some of the global warming from anthropogenic greenhouse gases is offset by increased reflection of solar radiation by clouds with smaller droplets that form in air polluted with aerosol particles that serve as cloud condensation nuclei. The resulting cooling tendency, termed the indirect aerosol forcing, is thought to be comparable in magnitude to the forcing by anthropogenic CO2, but it is difficult to estimate because the physical processes that determine global aerosol and cloud populations are poorly understood. Smaller cloud droplets not only reflect sunlight more effectively, but also inhibit precipitation, which is expected to result in increased cloud water. Such an increase in cloud water would result in even more reflective clouds, further increasing the indirect forcing. Marine boundary-layer clouds polluted by aerosol particles, however, are not generally observed to hold more water. Here we simulate stratocumulus clouds with a fluid dynamics model that includes detailed treatments of cloud microphysics and radiative transfer. Our simulations show that the response of cloud water to suppression of precipitation from increased droplet concentrations is determined by a competition between moistening from decreased surface precipitation and drying from increased entrainment of overlying air. Only when the overlying air is humid or droplet concentrations are very low does sufficient precipitation reach the surface to allow cloud water to increase with droplet concentrations. Otherwise, the response of cloud water to aerosol-induced suppression of precipitation is dominated by enhanced entrainment of overlying dry air. In this scenario, cloud water is reduced as droplet concentrations increase, which diminishes the indirect climate forcing.

  7. Direct radiative forcing of aerosols in cloudy condition using CALIPSO satellite data

    NASA Astrophysics Data System (ADS)

    Oikawa, E.; Nakajima, T.; Winker, D. M.

    2013-12-01

    The aerosol direct effect occurs by direct scattering and absorption of solar and thermal radiation. Shortwave direct aerosol radiative forcing (DARF) under clear-sky condition is estimated about 5 Wm-2 from satellite retrievals and model simulations [Yu et al., 2006ACP]. Simultaneous observations of aerosols and clouds are very limited, thus it is difficult to validate the estimation of DARF under cloudy-sky condition. In 2006, the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite was launched with the space-borne lidar, CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization). This enabled us to get data of the vertical distribution of aerosols and clouds all over the world. Oikawa et al. [2013JGR] estimated DARF under clear-sky, cloudy-sky, and all-sky conditions using CALIPSO and MODIS (Moderate resolution Imaging Spectrometer) data. Over Atlantic Ocean off southwest Africa, biomass burning aerosols are transported above low-level clouds and cause large positive DARF [Oikawa et al., 2013JGR; Chand et al., 2009Nat. Geosci.; De Graaf et al., 2012JGR; Takemura et al., 2005JGR]. We calculate DARF using CALIOP Level 2 Cloud and Aerosol Layer Products Version 3 and the method of Oikawa et al. [2013]. In this study, we focus on the case that aerosols exist above clouds (above-cloud case) in 2007. Over Atlantic Ocean off southwest Africa, DARF caused by smoke aerosols is +7.1 Wm-2 in September. On the other hand, aerosol optical thickness (AOT) of smoke is small as close to 0 Wm-2 in spring season. Over North Pacific, yellow sand and industrial smoke are transported from Asia and DARF is +5.2 Wm-2 in May. Dust AOT at 532 nm is 0.014 and polluted dust AOT at 532 nm is 0.052; in other words, a large part of dust emitted from Taklamakan and Gobi deserts are mixed with the industrial smoke and transported to the Pacific Ocean according to the CALIPSO algorithms.

  8. Radiative Forcing of the Pinatubo Aerosol as a Function of Latitude and Time

    NASA Technical Reports Server (NTRS)

    Bergstrom, R. W.; Kinne, S.; Russell, P. B.; Bauman, J. J.; Minnis, P.

    1996-01-01

    We present calculations of the radiative forcing of the Mt. Pinatubo aerosols as a function of latitude and time after the eruption and compare the results with GOES satellite data. The results from the model indicate that the net effect of the aerosol was to cool the earth-atmosphere system with the most significant radiative effect in the tropics (corresponding to the location of the tropical stratospheric reservoir) and at latitudes greater than 60 deg. The high-latitude maximum is a combined effect of the high-latitude peak in optical depth (Trepte et al 1994) and the large solar zenith angles. The comparison of the predicted and measured net flux shows relatively good agreement, with the model consistently under predicting the cooling effect of the aerosol.

  9. Radiative Forcing of the Pinatubo Aerosol as a Function of Latitude and Time

    NASA Technical Reports Server (NTRS)

    Bergstrom, Robert W.; Kinne, S.; Russell, P. B.; Bauman, J. J.; Minnis, P.

    2000-01-01

    We present calculations of the radiative forcing of the Mt. Pinatubo aerosols as a function of latitude and time after the eruption and compare the results with GOES satellite data. The results from the model indicate that the net effect of the aerosol was to cool the earth-atmosphere system with the most significant radiative effect in the tropics (corresponding to the location of the tropical stratospheric reservoir) and at latitudes greater than 60 degrees. The high-latitude maximum is a combined effect of the high-latitude peak in optical depth (Trepte et al 1994) and the large solar zenith angles. The comparison of the predicted and measured net flux shows relatively good agreement, with the model consistently under predicting the cooling effect of the aerosol.

  10. Quantifying the climatological cloud-free direct radiative forcing of aerosol over the Red Sea

    NASA Astrophysics Data System (ADS)

    Brindley, Helen; Osipov, Serega; Bantges, Richard; Smirnov, Alexander; Banks, Jamie; Levy, Robert; Prakash, P.-Jish; Stenchikov, Georgiy

    2015-04-01

    A combination of ground-based and satellite observations are used, in conjunction with column radiative transfer modelling, to assess the climatological aerosol loading and quantify its corresponding cloud-free direct radiative forcing (DRF) over the Red Sea. While there have been campaigns designed to probe aerosol-climate interactions over much of the world, relatively little attention has been paid to this region. Because of the remoteness of the area, satellite retrievals provide a crucial tool for assessing aerosol loading over the Sea. However, agreement between aerosol properties inferred from measurements from different instruments, and even in some cases from the same measurements using different retrieval algorithms can be poor, particularly in the case of mineral dust. Ground based measurements which can be used to evaluate retrievals are thus highly desirable. Here we take advantage of ship-based sun-photometer micro-tops observations gathered from a series of cruises which took place across the Red Sea during 2011 and 2013. To our knowledge these data represent the first set of detailed aerosol measurements from the Sea. They thus provide a unique opportunity to assess the performance of satellite retrieval algorithms in this region. Initially two aerosol optical depth (AOD) retrieval algorithms developed for the MODerate Resolution Imaging Spectroradiometer (MODIS) and Spinning Enhanced Visible and InfraRed Imager (SEVIRI) instruments are evaluated via comparison with the co-located cruise observations. These show excellent agreement, with correlations typically better than 0.9 and very small root-mean-square and bias differences. Calculations of radiative fluxes and DRF along one of the cruises using the observed aerosol and meteorological conditions also show good agreement with co-located estimates from the Geostationary Earth Radiation Budget (GERB) instrument if the aerosol asymmetry parameter is adjusted to account for the presence of large

  11. The impacts of optical properties on radiative forcing due to dust aerosol

    NASA Astrophysics Data System (ADS)

    Wang, H.; Shi, G. Y.; Li, S. Y.; Li, W.; Wang, B.; Huang, Y. B.

    2006-05-01

    There are large uncertainties in the quantitative assessment of radiative effects due to atmospheric dust aerosol. The optical properties contribute much to those uncertainties. The authors perform several sensitivity experiments to estimate the impacts of optical characteristics on regional radiative forcing in this paper. The experiments involve in refractive indices, single scattering albedo, asymmetry factor and optical depth. An updated dataset of refractive indices representing East Asian dust and the one recommended by the World Meteorology Organization (WMO) are contrastively analyzed and used. A radiative transfer code for solar and thermal infrared radiation with detailed aerosol parameterization is employed. The strongest emphasis is on the refractive indices since other optical parameters strongly depend on it, and the authors found a strong sensitivity of radiative forcing on refractive indices. Studies show stronger scattering, weaker absorption and forward scattering of the East Asian dust particles at solar wavelengths, which leads to higher negative forcing, lower positive forcing and bigger net forcing at the top of the atmosphere (TOA) than that of the WMO dust model. It is also found that the TOA forcings resulting from these two dust models have opposite signs in certain regions, which implies the importance of accurate measurements of optical properties in the quantitative estimation of radiative forcing.

  12. Long term characterization of aerosol optical properties: Implications for radiative forcing over the desert region of Jodhpur, India

    NASA Astrophysics Data System (ADS)

    Bhaskar, V. Vizaya; Safai, P. D.; Raju, M. P.

    2015-08-01

    AOT data for eight years period (2004-2012) using the MICROTOPS II Sun photometer has been used to study the wavelength dependent optical characteristics of aerosols over Jodhpur, situated in the desert region in NW India. The daily mean AOT at 500 nm for the present study period was 0.66 ± 0.14 with an average Angstrom exponent as 0.71 ± 0.20. Linear regression analysis of monthly AOT and Angstrom Exponent indicated an increasing trend of both. Seasonal variations of daily AOT and α as well as spectral dependence of seasonal mean AOT are presented. Diurnal variation of AOT and α in different season is studied. Impact of dust storm events on the aerosol characteristics over Jodhpur during the study period is studied. AOT values derived from MICROTOPS II were cross checked with Sun Sky Radiometer (Model POM-01, Prede Inc.) data for the period from May 2011 to April 2012 and were found to be in good agreement. Short wave aerosol radiative forcing (ARF) was computed for one year period of May 2011 to April 2012. Spectral variation of AOT, SSA and ASP showed more AOT and ASP during pre monsoon period when SSA was comparatively low; indicating towards more prevalence of coarse size absorbing dust in this period. The ARF at SUF and TOA was negative during all the seasons indicating dominance of scattering type aerosols mainly dust particles whereas that at ATM was positive in all the seasons indicating heating of the atmosphere, especially more during pre monsoon (+40.5 W/m2) than during rest of the year (+19.5 W/m2). A high degree of correlation between ARF at the SUF with AOT (R2 = 0.94) indicated that ARF is a strong function of AOT. The radiative forcing efficiency inferred to scattering nature of aerosols at SUF (-4.2 W/m2/AOD) and TOA (-63.2 W/m2/AOD) indicating cooling at surface and top of the atmosphere whereas, there was warming of the atmosphere in between (+59 W/m2/AOD). The atmospheric heating rates varied from 0.49 K/day in post monsoon to 1.13 K/day in

  13. Coefficients of an analytical aerosol forcing equation determined with a Monte-Carlo radiation model

    NASA Astrophysics Data System (ADS)

    Hassan, Taufiq; Moosmüller, H.; Chung, Chul E.

    2015-10-01

    Simple analytical equations for global-average direct aerosol radiative forcing are useful to quickly estimate aerosol forcing changes as function of key atmosphere, surface and aerosol parameters. The surface and atmosphere parameters in these analytical equations are the globally uniform atmospheric transmittance and surface albedo, and have so far been estimated from simplified observations under untested assumptions. In the present study, we take the state-of-the-art analytical equation and write the aerosol forcing as a linear function of the single scattering albedo (SSA) and replace the average upscatter fraction with the asymmetry parameter (ASY). Then we determine the surface and atmosphere parameter values of this equation using the output from the global MACR (Monte-Carlo Aerosol Cloud Radiation) model, as well as testing the validity of the equation. The MACR model incorporated spatio-temporally varying observations for surface albedo, cloud optical depth, water vapor, stratosphere column ozone, etc., instead of assuming as in the analytical equation that the atmosphere and surface parameters are globally uniform, and should thus be viewed as providing realistic radiation simulations. The modified analytical equation needs globally uniform aerosol parameters that consist of AOD (Aerosol Optical Depth), SSA, and ASY. The MACR model is run here with the same globally uniform aerosol parameters. The MACR model is also run without cloud to test the cloud effect. In both cloudy and cloud-free runs, the equation fits in the model output well whether SSA or ASY varies. This means the equation is an excellent approximation for the atmospheric radiation. On the other hand, the determined parameter values are somewhat realistic for the cloud-free runs but unrealistic for the cloudy runs. The global atmospheric transmittance, one of the determined parameters, is found to be around 0.74 in case of the cloud-free conditions and around 1.03 with cloud. The surface

  14. Influence of Brown Carbon Aerosols on Absorption Enhancement and Radiative Forcing

    NASA Astrophysics Data System (ADS)

    Shamjad, Puthukkadan; Nand Tripathi, Sachchida; Kant Pathak, Ravi; Hallquist, Mattias

    2015-04-01

    This study presents aerosol mass and optical properties measured during winter-spring months (February-March) of two consecutive years (2013-2014) from Kanpur, India located inside Gangetic Plain. Spectral absorption and scattering coefficients (405, 532 and 781 nm) of both atmospheric and denuded (at 300° C) is measured using a 3 wavelength Photo Acoustic Soot Spectrometer (PASS 3). Ratio between the atmospheric and denuded absorption is reported as enhancement in absorption (Eabs). Eabs values shows presence of large quantities of Brown Carbon (BrC) aerosols in the location. Diurnal trend of Eabs shows similar patterns at 405 and 532 nm. But at 781 nm Eabs values increased during day time (10:00 to 18:00) while that 405 and 532 nm decreased. Positive Matrix Analysis (PMF) of organic aerosols measured using HR-ToF-AMS shows factors with different trends with total absorption. Semi-volatile factor (SV-OOA) show no correlation with absorption but other factors such as Low-volatile (LV-OOA), Hydrocarbon (HOA) and Biomass burning (BBOA) organic aerosols shows a positive trend. All factors shows good correlation with scattering coefficient. Also a strong dependence of absorption is observed at 405 and 532 nm and a weak dependence at 781 nm is observed during regression analysis with factors and mass loading. We also present direct radiative forcing (DRF) calculated from measured optical properties due to total aerosol loading and only due to BrC. Total and BrC aerosol DRF shows cooling trends at top of atmosphere (TOA) and surface and warming trend in atmosphere. Days with biomass burning events shows increase in magnitude of DRF at atmosphere and surface up to 30 % corresponding to clear days. TOA forcing during biomass burning days shows increase in magnitude indicating change from negative to less negative.

  15. Challenges in constraining anthropogenic aerosol effects on cloud radiative forcing using present-day spatiotemporal variability

    PubMed Central

    Ghan, Steven; Wang, Minghuai; Zhang, Shipeng; Ferrachat, Sylvaine; Gettelman, Andrew; Griesfeller, Jan; Kipling, Zak; Lohmann, Ulrike; Morrison, Hugh; Neubauer, David; Partridge, Daniel G.; Stier, Philip; Takemura, Toshihiko; Wang, Hailong; Zhang, Kai

    2016-01-01

    A large number of processes are involved in the chain from emissions of aerosol precursor gases and primary particles to impacts on cloud radiative forcing. Those processes are manifest in a number of relationships that can be expressed as factors dlnX/dlnY driving aerosol effects on cloud radiative forcing. These factors include the relationships between cloud condensation nuclei (CCN) concentration and emissions, droplet number and CCN concentration, cloud fraction and droplet number, cloud optical depth and droplet number, and cloud radiative forcing and cloud optical depth. The relationship between cloud optical depth and droplet number can be further decomposed into the sum of two terms involving the relationship of droplet effective radius and cloud liquid water path with droplet number. These relationships can be constrained using observations of recent spatial and temporal variability of these quantities. However, we are most interested in the radiative forcing since the preindustrial era. Because few relevant measurements are available from that era, relationships from recent variability have been assumed to be applicable to the preindustrial to present-day change. Our analysis of Aerosol Comparisons between Observations and Models (AeroCom) model simulations suggests that estimates of relationships from recent variability are poor constraints on relationships from anthropogenic change for some terms, with even the sign of some relationships differing in many regions. Proxies connecting recent spatial/temporal variability to anthropogenic change, or sustained measurements in regions where emissions have changed, are needed to constrain estimates of anthropogenic aerosol impacts on cloud radiative forcing. PMID:26921324

  16. Challenges in constraining anthropogenic aerosol effects on cloud radiative forcing using present-day spatiotemporal variability.

    PubMed

    Ghan, Steven; Wang, Minghuai; Zhang, Shipeng; Ferrachat, Sylvaine; Gettelman, Andrew; Griesfeller, Jan; Kipling, Zak; Lohmann, Ulrike; Morrison, Hugh; Neubauer, David; Partridge, Daniel G; Stier, Philip; Takemura, Toshihiko; Wang, Hailong; Zhang, Kai

    2016-05-24

    A large number of processes are involved in the chain from emissions of aerosol precursor gases and primary particles to impacts on cloud radiative forcing. Those processes are manifest in a number of relationships that can be expressed as factors dlnX/dlnY driving aerosol effects on cloud radiative forcing. These factors include the relationships between cloud condensation nuclei (CCN) concentration and emissions, droplet number and CCN concentration, cloud fraction and droplet number, cloud optical depth and droplet number, and cloud radiative forcing and cloud optical depth. The relationship between cloud optical depth and droplet number can be further decomposed into the sum of two terms involving the relationship of droplet effective radius and cloud liquid water path with droplet number. These relationships can be constrained using observations of recent spatial and temporal variability of these quantities. However, we are most interested in the radiative forcing since the preindustrial era. Because few relevant measurements are available from that era, relationships from recent variability have been assumed to be applicable to the preindustrial to present-day change. Our analysis of Aerosol Comparisons between Observations and Models (AeroCom) model simulations suggests that estimates of relationships from recent variability are poor constraints on relationships from anthropogenic change for some terms, with even the sign of some relationships differing in many regions. Proxies connecting recent spatial/temporal variability to anthropogenic change, or sustained measurements in regions where emissions have changed, are needed to constrain estimates of anthropogenic aerosol impacts on cloud radiative forcing. PMID:26921324

  17. Decadal Changes in Arctic Radiative Forcing from Aerosols and Tropospheric Ozone

    NASA Astrophysics Data System (ADS)

    Breider, T. J.; Mickley, L. J.; Jacob, D. J.; Payer Sulprizio, M.; Croft, B.; Ridley, D. A.; Ge, C.; Yang, Q.; Bitz, C. M.; McConnell, J.; Sharma, S.; Skov, H.; Eleftheriadis, K.

    2014-12-01

    Annual average Arctic sea ice coverage has declined by 3.6% per decade since the 1980s, but factors driving this trend are uncertain. Long-term surface observations and ice core records suggest recent, large declines in the Arctic atmospheric burden of sulfate aerosol, which may account in part for the warming trend. The decline in black carbon (BC) aerosol in the Arctic during the same period may partly offset the warming due to decreases in sulfate. Here we use the GEOS-Chem chemical transport model together with a detailed inventory of historical anthropogenic trace gas and primary aerosol emissions to quantify changes in Arctic radiative forcing from tropospheric ozone and aerosol between 1980 and 2010. Previous studies have reported an increasing trend in observed ozone at 500 hPa over Canada, but our simulation shows no significant trend. Over Europe, good agreement is found with observed long-term trends in sulfate in surface air (observed = -0.14±0.02 μg m-3 yr-1, model = -0.13±0.01 μg m-3 yr-1), while the observed trend in sulfate in precipitation (-0.20±0.03 μg m-3 yr-1) is underestimated by 40%. At Alert, the timing of the observed decline in sulfate after 1991 is well captured in the simulation, but the observed trend between 1991 and 2001 (-36.3±4.1 ng m-3 yr-1) is underestimated by 26%. BC observations at remote Arctic surface stations are biased low throughout 1980-2010 by a factor of 2. At Greenland ice cores, observed 1980-2010 trends in sulfate deposition are underestimated by 35%. The smaller model bias in observed sulfate and BC deposition at ice cores in southern Greenland (5% and 65%) compared to northern Greenland (56% and 90%) indicates greater uncertainty in pollution emissions from Eurasian sources. We estimate a surface radiative forcing from atmospheric aerosols in the Arctic during 2008 of -0.51 W m-2. The forcing is largest in spring (-1.36 W m-2) and dominated by sulfate aerosol (87%). We will quantify the contributions to the

  18. Radiative Forcing of the Direct Aerosol Effect from AeroCom Phase II Simulations

    NASA Technical Reports Server (NTRS)

    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

  19. Radiative forcing of the direct aerosol effect from AeroCom Phase II simulations

    SciTech Connect

    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.; Kirkevåg, A.; Lamarque, J. -F.; Lin, G.; Liu, X.; Lund, M. T.; Luo, G.; Ma, X.; van Noije, T.; Penner, J. E.; Rasch, P. J.; Ruiz, A.; Seland, Ø.; 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 Wm-2, with a mean of -0.27 Wm-2 for the 16 models. Several models did not include nitrate or SOA and modifying the estimate by accounting for this with information from the other AeroCom models reduces the range and 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 Wm-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.

  20. Radiative Forcing, Satellite Validation, and Thermodynamic Impact of Aerosols during Aerose Campaigns

    NASA Astrophysics Data System (ADS)

    Flores, A.; Joseph, E.; Nalli, N. R.; Smirnov, A.; Morris, V. R.; Wolfe, D. E.; Aerose Team

    2011-12-01

    An estimated three billion metric tons of mineral aerosols are injected into the troposphere annually from the Saharan desert [Prospero et al., 1996]. These windswept aerosols from the African continent are responsible for a variety of climate, health, and environmental impacts on both global and regional scales that span the Western Hemisphere [Morris et al., 2006]. The Aerosol and Ocean Science Expeditions (AEROSE) are a great opportunity to tackle these impacts. The Saharan Air Layer (SAL) appears to retain its Saharan characteristics of warm, stable air near its base, and dryness and dustiness throughout its depth as it is carried as far as the western Caribbean Sea [Dunion & Velden, 2004]. AEROSE provides insitu characterization of the impact of aerosols of African origin on energy balance and microphysical evolution of mineral dust outflow over the tropical Atlantic Ocean. By quantifying the radiative properties of the SAL, aerosol optical depths (AOD) as high as 1.6 was detected over the Atlantic [Nalli et al., 2011], producing a shortwave forcing of 200 W/m2 and therefore a warming just above the marine boundary layer for this particular case. Also in this study, AOD values from AEROSE have been compared with the Moderate Resolution Imaging Spectroradiometer (MODIS), showing variety on each campaign.

  1. What are the driving forces behind the predicted elevated Ammonium-Nitrate Aerosol Concentrations in 2030?

    NASA Astrophysics Data System (ADS)

    Bauer, S. E.; Koch, D.; Metzger, S.; Unger, N.

    2006-12-01

    The formation of Ammonium - Nitrate Aerosols depends on a number of precursor species, most importantly gaseous ammonia and nitric acid, and on the thermodynamic state of the atmospheric system as it competes for ammonia with Ammonium-Sulfate formation. However, because Ammonium-Nitrate formation is very sensitive to future emission and climate change this paper investigates which of these future changes are responsible for the predicted elevated nitrate concentrations in about 25 years from now. We use the GISS climate model, fully coupled to aerosol and gas phase chemistry modules and the SRES A1B emissions for 2030. Our results show that Ammonium-Nitrate Aerosols would increase globally by 40% compared to 1990 conditions. Nitrate Aerosols increase everywhere but most strongly over China. Looking into the separate processes, physical climate change (e.g. increased Temperature and Humidity) have only a small impact, changes in NOx and SO2 emissions still have week impacts, whereas increased NH3 emissions are the driving force behind future nitrate concentrations. However, the model results are extremely sensitive to heterogeneous processes on mineral dust surfaces. For example Ammonium-Nitrate formation depends strongly on the mixing state of sulfate aerosols, wether the sulfate is externally mixed or attached to mineral dust.

  2. The Impact of Desert Dust Aerosol Radiative Forcing on Global and West African Precipitation

    NASA Astrophysics Data System (ADS)

    Jordan, A.; Zaitchik, B. F.; Gnanadesikan, A.; Dezfuli, A. K.

    2015-12-01

    Desert dust aerosols exert a radiative forcing on the atmosphere, influencing atmospheric temperature structure and modifying radiative fluxes at the top of the atmosphere (TOA) and surface. As dust aerosols perturb radiative fluxes, the atmosphere responds by altering both energy and moisture dynamics, with potentially significant impacts on regional and global precipitation. Global Climate Model (GCM) experiments designed to characterize these processes have yielded a wide range of results, owing to both the complex nature of the system and diverse differences across models. Most model results show a general decrease in global precipitation, but regional results vary. Here, we compare simulations from GFDL's CM2Mc GCM with multiple other model experiments from the literature in order to investigate mechanisms of radiative impact and reasons for GCM differences on a global and regional scale. We focus on West Africa, a region of high interannual rainfall variability that is a source of dust and that neighbors major Sahara Desert dust sources. As such, changes in West African climate due to radiative forcing of desert dust aerosol have serious implications for desertification feedbacks. Our CM2Mc results show net cooling of the planet at TOA and surface, net warming of the atmosphere, and significant increases in precipitation over West Africa during the summer rainy season. These results differ from some previous GCM studies, prompting comparative analysis of desert dust parameters across models. This presentation will offer quantitative analysis of differences in dust aerosol parameters, aerosol optical properties, and overall particle burden across GCMs, and will characterize the contribution of model differences to the uncertainty of forcing and climate response affecting West Africa.

  3. Impact of springtime biomass-burning aerosols on radiative forcing over northern Thailand during the 7SEAS campaign

    NASA Astrophysics Data System (ADS)

    Pani, Shantanu Kumar; Wang, Sheng-Hsiang; Lin, Neng-Huei; Lee, Chung-Te; Tsay, Si-Chee; Holben, Brent; Janjai, Serm; Hsiao, Ta-Chih; Chuang, Ming-Tung; Chantara, Somporn

    2016-04-01

    dominate the both surface mass concentration and the columnar burden. The BC contributed only 6% to the aerosol mass loading, but its contribution to the total AOD and net atmospheric forcing were 12% and 75%, respectively. The mean radiative forcing was -6.8 to -8.7 W m-2 at the top-of-atmosphere and -28 to -33 W m-2 at surface. Furthermore BC aerosols contributed 45-49% to the surface radiative forcing along with the water soluble aerosols (49-52%), thus, significantly contributing to solar dimming

  4. Large Aerosol Radiative Forcing due to the 1997 Indonesian Forest Fire

    NASA Astrophysics Data System (ADS)

    Podgorny, I. A.; Li, F.; Ramanathan, V.

    2003-01-01

    During the last decade, the feedback between El Niño and biomass burning caused the Indonesia's forest fire aerosols to be the second most significant source of anthropogenic aerosol over the tropical Indian Ocean after the South Asian Haze. In this paper, the estimates of the radiative forcing during the 1997 Indonesia's forest fire have been obtained by integrating satellite derived aerosol optical depths and cloud cover with in-situ observations of single scattering albedo and a Monte-Carlo Aerosol-Cloud radiation model. The haze reduced the seasonal average solar radiation absorbed by the equatorial Indian ocean by as much as 30 to 60 W m-2 during September to November 1997, and increased the atmospheric solar heating by as much as 50% to 100% within the first 3 kilometers. The radiative forcing at the top of the atmosphere (TOA) was in the range of 5 to 15 W m-2 under cloudy skies. The significance of such large radiative flux changes to the tropical ocean-atmosphere heat budget and climate needs to be examined with climate models.

  5. Aerosol Radiative Effects on Deep Convective Clouds and Associated Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Fan, J.; Zhang, R.; Tao, W.-K.; Mohr, I.

    2007-01-01

    The aerosol radiative effects (ARE) on the deep convective clouds are investigated by using a spectral-bin cloud-resolving model (CRM) coupled with a radiation scheme and an explicit land surface model. The sensitivity of cloud properties and the associated radiative forcing to aerosol single-scattering albedo (SSA) are examined. The ARE on cloud properties is pronounced for mid-visible SSA of 0.85. Relative to the case excluding the ARE, cloud fraction and optical depth decrease by about 18% and 20%, respectively. Cloud droplet and ice particle number concentrations, liquid water path (LWP), ice water path (IWP), and droplet size decrease significantly when the ARE is introduced. The ARE causes a surface cooling of about 0.35 K and significantly high heating rates in the lower troposphere (about 0.6K/day higher at 2 km), both of which lead to a more stable atmosphere and hence weaker convection. The weaker convection and the more desiccation of cloud layers explain the less cloudiness, lower cloud optical depth, LWP and IWP, smaller droplet size, and less precipitation. The daytime-mean direct forcing induced by black carbon is about 2.2 W/sq m at the top of atmosphere (TOA) and -17.4 W/sq m at the surface for SSA of 0.85. The semi-direct forcing is positive, about 10 and 11.2 W/sq m at the TOA and surface, respectively. Both the TOA and surface total radiative forcing values are strongly negative for the deep convective clouds, attributed mostly to aerosol indirect forcing. Aerosol direct and semi-direct effects are very sensitive to SSA. Because the positive semi-direct forcing compensates the negative direct forcing at the surface, the surface temperature and heat fluxes decrease less significantly with the increase of aerosol absorption (decreasing SSA). The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable and dryer atmosphere due to enhanced surface cooling and

  6. A simple method for estimation of coagulation efficiency in mixed aerosols. [environmental pollution control

    NASA Technical Reports Server (NTRS)

    Dimmick, R. L.; Boyd, A.; Wolochow, H.

    1975-01-01

    Aerosols of KBr and AgNO3 were mixed, exposed to light in a glass tube and collected in the dark. About 15% of the collected material was reduced to silver upon development. Thus, two aerosols of particles that react to form a photo-reducible compound can be used to measure coagulation efficiency.

  7. Influence of aerosols on surface reaching spectral irradiance and introduction to a new technique of estimating aerosol radiative forcing from high resolution spectral flux measurements

    NASA Astrophysics Data System (ADS)

    Rao, Roshan

    2016-04-01

    Aerosol radiative forcing estimates with high certainty are required in climate change studies. The approach in estimating the aerosol radiative forcing by using the chemical composition of aerosols is not effective as the chemical composition data with radiative properties are not widely available. We look into the approach where ground based spectral radiation flux measurement is made and along with an Radtiative transfer (RT) model, radiative forcing is estimated. Measurements of spectral flux were made using an ASD spectroradiometer with 350 - 1050 nm wavelength range and a 3nm resolution during around 54 clear-sky days during which AOD range was around 0.01 to 0.7. Simultaneous measurements of black carbon were also made using Aethalometer (Magee Scientific) which ranged from around 1.5 ug/m3 to 8 ug/m3. The primary study involved in understanding the sensitivity of spectral flux due to change in individual aerosol species (Optical properties of Aerosols and Clouds (OPAC) classified aerosol species) using the SBDART RT model. This made us clearly distinguish the influence of different aerosol species on the spectral flux. Following this, a new technique has been introduced to estimate an optically equivalent mixture of aerosol species for the given location. The new method involves matching different combinations of aerosol species in OPAC model and RT model as long as the combination which gives the minimum root mean squared deviation from measured spectral flux is obtained. Using the optically equivalent aerosol mixture and RT model, aerosol radiative forcing is estimated. Also an alternate method to estimate the spectral SSA is discussed. Here, the RT model, the observed spectral flux and spectral AOD is used. Spectral AOD is input to RT model and SSA is varied till the minimum root mean squared difference between observed and simulated spectral flux from RT model is obtained. The methods discussed are limited to clear sky scenes and its accuracy to derive

  8. Influence of aerosols on surface reaching spectral irradiance and introduction to a new technique for estimating aerosol radiative forcing from spectral flux measurements

    NASA Astrophysics Data System (ADS)

    Rao, R. R.

    2015-12-01

    Aerosol radiative forcing estimates with high certainty are required in climate change studies. The approach in estimating the aerosol radiative forcing by using the chemical composition of aerosols is not effective as the chemical composition data with radiative properties are not widely available. In this study we look into the approach where ground based spectral radiation flux measurements along with an RT model is used to estimate radiative forcing. Measurements of spectral flux were made using an ASD spectroradiometer with 350 - 1050 nm wavelength range and 3nm resolution for around 54 clear-sky days during which AOD range was around 0.1 to 0.7. Simultaneous measurements of black carbon were also made using Aethalometer (Magee Scientific) which ranged from around 1.5 ug/m3 to 8 ug/m3. All the measurements were made in the campus of Indian Institute of Science which is in the heart of Bangalore city. The primary study involved in understanding the sensitivity of spectral flux to change in the mass concentration of individual aerosol species (Optical properties of Aerosols and Clouds -OPAC classified aerosol species) using the SBDART RT model. This made us clearly distinguish the region of influence of different aerosol species on the spectral flux. Following this, a new technique has been introduced to estimate an optically equivalent mixture of aerosol species for the given location. The new method involves an iterative process where the mixture of aerosol species are changed in OPAC model and RT model is run as long as the mixture which mimics the measured spectral flux within 2-3% deviation from measured spectral flux is obtained. Using the optically equivalent aerosol mixture and RT model aerosol radiative forcing is estimated. The new method is limited to clear sky scenes and its accuracy to derive an optically equivalent aerosol mixture reduces when diffuse component of flux increases. Our analysis also showed that direct component of spectral flux is

  9. Effect of spectrally varying albedo of vegetation surfaces on shortwave radiation fluxes and direct aerosol forcing

    NASA Astrophysics Data System (ADS)

    Zhu, L.; Martins, J. V.; Yu, H.

    2012-06-01

    This study develops an algorithm for the representation of large spectral variations of albedo over vegetation surfaces based on Moderate Resolution Imaging Spectrometer (MODIS) observations at 7 discrete channels centered at 0.47, 0.55, 0.67, 0.86, 1.24, 1.63, and 2.11 μm. The MODIS 7-channel observations miss several major features of vegetation albedo including the vegetation red edge near 0.7 μm and vegetation absorption features at 1.48 and 1.92 μm. We characterize these features by investigating aerosol forcing in different spectral ranges. We show that the correction at 0.7 μm is the most sensitive and important due to the presence of the red edge and strong solar radiation; the other two corrections are less sensitive due to the weaker solar radiation and strong atmospheric water absorption. Four traditional approaches for estimating the reflectance spectrum and the MODIS enhanced vegetation albedo (MEVA) are tested against various vegetation types: dry grass, green grass, conifer, and deciduous from the John Hopkins University (JHU) spectral library; aspens from the US Geological Survey (USGS) digital spectral library; and Amazon vegetation types. Compared to traditional approaches, MEVA improves the accuracy of the outgoing flux at the top of the atmosphere by over 60 W m-2 and aerosol forcing by over 10 W m-2. Specifically, for Amazon vegetation types, MEVA can improve the accuracy of daily averaged aerosol forcing at equator at equinox by 3.7 W m-2 (about 70% of the aerosol forcing calculated with high spectral resolution surface reflectance). These improvements indicate that MEVA can contribute to vegetation covered regional climate studies, and help to improve understanding of climate processes and climate change.

  10. Vertical dependence of black carbon, sulphate and biomass burning aerosol radiative forcing

    NASA Astrophysics Data System (ADS)

    Samset, Bjørn H.; Myhre, Gunnar

    2011-12-01

    A global radiative transfer model is used to calculate the vertical profile of shortwave radiative forcing from a prescribed amount of aerosols. We study black carbon (BC), sulphate (SO4) and a black and organic carbon mixture typical of biomass burning (BIO), by prescribing aerosol burdens in layers between 1000 hPa and 20 hPa and calculating the resulting direct radiative forcing divided by the burden (NDRF). We find a strong sensitivity in the NDRF for BC with altitude, with a tenfold increase between BC close to the surface and the lower part of the stratosphere. Clouds are a major contributor to this dependence with altitude, but other factors also contribute. We break down and explain the different physical contributors to this strong sensitivity. The results show a modest regional dependence of the altitudinal dependence of BC NDRF between industrial regions, while for regions with properties deviating from the global mean NDRF variability is significant. Variations due to seasons and interannual changes in cloud conditions are found to be small. We explore the effect that large altitudinal variation in NDRF may have on model estimates of BC radiative forcing when vertical aerosol distributions are insufficiently constrained, and discuss possible applications of the present results for reducing inter-model differences.

  11. Direct shortwave forcing of climate by anthropogenic sulfate aerosol: Sensitivity to particle size, composition, and relative humidity

    SciTech Connect

    Nemesure, S.; Wagener, R.; Schwartz, S.E.

    1996-04-01

    Recent estimates of global or hemispheric average forcing of climate by anthropogenic sulfate aerosol due to scattering of shortwave radiation are uncertain by more than a factor of 2. This paper examines the sensitivity of forcing to these microphysical properties for the purposes of obtaining a better understanding of the properties required to reduce the uncertainty in the forcing.

  12. Identification of aerosol types over Indo-Gangetic Basin: implications to optical properties and associated radiative forcing.

    PubMed

    Tiwari, S; Srivastava, A K; Singh, A K; Singh, Sachchidanand

    2015-08-01

    The aerosols in the Indo-Gangetic Basin (IGB) are a mixture of sulfate, dust, black carbon, and other soluble and insoluble components. It is a challenge not only to identify these various aerosol types, but also to assess the optical and radiative implications of these components. In the present study, appropriate thresholds for fine-mode fraction and single-scattering albedo have been used to first identify the aerosol types over IGB. Four major aerosol types may be identified as polluted dust (PD), polluted continental (PC), black carbon-enriched (BCE), and organic carbon-enriched (OCE). Further, the implications of these different types of aerosols on optical properties and radiative forcing have been studied. The aerosol products derived from CIMEL sun/sky radiometer measurements, deployed under Aerosol Robotic Network program of NASA, USA were used from four different sites Karachi, Lahore, Jaipur, and Kanpur, spread over Pakistan and Northern India. PD is the most dominant aerosol type at Karachi and Jaipur, contributing more than 50% of all the aerosol types. OCE, on the other hand, contributes only about 12-15% at all the stations except at Kanpur where its contribution is ∼38%. The spectral dependence of AOD was relatively low for PD aerosol type, with the lowest AE values (<0.5); whereas, large spectral dependence in AOD was observed for the remaining aerosol types, with the highest AE values (>1.0). SSA was found to be the highest for OCE (>0.9) and the lowest for BCE (<0.9) type aerosols, with drastically different spectral variability. The direct aerosol radiative forcing at the surface and in the atmosphere was found to be the maximum at Lahore among all the four stations in the IGB.

  13. Nonlinear effects of anthropogenic aerosol and urban land surface forcing on spring climate in eastern China

    NASA Astrophysics Data System (ADS)

    Deng, Jiechun; Xu, Haiming; Zhang, Leying

    2016-05-01

    Anthropogenic aerosols and urban land cover change induce opposite thermal effects on the atmosphere near surface as well as in the troposphere. One can think of these anthropogenic effects as composed of two parts: the individual effect due to an individual anthropogenic forcing and the nonlinear effects resulting from the coexistence of two forcing factors. In this study, we explored the role of such nonlinear effects in affecting East Asian climate, as well as individual forcing effects, using the Community Atmosphere Model version 5.1 coupled with the Community Land Model version 4. Atmospheric responses were simulated by including anthropogenic aerosol emission only, urban cover only, or the combination of the two, over eastern China. Results showed that nonlinear responses were different from any effects by an individual forcing or the linear combination of individual responses. The nonlinear interaction could generate cold horizontal temperature advection to cool the troposphere, which induced anomalous subsidence along the Yangtze River Valley (YRV). This anomalous vertical motion, together with a weakened low-level southwesterly, favored below-normal (above-normal) rainfall over the YRV (southern China), shifting the spring rain belt southward. The resultant diabatic cooling, in turn, amplified the anomalous descent and further decreased tropospheric temperature over the YRV, forming a positive feedback loop to maintain the nonlinear effects. Consequently, the nonlinear effects acted to reduce the climate anomalies from a simple linear combination of two individual effects and played an important role in regional responses to one anthropogenic forcing when the other is prescribed.

  14. Current and efficiency optimization under oscillating forces in entropic barriers

    NASA Astrophysics Data System (ADS)

    Nutku, Ferhat; Aydıner, Ekrem

    2016-09-01

    The transport of externally overdriven particles confined in entropic barriers is investigated under various types of oscillating and temporal forces. Temperature, load, and amplitude dependence of the particle current and energy conversion efficiency are investigated in three dimensions. For oscillating forces, the optimized temperature–load, amplitude–temperature, and amplitude–load intervals are determined when fixing the amplitude, load, and temperature, respectively. By using three-dimensional plots rather than two-dimensional ones, it is clearly shown that oscillating forces provide more efficiency compared with a temporal one in specified optimized parameter regions. Furthermore, the dependency of efficiency to the angle between the unbiased driving force and a constant force is investigated and an asymmetric angular dependence is found for all types of forces. Finally, it is shown that oscillating forces with a high amplitude and under a moderate load lead to higher efficiencies than a temporal force at both low and high temperatures for the entire range of contact angle. Project supported by the Istanbul University, Turkey (Grant No. 55383).

  15. Current and efficiency optimization under oscillating forces in entropic barriers

    NASA Astrophysics Data System (ADS)

    Nutku, Ferhat; Aydıner, Ekrem

    2016-09-01

    The transport of externally overdriven particles confined in entropic barriers is investigated under various types of oscillating and temporal forces. Temperature, load, and amplitude dependence of the particle current and energy conversion efficiency are investigated in three dimensions. For oscillating forces, the optimized temperature-load, amplitude-temperature, and amplitude-load intervals are determined when fixing the amplitude, load, and temperature, respectively. By using three-dimensional plots rather than two-dimensional ones, it is clearly shown that oscillating forces provide more efficiency compared with a temporal one in specified optimized parameter regions. Furthermore, the dependency of efficiency to the angle between the unbiased driving force and a constant force is investigated and an asymmetric angular dependence is found for all types of forces. Finally, it is shown that oscillating forces with a high amplitude and under a moderate load lead to higher efficiencies than a temporal force at both low and high temperatures for the entire range of contact angle. Project supported by the Istanbul University, Turkey (Grant No. 55383).

  16. Aerosol Climatology at Pune, Western India: Implications to Direct Radiative Forcing and Heating Rates

    NASA Astrophysics Data System (ADS)

    Pandithurai, G.; Pinker, R. T.; Devara, P. C.; Raj, P. E.; Jayarao, Y.; Dani, K. K.; Maheskumar, R. S.; Sonbawne, S. M.; Saha, S. K.; Bhawar, R.; Shinde, U. P.

    2005-12-01

    Extensive aerosol observations were carried out at Indian Institute of Tropical Meteorology (IITM), Pune, an urban site in the western part of the country, using a Prede (Model POM-01L) sun/sky radiometer and a bi-static Argon ion lidar since December 2000 and October 1986, respectively. The sun/sky radiometer was operated daily at every 15 minute interval during day-time to derive column aerosol optical parameters such as aerosol optical depth (AOD), single scattering albedo (SSA), asymmetry parameter (ASY) while the lidar was operated weekly in the early-night period to derive vertical distributions of aerosol number density. The sun/sky radiance data collected during the above period have been analysed by using the radiative transfer model SkyRadPack version 3.0 (Nakajima et al. 1996) to retrieve AOD, SSA and ASY. AOD and SSA retrieved at 15-minutes interval were averaged to get monthly means. On every year from 2000 to 2005, monthly means of AOD show gradual increase of aerosol loading from December to April and Angstrom exponent decreases from March due to local as well as transported dust from African / Arabian regions through Arabian Sea. Monthly means of SSA show decrease from December to April and the wavelength dependence also indicate the abundance of dust from March to May. Lidar-derived vertical distributions yield minimum during the monsoon months, gradually builds up during the post-monsoon and winter months, and finally peaks during the pre-monsoon months in every year (Devara et al., 2002). The aerosol climatology of optical/radiative parameters and their vertical distribution are used for estimating aerosol radiative forcing (ARF) and atmospheric heating rates by using a discrete-ordinate radiative transfer model (Ricchiazzi et al., 1998, Pandithurai et al. 2004). Details of the experimental methods, data, results of aerosol climatology and implications to radiative forcing and associated heating rates will be presented. References Devara, P

  17. Aerosols, Chemistry, and Radiative Forcing: A 3-D Model Analysis of Satellite and ACE-Asia data (ACMAP)

    NASA Technical Reports Server (NTRS)

    Chin, Mian; Ginoux, Paul; Torres, Omar; Zhao, Xue-Peng

    2005-01-01

    We propose a research project to incorporate a global 3-D model and satellite data into the multi-national Aerosol Characterization Experiment-Asia (ACE-Asia) mission. Our objectives are (1) to understand the physical, chemical, and optical properties of aerosols and the processes that control those properties over the Asian-Pacific region, (2) to investigate the interaction between aerosols and tropospheric chemistry, and (3) to determine the aerosol radiative forcing over the Asia-Pacific region. We will use the Georgia TecWGoddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model to link satellite observations and the ACE-Asia measurements. First, we will use the GOCART model to simulate aerosols and related species, and evaluate the model with satellite and in-situ observations. Second, the model generated aerosol vertical profiles and compositions will be used to validate the satellite products; and the satellite data will be used for during- and post- mission analysis. Third, we will use the model to analyze and interpret both satellite and ACE- Asia field campaign data and investigate the aerosol-chemistry interactions. Finally, we will calculate aerosol radiative forcing over the Asian-Pacific region, and assess the influence of Asian pollution in the global atmosphere. We propose a research project to incorporate a global 3-D model and satellite data into

  18. Future Projections of Aerosol Optical Depth, Radiative Forcing, and Climate Response Due to Declining Aerosol Emissions in the Representative Concentration Pathways

    NASA Astrophysics Data System (ADS)

    Westervelt, D. M.; Mauzerall, D. L.; Horowitz, L. W.; Naik, V.

    2014-12-01

    It is widely expected that global emissions of atmospheric aerosols and their precursors will decrease strongly throughout the remainder of the 21st century, due to emission reduction policies enacted based on human health concerns. However, the resulting decrease in atmospheric aerosol burden will have unintended climate consequences. Since aerosols generally exert a net cooling influence on the climate, their removal will lead to an unmasking of global warming as well as other changes to the climate system. Aerosol and precursor global emissions decrease by as much as 80% by the year 2100, according to projections in four Representative Concentration Pathway (RCP) scenarios. We use the Geophysical Fluid Dynamics Laboratory Climate Model version 3 (GFDL CM3) to simulate future climate over the 21st century with and without aerosol emission changes projected by the RCPs in order to isolate the radiative forcing and climate response due to the aerosol reductions. We find that up to 1 W m-2 of radiative forcing may be unmasked globally by 2100 due to reductions in aerosol and precursor emissions, leading to average global temperature increases up to 1 K and global precipitation rate increases up to 0.09 mm d-1 (3%). Regionally and locally, climate impacts are much larger, as RCP8.5 projects a 2.1 K warming over China, Japan, and Korea due to reduced aerosol emissions. Our results highlight the importance of crafting emissions control policies with both climate and air pollution benefits in mind. The expected unmasking of additional global warming from aerosol reductions highlights the importance of robust greenhouse gas mitigation policies and may require more aggressive policies than anticipated.

  19. Radiative Forcing at the Surface by Clouds, Aerosols, and Water Vapor Over Tropical Oceans

    NASA Astrophysics Data System (ADS)

    Key, E.; Minnett, P.; Szczodrak, G.; Caniaux, G.; Voss, K.; Bourras, D.

    2007-12-01

    Data from recent campaigns conducted in the tropical Atlantic and Indian Oceans provide thorough testbeds for determining the contribution of clouds, aerosols, and water vapor to surface radiative forcing, with particular focus on areas of extreme SST gradients. Oceanographic cruises conducted during the African Monsoon Multidisciplinary Analysis included sampling monsoon onset in the Gulf of Guinea, which was characterized nearshore by rain and haze, the latter being a combination of water vapor and continental and pollution aerosols. Offshore and nearer to the equatorial cold tongue, the ITCZ was the dominant northern hemisphere cloud feature, while drier, cooler air masses existed south of the equator. The R/V Ronald H. Brown, operating a north-south transect along 23 W, encountered both atmospheric tropical wave conditions as well as dry Saharan Air Layers. In the Indian Ocean, the N/O Le Suroit occupied a point station near a positive SST anomaly to observe the onset of convection associated with the MJO and strong diurnal warming signatures. Combining radiative and turbulent flux data with measured and modeled profiles of the marine and atmospheric boundary layer, the evolution and interaction of the total air-sea column is observed. Particular emphasis is placed on the radiative forcing of clouds, aerosols, and water vapor on the sea surface skin temperature, towards the improvement of current diurnal warming models, which simplify atmospheric radiative effects into a general cloud parameter.

  20. How does the synergy between GEO-CAPE and GOES-R improve the retrieval of aerosol properties and the estimate of aerosol radiative forcing?

    NASA Astrophysics Data System (ADS)

    Wang, J.; Zeng, J.; Xu, X.; Spurr, R. J.; Liu, X.

    2011-12-01

    As a geostationary satellite, GEO-CAPE will monitor the same region constantly with same viewing zenith angle; but the change of solar zenith angle during the course of a day provides GEO-CAPE an opportunity to observe the same area at multi-scattering angles. This multi-angle observation from GEO-CAPE can be further combined with similar multi-angle observation from GOES-R, offering the unprecedented opportunity to conduct the retrieval of aerosol properties beyond the aerosol optical depth. In this study, we use the state-of-the-art linearized vector radative transfer model (VLIDORT), linearized Mie code, and linearized T-matrix code in conjunction with inversion theory and HITRAN database to study how the multi-angle synergy between GEO-CAPE and GOES-R can improve the retrieval of aerosol properties and the estimate of aerosol radiative forcing. Our numerical framework is capable to study the degree of freedoms in the aerosol retrieval space for any given set of synthetic or real satellite observation. Our preliminary studies showed that a combined use of GEO-CAPE and GOES-R multi-angle observation can offer unique opportunity to retrieve not only aerosol optical depth but also ~2-3 out of 4 aerosol parameters (e.g., effective radius, effective variance, and refractive index), depending on number of wavelengths and angles used in the retrieval. The retrieved parameter and the corresponding retrieval uncertainty are input into the radiative transfer model to compute the aerosol radiative forcing and estimate the associated uncertainty in the forcing calculations. These results are then compared against another set of forcing calculations that use the current knowledge of satellite-based aerosol parameters and uncertainties as inputs. The comparison is stratified as a function of many confounding parameters (such as surface reflectance, satellite-earth geometry, calibration accuracy) for different air mass types (e.g., urban, rural, or a mixture of both, etc) to

  1. GCM simulations of volcanic aerosol forcing. Part I: Climate changes induced by stead-state perturbations

    SciTech Connect

    Pollack, J.B. ); Rind, D.; Lacis, A.; Hansen, J.E.; Sato, M.; Ruedy, R. )

    1993-09-01

    The Goddard Institute for Space Studies Climate Model II was used to simulate the response of the climate system to a spatially and temporally constant forcing by volcanic aerosols. The climatic changes produced by differencing this simulation and one made for the present climate with no volcanic aerosol forcing. These climatic changes are also compared with those obtained when CO[sub 2] in the atmosphere was doubled and when the boundary conditions associated with the peak of the last ice age. In all three cases, the absolute magnitude of the change in the globally averaged air temperature at the surface is approximately 5K. The simulations imply a significant cooling of the troposphere and surface can occur at times of closely spaced, multiple, sulfur-rich volcanic explosions that span time scales of decades to centuries, such as occurred at the end of the nineteenth and beginning of the twentieth centuries. The steady-state climate response to volcanic forcing includes a expansion of sea ice, especially Southern Hemisphere; a large increase in surface and planetary albedo at high latitudes; and sizable changes in the annually and zonally averaged air temperature. The climate response to three different forcings is similar in 3 ways: direct radiative forcing accounts for 30% and 25% of the total [delta]T[sub s]; Changes in atmospheric water vapor are the most important positive feedback; Albedo feedback is significant, positive at high latitudes. The climate response to the three forcings also differs. The latitudinal profiles of [delta]T[sub s] differ, reflecting significant variations in the latitudinal profiles of the primary radiative forcing. Changes in eddy kinetic energy, heat transport by atmospheric eddies, and total atmospheric heat transport are quite different. These results raise questions about the ease with which atmospheric heat transport can be parameterized in a simple way in energy climate models. 44 refs., 32 figs.

  2. On the Feasibility of Studying Shortwave Aerosol Radiative Forcing of Climate Using Dual-Wavelength Aerosol Backscatter Lidar

    NASA Technical Reports Server (NTRS)

    Redemann, Jens; Russell, Philip B.; Winker, David M.; McCormick, M. Patrick; Hipskind, R. Stephen (Technical Monitor)

    2000-01-01

    The current low confidence in the estimates of aerosol-induced perturbations of Earth's radiation balance is caused by the highly non-uniform compositional, spatial and temporal distributions of tropospheric aerosols on a global scale owing to their heterogeneous sources and short lifetimes. Nevertheless, recent studies have shown that the inclusion of aerosol effects in climate model calculations can improve agreement with observed spatial and temporal temperature distributions. In light of the short lifetimes of aerosols, determination of their global distribution with space-borne sensors seems to be a necessary approach. Until recently, satellite measurements of tropospheric aerosols have been approximate and did not provide the full set of information required to determine their radiative effects. With the advent of active aerosol remote sensing from space (e.g., PICASSO-CENA), the applicability fo lidar-derived aerosol 180 deg -backscatter data to radiative flux calculations and hence studies of aerosol effects on climate needs to be investigated.

  3. Intensification of North American Megadroughts through Surface and Dust Aerosol Forcing

    NASA Technical Reports Server (NTRS)

    Cook, Benjamin I.; Seager, Richard; Miller, Ron L.; Mason, Joseph A

    2013-01-01

    Tree-ring-based reconstructions of the Palmer drought severity index (PDSI) indicate that, during the Medieval Climate Anomaly (MCA), the central plains of North America experienced recurrent periods of drought spanning decades or longer. These megadroughts had exceptional persistence compared to more recent events, but the causes remain uncertain. The authors conducted a suite of general circulation model experiments to test the impact of sea surface temperature (SST) and land surface forcing on the MCA megadroughts over the central plains. The land surface forcing is represented as a set of dune mobilization boundary conditions, derived from available geomorphological evidence and modeled as increased bare soil area and a dust aerosol source (32deg-44degN, 105deg-95degW). In the experiments, cold tropical Pacific SST forcing suppresses precipitation over the central plains but cannot reproduce the overall drying or persistence seen in the PDSI reconstruction. Droughts in the scenario with dust aerosols, however, are amplified and have significantly longer persistence than in other model experiments, more closely matching the reconstructed PDSI. This additional drying occurs because the dust increases the shortwave planetary albedo, reducing energy inputs to the surface and boundary layer. The energy deficit increases atmospheric stability, inhibiting convection and reducing cloud cover and precipitation over the central plains. Results from this study provide the first model-based evidence that dust aerosol forcing and land surface changes could have contributed to the intensity and persistence of the central plains megadroughts, although uncertainties remain in the formulation of the boundary conditions and the future importance of these feedbacks.

  4. Multi-site characterization of tropical aerosols: Implications for regional radiative forcing

    NASA Astrophysics Data System (ADS)

    Sumit, Kumar; Devara, P. C. S.; Manoj, M. G.

    2012-03-01

    A land campaign, as a part of the Indian Space Research Organization-Geosphere Biosphere Program (ISRO-GBP), has been organized using a suit of instruments like AERONET (Aerosol Robotic Network) Sun/Sky sunphotometer, Microtops-II (MICROprocessor-controlled Total Ozone Portable Spectrometer), short-wave pyranometer from December 1, 2006 to April 30, 2007, over five locations (Ahmedabad, Pune, Sinhgad, Trivandrum and Gadanki) representing different environments. The dominance of different aerosol types such as biomass burning, urban/industrial pollution, marine origin and desert-dust particles is expected at these five sites. In all locations, significant day-to-day variability in AOD and Ångström exponent is observed. The Ångström exponent exhibits its lowest values over semi-arid region (Ahmedabad) 0.4-0.7, while it is around 1.8 at rural site (Gadanki). The retrieved volume size distributions for Pune, Ahmedabad and Trivandrum are found to be bimodal with varying concentration of each mode. Interesting feature of this observation is, very low coarse-mode volume concentration observed at Trivandrum even though observations were made about 300 m from the coast. The synergy of results from these complementary measurements is reflected in the computed regional aerosol radiative forcing and heating rates. We have used a radiative transfer model (SBDART) to examine the variations of aerosol direct radiative effect (ADRE) and heating rates to give an overall estimation of the effect on climate. The ADRE, over different measurement sites, at short wavelength is found to be negative at the surface in the range of - 18 to - 59 W m - 2 , and TOA forcing values varied from + 0.9 to - 8 W m - 2 .

  5. The Impact of Pre-Industrial Land Use Change on Atmospheric Composition and Aerosol Radiative Forcing.

    NASA Astrophysics Data System (ADS)

    Hamilton, D. S.; Carslaw, K. S.; Spracklen, D. V.; Folberth, G.; Kaplan, J. O.; Pringle, K.; Scott, C.

    2015-12-01

    Anthropogenic land use change (LUC) has had a major impact on the climate by altering the amount of carbon stored in vegetation, changing surface albedo and modifying the levels of both biogenic and pyrogenic emissions. While previous studies of LUC have largely focused on the first two components, there has recently been a recognition that changes to aerosol and related pre-cursor gas emissions from LUC are equally important. Furthermore, it has also recently been recognised that the pre-industrial (PI) to present day (PD) radiative forcing (RF) of climate from aerosol cloud interactions (ACI) due to anthropogenic emissions is highly sensitive to the amount of natural aerosol that was present in the PI. This suggests that anthropogenic RF from ACI may be highly sensitive to land-use in the PI. There are currently two commonly used baseline reference years for the PI; 1750 and 1860. Rapid LUC occurred between 1750 and 1860, with large reductions in natural vegetation cover in Eastern Northern America, Europe, Central Russia, India and Eastern China as well as lower reductions in parts of Brazil and Africa. This LUC will have led to significant changes in biogenic and fire emissions with implications for natural aerosol concentrations and PI-to-PD RF. The focus of this study is therefore to quantify the impact of LUC between 1750 and 1860 on aerosol concentrations and PI-to-PD RF calculations from ACI. We use the UK Met Office HadGEM3-UKCA coupled-chemistry-climate model to calculate the impacts of anthropogenic emissions and anthropogenic LUC on aerosol size distributions in both 1750 and 1860. We prescribe LUC using the KK10 historical dataset of land cover change. Monoterpene emissions are coupled directly to the prescribed LUC through the JULES land surface scheme in HadGEM3. Fire emissions from LUC were calculated offline using the fire module LPJ-LMfire in the Lund-Potsdam-Jena dynamic global vegetation model. To separate out the impacts of LUC from

  6. Biomechanics of Forearm Rotation: Force and Efficiency of Pronator Teres

    PubMed Central

    Ibáñez-Gimeno, Pere; Galtés, Ignasi; Jordana, Xavier; Malgosa, Assumpció; Manyosa, Joan

    2014-01-01

    Biomechanical models are useful to assess the effect of muscular forces on bone structure. Using skeletal remains, we analyze pronator teres rotational efficiency and its force components throughout the entire flexion-extension and pronation-supination ranges by means of a new biomechanical model and 3D imaging techniques, and we explore the relationship between these parameters and skeletal structure. The results show that maximal efficiency is the highest in full elbow flexion and is close to forearm neutral position for each elbow angle. The vertical component of pronator teres force is the highest among all components and is greater in pronation and elbow extension. The radial component becomes negative in pronation and reaches lower values as the elbow flexes. Both components could enhance radial curvature, especially in pronation. The model also enables to calculate efficiency and force components simulating changes in osteometric parameters. An increase of radial curvature improves efficiency and displaces the position where the radial component becomes negative towards the end of pronation. A more proximal location of pronator teres radial enthesis and a larger humeral medial epicondyle increase efficiency and displace the position where this component becomes negative towards forearm neutral position, which enhances radial curvature. Efficiency is also affected by medial epicondylar orientation and carrying angle. Moreover, reaching an object and bringing it close to the face in a close-to-neutral position improve efficiency and entail an equilibrium between the forces affecting the elbow joint stability. When the upper-limb skeleton is used in positions of low efficiency, implying unbalanced force components, it undergoes plastic changes, which improve these parameters. These findings are useful for studies on ergonomics and orthopaedics, and the model could also be applied to fossil primates in order to infer their locomotor form. Moreover, activity

  7. Regional Influence of Aerosol Emissions from Wildfires Driven by Combustion Efficiency: Insights from the BBOP Campaign.

    PubMed

    Collier, Sonya; Zhou, Shan; Onasch, Timothy B; Jaffe, Daniel A; Kleinman, Lawrence; Sedlacek, Arthur J; Briggs, Nicole L; Hee, Jonathan; Fortner, Edward; Shilling, John E; Worsnop, Douglas; Yokelson, Robert J; Parworth, Caroline; Ge, Xinlei; Xu, Jianzhong; Butterfield, Zachary; Chand, Duli; Dubey, Manvendra K; Pekour, Mikhail S; Springston, Stephen; Zhang, Qi

    2016-08-16

    Wildfires are important contributors to atmospheric aerosols and a large source of emissions that impact regional air quality and global climate. In this study, the regional and nearfield influences of wildfire emissions on ambient aerosol concentration and chemical properties in the Pacific Northwest region of the United States were studied using real-time measurements from a fixed ground site located in Central Oregon at the Mt. Bachelor Observatory (∼2700 m a.s.l.) as well as near their sources using an aircraft. The regional characteristics of biomass burning aerosols were found to depend strongly on the modified combustion efficiency (MCE), an index of the combustion processes of a fire. Organic aerosol emissions had negative correlations with MCE, whereas the oxidation state of organic aerosol increased with MCE and plume aging. The relationships between the aerosol properties and MCE were consistent between fresh emissions (∼1 h old) and emissions sampled after atmospheric transport (6-45 h), suggesting that biomass burning organic aerosol concentration and chemical properties were strongly influenced by combustion processes at the source and conserved to a significant extent during regional transport. These results suggest that MCE can be a useful metric for describing aerosol properties of wildfire emissions and their impacts on regional air quality and global climate.

  8. Regional Influence of Aerosol Emissions from Wildfires Driven by Combustion Efficiency: Insights from the BBOP Campaign.

    PubMed

    Collier, Sonya; Zhou, Shan; Onasch, Timothy B; Jaffe, Daniel A; Kleinman, Lawrence; Sedlacek, Arthur J; Briggs, Nicole L; Hee, Jonathan; Fortner, Edward; Shilling, John E; Worsnop, Douglas; Yokelson, Robert J; Parworth, Caroline; Ge, Xinlei; Xu, Jianzhong; Butterfield, Zachary; Chand, Duli; Dubey, Manvendra K; Pekour, Mikhail S; Springston, Stephen; Zhang, Qi

    2016-08-16

    Wildfires are important contributors to atmospheric aerosols and a large source of emissions that impact regional air quality and global climate. In this study, the regional and nearfield influences of wildfire emissions on ambient aerosol concentration and chemical properties in the Pacific Northwest region of the United States were studied using real-time measurements from a fixed ground site located in Central Oregon at the Mt. Bachelor Observatory (∼2700 m a.s.l.) as well as near their sources using an aircraft. The regional characteristics of biomass burning aerosols were found to depend strongly on the modified combustion efficiency (MCE), an index of the combustion processes of a fire. Organic aerosol emissions had negative correlations with MCE, whereas the oxidation state of organic aerosol increased with MCE and plume aging. The relationships between the aerosol properties and MCE were consistent between fresh emissions (∼1 h old) and emissions sampled after atmospheric transport (6-45 h), suggesting that biomass burning organic aerosol concentration and chemical properties were strongly influenced by combustion processes at the source and conserved to a significant extent during regional transport. These results suggest that MCE can be a useful metric for describing aerosol properties of wildfire emissions and their impacts on regional air quality and global climate. PMID:27398804

  9. Secondary inorganic aerosol formation and its shortwave direct radiative forcing in China

    NASA Astrophysics Data System (ADS)

    Huang, Xin

    2015-04-01

    Secondary inorganic aerosol (SIA), including sulfate, nitrate and ammonium, is an important part of fine particle. SIA plays a significant role in shortwave radiation transfer. Numerical simulation is usually used to study SIA formation and its climate effect. In this work, we used the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to study SIA formation and its direct radiative forcing (DRF) over China. SO2 oxidation pathways related to mineral aerosol, including transition metal-catalyzed oxidation in aqueous phase and heterogeneous reactions, play an important role in sulfate production, but they are not well treated in current atmospheric models. In this work, we improved the WRF-Chem model by simulating the enhancement role of mineral aerosol in sulfate production. Firstly, we estimated mineral cations based on local measurements in order to well represent aqueous phase acidity. Secondly, we scaled the transition metal concentration to the mineral aerosol levels according to the existing observations and improved transition metal-catalyzed oxidation calculation. Lastly, heterogeneous reactions of acid gases on the surface of mineral aerosol were included in this simulation. Accuracy in the prediction of sulfate by the model was significantly improved and we concluded that mineral aerosol can facilitate SO2 oxidation and subsequent sulfate formation. It was demonstrated that, over China, mineral aerosol was responsible for 21.8% of annual mean sulfate concentration. The enhanced aqueous oxidation was more significant compared to the heterogeneous reactions. In winter, mineral aerosol was responsible for 39.6% of sulfate production. In summer, gaseous oxidation and aqueous oxidation of SO2 by hydrogen peroxide and ozone were the dominant pathways of sulfate formation. Mineral aerosol only contributed 11.9% to the total sulfate production. The increase in annual mean sulfate concentration due to mineral aerosol could reach up to over 6

  10. Stability of aerosol droplets in Bessel beam optical traps under constant and pulsed external forces

    SciTech Connect

    David, Grégory; Esat, Kıvanç; Hartweg, Sebastian; Cremer, Johannes; Chasovskikh, Egor; Signorell, Ruth

    2015-04-21

    We report on the dynamics of aerosol droplets in optical traps under the influence of additional constant and pulsed external forces. Experimental results are compared with simulations of the three-dimensional droplet dynamics for two types of optical traps, the counter-propagating Bessel beam (CPBB) trap and the quadruple Bessel beam (QBB) trap. Under the influence of a constant gas flow (constant external force), the QBB trap is found to be more stable compared with the CPBB trap. By contrast, under pulsed laser excitation with laser pulse durations of nanoseconds (pulsed external force), the type of trap is of minor importance for the droplet stability. It typically needs pulsed laser forces that are several orders of magnitude higher than the optical forces to induce escape of the droplet from the trap. If the droplet strongly absorbs the pulsed laser light, these escape forces can be strongly reduced. The lower stability of absorbing droplets is a result of secondary thermal processes that cause droplet escape.

  11. Future Climate Impacts of Direct Radiative Forcing Anthropogenic Aerosols, Tropospheric Ozone, and Long-lived Greenhouse Gases

    NASA Technical Reports Server (NTRS)

    Chen, Wei-Ting; Liao, Hong; Seinfeld, John H.

    2007-01-01

    Long-lived greenhouse gases (GHGs) are the most important driver of climate change over the next century. Aerosols and tropospheric ozone (O3) are expected to induce significant perturbations to the GHG-forced climate. To distinguish the equilibrium climate responses to changes in direct radiative forcing of anthropogenic aerosols, tropospheric ozone, and GHG between present day and year 2100, four 80-year equilibrium climates are simulated using a unified tropospheric chemistry-aerosol model within the Goddard Institute for Space Studies (GISS) general circulation model (GCM) 110. Concentrations of sulfate, nitrate, primary organic (POA) carbon, secondary organic (SOA) carbon, black carbon (BC) aerosols, and tropospheric ozone for present day and year 2100 are obtained a priori by coupled chemistry-aerosol GCM simulations, with emissions of aerosols, ozone, and precursors based on the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions Scenario (SRES) A2. Changing anthropogenic aerosols, tropospheric ozone, and GHG from present day to year 2100 is predicted to perturb the global annual mean radiative forcing by +0.18 (considering aerosol direct effects only), +0.65, and +6.54 W m(sup -2) at the tropopause, and to induce an equilibrium global annual mean surface temperature change of +0.14, +0.32, and +5.31 K, respectively, with the largest temperature response occurring at northern high latitudes. Anthropogenic aerosols, through their direct effect, are predicted to alter the Hadley circulation owing to an increasing interhemispheric temperature gradient, leading to changes in tropical precipitation. When changes in both aerosols and tropospheric ozone are considered, the predicted patterns of change in global circulation and the hydrological cycle are similar to those induced by aerosols alone. GHG-induced climate changes, such as amplified warming over high latitudes, weakened Hadley circulation, and increasing precipitation over the

  12. Premonsoon shortwave aerosol radiative forcings over the Arabian Sea and tropical Indian Ocean: Yearly and monthly mean variabilities

    NASA Astrophysics Data System (ADS)

    Ramachandran, S.

    2005-04-01

    The yearly and monthly mean variations in the clear-sky shortwave aerosol direct radiative forcings are estimated over Coastal India (CI), the Arabian Sea (AS), and tropical Indian Ocean (TIO) during winter monsoon seasons of 1996-2000. The 5-year mean TOA forcings are estimated to be -10, -9, and -4 W m-2 over CI, AS, and TIO. Surface (SFC) forcings are estimated to be -29, -22, and -5 W m-2 over CI, AS, and TIO, respectively. Atmosphere absorptions are quite large over CI and AS at +19 and +13 W m-2, indicating a significant influence of soot emitted from fossil fuel, biomass burning, and mineral dust. The yearly and monthly mean aerosol forcings are found to exhibit variations. The large atmospheric absorption estimated over CI and AS is found to be a feature of the other polluted ocean and land regions. The influence of relative humidity on the aerosol forcing is estimated. It is shown that as the single scattering albedo increases, the TOA forcing increases while the SFC forcing decreases. With an increase in aerosol optical depths the forcings at TOA and SFC are found to increase substantially, while an increase in the asymmetry parameter is found to decrease both TOA and SFC forcings. The effective factors (forcing at 80% RH/forcing at 30% RH) for the surface are found to be about 1.2 over CI, AS, and 1.4 over TIO. The effective factors estimated over these oceanic regions are found to be smaller than those obtained over the southeastern United States and the mid-Atlantic coast, indicating that the composition of aerosols found over these regions is different.

  13. Aerosol organic carbon to black carbon ratios: Analysis of published data and implications for climate forcing

    NASA Astrophysics Data System (ADS)

    Novakov, T.; Menon, S.; Kirchstetter, T. W.; Koch, D.; Hansen, J. E.

    2005-11-01

    Measurements of organic carbon (OC) and black carbon (BC) concentrations over a variety of locations worldwide have been analyzed to infer the spatial distributions of the ratios of OC to BC. Since these ratios determine the relative amounts of scattering and absorption, they are often used to estimate the radiative forcing due to aerosols. An artifact in the protocol for filter measurements of OC has led to widespread overestimates of the ratio of OC to BC in atmospheric aerosols. We developed a criterion to correct for this artifact and analyze corrected OC to BC ratios. The OC to BC ratios, ranging from 1.3 to 2.4, appear relatively constant and are generally unaffected by seasonality, sources, or technology changes, at the locations considered here. The ratios compare well with emission inventories over Europe and China but are a factor of 2 lower in other regions. The reduced estimate for OC/BC in aerosols strengthens the argument that reduction of soot emissions maybe a useful approach to slow global warming.

  14. Aerosol organic carbon to black carbon ratios: Analysis ofpublished data and implications for climate forcing

    SciTech Connect

    Novakov, T.; Menon, S.; Kirchstetter, T.W.; Koch, D.; Hansen, J.E.

    2005-07-11

    Measurements of organic carbon (OC) and black carbon (BC)concentrations over a variety of locations worldwide, have been analyzed to infer the spatial distributions of the ratios of OC to BC. Since these ratios determine the relative amounts of scattering and absorption, they are often used to estimate the radiative forcing due to aerosols. An artifact in the protocol for filter measurements of OC has led to widespread overestimates of the ratio of OC to BC in atmospheric aerosols. We developed a criterion to correct for this artifact and analyze corrected OC to BC ratios. The OC to BC ratios, ranging from 1.3to 2.4, appear relatively constant and are generally unaffected by seasonality, sources or technology changes, at the locations considered here. The ratios compare well with emission inventories over Europe and China but are a factor of two lower in other regions. The reduced estimate for OC/BC in aerosols strengthens the argument that reduction of soot emissions maybe a useful approach to slow global warming.

  15. Global aerosol formation and revised radiative forcing based on CERN CLOUD data

    NASA Astrophysics Data System (ADS)

    Gordon, H.; Carslaw, K. S.; Sengupta, K.; Dunne, E. M.; Kirkby, J.

    2015-12-01

    New particle formation in the atmosphere accounts for 40-70% of global cloud condensation nuclei (CCN). It is a complex process involving many precursors: sulphuric acid, ions, ammonia, and a wide range of natural and anthropogenic organic molecules. The CLOUD laboratory chamber experiment at CERN allows the contributions of different compounds to be disentangled in a uniquely well-controlled environment. To date, CLOUD has measured over 500 formation rates (Riccobono 2014, Kirkby 2015, Dunne 2015), under conditions representative of the planetary boundary layer and free troposphere. To understand the sensitivity of the climate to anthropogenic atmospheric aerosols, we must quantify historical aerosol radiative forcing. This requires an understanding of pre-industrial aerosol sources. Here we show pre-industrial nucleation over land usually involves organic molecules in the very first steps of cluster formation. The complexity of the organic vapors is a major challenge for theoretical approaches. Furthermore, with fewer sulphuric acid and ammonia molecules available to stabilize nucleating clusters in the pre-industrial atmosphere, ions from radon or galactic cosmic rays were probably more important than they are today. Parameterizations of particle formation rates determined in CLOUD as a function of precursor concentrations, temperature and ions are being used to refine the GLOMAP aerosol model (Spracklen 2005). The model simulates the growth, transport and loss of particles, translating nucleation rates to CCN concentrations. This allows us to better understand the effects of pre-industrial and present-day particle formation. I will present new results on global CCN based on CLOUD data, including estimates of anthropogenic aerosol radiative forcing, currently the most uncertain driver of climate change (IPCC 2013). References: Riccobono, F. et al, Science 344 717 (2014); Kirkby, J. et al, in review; Dunne, E. et al, in preparation; Spracklen, D. et al, Atmos

  16. High-efficiency particulate air filter test stand and aerosol generator for particle loading studies.

    PubMed

    Arunkumar, R; Hogancamp, Kristina U; Parsons, Michael S; Rogers, Donna M; Norton, Olin P; Nagel, Brian A; Alderman, Steven L; Waggoner, Charles A

    2007-08-01

    This manuscript describes the design, characterization, and operational range of a test stand and high-output aerosol generator developed to evaluate the performance of 30 x 30 x 29 cm(3) nuclear grade high-efficiency particulate air (HEPA) filters under variable, highly controlled conditions. The test stand system is operable at volumetric flow rates ranging from 1.5 to 12 standard m(3)/min. Relative humidity levels are controllable from 5%-90% and the temperature of the aerosol stream is variable from ambient to 150 degrees C. Test aerosols are produced through spray drying source material solutions that are introduced into a heated stainless steel evaporation chamber through an air-atomizing nozzle. Regulation of the particle size distribution of the aerosol challenge is achieved by varying source solution concentrations and through the use of a postgeneration cyclone. The aerosol generation system is unique in that it facilitates the testing of standard HEPA filters at and beyond rated media velocities by consistently providing, into a nominal flow of 7 standard m(3)/min, high mass concentrations (approximately 25 mg/m(3)) of dry aerosol streams having count mean diameters centered near the most penetrating particle size for HEPA filters (120-160 nm). Aerosol streams that have been generated and characterized include those derived from various concentrations of KCl, NaCl, and sucrose solutions. Additionally, a water insoluble aerosol stream in which the solid component is predominantly iron (III) has been produced. Multiple ports are available on the test stand for making simultaneous aerosol measurements upstream and downstream of the test filter. Types of filter performance related studies that can be performed using this test stand system include filter lifetime studies, filtering efficiency testing, media velocity testing, evaluations under high mass loading and high humidity conditions, and determination of the downstream particle size distributions.

  17. High-efficiency particulate air filter test stand and aerosol generator for particle loading studies.

    PubMed

    Arunkumar, R; Hogancamp, Kristina U; Parsons, Michael S; Rogers, Donna M; Norton, Olin P; Nagel, Brian A; Alderman, Steven L; Waggoner, Charles A

    2007-08-01

    This manuscript describes the design, characterization, and operational range of a test stand and high-output aerosol generator developed to evaluate the performance of 30 x 30 x 29 cm(3) nuclear grade high-efficiency particulate air (HEPA) filters under variable, highly controlled conditions. The test stand system is operable at volumetric flow rates ranging from 1.5 to 12 standard m(3)/min. Relative humidity levels are controllable from 5%-90% and the temperature of the aerosol stream is variable from ambient to 150 degrees C. Test aerosols are produced through spray drying source material solutions that are introduced into a heated stainless steel evaporation chamber through an air-atomizing nozzle. Regulation of the particle size distribution of the aerosol challenge is achieved by varying source solution concentrations and through the use of a postgeneration cyclone. The aerosol generation system is unique in that it facilitates the testing of standard HEPA filters at and beyond rated media velocities by consistently providing, into a nominal flow of 7 standard m(3)/min, high mass concentrations (approximately 25 mg/m(3)) of dry aerosol streams having count mean diameters centered near the most penetrating particle size for HEPA filters (120-160 nm). Aerosol streams that have been generated and characterized include those derived from various concentrations of KCl, NaCl, and sucrose solutions. Additionally, a water insoluble aerosol stream in which the solid component is predominantly iron (III) has been produced. Multiple ports are available on the test stand for making simultaneous aerosol measurements upstream and downstream of the test filter. Types of filter performance related studies that can be performed using this test stand system include filter lifetime studies, filtering efficiency testing, media velocity testing, evaluations under high mass loading and high humidity conditions, and determination of the downstream particle size distributions. PMID

  18. High-efficiency particulate air filter test stand and aerosol generator for particle loading studies

    NASA Astrophysics Data System (ADS)

    Arunkumar, R.; Hogancamp, Kristina U.; Parsons, Michael S.; Rogers, Donna M.; Norton, Olin P.; Nagel, Brian A.; Alderman, Steven L.; Waggoner, Charles A.

    2007-08-01

    This manuscript describes the design, characterization, and operational range of a test stand and high-output aerosol generator developed to evaluate the performance of 30×30×29cm3 nuclear grade high-efficiency particulate air (HEPA) filters under variable, highly controlled conditions. The test stand system is operable at volumetric flow rates ranging from 1.5to12standardm3/min. Relative humidity levels are controllable from 5%-90% and the temperature of the aerosol stream is variable from ambient to 150°C. Test aerosols are produced through spray drying source material solutions that are introduced into a heated stainless steel evaporation chamber through an air-atomizing nozzle. Regulation of the particle size distribution of the aerosol challenge is achieved by varying source solution concentrations and through the use of a postgeneration cyclone. The aerosol generation system is unique in that it facilitates the testing of standard HEPA filters at and beyond rated media velocities by consistently providing, into a nominal flow of 7standardm3/min, high mass concentrations (˜25mg/m3) of dry aerosol streams having count mean diameters centered near the most penetrating particle size for HEPA filters (120-160nm). Aerosol streams that have been generated and characterized include those derived from various concentrations of KCl, NaCl, and sucrose solutions. Additionally, a water insoluble aerosol stream in which the solid component is predominantly iron (III) has been produced. Multiple ports are available on the test stand for making simultaneous aerosol measurements upstream and downstream of the test filter. Types of filter performance related studies that can be performed using this test stand system include filter lifetime studies, filtering efficiency testing, media velocity testing, evaluations under high mass loading and high humidity conditions, and determination of the downstream particle size distributions.

  19. Carbonaceous aerosols over China--review of observations, emissions, and climate forcing.

    PubMed

    Wang, Linpeng; Zhou, Xuehua; Ma, Yujie; Cao, Zhaoyu; Wu, Ruidong; Wang, Wenxing

    2016-01-01

    Carbonaceous aerosols have been attracting attention due to the influence on visibility, air quality, and regional climate. Statistical analyses based on concentration levels, spatial-temporal variations, correlations, and organic carbon (OC) to element carbon (EC) ratios from published data of OC and EC in particulate matter (PM2.5 and PM10) were carried out in order to give a carbonaceous aerosol profile in China. The results showed maxima for OC of 29.5 ± 18.2 μg C m(-3) and for EC of 8.4 ± 6.3 μg C m(-3) in winter and minima for OC of 12.9 ± 7.7 μg C m(-3) in summer and for EC of 4.6 ± 2.8 μg C m(-3) in spring. In addition, OC and EC both had higher concentrations in urban than those in rural sites. Carbonaceous aerosol levels in China are about three to seven times higher compared to those in the USA and Europe. OC and EC occupied 20 ± 6 and 7 ± 3% of PM2.5 mass and 17 ± 7 and 5 ± 3% of PM10 mass, respectively, implying that carbonaceous aerosols are the main component of PM, especially OC. Secondary organic carbon (SOC) was a significant portion of PM and contributed 41 ± 26% to OC and 8 ± 6% to PM2.5 mass. The OC/EC ratio was 3.63 ± 1.73, which, along with the good correlation between OC and EC and the OC to EC slope of 2.29, signifies that coal combustion and/or vehicular exhaust is the dominated carbonaceous aerosol source in China. These provide a primary observation-based understanding of carbonaceous aerosol pollution in China and have a great significance in improving the emission inventory and climate forcing evaluation.

  20. Carbonaceous aerosols over China--review of observations, emissions, and climate forcing.

    PubMed

    Wang, Linpeng; Zhou, Xuehua; Ma, Yujie; Cao, Zhaoyu; Wu, Ruidong; Wang, Wenxing

    2016-01-01

    Carbonaceous aerosols have been attracting attention due to the influence on visibility, air quality, and regional climate. Statistical analyses based on concentration levels, spatial-temporal variations, correlations, and organic carbon (OC) to element carbon (EC) ratios from published data of OC and EC in particulate matter (PM2.5 and PM10) were carried out in order to give a carbonaceous aerosol profile in China. The results showed maxima for OC of 29.5 ± 18.2 μg C m(-3) and for EC of 8.4 ± 6.3 μg C m(-3) in winter and minima for OC of 12.9 ± 7.7 μg C m(-3) in summer and for EC of 4.6 ± 2.8 μg C m(-3) in spring. In addition, OC and EC both had higher concentrations in urban than those in rural sites. Carbonaceous aerosol levels in China are about three to seven times higher compared to those in the USA and Europe. OC and EC occupied 20 ± 6 and 7 ± 3% of PM2.5 mass and 17 ± 7 and 5 ± 3% of PM10 mass, respectively, implying that carbonaceous aerosols are the main component of PM, especially OC. Secondary organic carbon (SOC) was a significant portion of PM and contributed 41 ± 26% to OC and 8 ± 6% to PM2.5 mass. The OC/EC ratio was 3.63 ± 1.73, which, along with the good correlation between OC and EC and the OC to EC slope of 2.29, signifies that coal combustion and/or vehicular exhaust is the dominated carbonaceous aerosol source in China. These provide a primary observation-based understanding of carbonaceous aerosol pollution in China and have a great significance in improving the emission inventory and climate forcing evaluation. PMID:26385857

  1. Aerosol Radiative Effects: Expected Variations in Optical Depth Spectra and Climate Forcing, with Implications for Closure Experiment Strategies

    NASA Technical Reports Server (NTRS)

    Russell, Philip B.; Stowe, L. L.; Hobbs, P. V.; Podolske, James R. (Technical Monitor)

    1995-01-01

    We examine measurement strategies for reducing uncertainties in aerosol direct radiative forcing by focused experiments that combine surface, air, and space measurements. Particularly emphasized are closure experiments, which test the degree of agreement among different measurements and calculations of aerosol properties and radiative effects. By combining results from previous measurements of large-scale smokes, volcanic aerosols, and anthropogenic aerosols with models of aerosol evolution, we estimate the spatial and temporal variability in optical depth spectra to be expected in the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX, planned for summer 1996 off the Eastern U.S. seaboard). In particular, we examine the expected changes in the wavelength dependence of optical depth as particles evolve through nucleation, growth by condensation and coagulation, and removal via sedimentation. We then calculate the expected radiative climate forcing (i.e. change in net radiative flux) for typical expected aerosols and measurement conditions (e.g. solar elevations, surface albedos, radiometer altitudes). These calculations use new expressions for flux and albedo changes, which account not only for aerosol absorption, but also for instantaneous solar elevation angles and the dependence of surface albedo on solar elevation. These factors, which are usually ignored or averaged in calculations of global aerosol effects, can have a strong influence on fluxes measured in closure experiments, and hence must be accounted for in calculations if closure is to be convincingly tested. We compare the expected measurement signal to measurement uncertainties expected for various techniques in various conditions. Thereby we derive recommendations for measurement strategies that combine surface, airborne, and spaceborne measurements.

  2. Development of RAMS-CMAQ to Simulate Aerosol Optical Depth and Aerosol Direct Radiative Forcing and Its Application to East Asia

    SciTech Connect

    Han, Xiao; Zhang, Meigen; Liu, Xiaohong; Ghan, Steven J; Xin, Jin-Yuan; Wang, Li-Li

    2009-11-16

    The air quality modeling system RAMS (Regional Atmospheric Modeling System)-CMAQ (Models-3 Community Multi-scale Air Quality) is developed to simulate the aerosol optical depth (AOD) and aerosol direct forcing (DF). The aerosol-specific extinction, single scattering albedo, and asymmetry factor are parameterized based on Mie theory taking into account the aerosol size distribution, composition, refractive index, and water uptake of solution particles. A two-stream solar radiative model considers all gaseous molecular absorption, Rayleigh scattering, and aerosols and clouds. RAMSCMAQ is applied to simulate all major aerosol concentrations (e.g., sulfate, nitrate, ammonium, organic carbon, black carbon, fine soil, and sea salt) and AOD and DF over East Asia in 2005. To evaluate its performance, the simulated AOD values were compared with ground-based in situ measurements. The comparison shows that RAMSCMAQ performed well in most of the model domain and generally captured the observed variations. High AOD values (0.2-1.0) mainly appear in the Sichuan Basin as well as in central and southeastern China. The geographic distribution of DF generally follows the AOD distribution patterns, and the DF at the top-of-the-atmosphere is less than -25 and -20 W m-2 in clear-sky and all-sky over the Sichuan Basin. Both AOD and DF exhibit seasonal variations with lower values in July and higher ones in January. The DF could obviously be impacted by high cloud fractions.

  3. Understanding the Rapid Precipitation Response to CO2 and Aerosol Forcing on a Regional Scale

    NASA Astrophysics Data System (ADS)

    Richardson, Thomas; Forster, Piers; Parker, Doug; Andrews, Tim

    2015-04-01

    Regional precipitation change is one of the most uncertain aspects of climate change prediction, and can have major societal implications. On a global scale, precipitation is tightly constrained by the radiative cooling of the troposphere. As a result, precipitation exhibits a significant rapid adjustment in response to certain forcing agents, which is important for understanding long term climate change. However, the mechanisms which drive the spatial pattern of rapid adjustment are not well understood. In this study we analyze the spatial pattern of rapid precipitation change using simulations with fixed sea surface temperature. Using data obtained from sixteen models participating in the Coupled Model Inter-comparison Project Phase 5 (CMIP5), we investigate the response to three different forcing scenarios; an abrupt quadrupling of CO2, an increase in all aerosols, and an increase in sulphate aerosol from pre-industrial to present day levels. Analysis of the local atmospheric energy budget is used to understand the observed changes. We find that the spatial pattern of rapid precipitation adjustment due to forcing is primarily driven by the rapid land surface response. As a result, the spatial pattern due to quadrupling CO2 opposes that due to increased sulphate and increased all aerosols. Increasing CO2 levels causes warming of the land surface, due to enhanced downwelling longwave radiation. This destabilizes the atmosphere by warming the lower troposphere, producing an overall shift of convection and precipitation to over land. The reverse is observed for increased sulphate and increased all aerosols. Changes in tropospheric cooling are important in determining the magnitude of regional precipitation change, thereby satisfying global energy budget constraints. We find the spatial pattern of rapid precipitation change due to quadrupling CO2 levels is robust between models. The most significant precipitation changes occur in the tropics, with significant

  4. A Study of Direct and Cloud-Mediated Radiative Forcing of Climate Due to Aerosols

    NASA Technical Reports Server (NTRS)

    Yu, Shao-Cai

    1999-01-01

    The Intergovernmental Panel on Climate Change (IPCC) has reported that in the southeastern US and eastern China, the general greenhouse warming due to anthropogenic gaseous emissions is dominated by the cooling effect of anthropogenic aerosols. To verify this model prediction in eastern China and southeastern US, we analyzed regional patterns of climate changes at 72 stations in eastern China during 1951- 94 (44 years), and at 52 stations in the southeastern US during 1949-94 (46 years) to detect the fingerprint of aerosol radiative forcing. It was found that the mean rates of change of annual mean daily, maximum, minimum temperatures and diurnal temperature range (DTR) in eastern China were 0.8, -0.2, 1.8, and -2.0 C/100 years respectively, while the mean rates of change of annual mean daily, maximum, minimum temperatures and DTR in the southeastern US were -0.2, -0.6, 0.2, and -0.8 C/100 years, respectively. This indicates that the high rate of increase in annual mean minimum temperature in eastern China results in a slightly warming trend of daily temperature, while the high rate of decrease in annual mean maximum temperature and low rate of increase in annual mean minimum temperature lead to the cooling trend of daily temperature in the southeastern US. We found that the warming from the longwave forcing due to both greenhouse gases and aerosols was completely counteracted by the shortwave aerosol forcing in the southeastern US in the past 46 years. A slightly overall warming trend in eastern China is evident; winters have become milder. This finding is explained by hypothesizing that increasing energy usage during the past 44 years has resulted in more coal and biomass burning, thus increasing the emission of absorbing soot and organic aerosols in eastern China. Such emissions, in addition to well-known Asia dust and greenhouse gases, may be responsible for the winter warming trend in eastern China that we have reported here. The sensitivity of aerosol

  5. Experimental Assessment of Collection Efficiency of Submicron Aerosol Particles by Cloud Droplets

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Oo, K.; Brown, M. D.; Dhaniyala, S.; Cziczo, D. J.

    2012-12-01

    An experimental setup has been constructed to measure the collection efficiency of submicron aerosol particles by cloud droplets. The collection efficiency study is a prelude to studying contact nucleation, which is a potentially important ice nucleation mode that is not well-understood. This laboratory setup is a step closer to experimentally assessing the importance of contact nucleation. Water droplets with 20 micron diameter and submicron aerosol particles are brought into contact in an injector situated inside a chilled glass flow tube. The water droplets that collect aerosol particles are allowed to pass through a counterflow virtual impactor (CVI), which accepts large droplets and rejects aerosol particles that have not coagulated with the water droplets. The collected droplets are sent into the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument which performs in situ chemical analysis of a single particle. The number of aerosol particles collected by the single water droplet is quantified by calibrating the PALMS with known concentrations of aerosol particles. The water droplets contain a known amount of ammonium sulfate for identification purpose in the mass spectrometry. Preliminary results from the experiment will be discussed and compared with previous theoretical and experimental studies.

  6. Easy Aerosol - Robust and non-robust circulation responses to aerosol radiative forcing in comprehensive atmosphere models

    NASA Astrophysics Data System (ADS)

    Voigt, Aiko; Bony, Sandrine; Stevens, Bjorn; Boucher, Olivier; Medeiros, Brian; Pincus, Robert; Wang, Zhili; Zhang, Kai; Lewinschal, Anna; Bellouin, Nicolas; Yang, Young-Min

    2015-04-01

    A number of recent studies illustrated the potential of aerosols to change the large-scale atmospheric circulation and precipitation patterns. It remains unclear, however, to what extent the proposed aerosol-induced changes reflect robust model behavior or are affected by uncertainties in the models' treatment of parametrized physical processes, such as those related to clouds. "Easy Aerosol", a model-intercomparison project organized within the Grand Challenge on Clouds, Circulation and Climate Sensitivity of the World Climate Research Programme, addresses this question by subjecting a suite of comprehensive atmosphere general circulation models with prescribed sea-surface temperatures (SSTs) to the same set of idealized "easy" aerosol perturbations. This contribution discusses the aerosol perturbations as well as their impact on the model's precipitation and surface winds. The aerosol perturbations are designed based on a global aerosol climatology and mimic the gravest mode of the anthropogenic aerosol. Specifically, the meridional and zonal distributions of total aerosol optical depth are approximated by a superposition of Gaussian plumes; the vertical distribution is taken as constant within the lowest 1250m of the atmosphere followed by an exponential decay with height above. The aerosol both scatters and absorbs shortwave radiation, but in order to focus on direct radiative effects aerosol-cloud interactions are omitted. Each model contributes seven simulations. A clean control case with no aerosol-radiative effects at all is compared to six perturbed simulations with differing aerosol loading, zonal aerosol distributions, and SSTs. To estimate the role of natural variability, one of the models, MPI-ESM, contributes a 5-member ensemble for each simulation. If the observed SSTs from years 1979-2005 are prescribed, the aerosol leads to a local depression of precipitation at the Northern Hemisphere center of the aerosol and a northward shift of the

  7. GCM Simulations of Volcanic Aerosol Forcing. Part I: Climate Changes Induced by Steady-State Perturbations.

    NASA Astrophysics Data System (ADS)

    Pollack, James B.; Rind, David; Lacis, Andrew; Hansen, James E.; Sato, Makiko; Ruedy, Reto

    1993-09-01

    The authors have used the Goddard Institute for Space Studies Climate Model II to simulate the response of the climate system to a spatially and temporally constant forcing by volcanic aerosols having an optical depth of 0.15. The climatic changes produced by long-term volcanic aerosol forcing are obtained by differencing this simulation and one made for the present climate with no volcanic aerosol forcing. These climatic changes are compared with those obtained with the same climate model when the C02 content of the atmosphere was doubled (2×C02) and when the boundary conditions associated with the peak of the last ice age were used (18 K). In all three cases, the absolute magnitude of the change in the globally averaged air temperature at the surface is approximately the same, 5 K.The simulations imply that a significant cooling of the troposphere and surface can occur at times of closely spaced, multiple, sulfur-rich volcanic explosions that span time scales of decades to centuries, such as occurred at the end of the nineteenth and beginning of the twentieth centuries. The steady-state climate response to volcanic forcing includes a large expansion of sea ice, especially in the Southern Hemisphere; a resultant large increase in surface and planetary albedo at high latitudes; and sizable changes in the annually and zonally averaged air temperature, T; T at the surface (Ts) does not sharply increase with increasing latitude, while T in the lower stratosphere is positive at low latitudes and negative at high latitudes.In certain ways, the climate response to the three different forcings is similar. Direct radiative forcing accounts for 30% and 25% of the total Ts in the volcano and 2×C02 runs, respectively. Changes in atmospheric water vapor act as the most important feedback, and are positive in all three cases. Albedo feedback is a significant, positive feedback at high latitudes in all three simulations, although the land ice feedback is prominent only in the

  8. Impact of the aging process of black carbon aerosols on their spatial distribution, hygroscopicity, and radiative forcing in a global climate model

    NASA Astrophysics Data System (ADS)

    Goto, D.; Oshima, N.; Nakajima, T.; Takemura, T.; Ohara, T.

    2012-11-01

    surface aerosol forcing efficiencies normalized by aerosol optical thickness and by BC burden varied greatly with region in the AGV method, which allowed for the existence of internally mixed BC and sulfate, whereas these were not varied with region in the AGF method. These results suggest that the efficiencies of BC-ARF obtained by previous studies using the AGF method are significantly underestimated.

  9. Aerosol hygroscopicity and its impact on atmospheric visibility and radiative forcing in Guangzhou during the 2006 PRIDE-PRD campaign

    NASA Astrophysics Data System (ADS)

    Liu, Xingang; Zhang, Yuanhang; Cheng, Yafang; Hu, Min; Han, Tingting

    2012-12-01

    The objective of this study is to quantify the relation of aerosol chemical compositions and optical properties, and to assess the impact of relative humidity (RH) on atmospheric visibility and aerosol direct radiative forcing (ADRF). Mass concentration and size distribution of aerosol chemical compositions as well as aerosol optical properties were concurrently measured at Guangzhou urban site during the PRD (Pearl River Delta) campaign from 1 to 31 July, 2006. Gaseous pollutant NO2 and meteorological parameter were simultaneously monitored. Compared with its dry condition, atmospheric ambient extinction coefficient σext(RH) averagely increased about 51% and atmospheric visibility deceased about 35%, among which RH played an important role on the optical properties of water soluble inorganic salts. (NH4)2SO4 is the most important component responsible for visibility degradation at Guangzhou. In addition, the asymmetry factor g increased from 0.64 to 0.74 with the up-scatter fraction β decreasing from 0.24 to 0.19 when RH increasing from 40% to 90%. At 80% RH, the ADRF increased about 280% compared to that at dry condition and it averagely increased about 100% during the campaign under ambient conditions. It can be inferred that aerosol water content is a key factor and could not be ignored in assessing the role of aerosols in visibility impairment and radiative forcing, especially in the regions with high RH.

  10. The impact of detailed urban-scale processing on the composition, distribution, and radiative forcing of anthropogenic aerosols

    NASA Astrophysics Data System (ADS)

    Cohen, Jason Blake; Prinn, Ronald G.; Wang, Chien

    2011-05-01

    Detailed urban-scale processing has not been included in global 3D chemical transport models due to its large computational demands. Here we present a metamodel for including this processing, and compare it with the use of the traditional approach of dilution of emissions into large grid boxes. This metamodel is used in a global 3D model to simulate the effects of cities around the world on aerosol chemistry, physics, and radiative effects at the global scale. We show that the biases caused by ignoring urban processing on the global values of total aerosol surface concentration, the total aerosol column abundance, the aerosol optical depth (AOD), the absorbing aerosol optical depth (AAOD), and the top of the atmosphere radiative forcing (TOA) respectively are +26 ± 32%, +51 ± 1012%, +42 ± 810%, +8 ± 1618%, and -0.27 ± 0.140.10 W/m2. These results show that failure to consider urban scale processing leads to significantly more negative aerosol radiative forcing compared to when detailed urban scale processing is considered.

  11. Incorporation of Advanced Activation Treatments into CESM/CAM5: Model Evaluation and Impacts on Aerosol Indirect Forcing

    NASA Astrophysics Data System (ADS)

    Gantt, B.; He, J.; Zhang, X.; Zhang, Y.; Nenes, A.

    2013-12-01

    One of the greatest sources of uncertainty in climate science is the influence of aerosols on clouds through indirect effects, especially processes affecting the activation of aerosols into cloud droplets. Aerosol activation parameterizations incorporate much of the complexity of these processes, but the small differences between parameterizations can have a large impact on the spatiotemporal distribution of activated aerosols and the resulting cloud properties. Currently, most models simulate aerosol activation using the Abdul-Razzak and Ghan [2000] (AR-G00) scheme which derives an empiric calculation of the maximum parcel supersaturation based on the regression of numerical parcel calculations. The Community Atmosphere Model version 5.1.1 within the Community Earth Systems Model version 1.0.5 (CESM/CAM5) is an online-coupled Earth Systems model that simulates the interactions among aerosols, clouds, and radiation. CESM/CAM5 uses the AR-G00 scheme to simulate aerosol activation. In this work, we update CESM/CAM5 by incorporating a series of explicit aerosol activation schemes (Fountoukis and Nenes [2005]; Barahona and Nenes [2007]; Kumar et al. [2009]; and Barahona et al. [2010]) which account for the impacts of insoluble aerosol adsorption, giant cloud condensation nuclei activation kinetics, and entrainment on cloud droplet number concentrations (CDNC). CESM/CAM5 results with the empiric and explicit aerosol activation schemes are evaluated against several global datasets including observed low-level CDNC and satellite-derived cloud optical thickness (COT), liquid water path (LWP), and shortwave cloud forcing (SWCF). Globally, the incorporation of all explicit schemes leads to an average increase in column CDNC of 155%, increase (more negative) in SWCF of 13%, and decrease in surface shortwave radiation of -4%. In terms of climate impacts, these schemes result in an annual mean decrease in surface temperature and precipitation of -0.9 K (~0.2%) and -0.04 mm day

  12. Potential of lidar backscatter data to estimate solar aerosol radiative forcing

    NASA Astrophysics Data System (ADS)

    Wendisch, Manfred; Müller, Detlef; Mattis, Ina; Ansmann, Albert

    2006-02-01

    The potential to estimate solar aerosol radiative forcing (SARF) in cloudless conditions from backscatter data measured by widespread standard lidar has been investigated. For this purpose 132 days of sophisticated ground-based Raman lidar observations (profiles of particle extinction and backscatter coefficients at 532 nm wavelength) collected during two campaigns [the European Aerosol Research Lidar Network (EARLINET) and the Indian Ocean Experiment (INDOEX)] were analyzed. Particle extinction profiles were used as input for radiative transfer simulations with which to calculate the SARF, which then was plotted as a function of the column (i.e., height-integrated) particle backscatter coefficient (betac). A close correlation between the SARF and betac was found. SARF-betac parameterizations in the form of polynomial fits were derived that exhibit an estimated uncertainty of +/-(10-30)%. These parameterizations can be utilized to analyze data of upcoming lidar satellite missions and for other purposes. The EARLINET-based parameterizations can be applied to lidar measurements at mostly continental, highly industrialized sites with limited maritime influence (Europe, North America), whereas the INDOEX parameterizations rather can be employed in polluted maritime locations, e.g., coastal regions of south and east Asia.

  13. Potential of lidar backscatter data to estimate solar aerosol radiative forcing.

    PubMed

    Wendisch, Manfred; Müller, Detlef; Mattis, Ina; Ansmann, Albert

    2006-02-01

    The potential to estimate solar aerosol radiative forcing (SARF) in cloudless conditions from backscatter data measured by widespread standard lidar has been investigated. For this purpose 132 days of sophisticated ground-based Raman lidar observations (profiles of particle extinction and backscatter coefficients at 532 nm wavelength) collected during two campaigns [the European Aerosol Research Lidar Network (EARLINET) and the Indian Ocean Experiment (INDOEX)] were analyzed. Particle extinction profiles were used as input for radiative transfer simulations with which to calculate the SARF, which then was plotted as a function of the column (i.e., height-integrated) particle backscatter coefficient (beta(c)). A close correlation between the SARF and beta(c) was found. SARF-beta(c) parameterizations in the form of polynomial fits were derived that exhibit an estimated uncertainty of +/-(10-30)%. These parameterizations can be utilized to analyze data of upcoming lidar satellite missions and for other purposes. The EARLINET-based parameterizations can be applied to lidar measurements at mostly continental, highly industrialized sites with limited maritime influence (Europe, North America), whereas the INDOEX parameterizations rather can be employed in polluted maritime locations, e.g., coastal regions of south and east Asia.

  14. The Effect of Asian Dust Aerosols on Cloud Properties and Radiative Forcing from MODIS and CERES

    NASA Technical Reports Server (NTRS)

    Huang, Jianping; Minnis, Patrick; Lin, Bing; Wang, Tianhe; Yi, Yuhong; Hu, Yongxiang; Sun-Mack, Sunny; Ayers, Kirk

    2005-01-01

    The effects of dust storms on cloud properties and radiative forcing are analyzed over northwestern China from April 2001 to June 2004 using data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) and Clouds and the Earth's Radiant Energy System (CERES) instruments on the Aqua and Terra satellites. On average, ice cloud effective particle diameter, optical depth and ice water path of the cirrus clouds under dust polluted conditions are 11%, 32.8%, and 42% less, respectively, than those derived from ice clouds in dust-free atmospheric environments. The humidity differences are larger in the dusty region than in the dust-free region, and may be caused by removal of moisture by wet dust precipitation. Due to changes in cloud microphysics, the instantaneous net radiative forcing is reduced from -71.2 W/m2 for dust contaminated clouds to -182.7 W/m2 for dust-free clouds. The reduced cooling effects of dusts may lead to a net warming of 1 W/m2, which, if confirmed, would be the strongest aerosol forcing during later winter and early spring dust storm seasons over the studied region.

  15. Impact of Indonesian forest fires during the 1997 El Nino on aerosol distribution and clear sky aerosol aradiatikve forcing over the Indian Ocean

    NASA Astrophysics Data System (ADS)

    Parameswaran, K.; Nair, S.; Rejeev, K.

    The El Nino event of 1997-1998 followed by the La Nina in 1998-1999 was the strongest of its kind encountered in the 20t h century. Associated with this event Indonesia experienced severe drought leading to large forest fires. Large aerosol plume from these fires has advected over the Equatorial Indian Ocean region. Development and decay of this plume and its regional transport are studied using aerosol optical depth (AOD) derived from NOAA-14 AVHRR data using the Discrete Ordinate Method along with the tropospheric circulation derived from NCEP/NCAR reanalysis. In the second half of 1997 extensive smoke and haze episodes are observed over the tropical Indian Ocean in the latitude range of 5° N to 10° S. The AOD values at 630nm often exceeded 1.0 near Indonesia and in the southeastern parts of Bay of Bengal. Development of this plume started from September and continued up to the first half of November. During first half of September, the plume was conf ined to the coastal regions of Indonesia and then started developing towards west to reach up to 60°E. Decay of the plume started by the middle of November and subsided almost completely by December. During the development phase this plume showed a consistent increase in AOD from western Indian Ocean to Eastern part of tropical Indian Ocean. This westward transport of aerosols from the Indonesian region was confined to the equatorial latitudes. This was due to the reversal of zonal circulation during the El Nino period leading to large westward wind anomaly in the equatorial Indian Ocean region. Westward propagation of the aerosol plume is arrested near ~60°E because of the large convection and rainfall caused by El Nino in this longitude region. The El Nino related weather and atmospheric dynamics is found to have significantly influenced the regional aerosol distribution over the Indian Ocean. On an average, the diurnal mean clear sky aerosol radiative forcing at top of atmosphere (TOA) is estimated to be

  16. Experimental Assessment of Collection Efficiency of Submicron Aerosol Particles by Cloud Droplets

    NASA Astrophysics Data System (ADS)

    Huang, Y. W.; Ardon-Dryer, K.; Cziczo, D. J.

    2014-12-01

    The interplay between aerosol particles and water droplets in the atmosphere, especially in clouds, influences both aerosol and cloud properties. The major uncertainty in our understanding of climate arises in the indirect effect of aerosol and their ability to impact cloud formation and consequently alter the global radiative balance. The collision between a water droplet and aerosol particles that results in coalescence is termed "collection" or "coagulation". Coagulation can lead to aerosol removal from the atmosphere or induce ice nucleation via contact freezing. There is a theoretical collection efficiency minimum of particles with diameter between 0.1-2 µm, called the "Greenfield Gap". Experimental effort, however, was limited to drizzle and rain drops until recently, and has not constrained parameters that describe particle collection efficiency by cloud droplets. Collection efficiency is also an important parameter for assessing contact freezing, the least known ice nucleation mechanism today. Experimentally assessing collection efficiency can prove the existence of the "Greenfield Gap" and lay the foundation for studying contact freezing. We recently constructed the MIT-Contact Freezing Chamber (MIT-CFC) to study coagulation experimentally. A stream of 40 µm cloud droplets fall freely into the chamber and collide with aerosol particles with known size and concentration. The outflow goes through a series of dryers before entering the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument for chemical composition analysis. PALMS is a true single-particle instrument and gives information on the size and the chemical composition of each particle. Coagulated particles from the MIT-CFC have mass spectral signatures of both the aerosol particles and the droplet residuals, while the droplet residual contains no signature of the aerosol particles. To our knowledge, this is the first time coagulation has been seen on a single-particle basis. We will

  17. Seasonal differences in aerosol abundance and radiative forcing in months of contrasting emissions and rainfall over northern South Asia

    NASA Astrophysics Data System (ADS)

    Sadavarte, P.; Venkataraman, C.; Cherian, R.; Patil, N.; Madhavan, B. L.; Gupta, T.; Kulkarni, S.; Carmichael, G. R.; Adhikary, B.

    2016-01-01

    A modeling framework was used to examine gaps in understanding of seasonal and spatial heterogeneity in aerosol abundance and radiative forcing over northern South Asia, whose glimpses are revealed in observational studies. Regionally representative emissions were used in chemical transport model simulations at a spatial resolution of 60 × 60 km2, in April, July and September, chosen as months of contrasting emissions and rainfall. Modeled aerosol abundance in northern South Asia was predominantly found to be dust and carbonaceous in April, dust and sulfate in July and sulfate and carbonaceous in September. Anthropogenic aerosols arose from energy-use emissions (from industrial sources, residential biofuel cooking, brick kilns) in all months, additionally from field burning in April, and incursion from East Asia in September. In April, carbonaceous aerosols were abundant from open burning of agricultural fields even at high altitude locations (Godavari), and of forests in the eastern Gangetic Plain (Kolkata). Direct radiative forcing and heating rate, calculated from OPAC-SBDART, using modeled aerosol fields, and corrected by MODIS AOD observations, showed regionally uniform atmospheric forcing in April, compared to that in other months, influenced by both dust and black carbon abundance. A strong spatial heterogeneity of radiative forcing and heating rate was found, with factor of 2.5-3.5 lower atmospheric forcing over the Tibet plateau than that over the Ganga Plain and Northwest in July and September. However, even over the remote Tibet plateau, there was significant anthropogenic contribution to atmospheric forcing and heating rate (45% in Apr, 75% in Sep). Wind fields showed black carbon transport from south Asia in April and east Asia in September. Further evaluation of the transport of dust and anthropogenic emissions from various source regions and their deposition in the Himalaya and Tibet, is important in understanding regional air quality and climate

  18. Direct Radiative Forcing and Regional Climatic Effects of Anthropogenic Aerosols Over East Asia: A Regional Coupled Climate-Chemistry/Aerosol Model Study

    SciTech Connect

    Giorgi, Filippo; Bi, Xunqiang; Qian, Yun )

    2002-09-01

    We present a series of regional climate model simulations aimed at assessing the radiative forcing and surface climatic effects of anthropogenic sulfate and fossil fuel soot over east Asia. The simulations are carried out with a coupled regional climate-chemistry/aerosol model for the 5-year period of 1993-1997 using published estimates of sulfur emissions for the period. Anthropogenic sulfate induces a negative radiative forcing spatially varying from -1 to -8 W/m2 in the winter to -1 to -15 W/m2 in the summer, with maxima over the Sichan Basin of southwest China and over some areas of east and northeast China. This forcing induces a surface cooling in the range of -0.1 to -0.7 K. Fossil fuel soot exerts a positive atmospheric radiative forcing of 0.5 to 2 W/m2 and enhances the surface cooling by a few tenths of K due to increased surface shielding from solar radiation. Doubling of sulfur emissions induces a substantial increase in radiative forcing (up to -7 to -8 W/m2) and associated surface cooling. With doubled sulfur emissions, the surface cooling exceeds -1 K and is statistically significant at the 90% confidence level over various areas of China. The aerosol forcing and surface cooling tend to inhibit precipitation over the region, although this effect is relatively small in the simulations. Some features of the simulated aerosol-induced cooling are consistent with temperature trends observed in recent decades over different regions of China.

  19. Bayesian calibration of coarse-grained forces: Efficiently addressing transferability

    NASA Astrophysics Data System (ADS)

    Patrone, Paul N.; Rosch, Thomas W.; Phelan, Frederick R.

    2016-04-01

    Generating and calibrating forces that are transferable across a range of state-points remains a challenging task in coarse-grained (CG) molecular dynamics. In this work, we present a coarse-graining workflow, inspired by ideas from uncertainty quantification and numerical analysis, to address this problem. The key idea behind our approach is to introduce a Bayesian correction algorithm that uses functional derivatives of CG simulations to rapidly and inexpensively recalibrate initial estimates f0 of forces anchored by standard methods such as force-matching. Taking density-temperature relationships as a running example, we demonstrate that this algorithm, in concert with various interpolation schemes, can be used to efficiently compute physically reasonable force curves on a fine grid of state-points. Importantly, we show that our workflow is robust to several choices available to the modeler, including the interpolation schemes and tools used to construct f0. In a related vein, we also demonstrate that our approach can speed up coarse-graining by reducing the number of atomistic simulations needed as inputs to standard methods for generating CG forces.

  20. Bayesian calibration of coarse-grained forces: Efficiently addressing transferability.

    PubMed

    Patrone, Paul N; Rosch, Thomas W; Phelan, Frederick R

    2016-04-21

    Generating and calibrating forces that are transferable across a range of state-points remains a challenging task in coarse-grained (CG) molecular dynamics. In this work, we present a coarse-graining workflow, inspired by ideas from uncertainty quantification and numerical analysis, to address this problem. The key idea behind our approach is to introduce a Bayesian correction algorithm that uses functional derivatives of CG simulations to rapidly and inexpensively recalibrate initial estimates f0 of forces anchored by standard methods such as force-matching. Taking density-temperature relationships as a running example, we demonstrate that this algorithm, in concert with various interpolation schemes, can be used to efficiently compute physically reasonable force curves on a fine grid of state-points. Importantly, we show that our workflow is robust to several choices available to the modeler, including the interpolation schemes and tools used to construct f0. In a related vein, we also demonstrate that our approach can speed up coarse-graining by reducing the number of atomistic simulations needed as inputs to standard methods for generating CG forces.

  1. Overview of the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Forcing on the Mediterranean Climate (ChArMEx/ADRIMED) summer 2013 campaign

    NASA Astrophysics Data System (ADS)

    Mallet, M.; Dulac, F.; Formenti, P.; Nabat, P.; Sciare, J.; Roberts, G.; Pelon, J.; Ancellet, G.; Tanré, D.; Parol, F.; di Sarra, A.; Alados, L.; Arndt, J.; Auriol, F.; Blarel, L.; Bourrianne, T.; Brogniez, G.; Chazette, P.; Chevaillier, S.; Claeys, M.; D'Anna, B.; Denjean, C.; Derimian, Y.; Desboeufs, K.; Di Iorio, T.; Doussin, J.-F.; Durand, P.; Féron, A.; Freney, E.; Gaimoz, C.; Goloub, P.; Gómez-Amo, J. L.; Granados-Muñoz, M. J.; Grand, N.; Hamonou, E.; Jankowiak, I.; Jeannot, M.; Léon, J.-F.; Maillé, M.; Mailler, S.; Meloni, D.; Menut, L.; Momboisse, G.; Nicolas, J.; Podvin, J.; Pont, V.; Rea, G.; Renard, J.-B.; Roblou, L.; Schepanski, K.; Schwarzenboeck, A.; Sellegri, K.; Sicard, M.; Solmon, F.; Somot, S.; Torres, B.; Totems, J.; Triquet, S.; Verdier, N.; Verwaerde, C.; Wenger, J.; Zapf, P.

    2015-07-01

    The Chemistry-Aerosol Mediterranean Experiment (ChArMEx; http://charmex.lsce.ipsl.fr) is a collaborative research program federating international activities to investigate Mediterranean regional chemistry-climate interactions. A special observing period (SOP-1a) including intensive airborne measurements was performed in the framework of the Aerosol Direct Radiative Forcing on the Mediterranean Climate (ADRIMED) project during the Mediterranean dry season over the western and central Mediterranean basins, with a focus on aerosol-radiation measurements and their modeling. The SOP-1a took place from 11 June to 5 July 2013. Airborne measurements were made by both the ATR-42 and F-20 French research aircraft operated from Sardinia (Italy) and instrumented for in situ and remote-sensing measurements, respectively, and by sounding and drifting balloons, launched in Minorca. The experimental set-up also involved several ground-based measurement sites on islands including two ground-based reference stations in Corsica and Lampedusa and secondary monitoring sites in Minorca and Sicily. Additional measurements including lidar profiling were also performed on alert during aircraft operations at EARLINET/ACTRIS stations at Granada and Barcelona in Spain, and in southern Italy. Remote sensing aerosol products from satellites (MSG/SEVIRI, MODIS) and from the AERONET/PHOTONS network were also used. Dedicated meso-scale and regional modelling experiments were performed in relation to this observational effort. We provide here an overview of the different surface and aircraft observations deployed during the ChArMEx/ADRIMED period and of associated modeling studies together with an analysis of the synoptic conditions that determined the aerosol emission and transport. Meteorological conditions observed during this campaign (moderate temperatures and southern flows) were not favorable to produce high level of atmospheric pollutants nor

  2. A global model simulation of present and future nitrate aerosols and their direct radiative forcing of climate

    NASA Astrophysics Data System (ADS)

    Hauglustaine, D. A.; Balkanski, Y.; Schulz, M.

    2014-03-01

    The ammonia cycle and nitrate particle formation have been introduced in the LMDz-INCA global model. Both fine nitrate particles formation in the accumulation mode and coarse nitrate forming on existing dust and sea-salt particles are considered. The model simulates distributions of nitrates and related species in agreement with previous studies and observations. The calculated present-day total nitrate direct radiative forcing since the pre-industrial is -0.056 W m-2. This forcing has the same magnitude than the forcing associated with organic carbon particles and represents 18% of the sulfate forcing. Fine particles largely dominate the nitrate forcing representing close to 90% of this value. The model has been used to investigate the future changes in nitrates and direct radiative forcing of climate based on snapshot simulations for the four Representative Concentration Pathway (RCP) scenarios and for the 2030, 2050 and 2100 time horizons. Due to a decrease in fossil fuel emissions in the future, the concentrations of most of the species involved in the nitrate-ammonium-sulfate system drop by 2100 except for ammonia which originates from agricultural practices and for which emissions significantly increase in the future. Despite the decrease of nitrate surface levels in Europe and Northern America, the global burden of accumulation mode nitrates increases by up to a factor of 2.6 in 2100. This increase in nitrate in the future arises despite decreasing NOx emissions due to increased availability of ammonia to form ammonium nitrate. The total aerosol direct forcing decreases from its present-day value of -0.234 W m-2 to a range of -0.070 to -0.130 W m-2 in 2100 based on the considered scenario. The direct forcing decreases for all aerosols except for nitrates for which the direct negative forcing increases to a range of -0.060 to -0.115 W m-2 in 2100. Including nitrates in the radiative forcing calculations increases the total direct forcing of aerosols by a

  3. Efficient formation of stratospheric aerosol for climate engineering by emission of condensible vapor from aircraft

    NASA Astrophysics Data System (ADS)

    Pierce, Jeffrey R.; Weisenstein, Debra K.; Heckendorn, Patricia; Peter, Thomas; Keith, David W.

    2010-09-01

    Recent analysis suggests that the effectiveness of stratospheric aerosol climate engineering through emission of non-condensable vapors such as SO2 is limited because the slow conversion to H2SO4 tends to produce aerosol particles that are too large; SO2 injection may be so inefficient that it is difficult to counteract the radiative forcing due to a CO2 doubling. Here we describe an alternate method in which aerosol is formed rapidly in the plume following injection of H2SO4, a condensable vapor, from an aircraft. This method gives better control of particle size and can produce larger radiative forcing with lower sulfur loadings than SO2 injection. Relative to SO2 injection, it may reduce some of the adverse effects of geoengineering such as radiative heating of the lower stratosphere. This method does not, however, alter the fact that such a geoengineered radiative forcing can, at best, only partially compensate for the climate changes produced by CO2.

  4. Efficient Formation of Stratospheric Aerosol for Climate Engineering by Emission of Condensible Vapor from Aircraft

    NASA Technical Reports Server (NTRS)

    Pierce, Jeffrey R.; Weisenstein, Debra K.; Heckendorn, Patricia; Peter. Thomas; Keith, David W.

    2010-01-01

    Recent analysis suggests that the effectiveness of stratospheric aerosol climate engineering through emission of non-condensable vapors such as SO2 is limited because the slow conversion to H2SO4 tends to produce aerosol particles that are too large; SO2 injection may be so inefficient that it is difficult to counteract the radiative forcing due to a CO2 doubling. Here we describe an alternate method in which aerosol is formed rapidly in the plume following injection of H2SO4, a condensable vapor, from an aircraft. This method gives better control of particle size and can produce larger radiative forcing with lower sulfur loadings than SO2 injection. Relative to SO2 injection, it may reduce some of the adverse effects of geoengineering such as radiative heating of the lower stratosphere. This method does not, however, alter the fact that such a geoengineered radiative forcing can, at best, only partially compensate for the climate changes produced by CO2.

  5. Placement and efficiency effects on radiative forcing of solar installations

    NASA Astrophysics Data System (ADS)

    Burg, Brian R.; Ruch, Patrick; Paredes, Stephan; Michel, Bruno

    2015-09-01

    The promise for harnessing solar energy being hampered by cost, triggered efforts to reduce them. As a consequence low-efficiency, low-cost photovoltaics (PV) panels prevail. Conversely, in the traditional energy sector efficiency is extremely important due to the direct costs associated to fuels. This also affects solar energy due to the radiative forcing caused by the dark solar panels. In this paper we extend the concept of energy payback time by including the effect of albedo change, which gives a better assessment of the system sustainability. We present an analysis on the short and medium term climate forcing effects of different solar collectors in Riyadh, Saudi Arabia and demonstrate that efficiency is important to reduce the collector area and cost. This also influences the embodied energy and the global warming potential. We show that a placement of a high concentration photovoltaic thermal solar power station outside of the city using a district cooling system has a double beneficial effect since it improves the solar conversion efficiency and reduces the energy demand for cooling in the city. We also explain the mechanisms of the current economic development of solar technologies and anticipate changes.

  6. Placement and efficiency effects on radiative forcing of solar installations

    SciTech Connect

    Burg, Brian R.; Ruch, Patrick; Paredes, Stephan; Michel, Bruno

    2015-09-28

    The promise for harnessing solar energy being hampered by cost, triggered efforts to reduce them. As a consequence low-efficiency, low-cost photovoltaics (PV) panels prevail. Conversely, in the traditional energy sector efficiency is extremely important due to the direct costs associated to fuels. This also affects solar energy due to the radiative forcing caused by the dark solar panels. In this paper we extend the concept of energy payback time by including the effect of albedo change, which gives a better assessment of the system sustainability. We present an analysis on the short and medium term climate forcing effects of different solar collectors in Riyadh, Saudi Arabia and demonstrate that efficiency is important to reduce the collector area and cost. This also influences the embodied energy and the global warming potential. We show that a placement of a high concentration photovoltaic thermal solar power station outside of the city using a district cooling system has a double beneficial effect since it improves the solar conversion efficiency and reduces the energy demand for cooling in the city. We also explain the mechanisms of the current economic development of solar technologies and anticipate changes.

  7. Efficient Nose-to-Lung (N2L) Aerosol Delivery with a Dry Powder Inhaler

    PubMed Central

    Golshahi, Laleh; Behara, Srinivas R.B.; Tian, Geng; Farkas, Dale R.; Hindle, Michael

    2015-01-01

    Abstract Purpose: Delivering aerosols to the lungs through the nasal route has a number of advantages, but its use has been limited by high depositional loss in the extrathoracic airways. The objective of this study was to evaluate the nose-to-lung (N2L) delivery of excipient enhanced growth (EEG) formulation aerosols generated with a new inline dry powder inhaler (DPI). The device was also adapted to enable aerosol delivery to a patient simultaneously receiving respiratory support from high flow nasal cannula (HFNC) therapy. Methods: The inhaler delivered the antibiotic ciprofloxacin, which was formulated as submicrometer combination particles containing a hygroscopic excipient prepared by spray-drying. Nose-to-lung delivery was assessed using in vitro and computational fluid dynamics (CFD) methods in an airway model that continued through the upper tracheobronchial region. Results: The best performing device contained a 2.3 mm flow control orifice and a 3D rod array with a 3-4-3 rod pattern. Based on in vitro experiments, the emitted dose from the streamlined nasal cannula had a fine particle fraction <5 μm of 95.9% and mass median aerodynamic diameter of 1.4 μm, which was considered ideal for nose-to-lung EEG delivery. With the 2.3-343 device, condensational growth in the airways increased the aerosol size to 2.5–2.7 μm and extrathoracic deposition was <10%. CFD results closely matched the in vitro experiments and predicted that nasal deposition was <2%. Conclusions: The developed DPI produced high efficiency aerosolization with significant size increase of the aerosol within the airways that can be used to enable nose-to-lung delivery and aerosol administration during HFNC therapy. PMID:25192072

  8. Radiative Forcing Due to Enhancements in Tropospheric Ozone and Carbonaceous Aerosols Caused by Asian Fires During Spring 2008

    NASA Technical Reports Server (NTRS)

    Natarajan, Murali; Pierce, R. Bradley; Lenzen, Allen J.; Al-Saadi, Jassim A.; Soja, Amber J.; Charlock, Thomas P.; Rose, Fred G.; Winker, David M.; Worden, John R.

    2012-01-01

    Simulations of tropospheric ozone and carbonaceous aerosol distributions, conducted with the Real-time Air Quality Modeling System (RAQMS), are used to study the effects of major outbreaks of fires that occurred in three regions of Asia, namely Thailand, Kazakhstan, and Siberia, during spring 2008. RAQMS is a global scale meteorological and chemical modeling system. Results from these simulations, averaged over April 2008, indicate that tropospheric ozone column increases by more than 10 Dobson units (DU) near the Thailand region, and by lesser amounts in the other regions due to the fires. Widespread increases in the optical depths of organic and black carbon aerosols are also noted. We have used an off-line radiative transfer model to evaluate the direct radiative forcing due to the fire-induced changes in atmospheric composition. For clear sky, the monthly averaged radiative forcing at the top of the atmosphere (TOA) is mostly negative with peak values less than -12 W/sq m occurring near the fire regions. The negative forcing represents the increased outgoing shortwave radiation caused by scattering due to carbonaceous aerosols. At high latitudes, the radiative forcing is positive due to the presence of absorbing aerosols over regions of high surface albedo. Regions of positive forcing at TOA are more pronounced under total sky conditions. The monthly averaged radiative forcing at the surface is mostly negative, and peak values of less than -30 W/sq m occur near the fire regions. Persistently large negative forcing at the surface could alter the surface energy budget and potentially weaken the hydrological cycle.

  9. Timing, global aerosol forcing, and climate impact of volcanic eruptions during the Common Era

    NASA Astrophysics Data System (ADS)

    Sigl, Michael; McConnell, Joseph R.; Winstrup, Mai; Welten, Kees C.; Plunkett, Gill; Ludlow, Francis; Toohey, Matthew; Büntgen, Ulf; Caffee, Marc; Kipfstuhl, Sepp; Kostick, Conor; Krüger, Kirstin; Maselli, Olivia J.; Mulvaney, Robert; Woodruff, Thomas E.

    2015-04-01

    Early documentary records report of a mysterious dust cloud that was covering Europe for 12 months in 536-37 CE, which was followed by climatic downturn and societal decline globally. Tree rings and other climate proxies have corroborated the occurrence of this event as well as characterized its extent and duration, but failed to trace its origin. By using a multi-disciplinary approach that integrates novel, global-scale age markers with state-of-the-art continuous ice core aerosol measurements, automated objective ice-core layer counting, tephra analyses, and detailed examination of historical archives, we developed an accurate volcanic forcing series from bipolar ice-core arrays back into early Roman times. Our study reconciles human and natural archives - demonstrated by the synchronicity of major volcanic eruption dates to historical documentary records and the now consistent response of tree-ring-reconstructed cooling extremes occurring in the immediate aftermath of large volcanic eruptions throughout the past 2,000 years. These findings have significant implications in multiple research fields including (1) quantification and attribution of climate variations to external solar and volcanic forcing and (2) improvement of reconstructions of climate variations from multi-proxy networks comprising tree-ring and/or ice-core data (e.g., PAGES 2k).

  10. Long-term variations in the South Asian monsoon annual cycle: the role of regional anthropogenic aerosol forcing

    NASA Astrophysics Data System (ADS)

    Bollasina, Massimo; Ming, Yi

    2013-04-01

    Detection and attribution of long-term variations of the South Asian monsoon is of extreme importance. Indeed, even small changes in the onset and duration of the monsoon season or in the spatial distribution of the seasonal mean precipitation may severely impact agriculture, health, water availability, ecosystems, and economy for a substantial fraction of the world's population. In the past decades emissions of aerosols have dramatically increased over South Asia due to rapid urbanization and population growth. As a result, the study of the impact of anthropogenic aerosols on the monsoon has recently emerged as one of the topics of highest priority in the scientific community. This study makes use of a state-of-the-art coupled climate model, the GFDL CM3, to investigate two aspects of the aerosol influence on the 20th-century changes in the monsoon. The model has fully-interactive aerosols and a representation of both direct and indirect effects. Aerosols are responsible for the advancement of the monsoon onset over India, leading, in agreement with observations, to enhanced precipitation in June over most parts of the subcontinent. Our experiments show that the earlier onset is preceded in early spring by a strong aerosol forcing over the Bay of Bengal and Indonesia and associated atmospheric circulation anomalies. The latter triggers thermodynamical changes over the northwestern part of the Subcontinent in May and June, including enhanced surface heating, which in turn drive the movement of the monsoon to the west. We also performed historical experiments with time-evolving radiative forcings aimed at isolating the contribution of regional versus remote anthropogenic aerosol emissions on the observed 20th century widespread drying of the Indian monsoon. Indian-only aerosol sources are found to play a predominant role in generating suppressed rainfall over the subcontinent, especially during early summer. Remote aerosols contribute, although in a minor way, to

  11. Efficient parametrization of complex molecule-surface force fields.

    PubMed

    Gao, David Z; Federici Canova, Filippo; Watkins, Matthew B; Shluger, Alexander L

    2015-06-15

    We present an efficient scheme for parametrizing complex molecule-surface force fields from ab initio data. The cost of producing a sufficient fitting library is mitigated using a 2D periodic embedded slab model made possible by the quantum mechanics/molecular mechanics scheme in CP2K. These results were then used in conjunction with genetic algorithm (GA) methods to optimize the large parameter sets needed to describe such systems. The derived potentials are able to well reproduce adsorption geometries and adsorption energies calculated using density functional theory. Finally, we discuss the challenges in creating a sufficient fitting library, determining whether or not the GA optimization has completed, and the transferability of such force fields to similar molecules.

  12. Efficient parametrization of complex molecule-surface force fields.

    PubMed

    Gao, David Z; Federici Canova, Filippo; Watkins, Matthew B; Shluger, Alexander L

    2015-06-15

    We present an efficient scheme for parametrizing complex molecule-surface force fields from ab initio data. The cost of producing a sufficient fitting library is mitigated using a 2D periodic embedded slab model made possible by the quantum mechanics/molecular mechanics scheme in CP2K. These results were then used in conjunction with genetic algorithm (GA) methods to optimize the large parameter sets needed to describe such systems. The derived potentials are able to well reproduce adsorption geometries and adsorption energies calculated using density functional theory. Finally, we discuss the challenges in creating a sufficient fitting library, determining whether or not the GA optimization has completed, and the transferability of such force fields to similar molecules. PMID:25891018

  13. Modelling multi-component aerosol transport problems by the efficient splitting characteristic method

    NASA Astrophysics Data System (ADS)

    Liang, Dong; Fu, Kai; Wang, Wenqia

    2016-11-01

    In this paper, a splitting characteristic method is developed for solving general multi-component aerosol transports in atmosphere, which can efficiently compute the aerosol transports by using large time step sizes. The proposed characteristic finite difference method (C-FDM) can solve the multi-component aerosol distributions in high dimensional domains over large ranges of concentrations and for different aerosol types. The C-FDM is first tested to compute the moving of a Gaussian concentration hump. Comparing with the Runge-Kutta method (RKM), our C-FDM can use very large time step sizes. Using Δt = 0.1, the accuracy of our C-FDM is 10-4, but the RKM only gets the accuracy of 10-2 using a small Δt = 0.01 and the accuracy of 10-3 even using a much smaller Δt = 0.002. A simulation of sulfate transport in a varying wind field is then carried out by the splitting C-FDM, where the sulfate pollution is numerically showed expanding along the wind direction and the effects of the different time step sizes and different wind speeds are analyzed. Further, a realistic multi-component aerosol transport over an area in northeastern United States is studied. Concentrations of PM2.5 sulfate, ammonium, nitrate are high in the urban area, and low in the marine area, while sea salts of sodium and chloride mainly exist in the marine area. The normalized mean bias and the normalized mean error of the predicted PM2.5 concentrations are -6.5% and 24.1% compared to the observed data measured at monitor stations. The time series of numerical aerosol concentration distribution show that the strong winds can move the aerosol concentration peaks horizontally for a long distance, such as from the urban area to the rural area and from the marine area to the urban and rural area. Moreover, we also show the numerical time duration patterns of the aerosol concentration distributions due to the affections of the turbulence and the deposition removal. The developed splitting C-FDM algorithm

  14. Spatial variations in immediate greenhouse gases and aerosol emissions and resulting radiative forcing from wildfires in interior Alaska

    NASA Astrophysics Data System (ADS)

    Huang, Shengli; Liu, Heping; Dahal, Devendra; Jin, Suming; Li, Shuang; Liu, Shuguang

    2016-02-01

    Boreal fires can cool the climate; however, this conclusion came from individual fires and may not represent the whole story. We hypothesize that the climatic impact of boreal fires depends on local landscape heterogeneity such as burn severity, prefire vegetation type, and soil properties. To test this hypothesis, spatially explicit emission of greenhouse gases (GHGs) and aerosols and their resulting radiative forcing are required as an important and necessary component towards a full assessment. In this study, we integrated remote sensing (Landsat and MODIS) and models (carbon consumption model, emission factors model, and radiative forcing model) to calculate the carbon consumption, GHGs and aerosol emissions, and their radiative forcing of 2001-2010 fires at 30 m resolution in the Yukon River Basin of Alaska. Total carbon consumption showed significant spatial variation, with a mean of 2,615 g C m-2 and a standard deviation of 2,589 g C m-2. The carbon consumption led to different amounts of GHGs and aerosol emissions, ranging from 593.26 Tg (CO2) to 0.16 Tg (N2O). When converted to equivalent CO2 based on global warming potential metric, the maximum 20 years equivalent CO2 was black carbon (713.77 Tg), and the lowest 20 years equivalent CO2 was organic carbon (-583.13 Tg). The resulting radiative forcing also showed significant spatial variation: CO2, CH4, and N2O can cause a 20-year mean radiative forcing of 7.41 W m-2 with a standard deviation of 2.87 W m-2. This emission forcing heterogeneity indicates that different boreal fires have different climatic impacts. When considering the spatial variation of other forcings, such as surface shortwave forcing, we may conclude that some boreal fires, especially boreal deciduous fires, can warm the climate.

  15. Influence of the vertical absorption profile of mixed Asian dust plumes on aerosol direct radiative forcing over East Asia

    NASA Astrophysics Data System (ADS)

    Noh, Young Min; Lee, Kwonho; Kim, Kwanchul; Shin, Sung-Kyun; Müller, Detlef; Shin, Dong Ho

    2016-08-01

    We estimate the aerosol direct radiative forcing (ADRF) and heating rate profiles of mixed East Asian dust plumes in the solar wavelength region ranging from 0.25 to 4.0 μm using the Santa Barbara Discrete Ordinate Atmospheric Radiative Transfer (SBDART) code. Vertical profiles of aerosol extinction coefficients and single-scattering albedos (SSA) were derived from measurements with a multi-wavelength Raman lidar system. The data are used as input parameters for our radiative transfer calculations. We considered four cases of radiative forcing in SBDART: 1. dust, 2. pollution, 3. mixed dust plume and the use of vertical profiles of SSA, and 4. mixed dust plumes and the use of column-averaged values of SSA. In our sensitivity study we examined the influence of SSA and aerosol layer height on our results. The ADRF at the surface and in the atmosphere shows a small dependence on the specific shape of the aerosol extinction vertical profile and its light-absorption property for all four cases. In contrast, at the top of the atmosphere (TOA), the ADRF is largely affected by the vertical distribution of the aerosols extinction. This effect increases if the light-absorption capacity (decrease of SSA) of the aerosols increases. We find different radiative effects in situations in which two layers of aerosols had different light-absorption properties. The largest difference was observed at the TOA for an absorbing aerosol layer at high altitude in which we considered in one case the vertical profile of SSA and in another case the column-averaged SSA only. The ADRF at the TOA increases when the light-absorbing aerosol layer is located above 3 km altitude. The differences between height-resolved SSA, which can be obtained from lidar data, and total layer-mean SSA indicates that the use of a layer-mean SSA can be rather misleading as it can induce a large error in the calculation of the ADRF at the TOA, which in turn may cause errors in the vertical profiles of heating rates.

  16. Overview of the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Forcing on the Mediterranean Climate (ChArMEx/ADRIMED) summer 2013 campaign

    NASA Astrophysics Data System (ADS)

    Mallet, M.; Dulac, F.; Formenti, P.; Nabat, P.; Sciare, J.; Roberts, G.; Pelon, J.; Ancellet, G.; Tanré, D.; Parol, F.; Denjean, C.; Brogniez, G.; di Sarra, A.; Alados-Arboledas, L.; Arndt, J.; Auriol, F.; Blarel, L.; Bourrianne, T.; Chazette, P.; Chevaillier, S.; Claeys, M.; D'Anna, B.; Derimian, Y.; Desboeufs, K.; Di Iorio, T.; Doussin, J.-F.; Durand, P.; Féron, A.; Freney, E.; Gaimoz, C.; Goloub, P.; Gómez-Amo, J. L.; Granados-Muñoz, M. J.; Grand, N.; Hamonou, E.; Jankowiak, I.; Jeannot, M.; Léon, J.-F.; Maillé, M.; Mailler, S.; Meloni, D.; Menut, L.; Momboisse, G.; Nicolas, J.; Podvin, T.; Pont, V.; Rea, G.; Renard, J.-B.; Roblou, L.; Schepanski, K.; Schwarzenboeck, A.; Sellegri, K.; Sicard, M.; Solmon, F.; Somot, S.; Torres, B.; Totems, J.; Triquet, S.; Verdier, N.; Verwaerde, C.; Waquet, F.; Wenger, J.; Zapf, P.

    2016-01-01

    MBL. In terms of shortwave (SW) direct forcing, in situ surface and aircraft observations have been merged and used as inputs in 1-D radiative transfer codes for calculating the aerosol direct radiative forcing (DRF). Results show significant surface SW instantaneous forcing (up to -90 W m-2 at noon). Aircraft observations provide also original estimates of the vertical structure of SW and LW radiative heating revealing significant instantaneous values of about 5° K per day in the solar spectrum (for a solar angle of 30°) within the dust layer. Associated 3-D modeling studies from regional climate (RCM) and chemistry transport (CTM) models indicate a relatively good agreement for simulated AOD compared with observations from the AERONET/PHOTONS network and satellite data, especially for long-range dust transport. Calculations of the 3-D SW (clear-sky) surface DRF indicate an average of about -10 to -20 W m-2 (for the whole period) over the Mediterranean Sea together with maxima (-50 W m-2) over northern Africa. The top of the atmosphere (TOA) DRF is shown to be highly variable within the domain, due to moderate absorbing properties of dust and changes in the surface albedo. Indeed, 3-D simulations indicate negative forcing over the Mediterranean Sea and Europe and positive forcing over northern Africa. Finally, a multi-year simulation, performed for the 2003 to 2009 period and including an ocean-atmosphere (O-A) coupling, underlines the impact of the aerosol direct radiative forcing on the sea surface temperature, O-A fluxes and the hydrological cycle over the Mediterranean.

  17. Solid versus Liquid Particle Sampling Efficiency of Three Personal Aerosol Samplers when Facing the Wind

    PubMed Central

    Koehler, Kirsten A.; Anthony, T. Renee; Van Dyke, Michael

    2016-01-01

    The objective of this study was to examine the facing-the-wind sampling efficiency of three personal aerosol samplers as a function of particle phase (solid versus liquid). Samplers examined were the IOM, Button, and a prototype personal high-flow inhalable sampler head (PHISH). The prototype PHISH was designed to interface with the 37-mm closed-face cassette and provide an inhalable sample at 10 l min−1 of flow. Increased flow rate increases the amount of mass collected during a typical work shift and helps to ensure that limits of detection are met, particularly for well-controlled but highly toxic species. Two PHISH prototypes were tested: one with a screened inlet and one with a single-pore open-face inlet. Personal aerosol samplers were tested on a bluff-body disc that was rotated along the facing-the-wind axis to reduce spatiotemporal variability associated with sampling supermicron aerosol in low-velocity wind tunnels. When compared to published data for facing-wind aspiration efficiency for a mouth-breathing mannequin, the IOM oversampled relative to mannequin facing-the-wind aspiration efficiency for all sizes and particle types (solid and liquid). The sampling efficiency of the Button sampler was closer to the mannequin facing-the-wind aspiration efficiency than the IOM for solid particles, but the screened inlet removed most liquid particles, resulting in a large underestimation compared to the mannequin facing-the-wind aspiration efficiency. The open-face PHISH results showed overestimation for solid particles and underestimation for liquid particles when compared to the mannequin facing-the-wind aspiration efficiency. Substantial (and statistically significant) differences in sampling efficiency were observed between liquid and solid particles, particularly for the Button and screened-PHISH, with a majority of aerosol mass depositing on the screened inlets of these samplers. Our results suggest that large droplets have low penetration efficiencies

  18. Anthropogenic Aerosol Forcing as Indicated by the Reversion of Warming-elevation Relationship

    NASA Astrophysics Data System (ADS)

    Zeng, Z.; Chen, A.; Ciais, P.; Li, Y.; Li, L. Z. X.; Vautard, R.; Zhou, L.; Yang, H.; Huang, M.; Piao, S.

    2015-12-01

    Global climate models prescribed with increasing greenhouse gases (GHGs) produce warming trends that increase with altitude. However, observations do not show a uniform acceleration of warming with elevation. Here, we explore warming-elevation relationship, apply records from 2660 meteorological stations, and determine that the vertical gradient of warming rate varies with location. Warming is faster at higher altitude in Asia and western North America, but the opposite is observed over central Europe and eastern North America which have received more short-wave radiation (brightening) associated with a decrease of aerosols and clouds since the 1980s. We found that altitudinal differences in air pollution brightening, with observations showing more short-wave radiation received at low altitudes than at mountain stations, modulate the otherwise uniform effect of the long-wave forcing of GHGs on the warming-elevation relationship. Characterizing the warming-elevation relationships over different mountainous regions thus provides a valuable tool for understanding the drivers of regional climate change and will contribute to the formulation of strategies for climate change mitigation (e.g., biodiversity conservation) at high elevations.

  19. Overview of the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Forcing on the Mediterranean Climate (ChArMEx/ADRIMED) summer 2013 campaign

    NASA Astrophysics Data System (ADS)

    Mallet, M.; Dulac, F.; Formenti, P.; Nabat, P.; Sciare, J.; Roberts, G.; Pelon, J.; Ancellet, G.; Tanré, D.; Parol, F.; Denjean, C.; Brogniez, G.; di Sarra, A.; Alados-Arboledas, L.; Arndt, J.; Auriol, F.; Blarel, L.; Bourrianne, T.; Chazette, P.; Chevaillier, S.; Claeys, M.; D'Anna, B.; Derimian, Y.; Desboeufs, K.; Di Iorio, T.; Doussin, J.-F.; Durand, P.; Féron, A.; Freney, E.; Gaimoz, C.; Goloub, P.; Gómez-Amo, J. L.; Granados-Muñoz, M. J.; Grand, N.; Hamonou, E.; Jankowiak, I.; Jeannot, M.; Léon, J.-F.; Maillé, M.; Mailler, S.; Meloni, D.; Menut, L.; Momboisse, G.; Nicolas, J.; Podvin, T.; Pont, V.; Rea, G.; Renard, J.-B.; Roblou, L.; Schepanski, K.; Schwarzenboeck, A.; Sellegri, K.; Sicard, M.; Solmon, F.; Somot, S.; Torres, B.; Totems, J.; Triquet, S.; Verdier, N.; Verwaerde, C.; Waquet, F.; Wenger, J.; Zapf, P.

    2016-01-01

    The Chemistry-Aerosol Mediterranean Experiment (ChArMEx; http://charmex.lsce.ipsl.fr) is a collaborative research program federating international activities to investigate Mediterranean regional chemistry-climate interactions. A special observing period (SOP-1a) including intensive airborne measurements was performed in the framework of the Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region (ADRIMED) project during the Mediterranean dry season over the western and central Mediterranean basins, with a focus on aerosol-radiation measurements and their modeling. The SOP-1a took place from 11 June to 5 July 2013. Airborne measurements were made by both the ATR-42 and F-20 French research aircraft operated from Sardinia (Italy) and instrumented for in situ and remote-sensing measurements, respectively, and by sounding and drifting balloons, launched in Minorca. The experimental setup also involved several ground-based measurement sites on islands including two ground-based reference stations in Corsica and Lampedusa and secondary monitoring sites in Minorca and Sicily. Additional measurements including lidar profiling were also performed on alert during aircraft operations at EARLINET/ACTRIS stations at Granada and Barcelona in Spain, and in southern Italy. Remote-sensing aerosol products from satellites (MSG/SEVIRI, MODIS) and from the AERONET/PHOTONS network were also used. Dedicated meso-scale and regional modeling experiments were performed in relation to this observational effort. We provide here an overview of the different surface and aircraft observations deployed during the ChArMEx/ADRIMED period and of associated modeling studies together with an analysis of the synoptic conditions that determined the aerosol emission and transport. Meteorological conditions observed during this campaign (moderate temperatures and southern flows) were not favorable to producing high

  20. A Fast and Efficient Version of the TwO-Moment Aerosol Sectional (TOMAS) Global Aerosol Microphysics Model

    NASA Technical Reports Server (NTRS)

    Lee, Yunha; Adams, P. J.

    2012-01-01

    This study develops more computationally efficient versions of the TwO-Moment Aerosol Sectional (TOMAS) microphysics algorithms, collectively called Fast TOMAS. Several methods for speeding up the algorithm were attempted, but only reducing the number of size sections was adopted. Fast TOMAS models, coupled to the GISS GCM II-prime, require a new coagulation algorithm with less restrictive size resolution assumptions but only minor changes in other processes. Fast TOMAS models have been evaluated in a box model against analytical solutions of coagulation and condensation and in a 3-D model against the original TOMAS (TOMAS-30) model. Condensation and coagulation in the Fast TOMAS models agree well with the analytical solution but show slightly more bias than the TOMAS-30 box model. In the 3-D model, errors resulting from decreased size resolution in each process (i.e., emissions, cloud processing wet deposition, microphysics) are quantified in a series of model sensitivity simulations. Errors resulting from lower size resolution in condensation and coagulation, defined as the microphysics error, affect number and mass concentrations by only a few percent. The microphysics error in CN70CN100 (number concentrations of particles larger than 70100 nm diameter), proxies for cloud condensation nuclei, range from 5 to 5 in most regions. The largest errors are associated with decreasing the size resolution in the cloud processing wet deposition calculations, defined as cloud-processing error, and range from 20 to 15 in most regions for CN70CN100 concentrations. Overall, the Fast TOMAS models increase the computational speed by 2 to 3 times with only small numerical errors stemming from condensation and coagulation calculations when compared to TOMAS-30. The faster versions of the TOMAS model allow for the longer, multi-year simulations required to assess aerosol effects on cloud lifetime and precipitation.

  1. Overview of the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Forcing on the Mediterranean Climate (ChArMEx/ADRIMED) summer 2013 campaign

    NASA Astrophysics Data System (ADS)

    Mallet, M.; Dulac, F.; Formenti, P.; Nabat, P.; Sciare, J.; Roberts, G.; Pelon, J.; Ancellet, G.; Tanré, D.; Parol, F.; di Sarra, A.; Alados, L.; Arndt, J.; Auriol, F.; Blarel, L.; Bourrianne, T.; Brogniez, G.; Chazette, P.; Chevaillier, S.; Claeys, M.; D'Anna, B.; Denjean, C.; Derimian, Y.; Desboeufs, K.; Di Iorio, T.; Doussin, J.-F.; Durand, P.; Féron, A.; Freney, E.; Gaimoz, C.; Goloub, P.; Gómez-Amo, J. L.; Granados-Muñoz, M. J.; Grand, N.; Hamonou, E.; Jankowiak, I.; Jeannot, M.; Léon, J.-F.; Maillé, M.; Mailler, S.; Meloni, D.; Menut, L.; Momboisse, G.; Nicolas, J.; Podvin, J.; Pont, V.; Rea, G.; Renard, J.-B.; Roblou, L.; Schepanski, K.; Schwarzenboeck, A.; Sellegri, K.; Sicard, M.; Solmon, F.; Somot, S.; Torres, B.; Totems, J.; Triquet, S.; Verdier, N.; Verwaerde, C.; Wenger, J.; Zapf, P.

    2015-07-01

    The Chemistry-Aerosol Mediterranean Experiment (ChArMEx; http://charmex.lsce.ipsl.fr) is a collaborative research program federating international activities to investigate Mediterranean regional chemistry-climate interactions. A special observing period (SOP-1a) including intensive airborne measurements was performed in the framework of the Aerosol Direct Radiative Forcing on the Mediterranean Climate (ADRIMED) project during the Mediterranean dry season over the western and central Mediterranean basins, with a focus on aerosol-radiation measurements and their modeling. The SOP-1a took place from 11 June to 5 July 2013. Airborne measurements were made by both the ATR-42 and F-20 French research aircraft operated from Sardinia (Italy) and instrumented for in situ and remote-sensing measurements, respectively, and by sounding and drifting balloons, launched in Minorca. The experimental set-up also involved several ground-based measurement sites on islands including two ground-based reference stations in Corsica and Lampedusa and secondary monitoring sites in Minorca and Sicily. Additional measurements including lidar profiling were also performed on alert during aircraft operations at EARLINET/ACTRIS stations at Granada and Barcelona in Spain, and in southern Italy. Remote sensing aerosol products from satellites (MSG/SEVIRI, MODIS) and from the AERONET/PHOTONS network were also used. Dedicated meso-scale and regional modelling experiments were performed in relation to this observational effort. We provide here an overview of the different surface and aircraft observations deployed during the ChArMEx/ADRIMED period and of associated modeling studies together with an analysis of the synoptic conditions that determined the aerosol emission and transport. Meteorological conditions observed during this campaign (moderate temperatures and southern flows) were not favorable to produce high level of atmospheric pollutants nor

  2. Simulation of the Indirect Radiative Forcing of Climate Due to Aerosols by the Two-Way Coupled WRF-CMAQ over the Eastern United States

    EPA Science Inventory

    In this study, the shortwave cloud forcing (SWCF) and longwave cloud forcing (LWCF) are estimated with the newly developed two-way coupled WRF-CMAQ over the eastern United States. Preliminary indirect aerosol forcing has been successfully implemented in WRF-CMAQ. The comparisons...

  3. A global model simulation of present and future nitrate aerosols and their direct radiative forcing of climate

    NASA Astrophysics Data System (ADS)

    Hauglustaine, D. A.; Balkanski, Y.; Schulz, M.

    2014-10-01

    The ammonia cycle and nitrate particle formation are introduced into the LMDz-INCA (Laboratoire de Météorologie Dynamique, version 4 - INteraction with Chemistry and Aerosols, version 3) global model. An important aspect of this new model is that both fine nitrate particle formation in the accumulation mode and coarse nitrate forming on existing dust and sea-salt particles are considered. The model simulates distributions of nitrates and related species in agreement with previous studies and observations. The calculated present-day total nitrate direct radiative forcing since the pre-industrial is -0.056 W m-2. This forcing corresponds to 18% of the sulfate forcing. Fine particles largely dominate the nitrate forcing, representing close to 90% of this value. The model has been used to investigate the future changes in nitrates and direct radiative forcing of climate based on snapshot simulations for the four representative concentration pathway (RCP) scenarios and for the 2030, 2050, and 2100 time horizons. Due to a decrease in fossil fuel emissions in the future, the concentration of most of the species involved in the nitrate-ammonium-sulfate system drop by 2100 except for ammonia, which originates from agricultural practices and for which emissions significantly increase in the future. Despite the decrease of nitrate surface levels in Europe and North America, the global burden of accumulation mode nitrates increases by up to a factor of 2.6 in 2100. This increase in ammonium nitrate in the future arises despite decreasing NOx emissions due to increased availability of ammonia to form ammonium nitrate. The total aerosol direct forcing decreases from its present-day value of -0.234 W m-2 to a range of -0.070 to -0.130 W m-2 in 2100 based on the considered scenario. The direct forcing decreases for all aerosols except for nitrates, for which the direct negative forcing increases to a range of -0.060 to -0.115 W m-2 in 2100. Including nitrates in the radiative

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

    NASA Technical Reports Server (NTRS)

    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.

  5. Mechanisms of Formation of Secondary Organic Aerosols and Implications for Global Radiative Forcing

    SciTech Connect

    John H. Seinfeld

    2011-12-08

    Organic material constitutes about 50% of global atmospheric aerosol mass, and the dominant source of organic aerosol is the oxidation of volatile hydrocarbons, to produce secondary organic aerosol (SOA). Understanding the formation of SOA is crucial to predicting present and future climate effects of atmospheric aerosols. The goal of this program is to significantly increase our understanding of secondary organic aerosol (SOA) formation in the atmosphere. Ambient measurements indicate that the amount of SOA in the atmosphere exceeds that predicted in current models based on existing laboratory chamber data. This would suggest that either the SOA yields measured in laboratory chambers are understated or that all major organic precursors have not been identified. In this research program we are systematically exploring these possibilities.

  6. Aerosol Radiative Forcing Estimates from South Asian Clay Brick Production Based on Direct Emission Measurements

    NASA Astrophysics Data System (ADS)

    Weyant, C.; Athalye, V.; Ragavan, S.; Rajarathnam, U.; Kr, B.; Lalchandani, D.; Maithel, S.; Malhotra, G.; Bhanware, P.; Thoa, V.; Phuong, N.; Baum, E.; Bond, T. C.

    2012-12-01

    About 150-200 billion clay bricks are produced in India every year. Most of these bricks are fired in small-scale traditional kilns that burn coal or biomass without pollution controls. Reddy and Venkataraman (2001) estimated that 8% of fossil fuel related PM2.5 emissions and 23% of black carbon emissions in India are released from brick production. Few direct emissions measurements have been done in this industry and black carbon emissions, in particular, have not been previously measured. In this study, 9 kilns representing five common brick kiln technologies were tested for aerosol properties and gaseous pollutant emissions, including optical scattering and absorption and thermal-optical OC/EC. Simple relationships are then used to estimate the radiative-forcing impact. Kiln design and fuel quality greatly affect the overall emission profiles and relative climate warming. Batch production kilns, such as the Downdraft kiln, produce the most PM2.5 (0.97 gPM2.5/fired brick) with an OC/EC fraction of 0.3. Vertical Shaft Brick kilns using internally mixed fuels produce the least PM (0.09 gPM2.5/kg fired brick) with the least EC (OC/EC = 16.5), but these kilns are expensive to implement and their use throughout Southern Asia is minimal. The most popular kiln in India, the Bull's Trench kiln, had fewer emissions per brick than the Downdraft kiln, but an even higher EC fraction (OC/EC = 0.05). The Zig-zag kiln is similar in structure to the Bull's Trench kiln, but the emission factors are significantly lower: 50% reduction for CO, 17% for PM2.5 and 60% for black carbon. This difference in emissions suggests that converting traditional Bull's Trench kilns into less polluting Zig-zag kilns would result in reduced atmospheric warming from brick production.

  7. Assessment of aerosol radiative forcing in the North-Eastern region of India using radiative transfer model and regional climate model

    NASA Astrophysics Data System (ADS)

    Pathak, Binita; Bhuyan, Pradip

    Regional characterization of atmospheric aerosols is essential from the viewpoint of reducing the current uncertainties in the understanding of their climate implications at regional and global scale. The north-eastern part of India owing to its unique topography and geography located at sub Himalayan range and the middle of Indian Subcontinent and South-East Asian region as well as with scattered local hilly regions persevere complex aerosol environment. Collocated measurements of parameters corresponding to aerosol optical and physical properties i.e., spectral aerosol optical depths (AODs) by a 10 channel Multi-Wavelength solar Radiometer (MWR), near surface aerosol mass concentration of composite aerosols by a Quartz Crystal Microbalance Impactor (QCM) and Black Carbon (BC) mass concentration by an Aethalometer have been used in the Optical Properties of Aerosols and Clouds (OPAC) model to estimate the optical properties of composite aerosols over Dibrugarh (27.3ºN, 94.6ºE, 111 m amsl) for the short wavelength range. The OPAC outputs are then used as inputs to the Rdiative Transfer model ‘Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART)’, developed by the University of California, Santa Barbara, to derive the shortwave aerosol radiative properties. The aerosol optical depth shows maximum value in pre-monsoon season and minimum in post-monsoon season. Columnar aerosols are bimodal in nature with dominant contribution from fine mode aerosols. Unlike columnar aerosols surface aerosol concentration including black carbon shows maximum value in winter and minimum in monsoon season. The aerosol radiative forcing (ARF) estimated for the period pre-monsoon 2008-winter 2013 shows maximum value in the pre-monsoon season at the surface as well as in the atmosphere corresponding to highest columnar aerosol loading. The surface forcing varies between -37 Wm-2 in Pre-monsoon 2009 and 2011 to -13 Wm-2 in Post-monsoon 2008 while forcing in the Atmosphere

  8. Sensitivity of aerosol indirect forcing and autoconversion to cloud droplet parameterization: an assessment with the NASA Global Modeling Initiative.

    NASA Astrophysics Data System (ADS)

    Sotiropoulou, R. P.; Meshkhidze, N.; Nenes, A.

    2006-12-01

    The aerosol indirect forcing is one of the largest sources of uncertainty in assessments of anthropogenic climate change [IPCC, 2001]. Much of this uncertainty arises from the approach used for linking cloud droplet number concentration (CDNC) to precursor aerosol. Global Climate Models (GCM) use a wide range of cloud droplet activation mechanisms ranging from empirical [Boucher and Lohmann, 1995] to detailed physically- based formulations [e.g., Abdul-Razzak and Ghan, 2000; Fountoukis and Nenes, 2005]. The objective of this study is to assess the uncertainties in indirect forcing and autoconversion of cloud water to rain caused by the application of different cloud droplet parameterization mechanisms; this is an important step towards constraining the aerosol indirect effects (AIE). Here we estimate the uncertainty in indirect forcing and autoconversion rate using the NASA Global Model Initiative (GMI). The GMI allows easy interchange of meteorological fields, chemical mechanisms and the aerosol microphysical packages. Therefore, it is an ideal tool for assessing the effect of different parameters on aerosol indirect forcing. The aerosol module includes primary emissions, chemical production of sulfate in clear air and in-cloud aqueous phase, gravitational sedimentation, dry deposition, wet scavenging in and below clouds, and hygroscopic growth. Model inputs include SO2 (fossil fuel and natural), black carbon (BC), organic carbon (OC), mineral dust and sea salt. The meteorological data used in this work were taken from the NASA Data Assimilation Office (DAO) and two different GCMs: the NASA GEOS4 finite volume GCM (FVGCM) and the Goddard Institute for Space Studies version II' (GISS II') GCM. Simulations were carried out for "present day" and "preindustrial" emissions using different meteorological fields (i.e. DAO, FVGCM, GISS II'); cloud droplet number concentration is computed from the correlations of Boucher and Lohmann [1995], Abdul-Razzak and Ghan [2000

  9. A method for the direct measurement of surface tension of collected atmospherically relevant aerosol particles using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Hritz, Andrew D.; Raymond, Timothy M.; Dutcher, Dabrina D.

    2016-08-01

    Accurate estimates of particle surface tension are required for models concerning atmospheric aerosol nucleation and activation. However, it is difficult to collect the volumes of atmospheric aerosol required by typical instruments that measure surface tension, such as goniometers or Wilhelmy plates. In this work, a method that measures, ex situ, the surface tension of collected liquid nanoparticles using atomic force microscopy is presented. A film of particles is collected via impaction and is probed using nanoneedle tips with the atomic force microscope. This micro-Wilhelmy method allows for direct measurements of the surface tension of small amounts of sample. This method was verified using liquids, whose surface tensions were known. Particles of ozone oxidized α-pinene, a well-characterized system, were then produced, collected, and analyzed using this method to demonstrate its applicability for liquid aerosol samples. It was determined that oxidized α-pinene particles formed in dry conditions have a surface tension similar to that of pure α-pinene, and oxidized α-pinene particles formed in more humid conditions have a surface tension that is significantly higher.

  10. Vertical microphysical profiles of convective clouds as a tool for obtaining aerosol cloud-mediated climate forcings

    SciTech Connect

    Rosenfeld, Daniel

    2015-12-23

    Quantifying the aerosol/cloud-mediated radiative effect at a global scale requires simultaneous satellite retrievals of cloud condensation nuclei (CCN) concentrations and cloud base updraft velocities (Wb). Hitherto, the inability to do so has been a major cause of high uncertainty regarding anthropogenic aerosol/cloud-mediated radiative forcing. This can be addressed by the emerging capability of estimating CCN and Wb of boundary layer convective clouds from an operational polar orbiting weather satellite. Our methodology uses such clouds as an effective analog for CCN chambers. The cloud base supersaturation (S) is determined by Wb and the satellite-retrieved cloud base drop concentrations (Ndb), which is the same as CCN(S). Developing and validating this methodology was possible thanks to the ASR/ARM measurements of CCN and vertical updraft profiles. Validation against ground-based CCN instruments at the ARM sites in Oklahoma, Manaus, and onboard a ship in the northeast Pacific showed a retrieval accuracy of ±25% to ±30% for individual satellite overpasses. The methodology is presently limited to boundary layer not raining convective clouds of at least 1 km depth that are not obscured by upper layer clouds, including semitransparent cirrus. The limitation for small solar backscattering angles of <25º restricts the satellite coverage to ~25% of the world area in a single day. This methodology will likely allow overcoming the challenge of quantifying the aerosol indirect effect and facilitate a substantial reduction of the uncertainty in anthropogenic climate forcing.

  11. Global distribution and climate forcing of marine organic aerosol: 1. Model improvements and evaluation

    SciTech Connect

    Meskhidze, N.; Xu, J.; Gantt, Brett; Zhang, Yang; Nenes, Athanasios; Ghan, Steven J.; Liu, Xiaohong; Easter, Richard C.; Zaveri, Rahul A.

    2011-11-23

    Marine organic aerosol emissions have been implemented and evaluated within the National Center of Atmospheric Research (NCAR)'s Community Atmosphere Model (CAM5) with the Pacific Northwest National Laboratory's 7-mode Modal Aerosol Module (MAM-7). Emissions of marine primary organic aerosols (POA), phytoplanktonproduced isoprene- and monoterpenes-derived secondary organic aerosols (SOA) and methane sulfonate (MS{sup -}) are shown to affect surface concentrations of organic aerosols in remote marine regions. Global emissions of submicron marine POA is estimated to be 7.9 and 9.4 Tg yr{sup -1}, for the Gantt et al. (2011) and Vignati et al. (2010) emission parameterizations, respectively. Marine sources of SOA and particulate MS{sup -} (containing both sulfur and carbon atoms) contribute an additional 0.2 and 5.1 Tg yr{sup -1}, respectively. Widespread areas over productive waters of the Northern Atlantic, Northern Pacific, and the Southern Ocean show marine-source submicron organic aerosol surface concentrations of 100 ngm{sup -3}, with values up to 400 ngm{sup -3} over biologically productive areas. Comparison of long-term surface observations of water insoluble organic matter (WIOM) with POA concentrations from the two emission parameterizations shows that despite revealed discrepancies (often more than a factor of 2), both Gantt et al. (2011) and Vignati et al. (2010) formulations are able to capture the magnitude of marine organic aerosol concentrations, with the Gantt et al. (2011) parameterization attaining better seasonality. Model simulations show that the mixing state of the marine POA can impact the surface number concentration of cloud condensation nuclei (CCN). The largest increases (up to 20 %) in CCN (at a supersaturation (S) of 0.2 %) number concentration are obtained over biologically productive ocean waters when marine organic aerosol is assumed to be externally mixed with sea-salt. Assuming marine organics are internally-mixed with sea

  12. Aerosol Observing System (AOS) Handbook

    SciTech Connect

    Jefferson, A

    2011-01-17

    The Aerosol Observing System (AOS) is a suite of in situ surface measurements of aerosol optical and cloud-forming properties. The instruments measure aerosol properties that influence the earth’s radiative balance. The primary optical measurements are those of the aerosol scattering and absorption coefficients as a function of particle size and radiation wavelength and cloud condensation nuclei (CCN) measurements as a function of percent supersaturation. Additional measurements include those of the particle number concentration and scattering hygroscopic growth. Aerosol optical measurements are useful for calculating parameters used in radiative forcing calculations such as the aerosol single-scattering albedo, asymmetry parameter, mass scattering efficiency, and hygroscopic growth. CCN measurements are important in cloud microphysical models to predict droplet formation.

  13. GUIDE TO CALCULATING TRANSPORT EFFICIENCY OF AEROSOLS IN OCCUPATIONAL AIR SAMPLING SYSTEMS

    SciTech Connect

    Hogue, M.; Hadlock, D.; Thompson, M.; Farfan, E.

    2013-11-12

    This report will present hand calculations for transport efficiency based on aspiration efficiency and particle deposition losses. Because the hand calculations become long and tedious, especially for lognormal distributions of aerosols, an R script (R 2011) will be provided for each element examined. Calculations are provided for the most common elements in a remote air sampling system, including a thin-walled probe in ambient air, straight tubing, bends and a sample housing. One popular alternative approach would be to put such calculations in a spreadsheet, a thorough version of which is shared by Paul Baron via the Aerocalc spreadsheet (Baron 2012). To provide greater transparency and to avoid common spreadsheet vulnerabilities to errors (Burns 2012), this report uses R. The particle size is based on the concept of activity median aerodynamic diameter (AMAD). The AMAD is a particle size in an aerosol where fifty percent of the activity in the aerosol is associated with particles of aerodynamic diameter greater than the AMAD. This concept allows for the simplification of transport efficiency calculations where all particles are treated as spheres with the density of water (1g cm-3). In reality, particle densities depend on the actual material involved. Particle geometries can be very complicated. Dynamic shape factors are provided by Hinds (Hinds 1999). Some example factors are: 1.00 for a sphere, 1.08 for a cube, 1.68 for a long cylinder (10 times as long as it is wide), 1.05 to 1.11 for bituminous coal, 1.57 for sand and 1.88 for talc. Revision 1 is made to correct an error in the original version of this report. The particle distributions are based on activity weighting of particles rather than based on the number of particles of each size. Therefore, the mass correction made in the original version is removed from the text and the calculations. Results affected by the change are updated.

  14. Observations of Smoke Aerosol from Biomass Burning in Mexico: Effect of Particle Aging on Radiative Forcing and Remote Sensing

    NASA Technical Reports Server (NTRS)

    Remer, Lorraine A.; Bruintjes, Roelof; Holben, Brent N.; Christopher, Sundar

    1999-01-01

    We take advantage of the May 1998 biomass burning event in Southern Mexico to test the global applicability of a smoke aerosol size model developed from data observed in South America. The Mexican event is an unique opportunity to observe well-aged, residual smoke. Observations of smoke aerosol size distribution made from vertical profiles of airborne in situ measurements show an inverse relationship between concentration and particle size that suggests the aging process continues more than a week after the smoke is separated from its fire sources. The ground-based radiometer retrievals show that the column-averaged, aged, Mexican smoke particles are larger (diameter = 0.28 - 0.33 micrometers) than the mean smoke particles in South America (diameter = 0.22 - 0.30 micrometers). However, the difference (delta - 0.06 micrometer) translates into differences in backscattering coefficient of only 4-7% and an increase of direct radiative forcing of only 10%.

  15. Spatial variations in immediate greenhouse gases and aerosol emissions and resulting radiative forcing from wildfires in interior Alaska

    USGS Publications Warehouse

    Huang, Shengli; Liu, Heping; Dahal, Devendra; Jin, Suming; Li, Shuang; Liu, Shu-Guang

    2016-01-01

    Boreal fires can cool the climate; however, this conclusion came from individual fires and may not represent the whole story. We hypothesize that the climatic impact of boreal fires depends on local landscape heterogeneity such as burn severity, prefire vegetation type, and soil properties. To test this hypothesis, spatially explicit emission of greenhouse gases (GHGs) and aerosols and their resulting radiative forcing are required as an important and necessary component towards a full assessment. In this study, we integrated remote sensing (Landsat and MODIS) and models (carbon consumption model, emission factors model, and radiative forcing model) to calculate the carbon consumption, GHGs and aerosol emissions, and their radiative forcing of 2001–2010 fires at 30 m resolution in the Yukon River Basin of Alaska. Total carbon consumption showed significant spatial variation, with a mean of 2,615 g C m−2 and a standard deviation of 2,589 g C m−2. The carbon consumption led to different amounts of GHGs and aerosol emissions, ranging from 593.26 Tg (CO2) to 0.16 Tg (N2O). When converted to equivalent CO2 based on global warming potential metric, the maximum 20 years equivalent CO2 was black carbon (713.77 Tg), and the lowest 20 years equivalent CO2 was organic carbon (−583.13 Tg). The resulting radiative forcing also showed significant spatial variation: CO2, CH4, and N2O can cause a 20-year mean radiative forcing of 7.41 W m−2 with a standard deviation of 2.87 W m−2. This emission forcing heterogeneity indicates that different boreal fires have different climatic impacts. When considering the spatial variation of other forcings, such as surface shortwave forcing, we may conclude that some boreal fires, especially boreal deciduous fires, can warm the climate.

  16. "Worst case" aerosol testing parameters: II. Efficiency dependence of commercial respirator filters on humidity pretreatment.

    PubMed

    Moyer, E S; Stevens, G A

    1989-05-01

    Previous studies have shown that relative humidity has a degrading effect on the performance of commercially available particulate air-purifying respirator filters. That degradation results from a reduction of charge within the filter. This study was done to evaluate the time-dependent effects of relative humidity pretreatment and the reduction of charge on filter penetration against a most penetrating, "worst case" aerosol challenge. Filters of the dust and mist; dust, fume, and mist; paint, lacquer, and enamel mist; and high efficiency types were tested after being pretreated in an environment of 38 degrees C and 85% relative humidity for periods up to 42 days. After various intervals of pretreatment (1, 7, 14, 28, and 42 days), the filters were tested against neutralized worst-case sodium chloride (NaCl) and dioctyl phthalate (DOP) aerosols for percent penetration. The results showed a drop in filter efficiency of approximately 2%-6% depending on preconditioning time, except for the high efficiency filters tested which showed no detectable change. PMID:2729102

  17. Worst case aerosol testing parameters: II. Efficiency dependence of commercial respirator filters on humidity pretreatment

    SciTech Connect

    Moyer, E.S.; Stevens, G.A.

    1989-05-01

    Previous studies have shown that relative humidity has a degrading effect on the performance of commercially available particulate air-purifying respirator filters. That degradation results from a reduction of charge within the filter. This study was done to evaluate the time-dependent effects of relative humidity pretreatment and the reduction of charge on filter penetration against a most penetrating, ''worst case'' aerosol challenge. Filters of the dust and mist; dust, fume, and mist; paint, lacquer, and enamel mist; and high efficiency types were tested after being pretreated in an environment of 38 degrees C and 85% relative humidity for periods up to 42 days. After various intervals of pretreatment (1, 7, 14, 28, and 42 days), the filters were tested against neutralized worst-case sodium chloride (NaCl) and dioctyl phthalate (DOP) aerosols for percent penetration. The results showed a drop in filter efficiency of approximately 2%-6% depending on preconditioning time, except for the high efficiency filters tested which showed no detectable change.

  18. Organic aerosols

    SciTech Connect

    Penner, J.E.

    1994-01-01

    Organic aerosols scatter solar radiation. They may also either enhance or decrease concentrations of cloud condensation nuclei. This paper summarizes observed concentrations of aerosols in remote continental and marine locations and provides estimates for the sources of organic aerosol matter. The anthropogenic sources of organic aerosols may be as large as the anthropogenic sources of sulfate aerosols, implying a similar magnitude of direct forcing of climate. The source estimates are highly uncertain and subject to revision in the future. A slow secondary source of organic aerosols of unknown origin may contribute to the observed oceanic concentrations. The role of organic aerosols acting as cloud condensation nuclei (CCN) is described and it is concluded that they may either enhance or decrease the ability of anthropogenic sulfate aerosols to act as CCN.

  19. Development of a New Technique for the Efficient Delivery of Aerosolized Medications to Infants on Mechanical Ventilation

    PubMed Central

    Longest, P. Worth; Tian, Geng

    2014-01-01

    Purpose To evaluate the efficiency of a new technique for delivering aerosols to intubated infants that employs a new Y-connector, access port administration of a dry powder, and excipient enhanced growth (EEG) formulation particles that change size in the airways. Methods A previously developed CFD model combined with algebraic correlations were used to predict delivery system and lung deposition of typical nebulized droplets (MMAD = 4.9 μm) and EEG dry powder aerosols. The delivery system consisted of a Y-connector [commercial (CM); streamlined (SL); or streamlined with access port (SL-port)] attached to a 4-mm diameter endotracheal tube leading to the airways of a 6-month-old infant. Results Compared to the CM device and nebulized aerosol, the EEG approach with an initial 0.9 μm aerosol combined with the SL and SL-port geometries reduced device depositional losses by factors of 3-fold and >10-fold, respectively. With EEG powder aerosols, the SL geometry provided the maximum tracheobronchial deposition fraction (55.7%), whereas the SL-port geometry provided the maximum alveolar (67.6%) and total lung (95.7%) deposition fractions, respectively. Conclusions Provided the aerosol can be administered in the first portion of the inspiration cycle, the proposed new method can significantly improve the deposition of pharmaceutical aerosols in the lungs of intubated infants. PMID:25103332

  20. Separation efficiency of a wood dust collector-field measurement using a fluorescent aerosol.

    PubMed

    Bémer, D; Regnier, R; Calle, S

    2000-05-01

    Given the dangerous nature of the dust emitted in the wood industry, the quality of the recycled air in the work premises after cleaning must be strictly controlled.A method of measuring the efficiency of a wood dust collector as a function of the particle diameter has been developed using a fluorescein tracer aerosol generated upstream of the equipment. The separation efficiency is determined from the particle size mass distribution of the tracer, both upstream and downstream, measured by means of two cascade impactors. The mass efficiency measured by tracer technique was compared on a test rig to the number efficiency measured using a reference method based on optical counting. The agreement between the two efficiencies is quite good; nevertheless, the tracer method leads to results that are slightly below those obtained using the reference method. The method was applied to measure the efficiency of a 11 500 m(3) h(-1) wood dust collector. The results are presented along with those obtained from a sample of plane filter media making up the bags of the dust collector.

  1. Effect of Spectrally Varying Albedo of Vegetation Surfaces on Shortwave Radiation Fluxes and Aerosol Direct Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Zhu, L.; Martins, J. V.; Yu, H.

    2012-01-01

    This study develops an algorithm for representing detailed spectral features of vegetation albedo based on Moderate Resolution Imaging Spectrometer (MODIS) observations at 7 discrete channels, referred to as the MODIS Enhanced Vegetation Albedo (MEVA) algorithm. The MEVA algorithm empirically fills spectral gaps around the vegetation red edge near 0.7 micrometers and vegetation water absorption features at 1.48 and 1.92 micrometers which cannot be adequately captured by the MODIS 7 channels. We then assess the effects of applying MEVA in comparison to four other traditional approaches to calculate solar fluxes and aerosol direct radiative forcing (DRF) at the top of atmosphere (TOA) based on the MODIS discrete reflectance bands. By comparing the DRF results obtained through the MEVA method with the results obtained through the other four traditional approaches, we show that filling the spectral gap of the MODIS measurements around 0.7 micrometers based on the general spectral behavior of healthy green vegetation leads to significant improvement in the instantaneous aerosol DRF at TOA (up to 3.02Wm(exp -2) difference or 48% fraction of the aerosol DRF, .6.28Wm(exp -2), calculated for high spectral resolution surface reflectance from 0.3 to 2.5 micrometers for deciduous vegetation surface). The corrections of the spectral gaps in the vegetation spectrum in the near infrared, again missed by the MODIS reflectances, also contributes to improving TOA DRF calculations but to a much lower extent (less than 0.27Wm(exp -2), or about 4% of the instantaneous DRF). Compared to traditional approaches, MEVA also improves the accuracy of the outgoing solar flux between 0.3 to 2.5 micrometers at TOA by over 60Wm(exp -2) (for aspen 3 surface) and aerosol DRF by over 10Wm(exp -2) (for dry grass). Specifically, for Amazon vegetation types, MEVA can improve the accuracy of daily averaged aerosol radiative forcing in the spectral range of 0.3 to 2.5 micrometers at equator at the

  2. Determination of the passing efficiency for aerosol chemical species through a typical aircraft-mounted, diffuser-type aerosol inlet system

    NASA Astrophysics Data System (ADS)

    Sheridan, Patrick J.; Norton, Richard B.

    1998-04-01

    To assess the particle transmission efficiency of a conventional aircraft-mounted, diffuser-type inlet (CI), a new design inlet containing an internal filter basket assembly (aerosol filter inlet, or AFI) was constructed. All interior surfaces of the AFI were covered with filter material, and air was actively pulled through these filter walls during aerosol sampling. The AFI was demonstrated in the laboratory to trap nearly all particles entering its nozzle orifice, so it was considered usable as a baseline to judge the performance of other inlets. Wind tunnel studies were conducted at three different wind velocities that approximated typical research aircraft speeds. As wind velocity increased, particle transmission through the CI relative to the AFI decreased, as evidenced by chemical analysis of the filter deposits. Aircraft studies of the two inlets showed that particle transmission varied significantly with the measured species. Typical coarse-particle species such as Ca++, Mg++, Na+ and K+ showed 50-90% mass losses through a conventional diffuser-type inlet/curved intake tube system. Predominantly fine particle species such as SO4= and NH4+ passed the CI system with much higher efficiencies, with aerosol mass losses of 0-26% for most flights. Since the AFI traps nearly all particles aspirated into its nozzle orifice, these values indicate that on average, 80-90% of the SO4= and NH4+ aerosol mass passes through the CI and curved intake tube during airborne sampling. This finding suggests that the capability to sample fine (i.e., submicrometer) aerosols from aircraft is perhaps not as bad as has been previously reported, given that adequate attention is paid to inlet design, location, and orientation issues.

  3. Forcing of anthropogenic aerosols on temperature trends of the sub-thermocline southern Indian Ocean.

    PubMed

    Cowan, Tim; Cai, Wenju; Purich, Ariaan; Rotstayn, Leon; England, Matthew H

    2013-01-01

    In the late twentieth century, the sub-thermocline waters of the southern tropical and subtropical Indian Ocean experienced a sharp cooling. This cooling has been previously attributed to an anthropogenic aerosol-induced strengthening of the global ocean conveyor, which transfers heat from the subtropical gyre latitudes toward the North Atlantic. From the mid-1990s the sub-thermocline southern Indian Ocean experienced a rapid temperature trend reversal. Here we show, using climate models from phase 5 of the Coupled Model Intercomparison Project, that the late twentieth century sub-thermocline cooling of the southern Indian Ocean was primarily driven by increasing anthropogenic aerosols and greenhouse gases. The models simulate a slow-down in the sub-thermocline cooling followed by a rapid warming towards the mid twenty-first century. The simulated evolution of the Indian Ocean temperature trend is linked with the peak in aerosols and their subsequent decline in the twenty-first century, reinforcing the hypothesis that aerosols influence ocean circulation trends.

  4. Forcing of anthropogenic aerosols on temperature trends of the sub-thermocline southern Indian Ocean

    PubMed Central

    Cowan, Tim; Cai, Wenju; Purich, Ariaan; Rotstayn, Leon; England, Matthew H.

    2013-01-01

    In the late twentieth century, the sub-thermocline waters of the southern tropical and subtropical Indian Ocean experienced a sharp cooling. This cooling has been previously attributed to an anthropogenic aerosol-induced strengthening of the global ocean conveyor, which transfers heat from the subtropical gyre latitudes toward the North Atlantic. From the mid-1990s the sub-thermocline southern Indian Ocean experienced a rapid temperature trend reversal. Here we show, using climate models from phase 5 of the Coupled Model Intercomparison Project, that the late twentieth century sub-thermocline cooling of the southern Indian Ocean was primarily driven by increasing anthropogenic aerosols and greenhouse gases. The models simulate a slow-down in the sub-thermocline cooling followed by a rapid warming towards the mid twenty-first century. The simulated evolution of the Indian Ocean temperature trend is linked with the peak in aerosols and their subsequent decline in the twenty-first century, reinforcing the hypothesis that aerosols influence ocean circulation trends. PMID:23873281

  5. Changes in radiative forcing in Amazonia: the influence of clouds and aerosols controlling carbon budget

    NASA Astrophysics Data System (ADS)

    Artaxo, Paulo

    2016-07-01

    Surface radiation fluxes are critically important in photosynthetic processes that controls carbon assimilation and losses in tropical forests. Clouds and aerosols control the surface radiation fluxes in Amazonia, and the ratio of diffuse and direct radiation directly affects photosynthetic plant processes. Biomass burning emissions changes the atmosphere aerosol loading. The background aerosol optical thickness in wet season Amazonia is about 0.1 at 550 nm, while during the dry season AOT can reach values as high as 3-4 over large areas. The increase in diffuse radiation significantly enhance photosynthesis. Remote sensing measurements using MODIS and AERONET were used to measure the large scale aerosol distribution over Amazonia, and LBA flux towers provided the carbon balance over several sites. The enhancement in carbon uptake for AOD between 0.1 and 1 can reach 45%. For AOD above 1, the reduction in the direct flux starts to dominate and a strong reduction in carbon uptake is observed. Cloud cover also has a huge impact on carbon balance in Amazonia, but it is more difficult to quantify. These effects controls carbon balance in Amazonia.

  6. Present and potential future contributions of sulfate, black and organic carbon aerosols from China to global air quality, premature mortality and radiative forcing

    NASA Astrophysics Data System (ADS)

    Saikawa, E.; Naik, V.; Horowitz, L. W.; Liu, J.; Mauzerall, D. L.

    2008-12-01

    Aerosols are harmful to human health and have both direct and indirect effects on climate. China is a major contributor to global emissions of sulfur dioxide (SO2), a sulfate (SO42-) precursor, organic carbon (OC), and black carbon (BC) aerosols. Although increasingly examined, the effect of present and potential future levels of these emissions on global premature mortality and climate change has not been well quantified. Through both direct and indirect effects, SO42- and OC exert negative radiative forcing (cooling) while BC exerts positive forcing (warming). We analyze the effect of China's emissions of SO2, SO42-, OC and BC in 2000 and for three emission scenarios in 2030 on global surface aerosol concentrations, premature mortality, and radiative forcing. Using global models of chemical transport (MOZART-2) and radiative transfer (GFDL RTM), and combining simulation results with gridded population data, mortality rates, and concentration-response relationships from the epidemiological literature, we estimate the contribution of Chinese aerosols to global annual premature mortality and to radiative forcing in 2000 and 2030. In 2000, we estimate these aerosols cause 385,320 premature deaths in China and an additional 18 240 globally. In 2030, aggressive emission controls lead to a reduction in premature deaths to 200,370 in China and 7,740 elsewhere, while under a high emissions scenario premature deaths would increase to 602,950 in China and to 29,750 elsewhere. Because the negative radiative forcing from SO42- and OC is larger than the positive forcing from BC, the Chinese aerosols lead to global net direct radiative forcing of -74 mW m-2 in 2000 and between -15 and -97 mW m-2 in 2030 based on the emissions scenario. Our analysis suggests that environmental policies that simultaneously improve public health and mitigate climate change would be highly beneficial (eg. reductions in BC emissions).

  7. Efficient Isoprene Secondary Organic Aerosol Formation from a Non-IEPOX Pathway.

    PubMed

    Liu, Jiumeng; D'Ambro, Emma L; Lee, Ben H; Lopez-Hilfiker, Felipe D; Zaveri, Rahul A; Rivera-Rios, Jean C; Keutsch, Frank N; Iyer, Siddharth; Kurten, Theo; Zhang, Zhenfa; Gold, Avram; Surratt, Jason D; Shilling, John E; Thornton, Joel A

    2016-09-20

    With a large global emission rate and high reactivity, isoprene has a profound effect upon atmospheric chemistry and composition. The atmospheric pathways by which isoprene converts to secondary organic aerosol (SOA) and how anthropogenic pollutants such as nitrogen oxides and sulfur affect this process are subjects of intense research because particles affect Earth's climate and local air quality. In the absence of both nitrogen oxides and reactive aqueous seed particles, we measure SOA mass yields from isoprene photochemical oxidation of up to 15%, which are factors of 2 or more higher than those typically used in coupled chemistry climate models. SOA yield is initially constant with the addition of increasing amounts of nitric oxide (NO) but then sharply decreases for input concentrations above 50 ppbv. Online measurements of aerosol molecular composition show that the fate of second-generation RO2 radicals is key to understanding the efficient SOA formation and the NOx-dependent yields described here and in the literature. These insights allow for improved quantitative estimates of SOA formation in the preindustrial atmosphere and in biogenic-rich regions with limited anthropogenic impacts and suggest that a more-complex representation of NOx-dependent SOA yields may be important in models.

  8. Efficient Isoprene Secondary Organic Aerosol Formation from a Non-IEPOX Pathway.

    PubMed

    Liu, Jiumeng; D'Ambro, Emma L; Lee, Ben H; Lopez-Hilfiker, Felipe D; Zaveri, Rahul A; Rivera-Rios, Jean C; Keutsch, Frank N; Iyer, Siddharth; Kurten, Theo; Zhang, Zhenfa; Gold, Avram; Surratt, Jason D; Shilling, John E; Thornton, Joel A

    2016-09-20

    With a large global emission rate and high reactivity, isoprene has a profound effect upon atmospheric chemistry and composition. The atmospheric pathways by which isoprene converts to secondary organic aerosol (SOA) and how anthropogenic pollutants such as nitrogen oxides and sulfur affect this process are subjects of intense research because particles affect Earth's climate and local air quality. In the absence of both nitrogen oxides and reactive aqueous seed particles, we measure SOA mass yields from isoprene photochemical oxidation of up to 15%, which are factors of 2 or more higher than those typically used in coupled chemistry climate models. SOA yield is initially constant with the addition of increasing amounts of nitric oxide (NO) but then sharply decreases for input concentrations above 50 ppbv. Online measurements of aerosol molecular composition show that the fate of second-generation RO2 radicals is key to understanding the efficient SOA formation and the NOx-dependent yields described here and in the literature. These insights allow for improved quantitative estimates of SOA formation in the preindustrial atmosphere and in biogenic-rich regions with limited anthropogenic impacts and suggest that a more-complex representation of NOx-dependent SOA yields may be important in models. PMID:27548285

  9. A Multimodel Assessment of the Influence of Regional Anthropogenic Emission Reductions on Aerosol Direct Radiative Forcing and the Role of Intercontinental Transport

    NASA Technical Reports Server (NTRS)

    Yu, Hongbin; Chin, Mian; West, Jason; Atherton, Cynthia S.; Bellouin, Nicolas; Bergmann, Dan; Bey, Isabelle; Bian, Huisheng; Diehl, Thomas; Forberth, Gerd; Hess, Peter; Schulz, Michael; Shindell, Drew; Takemura, Toshihiko; Tan, Qian

    2013-01-01

    In this study, we assess changes of aerosol optical depth (AOD) and direct radiative forcing (DRF) in response to the reduction of anthropogenic emissions in four major pollution regions in the Northern Hemisphere by using results from nine global models in the framework of the Hemispheric Transport of Air Pollution (HTAP). DRF at top of atmosphere (TOA) and surface is estimated based on AOD results from the HTAP models and AOD-normalized DRF (NDRF) from a chemical transport model. The multimodel results show that, on average, a 20% reduction of anthropogenic emissions in North America, Europe, East Asia, and South Asia lowers the global mean AOD (all-sky TOA DRF) by 9.2% (9.0%), 3.5% (3.0%), and 9.4% (10.0%) for sulfate, particulate organic matter (POM), and black carbon (BC), respectively. Global annual average TOA all-sky forcing efficiency relative to particle or gaseous precursor emissions from the four regions (expressed as multimodel mean +/- one standard deviation) is -3.5 +/-0.8, -4.0 +/- 1.7, and 29.5+/-18.1mW / sq m per Tg for sulfate (relative to SO2), POM, and BC, respectively. The impacts of the regional emission reductions on AOD and DRF extend well beyond the source regions because of intercontinental transport (ICT). On an annual basis, ICT accounts for 11 +/- 5% to 31 +/- 9% of AOD and DRF in a receptor region at continental or subcontinental scale, with domestic emissions accounting for the remainder, depending on regions and species. For sulfate AOD, the largest ICT contribution of 31 +/- 9% occurs in South Asia, which is dominated by the emissions from Europe. For BC AOD, the largest ICT contribution of 28 +/- 18% occurs in North America, which is dominated by the emissions from East Asia. The large spreads among models highlight the need to improve aerosol processes in models, and evaluate and constrain models with observations.

  10. Column Aerosol Optical Properties and Aerosol Radiative Forcing During a Serious Haze-Fog Month over North China Plain in 2013 Based on Ground-Based Sunphotometer Measurements

    NASA Technical Reports Server (NTRS)

    Che, H.; Xia, X.; Zhu, J.; Li, Z.; Dubovik, O.; Holben, Brent N.; Goloub, P.; Chen, H.; Estelles, V.; Cuevas-Agullo, E.

    2014-01-01

    In January 2013, North China Plain experienced several serious haze events. Cimel sunphotometer measurements at seven sites over rural, suburban and urban regions of North China Plain from 1 to 30 January 2013 were used to further our understanding of spatial-temporal variation of aerosol optical parameters and aerosol radiative forcing (ARF). It was found that Aerosol Optical Depth at 500 nm (AOD500nm) during non-pollution periods at all stations was lower than 0.30 and increased significantly to greater than 1.00 as pollution events developed. The Angstrom exponent (Alpha) was larger than 0.80 for all stations most of the time. AOD500nm averages increased from north to south during both polluted and non-polluted periods on the three urban sites in Beijing. The fine mode AOD during pollution periods is about a factor of 2.5 times larger than that during the non-pollution period at urban sites but a factor of 5.0 at suburban and rural sites. The fine mode fraction of AOD675nm was higher than 80% for all sites during January 2013. The absorption AOD675nm at rural sites was only about 0.01 during pollution periods, while 0.03-0.07 and 0.01-0.03 during pollution and non-pollution periods at other sites, respectively. Single scattering albedo varied between 0.87 and 0.95 during January 2013 over North China Plain. The size distribution showed an obvious tri-peak pattern during the most serious period. The fine mode effective radius in the pollution period was about 0.01-0.08 microns larger than during nonpollution periods, while the coarse mode radius in pollution periods was about 0.06-0.38 microns less than that during nonpollution periods. The total, fine and coarse mode particle volumes varied by about 0.06-0.34 cu microns, 0.03-0.23 cu microns, and 0.03-0.10 cu microns, respectively, throughout January 2013. During the most intense period (1-16 January), ARF at the surface exceeded -50W/sq m, -180W/sq m, and -200W/sq m at rural, suburban, and urban sites

  11. Aerosol's optical and physical characteristics and direct radiative forcing during a shamal dust storm, a case study

    NASA Astrophysics Data System (ADS)

    Saeed, T. M.; Al-Dashti, H.; Spyrou, C.

    2014-04-01

    Dust aerosols are analyzed for their optical and physical properties during an episode of a dust storm that blew over Kuwait on 26 March 2003 when the military Operation Iraqi Freedom was in full swing. The intensity of the dust storm was such that it left a thick suspension of dust throughout the following day, 27 March. The synoptic sequence leading to the dust storm and the associated wind fields are discussed. Ground-based measurements of aerosol optical thickness reached 3.617 and 4.17 on 26 and 27 March respectively while the Ångstrom coefficient, α870/440, dropped to -0.0234 and -0.0318. Particulate matter concentration of 10 μm diameter or less, PM10, peaked at 4800 μg m-3 during dust storm hours of 26 March. Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved aerosol optical depth (AOD) by Deep Blue algorithm and Total Ozone Mapping Spectrometer (TOMS) aerosol index (AI) exhibited high values. Latitude-longitude maps of AOD and AI were used to deduce source regions of dust transport over Kuwait. The vertical profile of the dust layer was simulated using the SKIRON atmospheric model. Instantaneous net direct radiative forcing is calculated at top of atmosphere (TOA) and surface level. The thick dust layer of 26 March resulted in cooling the TOA by -60 Wm-2 and surface level by -175 Wm-2 for a surface albedo of 0.35. Slightly higher values were obtained for 27 March due to the increase in aerosol optical thickness. Radiative heating/cooling rates in the shortwave and longwave bands were also examined. Shortwave heating rate reached a maximum value of 2 K day-1 between 3 and 5 km, dropped to 1.5 K day-1 at 6 km and diminished at 8 km. Longwave radiation initially heated the lower atmosphere by a maximum value of 0.2 K day-1 at surface level, declined sharply at increasing altitude and diminished at 4 km. Above 4 km longwave radiation started to cool the atmosphere slightly reaching a maximum rate of -0.1 K day-1 at 6 km.

  12. Efficient force feedback transmission system for tele surgery.

    PubMed

    Natarajan, Sriram; Ganz, Aura

    2008-01-01

    Remote surgery information requires quick and reliable transmission between the surgeon and the patient side. However, the interconnecting network is usually time varying and lossy which can cause packet loss and delay jitter. In this paper we introduce an adaptive packet prediction and buffer time adjustment algorithm which reduces the negative effects caused by the time varying networks on the transmission of force feedback data. To evaluate our scheme we run a virtual reality applet built in Matlab. Our results show, for severe packet loss and variable delay jitter, the integrated synchronization technique significantly improves the performance of the force feedback device. PMID:19163399

  13. Air Force F-16 Aircraft Engine Aerosol Emissions Under Cruise Altitude Conditions

    NASA Technical Reports Server (NTRS)

    Anderson, Bruce E.; Cofer, W. Randy, III; McDougal, David S.

    1999-01-01

    Selected results from the June 1997 Third Subsonic Assessment Near-Field Interactions Flight (SNIF-III) Experiment are documented. The primary objectives of the SNIF-III experiment were to determine the partitioning and abundance of sulfur species and to examine the formation and growth of aerosol particles in the exhaust of F-16 aircraft as a function of atmospheric and aircraft operating conditions and fuel sulfur concentration. This information is, in turn, being used to address questions regarding the fate of aircraft fuel sulfur impurities and to evaluate the potential of their oxidation products to perturb aerosol concentrations and surface areas in the upper troposphere. SNIF-III included participation of the Vermont and New Jersey Air National Guard F-16's as source aircraft and the Wallops Flight Facility T-39 Sabreliner as the sampling platform. F-16's were chosen as a source aircraft because they are powered by the modern F-100 Series 220 engine which is projected to be representative of future commercial aircraft engine technology. The T-39 instrument suite included sensors for measuring volatile and non-volatile condensation nuclei (CN), aerosol size distributions over the range from 0.1 to 3.0 (micro)m, 3-D winds, temperature, dewpoint, carbon dioxide (CO2), sulfur dioxide (SO2), sulfuric acid (H2SO4), and nitric acid (HNO3).

  14. High-solids paint overspray aerosols in a spray painting booth: particle size analysis and scrubber efficiency

    SciTech Connect

    Chan, T.L.; D'arcy, J.B.; Schreck, R.M.

    1986-07-01

    Particle size distributions of high-solids acrylic-enamel paint overspray aerosols were determined isokinetically in a typical downdraft spray painting booth in which a 7-stage cascade impactor was used. Three different industrial paint atomizers were used, and the paint aerosols were characterized before and after a paint both scrubber. The mass median aerodynamic diameter (MMAD) of a metallic basecoat and an acrylic clearcoat paint aerosol from air-atomized spray guns ranged from 4-12 ..mu..m and was dependent on atomization pressure. When the paint booth was operated under controlled conditions simulating those in a plant, the collection efficiency of paint overspray aerosols by a paint scrubber was found to be size dependent and decreased sharply for particles smaller than 2 ..mu..m to as low as 64% for clearcoat paint particles of 0.6 ..mu..m. Improvement in the overall particulate removal efficiency can be achieved by optimizing the spray painting operations so as to produce the least amount of fine overspray paint aerosols less than 2 ..mu..m. Maintaining a higher static pressure drop across the paint both scrubber also will improve scrubber performance.

  15. AEROSOL DEPOSITION EFFICIENCIES AND UPSTREAM RELEASE POSITIONS FOR DIFFERENT INHALATION MODES IN AN UPPER BRONCHIAL AIRWAY MODELS

    EPA Science Inventory

    Aerosol Deposition Efficiencies and Upstream Release Positions for Different Inhalation Modes in an Upper Bronchial Airway Model

    Zhe Zhang, Clement Kleinstreuer, and Chong S. Kim

    Center for Environmental Medicine and Lung Biology, University of North Carolina at Ch...

  16. Whole-atmosphere aerosol microphysics simulations of the Mt Pinatubo eruption: Part 2: Quantifying the direct and indirect (dynamical) radiative forcings

    NASA Astrophysics Data System (ADS)

    Mann, Graham; Dhomse, Sandip; Carslaw, Ken; Chipperfield, Martyn; Lee, Lindsay; Emmerson, Kathryn; Abraham, Luke; Telford, Paul; Pyle, John; Braesicke, Peter; Bellouin, Nicolas; Dalvi, Mohit; Johnson, Colin

    2016-04-01

    The Mt Pinatubo volcanic eruption in June 1991 injected between 10 and 20 Tg of sulphur dioxide into the tropical lower stratosphere. Following chemical conversion to sulphuric acid, the stratospheric aerosol layer thickened substantially causing a strong radiative, dynamical and chemical perturbation to the Earth's atmosphere with effects lasting several years. In this presentation we show results from model experiments to isolate the different ways the enhanced stratospheric aerosol from Pinatubo influenced the Earth's climate. The simulations are carried out in the UK Chemistry and Aerosol composition-climate model (UKCA) which extends the high-top (to 80km) version of the UK Met Office Unified Model (UM). The UM-UKCA model uses the GLOMAP-mode aerosol microphysics module coupled with a stratosphere-troposphere chemistry scheme including sulphur chemistry. By running no-feedback and standard integrations, we separate the main radiative forcings due to aerosol-radiation interactions (i.e. the direct forcings) from those induced by dynamical changes which alter meridional heat transport and distributions of aerosol, ozone and water vapour.

  17. CCN activation and efficiency of nucleation and impaction removal process of biomass burning aerosols in Brazil: preliminary results.

    NASA Astrophysics Data System (ADS)

    Sánchez Gácita, Madeleine; Longo, Karla M.; Freitas, Saulo R.; Martin, Scot T.

    2015-04-01

    The biomass burning activity constitutes an important source of aerosols and trace gases to the atmosphere globally. In South America, during the dry season, aerosols prevenient from biomass burning are typically transported to long distances from its sources before being removed though contributing significantly to the aerosol budget on a continental scale. The uncertainties in the magnitude of the impacts on the hydrological cycle, the radiation budget and the biogeochemical cycles on a continental scale are still noteworthy. The still unknowns on the efficiency of biomass burning aerosol to act as cloud condensation nuclei (CCN) and the effectiveness of the nucleation and impaction scavenging mechanisms in removing them from the atmosphere contribute to such uncertainties. In the present work, the explicit modelling of the early stages of cloud development using a parcel model for the typical conditions of the dry season and dry-to-wet transition periods in Amazonia allowed an estimation of the efficiency of nucleation scavenging process and the ability of South American biomass burning aerosol to act as CCN. Additionally, the impaction scavenging was simulated for the same aerosol population following a method based on the widely used concept of the efficiency of collision between a raindrop and an aerosol particle. DMPS and H-TDMA data available in the literature for biomass burning aerosol population in the region indicated the presence of a nearly hydrophobic fraction (on average, with specific hygroscopic parameter κ=0.04, and relative abundance of 73 %) and nearly hygroscopic fraction (κ=0.13, 27 %), externally mixed. The hygroscopic parameters and relative abundances of each hygroscopic group, as well as the weighted average specific hygroscopic parameter for the entire population κ=0.06, were used in calculations of aerosol activation and population mass and number concentration scavenged by nucleation. Results from both groups of simulations are

  18. Long-term aerosol-mediated changes in cloud radiative forcing of deep clouds at the top and bottom of the atmosphere over the Southern Great Plains

    NASA Astrophysics Data System (ADS)

    Yan, Hongru; Li, Zhanqing; Huang, Jianping; Cribb, Maureen; Liu, Jianjun

    2014-02-01

    Aerosols can alter the macro- and micro-physical properties of deep convective clouds (DCC) and their radiative forcing (CRF). This study presents what is arguably the first long-term estimate of the aerosol-mediated changes in CRF (AMCRF) for deep cloud systems derived from decade-long continuous ground-based and satellite observations, model simulations and reanalysis data. Measurements were made at the US Department of Energy's Atmospheric Radiation Measurement Program's Southern Great Plains (SGP) site. Satellite retrievals are from the Geostationary Operational Environmental Satellite (GOES). Increases in aerosol loading were accompanied by the thickening of DCC cores and the expansion and thinning of anvils, due presumably to the aerosol invigoration effect (AIV) and the aerosol microphysical effect (AME). Meteorological variables dictating these cloud processes were investigated. Consistent with previous findings, the AIV is most significant when the atmosphere is moist and unstable with weak wind shear. Such aerosol-mediated systematic changes in DCC core thickness and anvil size alter CRF at the top of atmosphere (TOA) and at the surface. Using extensive observations, ~300 DCC systems were identified over a 10 yr period at the SGP site (2000-2011) and analyzed. Daily mean AMCRF at the TOA and at the surface are 29.3 W m-2 and 22.2 W m-2, respectively. This net warming effect due to changes in DCC microphysics offsets the cooling resulting from the first aerosol indirect effect.

  19. Long-term aerosol-mediated changes in cloud radiative forcing of deep clouds at the top and bottom of the atmosphere over the Southern Great Plains

    NASA Astrophysics Data System (ADS)

    Yan, Hongru; Li, Zhanqing; Huang, Jianping; Cribb, Maureen; Liu, Jianjun

    2014-07-01

    Aerosols can alter the macro- and micro-physical properties of deep convective clouds (DCCs) and their radiative forcing (CRF). This study presents what is arguably the first long-term estimate of the aerosol-mediated changes in CRF (AMCRF) for deep cloud systems derived from decade-long continuous ground-based and satellite observations, model simulations, and reanalysis data. Measurements were made at the US Department of Energy's Atmospheric Radiation Measurement Program's Southern Great Plains (SGP) site. Satellite retrievals are from the Geostationary Operational Environmental Satellite. Increases in aerosol loading were accompanied by the thickening of DCC cores and the expansion and thinning of anvils, due presumably to the aerosol invigoration effect (AIV) and the aerosol microphysical effect. Meteorological variables dictating these cloud processes were investigated. Consistent with previous findings, the AIV is most significant when the atmosphere is moist and unstable with weak wind shear. Such aerosol-mediated systematic changes in DCC core thickness and anvil size alter CRF at the top of atmosphere (TOA) and at the surface. Using extensive observations, ~300 DCC systems were identified over a 10 years period at the SGP site (2000-2011) and analyzed. Daily mean AMCRF at the TOA and at the surface are 29.3 W m-2 and 22.2 W m-2, respectively. This net warming effect due to changes in DCC microphysics offsets the cooling resulting from the first aerosol indirect effect.

  20. Axial force and efficiency tests of fixed center variable speed belt drive

    NASA Technical Reports Server (NTRS)

    Bents, D. J.

    1981-01-01

    An investigation of how the axial force varies with the centerline force at different speed ratios, speeds, and loads, and how the drive's transmission efficiency is affected by these related forces is described. The tests, intended to provide a preliminary performance and controls characterization for a variable speed belt drive continuously variable transmission (CVT), consisted of the design and construction of an experimental test rig geometrically similar to the CVT, and operation of that rig at selected speed ratios and power levels. Data are presented which show: how axial forces exerted on the driver and driven sheaves vary with the centerline force at constant values of speed ratio, speed, and output power; how the transmission efficiency varies with centerline force and how it is also a function of the V belt coefficient; and the axial forces on both sheaves as normalized functions of the traction coefficient.

  1. Confronting the "Indian summer monsoon response to black carbon aerosol" with the uncertainty in its radiative forcing and beyond

    NASA Astrophysics Data System (ADS)

    Kovilakam, Mahesh; Mahajan, Salil

    2016-07-01

    While black carbon aerosols (BC) are believed to modulate the Indian monsoons, the radiative forcing estimate of BC suffers from large uncertainties globally. We analyze a suite of idealized experiments forced with a range of BC concentrations that span a large swath of the latest estimates of its global radiative forcing. Within those bounds of uncertainty, summer precipitation over the Indian region increases nearly linearly with the increase in BC burden. The linearity holds even as the BC concentration is increased to levels resembling those hypothesized in nuclear winter scenarios, despite large surface cooling over India and adjoining regions. The enhanced monsoonal circulation is associated with a linear increase in the large-scale meridional tropospheric temperature gradient. The precipitable water over the region also increases linearly with an increase in BC burden, due to increased moisture transport from the Arabian sea to the land areas. The wide range of Indian monsoon response elicited in these experiments emphasizes the need to reduce the uncertainty in BC estimates to accurately quantify their role in modulating the Indian monsoons. The increase in monsoonal circulation in response to large BC concentrations contrasts earlier findings that the Indian summer monsoon may break down following a nuclear war.

  2. Pacific trade winds accelerated by aerosol forcing over the past two decades

    NASA Astrophysics Data System (ADS)

    Takahashi, Chiharu; Watanabe, Masahiro

    2016-08-01

    The Pacific trade winds, coupled with the zonal sea surface temperature gradient in the equatorial Pacific Ocean, control regional sea levels, and therefore their trend is a great concern in the Pacific Rim. Over the past two decades, easterly winds have been accelerated in association with eastern tropical Pacific cooling. They may represent natural interdecadal variability in the Pacific and possibly explain the recent global warming hiatus. However, the intensification of the winds has been the strongest ever observed in the past century, the reason for which is still unclear. Here we show, using multiple climate simulations for 1921-2014 by a global climate model, that approximately one-third of the trade-wind intensification for 1991-2010 can be attributed to changes in sulfate aerosols. The multidecadal sea surface temperature anomaly induced mostly by volcanic aerosols dominates in the western North Pacific, and its sign changed rapidly from negative to positive in the 1990s, coherently with Atlantic multidecadal variability. The western North Pacific warming resulted in intensification of trade winds to the west of the dateline. These trends have not contributed much to the global warming hiatus, but have greatly impacted rainfall over the western Pacific islands.

  3. Direct radiative forcing and atmospheric absorption by boundary layer aerosols in the southeastern US: model estimates on the basis of new observations

    NASA Astrophysics Data System (ADS)

    Yu, Shaocai; Zender, Charles S.; Saxena, V. K.

    In an effort to reduce uncertainties in the quantification of aerosol direct radiative forcing (ADRF) in the southeastern United States (US), a field column experiment was conducted to measure aerosol radiative properties and effects at Mt. Mitchell, North Carolina, and at an adjacent valley site. The experimental period was from June 1995 to mid-December 1995. The aerosol optical properties (single scattering albedo and asymmetry factor) needed to compute ADRF were obtained on the basis of a procedure involving a Mie code and a radiative transfer code in conjunction with the retrieved aerosol size distribution, aerosol optical depth, and diffuse-to-direct solar irradiance ratio. The regional values of ADRF at the surface and top of atmosphere (TOA), and atmospheric aerosol absorption are derived using the obtained aerosol optical properties as inputs to the column radiation model (CRM) of the community climate model (CCM3). The cloud-free instantaneous TOA ADRFs for highly polluted (HP), marine (M) and continental (C) air masses range from 20.3 to -24.8, 1.3 to -10.4, and 1.9 to -13.4 W m -2, respectively. The mean cloud-free 24-h ADRFs at the TOA (at the surface) for HP, M, and C air masses are estimated to be -8±4 (-33±16), -7±4 (-13±8), and -0.14±0.05 (-8±3) W m -2, respectively. On the assumption that the fractional coverage of clouds is 0.61, the annual mean ADRFs at the TOA and the surface are -2±1, and -7±2 W m -2, respectively. This also implies that aerosols currently heat the atmosphere over the southeastern US by 5±3 W m -2 on annual timescales due to the aerosol absorption in the troposphere.

  4. Air Force Achieves Fuel Efficiency through Industry Best Practices

    SciTech Connect

    2012-12-01

    The U.S. Air Force’s Air Mobility Command (AMC) is changing the way it does business. It is saving energy and money through an aircraft fleet fuel-efficiency program inspired by private industry best practices and ideas resulting from the empowered fuel savings culture.

  5. The spatial distribution of mineral dust and its shortwave radiative forcing over North Africa. Modeling sensitivities to dust emissions and aerosol size treatments

    SciTech Connect

    Zhao, Chun; Liu, Xiaohong; Leung, Lai-Yung R.; Johnson, Ben; McFarlane, Sally A.; Gustafson, William I.; Fast, Jerome D.; Easter, Richard C.

    2010-09-20

    A fully coupled meteorology-chemistry-aerosol model (WRF-Chem) with the implementation of two dust emission schemes (GOCART and DUSTRAN) into two aerosol models (MADE/SORGAM and MOSAIC) is applied over North Africa to investigate the modeling sensitivities to dust emissions and aerosol size treatments in simulating mineral dust and its shortwave (SW) radiative forcing. Model results of the spatial distribution of mineral dust and its radiative forcing are evaluated using measurements from the AMMA SOP0 campaign in January and February of 2006 over North Africa. Our study suggests that the size distribution of emitted dust can result in significant differences (up to 100%) in simulating mineral dust and its SW radiative forcing. With the same dust emission and dry deposition processes, two aerosol models, MADE/SORGAM and MOSAIC, can yield large difference in size distributions of dust particles due to their different aerosol size treatments using modal and sectional approaches respectively. However, the difference between the two aerosol models in simulating the mass concentrations and the SW radiative forcing of mineral dust is small (< 10%). The model simulations show that mineral dust increases AOD by a factor of 2, heats the lower atmosphere (1-3 km) with a maximum rate of 0.7±0.5 K day-1 below 1 km, and reduces the downwelling SW radiation by up to 25 W m-2 on 24-hour average at surface, highlighting the importance of including dust radiative impact in understanding the regional climate of North Africa. When compared to the available measurements, WRF-Chem simulations can generally capture the measured features of mineral dust and its radiative properties over North Africa, suggesting that the model can be used to perform more extensive simulations of regional climate over North Africa.

  6. A novel methodology for large-scale daily assessment of the direct radiative forcing of smoke aerosols

    NASA Astrophysics Data System (ADS)

    Sena, E. T.; Artaxo, P.

    2015-05-01

    A new methodology was developed for obtaining daily retrievals of the direct radiative forcing of aerosols (24h-DARF) at the top of the atmosphere (TOA) using satellite remote sensing. Simultaneous CERES (Clouds and Earth's Radiant Energy System) shortwave flux at the top of the atmosphere and MODIS (Moderate Resolution Spectroradiometer) aerosol optical depth (AOD) retrievals were used. To analyse the impact of forest smoke on the radiation balance, this methodology was applied over the Amazonia during the peak of the biomass burning season from 2000 to 2009. To assess the spatial distribution of the DARF, background smoke-free scenes were selected. The fluxes at the TOA under clean conditions (Fcl) were estimated as a function of the illumination geometry (θ0) for each 0.5° x 0.5° grid cell. The instantaneous DARF was obtained as the difference between the clean (Fcl (θ0)) and the polluted flux at the TOA measured by CERES in each cell (Fpol (θ0)). The radiative transfer code SBDART (Santa Barbara DISORT Radiative Transfer model) was used to expand instantaneous DARFs to 24 h averages. This new methodology was applied to assess the DARF both at high temporal resolution and over a large area in Amazonia. The spatial distribution shows that the mean 24h-DARF can be as high as -30 W m-2 over some regions. The temporal variability of the 24h-DARF along the biomass burning season was also studied and showed large intraseasonal and interannual variability. We showed that our methodology considerably reduces statistical sources of uncertainties in the estimate of the DARF, when compared to previous approaches. DARF assessments using the new methodology agree well with ground-based measurements and radiative transfer models. This demonstrates the robustness of the new proposed methodology for assessing the radiative forcing for biomass burning aerosols. To our knowledge, this is the first time that satellite remote sensing assessments of the DARF have been compared

  7. Optical properties and chemical composition of aerosol particles at an urban location: An estimation of the aerosol mass scattering and absorption efficiencies

    NASA Astrophysics Data System (ADS)

    Titos, G.; Foyo-Moreno, I.; Lyamani, H.; Querol, X.; Alastuey, A.; Alados-Arboledas, L.

    2012-02-01

    We investigated aerosol optical properties, mass concentration and chemical composition over a 1 year period (from March 2006 to February 2007) at an urban site in Southern Spain (Granada, 37.18°N, 3.58°W, 680 m above sea level). Light-scattering and absorption measurements were performed using an integrating nephelometer and a MultiAngle Absorption Photometer (MAAP), respectively, with no aerosol size cut-off and without any conditioning of the sampled air. PM10 and PM1 (ambient air levels of atmospheric particulate matter finer than 10 and 1 microns) were collected with two high volume samplers, and the chemical composition was investigated for all samples. Relative humidity (RH) within the nephelometer was below 50% and the weighting of the filters was also at RH of 50%. PM10 and PM1 mass concentrations showed a mean value of 44 ± 19 μg/m3 and 15 ± 7 μg/m3, respectively. The mineral matter was the major constituent of the PM10-1 fraction (contributing more than 58%) whereas organic matter and elemental carbon (OM+EC) contributed the most to the PM1 fraction (around 43%). The absorption coefficient at 550 nm showed a mean value of 24 ± 9 Mm-1 and the scattering coefficient at 550 nm presented a mean value of 61 ± 25 Mm-1, typical of urban areas. Both the scattering and the absorption coefficients exhibited the highest values during winter and the lowest during summer, due to the increase in the anthropogenic contribution and the lower development of the convective mixing layer during winter. A very low mean value of the single scattering albedo of 0.71 ± 0.07 at 550 nm was calculated, suggesting that urban aerosols in this site contain a large fraction of absorbing material. Mass scattering and absorption efficiencies of PM10 particles exhibited larger values during winter and lower during summer, showing a similar trend to PM1 and opposite to PM10-1. This seasonality is therefore influenced by the variations on PM composition. In addition, the mass

  8. Experimental study of elementary collection efficiency of aerosols by spray: Design of the experimental device

    SciTech Connect

    Ducret, D.; Vendel, J.; Garrec. S.L.

    1995-02-01

    The safety of a nuclear power plant containment building, in which pressure and temperature could increase because of a overheating reactor accident, can be achieved by spraying water drops. The spray reduces the pressure and the temperature levels by condensation of steam on cold water drops. The more stringent thermodynamic conditions are a pressure of 5.10{sup 5} Pa (due to steam emission) and a temperature of 413 K. Moreover its energy dissipation function, the spray leads to the washout of fission product particles emitted in the reactor building atmosphere. The present study includes a large program devoted to the evaluation of realistic washout rates. The aim of this work is to develop experiments in order to determine the collection efficiency of aerosols by a single drop. To do this, the experimental device has to be designed with fundamental criteria:-Thermodynamic conditions have to be representative of post-accident atmosphere. Thermodynamic equilibrium has to be attained between the water drops and the gaseous phase. Thermophoretic, diffusiophoretic and mechanical effects have to be studied independently. Operating conditions have to be homogenous and constant during each experiment. This paper presents the design of the experimental device. In practice, the consequences on the design of each of the criteria given previously and the necessity of being representative of the real conditions will be described.

  9. The Role of Local and Remote Anthropogenic Aerosol Forcing on Long-term Variations in the South Asian Monsoon Annual Cycle

    NASA Astrophysics Data System (ADS)

    Bollasina, M. A.; Ming, Y.; Ramaswamy, V.

    2013-12-01

    Detection and attribution of long-term variations of the South Asian monsoon is of extreme importance: even small changes in the onset and duration of the monsoon season or in the spatial distribution of the seasonal mean precipitation may severely impact agriculture, health, water availability, ecosystems, and economy for a substantial fraction of the world's population. In the past decades emissions of aerosols have dramatically increased over South Asia due to rapid urbanization and population growth. As a result, the study of the impact of anthropogenic aerosols on the monsoon has recently emerged as one of the topics of highest priority in the scientific community. This study makes use of a state-of-the-art coupled climate model, the GFDL CM3, to investigate two aspects of the aerosol influence on the observed late 20th century changes in the monsoon annual cycle. The model has fully-interactive aerosols and a representation of both direct and indirect aerosol effects. Aerosols are responsible for an earlier shift of the monsoon onset over India, leading, in agreement with observations, to enhanced precipitation in June over most parts of the subcontinent. Our experiments show that the shift is preceded in early spring by strong aerosol forcing over the Bay of Bengal and Indochina, mostly attributable to the direct effect, resulting in increased atmospheric stability that inhibits the monsoon migration in May. The adjusted atmospheric circulation leads to thermodynamical changes over the northwestern continental region, including increased surface heating and near-surface moist static energy, which support a stronger June flow and, facilitated by a relative warming of the Indian Ocean, a vigorous northwestward precipitation shift. These findings underscore the importance of dynamical feedbacks and regional land-surface processes for the aerosol-monsoon link. We also performed historical experiments with time-evolving radiative forcings aimed at isolating the

  10. Carbonaceous aerosols recorded in a southeastern Tibetan glacier: analysis of temporal variations and model estimates of sources and radiative forcing

    SciTech Connect

    Wang, Mo; Xu, B.; Cao, J.; Tie, X.; Wang, Hailong; Zhang, Rudong; Qian, Yun; Rasch, Philip J.; Zhao, Shuyu; Wu, Guangjian; Zhao, Huabiao; Joswiak, Daniel R.; Li, Jiule; Xie, Ying

    2015-02-02

    High temporal resolution measurements of black carbon (BC) and organic carbon (OC) covering the time period of 1956–2006 in an ice core over the southeastern Tibetan Plateau show a distinct seasonal dependence of BC and OC with higher respective concentrations but a lower OC / BC ratio in the non-monsoon season than during the summer monsoon. We use a global aerosol-climate model, in which BC emitted from different source regions can be explicitly tracked, to quantify BC source–receptor relationships between four Asian source regions and the southeastern Tibetan Plateau as a receptor. The model results show that South Asia has the largest contribution to the present-day (1996–2005) mean BC deposition at the ice-core drilling site during the non-monsoon season (October to May) (81%) and all year round (74%), followed by East Asia (14% to the non-monsoon mean and 21% to the annual mean). The ice-core record also indicates stable and relatively low BC and OC deposition fluxes from the late 1950s to 1980, followed by an overall increase to recent years. This trend is consistent with the BC and OC emission inventories and the fuel consumption of South Asia (as the primary contributor to annual mean BC deposition). Moreover, the increasing trend of the OC / BC ratio since the early 1990s indicates a growing contribution of coal combustion and/or biomass burning to the emissions. The estimated radiative forcing induced by BC and OC impurities in snow has increased since 1980, suggesting an increasing potential influence of carbonaceous aerosols on the Tibetan glacier melting and the availability of water resources in the surrounding regions. Our study indicates that more attention to OC is merited because of its non-negligible light absorption and the recent rapid increases evident in the ice-core record.

  11. Carbonaceous aerosols recorded in a southeastern Tibetan glacier: analysis of temporal variations and model estimates of sources and radiative forcing

    DOE PAGES

    Wang, Mo; Xu, B.; Cao, J.; Tie, X.; Wang, Hailong; Zhang, Rudong; Qian, Yun; Rasch, Philip J.; Zhao, Shuyu; Wu, Guangjian; et al

    2015-02-02

    High temporal resolution measurements of black carbon (BC) and organic carbon (OC) covering the time period of 1956–2006 in an ice core over the southeastern Tibetan Plateau show a distinct seasonal dependence of BC and OC with higher respective concentrations but a lower OC / BC ratio in the non-monsoon season than during the summer monsoon. We use a global aerosol-climate model, in which BC emitted from different source regions can be explicitly tracked, to quantify BC source–receptor relationships between four Asian source regions and the southeastern Tibetan Plateau as a receptor. The model results show that South Asia hasmore » the largest contribution to the present-day (1996–2005) mean BC deposition at the ice-core drilling site during the non-monsoon season (October to May) (81%) and all year round (74%), followed by East Asia (14% to the non-monsoon mean and 21% to the annual mean). The ice-core record also indicates stable and relatively low BC and OC deposition fluxes from the late 1950s to 1980, followed by an overall increase to recent years. This trend is consistent with the BC and OC emission inventories and the fuel consumption of South Asia (as the primary contributor to annual mean BC deposition). Moreover, the increasing trend of the OC / BC ratio since the early 1990s indicates a growing contribution of coal combustion and/or biomass burning to the emissions. The estimated radiative forcing induced by BC and OC impurities in snow has increased since 1980, suggesting an increasing potential influence of carbonaceous aerosols on the Tibetan glacier melting and the availability of water resources in the surrounding regions. Our study indicates that more attention to OC is merited because of its non-negligible light absorption and the recent rapid increases evident in the ice-core record.« less

  12. Aerosol-induced changes in summer rainfall and circulation in the Australasian region: a study using single-forcing climate simulations

    NASA Astrophysics Data System (ADS)

    Rotstayn, L. D.; Jeffrey, S. J.; Collier, M. A.; Dravitzki, S. M.; Hirst, A. C.; Syktus, J. I.; Wong, K. K.

    2012-02-01

    We use a coupled atmosphere-ocean global climate model (CSIRO-Mk3.6) to investigate the roles of different forcing agents as drivers of summer rainfall trends in the Australasian region. Our results suggest that anthropogenic aerosols have contributed to the observed multi-decadal rainfall increase over north-western Australia. As part of the Coupled Model Intercomparison Project Phase 5 (CMIP5), we performed multiple 10-member ensembles of historical climate change, which are analysed for the period 1951-2010. The historical runs include ensembles driven by "all forcings" (HIST), all forcings except anthropogenic aerosols (NO_AA) and forcing only from long-lived greenhouse gases (GHGAS). Anthropogenic aerosol-induced effects in a warming climate are calculated from the difference of HIST minus NO_AA. We also compare a 10-member 21st century ensemble driven by Representative Concentration Pathway 4.5 (RCP4.5). Simulated aerosol-induced rainfall trends over the Indo-Pacific region for austral summer and boreal summer show a distinct contrast. In boreal summer, there is a southward shift of equatorial rainfall, consistent with the idea that anthropogenic aerosols have suppressed Asian monsoonal rainfall, and caused a southward shift of the local Hadley circulation. In austral summer, the aerosol-induced response more closely resembles a westward shift and strengthening of the upward branch of the Walker circulation, rather than a coherent southward shift of regional tropical rainfall. Thus the mechanism by which anthropogenic aerosols may affect Australian summer rainfall is unclear. Focusing on summer rainfall trends over north-western Australia (NWA), we find that CSIRO-Mk3.6 simulates a strong rainfall decrease in RCP4.5, whereas simulated trends in HIST are weak and insignificant during 1951-2010. The weak rainfall trends in HIST are due to compensating effects of different forcing agents: there is a significant decrease in GHGAS, offset by an aerosol

  13. Efficiency of five chemical protective clothing materials against nano and submicron aerosols when submitted to mechanical deformations.

    PubMed

    Ben Salah, Mehdi; Hallé, Stéphane; Tuduri, Ludovic

    2016-01-01

    Due to their potential toxicity, the use of nanoparticles in the workplace is a growing concern. Some studies indicate that nanoparticles can penetrate the skin and lead to adverse health effects. Since chemical protective clothing is the last barrier to protect the skin, this study aims to better understand nanoparticle penetration behaviour in dermal protective clothing under mechanical deformation. For this purpose, five of the most common types of fabrics used in protective clothing, one woven and four nonwoven, were chosen and submitted to different simulated exposure conditions. They were tested against polydispersed NaCl aerosols having an electrical-mobility diameter between 14 and 400 nm. A bench-scale exposure setup and a sampling protocol was developed to measure the level of penetration of the aerosols through the material samples of disposable coveralls and lab coat, while subjecting them to mechanical deformations to simulate the conditions of usage in the workplace. Particle size distribution of the aerosol was determined upstream and downstream using a scanning mobility particle sizer (SMPS). The measured efficiencies demonstrated that the performances of nonwoven materials were similar. Three nonwovens had efficiencies above 99%, while the woven fabric was by far, the least effective. Moreover, the results established that mechanical deformations, as simulated for this study, did not have a significant effect on the fabrics' efficiencies.

  14. Laboratory studies of collection efficiency of sub-micrometer aerosol particles by cloud droplets on a single droplet basis

    NASA Astrophysics Data System (ADS)

    Ardon-Dryer, K.; Huang, Y.-W.; Cziczo, D. J.

    2015-03-01

    An experimental setup has been constructed to measure the Collection Efficiency (CE) of sub-micrometer aerosol particles by cloud droplets. Water droplets of a dilute aqueous ammonium sulfate solution with a radius of ~20 μm fall freely into a chamber and collide with sub-micrometer Polystyrene Latex Sphere (PSL) particles of variable size and concentrations. Two RH conditions, ~15 and ~88%, hereafter termed "Low" and "High", respectively, were varied with different particles size and concentrations. After passing through the chamber, the droplets and aerosol particles were sent to the Particle Analysis by Laser Mass Spectrometry (PALMS) instrument to determine chemical compositions on a single particle basis. Coagulated droplets had mass spectra that contain signatures from both an aerosol particle and a droplet residual. CE values range from 5.7 × 10-3 to 4.6 × 10-2 for the Low RH and from 6.4 × 10-3 to 2.2 × 10-2 for the High RH cases. CE values were, within experimental uncertainty, independent of the aerosol concentrations. CE values in this work were found to be in agreement with previous experimental and theoretical studies. To our knowledge, this is the first coagulation experiment performed on a single droplet basis.

  15. Particle Characterization and Ice Nucleation Efficiency of Field-Collected Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Wang, B.; Gilles, M. K.; Laskin, A.; Moffet, R.; Nizkorodov, S.; Roedel, T.; Sterckx, L.; Tivanski, A.; Knopf, D. A.

    2011-12-01

    Atmospheric ice formation by heterogeneous nucleation is one of the least understood processes resulting in cirrus and mixed-phase clouds which affect the global radiation budget, the hydrological cycle, and water vapor distribution. In particular, how organic aerosol affect ice nucleation is not well understood. Here we report on heterogeneous ice nucleation from particles collected during the CalNex campaign at the Caltech campus site, Pasadena, on May 19, 2010 at 6am-12pm (A2) and 12pm-6pm (A3) and May 23 at 6am-12pm (B2) and 6pm-12am (B4). The ice nucleation onsets and water uptake were determined as a function of temperature (200-273 K) and relative humidity with respect to ice (RHice). The ice nucleation efficiency was related to the particle chemical composition. Single particle characterization was provided by using computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX) and scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). The STXM/NEXAFS analysis indicates that the morning sample (A2) constitutes organic particles and organic particles with soot and inorganic inclusions. The afternoon sample (A3) is dominated by organic particles with a potentially higher degree of oxidation associated with soot. The B2 sample shows a higher number fraction of magnesium-containing particle indicative of a marine source and ~93% of the particles contained sulfur besides oxygen and carbon as derived from CCSEM/EDX analysis. The B4 sample lacks the strong marine influence and shows higher organic content. Above 230 K, we observed water uptake followed by condensation freezing at mean RH of 93-100% and 89-95% for A2 and A3, respectively. This indicates that the aged A3 particles are efficient ice nuclei (IN) for condensation freezing. Below 230 K A2 and A3 induced deposition ice nucleation between 125-155% RHice (at mean values of 134-150% RHice). The B2 and B4

  16. Evaluating the skill of high-resolution WRF-Chem simulations in describing drivers of aerosol direct climate forcing on the regional scale

    NASA Astrophysics Data System (ADS)

    Crippa, P.; Sullivan, R. C.; Thota, A.; Pryor, S. C.

    2016-01-01

    Assessing the ability of global and regional models to describe aerosol optical properties is essential to reducing uncertainty in aerosol direct radiative forcing in the contemporary climate and to improving confidence in future projections. Here we evaluate the performance of high-resolution simulations conducted using the Weather Research and Forecasting model with coupled with Chemistry (WRF-Chem) in capturing spatiotemporal variability of aerosol optical depth (AOD) and the Ångström exponent (AE) by comparison with ground- and space-based remotely sensed observations. WRF-Chem is run over eastern North America at a resolution of 12 km for a representative year (2008). A systematic positive bias in simulated AOD relative to observations is found (annual mean fractional bias (MFB) is 0.15 and 0.50 relative to MODIS (MODerate resolution Imaging Spectroradiometer) and AERONET, respectively), whereas the spatial variability is well captured during most months. The spatial correlation of observed and simulated AOD shows a clear seasonal cycle with highest correlation during summer months (r = 0.5-0.7) when the aerosol loading is large and more observations are available. The model is biased towards the simulation of coarse-mode aerosols (annual MFB for AE = -0.10 relative to MODIS and -0.59 for AERONET), but the spatial correlation for AE with observations is 0.3-0.5 during most months, despite the fact that AE is retrieved with higher uncertainty from the remote-sensing observations. WRF-Chem also exhibits high skill in identifying areas of extreme and non-extreme aerosol loading, and its ability to correctly simulate the location and relative intensity of extreme aerosol events (i.e., AOD > 75th percentile) varies between 30 and 70 % during winter and summer months, respectively.

  17. Aerosol Direct Radiative Forcing in the Southern Appalachian Mountains: Initial Results from the Appalachian Atmospheric Interdisciplinary Research (AppalAIR) Facility

    NASA Astrophysics Data System (ADS)

    Taubman, B.; Sherman, J.; Sheridan, P. J.; Perry, L. B.; Neufeld, H.; Emanuel, R. E.; Tashakkori, R.; Bowman, D.; Long, C.

    2009-12-01

    AppalAIR (Appalachian Atmospheric Interdisciplinary Research, http://appalair.appstate.edu/) is a new interdisciplinary, atmospheric research facility located on the campus of Appalachian State University (1076 m; 36.2° N, 81.7° W) in the southern Appalachian Mountains. The facility was designed to investigate air pollution formation and transport, the relationships among biogenic and anthropogenic inputs to a changing climate, and the effects of these factors on regional ecosystems. AppalAIR is a collaborating member of the NOAA Earth System Research Laboratory Global Monitoring Division (NOAA/ESRL GMD) Collaborative Global Aerosol Network (http://www.esrl.noaa.gov/gmd/aero/net/app/index.html). Measurements are made from a 34 m tower and include aerosol light scattering (3-λ nephelometer) and absorption (3-λ PSAP, 7-λ aethalometer, 6-λ UV aethalometer), particle number concentration (CPC), and aerosol chemistry, size, and morphology using SPME/GC-MS and SEM analyses on 24 h filter samples. Initial results indicate alternating periods of small, highly absorptive (ssa < 0.90) fractal agglomerates and large, highly scattering (ssa > 0.95) spherical particles that are strongly dependent upon the highly variably meteorological patterns that have occurred over the summertime (JJA) in the southeastern U.S. By quantifying the aerosol direct radiative forcing during discrete meteorological patterns as defined by statistical cluster analysis as well as from specific aerosol chemical sources, we are able to extrapolate the results beyond the immediate region.

  18. Recovery efficiency and limit of detection of aerosolized Bacillus anthracis Sterne from environmental surface samples.

    PubMed

    Estill, Cheryl Fairfield; Baron, Paul A; Beard, Jeremy K; Hein, Misty J; Larsen, Lloyd D; Rose, Laura; Schaefer, Frank W; Noble-Wang, Judith; Hodges, Lisa; Lindquist, H D Alan; Deye, Gregory J; Arduino, Matthew J

    2009-07-01

    After the 2001 anthrax incidents, surface sampling techniques for biological agents were found to be inadequately validated, especially at low surface loadings. We aerosolized Bacillus anthracis Sterne spores within a chamber to achieve very low surface loading (ca. 3, 30, and 200 CFU per 100 cm(2)). Steel and carpet coupons seeded in the chamber were sampled with swab (103 cm(2)) or wipe or vacuum (929 cm(2)) surface sampling methods and analyzed at three laboratories. Agar settle plates (60 cm(2)) were the reference for determining recovery efficiency (RE). The minimum estimated surface concentrations to achieve a 95% response rate based on probit regression were 190, 15, and 44 CFU/100 cm(2) for sampling steel surfaces and 40, 9.2, and 28 CFU/100 cm(2) for sampling carpet surfaces with swab, wipe, and vacuum methods, respectively; however, these results should be cautiously interpreted because of high observed variability. Mean REs at the highest surface loading were 5.0%, 18%, and 3.7% on steel and 12%, 23%, and 4.7% on carpet for the swab, wipe, and vacuum methods, respectively. Precision (coefficient of variation) was poor at the lower surface concentrations but improved with increasing surface concentration. The best precision was obtained with wipe samples on carpet, achieving 38% at the highest surface concentration. The wipe sampling method detected B. anthracis at lower estimated surface concentrations and had higher RE and better precision than the other methods. These results may guide investigators to more meaningfully conduct environmental sampling, quantify contamination levels, and conduct risk assessment for humans.

  19. Synthesis of Spherical Carbon Nitride-Based Polymer Composites by Continuous Aerosol-Photopolymerization with Efficient Light Harvesting.

    PubMed

    Poostforooshan, Jalal; Badiei, Alireza; Kolahdouz, Mohammadreza; Weber, Alfred P

    2016-08-24

    Here we report a novel, facile, and sustainable approach for the preparation of spherical submicrometer carbon nitride-based polymer composites by a continuous aerosol-photopolymerization process. In this regard, spherical mesoporous carbon nitride (SMCN) nanoparticles were initially prepared via a nanocasting approach using spray-drying synthesized spherical mesoporous silica (SMS) nanoparticles as hard templates. In addition to experimental characterization, the effect of porosity on the light absorption enhancement and consequently the generation rate of electron-hole pairs inside the SMCN was simulated using a three-dimensional finite difference time-domain (FDTD) method. To produce the carbon nitride-based polymer composite, SMCN nanoparticles exhibit excellent performance in photopolymerization of butyl acrylate (PBuA) monomer in the presence of n-methyldiethanolamine (MDEA) as a co-initiator in a continuous aerosol-based process. In this one-pot synthesis, SMCN nanoparticles act not only as photoinitiators but at the same time as fillers and templates. The average aerosol residence time in the photoreactor is about 90 s. The presented aerosol-photopolymerization process avoids the need for solvent and surfactant, operates at room temperature, and, more importantly, is suitable to produce the spherical composite with hydrophobic polymers. Furthermore, we simulated the condition of SMCN nanoparticles during illumination in the gas phase process, which can freely rotate. The results demonstrated that the hole (h(+)) density is almost equally distributed in the whole part of the SMCN nanoparticles due to their rotation, leading to efficient light harvesting and more homogeneous photoreaction. The combination of the outstanding features of environmentally friendly SMCN, photopolymerization, and aerosol processing might open new avenues, especially in green chemistry, to produce novel polymer composites with multifunctional properties. PMID:27483090

  20. Synthesis of Spherical Carbon Nitride-Based Polymer Composites by Continuous Aerosol-Photopolymerization with Efficient Light Harvesting.

    PubMed

    Poostforooshan, Jalal; Badiei, Alireza; Kolahdouz, Mohammadreza; Weber, Alfred P

    2016-08-24

    Here we report a novel, facile, and sustainable approach for the preparation of spherical submicrometer carbon nitride-based polymer composites by a continuous aerosol-photopolymerization process. In this regard, spherical mesoporous carbon nitride (SMCN) nanoparticles were initially prepared via a nanocasting approach using spray-drying synthesized spherical mesoporous silica (SMS) nanoparticles as hard templates. In addition to experimental characterization, the effect of porosity on the light absorption enhancement and consequently the generation rate of electron-hole pairs inside the SMCN was simulated using a three-dimensional finite difference time-domain (FDTD) method. To produce the carbon nitride-based polymer composite, SMCN nanoparticles exhibit excellent performance in photopolymerization of butyl acrylate (PBuA) monomer in the presence of n-methyldiethanolamine (MDEA) as a co-initiator in a continuous aerosol-based process. In this one-pot synthesis, SMCN nanoparticles act not only as photoinitiators but at the same time as fillers and templates. The average aerosol residence time in the photoreactor is about 90 s. The presented aerosol-photopolymerization process avoids the need for solvent and surfactant, operates at room temperature, and, more importantly, is suitable to produce the spherical composite with hydrophobic polymers. Furthermore, we simulated the condition of SMCN nanoparticles during illumination in the gas phase process, which can freely rotate. The results demonstrated that the hole (h(+)) density is almost equally distributed in the whole part of the SMCN nanoparticles due to their rotation, leading to efficient light harvesting and more homogeneous photoreaction. The combination of the outstanding features of environmentally friendly SMCN, photopolymerization, and aerosol processing might open new avenues, especially in green chemistry, to produce novel polymer composites with multifunctional properties.

  1. Force.

    ERIC Educational Resources Information Center

    Gamble, Reed

    1989-01-01

    Discusses pupil misconceptions concerning forces. Summarizes some of Assessment of Performance Unit's findings on meaning of (1) force, (2) force and motion in one dimension and two dimensions, and (3) Newton's second law. (YP)

  2. Lip Forces and Chewing Efficiency in Children with Peripheral Facial Paralysis.

    PubMed

    Ilea, Aranka; Cristea, Alexandru; Dudescu, Cristian M; Hurubeanu, Lucia; Vâjâean, Cosmin; Albu, Silviu; Câmpian, Radu S

    2015-08-01

    Peripheral facial paralysis is accompanied by facial motor disorders and also, by oral dysfunctions. The aim of this study was to evaluate the lip forces and chewing efficiency in a group of children with peripheral facial paralysis. The degree of peripheral facial paralysis in the study group (n 11) was assessed using the House-Brackmann scale. The control group consisted of 21 children without facial nerve impairment. To assess lip forces, acrylic vestibular plates of three sizes were used: large (LVP), medium (MVP) and small (SVP). The lip force was recorded with a force transducer coupled with the data acquisition system. Masticatory efficiency was evaluated by the ability to mix two differently colored chewing gums. The images were processed with Adobe Photoshop CS3 (Delaware Corporation, San Jose, California, United States) and the number of pixels was quantified with the Image J software (DHHS/NIH/NIMH/RSB, Maryland, United States). For statistical analysis, the following statistical analysis were used: Pearson or Spearman correlation coefficient, multiple linear regression analysis, multiple logistic regression analysis, and optimal cutoff values for muscular dysfunction. There were statistically significant differences between lip forces in the following three groups: p=0.01 (LVP), p=0.01 (MVP), and p=0.008 (SVP). The cutoff values of lip forces in the study group were as follows: 7.08 N (LVP), 4.89 N (MVP), and 4.24 N (SVP). There were no statistically significant differences between the masticatory efficiency in the two groups (p=0.25). Lip forces were dependent on the degree of peripheral facial paralysis and age, but not on gender. In peripheral facial paralysis in children, a significant decrease of lip forces, but not masticatory efficiency, occurs.

  3. Aerosol mixing state, hygroscopic growth and cloud activation efficiency during MIRAGE 2006

    NASA Astrophysics Data System (ADS)

    Lance, S.; Raatikainen, T.; Onasch, T. B.; Worsnop, D. R.; Yu, X.-Y.; Alexander, M. L.; Stolzenburg, M. R.; McMurry, P. H.; Smith, J. N.; Nenes, A.

    2013-05-01

    Observations of aerosol hygroscopic growth and CCN activation spectra for submicron particles are reported for the T1 ground site outside of Mexico City during the MIRAGE 2006 campaign. κ-Köhler theory is used to evaluate the characteristic hygroscopicity parameter, κ*, for the CCN active aerosol population using both size-resolved HTMDA and size-resolved CCNc measurements. Organic mass fractions (forg) are evaluated from size-resolved aerosol mass spectrometer (AMS) measurements, from which predictions of the hygroscopicity parameter are compared against κ*. Strong diurnal changes in aerosol water uptake parameters and aerosol composition are observed. We find that new particle formation (NPF) events are correlated with an increased κ* and CCN-active fraction during the daytime, with greater impact on smaller particles. During NPF events, the number concentration of 40 nm particles acting as CCN at 0.51% ± 0.06% supersaturation can surpass by more than a factor of two the corresponding concentrations of 100 nm particles. We also find that at 06:00-08:00 LT throughout the campaign, fresh traffic emissions result in substantial changes to the chemical distribution of the aerosol, with on average 65% externally mixed fraction for 40 nm particles and 30% externally mixed fraction for 100 nm particles, whereas at midday nearly all particles of both sizes can be described as "internally mixed". Average activation spectra and growth factor distributions are analyzed for different time periods characterizing the daytime (with and without NPF events), the early morning "rush hour" and the entire campaign. We show that κ* derived from CCNc measurements decreases as a function of size during all time periods, while the CCN-active fraction increases as a function of size. Size-resolved AMS measurements do not predict the observed trend for κ* versus particle size, which can be attributed to unresolved mixing state and the presence of refractory material not measured

  4. Aerosol-based efficient delivery of azithromycin to alveolar macrophages for treatment of respiratory infections.

    PubMed

    Togami, Kohei; Chono, Sumio; Morimoto, Kazuhiro

    2013-01-01

    The efficacy of aerosol-based delivery of azithromycin (AZM) for the treatment of respiratory infections caused by pathogenic microorganisms infected in alveolar macrophages (AMs) was evaluated by comparison with oral administration. The aerosol formulation of AZM (0.2 mg/kg) was administered to rat lungs using a Liquid MicroSprayer(®). The oral formulation of AZM (50 mg/kg) was used for comparison. Time-courses of concentrations of AZM in AMs following administration were obtained, and then the therapeutic availability (TA) was calculated. In addition, the area under the concentrations of AZM in AMs - time curve/minimum inhibitory concentration at which 90% of isolates ratio (AUC/MIC90) were calculated to estimate the antibacterial effects in AMs. The TA of AZM in AMs following administration of aerosol formulation was markedly greater than that following administration of oral formulation. In addition, the AUC/MIC90 of AZM in AMs was markedly higher than the effective values. This indicates that the aerosol formulation could be useful for the treatment of respiratory infections caused by pathogenic microorganisms infected in AMs. This study suggests that aerosolized AZM is an effective pulmonary drug delivery system for the treatment of respiratory infections.

  5. Seasonality of meningitis in Africa and climate forcing: aerosols stand out

    PubMed Central

    Agier, L.; Deroubaix, A.; Martiny, N.; Yaka, P.; Djibo, A.; Broutin, H.

    2013-01-01

    Bacterial meningitis is an ongoing threat for the population of the African Meningitis Belt, a region characterized by the highest incidence rates worldwide. The determinants of the disease dynamics are still poorly understood; nevertheless, it is often advocated that climate and mineral dust have a large impact. Over the last decade, several studies have investigated this relationship at a large scale. In this analysis, we scaled down to the district-level weekly scale (which is used for in-year response to emerging epidemics), and used wavelet and phase analysis methods to define and compare the time-varying periodicities of meningitis, climate and dust in Niger. We mostly focused on detecting time-lags between the signals that were consistent across districts. Results highlighted the special case of dust in comparison to wind, humidity or temperature: a strong similarity between districts is noticed in the evolution of the time-lags between the seasonal component of dust and meningitis. This result, together with the assumption of dust damaging the pharyngeal mucosa and easing bacterial invasion, reinforces our confidence in dust forcing on meningitis seasonality. Dust data should now be integrated in epidemiological and forecasting models to make them more realistic and usable in a public health perspective. PMID:23221989

  6. Implementation of the Missing Aerosol Physics into LLNL IMPACT

    SciTech Connect

    Chuang, C

    2005-02-09

    In recent assessments of climate forcing, the Intergovernmental Panel on Climate Change lists aerosol as one o f the most important anthropogenic agents that influence climate. Atmospheric aerosols directly affect the radiative fluxes at the surface and top of the Earth's atmosphere by scattering and/or absorbing radiation. Further, aerosols indirectly change cloud microphysical properties (such as cloud drop effective radius) that also affect the radiative fluxes. However, the estimate of the magnitude of aerosol climatic effect varies widely, and aerosol/cloud interactions remain one of the most uncertain aspects of climate models today. The Atmospheric Sciences Division has formulated a plan to enhance and expand our modeling expertise in aerosol/cloud/climate interactions. Under previous LDRD support, we successfully developed a computationally efficient version of IMPACT to simulate aerosol climatology. This new version contains a compact chemical mechanism for the prediction of sulfate and also predicts the distributions of organic carbon (OC), black carbon (BC), dust, and sea salt. Furthermore, we implemented a radiation package into IMPACT to calculate the radiative forcing and heating/cooling rates by aerosols. This accomplishment built the foundation of our currently funded projects under the NASA Global Modeling and Analysis Program as well as the DOE Atmospheric Radiation Program. Despite the fact that our research is being recognized as an important effort to quantify the effects of anthropogenic aerosols on climate, the major shortcoming of our previous simulations on aerosol climatic effects is the over simplification of spatial and temporal variations of aerosol size distributions that are shaped by complicated nucleation, growth, transport and removal processes. Virtually all properties of atmospheric aerosols and clouds depend strongly on aerosol size distribution. Moreover, molecular processing on aerosol surfaces alters the hygroscopic

  7. Influence of balancing holes and disc sealing in turbine stages on thermodynamic efficiency and rotor forces

    NASA Astrophysics Data System (ADS)

    Sláma, Václav

    2016-03-01

    This paper deals with CFD analysis of a particular turbine impulse stage including the surrounding parts such as diaphragm seals, shroud seals and a disc axial gap, where balancing holes and a disc sealing is designed. The aim is to investigate effects on efficiency and axial forces by evaluation of a pressure distribution on the rotor disc and respective mass flow balances. As a result of this, the possible methodology of design optimization could be found. The other part of the project is to find the way for a more exact preliminary computation which is essential for increasing efficiency and the reduction of the axial forces.

  8. Improvement of force factor of magnetostrictive vibration power generator for high efficiency

    SciTech Connect

    Kita, Shota Ueno, Toshiyuki; Yamada, Sotoshi

    2015-05-07

    We develop high power magnetostrictive vibration power generator for battery-free wireless electronics. The generator is based on a cantilever of parallel beam structure consisting of coil-wound Galfenol and stainless plates with permanent magnet for bias. Oscillating force exerted on the tip bends the cantilever in vibration yields stress variation of Galfenol plate, which causes flux variation and generates voltage on coil due to the law of induction. This generator has advantages over conventional, such as piezoelectric or moving magnet types, in the point of high efficiency, highly robust, and low electrical impedance. Our concern is the improvement of energy conversion efficiency dependent on the dimension. Especially, force factor, the conversion ratio of the electromotive force (voltage) on the tip velocity in vibration, has an important role in energy conversion process. First, the theoretical value of the force factor is formulated and then the validity was verified by experiments, where we compare four types of prototype with parameters of the dimension using 7.0 × 1.5 × 50 mm beams of Galfenol with 1606-turn wound coil. In addition, the energy conversion efficiency of the prototypes depending on load resistance was measured. The most efficient prototype exhibits the maximum instantaneous power of 0.73 W and energy of 4.7 mJ at a free vibration of frequency of 202 Hz in the case of applied force is 25 N. Further, it was found that energy conversion efficiency depends not only on the force factor but also on the damping (mechanical loss) of the vibration.

  9. Improvement of force factor of magnetostrictive vibration power generator for high efficiency

    NASA Astrophysics Data System (ADS)

    Kita, Shota; Ueno, Toshiyuki; Yamada, Sotoshi

    2015-05-01

    We develop high power magnetostrictive vibration power generator for battery-free wireless electronics. The generator is based on a cantilever of parallel beam structure consisting of coil-wound Galfenol and stainless plates with permanent magnet for bias. Oscillating force exerted on the tip bends the cantilever in vibration yields stress variation of Galfenol plate, which causes flux variation and generates voltage on coil due to the law of induction. This generator has advantages over conventional, such as piezoelectric or moving magnet types, in the point of high efficiency, highly robust, and low electrical impedance. Our concern is the improvement of energy conversion efficiency dependent on the dimension. Especially, force factor, the conversion ratio of the electromotive force (voltage) on the tip velocity in vibration, has an important role in energy conversion process. First, the theoretical value of the force factor is formulated and then the validity was verified by experiments, where we compare four types of prototype with parameters of the dimension using 7.0 × 1.5 × 50 mm beams of Galfenol with 1606-turn wound coil. In addition, the energy conversion efficiency of the prototypes depending on load resistance was measured. The most efficient prototype exhibits the maximum instantaneous power of 0.73 W and energy of 4.7 mJ at a free vibration of frequency of 202 Hz in the case of applied force is 25 N. Further, it was found that energy conversion efficiency depends not only on the force factor but also on the damping (mechanical loss) of the vibration.

  10. Estimate of the Saharan dust shortwave and photosynthetic radiative forcing efficiency at the surface during the propagation of a gravity wave in the central Mediterranean

    NASA Astrophysics Data System (ADS)

    di Sarra, Alcide; Fuà, Daniele; Meloni, Daniela

    2013-04-01

    This study is based on measurements made at ENEA Station for Climate Observations (35.52° N, 12.63° E, 50 m asl) on the island of Lampedusa, in the Southern part of the Central Mediterranean. A quasi periodic oscillation of aerosol optical depth, column water vapour, shortwave (SW) and photosynthetic active radiation (PAR) is observed to occur during the morning of 7 September 2005. The quasi-periodic wave is present from about 6 to 10 UT, with solar zenith angles (SZA) varying between 77.5° and 37.2° . In this period the aerosol optical depth at 500 nm, ?, varies between 0.29 and 0.41; the column water vapour, cwv, varies between 2.4 and 2.8 cm. The oscillations of ? and cwv are in phase, while the modulation of the downward surface irradiances is in opposition of phase with respect to ? and cwv. The period of the oscillation is about 13 min. The oscillation is attributed to the propagation of a gravity wave which modulates the structure of the planetary boundary layer. The measured aerosol optical properties are typical of cases dominated by Saharan dust, with the Ångström exponent comprised between 0.5 and 0.6. The backtrajectory analysis for that day shows that airmasses overpass Northern Libya (trajectories arriving below 2000 m), Tunisia and Northern Algeria (trajectories arriving above 2000 m), carrying Saharan dust particles to Lampedusa. The combined modulation of downward irradiance, water vapour column, and aerosol optical depth is used to estimate the aerosol effect on the irradiance. From the irradiance-optical depth relation, the aerosol surface direct forcing efficiency (FE) is derived, under the assumption that during the measurement interval the aerosol microphysical properties do not appreciably change. As a first step, all SW irradiances are reported to the same cwv content (2.6 cm), by using radiative transfer model calculations. Reference curves describing the downward SW and PAR irradiances are constructed by using measurements obtained

  11. The economics and ethics of aerosol geoengineering strategies

    NASA Astrophysics Data System (ADS)

    Goes, Marlos; Keller, Klaus; Tuana, Nancy

    2010-05-01

    Anthropogenic greenhouse gas emissions are changing the Earth's climate and impose substantial risks for current and future generations. What are scientifically sound, economically viable, and ethically defendable strategies to manage these climate risks? Ratified international agreements call for a reduction of greenhouse gas emissions to avoid dangerous anthropogenic interference with the climate system. Recent proposals, however, call for a different approach: geoengineering climate by injecting aerosol precursors into the stratosphere. Published economic studies typically neglect the risks of aerosol geoengineering due to (i) a potential failure to sustain the aerosol forcing and (ii) due to potential negative impacts associated with aerosol forcings. Here we use a simple integrated assessment model of climate change to analyze potential economic impacts of aerosol geoengineering strategies over a wide range of uncertain parameters such as climate sensitivity, the economic damages due to climate change, and the economic damages due to aerosol geoengineering forcings. The simplicity of the model provides the advantages of parsimony and transparency, but it also imposes considerable caveats. For example, the analysis is based on a globally aggregated model and is hence silent on intragenerational distribution of costs and benefits. In addition, the analysis neglects the effects of future learning and is based on a simple representation of climate change impacts. We use this integrated assessment model to show three main points. First, substituting aerosol geoengineering for the reduction of greenhouse gas emissions can fail the test of economic efficiency. One key to this finding is that a failure to sustain the aerosol forcing can lead to sizeable and abrupt climatic changes. The monetary damages due to such a discontinuous aerosol geoengineering can dominate the cost-benefit analysis because the monetary damages of climate change are expected to increase with

  12. Aerosol distribution apparatus

    DOEpatents

    Hanson, W.D.

    An apparatus for uniformly distributing an aerosol to a plurality of filters mounted in a plenum, wherein the aerosol and air are forced through a manifold system by means of a jet pump and released into the plenum through orifices in the manifold. The apparatus allows for the simultaneous aerosol-testing of all the filters in the plenum.

  13. Aerosol- and greenhouse gas-induced changes in summer rainfall and circulation in the Australasian region: a study using single-forcing climate simulations

    NASA Astrophysics Data System (ADS)

    Rotstayn, L. D.; Jeffrey, S. J.; Collier, M. A.; Dravitzki, S. M.; Hirst, A. C.; Syktus, J. I.; Wong, K. K.

    2012-07-01

    We use a coupled atmosphere-ocean global climate model (CSIRO-Mk3.6) to investigate the drivers of trends in summer rainfall and circulation in the vicinity of northern Australia. As part of the Coupled Model Intercomparison Project Phase 5 (CMIP5), we perform a 10-member 21st century ensemble driven by Representative Concentration Pathway 4.5 (RCP4.5). To investigate the roles of different forcing agents, we also perform multiple 10-member ensembles of historical climate change, which are analysed for the period 1951-2010. The historical runs include ensembles driven by "all forcings" (HIST), all forcings except anthropogenic aerosols (NO_AA) and forcing only from long-lived greenhouse gases (GHGAS). Anthropogenic aerosol-induced effects in a warming climate are calculated from the difference of HIST minus NO_AA. CSIRO-Mk3.6 simulates a strong summer rainfall decrease over north-western Australia (NWA) in RCP4.5, whereas simulated trends in HIST are weakly positive (but insignificant) during 1951-2010. The weak rainfall trends in HIST are due to compensating effects of different forcing agents: there is a significant decrease in GHGAS, offset by an aerosol-induced increase. Observations show a significant increase of summer rainfall over NWA during the last few decades. The large magnitude of the observed NWA rainfall trend is not captured by 440 unforced 60-yr trends calculated from a 500-yr pre-industrial control run, even though the model's decadal variability appears to be realistic. This suggests that the observed trend includes a forced component, despite the fact that the model does not simulate the magnitude of the observed rainfall increase in response to "all forcings" (HIST). We investigate the mechanism of simulated and observed NWA rainfall changes by exploring changes in circulation over the Indo-Pacific region. The key circulation feature associated with the rainfall increase in reanalyses is a lower-tropospheric cyclonic circulation trend off the

  14. A HTAP Multi-Model Assessment of the Influence of Regional Anthropogenic Emission Reductions on Aerosol Direct Radiative Forcing and the Role of Intercontinental Transport

    NASA Technical Reports Server (NTRS)

    Yu, Hongbin; Chin, Mian; West, J. Jason; Atherton, Cynthia S.; Bellouin, Nicolas; Bergmann, Dan; Bey, Isabelle; Bian, Huisheng; Diehl, Thomas; Forberth, Gerd; Hess, Peter; Schulz, Michael; Shindell, Drew; Takemura, Toshihiko; Tan, Qian

    2012-01-01

    In this study, we assess changes of aerosol optical depth (AOD) and direct radiative forcing (DRF) in response to the reduction of anthropogenic emissions in four major pollution regions in the northern hemisphere by using results from 10 global chemical transport models in the framework of the Hemispheric Transport of Air Pollution (HTAP). The multi-model results show that on average, a 20% reduction of anthropogenic emissions in North America, Europe, East Asia and South Asia lowers the global mean AOD and DRF by about 9%, 4%, and 10% for sulfate, organic matter, and black carbon aerosol, respectively. The impacts of the regional emission reductions on AOD and DRF extend well beyond the source regions because of intercontinental transport. On an annual basis, intercontinental transport accounts for 10-30% of the overall AOD and DRF in a receptor region, with domestic emissions accounting for the remainder, depending on regions and species. While South Asia is most influenced by import of sulfate aerosol from Europe, North America is most influenced by import of black carbon from East Asia. Results show a large spread among models, highlighting the need to improve aerosol processes in models and evaluate and constrain models with observations.

  15. Hand-rim forces and gross mechanical efficiency in asynchronous and synchronous wheelchair propulsion: a comparison.

    PubMed

    Lenton, J P; van der Woude, L; Fowler, N; Nicholson, G; Tolfrey, K; Goosey-Tolfrey, V

    2014-03-01

    To compare the force application characteristics at various push frequencies of asynchronous (ASY) and synchronous (SYN) hand-rim propulsion, 8 able-bodied participants performed a separate sub-maximal exercise test on a wheelchair roller ergometer for each propulsion mode. Each test consisted of a series of 5, 4-min exercise blocks at 1.8 m · s-1 - initially at their freely chosen frequency (FCF), followed by four counter-balanced trials at 60, 80, 120 and 140% FCF. Kinetic data was obtained using a SMARTWheel, measuring forces and moments. The gross efficiency (GE) was determined as the ratio of external work done and the total energy expended. The ASY propulsion produced higher force measures for FRES, FTAN, rate of force development & FEF (P<0.05), while there was no difference in GE values (P=0.518). In pair-matched push frequencies (ASY80:SYN60, ASY100:SYN80, ASY120:SYN100 and ASY140:SYN120), ASY propulsion forces remained significantly higher (FRES, FTAN, rate of force development & FEF P<0.05), and there was no significant effect on GE (P=0.456). Both ASY and SYN propulsion demonstrate similar trends: changes in push frequency are accompanied by changes in absolute force even without changes in the gross pattern/trend of force application, FEF or GE. Matched push frequencies continue to produce significant differences in force measures but not GE. This suggests ASY propulsion is the predominant factor in force application differences. The ASY would appear to offer a kinetic disadvantage to SYN propulsion and no physiological advantage under current testing conditions.

  16. Heterogeneous Chemistry: Understanding Aerosol/Oxidant Interactions

    SciTech Connect

    Joyce E. Penner

    2005-03-14

    Global radiative forcing of nitrate and ammonium aerosols has mostly been estimated from aerosol concentrations calculated at thermodynamic equilibrium or using approximate treatments for their uptake by aerosols. In this study, a more accurate hybrid dynamical approach (DYN) was used to simulate the uptake of nitrate and ammonium by aerosols and the interaction with tropospheric reactive nitrogen chemistry in a three-dimensional global aerosol and chemistry model, IMPACT, which also treats sulfate, sea salt and mineral dust aerosol. 43% of the global annual average nitrate aerosol burden, 0.16 TgN, and 92% of the global annual average ammonium aerosol burden, 0.29 TgN, exist in the fine mode (D<1.25 {micro}m) that scatters most efficiently. Results from an equilibrium calculation differ significantly from those of DYN since the fraction of fine-mode nitrate to total nitrate (gas plus aerosol) is 9.8%, compared to 13% in DYN. Our results suggest that the estimates of aerosol forcing from equilibrium concentrations will be underestimated. We also show that two common approaches used to treat nitrate and ammonium in aerosol in global models, including the first-order gas-to-particle approximation based on uptake coefficients (UPTAKE) and a hybrid method that combines the former with an equilibrium model (HYB), significantly overpredict the nitrate uptake by aerosols especially that by coarse particles, resulting in total nitrate aerosol burdens higher than that in DYN by +106% and +47%, respectively. Thus, nitrate aerosol in the coarse mode calculated by HYB is 0.18 Tg N, a factor of 2 more than that in DYN (0.086 Tg N). Excessive formation of the coarse-mode nitrate in HYB leads to near surface nitrate concentrations in the fine mode lower than that in DYN by up to 50% over continents. In addition, near-surface HNO{sub 3} and NO{sub x} concentrations are underpredicted by HYB by up to 90% and 5%, respectively. UPTAKE overpredicts the NO{sub x} burden by 56% and near

  17. Aerosol mixingstate, hygroscopic growth and cloud activation efficiency during MIRAGE 2006

    SciTech Connect

    Lance, Sara; Raatikainen, T.; Onasch, Timothy B.; Worsnop, Douglas R.; Yu, Xiao-Ying; Alexander, M. L.; Stolzenberg, Mark; McMurry, Peter; Smith, James N.; Nenes, Athanasios

    2013-05-15

    Observations of aerosol hygroscopic growth and CCN activation spectra for submicron particles are reported for the T1 ground site outside of Mexico City during the MIRAGE 2006 campaign. K¨ohler theory is used to evaluate the characteristic water uptake coefficient, k*, for the CCN active aerosol population using both size-resolved HTMDA and size-resolved CCNc measurements. Organic mass fractions, (forg), are evaluated from size-resolved aerosol mass spectrometer (AMS) measurements, from which kAMS is inferred and compared against k*. Strong diurnal profiles of aerosol water uptake parameters and aerosol composition are observed. We find that new particle formation (NPF) events are correlated with an increased k* and CCN-active fraction during the daytime, with greater impact on smaller particles. During NPF events, the number concentration of 40 nm particles acting as CCN can surpass by more than a factor of two the concentrations of 100 nm particles acting as CCN, at supersaturations of 0.51% +/- 0.06%. We also find that at 0600-0800 in the morning throughout the campaign, fresh traffic emissions result in substantial changes to the chemical distribution of the aerosol, with on average 65% externally-mixed fraction for 40 nm particles and 30% externally-mixed fraction for 100 nm particles, whereas at midday nearly all particles of both sizes can be described as “internally-mixed”. Average activation spectra and growth factor distributions are analyzed for different time periods characterizing the daytime (with and without NPF events), the early morning “rush hour”, and the entire campaign. We show that k* derived from CCNc measurements decreases as a function of size during all time periods, while the CCN-active fraction increases as a function of size. Size-resolved AMS measurements do not predict the observed trend for k* versus particle size, which can be attributed to unresolved mixing-state and the presence of refractory material not measured by the

  18. Aerosol mixing-state, hygroscopic growth and cloud activation efficiency during MIRAGE 2006

    NASA Astrophysics Data System (ADS)

    Lance, S.; Raatikainen, T.; Onasch, T.; Worsnop, D. R.; Yu, X.-Y.; Alexander, M. L.; Stolzenburg, M. R.; McMurry, P. H.; Smith, J. N.; Nenes, A.

    2012-06-01

    Observations of aerosol hygroscopic growth and CCN activation spectra for submicron particles are reported for the T1 ground site outside of Mexico City during the MIRAGE 2006 campaign. κ-Köhler theory is used to evaluate the characteristic water uptake coefficient, κ*, for the CCN active aerosol population using both size-resolved HTDMA and size-resolved CCNc measurements. Organic mass fractions, forg, are evaluated from size-resolved aerosol mass spectrometer (AMS) measurements, from which κAMS is inferred and compared against κ*. Strong diurnal profiles of aerosol water uptake parameters and aerosol composition are observed. We find that new particle formation (NPF) events are correlated with an increased κ* and CCN-active fraction during the daytime, with greater impact on smaller particles. During NPF events, the number concentration of 40 nm particles acting as CCN can surpass by more than a factor of two the concentrations of 100 nm particles acting as CCN, at supersaturations of 0.51% ± 0.06%. We also find that at 06:00-08:00 in the morning throughout the campaign, fresh traffic emissions result in substantial changes to the chemical distribution of the aerosol, with on average 65% externally-mixed fraction for 40 nm particles and 30% externally-mixed fraction for 100 nm particles, whereas at midday nearly all particles of both sizes can be described as internally-mixed. Average activation spectra and growth factor distributions are analyzed for different time periods characterizing the daytime (with and without NPF events), the early morning "rush hour", and the entire campaign. We show that κ* derived from CCNc measurements decreases as a function of size during all time periods, while the CCN-active fraction increases as a function of size. Size-resolved AMS measurements do not predict the observed trend for κ* versus particle size, which can be attributed to unresolved mixing-state and the presence of refractory material not measured by the AMS

  19. Untangling aerosol effects on clouds and precipitation in a buffered system.

    PubMed

    Stevens, Bjorn; Feingold, Graham

    2009-10-01

    It is thought that changes in the concentration of cloud-active aerosol can alter the precipitation efficiency of clouds, thereby changing cloud amount and, hence, the radiative forcing of the climate system. Despite decades of research, it has proved frustratingly difficult to establish climatically meaningful relationships among the aerosol, clouds and precipitation. As a result, the climatic effect of the aerosol remains controversial. We propose that the difficulty in untangling relationships among the aerosol, clouds and precipitation reflects the inadequacy of existing tools and methodologies and a failure to account for processes that buffer cloud and precipitation responses to aerosol perturbations.

  20. Tropospheric Aerosols

    NASA Astrophysics Data System (ADS)

    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

  1. A review of Air Force high efficiency cascaded multiple bandgap solar cell research and development

    NASA Technical Reports Server (NTRS)

    Rahilly, W. P.

    1979-01-01

    At the time of their conception, the cell stack systems to be discussed represent the best semiconductor materials combinations to achieve Air Force program goals. These systems are investigated thoroughly and the most promising systems, from the standpoint of high efficiency, are taken for further development with large area emphasized (at least 4 sq cm). The emphasis in the Air Force cascaded cell program is placed on eventual nonconcentrator application. This use of the final cell design considerably relieves the low resistance requirements for the tunnel junction. In a high concentration application the voltage drop across the tunnel junction can be a very serious problem.

  2. Organic aerosols and inorganic species from post-harvest agricultural-waste burning emissions over northern India: impact on mass absorption efficiency of elemental carbon.

    PubMed

    Rajput, Prashant; Sarin, M M; Sharma, Deepti; Singh, Darshan

    2014-01-01

    Atmospheric PM2.5 (particulate matter with aerodynamic diameter of ≤ 2.5 μm), collected from a source region [Patiala: 30.2 °N; 76.3 °E; 250 m above mean sea level] of emissions from post-harvest agricultural-waste (paddy-residue) burning in the Indo-Gangetic Plain (IGP), North India, has been studied for its chemical composition and impact on regional atmospheric radiative forcing. On average, organic aerosol mass accounts for 63% of PM2.5, whereas the contribution of elemental carbon (EC) is ∼3.5%. Sulphate, nitrate and ammonium contribute up to ∼85% of the total water-soluble inorganic species (WSIS), which constitutes ∼23% of PM2.5. The potassium-to-organic carbon ratio from paddy-residue burning emissions (KBB(+)/OC: 0.05 ± 0.01) is quite similar to that reported from Amazonian and Savanna forest-fires; whereas non-sea-salt-sulphate-to-OC ratio (nss-SO4(2-)/OC: 0.21) and nss-SO4(2-)/EC ratio of 2.6 are significantly higher (by factor of 5 to 8). The mass absorption efficiency of EC (3.8 ± 1.3 m(2) g(-1)) shows significant decrease with a parallel increase in the concentrations of organic aerosols and scattering species (sulphate and nitrate). A cross plot of OC/EC and nss-SO4(2-)/EC ratios show distinct differences for post-harvest burning emissions from paddy-residue as compared to those from fossil-fuel combustion sources in south-east Asia.

  3. Modelling of long-range transport of Southeast Asia biomass-burning aerosols to Taiwan and their radiative forcings over East Asia

    SciTech Connect

    Lin, Chuan-Yao; Zhao, Chun; Liu, Xiaohong; Lin, Neng-Huei; Chen, Wei-Nei

    2014-10-12

    Biomass burning is a major source of aerosols and air pollutants during the springtime in Southeast Asia. At Lulin mountain background station (elevation 2862 m) in Taiwan, the concentrations of carbon monoxide (CO), ozone (O3) and particulate matter particles with diameter less than 10 μm (PM10), were measured around 150-250 ppb, 40-60 ppb, and 10-30μg/m3, respectively at spring time (February-April) during 2006 and 2009, which are about 2~3 times higher than those in other seasons. Observations and simulation results indicate that the higher concentrations during the spring time are clearly related to biomass burning plumes transported from the Indochina Peninsula of Southeast Asia. The spatial distribution of high aerosols optical depth (AOD) were identified by the satellite measurement and Aerosol Robotic Network (AERONET) ground observation, and could be reasonably captured by the WRF-Chem model during the study period of 15-18 March, 2008. AOD reached as high as 0.8-1.0 in Indochina ranging from 10 to 22°N and 95 to 107°E. Organic carbon (OC) is a major contributor of AOD over Indochina according to simulation results. The contributor of AOD from black carbon (BC) is minor when compared with OC over the Indochina. However, the direct absorption radiative forcing of BC in the atmosphere could reach 35-50 W m-2, which is about 8-10 times higher than that of OC. The belt shape of radiation reduction at surface from Indochina to Taiwan could be as high 20-40 W m-2 during the study period. The implication of the radiative forcing from biomass burning aerosols and their impact on the regional climate in East Asia is our major concern.

  4. Modulation of aerosol radiative forcing due to mixing state in clear and cloudy-sky: A case study from Delhi National Capital Region, India

    NASA Astrophysics Data System (ADS)

    Srivastava, Parul; Dey, Sagnik; Srivastava, Atul K.; Singh, Sachchidanand; Tiwari, Suresh; Agarwal, Poornima

    2016-04-01

    Aerosol properties change with the change in mixing state of aerosols and therefore it is a source of uncertainty in estimated aerosol radiative forcing (ARF) from observations or by models assuming a specific mixing state. The problem is important in the Indo-Gangetic Basin, Northern India, where various aerosol types mix and show strong seasonal variations. Quantifying the modulation of ARF by mixing state is hindered by lack of knowledge about proper aerosol composition. Hence, first a detailed chemical composition analysis of aerosols for Delhi National capital region (NCR) is carried out. Aerosol composition is arranged quantitatively into five major aerosol types - accumulation dust, coarse dust, water soluble (WS), water insoluble (WINS), and black carbon (BC) (directly measured by Athelometer). Eight different mixing cases - external mixing, internal mixing, and six combinations of core- shell mixing (BC over dust, WS over dust, WS over BC, BC over WS, WS over WINS, and BC over WINS; each of the combinations externally mixed with other species) have been considered. The spectral aerosol optical properties - extinction coefficient, single scattering albedo (SSA) and asymmetry parameter (g) for each of the mixing cases are calculated and finally 'clear-sky' and 'cloudy-sky' ARF at the top-of-the-atmosphere (TOA) and surface are estimated using a radiative transfer model. Comparison of surface-reaching flux for each of the cases with MERRA downward shortwave surface flux reveals the most likely mixing state. 'BC-WINS+WS+Dust' show least deviation relative to MERRA during the pre-monsoon (MAMJ) and monsoon (JAS) seasons and hence is the most probable mixing states. During the winter season (DJF), 'BC-Dust+WS+WINS' case shows the closest match with MERRA, while external mixing is the most probable mixing state in the post-monsoon season (ON). Lowest values for both TOA and surface 'clear-sky' ARF is observed for 'BC-WINS+WS+ Dust' mixing case. TOA ARF is 0.28±2

  5. Black carbon aerosol mixing state, organic aerosols and aerosol optical properties over the United Kingdom

    NASA Astrophysics Data System (ADS)

    McMeeking, G. R.; Morgan, W. T.; Flynn, M.; Highwood, E. J.; Turnbull, K.; Haywood, J.; Coe, H.

    2011-09-01

    Black carbon (BC) aerosols absorb sunlight thereby leading to a positive radiative forcing and a warming of climate and can also impact human health through their impact on the respiratory system. The state of mixing of BC with other aerosol species, particularly the degree of internal/external mixing, has been highlighted as a major uncertainty in assessing its radiative forcing and hence its climate impact, but few in situ observations of mixing state exist. We present airborne single particle soot photometer (SP2) measurements of refractory BC (rBC) mass concentrations and mixing state coupled with aerosol composition and optical properties measured in urban plumes and regional pollution over the United Kingdom. All data were obtained using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA) operated by the Facility for Airborne Atmospheric Measurements (FAAM). We measured sub-micron aerosol composition using an aerosol mass spectrometer (AMS) and used positive matrix factorization to separate hydrocarbon-like (HOA) and oxygenated organic aerosols (OOA). We found a higher number fraction of thickly coated rBC particles in air masses with large OOA relative to HOA, higher ozone-to-nitrogen oxides (NOx) ratios and large concentrations of total sub-micron aerosol mass relative to rBC mass concentrations. The more ozone- and OOA-rich air masses were associated with transport from continental Europe, while plumes from UK cities had higher HOA and NOx and fewer thickly coated rBC particles. We did not observe any significant change in the rBC mass absorption efficiency calculated from rBC mass and light absorption coefficients measured by a particle soot absorption photometer despite observing significant changes in aerosol composition and rBC mixing state. The contributions of light scattering and absorption to total extinction (quantified by the single scattering albedo; SSA) did change for different air masses, with lower SSA

  6. Hygroscopic properties of atmospheric aerosol particles over the Eastern Mediterranean: implications for regional direct radiative forcing under clean and polluted conditions

    NASA Astrophysics Data System (ADS)

    Stock, M.; Cheng, Y. F.; Birmili, W.; Massling, A.; Wehner, B.; Müller, T.; Leinert, S.; Kalivitis, N.; Mihalopoulos, N.; Wiedensohler, A.

    2011-05-01

    This work examines the effect of direct radiative forcing of aerosols in the eastern Mediterranean troposphere as a function of air mass composition, particle size distribution and hygroscopicity, and relative humidity (RH). During intensive field measurements on the island of Crete, Greece, the hygroscopic properties of atmospheric particles were determined using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) and a Hygroscopicity Differential Mobility Analyzer-Aerodynamic Particle Sizer (H-DMA-APS). Similar to former studies, the H-TDMA identified three hygroscopic sub-fractions of particles in the sub-μm range: a more hygroscopic group, a less hygroscopic group and a nearly hydrophobic particle group. The average hygroscopic particle growth factors at 90 % RH were a significant function of particle mobility diameter (Dp): 1.42 (± 0.05) at 30 nm compared to 1.63 (± 0.07) at 250 nm. The H-DMA-APS identified up to three hygroscopic sub-fractions at mobility diameters of 1.0 and 1.2 μm. The data recorded between 12 August and 20 October 2005 were classified into four distinct synoptic-scale air mass types distinguishing between different regions of origin (western Mediterranean vs. the Aegean Sea) as well as the degree of continental pollution (marine vs. continentally influenced). The hygroscopic properties of particles with diameter Dp≥150 nm showed the most pronounced dependency on air mass origin, with growth factors in marine air masses exceeding those in continentally influenced air masses. Particle size distributions and hygroscopic growth factors were used to calculate aerosol light scattering coefficients at ambient RH using a Mie model. A main result was the pronounced enhancement of particle scattering over the eastern Mediterranean due to hygroscopic growth, both in the marine and continentally influenced air masses. When RH reached its summer daytime values around 70-80 %, up to 50-70 % of the calculated visibility reduction was

  7. Hygroscopic properties of atmospheric aerosol particles over the Eastern Mediterranean: implications for regional direct radiative forcing under clean and polluted conditions

    NASA Astrophysics Data System (ADS)

    Stock, M.; Cheng, Y. F.; Birmili, W.; Massling, A.; Wehner, B.; Müller, T.; Leinert, S.; Kalivitis, N.; Mihalopoulos, N.; Wiedensohler, A.

    2010-11-01

    This work examines the effect of direct radiative forcing of aerosols in the eastern Mediterranean troposphere as a function of air mass composition, particle size distribution and hygroscopicity, and relative humidity (RH). During intensive field measurements on the island of Crete, Greece, the hygroscopic properties of atmospheric particles were determined using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) and a Hygroscopicity Differential Mobility Analyzer - Aerodynamic Particle Sizer (H-DMA-APS). Like in several studies before, the H-TDMA identified three hygroscopic sub-fractions of particles in the sub-μm range: a more hygroscopic group, a less hygroscopic group and a nearly hydrophobic particle group. The hygroscopic particle growth factors at 90% RH were a significant function of particle mobility diameter (Dp): 1.42 (± 0.05) at 30 nm compared to 1.63 (± 0.07) at 250 nm. The H-DMA-APS identified up to three hygroscopic sub-fractions at mobility diameters of 1.0 and 1.2 μm. All data recorded between 12 August and 20 October, 2005 were classified into four distinct synoptic-scale air mass types distinguishing between different regions of origin (western Mediterranean vs. the Aegean Sea) as well as the degree of continental pollution (marine vs. continentally influenced). The hygroscopic properties of particles with diameter Dp ≥ 150 nm showed the most pronounced dependency on air mass origin, with growth factors in marine air masses exceeding those in more continentally influenced air masses. Particle size distributions and hygroscopic growth factors were employed to calculate aerosol light scattering coefficients at ambient RH using a Mie model. A main result was the pronounced enhancement of particle scattering over the eastern Mediterranean due to hygroscopic growth, both in the marine and continentally influenced air masses. When RH reached its daytime values around 70-80% in summer, up to 50-70% of the calculated visibility

  8. The forced radiation efficiency of finite size flat panels that are excited by incident sound.

    PubMed

    Davy, John L

    2009-08-01

    The radiation efficiency of an infinite flat panel that radiates a plane wave into a half space is equal to the inverse of the cosine of the angle between the direction of propagation of the plane wave and the normal to the panel. The fact that this radiation efficiency tends to infinity as the angle tends to 90 degrees causes problems with simple theories of sound insulation. Sato calculated numerical values of radiation efficiency for a finite size rectangular panel in an infinite baffle whose motion is forced by sound incident at an angle to the normal from the other side. This paper presents a simple two dimensional analytic strip theory, which agrees reasonably well with Sato's numerical calculations for a rectangular panel. This leads to the conclusion that it is mainly the length of the panel in the direction of radiation, rather than its width that is important in determining its radiation efficiency. A low frequency correction is added to the analytic strip theory. The theory is analytically integrated over all angles of incidence, with the appropriate weighting function, to obtain the diffuse sound field forced radiation efficiency of a panel. PMID:19640035

  9. Spermine-alt-poly(ethylene glycol) polyspermine as a safe and efficient aerosol gene carrier for lung cancer therapy.

    PubMed

    Kim, You-Kyoung; Cho, Chong-Su; Cho, Myung-Haing; Jiang, Hu-Lin

    2014-07-01

    The clinical success of gene therapy critically depends upon the safety and efficiency of delivery system used. Although polyethylenimine (PEI) has been commonly used as an efficient cationic polymeric gene carrier due to its high transfection efficiency, its cytotoxicity and nondegradability limit the polymer's therapeutic applications in clinical trials. In this study, biocompatible polyspermine based on spermine (SPE) and poly(ethylene glycol) (PEG) diacrylate (SPE-alt-PEG) was synthesized using a Michael-type addition reaction, and its ability as an alternative gene carrier for lung cancer therapy was evaluated. SPE-alt-PEG polyspermine was complexed with plasmid DNA, and the resulting complexes were characterized by particle size and surface charge by dynamic light scattering, complex formation and DNA protection ability by gel retardation, and complex shape by energy-filtering transmission electron microscopy. The SPE-alt-PEG copolymer showed low cytotoxicity, and SPE-alt-PEG/DNA complexes showed efficacious transfection efficiency compared with 25 kDa PEI (PEI 25K). Also SPE-alt-PEG/GFP complexes were efficiently transferred into the lungs after aerosol administration without toxicity, and delivery of Pdcd4 gene as a therapeutic gene with SPE-alt-PEG polyspermine greatly reduced tumor size as well as tumor numbers in K-ras(LA1) lung cancer model mice compared relative to the effect observed for PEI 25K. These results suggest that SPE-alt-PEG has potential as a gene carrier for lung cancer gene therapy. PMID:23929634

  10. Development of a double-layered ceramic filter for aerosol filtration at high-temperatures: the filter collection efficiency.

    PubMed

    de Freitas, Normanda L; Gonçalves, José A S; Innocentini, Murilo D M; Coury, José R

    2006-08-25

    The performance of double-layered ceramic filters for aerosol filtration at high temperatures was evaluated in this work. The filtering structure was composed of two layers: a thin granular membrane deposited on a reticulate ceramic support of high porosity. The goal was to minimize the high pressure drop inherent of granular structures, without decreasing their high collection efficiency for small particles. The reticulate support was developed using the technique of ceramic replication of polyurethane foam substrates of 45 and 75 pores per inch (ppi). The filtering membrane was prepared by depositing a thin layer of granular alumina-clay paste on one face of the support. Filters had their permeability and fractional collection efficiency analyzed for filtration of an airborne suspension of phosphatic rock in temperatures ranging from ambient to 700 degrees C. Results revealed that collection efficiency decreased with gas temperature and was enhanced with filtration time. Also, the support layer influenced the collection efficiency: the 75 ppi support was more effective than the 45 ppi. Particle collection efficiency dropped considerably for particles below 2 microm in diameter. The maximum collection occurred for particle diameters of approximately 3 microm, and decreased again for diameters between 4 and 8 microm. Such trend was successfully represented by the proposed correlation, which is based on the classical mechanisms acting on particle collection. Inertial impaction seems to be the predominant collection mechanism, with particle bouncing/re-entrainment acting as detachment mechanisms.

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

    NASA Technical Reports Server (NTRS)

    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

  12. Quantifying the climatological cloud-free shortwave direct radiative forcing of mineral dust aerosol over the Red Sea

    NASA Astrophysics Data System (ADS)

    Stenchikov, G. L.; Brindley, H. E.; Osipov, S.; Bantges, R. J.; Smirnov, A.; Prakash, P. J.

    2014-12-01

    While there have been a number of campaigns designed to probe dust-climate interactions over much of the world, relatively little attention has been paid to the Red Sea. Because of the remoteness of the area, satellite retrievals provide a crucial tool for assessing aerosol loading over the Sea. However, agreement between aerosol properties inferred from measurements from different instruments, and even in some cases from the same measurements using different retrieval algorithms can be poor, particularly in the case of mineral dust. Ground based measurements, which can be used to evaluate retrievals, are thus highly desirable. Here we take advantage of ship-based hand-held sun-photometer (microtops) observations gathered within the framework of NASA Aerosol Maritime Network from a series of cruises, which took place across the Red Sea during 2011 and 2013. To our knowledge these data represent the first set of detailed aerosol measurements from the Sea. They thus provide a unique opportunity to assess the performance of satellite retrieval algorithms in this region. Here we used the microtops measurements to evaluate the performance of co-located satellite retrievals from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and the MODerate Imaging Spectrometer (MODIS). Both algorithms show good agreement with the ship-based measurements and with each other, although it appears that the MODIS cloud detection scheme in particular is rather conservative. The stand alone Rapid Radiative Transfer Model (RRTM) driven by reanalysis meteorological fields is used to estimate the cloud-free aerosol direct radiative effect at the surface and TOA along the ship tracks. The TOA effects are compared to co-located measurements from the Geostationary Earth Radiation Budget (GERB) instrument. Having evaluated both the quality of the retrievals and the ability of the model to capture the associated radiative effect, we will present a climatology of aerosol loading over the

  13. Spatial heterogeneities in aerosol properties over Bay of Bengal inferred from ship-borne and MODIS observations during ICARB-W cruise campaign: Implications to radiative forcing

    NASA Astrophysics Data System (ADS)

    Raghavendra Kumar, K.; Narasimhulu, K.; Balakrishnaiah, G.; Suresh Kumar Reddy, B.; Rama Gopal, K.; Reddy, R. R.; Reddy, L. S. S.; Krishna Moorthy, K.; Suresh Babu, S.; Dutt, C. B. S.

    2011-01-01

    Comprehensive investigations during the last decade have clearly established that aerosols have a significant impact on the climate. This paper reports the results of the spatial variations in aerosol optical depth (AOD) and fine mode fraction (FMF) characteristics as a function of latitude and longitude over the Bay of Bengal (BoB) and the Northern Indian Ocean (NIO) during ICARB-W cruise period of 27th December 2008-30th January 2009 from onboard Sunphotometer and MODIS (Terra, Aqua) satellite measurements. Very high AOD 500 (0.7-0.8) occurred over the north head BoB adjacent to the northeastern Indian coast and the lowest AOD 500 (0.1-0.2) occurred in central BoB far away from the coasts, and in a small area in the northeastern part close to Myanmar coast as well as over NIO. The highest values (as high as 1.2) of Ångström exponent, α occurring over northeast BoB (regions close to Bangladesh and Myanmar) indicate relative abundance of accumulation mode particles and very low values of α (below 0.7) over central part of BoB as well as southern BoB/NIO suggesting dominance of coarse-mode sea spray aerosols. Terra/Aqua MODIS AOD 550 and cruise measured AOD 500 using Sunphotometer showed good agreement ( R2 = 0.92) over the BoB. The total mass concentrations over BoB during cruise period were remarkably high, with a mean value of 28.4 ± 5.7 μg m -3. Aerosol FMF was higher than 0.7 over the BoB, while FMF over NIO was about 0.5. NCEP reanalysis data on winds at 850 hPa, along with 5-days airmass back trajectories via HYSPLIT model, suggested transport of continental aerosols from the central and northern India over the BoB by the strong westerly/northwesterly winds. Regionally averaged clear sky aerosol (net) forcing over BoB during the winter is -28.9 W m -2 at the surface and -10.4 W m -2 at the top of the atmosphere whereas, the ARF values estimated over NIO at TOA, surface and in the atmosphere are -6.4, -18.3 and +11.9 W m -2, respectively.

  14. Aerosol and pollutant transport and their impact on radiative forcing over the tropical Indian Ocean during the January February 1996 pre-INDOEX cruise

    NASA Astrophysics Data System (ADS)

    Krishnamurti, T. N.; Jha, B.; Prospero, J.; Jayaraman, A.; Ramanathan, V.

    1998-11-01

    Measurements of aerosol bulk composition, optical depth, size distribution and the incoming solar radiation flux were carried out over the coastal waters of India, the Arabian sea and the tropical Indian Ocean during a cruise conducted in January 1996. Aerosol concentrations were relatively high throughout much of the cruise, even when the ship was at considerable distances from land. In this paper, we link the observed spatial variations and meridional gradients in the measurements to monsoonal and inter-hemispheric transport across the ITCZ using a high resolution global reanalysis that highlights the winter monsoon. We show that the northeast monsoonal low level flow can transport sulfates, mineral dust and other aerosols from the Indian sub-continent to the ITCZ within 6 7days. These transports result in an increase the aerosol optical depth (AOD) at the equator by as much as 0.2 and a decrease in the solar radiative forcing at the sea surface by about 10 20 Wm-2. The high concentrations of continental aerosols are a result of three factors: strong (about 6 10m/s) near-surface northerly flow; a shallow boundary layer of about 400 to 800 m thick, which traps the pollutants; subsidence, associated with the northeast monsoon, which suppresses rainfall over most of the Arabian sea and thus minimizes the wet removal process. In addition dust can be transported in the middle troposphere from the Arabian desert to the cruise region 4000km away with a transit time of 2 3days. There is strong evidence of interhemispheric transports effected by eddies that wrap around the ITCZ. These eddies bring clean southern hemisphere air to about 10°N in the Indian Ocean and carry polluted continental air into the southern-hemisphere. In this manner, substantial amounts of aerosols and other pollutants can be routinely transported to the southern-hemisphere Indian Ocean during the northeast monsoon. Thus, in order to understand the connection between continental emissions and

  15. The effect of forced expiration on the uniformity of 99Tcm-DTPA aerosol ventilation images in patients with excess sputum production.

    PubMed

    Middleton, E; Clout, C; Occleshaw, C; Tindale, W B; Parker, B V; Barber, D C; Barrington, N A

    1990-08-01

    This study examines the use of the forced expiratory technique (FET) as a means of improving the uniformity of radionuclide aerosol ventilation images in patients with excess sputum production. Ventilation images are objectively classified by two computer derived indices to characterize the degree of radioaerosol clumping and overall uniformity. In a series of twenty five patients with a long-standing history of daily sputum production, images acquired before and after forced expiration and again after a second ventilation immediately following FET showed no significant change in either index. The results obtained do not provide evidence to support the routine use of FET in conjunction with radioaerosol scintigraphy. The method of image classification correlates well with a visual assessment of image uniformity and has general application.

  16. Field Measurements of Heating Efficiency of Electric Forced-Air Furnaces in Six Manufactured Homes.

    SciTech Connect

    Davis, Bob; Palmiter, Larry S.; Siegel, Jeff

    1994-07-26

    This report presents the results of field measurements of heating efficiency for six manufactured homes in the Pacific Northwest heated with electric forced-air systems. This is the first in a series of regional and national efforts to measure in detail the heating efficiency of manufactured homes. Only six homes were included in this study because of budgetary constraints; therefore this is not a representative sample. These investigations do provide some useful information on the heating efficiency of these homes. Useful comparisons can be drawn between these study homes and site-built heating efficiencies measured with a similar protocol. The protocol used to test these homes is very similar to another Ecotope protocol used in the study conducted in 1992 and 1993 for the Bonneville Power Administration to test the heating efficiency of 24 homes. This protocol combined real-time power measurements of furnace energy usage with energy usage during co-heat periods. Accessory data such as house and duct tightness measurements and tracer gas measurements were used to describe these homes and their heating system efficiency. Ensuring that manufactured housing is constructed in an energy and resource efficient manner is of increasing concern to manufactured home builders and consumers. No comparable work has been done to measure the heating system efficiency of MCS manufactured homes, although some co-heat tests have been performed on manufactured homes heated with natural gas to validate HUD thermal standards. It is expected that later in 1994 more research of this kind will be conducted, and perhaps a less costly and less time-consuming method for testing efficiencies will be develops.

  17. The Importance of the Vertical Location of Aerosol Layers on Convective Storms

    NASA Astrophysics Data System (ADS)

    van den Heever, Susan; Grant, Leah

    2014-05-01

    Enhanced aerosol concentrations appear to influence a number of the aspects of convective storms including the strength of the convective updraft, the intensity of the cold pool, and the microphysical and radiative characteristics of the convective anvil. However, in order for such influences to occur, aerosols need to be effectively ingested by the storm system of interest. The vertical location of an aerosol layer impacting a convective storm may influence how effectively aerosol are ingested by the storm system, and hence the degree to which the ingested aerosol subsequently influence storm microphysical and radiative processes. Furthermore, if the aerosol species impacting the storm are effective at absorbing solar radiation, heating within the aerosol layer enhances atmospheric stability, the level of which will be dictated by where the aerosol layer is located. Enhanced static stability may have negative impacts on the initial development of the convection of interest. Convective storms developing within environments of the same aerosol optical depth may therefore respond differently to aerosol indirect forcing by virtue of where the aerosol layer is vertically located. In this talk, the results of various high-resolution, cloud-resolving simulations will be presented, in which the sensitivity to the vertical location of the aerosol source on the convective development, aerosol ingestion efficiency, and subsequent microphysical and radiative properties are investigated. Microphysical budgets and storm trajectories will form an integral part of the analysis.

  18. An efficient and numerically stable procedure for generating sextic force fields in normal mode coordinates.

    PubMed

    Sibaev, M; Crittenden, D L

    2016-06-01

    In this paper, we outline a general, scalable, and black-box approach for calculating high-order strongly coupled force fields in rectilinear normal mode coordinates, based upon constructing low order expansions in curvilinear coordinates with naturally limited mode-mode coupling, and then transforming between coordinate sets analytically. The optimal balance between accuracy and efficiency is achieved by transforming from 3 mode representation quartic force fields in curvilinear normal mode coordinates to 4 mode representation sextic force fields in rectilinear normal modes. Using this reduced mode-representation strategy introduces an error of only 1 cm(-1) in fundamental frequencies, on average, across a sizable test set of molecules. We demonstrate that if it is feasible to generate an initial semi-quartic force field in curvilinear normal mode coordinates from ab initio data, then the subsequent coordinate transformation procedure will be relatively fast with modest memory demands. This procedure facilitates solving the nuclear vibrational problem, as all required integrals can be evaluated analytically. Our coordinate transformation code is implemented within the extensible PyPES library program package, at http://sourceforge.net/projects/pypes-lib-ext/. PMID:27276945

  19. On improving the algorithm efficiency in the particle-particle force calculations

    NASA Astrophysics Data System (ADS)

    Kozynchenko, Alexander I.; Kozynchenko, Sergey A.

    2016-09-01

    The problem of calculating inter-particle forces in the particle-particle (PP) simulation models takes an important place in scientific computing. Such simulation models are used in diverse scientific applications arising in astrophysics, plasma physics, particle accelerators, etc., where the long-range forces are considered. The inverse-square laws such as Coulomb's law of electrostatic forces and Newton's law of universal gravitation are the examples of laws pertaining to the long-range forces. The standard naïve PP method outlined, for example, by Hockney and Eastwood [1] is straightforward, processing all pairs of particles in a double nested loop. The PP algorithm provides the best accuracy of all possible methods, but its computational complexity is O (Np2), where Np is a total number of particles involved. Too low efficiency of the PP algorithm seems to be the challenging issue in some cases where the high accuracy is required. An example can be taken from the charged particle beam dynamics where, under computing the own space charge of the beam, so-called macro-particles are used (see e.g., Humphries Jr. [2], Kozynchenko and Svistunov [3]).

  20. An efficient and numerically stable procedure for generating sextic force fields in normal mode coordinates.

    PubMed

    Sibaev, M; Crittenden, D L

    2016-06-01

    In this paper, we outline a general, scalable, and black-box approach for calculating high-order strongly coupled force fields in rectilinear normal mode coordinates, based upon constructing low order expansions in curvilinear coordinates with naturally limited mode-mode coupling, and then transforming between coordinate sets analytically. The optimal balance between accuracy and efficiency is achieved by transforming from 3 mode representation quartic force fields in curvilinear normal mode coordinates to 4 mode representation sextic force fields in rectilinear normal modes. Using this reduced mode-representation strategy introduces an error of only 1 cm(-1) in fundamental frequencies, on average, across a sizable test set of molecules. We demonstrate that if it is feasible to generate an initial semi-quartic force field in curvilinear normal mode coordinates from ab initio data, then the subsequent coordinate transformation procedure will be relatively fast with modest memory demands. This procedure facilitates solving the nuclear vibrational problem, as all required integrals can be evaluated analytically. Our coordinate transformation code is implemented within the extensible PyPES library program package, at http://sourceforge.net/projects/pypes-lib-ext/.

  1. Alignment of cellular motility forces with tissue flow as a mechanism for efficient wound healing

    PubMed Central

    Basan, Markus; Elgeti, Jens; Hannezo, Edouard; Rappel, Wouter-Jan; Levine, Herbert

    2013-01-01

    Recent experiments have shown that spreading epithelial sheets exhibit a long-range coordination of motility forces that leads to a buildup of tension in the tissue, which may enhance cell division and the speed of wound healing. Furthermore, the edges of these epithelial sheets commonly show finger-like protrusions whereas the bulk often displays spontaneous swirls of motile cells. To explain these experimental observations, we propose a simple flocking-type mechanism, in which cells tend to align their motility forces with their velocity. Implementing this idea in a mechanical tissue simulation, the proposed model gives rise to efficient spreading and can explain the experimentally observed long-range alignment of motility forces in highly disordered patterns, as well as the buildup of tensile stress throughout the tissue. Our model also qualitatively reproduces the dependence of swirl size and swirl velocity on cell density reported in experiments and exhibits an undulation instability at the edge of the spreading tissue commonly observed in vivo. Finally, we study the dependence of colony spreading speed on important physical and biological parameters and derive simple scaling relations that show that coordination of motility forces leads to an improvement of the wound healing process for realistic tissue parameters. PMID:23345440

  2. Energy-efficient utilization of bipolar optical forces in nano-optomechanical cavities.

    PubMed

    Tian, Feng; Zhou, Guangya; Du, Yu; Chau, Fook Siong; Deng, Jie; Tang, Xiaosong; Akkipeddi, Ramam

    2013-07-29

    Nanoscale all-optical circuits driven by optical forces have broad applications in future communication, computation, and sensing systems. Because human society faces huge challenges of energy saving and emission reduction, it is very important to develop energy-efficient nano-optomechanical devices. Due to their high quality (Q) factors, resonance modes of cavities are capable of generating much larger forces than waveguide modes. Here we experimentally demonstrate the use of resonance modes of double-coupled one-dimensional photonic crystal cavities to generate bipolar optical forces. Attractive and repulsive forces of -6.2 nN and 1.9 nN were obtained with respective launching powers of 0.81 mW and 0.87 mW in the waveguide just before cavities. Supported by flexible nanosprings (spring constant 0.166 N/m), one cavity is pulled to (pushed away from) the other cavity by 37.1 nm (11.4 nm). The shifts of the selected resonance modes of the device are mechanically and thermally calibrated with an integrated nanoelectromechanical system actuator and a temperature-controlled testing platform respectively. Based on these experimentally-obtained relations, probe mode shifts due to the optomechanical effect are decoupled from those due to the thermo-optic effect. Actuated by the third-order even pump mode, the optomechanical shift of the second-order even probe mode is found to be about 2.5 times its thermal shift, indicating a highly efficient conversion of light energy to mechanical energy.

  3. Heterodyne efficiency for a coherent laser radar with diffuse or aerosol targets

    NASA Technical Reports Server (NTRS)

    Frehlich, R. G.

    1993-01-01

    The performance of a Coherent Laser Radar is determined by the statistics of the coherent Doppler signal. The heterodyne efficiency is an excellent indication of performance because it is an absolute measure of beam alignment and is independent of the transmitter power, the target backscatter coefficient, the atmospheric attenuation, and the detector quantum efficiency and gain. The theoretical calculation of heterodyne efficiency for an optimal monostatic lidar with a circular aperture and Gaussian transmit laser is presented including beam misalignment in the far-field and near-field regimes. The statistical behavior of estimates of the heterodyne efficiency using a calibration hard target are considered. For space based applications, a biased estimate of heterodyne efficiency is proposed that removes the variability due to the random surface return but retains the sensitivity to misalignment. Physical insight is provided by simulation of the fields on the detector surface. The required detector calibration is also discussed.

  4. The climate impact of aviation aerosols

    NASA Astrophysics Data System (ADS)

    Gettelman, A.; Chen, C.

    2013-06-01

    A comprehensive general circulation model (GCM) is used to estimate the climate impact of aviation emissions of black carbon (BC) and sulfate (SO4) aerosols. Aviation BC is found not to exert significant radiative forcing impacts, when BC nucleating efficiencies in line with observations are used. Sulfate emissions from aircraft are found to alter liquid clouds at altitudes below emission (˜200 hPa); contributing to shortwave cloud brightening through enhanced liquid water path and drop number concentration in major flight corridors, particularly in the N. Atlantic. Global averaged sulfate direct and indirect effects on liquid clouds of 46 mWm-2are larger than the warming effect of aviation induced cloudiness of 16 mWm-2. The net result of including contrail cirrus and aerosol effects is a global averaged cooling of -21±11 mWm-2. These aerosol forcings should be considered with contrails in evaluating the total global impact of aviation on climate.

  5. Surface fractal dimension, water adsorption efficiency, and cloud nucleation activity of insoluble aerosol

    PubMed Central

    Laaksonen, Ari; Malila, Jussi; Nenes, Athanasios; Hung, Hui-Ming; Chen, Jen-Ping

    2016-01-01

    Surface porosity affects the ability of a substance to adsorb gases. The surface fractal dimension D is a measure that indicates the amount that a surface fills a space, and can thereby be used to characterize the surface porosity. Here we propose a new method for determining D, based on measuring both the water vapour adsorption isotherm of a given substance, and its ability to act as a cloud condensation nucleus when introduced to humidified air in aerosol form. We show that our method agrees well with previous methods based on measurement of nitrogen adsorption. Besides proving the usefulness of the new method for general surface characterization of materials, our results show that the surface fractal dimension is an important determinant in cloud drop formation on water insoluble particles. We suggest that a closure can be obtained between experimental critical supersaturation for cloud drop activation and that calculated based on water adsorption data, if the latter is corrected using the surface fractal dimension of the insoluble cloud nucleus. PMID:27138171

  6. Surface fractal dimension, water adsorption efficiency, and cloud nucleation activity of insoluble aerosol

    NASA Astrophysics Data System (ADS)

    Laaksonen, Ari; Malila, Jussi; Nenes, Athanasios; Hung, Hui-Ming; Chen, Jen-Ping

    2016-05-01

    Surface porosity affects the ability of a substance to adsorb gases. The surface fractal dimension D is a measure that indicates the amount that a surface fills a space, and can thereby be used to characterize the surface porosity. Here we propose a new method for determining D, based on measuring both the water vapour adsorption isotherm of a given substance, and its ability to act as a cloud condensation nucleus when introduced to humidified air in aerosol form. We show that our method agrees well with previous methods based on measurement of nitrogen adsorption. Besides proving the usefulness of the new method for general surface characterization of materials, our results show that the surface fractal dimension is an important determinant in cloud drop formation on water insoluble particles. We suggest that a closure can be obtained between experimental critical supersaturation for cloud drop activation and that calculated based on water adsorption data, if the latter is corrected using the surface fractal dimension of the insoluble cloud nucleus.

  7. Surface fractal dimension, water adsorption efficiency, and cloud nucleation activity of insoluble aerosol.

    PubMed

    Laaksonen, Ari; Malila, Jussi; Nenes, Athanasios; Hung, Hui-Ming; Chen, Jen-Ping

    2016-01-01

    Surface porosity affects the ability of a substance to adsorb gases. The surface fractal dimension D is a measure that indicates the amount that a surface fills a space, and can thereby be used to characterize the surface porosity. Here we propose a new method for determining D, based on measuring both the water vapour adsorption isotherm of a given substance, and its ability to act as a cloud condensation nucleus when introduced to humidified air in aerosol form. We show that our method agrees well with previous methods based on measurement of nitrogen adsorption. Besides proving the usefulness of the new method for general surface characterization of materials, our results show that the surface fractal dimension is an important determinant in cloud drop formation on water insoluble particles. We suggest that a closure can be obtained between experimental critical supersaturation for cloud drop activation and that calculated based on water adsorption data, if the latter is corrected using the surface fractal dimension of the insoluble cloud nucleus. PMID:27138171

  8. Surface fractal dimension, water adsorption efficiency, and cloud nucleation activity of insoluble aerosol.

    PubMed

    Laaksonen, Ari; Malila, Jussi; Nenes, Athanasios; Hung, Hui-Ming; Chen, Jen-Ping

    2016-05-03

    Surface porosity affects the ability of a substance to adsorb gases. The surface fractal dimension D is a measure that indicates the amount that a surface fills a space, and can thereby be used to characterize the surface porosity. Here we propose a new method for determining D, based on measuring both the water vapour adsorption isotherm of a given substance, and its ability to act as a cloud condensation nucleus when introduced to humidified air in aerosol form. We show that our method agrees well with previous methods based on measurement of nitrogen adsorption. Besides proving the usefulness of the new method for general surface characterization of materials, our results show that the surface fractal dimension is an important determinant in cloud drop formation on water insoluble particles. We suggest that a closure can be obtained between experimental critical supersaturation for cloud drop activation and that calculated based on water adsorption data, if the latter is corrected using the surface fractal dimension of the insoluble cloud nucleus.

  9. An efficient algorithm using matrix methods to solve wind tunnel force-balance equations

    NASA Technical Reports Server (NTRS)

    Smith, D. L.

    1972-01-01

    An iterative procedure applying matrix methods to accomplish an efficient algorithm for automatic computer reduction of wind-tunnel force-balance data has been developed. Balance equations are expressed in a matrix form that is convenient for storing balance sensitivities and interaction coefficient values for online or offline batch data reduction. The convergence of the iterative values to a unique solution of this system of equations is investigated, and it is shown that for balances which satisfy the criteria discussed, this type of solution does occur. Methods for making sensitivity adjustments and initial load effect considerations in wind-tunnel applications are also discussed, and the logic for determining the convergence accuracy limits for the iterative solution is given. This more efficient data reduction program is compared with the technique presently in use at the NASA Langley Research Center, and computational times on the order of one-third or less are demonstrated by use of this new program.

  10. [Aerosol therapy].

    PubMed

    Wildhaber, J H

    1998-08-15

    Aerosol therapy plays a major role in the diagnosis and treatment of various lung diseases. The aim of inhalation therapy is to deposit a reproducible and adequate dose of a specific drug to the airways, in order to achieve a high, local, clinical effect while avoiding serious systemic side effects. To achieve this goal, it is therefore important to have an efficient inhalation device to deliver different medications. However, the currently available therapeutic inhalation devices (nebuliser, pressurised metered-dose inhaler and dry powder inhaler) are not very efficient in aerosol delivery and have several disadvantages. Inhalation devices can be assessed by in vitro studies, filter studies and radiolabelled deposition studies. Several radiolabelled deposition studies have shown that nebulisers and pressurised metered-dose inhalers are not very efficient in aerosol delivery. In children, before 1997, only 0.5% to 15% of the total nebulised or actuated dose from a nebuliser or pressurised metered-dose inhaler actually reached the lungs. These numbers were somewhat improved in adults, 30% of the total nebulised or actuated dose reaching the airways. Aerosol therapy with dry powder inhalers was the most efficient before 1997, 30% of the total dose being deposited in the lungs of adults and children. In 1997, new developments in pressurised metered-dose inhalers much improved their efficiency in aerosol delivery. Lung deposition can be increased by up to 60% with use of a non-electrostatic holding chamber and/or a pressurised metered-dose inhaler with a hydrofluoroalkane propellant possessing superior aerosol characteristics. Several studies comparing the clinical efficiency of different inhalation devices have shown that the choice of an optimal inhalation device is crucial. In addition to the aerosol characteristics, ventilation parameters and airway morphology have an important bearing on deposition patterns. These parameters may be greatly influenced by the

  11. Efficiency of transport in periodic potentials: dichotomous noise contra deterministic force

    NASA Astrophysics Data System (ADS)

    Spiechowicz, J.; Łuczka, J.; Machura, L.

    2016-05-01

    We study the transport of an inertial Brownian particle moving in a symmetric and periodic one-dimensional potential, and subjected to both a symmetric, unbiased external harmonic force as well as biased dichotomic noise η (t) also known as a random telegraph signal or a two state continuous-time Markov process. In doing so, we concentrate on the previously reported regime (Spiechowicz et al 2014 Phys. Rev. E 90 032104) for which non-negative biased noise η (t) in the form of generalized white Poissonian noise can induce anomalous transport processes similar to those generated by a deterministic constant force F=< η (t)> but significantly more effective than F, i.e. the particle moves much faster, the velocity fluctuations are noticeably reduced and the transport efficiency is enhanced several times. Here, we confirm this result for the case of dichotomous fluctuations which, in contrast to white Poissonian noise, can assume positive as well as negative values and examine the role of thermal noise in the observed phenomenon. We focus our attention on the impact of bidirectionality of dichotomous fluctuations and reveal that the effect of nonequilibrium noise enhanced efficiency is still detectable. This result may explain transport phenomena occurring in strongly fluctuating environments of both physical and biological origin. Our predictions can be corroborated experimentally by use of a setup that consists of a resistively and capacitively shunted Josephson junction.

  12. Efficient evaluation of the Coulomb force in the Gaussian and finite-element Coulomb method

    NASA Astrophysics Data System (ADS)

    Kurashige, Yuki; Nakajima, Takahito; Sato, Takeshi; Hirao, Kimihiko

    2010-06-01

    We propose an efficient method for evaluating the Coulomb force in the Gaussian and finite-element Coulomb (GFC) method, which is a linear-scaling approach for evaluating the Coulomb matrix and energy in large molecular systems. The efficient evaluation of the analytical gradient in the GFC is not straightforward as well as the evaluation of the energy because the SCF procedure with the Coulomb matrix does not give a variational solution for the Coulomb energy. Thus, an efficient approximate method is alternatively proposed, in which the Coulomb potential is expanded in the Gaussian and finite-element auxiliary functions as done in the GFC. To minimize the error in the gradient not just in the energy, the derived functions of the original auxiliary functions of the GFC are used additionally for the evaluation of the Coulomb gradient. In fact, the use of the derived functions significantly improves the accuracy of this approach. Although these additional auxiliary functions enlarge the size of the discretized Poisson equation and thereby increase the computational cost, it maintains the near linear scaling as the GFC and does not affects the overall efficiency of the GFC approach.

  13. A novel methodology using MODIS and CERES for assessing the daily radiative forcing of smoke aerosols in large scale over the Amazonia

    NASA Astrophysics Data System (ADS)

    Sena, E. T.; Artaxo, P.

    2014-12-01

    A new methodology was developed for obtaining daily retrievals of the direct radiative forcing of aerosols (24h-DARF) at the top of the atmosphere (TOA) using satellite remote sensing. For that, simultaneous CERES (Clouds and Earth's Radiant Energy System) shortwave flux at the top of the atmosphere (TOA) and MODIS (Moderate Resolution Spectroradiometer) aerosol optical depth (AOD) retrievals were used. This methodology is applied over a large region of Brazilian Amazonia. We focused our studies on the peak of the biomass burning season (August to September) from 2000 to 2009 to analyse the impact of forest smoke on the radiation balance. To assess the spatial distribution of the DARF, background scenes without biomass burning impacts, were defined as scenes with MODIS AOD < 0.1. The fluxes at the TOA retrieved by CERES for those clean conditions (Fcl) were estimated as a function of the illumination geometry (θ0) for each 0.5° × 0.5° grid cell. The instantaneous DARF was obtained as the difference between clean Fcl (θ0) and the polluted mean flux at the TOA measured by CERES in each cell (Fpol (θ0)). The radiative transfer code SBDART (Santa Barbara DISORT Radiative Transfer model) was used to expand instantaneous DARFs to 24 h averages. With this methodology it is possible to assess the DARF both at large scale and at high temporal resolution. This new methodology also showed to be more robust, because it considerably reduces statistical sources of uncertainties in the estimates of the DARF, when compared to previous assessments of the DARF using satellite remote sensing. The spatial distribution of the 24h-DARF shows that, for some cases, the mean 24h-DARF presents local values as high as -30 W m-2. The temporal variability of the 24h-DARF along the biomass burning season was also studied and showed large intraseasonal and interannual variability. In an attempt to validate the radiative forcing obtained in this work using CERES and MODIS, those results

  14. Evaluation of Ag nanoparticle coated air filter against aerosolized virus: Anti-viral efficiency with dust loading.

    PubMed

    Joe, Yun Haeng; Park, Dae Hoon; Hwang, Jungho

    2016-01-15

    In this study, the effect of dust loading on the anti-viral ability of an anti-viral air filter was investigated. Silver nanoparticles approximately 11 nm in diameter were synthesized via a spark discharge generation system and were used as anti-viral agents coated onto a medium air filter. The pressure drop, filtration efficiency, and anti-viral ability of the filter against aerosolized bacteriophage MS2 virus particles were tested with dust loading. The filtration efficiency and pressure drop increased with dust loading, while the anti-viral ability decreased. Theoretical analysis of anti-viral ability with dust loading was carried out using a mathematical model based on that presented by Joe et al. (J. Hazard. Mater.; 280: 356-363, 2014). Our model can be used to compare anti-viral abilities of various anti-viral agents, determine appropriate coating areal density of anti-viral agent on a filter, and predict the life cycle of an anti-viral filter. PMID:26434534

  15. Comparison of force, power, and striking efficiency for a Kung Fu strike performed by novice and experienced practitioners: preliminary analysis.

    PubMed

    Neto, Osmar Pinto; Magini, Marcio; Saba, Marcelo M F; Pacheco, Marcos Tadeu Tavares

    2008-02-01

    This paper presents a comparison of force, power, and efficiency values calculated from Kung Fu Yau-Man palm strikes, when performed by 7 experienced and 6 novice men. They performed 5 palm strikes to a freestanding basketball, recorded by high-speed camera at 1000 Hz. Nonparametric comparisons and correlations showed experienced practitioners presented larger values of mean muscle force, mean impact force, mean muscle power, mean impact power, and mean striking efficiency, as is noted in evidence obtained for other martial arts. Also, an interesting result was that for experienced Kung Fu practitioners, muscle power was linearly correlated with impact power (p = .98) but not for the novice practitioners (p = .46).

  16. Enhanced efficiency in the excitation of higher modes for atomic force microscopy and mechanical sensors operated in liquids

    SciTech Connect

    Penedo, M. Hormeño, S.; Fernández-Martínez, I.; Luna, M.; Briones, F.; Raman, A.

    2014-10-27

    Recent developments in dynamic Atomic Force Microscopy where several eigenmodes are simultaneously excited in liquid media are proving to be an excellent tool in biological studies. Despite its relevance, the search for a reliable, efficient, and strong cantilever excitation method is still in progress. Herein, we present a theoretical modeling and experimental results of different actuation methods compatible with the operation of Atomic Force Microscopy in liquid environments: ideal acoustic, homogeneously distributed force, distributed applied torque (MAC Mode™), photothermal and magnetostrictive excitation. From the analysis of the results, it can be concluded that magnetostriction is the strongest and most efficient technique for higher eigenmode excitation when using soft cantilevers in liquid media.

  17. Efficiency in Israel Defence Forces Dental Labs: assessing the need for privatizing publicly provided services.

    PubMed

    Levy, R; Cohen, M

    1996-01-01

    In the last 10 to 15 years, privatization has been used as a policy instrument to reduce the involvement of the public sector in the provision of a variety of services. The purpose of this paper is to discuss models of privatization in the dental technician market and to report on the findings of an analysis of the functioning and efficiency of such services within the framework of the Israel Defence Forces (IDF). We also develop a method for assessing the quality and efficiency with which such services are produced and assess the need for privatization of the service. Currently, the IDF employs a mixed model of privatization whereby some dental technician services are produced in-house and others are contracted out to the civilian private market. A comparative quantitative analysis of the efficiency, quality, and cost of services indicates that the civilian labs are able to produce prosthetic services at a lower cost per unit of output and at a higher level of quality than are the IDF labs. The highly competitive nature of the industry as well as the relative ease with which the IDF could monitor the quality of service further supports the case for privatization of the entire service. The analysis and method described in this paper can serve as a paradigm for evaluating dental technician services in a variety of settings. PMID:11082751

  18. Mass absorption efficiency of light absorbing organic aerosols from source region of paddy-residue burning emissions in the Indo-Gangetic Plain

    NASA Astrophysics Data System (ADS)

    Srinivas, B.; Rastogi, N.; Sarin, M. M.; Singh, A.; Singh, D.

    2016-01-01

    The mass absorption efficiency (MAE) of light absorbing water-soluble organics, representing a significant fraction of brown carbon (BrC), has been studied in fine mode aerosols (PM2.5) from a source region (Patiala: 30.2 °N, 76.3 °E) of biomass burning emissions (BBEs) in the Indo-Gangetic Plain (IGP). The mass absorption coefficient of BrC at 365 nm (babs-365), assessed from absorption spectra of aqueous extracts, exhibits significant linear relationship with water-soluble organic carbon (WSOC) for day (R2 = 0.37) and night time (R2 = 0.77) samples; and slope of regression lines provides a measure of MAE of BrC (daytime: ˜0.75 m2 g-1 and night time: 1.13 m2 g-1). A close similarity in the temporal variability of babs-365 (for BrC) and K+ in all samples suggests their common source from BBEs. The babs-365 of BrC follows a power law (babs-λ ≈ λ-α; where α = angstrom exponent) and averages around 5.2 ± 2.0 M m-1 (where M = 10-6). A significant decrease in the MAE of BrC from the source region (this study) to the downwind oceanic region (over Bay of Bengal, Srinivas and Sarin, 2013) could be attributed to relative increase in the contribution of non-absorbing WSOC and/or photo-bleaching of BrC during long-range atmospheric transport. The atmospheric radiative forcing due to BrC over the study site accounts for ˜40% of that from elemental carbon (EC).

  19. Evaluating Aerosol Process Modules within the Framework of the Aerosol Modeling Testbed

    NASA Astrophysics Data System (ADS)

    Fast, J. D.; Velu, V.; Gustafson, W. I.; Chapman, E.; Easter, R. C.; Shrivastava, M.; Singh, B.

    2012-12-01

    Factors that influence predictions of aerosol direct and indirect forcing, such as aerosol mass, composition, size distribution, hygroscopicity, and optical properties, still contain large uncertainties in both regional and global models. New aerosol treatments are usually implemented into a 3-D atmospheric model and evaluated using a limited number of measurements from a specific case study. Under this modeling paradigm, the performance and computational efficiency of several treatments for a specific aerosol process cannot be adequately quantified because many other processes among various modeling studies (e.g. grid configuration, meteorology, emission rates) are different as well. The scientific community needs to know the advantages and disadvantages of specific aerosol treatments when the meteorology, chemistry, and other aerosol processes are identical in order to reduce the uncertainties associated with aerosols predictions. To address these issues, an Aerosol Modeling Testbed (AMT) has been developed that systematically and objectively evaluates new aerosol treatments for use in regional and global models. The AMT consists of the modular Weather Research and Forecasting (WRF) model, a series testbed cases for which extensive in situ and remote sensing measurements of meteorological, trace gas, and aerosol properties are available, and a suite of tools to evaluate the performance of meteorological, chemical, aerosol process modules. WRF contains various parameterizations of meteorological, chemical, and aerosol processes and includes interactive aerosol-cloud-radiation treatments similar to those employed by climate models. In addition, the physics suite from the Community Atmosphere Model version 5 (CAM5) have also been ported to WRF so that they can be tested at various spatial scales and compared directly with field campaign data and other parameterizations commonly used by the mesoscale modeling community. Data from several campaigns, including the 2006

  20. Dust Aerosol Impact on North Africa Climate: A GCM Investigation of Aerosol-Cloud-Radiation Interactions Using A-Train Satellite Data

    SciTech Connect

    Gu, Y.; Liou, K. N.; Jiang, Jonathan; Su, Hui; Liu, Xiaohong

    2012-02-15

    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 indirect effect based on cloud and aerosol data retrieved from A-Train satellite observations have been employed in the climate model simulations. Offline simulations reveal that the direct solar, IR, and net forcings by dust aerosols 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 could exceed aerosol forcing. With the aerosol indirect effect, the net cloud forcing is generally reduced for 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 result 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 seems to be associated with enhanced ice water contents in this region. The 200 mb radiative heating rate shows more cooling with the aerosol indirect effect since greater cooling is

  1. Collection efficiency of the soot-particle aerosol mass spectrometer (SP-AMS) for internally mixed particulate black carbon

    NASA Astrophysics Data System (ADS)

    Willis, M. D.; Lee, A. K. Y.; Onasch, T. B.; Fortner, E. C.; Williams, L. R.; Lambe, A. T.; Worsnop, D. R.; Abbatt, J. P. D.

    2014-12-01

    The soot-particle aerosol mass spectrometer (SP-AMS) uses an intra-cavity infrared laser to vaporize refractory black carbon (rBC) containing particles, making the particle beam-laser beam overlap critical in determining the collection efficiency (CE) for rBC and associated non-refractory particulate matter (NR-PM). This work evaluates the ability of the SP-AMS to quantify rBC and NR-PM mass in internally mixed particles with different thicknesses of organic coating. Using apparent relative ionization efficiencies for uncoated and thickly coated rBC particles, we report measurements of SP-AMS sensitivity to NR-PM and rBC, for Regal Black, the recommended particulate calibration material. Beam width probe (BWP) measurements are used to illustrate an increase in sensitivity for highly coated particles due to narrowing of the particle beam, which enhances the CE of the SP-AMS by increasing the laser beam-particle beam overlap. Assuming complete overlap for thick coatings, we estimate CE for bare Regal Black particles of 0.6 ± 0.1, which suggests that previously measured SP-AMS sensitivities to Regal Black were underestimated by up to a factor of 2. The efficacy of the BWP measurements is highlighted by studies at a busy road in downtown Toronto and at a non-roadside location, which show particle beam widths similar to, but greater than that of bare Regal Black and coated Regal Black, respectively. Further BWP measurements at field locations will help to constrain the range of CE for fresh and aged rBC-containing particles. The ability of the SP-AMS to quantitatively assess the composition of internally mixed particles is validated through measurements of laboratory-generated organic coated particles, which demonstrate that the SP-AMS can quantify rBC and NR-PM over a wide range of particle compositions and rBC core sizes.

  2. A novel exposure system for the efficient and controlled deposition of aerosol particles onto cell cultures.

    PubMed

    Savi, Melanie; Kalberer, Markus; Lang, Doris; Ryser, Manuel; Fierz, Martin; Gaschen, Annina; Ricka, Jaroslav; Geiser, Marianne

    2008-08-01

    Epidemiologic studies have shown correlations between morbidity and particles < or = 2.5 microm generated from pollution processes and manufactured nanoparticles. Thereby nanoparticles seem to play a specific role. The interaction of particles with the lung, the main pathway of undesired particle uptake, is poorly understood. In most studies investigating these interactions in vitro, particle deposition differs greatly from the in vivo situation, causing controversial results. We present a nanoparticle deposition chamber to expose lung cells mimicking closely the particle deposition conditions in the lung. In this new deposition chamber, particles are deposited very efficiently, reproducibly, and uniformly onto the cell culture, a key aspect if cell responses are quantified in respect to the deposited particle number. In situ analyses of the lung cells, e.g., the ciliary beat frequency, indicative of the defense capability of the cells, are complemented by off-line biochemical, physiological, and morphological cell analyses.

  3. Fine Mode Aerosol over the United Arab Emirates

    NASA Astrophysics Data System (ADS)

    Ross, K. E.; Piketh, S. J.; Reid, J. S.; Reid, E. A.

    2005-12-01

    The aerosol loading of the atmosphere over the Arabian Gulf region is extremely diverse and is composed not only of dust, but also of pollution that is derived largely from oil-related activities. Fine mode pollution particles are most efficient at scattering incoming solar radiation and have the potential to act as cloud condensation nuclei (CCN), and may therefore have implications for climate change. The smaller aerosols may also pose a health hazard if present in high concentrations. The United Arab Emirates Unified Aerosol Experiment (UAE2) was designed to investigate aerosol and meteorological characteristics over the region using ground-based, aircraft and satellite measurements, and was conducted in August and September 2004. Aerosol chemical composition has been obtained from filters that were collected at the site of the Mobile Atmospheric Aerosol and Radiation Characterization Observatory (MAARCO) on the coast of the UAE between Abu Dhabi and Dubai. Filter samples were also collected on an airborne platform in order to assess how aerosol chemical composition varies across the region and throughout the depth of the boundary layer. Results of the analysis of the PM2.5 coastal samples show that ammonium sulphate is the most prevalent constituent of the fine mode aerosol in the region (>50% of the mass), followed by organic matter, alumino-silicates, calcium carbonate and black carbon. Source apportionment indicates that most of the fine aerosol mass is derived from fossil fuel combustion, while mineral dust and local vehicle emissions also contribute to the fine aerosol loading. The organic carbon-to-total carbon ratio of the aerosol is 0.65, which is typical of fossil fuel combustion. The dominance of sulphates means that the fine mode aerosol in the region is probably responsible for a negative radiative forcing, and that the polluting emissions significantly elevate the concentration of CCN.

  4. Analysis of driving efficiency for LRV wheels using forced-slip method

    NASA Astrophysics Data System (ADS)

    Liang, Zhongchao; Gao, Haibo; Ding, Liang; Deng, Zongquan; Qu, Jianjun

    2014-11-01

    To investigate and improve the mobility of the Lunar Roving Vehicle (LRV), it is necessary to consider the mechanical properties of the interaction between the wheels and the ground. In this paper, a new solution method, the forced-slip solution method, which uses a semi-empirical approach, was presented. That is, given the wheel's vertical load and drawbar pull or driving torque as known input values, the unknown slip ratio can be resolved. The alternative method involves predicting the mechanics for a given slip ratio. The proposed method correlates better with actual wheel movements, and by studying a single wheel, this solution method can also be used to resolve the mechanical properties of the front and rear wheels in a four-wheel-drive (4WD) LRV configuration. It can also be used to consider the multi-pass effect of the rear wheels on lunar soil. The calculation results show that the 4WD LRV driving efficiency varies with the position of the center of mass. Thus, the LRV driving efficiency can be optimized by adjusting the position of its center of mass.

  5. Effects of divided doses of a bronchodilator aerosol and the intervening time interval on the forced expiration.

    PubMed

    Hidinger, K G; Bake, B

    1986-01-01

    Twelve patients with bronchial asthma participated in a blind, randomized, crossover study comparing the effects of 500 micrograms terbutaline in one inhalation, 125 micrograms in four inhalations taken in rapid succession, and 125 micrograms in four inhalations taken with an intervening time interval of 30 min. There were no significant differences between the three modes of inhalation of 500 micrograms terbutaline in any of the spirometric variables, i.e., 1-second forced expiratory volume, forced vital capacity, and maximal airflows when 50 and 75% of the forced vital capacity was exhaled from the total lung capacity. However, there were neither any significant differences between the levels of bronchodilation reached after administration of 500 micrograms and 2 or 3 X 125 micrograms terbutaline with an intervening time interval of 30 min. The time interval between the divided doses was possibly too long to achieve maximum accumulated effect of the four divided doses.

  6. Easy Volcanic Aerosol

    NASA Astrophysics Data System (ADS)

    Toohey, Matthew; Stevens, Bjorn; Schmidt, Hauke; Timmreck, Claudia

    2016-04-01

    Radiative forcing by stratospheric sulfate aerosol of volcanic origin is one of the strongest drivers of natural climate variability. Transient model simulations attempting to match observed climate variability, such as the CMIP historical simulations, rely on volcanic forcing reconstructions based on observations of a small sample of recent eruptions and coarse proxy data for eruptions before the satellite era. Volcanic forcing data sets used in CMIP5 were provided either in terms of optical properties, or in terms of sulfate aerosol mass, leading to significant inter-model spread in the actual volcanic radiative forcing produced by models and in their resulting climate responses. It remains therefore unclear to what degree inter-model spread in response to volcanic forcing represents model differences or variations in the forcing. In order to isolate model differences, Easy Volcanic Aerosol (EVA) provides an analytic representation of volcanic stratospheric aerosol forcing, based on available observations and aerosol model results, prescribing the aerosol's radiative properties and primary modes of spatial and temporal variability. In contrast to regriddings of observational data, EVA allows for the production of physically consistent forcing for historic and hypothetical eruptions of varying magnitude, source latitude, and season. Within CMIP6, EVA will be used to reconstruct volcanic forcing over the past 2000 years for use in the Paleo-Modeling Intercomparison Project (PMIP), and will provide forcing sets for VolMIP experiments aiming to quantify model uncertainty in the response to volcanic forcing. Here, the functional form of EVA will be introduced, along with illustrative examples including the EVA-based reconstruction of volcanic forcing over the historical period, and that of the 1815 Tambora eruption.

  7. Building America Case Study: Apartment Compartmentalization with an Aerosol-Based Sealing Process - Queens, NY; Technology Solutions for New and Existing Homes, Energy Efficiency & Renewable Energy (EERE)

    SciTech Connect

    2015-07-01

    Air sealing of building enclosures is a difficult and time-consuming process. Current methods in new construction require laborers to physically locate small and sometimes large holes in multiple assemblies and then manually seal each of them. The innovation demonstrated under this research study was the automated air sealing and compartmentalization of buildings through the use of an aerosolized sealant, developed by the Western Cooling Efficiency Center at University of California Davis.
    CARB sought to demonstrate this new technology application in a multifamily building in Queens, NY. The effectiveness of the sealing process was evaluated by three methods: air leakage testing of overall apartment before and after sealing, point-source testing of individual leaks, and pressure measurements in the walls of the target apartment during sealing. Aerosolized sealing was successful by several measures in this study. Many individual leaks that are labor-intensive to address separately were well sealed by the aerosol particles. In addition, many diffuse leaks that are difficult to identify and treat were also sealed. The aerosol-based sealing process resulted in an average reduction of 71% in air leakage across three apartments and an average apartment airtightness of 0.08 CFM50/SF of enclosure area.

  8. The importance of aerosol water for air pollution effects on weather and climate

    NASA Astrophysics Data System (ADS)

    Metzger, S.; Lelieveld, J.

    2007-12-01

    We apply a new concept to study air pollution effects on weather and climate, which is based on thermodynamic principles that explain hydration and osmosis - including the required transformation of laboratory based concepts to atmospheric conditions. Under ambient conditions the equilibrium relative humidity (ERH) determines the saturation molality, solute and solvent activities (and activity coefficients), and the aerosol associated water mass, sine the water content is fixed by ERH for a given aerosol concentration and type. As a consequence, aerosol water drives the gas/liquid/solid aerosol partitioning, ambient aerosol size-distributions and directly links aerosol hygroscopic growth into fog, haze and clouds. Various modeling results indicate that a) our new concept is not limited to dilute binary solutions, b) sensitive aerosol properties such as the pH of binary and mixed inorganic/organic salt solutions up to saturation can be computed accurately, and c) that anthropogenic emissions can be directly linked to visibility reduction, cloud formation and climate forcing, if we explicitly account for the aerosol water mass. Our new concept is more explicit than the traditional CCN concept as it abandons the use of ambiguous terms such as "marine" and "continental" aerosols, and refines lumped categories such as mineral dust, biomass burning, sea salt, organic or sulfate aerosols currently used in atmospheric modeling. Despite, our concept is computationally very efficient as it allows solving the whole gas/liquid/solid aerosol partitioning analytically without numerical iterations. It is therefore especially suited for regional high resolution, or global climate applications.

  9. Aerosol indirect effect on tropospheric ozone via lightning

    NASA Astrophysics Data System (ADS)

    Yuan, Tianle; Remer, Lorraine A.; Bian, Huisheng; Ziemke, Jerald R.; Albrecht, Rachel; Pickering, Kenneth E.; Oreopoulos, Lazaros; Goodman, Steven J.; Yu, Hongbin; Allen, Dale J.

    2012-09-01

    Tropospheric ozone (O3) is a pollutant and major greenhouse gas and its radiative forcing is still uncertain. Inadequate understanding of processes related to O3 production, in particular those natural ones such as lightning, contributes to this uncertainty. Here we demonstrate a new effect of aerosol particles on O3production by affecting lightning activity and lightning-generated NOx (LNOx). We find that lightning flash rate increases at a remarkable rate of 30 times or more per unit of aerosol optical depth. We provide observational evidence that indicates the observed increase in lightning activity is caused by the influx of aerosols from a volcano. Satellite data analyses show O3is increased as a result of aerosol-induced increase in lightning and LNOx, which is supported by modle simulations with prescribed lightning change. O3production increase from this aerosol-lightning-ozone link is concentrated in the upper troposphere, where O3 is most efficient as a greenhouse gas. In the face of anthropogenic aerosol increase our findings suggest that lightning activity, LNOx and O3, especially in the upper troposphere, have all increased substantially since preindustrial time due to the proposed aerosol-lightning-ozone link, which implies a stronger O3 historical radiative forcing. Aerosol forcing therefore has a warming component via its effect on O3 production and this component has mostly been ignored in previous studies of climate forcing related to O3and aerosols. Sensitivity simulations suggest that 4-8% increase of column tropospheric ozone, mainly in the tropics, is expected if aerosol-lighting-ozone link is parameterized, depending on the background emission scenario. We note, however, substantial uncertainties remain on the exact magnitude of aerosol effect on tropospheric O3 via lightning. The challenges for obtaining a quantitative global estimate of this effect are also discussed. Our results have significant implications for understanding past and

  10. Direct Radiative Effect and Heating Rate of black carbon aerosol: high time resolution measurements and source-identified forcing effects

    NASA Astrophysics Data System (ADS)

    Ferrero, Luca; Mocnik, Grisa; Cogliati, Sergio; Comi, Alberto; Degni, Francesca; Di Mauro, Biagio; Colombo, Roberto; Bolzacchini, Ezio

    2016-04-01

    Black carbon (BC) absorbs sunlight in the atmosphere heating it. However, up to now, heating rate (HR) calculations from the divergence of the net radiative flux with altitude or from the modelling activity are too sparse. This work fills the aforementioned gap presenting a new methodology based on a full set of physical equations to experimentally determine both the radiative power density absorbed into a ground-based atmospheric layer (ADRE), and the consequent HR induced by the absorptive component of aerosol. In urban context, it is essentially related to the BC. The methodology is also applicable to natural components (i.e. dust) and is obtained solving the first derivative of the main radiative transfer equations. The ADRE and the consequent HR can be determined coupling spectral aerosol absorption measurements with the spectrally resolved measurements of the direct, diffuse downward radiation and the surface reflected radiance components. Moreover, the spectral absorption of BC aerosol allows its source apportionment (traffic and biomass burning (BB)) allowing the same apportionment on HR. This work reports one year of high-time resolution measurements (5 min) of sunlight absorption and HR induced by BC aerosol over Milan. A unique sampling site was set up from March 2015 with: 1) Aethalometer (AE-31, Magee Scientific, 7-λ), 2) the Multiplexer-Radiometer-Irradiometer which detects downward and reflected radiance (350-1000 nm in 3648 spectral bands) coupled with a rotating shadow-band to measure spectrally-resolved global and diffuse radiation (thus direct), 3) a meteorological station (LSI-Lastem) equipped with 3 pyranometers (global, diffuse and refrected radiation; 300-3000 nm), a thermohygrometer, a barometer, an anemometer, 4) condensation and optical particle counters (TSI 3775 and Grimm 1.107), 5) low volume sampler (FAI Hydra dual sampler, PM2.5 and PM10) for sample collection and chemistry determination. Results concerning the radiative power

  11. Improved aerosol radiative properties as a foundation for solar geoengineering risk assessment

    NASA Astrophysics Data System (ADS)

    Dykema, J. A.; Keith, D. W.; Keutsch, F. N.

    2016-07-01

    Side effects resulting from the deliberate injection of sulfate aerosols intended to partially offset climate change have motivated the investigation of alternatives, including solid aerosol materials. Sulfate aerosols warm the tropical tropopause layer, increasing the flux of water vapor into the stratosphere, accelerating ozone loss, and increasing radiative forcing. The high refractive index of some solid materials may lead to reduction in these risks. We present a new analysis of the scattering efficiency and absorption of a range of candidate solid aerosols. We utilize a comprehensive radiative transfer model driven by updated, physically consistent estimates of optical properties. We compute the potential increase in stratospheric water vapor and associated longwave radiative forcing. We find that the stratospheric heating calculated in this analysis indicates some materials to be substantially riskier than previous work. We also find that there are Earth-abundant materials that may reduce some principal known risks relative to sulfate aerosols.

  12. Aqueous aerosol SOA formation: impact on aerosol physical properties.

    PubMed

    Woo, Joseph L; Kim, Derek D; Schwier, Allison N; Li, Ruizhi; McNeill, V Faye

    2013-01-01

    Organic chemistry in aerosol water has recently been recognized as a potentially important source of secondary organic aerosol (SOA) material. This SOA material may be surface-active, therefore potentially affecting aerosol heterogeneous activity, ice nucleation, and CCN activity. Aqueous aerosol chemistry has also been shown to be a potential source of light-absorbing products ("brown carbon"). We present results on the formation of secondary organic aerosol material in aerosol water and the associated changes in aerosol physical properties from GAMMA (Gas-Aerosol Model for Mechanism Analysis), a photochemical box model with coupled gas and detailed aqueous aerosol chemistry. The detailed aerosol composition output from GAMMA was coupled with two recently developed modules for predicting a) aerosol surface tension and b) the UV-Vis absorption spectrum of the aerosol, based on our previous laboratory observations. The simulation results suggest that the formation of oligomers and organic acids in bulk aerosol water is unlikely to perturb aerosol surface tension significantly. Isoprene-derived organosulfates are formed in high concentrations in acidic aerosols under low-NO(x) conditions, but more experimental data are needed before the potential impact of these species on aerosol surface tension may be evaluated. Adsorption of surfactants from the gas phase may further suppress aerosol surface tension. Light absorption by aqueous aerosol SOA material is driven by dark glyoxal chemistry and is highest under high-NO(x) conditions, at high relative humidity, in the early morning hours. The wavelength dependence of the predicted absorption spectra is comparable to field observations and the predicted mass absorption efficiencies suggest that aqueous aerosol chemistry can be a significant source of aerosol brown carbon under urban conditions. PMID:24601011

  13. Collection efficiency of the Soot-Particle Aerosol Mass Spectrometer (SP-AMS) for internally mixed particulate black carbon

    DOE PAGES

    Willis, M. D.; Lee, A. K. Y.; Onasch, T. B.; Fortner, E. C.; Williams, L. R.; Lambe, A. T.; Worsnop, D. R.; Abbatt, J. P. D.

    2014-05-26

    The soot-particle aerosol mass spectrometer (SP-AMS) uses an intra-cavity infrared laser to vaporize refractory black carbon (rBC) containing particles, making the particle beam–laser beam overlap critical in determining the collection efficiency (CE) for rBC and associated non-refractory particulate matter (NR-PM). This work evaluates the ability of the SP-AMS to quantify rBC and NR-PM mass in internally mixed particles with different thicknesses of organic coating. Using apparent relative ionization efficiencies for uncoated and thickly coated rBC particles, we report measurements of SP-AMS sensitivity to NR-PM and rBC, for Regal Black, the recommended particulate calibration material. Beam width probe (BWP) measurements aremore » used to illustrate an increase in sensitivity for highly coated particles due to narrowing of the particle beam, which enhances the CE of the SP-AMS by increasing the laser beam–particle beam overlap. Assuming complete overlap for thick coatings, we estimate CE for bare Regal Black particles of 0.6 ± 0.1, which suggests that previously measured SP-AMS sensitivities to Regal Black were underestimated by up to a factor of two. The efficacy of the BWP measurements is highlighted by studies at a busy road in downtown Toronto and at a non-roadside location, which show particle beam widths similar to, but greater than that of bare Regal Black and coated Regal Black, respectively. Further BWP measurements at field locations will help to constrain the range of CE for fresh and aged rBC-containing particles. The ability of the SP-AMS to quantitatively assess the composition of internally mixed particles is validated through measurements of laboratory-generated organic coated particles, which demonstrate that the SP-AMS can quantify rBC and NR-PM over a wide range of particle compositions and rBC core sizes.« less

  14. Collection efficiency of the soot-particle aerosol mass spectrometer (SP-AMS) for internally mixed particulate black carbon

    DOE PAGES

    Willis, M. D.; Lee, A. K. Y.; Onasch, T. B.; Fortner, E. C.; Williams, L. R.; Lambe, A. T.; Worsnop, D. R.; Abbatt, J. P. D.

    2014-12-18

    The soot-particle aerosol mass spectrometer (SP-AMS) uses an intra-cavity infrared laser to vaporize refractory black carbon (rBC) containing particles, making the particle beam–laser beam overlap critical in determining the collection efficiency (CE) for rBC and associated non-refractory particulate matter (NR-PM). This work evaluates the ability of the SP-AMS to quantify rBC and NR-PM mass in internally mixed particles with different thicknesses of organic coating. Using apparent relative ionization efficiencies for uncoated and thickly coated rBC particles, we report measurements of SP-AMS sensitivity to NR-PM and rBC, for Regal Black, the recommended particulate calibration material. Beam width probe (BWP) measurements aremore » used to illustrate an increase in sensitivity for highly coated particles due to narrowing of the particle beam, which enhances the CE of the SP-AMS by increasing the laser beam–particle beam overlap. Assuming complete overlap for thick coatings, we estimate CE for bare Regal Black particles of 0.6 ± 0.1, which suggests that previously measured SP-AMS sensitivities to Regal Black were underestimated by up to a factor of 2. The efficacy of the BWP measurements is highlighted by studies at a busy road in downtown Toronto and at a non-roadside location, which show particle beam widths similar to, but greater than that of bare Regal Black and coated Regal Black, respectively. Further BWP measurements at field locations will help to constrain the range of CE for fresh and aged rBC-containing particles. The ability of the SP-AMS to quantitatively assess the composition of internally mixed particles is validated through measurements of laboratory-generated organic coated particles, which demonstrate that the SP-AMS can quantify rBC and NR-PM over a wide range of particle compositions and rBC core sizes.« less

  15. LightForce Photon-Pressure Collision Avoidance: Updated Efficiency Analysis Utilizing a Highly Parallel Simulation Approach

    NASA Astrophysics Data System (ADS)

    Stupl, J.; Faber, N.; Foster, C.; Yang, F.; Nelson, B.; Aziz, J.; Nuttall, A.; Henze, C.; Levit, C.

    2014-09-01

    This paper provides an updated efficiency analysis of the LightForce space debris collision avoidance scheme. LightForce aims to prevent collisions on warning by utilizing photon pressure from ground based, commercial off the shelf lasers. Past research has proven that a few ground-based systems consisting of 10 kW class lasers directed by 1.5 m telescopes with adaptive optics could lower the expected number of collisions in Low Earth Orbit (LEO) by an order of magnitude. Our simulation approach utilizes the entire Two Line Element (TLE) catalogue in LEO for a given day as initial input. Least-squares fitting of a TLE time series is used for an improved orbit estimate. We then calculate the probability of collision for all LEO objects in the catalogue for a time step of the simulation. The conjunctions that exceed a threshold probability of collision are then engaged by a simulated network of laser ground stations. After those engagements, the perturbed orbits are used to re-assess the probability of collision and evaluate the efficiency. This paper describes new simulations with three updated aspects: 1) By utilizing a highly parallel simulation approach employing hundreds of processors, we have extended our analysis to a much broader dataset. The simulation time is extended to one year. 2) We analyze not only the efficiency of LightForce on conjunctions that naturally occur, but also take into account conjunctions caused by orbit perturbations due to LightForce engagements. 3) We use a new simulation approach that is regularly updating the LightForce engagement strategy, as it would be during actual operations. In this paper we present both our simulation approach to parallelize the efficiency analysis, its computational performance and the resulting expected efficiency of the LightForce collision avoidance system.

  16. In situ fabrication of depth-type hierarchical CNT/quartz fiber filters for high efficiency filtration of sub-micron aerosols and high water repellency

    NASA Astrophysics Data System (ADS)

    Li, Peng; Zong, Yichen; Zhang, Yingying; Yang, Mengmeng; Zhang, Rufan; Li, Shuiqing; Wei, Fei

    2013-03-01

    We fabricated depth-type hierarchical CNT/quartz fiber (QF) filters through in situ growth of CNTs upon quartz fiber (QF) filters using a floating catalyst chemical vapor deposition (CVD) method. The filter specific area of the CNT/QF filters is more than 12 times higher than that of the pristine QF filters. As a result, the penetration of sub-micron aerosols for CNT/QF filters is reduced by two orders of magnitude, which reaches the standard of high-efficiency particulate air (HEPA) filters. Simultaneously, due to the fluffy brush-like hierarchical structure of CNTs on QFs, the pore size of the hybrid filters only has a small increment. The pressure drop across the CNT/QF filters only increases about 50% with respect to that of the pristine QF filters, leading to an obvious increased quality factor of the CNT/QF filters. Scanning electron microscope images reveal that CNTs are very efficient in capturing sub-micron aerosols. Moreover, the CNT/QF filters show high water repellency, implying their superiority for applications in humid conditions.We fabricated depth-type hierarchical CNT/quartz fiber (QF) filters through in situ growth of CNTs upon quartz fiber (QF) filters using a floating catalyst chemical vapor deposition (CVD) method. The filter specific area of the CNT/QF filters is more than 12 times higher than that of the pristine QF filters. As a result, the penetration of sub-micron aerosols for CNT/QF filters is reduced by two orders of magnitude, which reaches the standard of high-efficiency particulate air (HEPA) filters. Simultaneously, due to the fluffy brush-like hierarchical structure of CNTs on QFs, the pore size of the hybrid filters only has a small increment. The pressure drop across the CNT/QF filters only increases about 50% with respect to that of the pristine QF filters, leading to an obvious increased quality factor of the CNT/QF filters. Scanning electron microscope images reveal that CNTs are very efficient in capturing sub-micron aerosols

  17. What does nature tell us about aerosol effects in a trade cumulus regime?

    NASA Astrophysics Data System (ADS)

    Yuan, T.; Remer, L. A.; Yu, H.; Wang, H.

    2011-12-01

    Detecting aerosol effect on cloud amount has been elusive to both observations and modeling due to potential buffering mechanisms and convolution of meteorology. Here through a natural experiment provided by long-term degassing of a low-lying volcano and use of A-Train satellite observations, we show modifications of trade cumulus cloud fields including decreased droplet size, decreased precipitation efficiency and increased cloud amount are associated with volcanic aerosols. In addition we find significantly higher cloud tops for polluted clouds. We demonstrate that the observed microphysical and macrophysical changes cannot be explained by synoptic meteorology or the orographic effect of the Hawaiian Islands. Idealized large eddy simulations reproduce some key observed features of the cloud response to aerosol perturbations, which helps us further understand the underlying mechanisms. The "total shortwave aerosol forcing", resulting from direct and indirect forcings including both cloud albedo and cloud amount, is almost an order of magnitude higher than aerosol direct forcing alone. Furthermore, the precipitation reduction associated with enhanced aerosol leads to large changes in the energetics of air-sea exchange and trade wind boundary layer. Our results represent the first observational evidence of large-scale increase of cloud amount due to aerosols in a trade cumulus regime, which can be used to constrain the representation of aerosol-cloud interactions in climate models. The findings also have implications for volcano-climate interactions and climate mitigation research.

  18. Aerosol indirect effect on tropospheric ozone via lightning

    NASA Astrophysics Data System (ADS)

    Yuan, T.; Remer, L. A.; Bian, H.; Ziemke, J. R.; Albrecht, R. I.; Pickering, K. E.; Oreopoulos, L.; Goodman, S. J.; Yu, H.; Allen, D. J.

    2012-12-01

    Tropospheric ozone (O3) is a pollutant and major greenhouse gas and its radiative forcing is still uncertain. The unresolved difference between modeled and observed natural background O3 concentrations is a key source of the uncertainty. Here we demonstrate remarkable sensitivity of lightning activity to aerosol loading with lightning activity increasing more than 30 times per unit of aerosol optical depth over our study area. We provide observational evidence that indicates the observed increase in lightning activity is caused by the influx of aerosols from a volcano. Satellite data analyses suggest O3 is increased as a result of aerosol-induced increase in lightning and lightning produced NOx. Model simulations with prescribed lightning change corroborate the satellite data analysis. This aerosol-O3 connection is achieved via aerosol increasing lightning and thus lightning produced nitrogen oxides. This aerosol-lightning-ozone link provides a potential physical mechanism that may account for a part of the model-observation difference in background O3 concentration. More importantly, O3 production increase from this link is concentrated in the upper troposphere, where O3 is most efficient as a greenhouse gas. Both of these implications suggest a stronger O3 historical radiative forcing. This introduces a new pathway, through which increasing in aerosols from pre-industrial time to present day enhances tropospheric O3 production. Aerosol forcing thus has a warming component via its effect on O3 production. Sensitivity simulations suggest that 4-8% increase of tropospheric ozone, mainly in the tropics, is expected if aerosol-lighting-ozone link is parameterized, depending on the background emission scenario. We note, however, substantial uncertainties remain on the exact magnitude of aerosol effect on tropospheric O3 via lightning. The challenges for obtaining a quantitative global estimate of this effect are also discussed. Our results have significant implications

  19. Irrelevance of the Power Stroke for the Directionality, Stopping Force, and Optimal Efficiency of Chemically Driven Molecular Machines

    PubMed Central

    Astumian, R. Dean

    2015-01-01

    A simple model for a chemically driven molecular walker shows that the elastic energy stored by the molecule and released during the conformational change known as the power-stroke (i.e., the free-energy difference between the pre- and post-power-stroke states) is irrelevant for determining the directionality, stopping force, and efficiency of the motor. Further, the apportionment of the dependence on the externally applied force between the forward and reverse rate constants of the power-stroke (or indeed among all rate constants) is irrelevant for determining the directionality, stopping force, and efficiency of the motor. Arguments based on the principle of microscopic reversibility demonstrate that this result is general for all chemically driven molecular machines, and even more broadly that the relative energies of the states of the motor have no role in determining the directionality, stopping force, or optimal efficiency of the machine. Instead, the directionality, stopping force, and optimal efficiency are determined solely by the relative heights of the energy barriers between the states. Molecular recognition—the ability of a molecular machine to discriminate between substrate and product depending on the state of the machine—is far more important for determining the intrinsic directionality and thermodynamics of chemo-mechanical coupling than are the details of the internal mechanical conformational motions of the machine. In contrast to the conclusions for chemical driving, a power-stroke is very important for the directionality and efficiency of light-driven molecular machines and for molecular machines driven by external modulation of thermodynamic parameters. PMID:25606678

  20. Irrelevance of the power stroke for the directionality, stopping force, and optimal efficiency of chemically driven molecular machines.

    PubMed

    Astumian, R Dean

    2015-01-20

    A simple model for a chemically driven molecular walker shows that the elastic energy stored by the molecule and released during the conformational change known as the power-stroke (i.e., the free-energy difference between the pre- and post-power-stroke states) is irrelevant for determining the directionality, stopping force, and efficiency of the motor. Further, the apportionment of the dependence on the externally applied force between the forward and reverse rate constants of the power-stroke (or indeed among all rate constants) is irrelevant for determining the directionality, stopping force, and efficiency of the motor. Arguments based on the principle of microscopic reversibility demonstrate that this result is general for all chemically driven molecular machines, and even more broadly that the relative energies of the states of the motor have no role in determining the directionality, stopping force, or optimal efficiency of the machine. Instead, the directionality, stopping force, and optimal efficiency are determined solely by the relative heights of the energy barriers between the states. Molecular recognition--the ability of a molecular machine to discriminate between substrate and product depending on the state of the machine--is far more important for determining the intrinsic directionality and thermodynamics of chemo-mechanical coupling than are the details of the internal mechanical conformational motions of the machine. In contrast to the conclusions for chemical driving, a power-stroke is very important for the directionality and efficiency of light-driven molecular machines and for molecular machines driven by external modulation of thermodynamic parameters.

  1. Use of the NASA GEOS-5 SEAC4RS Meteorological and Aerosol Reanalysis for assessing simulated aerosol optical properties as a function of smoke age

    NASA Astrophysics Data System (ADS)

    Randles, C. A.; da Silva, A. M., Jr.; Colarco, P. R.; Darmenov, A.; Buchard, V.; Govindaraju, R.; Chen, G.; Hair, J. W.; Russell, P. B.; Shinozuka, Y.; Wagner, N.; Lack, D.

    2014-12-01

    The NASA Goddard Earth Observing System version 5 (GEOS-5) Earth system model, which includes an online aerosol module, provided chemical and weather forecasts during the SEAC4RS field campaign. For post-mission analysis, we have produced a high resolution (25 km) meteorological and aerosol reanalysis for the entire campaign period. In addition to the full meteorological observing system used for routine NWP, we assimilate 550 nm aerosol optical depth (AOD) derived from MODIS (both Aqua and Terra satellites), ground-based AERONET sun photometers, and the MISR instrument (over bright surfaces only). Daily biomass burning emissions of CO, CO2, SO2, and aerosols are derived from MODIS fire radiative power retrievals. We have also introduced novel smoke "age" tracers, which provide, for a given time, a snapshot histogram of the age of simulated smoke aerosol. Because GEOS-5 assimilates remotely sensed AOD data, it generally reproduces observed (column) AOD compared to, for example, the airborne 4-STAR instrument. Constraining AOD, however, does not imply a good representation of either the vertical profile or the aerosol microphysical properties (e.g., composition, absorption). We do find a reasonable vertical structure for aerosols is attained in the model, provided actual smoke injection heights are not much above the planetary boundary layer, as verified with observations from DIAL/HRSL aboard the DC8. The translation of the simulated aerosol microphysical properties to total column AOD, needed in the aerosol assimilation step, is based on prescribed mass extinction efficiencies that depend on wavelength, composition, and relative humidity. Here we also evaluate the performance of the simulated aerosol speciation by examining in situ retrievals of aerosol absorption/single scattering albedo and scattering growth factor (f(RH)) from the LARGE and AOP suite of instruments. Putting these comparisons in the context of smoke age as diagnosed by the model helps us to

  2. Child Protection, Public Services and the Chimera of Market Force Efficiency.

    ERIC Educational Resources Information Center

    Barker, Richard W.

    1996-01-01

    Describes child protection systems in England and ongoing changes in their services. Considers effects of a market force approach on the organization of child protection services in relation to coordination versus fragmentation and profit versus professionalism. Concludes that the idea that a market force approach to child protection will lead to…

  3. A COMPUTATIONALLY EFFICIENT HYBRID APPROACH FOR DYNAMIC GAS/AEROSOL TRANSFER IN AIR QUALITY MODELS. (R826371C005)

    EPA Science Inventory

    Dynamic mass transfer methods have been developed to better describe the interaction of the aerosol population with semi-volatile species such as nitrate, ammonia, and chloride. Unfortunately, these dynamic methods are computationally expensive. Assumptions are often made to r...

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

    EPA Science Inventory

    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. LightForce Photon-Pressure Collision Avoidance: Updated Efficiency Analysis Utilizing a Highly Parallel Simulation Approach

    NASA Technical Reports Server (NTRS)

    Stupl, Jan; Faber, Nicolas; Foster, Cyrus; Yang, Fan Yang; Nelson, Bron; Aziz, Jonathan; Nuttall, Andrew; Henze, Chris; Levit, Creon

    2014-01-01

    This paper provides an updated efficiency analysis of the LightForce space debris collision avoidance scheme. LightForce aims to prevent collisions on warning by utilizing photon pressure from ground based, commercial off the shelf lasers. Past research has shown that a few ground-based systems consisting of 10 kilowatt class lasers directed by 1.5 meter telescopes with adaptive optics could lower the expected number of collisions in Low Earth Orbit (LEO) by an order of magnitude. Our simulation approach utilizes the entire Two Line Element (TLE) catalogue in LEO for a given day as initial input. Least-squares fitting of a TLE time series is used for an improved orbit estimate. We then calculate the probability of collision for all LEO objects in the catalogue for a time step of the simulation. The conjunctions that exceed a threshold probability of collision are then engaged by a simulated network of laser ground stations. After those engagements, the perturbed orbits are used to re-assess the probability of collision and evaluate the efficiency of the system. This paper describes new simulations with three updated aspects: 1) By utilizing a highly parallel simulation approach employing hundreds of processors, we have extended our analysis to a much broader dataset. The simulation time is extended to one year. 2) We analyze not only the efficiency of LightForce on conjunctions that naturally occur, but also take into account conjunctions caused by orbit perturbations due to LightForce engagements. 3) We use a new simulation approach that is regularly updating the LightForce engagement strategy, as it would be during actual operations. In this paper we present our simulation approach to parallelize the efficiency analysis, its computational performance and the resulting expected efficiency of the LightForce collision avoidance system. Results indicate that utilizing a network of four LightForce stations with 20 kilowatt lasers, 85% of all conjunctions with a

  6. Impact of aerosol direct radiative forcing on the radiative budget, surface heat fluxes, and atmospheric dynamics during the heat wave of summer 2003 over western Europe: A modeling study

    NASA Astrophysics Data System (ADS)

    PéRé, J. C.; Mallet, M.; Pont, V.; Bessagnet, B.

    2011-12-01

    In this work, an off-line coupling between the chemistry-transport model CHIMERE (associated with an aerosol optical module) and the meteorological model Weather Research and Forecasting (WRF) is used to study (1) the direct radiative forcing of pollution aerosols during the heat wave of summer 2003 over western Europe and (2) the possible feedbacks of this direct radiative forcing on the surface-atmosphere system. Simulations performed for the period 7-15 August 2003 reveal a significant decrease of daily mean solar radiation reaching the surface (ΔFBOA = -(10-30) W/m2) because of back scattering at the top of the atmosphere (ΔFTOA = -(1-12) W/m2) and also absorption of solar radiation by polluted particles (ΔFatm = + (5-23) W/m2). During daytime, the aerosol surface dimming induces a mean reduction of both sensible (16 W/m2) and latent (21 W/m2) heat fluxes emitted by the terrestrial surface, resulting in a radiative cooling of the air near the surface (up to 2.9 K/d at noon). Simultaneously, the absorption of solar energy by aerosols causes an atmospheric radiative heating within the planetary boundary layer reaching 1.20 K/d at noon. As a consequence, the direct radiative effect of aerosols is shown to reduce both the planetary boundary layer height (up to 30%) and the horizontal wind speed (up to 6%); that may have contributed to favor the particulate pollution during the heat wave of summer 2003.

  7. The effects of solution chemistry on the sticking efficiencies of viable Enterococcus faecalis: An atomic force microscopy and modeling study

    NASA Astrophysics Data System (ADS)

    Cail, Tracy L.; Hochella, Michael F.

    2005-06-01

    Atomic force microscopy (AFM) and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory in combination with the interaction force boundary layer (IFBL) model have been used to empirically and theoretically calculate sticking efficiencies (α) of Enterococcus faecalis cells against a silica glass surface. Sticking efficiencies were calculated in solutions of varying pH and ionic strength and related to maximum distances of transport through a hypothetical soil block using colloid filtration theory. AFM measurements show that the repulsive and attractive forces between E. faecalis cells and a glass surface are a function of ionic strength but are less sensitive to changes in solution pH. Zeta (ζ)-potential measurements of the cells and glass surfaces correlate with these trends. Calculated DLVO energy profiles predict much greater sensitivity to changing solution chemistry. Sticking efficiencies derived from AFM measurements range from 9.6 × 10 -17 to 1 in solutions of low ionic strength (IS) and from 2.6 × 10 -33 to 1 at higher IS. Corresponding α values determined from DLVO theory are essentially zero in all tested solutions. Sticking efficiencies calculated in this study are smaller than values determined from column and field studies in similar systems; however, α derived from AFM data and the IFBL model more closely represent field data than do values calculated from DLVO energy values. A comparison with different methods of calculating α suggests that reversible adhesion may be significant in column-scale transport studies.

  8. Optical extinction of highly porous aerosol following atmospheric freeze drying

    NASA Astrophysics Data System (ADS)

    Adler, Gabriela; Haspel, Carynelisa; Moise, Tamar; Rudich, Yinon

    2014-06-01

    Porous glassy particles are a potentially significant but unexplored component of atmospheric aerosol that can form by aerosol processing through the ice phase of high convective clouds. The optical properties of porous glassy aerosols formed from a freeze-dry cycle simulating freezing and sublimation of ice particles were measured using a cavity ring down aerosol spectrometer (CRD-AS) at 532 nm and 355 nm wavelength. The measured extinction efficiency was significantly reduced for porous organic and mixed organic-ammonium sulfate particles as compared to the extinction efficiency of the homogeneous aerosol of the same composition prior to the freeze-drying process. A number of theoretical approaches for modeling the optical extinction of porous aerosols were explored. These include effective medium approximations, extended effective medium approximations, multilayer concentric sphere models, Rayleigh-Debye-Gans theory, and the discrete dipole approximation. Though such approaches are commonly used to describe porous particles in astrophysical and atmospheric contexts, in the current study, these approaches predicted an even lower extinction than the measured one. Rather, the best representation of the measured extinction was obtained with an effective refractive index retrieved from a fit to Mie scattering theory assuming spherical particles with a fixed void content. The single-scattering albedo of the porous glassy aerosols was derived using this effective refractive index and was found to be lower than that of the corresponding homogeneous aerosol, indicating stronger relative absorption at the wavelengths measured. The reduced extinction and increased absorption may be of significance in assessing direct, indirect, and semidirect forcing in regions where porous aerosols are expected to be prevalent.

  9. In situ fabrication of depth-type hierarchical CNT/quartz fiber filters for high efficiency filtration of sub-micron aerosols and high water repellency.

    PubMed

    Li, Peng; Zong, Yichen; Zhang, Yingying; Yang, Mengmeng; Zhang, Rufan; Li, Shuiqing; Wei, Fei

    2013-04-21

    We fabricated depth-type hierarchical CNT/quartz fiber (QF) filters through in situ growth of CNTs upon quartz fiber (QF) filters using a floating catalyst chemical vapor deposition (CVD) method. The filter specific area of the CNT/QF filters is more than 12 times higher than that of the pristine QF filters. As a result, the penetration of sub-micron aerosols for CNT/QF filters is reduced by two orders of magnitude, which reaches the standard of high-efficiency particulate air (HEPA) filters. Simultaneously, due to the fluffy brush-like hierarchical structure of CNTs on QFs, the pore size of the hybrid filters only has a small increment. The pressure drop across the CNT/QF filters only increases about 50% with respect to that of the pristine QF filters, leading to an obvious increased quality factor of the CNT/QF filters. Scanning electron microscope images reveal that CNTs are very efficient in capturing sub-micron aerosols. Moreover, the CNT/QF filters show high water repellency, implying their superiority for applications in humid conditions. PMID:23467703

  10. Aerosol radiative effects in the ultraviolet, visible, and near-infrared spectral ranges using long-term aerosol data series over the Iberian Peninsula

    NASA Astrophysics Data System (ADS)

    Mateos, D.; Antón, M.; Toledano, C.; Cachorro, V. E.; Alados-Arboledas, L.; Sorribas, M.; Costa, M. J.; Baldasano, J. M.

    2014-12-01

    A better understanding of aerosol radiative properties is a crucial challenge for climate change studies. This study aims at providing a complete characterization of aerosol radiative effects in different spectral ranges within the shortwave (SW) solar spectrum. For this purpose, long-term data sets of aerosol properties from six AERONET stations located in the Iberian Peninsula (southwestern Europe) have been analyzed in terms of climatological characterization and inter-annual changes. Aerosol information was used as input for the libRadtran model in order to determine the aerosol radiative effect (ARE) 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, yearly aerosol radiative effects in the different spectral ranges were found to be -1.1 < AREUV < -0.7, -5.7 < AREVIS < -3.5, -2.6 < ARENIR < -1.6, and -8.8 < ARESW < -5.7 (in W m-2). Monthly means of ARE showed a seasonal pattern with larger values in spring and summer. The aerosol forcing efficiency (AFE), ARE per unit of aerosol optical depth, has also been evaluated in the four spectral ranges. AFE exhibited a dependence on single scattering albedo as well as a weaker one on the 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 varied with the aerosol types. The predominant aerosol size determined the fractions AFEVIS/AFESW and AFENIR/AFESW. The AFEVIS was the dominant contributor for all aerosol types, although non-absorbing large particles caused more even contribution of VIS and NIR intervals. The AFEUV / AFESW ratio showed a higher value in the case of absorbing fine particles.

  11. Steps Toward an Aerosol-Type Global Climate Data Record

    NASA Astrophysics Data System (ADS)

    Kahn, R. A.

    2015-12-01

    Earth-observing satellites have produced a global record of aerosol optical depth approaching two decades in length. However a global record of aerosol properties at the level-of-detail required for constraining aerosol radiative forcing, aerosol-cloud interaction assessments, and many air quality applications is as yet lacking. Some aerosol-type information is derived from surface-based photometers, and qualitative classification is possible under favorable conditions from MISR, POLDER, and CALIPSO. More detailed particle microphysical properties are obtained from in situ measurements, but sampling is poor, and the suite of coincident measurements required for many applications is rarely acquired. Aerosol transport models can connect remote-sensing and in situ observations to specific aerosol sources, and extrapolate limited observational sampling in space and time. The biggest challenges to producing a global aerosol-type data record are filling gaps in detailed observations, maintaining global observing capabilities, and putting the pieces together. Obtaining detailed particle properties is probably the leading observational gap. One simplifying factor is that, for a given aerosol source and season, aerosol amounts can vary, but the particle properties tend to be repeatable. So an aircraft payload designed and deployed frequently enough to acquire the PDFs of the key variables could fill this gap; the SAM-CAAM (Systematic Aircraft Measurements to Characterize Aerosol Air Masses) concept aims at meeting this objective. Such data would add value to the entire satellite data record, improving the aerosol property assumptions in retrievals, and providing quantitative mass extinction efficiencies to translate between remote-sensing optical constraints and the aerosol mass book-kept in climate models. This will also help putting the pieces together in other ways, by improving the connection between remote-sensing particle types and those defined in models. The

  12. Energy efficiency assessment methods and tools evaluation. Bolling Air Force Base. Revision 1

    SciTech Connect

    McMordie, K.L.; Richman, E.E.; Keller, J.M.; Dixon, D.R.

    1995-05-01

    The goal of the U.S. Department of Energy (DOE) Federal Energy Management Program (FEMP) is to facilitate energy-efficiency improvements at federal facilities. This is accomplished by a balanced program of technology development, facility assessment, and use of cost-sharing procurement mechanisms. Technology development focuses upon the tools, software, and procedures used to identify and evaluate energy-efficiency technologies and improvements. For facility assessment, FEMP provides metering equipment and trained analysts to federal agencies exhibiting a commitment to improve energy use efficiency. To assist in procurement of energy-efficiency measures, FEMP helps federal agencies devise and implement performance contracting and utility demand-side management strategies. Pacific Northwest Laboratory (PNL) supports the FEMP mission of energy systems modernization. Under this charter, the Laboratory and its contractors work with federal facility energy managers to assess and implement energy-efficiency improvements at federal facilities nationwide.

  13. ATI TDA 5A aerosol generator evaluation

    SciTech Connect

    Gilles, D.A.

    1998-07-27

    Oil based aerosol ``Smoke`` commonly used for testing the efficiency and penetration of High Efficiency Particulate Air filters (HEPA) and HEPA systems can produce flammability hazards that may not have been previously considered. A combustion incident involving an aerosol generator has caused an investigation into the hazards of the aerosol used to test HEPA systems at Hanford.

  14. AEROSOL, CLOUDS, AND CLIMATE CHANGE

    SciTech Connect

    SCHWARTZ, S.E.

    2005-09-01

    Earth's climate is thought to be quite sensitive to changes in radiative fluxes that are quite small in absolute magnitude, a few watts per square meter, and in relation to these fluxes in the natural climate. Atmospheric aerosol particles exert influence on climate directly, by scattering and absorbing radiation, and indirectly by modifying the microphysical properties of clouds and in turn their radiative effects and hydrology. The forcing of climate change by these indirect effects is thought to be quite substantial relative to forcing by incremental concentrations of greenhouse gases, but highly uncertain. Quantification of aerosol indirect forcing by satellite- or ground-based remote sensing has proved quite difficult in view of inherent large variation in the pertinent observables such as cloud optical depth, which is controlled mainly by liquid water path and only secondarily by aerosols. Limited work has shown instances of large magnitude of aerosol indirect forcing, with local instantaneous forcing upwards of 50 W m{sup 66}-2. Ultimately it will be necessary to represent aerosol indirect effects in climate models to accurately identify the anthropogenic forcing at present and over secular time and to assess the influence of this forcing in the context of other forcings of climate change. While the elements of aerosol processes that must be represented in models describing the evolution and properties of aerosol particles that serve as cloud condensation particles are known, many important components of these processes remain to be understood and to be represented in models, and the models evaluated against observation, before such model-based representations can confidently be used to represent aerosol indirect effects in climate models.

  15. Economic innovation and efficiency gains as the driving force for accelerating carbon dioxide emissions

    NASA Astrophysics Data System (ADS)

    Garrett, T. J.

    2012-12-01

    It is normally assumed that gains in energy efficiency are one of the best routes that society has available to it for stabilizing future carbon dioxide emissions. For a given degree of economic productivity less energy is consume