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Sample records for additional radiative forcing

  1. Computing the acoustic radiation force exerted on a sphere using the translational addition theorem.

    PubMed

    Silva, Glauber T; Baggio, André L; Lopes, J Henrique; Mitri, Farid G

    2015-03-01

    In this paper, the translational addition theorem for spherical functions is employed to calculate the acoustic radiation force produced by an arbitrary shaped beam on a sphere arbitrarily suspended in an inviscid fluid. The procedure is also based on the partial-wave expansion method, which depends on the beam-shape and scattering coefficients. Given a set of beam-shape coefficients (BSCs) for an acoustic beam relative to a reference frame, the translational addition theorem can be used to obtain the BSCs relative to the sphere positioned anywhere in the medium. The scattering coefficients are obtained from the acoustic boundary conditions across the sphere's surface. The method based on the addition theorem is particularly useful to avoid quadrature schemes to obtain the BSCs. We use it to compute the acoustic radiation force exerted by a spherically focused beam (in the paraxial approximation) on a silicone-oil droplet (compressible fluid sphere). The analysis is carried out in the Rayleigh (i.e., the particle diameter is much smaller than the wavelength) and Mie (i.e., the particle diameter is of the order of the wavelength or larger) scattering regimes. The obtained results show that the paraxial focused beam can only trap particles in the Rayleigh scattering regime. PMID:25768823

  2. Resonance scattering and radiation force calculations for an elastic cylinder using the translational addition theorem for cylindrical wave functions

    SciTech Connect

    Mitri, F. G.

    2015-09-15

    The standard Resonance Scattering Theory (RST) of plane waves is extended for the case of any two-dimensional (2D) arbitrarily-shaped monochromatic beam incident upon an elastic cylinder with arbitrary location using an exact methodology based on Graf’s translational addition theorem for the cylindrical wave functions. The analysis is exact as it does not require numerical integration procedures. The formulation is valid for any cylinder of finite size and material that is immersed in a nonviscous fluid. Partial-wave series expansions (PWSEs) for the incident, internal and scattered linear pressure fields are derived, and the analysis is further extended to obtain generalized expressions for the on-axis and off-axis acoustic radiation force components. The wave-fields are expressed using generalized PWSEs involving the beam-shape coefficients (BSCs) and the scattering coefficients of the cylinder. The off-axial BSCs are expressed analytically in terms of an infinite PWSE with emphasis on the translational offset distance d. Numerical computations are considered for a zeroth-order quasi-Gaussian beam chosen as an example to illustrate the analysis. Acoustic resonance scattering directivity diagrams are calculated by subtracting an appropriate background from the expression of the scattered pressure field. In addition, computations for the radiation force exerted on an elastic cylinder centered on the axis of wave propagation of the beam, and shifted off-axially are analyzed and discussed.

  3. Radiative Forcing by Contrails

    NASA Technical Reports Server (NTRS)

    Meerkoetter, R.; Schumann, U.; Doelling, D. R.; Nakajima, T.; Tsushima, Y.

    1999-01-01

    A parametric study of the instantaneous radiative impact of contrails is presented using three different radiative transfer models for a series of model atmospheres and cloud parameters. Contrails are treated as geometrically and optically thin plane parallel homogeneous cirrus layers in a static atmospheres The ice water content is varied as a function of ambient temperature. The model atmospheres include tropical, mid-latitude, and subarctic summer and winter atmospheres Optically thin contrails cause a positive net forcing at top of the atmosphere. At the surface the radiative forcing is negative during daytime. The forcing increases with the optical depth and the amount of contrail cover. At the top of the atmosphere a mean contrail cover of 0.1% with average optical depth of 0.2 to 0.5 causes about 0.01 to 0.03 W/m(exp 2)a daily mean instantaneous radiative forcing. Contrails cool the surface during the day and heat the surface during the night, and hence reduce the daily temperature amplitude The net effect depends strongly on the daily variation of contrail cloud cover. The indirect radiative forcing due to particle changes in natural cirrus clouds may be of the same magnitude as the direct one due to additional cover.

  4. Radiative forcing of climate

    NASA Technical Reports Server (NTRS)

    Ramanswamy, V.; Shine, Keith; Leovy, Conway; Wang, Wei-Chyung; Rodhe, Henning; Wuebbles, Donald J.; Ding, M.; Lelieveld, Joseph; Edmonds, Jae A.; Mccormick, M. Patrick

    1991-01-01

    An update of the scientific discussions presented in Chapter 2 of the Intergovernmental Panel on Climate Change (IPCC) report is presented. The update discusses the atmospheric radiative and chemical species of significance for climate change. There are two major objectives of the present update. The first is an extension of the discussion on the Global Warming Potentials (GWP's), including a reevaluation in view of the updates in the lifetimes of the radiatively active species. The second important objective is to underscore major developments in the radiative forcing of climate due to the observed stratospheric ozone losses occurring between 1979 and 1990.

  5. Radiative Forcing of Climate Change

    SciTech Connect

    Ramaswamy, V.; Boucher, Olivier; Haigh, J.; Hauglustaine, D.; Haywood, J.; Myhre, G.; Nakajima, Takahito; Shi, Guangyu; Solomon, S.; Betts, Robert E.; Charlson, R.; Chuang, C. C.; Daniel, J. S.; Del Genio, Anthony D.; Feichter, J.; Fuglestvedt, J.; Forster, P. M.; Ghan, Steven J.; Jones, A.; Kiehl, J. T.; Koch, D.; Land, C.; Lean, J.; Lohmann, Ulrike; Minschwaner, K.; Penner, Joyce E.; Roberts, D. L.; Rodhe, H.; Roelofs, G.-J.; Rotstayn, Leon D.; Schneider, T. L.; Schumann, U.; Schwartz, Stephen E.; Schwartzkopf, M. D.; Shine, K. P.; Smith, Steven J.; Stevenson, D. S.; Stordal, F.; Tegen, I.; van Dorland, R.; Zhang, Y.; Srinivasan, J.; Joos, Fortunat

    2001-10-01

    Chapter 6 of the IPCC Third Assessment Report Climate Change 2001: The Scientific Basis. Sections include: Executive Summary 6.1 Radiative Forcing 6.2 Forcing-Response Relationship 6.3 Well-Mixed Greenhouse Gases 6.4 Stratospheric Ozone 6.5 Radiative Forcing By Tropospheric Ozone 6.6 Indirect Forcings due to Chemistry 6.7 The Direct Radiative Forcing of Tropospheric Aerosols 6.8 The Indirect Radiative Forcing of Tropospheric Aerosols 6.9 Stratospheric Aerosols 6.10 Land-use Change (Surface Albedo Effect) 6.11 Solar Forcing of Climate 6.12 Global Warming Potentials hydrocarbons 6.13 Global Mean Radiative Forcings 6.14 The Geographical Distribution of the Radiative Forcings 6.15 Time Evolution of Radiative Forcings Appendix 6.1 Elements of Radiative Forcing Concept References.

  6. Aerosol Absorption and Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Stier, Philip; Seinfeld, J. H.; Kinne, Stefan; Boucher, Olivier

    2007-01-01

    We present a comprehensive examination of aerosol absorption with a focus on evaluating the sensitivity of the global distribution of aerosol absorption to key uncertainties in the process representation. For this purpose we extended the comprehensive aerosol-climate model ECHAM5-HAM by effective medium approximations for the calculation of aerosol effective refractive indices, updated black carbon refractive indices, new cloud radiative properties considering the effect of aerosol inclusions, as well as by modules for the calculation of long-wave aerosol radiative properties and instantaneous aerosol forcing. The evaluation of the simulated aerosol absorption optical depth with the AERONET sun-photometer network shows a good agreement in the large scale global patterns. On a regional basis it becomes evident that the update of the BC refractive indices to Bond and Bergstrom (2006) significantly improves the previous underestimation of the aerosol absorption optical depth. In the global annual-mean, absorption acts to reduce the shortwave anthropogenic aerosol top-of-atmosphere (TOA) radiative forcing clear-sky from -0.79 to -0.53 W m(sup -2) (33%) and all-sky from -0.47 to -0.13W m(sup -2 (72%). Our results confirm that basic assumptions about the BC refractive index play a key role for aerosol absorption and radiative forcing. The effect of the usage of more accurate effective medium approximations is comparably small. We demonstrate that the diversity in the AeroCom land-surface albedo fields contributes to the uncertainty in the simulated anthropogenic aerosol radiative forcings: the usage of an upper versus lower bound of the AeroCom land albedos introduces a global annual-mean TOA forcing range of 0.19W m(sup -2) (36%) clear-sky and of 0.12W m(sup -2) (92%) all-sky. The consideration of black carbon inclusions on cloud radiative properties results in a small global annual-mean all-sky absorption of 0.05W m(sup -2) and a positive TOA forcing perturbation of 0

  7. Radiation Therapy: Additional Treatment Options

    MedlinePlus

    ... This is refered to as immunotherapy . Intraoperative Radiation Therapy Radiation therapy given during surgery is called intraoperative ... external beam therapy or as brachytherapy . Novel Targeted Therapies Cancer doctors now know much more about how ...

  8. Inhomogeneous radiative forcing of homogeneous greenhouse gases

    NASA Astrophysics Data System (ADS)

    Huang, Yi; Tan, Xiaoxiao; Xia, Yan

    2016-03-01

    Radiative forcing of a homogeneous greenhouse gas (HGG) can be very inhomogeneous because the forcing is dependent on other atmospheric and surface variables. In the case of doubling CO2, the monthly mean instantaneous forcing at the top of the atmosphere is found to vary geographically and temporally from positive to negative values, with the range (-2.5-5.1 W m-2) being more than 3 times the magnitude of the global mean value (2.3 W m-2). The vertical temperature change across the atmospheric column (temperature lapse rate) is found to be the best single predictor for explaining forcing variation. In addition, the masking effects of clouds and water vapor also contribute to forcing inhomogeneity. A regression model that predicts forcing from geophysical variables is constructed. This model can explain more than 90% of the variance of the forcing. Applying this model to analyzing the forcing variation in the Climate Model Intercomparison Project Phase 5 models, we find that intermodel discrepancy in CO2 forcing caused by model climatology leads to considerable discrepancy in their projected change in poleward energy transport.

  9. 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.

  10. 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

  11. 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...

  12. Radiation Forces and Torques without Stress (Tensors)

    ERIC Educational Resources Information Center

    Bohren, Craig F.

    2011-01-01

    To understand radiation forces and torques or to calculate them does not require invoking photon or electromagnetic field momentum transfer or stress tensors. According to continuum electromagnetic theory, forces and torques exerted by radiation are a consequence of electric and magnetic fields acting on charges and currents that the fields induce…

  13. Simulation of the global contrail radiative forcing: A sensitivity analysis

    NASA Astrophysics Data System (ADS)

    Yi, Bingqi; Yang, Ping; Liou, Kuo-Nan; Minnis, Patrick; Penner, Joyce E.

    2012-12-01

    The contrail radiative forcing induced by human aviation activity is one of the most uncertain contributions to climate forcing. An accurate estimation of global contrail radiative forcing is imperative, and the modeling approach is an effective and prominent method to investigate the sensitivity of contrail forcing to various potential factors. We use a simple offline model framework that is particularly useful for sensitivity studies. The most-up-to-date Community Atmospheric Model version 5 (CAM5) is employed to simulate the atmosphere and cloud conditions during the year 2006. With updated natural cirrus and additional contrail optical property parameterizations, the RRTMG Model (RRTM-GCM application) is used to simulate the global contrail radiative forcing. Global contrail coverage and optical depth derived from the literature for the year 2002 is used. The 2006 global annual averaged contrail net (shortwave + longwave) radiative forcing is estimated to be 11.3 mW m-2. Regional contrail radiative forcing over dense air traffic areas can be more than ten times stronger than the global average. A series of sensitivity tests are implemented and show that contrail particle effective size, contrail layer height, the model cloud overlap assumption, and contrail optical properties are among the most important factors. The difference between the contrail forcing under all and clear skies is also shown.

  14. Radiation force and balance of electromagnetic momentum

    NASA Astrophysics Data System (ADS)

    Campos, I.; Jiménez, J. L.; Roa-Neri, J. A. E.

    2016-07-01

    Some force densities can be expressed as a divergence of a stress tensor, as is the case with the electromagnetic force density. We have shown elsewhere that from the Maxwell equations several balance equations of electromagnetic momentum can be derived, depending on the form these equations are expressed in terms of fields E, D, B, H, and polarisations P and M. These balance equations imply different force densities and different stress tensors, providing a great flexibility to solve particular problems. Among these force densities we have found some proposed in the past with plausibility arguments, like the Einstein–Laub force density, while other proposed force densities appear as particular or limit cases of these general force densities, like the Helmholtz force density. We calculate the radiation force of an electromagnetic wave incident on a semi-infinite negligibly absorbing material using these balance equations, corroborating in this way that the surface integration of the stress tensor gives the same result that the calculation made through a volume integration of the force density, as done by Bohren. As is usual in applications of Gauss’s theorem, the surface on which the surface integral is to be performed must be chosen judiciously, and due care of discontinuities on the boundary conditions must be taken. Advanced undergraduates and graduate students will find a different approach to new aspects of the interaction of radiation with matter.

  15. Precipitation Response to Regional Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Shindell, D. T.; Voulgarakis, A.; Faluvegi, G.; Milly, G.

    2012-01-01

    Precipitation shifts can have large impacts on human society and ecosystems. Many aspects of how inhomogeneous radiative forcings influence precipitation remain unclear, however. Here we investigate regional precipitation responses to various forcings imposed in different latitude bands in a climate model. We find that several regions show strong, significant responses to most forcings, but that the magnitude and even the sign depends upon the forcing location and type. Aerosol and ozone forcings typically induce larger responses than equivalent carbon dioxide (CO2) forcing, and the influence of remote forcings often outweighs that of local forcings. Consistent with this, ozone and especially aerosols contribute greatly to precipitation changes over the Sahel and South and East Asia in historical simulations, and inclusion of aerosols greatly increases the agreement with observed trends in these areas, which cannot be attributed to either greenhouse gases or natural forcings. Estimates of precipitation responses derived from multiplying our Regional Precipitation Potentials (RPP; the response per unit forcing relationships) by historical forcings typically capture the actual response in full transient climate simulations fairly well, suggesting that these relationships may provide useful metrics. The strong sensitivity to aerosol and ozone forcing suggests that although some air quality improvements may unmask greenhouse gas-induced warming, they have large benefits for reducing regional disruption of the hydrologic cycle.

  16. 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

  17. Radiative Forcing Over Ocean by Ship Wakes

    NASA Technical Reports Server (NTRS)

    Gatebe, Charles K.; Wilcox, E.; Poudyal, R.; Wang, J.

    2011-01-01

    Changes in surface albedo represent one of the main forcing agents that can counteract, to some extent, the positive forcing from increasing greenhouse gas concentrations. Here, we report on enhanced ocean reflectance from ship wakes over the Pacific Ocean near the California coast, where we determined, based on airborne radiation measurements that ship wakes can increase reflected sunlight by more than 100%. We assessed the importance of this increase to climate forcing, where we estimated the global radiative forcing of ship wakes to be -0.00014 plus or minus 53% Watts per square meter assuming a global distribution of 32331 ships of size of greater than or equal to 100000 gross tonnage. The forcing is smaller than the forcing of aircraft contrails (-0.007 to +0.02 Watts per square meter), but considering that the global shipping fleet has rapidly grown in the last five decades and this trend is likely to continue because of the need of more inter-continental transportation as a result of economic globalization, we argue that the radiative forcing of wakes is expected to be increasingly important especially in harbors and coastal regions.

  18. 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.

  19. Transthoracic Cardiac Acoustic Radiation Force Impulse Imaging

    NASA Astrophysics Data System (ADS)

    Bradway, David Pierson

    heart function. Presented is the first use of transthoracic ARFI imaging in a serial study of heart failure in a porcine model. Results demonstrate the ability of transthoracic ARFI to image cyclically-varying stiffness changes in healthy and infarcted myocardium under good B-mode imaging conditions at depths in the range of 3-5 cm. Challenging imaging scenarios such as deep regions of interest, vigorous lateral motion and stable, reverberant clutter are analyzed and discussed. Results are then presented from the first study of clinical feasibility of transthoracic cardiac ARFI imaging. At the Duke University Medical Center, healthy volunteers and patients having magnetic resonance imaging-confirmed apical infarcts were enrolled for the study. The number of patients who met the inclusion criteria in this preliminary clinical trial was low, but results showed that the limitations seen in animal studies were not overcome by allowing transmit power levels to exceed the FDA mechanical index (MI) limit. The results suggested the primary source of image degradation was clutter rather than lack of radiation force. Additionally, the transthoracic method applied in its present form was not shown capable of tracking propagating ARFI-induced shear waves in the myocardium. Under current instrumentation and processing methods, results of these studies support feasibility for transthoracic ARFI in high-quality B-Mode imaging conditions. Transthoracic ARFI was not shown sensitive to infarct or to tracking heart failure in the presence of clutter and signal decorrelation. This work does provide evidence that transthoracic ARFI imaging is a safe non-invasive tool, but clinical efficacy as a diagnostic tool will need to be addressed by further development to overcome current challenges and increase robustness to sources of image degradation.

  20. Tropical cirrus cloud radiative forcing: Sensitivity studies

    SciTech Connect

    Jensen, E.J.; Kinne, S.; Toon, O.B.

    1994-09-01

    We have performed one dimensional radiative transfer calculations to evaluate the impact of cirrus clouds on the tropical radiation budget. We investigate the sensitivity of solar and infrared fluxes to cloud optical depth, particle size distributions, and cloud height. If the observed solar cloud forcing in excess of 100 W/sq m is to be attributed to cirrus anvils alone, then the optical depth of these anvils must be at least 5 (assuming 50% cloud cover and an ice crystal effective radius of 15 microns). The net radiative forcing of cirrus near the tropical tropopause is positive (heating) for cloud optical depths less than about 16 and negative (cooling) for larger optical depths. If cirrus clouds alone are responsible for the equal and opposite shortwave and longwave cloud forcing in excess of 100 W/sq m observed by Earth Radiation Budget Experiment (ERBE), then the cirrus must typically take the form of deep, optically thick clouds with relatively small particles (radii of 10-20 microns) and cloud-tops well below the tropopause. The maintenance of this balance on monthly time scales can be attributed to a variety of correlations: The cloud cover of optically thick cirrus or thin cirrus overlying low-level stratus clouds could vary; or cirrus anvil height cloud increase along with a decrease in the ice crystal effective radius and an increase in optical depth. It would be of great interest to determine observationally which of these correlations is responsible for the observed lack of variation in cloud forcing.

  1. Implication of radiative forcing distribution for energy transport

    NASA Astrophysics Data System (ADS)

    Huang, Yi

    2016-04-01

    Radiative forcing of a homogeneous greenhouse gas can be very inhomogeneous because the forcing is dependent on other atmospheric and surface variables. In the case of doubling CO2, the mean instantaneous forcing at the top of the atmosphere is found to vary geographically and temporally from positive to negative values, with the range being more than three times the magnitude of the global mean value. The vertical temperature change across the atmospheric column (temperature lapse rate) is found to be the best single predictor for explaining forcing variation. In addition, the masking effects of clouds and water vapor also contribute to forcing inhomogeneity. A regression model that predicts forcing from geophysical variables is constructed. This model can explain more than 90% of the variance of the forcing. Applying this model to analyzing the forcing variation in the CMIP5 models, we find that inter-model discrepancy in CO2 forcing caused by model climatology leads to considerable discrepancy in their projected change in poleward energy transport.

  2. Additive CHARMM force field for naturally occurring modified ribonucleotides.

    PubMed

    Xu, You; Vanommeslaeghe, Kenno; Aleksandrov, Alexey; MacKerell, Alexander D; Nilsson, Lennart

    2016-04-15

    More than 100 naturally occurring modified nucleotides have been found in RNA molecules, in particular in tRNAs. We have determined molecular mechanics force field parameters compatible with the CHARMM36 all-atom additive force field for all these modifications using the CHARMM force field parametrization strategy. Emphasis was placed on fine tuning of the partial atomic charges and torsion angle parameters. Quantum mechanics calculations on model compounds provided the initial set of target data, and extensive molecular dynamics simulations of nucleotides and oligonucleotides in aqueous solutions were used for further refinement against experimental data. The presented parameters will allow for computational studies of a wide range of RNAs containing modified nucleotides, including the ribosome and transfer RNAs. PMID:26841080

  3. Additive CHARMM force field for naturally occurring modified ribonucleotides

    PubMed Central

    Xu, You; Vanommeslaeghe, Kenno; Aleksandrov, Alexey; MacKerell, Alexander D.

    2016-01-01

    More than 100 naturally occurring modified nucleotides have been found in RNA molecules, in particular in tRNAs. We have determined molecular mechanics force field parameters compatible with the CHARMM36 all‐atom additive force field for all these modifications using the CHARMM force field parametrization strategy. Emphasis was placed on fine tuning of the partial atomic charges and torsion angle parameters. Quantum mechanics calculations on model compounds provided the initial set of target data, and extensive molecular dynamics simulations of nucleotides and oligonucleotides in aqueous solutions were used for further refinement against experimental data. The presented parameters will allow for computational studies of a wide range of RNAs containing modified nucleotides, including the ribosome and transfer RNAs. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc. PMID:26841080

  4. Mariner Venus/Mercury 1973 solar radiation force and torques

    NASA Technical Reports Server (NTRS)

    Georgevic, R. M.

    1974-01-01

    The need for an improvement of the mathematical model of the solar radiation force and torques for the Mariner Venus/Mercury spacecraft arises from the fact that this spacecraft will be steering toward the inner planets (Venus and Mercury), where, due to the proximity of the Sun, the effect of the solar radiation pressure is much larger than it was on the antecedent Mariner spacecraft, steering in the opposite direction. Therefore, although the model yielded excellent results in the case of the Mariner 9 Mars Orbiter, additional effects of negligible magnitudes for the previous missions of the Mariner spacecraft should now be included in the model. This study examines all such effects and incorporates them into the already existing model, as well as using the improved model for calculation of the solar radiation force and torques acting on the Mariner Venus/Mercury spacecraft.

  5. Sea ice radiative forcing, sea ice area, and climate sensitivity

    NASA Astrophysics Data System (ADS)

    Caldeira, Ken; Cvijanovic, Ivana

    2014-05-01

    Changes in sea ice cover affect climate sensitivity by modifying albedo and surface heat flux exchange, which in turn affect the absorbed solar radiation at the surface as well as cloud cover, atmospheric water content and poleward atmospheric heat transport. Here, we use a configuration of the Community Earth System Model 1.0.4 with a slab ocean model and a thermodynamic-dynamic sea ice model to investigate the overall net effect of feedbacks associated with the sea ice loss. We analyze the strength of the overall sea ice feedback in terms of two factors: the sensitivity of sea ice area to changes in temperature, and the sensitivity of sea ice radiative forcing to changes in sea ice area. In this model configuration, sea ice area decreases by ~3 × 1012 m2 per K of global warming, while the effective global radiative forcing per square meter of sea ice loss is ~0.1 × 10-12 W m-2. The product of these two terms (~0.3 W m-2 K-1) approximately equals the difference in climate feedback parameter found in simulations with sea ice response (1.05 W m-2 K-1) and simulations without sea ice response (1.31 W m-2 K-1 or 1.35 W m-2 K-1, depending on the method used to disable changes in sea ice cover). Thus, we find that in our model simulations, sea ice response accounts for about 20% to 22% of the climate sensitivity to an imposed change in radiative forcing. In our model, the additional radiative forcing resulting from a loss of all sea ice in the 'pre-industrial' state is comparable to but somewhat less than the radiative forcing from a doubling of atmospheric CO2 content.

  6. Sea Ice Radiative Forcing, Sea Ice Area, and Climate Sensitivity

    NASA Astrophysics Data System (ADS)

    Caldeira, K.; Cvijanovic, I.

    2014-12-01

    Changes in sea ice cover affect climate sensitivity by modifying albedo and surface heat flux exchange, which in turn affect the absorbed solar radiation at the surface as well as cloud cover, atmospheric water content and poleward atmospheric heat transport. Here, we use a configuration of the Community Earth System Model 1.0.4 with a slab ocean model and a thermodynamic-dynamic sea ice model to investigate the overall net effect of feedbacks associated with the sea ice loss. We analyze the strength of the overall sea ice feedback in terms of two factors: the sensitivity of sea ice area to changes in temperature, and the sensitivity of sea ice radiative forcing to changes in sea ice area. In this model configuration, sea ice area decreases by ~3 × 1012 m2 per K of global warming, while the effective global radiative forcing per unit area of sea ice loss is ~0.1 × 10-12 W m-2. The product of these two terms (~0.3 W m-2 K-1) approximately equals the difference in climate feedback parameter found in simulations with sea ice response (1.05 W m-2 K-1) and simulations without sea ice response (1.31 W m-2 K-1 or 1.35 W m-2 K-1, depending on the method used to disable the changes in sea ice cover). Thus, we find that in our model simulations, sea ice response accounts for about 20% to 22% of the climate sensitivity to an imposed change in radiative forcing. In our model, the additional radiative forcing resulting from a loss of all sea-ice in the "pre-industrial" state is comparable to but somewhat less than the radiative forcing from a doubling of atmospheric CO2 content.

  7. 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.

  8. Radiative Forcing and Climate Response: From Paleoclimate to Future Climate

    NASA Astrophysics Data System (ADS)

    Caldeira, K.; Cao, L.

    2011-12-01

    The concept of radiative forcing was introduced to allow comparison of climate effects of different greenhouse gases. In the classic view, radiative forcing is applied to the climate system and the climate responds to this forcing, approaching some equilibrium temperature change that is the product of the radiative forcing times the 'climate sensitivity' to radiative forcing. However, this classic view is oversimplified in several respects. Climate forcing and response often cannot be clearly separated. When carbon dioxide is added to the atmosphere, within days, the increased absorption of longwave radiation begins to warm the interior of the troposphere, affecting various tropospheric properties. Especially in the case of aerosols, it has been found that considering rapid tropospheric adjustment gives a better predictor of "equilibrium" climate change than does the classic definition of radiative forcing. Biogeochemistry also provides additional feedbacks on the climate system. It is generally thought that biogeochemistry helps diminish climate sensitivity to a carbon dioxide emission, since carbon dioxide tends to stimulate carbon dioxide uptake by land plants and the ocean. However, there is potential to destabilize carbon locked up in permafrost and at least some possibility to destabilize methane in continental shelf sediments. Furthermore, wetlands may provide a significant methane feedback. These and other possible biogeochemical feedbacks have the potential to greatly increase the sensitivity of the climate system to carbon dioxide emissions. As time scales extend out to millennia, the large ice sheets can begin to play an important role. In addition to affecting atmospheric flows by their sheer bulk, ice sheets tend to reflect a lot of energy to space. If carbon dioxide remains in the atmosphere long enough, there is potential to melt back the large ice sheets, which would add additional warming to the climate system. It is likely that these millennial

  9. 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.

  10. Material fabrication using acoustic radiation forces

    SciTech Connect

    Sinha, Naveen N.; Sinha, Dipen N.; Goddard, Gregory Russ

    2015-12-01

    Apparatus and methods for using acoustic radiation forces to order particles suspended in a host liquid are described. The particles may range in size from nanometers to millimeters, and may have any shape. The suspension is placed in an acoustic resonator cavity, and acoustical energy is supplied thereto using acoustic transducers. The resulting pattern may be fixed by using a solidifiable host liquid, forming thereby a solid material. Patterns may be quickly generated; typical times ranging from a few seconds to a few minutes. In a one-dimensional arrangement, parallel layers of particles are formed. With two and three dimensional transducer arrangements, more complex particle configurations are possible since different standing-wave patterns may be generated in the resonator. Fabrication of periodic structures, such as metamaterials, having periods tunable by varying the frequency of the acoustic waves, on surfaces or in bulk volume using acoustic radiation forces, provides great flexibility in the creation of new materials. Periodicities may range from millimeters to sub-micron distances, covering a large portion of the range for optical and acoustical metamaterials.

  11. Radiative forcing caused by rocket engine emissions

    NASA Astrophysics Data System (ADS)

    Ross, Martin N.; Sheaffer, Patti M.

    2014-04-01

    Space transportation plays an important and growing role in Earth's economic system. Rockets uniquely emit gases and particles directly into the middle and upper atmosphere where exhaust from hundreds of launches accumulates, changing atmospheric radiation patterns. The instantaneous radiative forcing (RF) caused by major rocket engine emissions CO2, H2O, black carbon (BC), and Al2O3 (alumina) is estimated. Rocket CO2 and H2O emissions do not produce significant RF. BC and alumina emissions, under some scenarios, have the potential to produce significant RF. Absorption of solar flux by BC is likely the main RF source from rocket launches. In a new finding, alumina particles, previously thought to cool the Earth by scattering solar flux back to space, absorb outgoing terrestrial longwave radiation, resulting in net positive RF. With the caveat that BC and alumina microphysics are poorly constrained, we find that the present-day RF from rocket launches equals 16 ± 8 mW m-2. The relative contributions from BC, alumina, and H2O are 70%, 28%, and 2%. respectively. The pace of rocket launches is predicted to grow and space transport RF could become comparable to global aviation RF in coming decades. Improved understanding of rocket emission RF requires more sophisticated modeling and improved data describing particle microphysics.

  12. Nonlinearly Additive Forces in Multivalent Ligand Binding to a Single Protein Revealed with Force Spectroscopy

    SciTech Connect

    Ratto, T V; Rudd, R E; Langry, K C; Balhorn, R L; McElfresh, M W

    2005-07-15

    We present evidence of multivalent interactions between a single protein molecule and multiple carbohydrates at a pH where the protein can bind four ligands. The evidence is based not only on measurements of the force required to rupture the bonds formed between ConcanavalinA (ConA) and {alpha}-D-mannose, but also on an analysis of the polymer-extension force curves to infer the polymer architecture that binds the protein to the cantilever and the ligands to the substrate. We find that although the rupture forces for multiple carbohydrate connections to a single protein are larger than the rupture force for a single connection, they do not scale additively with increasing number. Specifically, the most common rupture forces are approximately 46, 66, and 85 pN, which we argue corresponds to 1, 2, and 3 ligands being pulled simultaneously from a single protein as corroborated by an analysis of the linkage architecture. As in our previous work polymer tethers allow us to discriminate between specific and non-specific binding. We analyze the binding configuration (i.e. serial versus parallel connections) through fitting the polymer stretching data with modified Worm-Like Chain (WLC) models that predict how the effective stiffness of the tethers is affected by multiple connections. This analysis establishes that the forces we measure are due to single proteins interacting with multiple ligands, the first force spectroscopy study that establishes single-molecule multivalent binding unambiguously.

  13. 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).

  14. Magnetic resonance acoustic radiation force imaging

    PubMed Central

    McDannold, Nathan; Maier, Stephan E.

    2008-01-01

    Acoustic radiation force impulse imaging is an elastography method developed for ultrasound imaging that maps displacements produced by focused ultrasound pulses systematically applied to different locations. The resulting images are “stiffness weighted” and yield information about local mechanical tissue properties. Here, the feasibility of magnetic resonance acoustic radiation force imaging (MR-ARFI) was tested. Quasistatic MR elastography was used to measure focal displacements using a one-dimensional MRI pulse sequence. A 1.63 or 1.5 MHz transducer supplied ultrasound pulses which were triggered by the magnetic resonance imaging hardware to occur before a displacement-encoding gradient. Displacements in and around the focus were mapped in a tissue-mimicking phantom and in an ex vivo bovine kidney. They were readily observed and increased linearly with acoustic power in the phantom (R2=0.99). At higher acoustic power levels, the displacement substantially increased and was associated with irreversible changes in the phantom. At these levels, transverse displacement components could also be detected. Displacements in the kidney were also observed and increased after thermal ablation. While the measurements need validation, the authors have demonstrated the feasibility of detecting small displacements induced by low-power ultrasound pulses using an efficient magnetic resonance imaging pulse sequence that is compatible with tracking of a dynamically steered ultrasound focal spot, and that the displacement increases with acoustic power. MR-ARFI has potential for elastography or to guide ultrasound therapies that use low-power pulsed ultrasound exposures, such as drug delivery. PMID:18777934

  15. Acoustic radiation force impulse of the liver

    PubMed Central

    D’Onofrio, Mirko; Crosara, Stefano; De Robertis, Riccardo; Canestrini, Stefano; Demozzi, Emanuele; Gallotti, Anna; Pozzi Mucelli, Roberto

    2013-01-01

    Acoustic radiation force impulse (ARFI) imaging is a new and promising ultrasound-based diagnostic technique that, evaluating the wave propagation speed, allows the assessment of the tissue stiffness. ARFI is implemented in the ultrasound scanner. By short-duration acoustic radiation forces (less than 1 ms), localized displacements are generated in a selected region of interest not requiring any external compression so reducing the operator dependency. The generated wave scan provides qualitative or quantitative (wave velocity values) responses. Several non-invasive methods for assessing the staging of fibrosis are used, in order to avoid liver biopsy. Liver function tests and transient elastography are non-invasive, sensitive and accurate tools for the assessment of liver fibrosis and for the discrimination between cirrhotic and non-cirrhotic liver. Many published studies analyse ARFI performance and feasibility in studying diffuse liver diseases and compare them to other diagnostic imaging modalities such as conventional ultrasonography and transient elastography. Solid focal liver lesions, both benign and malignant, are common findings during abdominal examinations. The accurate characterization and differential diagnosis are important aims of all the imaging modalities available today. Only few papers describe the application of ARFI technology in the study of solid focal liver lesions, with different results. In the present study, the existing literature, to the best of our knowledge, about ARFI application on diffuse and focal liver pathology has been evaluated and results and statistical analyses have been compared, bringing to the conclusion that ARFI can be used in the study of the liver with similar accuracy as transient elastography in diagnosing significant fibrosis or cirrhosis and has got some advantages in respect to transient elastography since it does not require separate equipment, better displays anatomical structures and measurements can be

  16. Assigning a Price to Radiative Forcing: Methods, Results, and Implications

    NASA Astrophysics Data System (ADS)

    Lutz, D. A.; Howarth, R. B.

    2015-12-01

    Climate change mitigation frameworks have increasingly begun to include components that involve active management of the land surface. Predominantly, these programs focus on the sequestration of greenhouse gasses in vegetation and soils, generating offset credits for projects which demonstrate considerable storage. However, it is widely known that biogeophysical interactions between the land surface and the atmosphere, such as latent and sensible heat flux, albedo radiative forcing, and surface roughness, can in many cases outweigh the influence of greenhouse gas storage on global and local climate. Surface albedo, in particular, has attracted attention in the context of these frameworks because it has been shown to influence the overall climate benefits of high-latitude forest growth through tradeoffs between carbon sequestration and radiative forcing from seasonal snow cover albedo. Here we review a methodology for pricing albedo-related radiative forcing through the use of an integrated assessment model, present the results under several emissions and social preference scenarios, and describe the implications that this pricing methodology may have on forest land management in the Northeastern United States. Additionally, we investigate the consequences of projected decreased winter precipitation on the net climate benefits of snow albedo throughout the state of New Hampshire, USA.

  17. Black Carbon Vertical Profiles Strongly Affect Its Radiative Forcing Uncertainty

    NASA Technical Reports Server (NTRS)

    Samset, B. H.; Myhre, G.; Schulz, M.; Balkanski, Y.; Bauer, S.; Berntsen, T. K.; Bian, H.; Bellouin, N.; Diehl, T.; Easter, R. C.; Ghan, S. J.; Iversen, T.; Kinne, S.; Kirkevag, A.; Lamarque, J.-F.; Lin, G.; Liu, X.; Penner, J. E.; Seland, O.; Skeie, R. B.; Stier, P.; Takemura, T.; Tsigaridis, K.; Zhang, K.

    2013-01-01

    The impact of black carbon (BC) aerosols on the global radiation balance is not well constrained. Here twelve global aerosol models are used to show that at least 20% of the present uncertainty in modeled BC direct radiative forcing (RF) is due to diversity in the simulated vertical profile of BC mass. Results are from phases 1 and 2 of the global aerosol model intercomparison project (AeroCom). Additionally, a significant fraction of the variability is shown to come from high altitudes, as, globally, more than 40% of the total BC RF is exerted above 5 km. BC emission regions and areas with transported BC are found to have differing characteristics. These insights into the importance of the vertical profile of BC lead us to suggest that observational studies are needed to better characterize the global distribution of BC, including in the upper troposphere.

  18. Black Carbon Vertical Profiles Strongly Affect its Radiative Forcing Uncertainty

    SciTech Connect

    Samset, B. H.; Myhre, G.; Schulz, M.; Balkanski, Y.; Bauer, Susanne E.; Berntsen, T.; Bian, Huisheng; Bellouin, N.; Diehl, T.; Easter, Richard C.; Ghan, Steven J.; Iversen, T.; Kinne, Stefan; Kirkevag, A.; Lamarque, J.-F.; Lin, G.; Liu, Xiaohong; Penner, Joyce E.; Seland, O.; Skeie, R. B.; Stier, P.; Takemura, T.; Tsigaridis, K.; Zhang, Kai

    2013-03-01

    The impact of black carbon (BC) aerosols on the global radiation balance is not well constrained. Here twelve global aerosol models are used to show that at least 20% of the present uncertainty in modeled BC direct radiative forcing (RF) is due to diversity in the simulated vertical profile of BC mass. Results are from phases 1 and 2 of the global aerosol model intercomparison project (AeroCom). Additionally, a significant fraction of the variability is shown to come from high altitudes, as, globally, more than 40% of the total BC RF is exerted above 5 km. BC emission regions and areas with transported BC are found to have differing characteristics. These insights into the importance of the vertical profile of BC lead us to suggest that observational studies are needed to better characterize the global distribution of BC, including in the upper troposphere.

  19. 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.

  20. SOURCE ATTRIBUTION OF RADIATIVE FORCING FROM SHORT LIVED CLIMATE FORCING AGENTS

    EPA Science Inventory

    The immediate project result is quantification of the pre-industrial to present forcing for anthropogenic emissions, the radiative effects of natural emissions, and spatial distribution of the radiative forcing efficiency for key aerosol and O3 precursors (i.e., mW/m2<...

  1. The Radiative Forcing from Biogenic Secondary Organic Aerosol

    NASA Astrophysics Data System (ADS)

    Scott, C. E.; Forster, P.; Spracklen, D. V.; Carslaw, K. S.; Arnold, S.; Rap, A.

    2012-12-01

    Vegetation emits biogenic volatile organic compounds (BVOCs), such as monoterpenes, isoprene and sesquiterpenes, into the atmosphere. Once emitted, BVOCs rapidly undergo reactions with the hydroxyl radical, ozone and the nitrate radical to yield a range of lower volatility oxidation products. These compounds are of sufficiently low volatility to partition into the aerosol phase, forming secondary organic aerosol (SOA). Increasingly, there are indications that organic compounds, specifically the oxidation products of terpenes, may contribute to the process of new particle formation as well as the growth of existing particles. The formation of SOA can influence the Earth's radiative balance by absorbing and scattering radiation (the direct effect) and by altering the properties of clouds (the indirect effect), via their action as cloud condensation nuclei (CCN). Biogenic SOA formed from the oxidation products of isoprene and monoterpenes has been shown to be CCN active under atmospherically relevant conditions, indicating that complex climate feedbacks may result from the emission of BVOCs. Using a global aerosol microphysics model (GLOMAP), and offline radiative transfer code, we simulate a present day aerosol indirect radiative forcing of between -0.07 and - 0.81 W.m-2, for the emission of BVOCs, due to a simulated increase in the number of particles able to act as CCN. The forcing obtained per emission is not spatially uniform, with monoterpenes in the southern hemisphere being most efficient at inducing a radiative change. We find a strong sensitivity to the treatment of concurrent anthropogenic emissions. In the present day, biogenic secondary organic material is more efficient at perturbing CCN number concentrations, but when anthropogenic emissions from 1750 are included in our simulations, the lower background aerosol concentration results in a more significant radiative response. The largest uncertainty in the forcing obtained however, comes from the

  2. Acoustic radiation force-based elasticity imaging methods

    PubMed Central

    Palmeri, Mark L.; Nightingale, Kathryn R.

    2011-01-01

    Conventional diagnostic ultrasound images portray differences in the acoustic properties of soft tissues, whereas ultrasound-based elasticity images portray differences in the elastic properties of soft tissues (i.e. stiffness, viscosity). The benefit of elasticity imaging lies in the fact that many soft tissues can share similar ultrasonic echogenicities, but may have different mechanical properties that can be used to clearly visualize normal anatomy and delineate pathological lesions. Acoustic radiation force-based elasticity imaging methods use acoustic radiation force to transiently deform soft tissues, and the dynamic displacement response of those tissues is measured ultrasonically and is used to estimate the tissue's mechanical properties. Both qualitative images and quantitative elasticity metrics can be reconstructed from these measured data, providing complimentary information to both diagnose and longitudinally monitor disease progression. Recently, acoustic radiation force-based elasticity imaging techniques have moved from the laboratory to the clinical setting, where clinicians are beginning to characterize tissue stiffness as a diagnostic metric, and commercial implementations of radiation force-based ultrasonic elasticity imaging are beginning to appear on the commercial market. This article provides an overview of acoustic radiation force-based elasticity imaging, including a review of the relevant soft tissue material properties, a review of radiation force-based methods that have been proposed for elasticity imaging, and a discussion of current research and commercial realizations of radiation force based-elasticity imaging technologies. PMID:22419986

  3. Simulated radiative forcing from contrails and contrail cirrus

    NASA Astrophysics Data System (ADS)

    Chen, C.-C.; Gettelman, A.

    2013-12-01

    A comprehensive general circulation model including ice supersaturation is used to estimate the climate impact of aviation induced contrails. The model uses a realistic aviation emissions inventory for 2006 to initiate contrails, and allows them to evolve consistently with the model hydrologic cycle. The radiative forcing from linear contrails is very sensitive to the diurnal cycle. For linear contrails, including the diurnal cycle of air traffic reduces the estimated radiative forcing by 29%, and for contrail cirrus estimates, the radiative forcing is reduced by 25%. Estimated global radiative forcing from linear contrails is 0.0031 ± 0.0005 Wm-2. The linear contrail radiative forcing is found to exhibit a strong diurnal cycle. The contrail cirrus radiative forcing is less sensitive to the diurnal cycle of flights. The estimated global radiative forcing from contrail cirrus is 0.013 ± 0.01 Wm-2. Over regions with the highest air traffic, the regional effect can be as large as 1 Wm-2.

  4. Unravelling the effects of radiation forces in water.

    PubMed

    Astrath, Nelson G C; Malacarne, Luis C; Baesso, Mauro L; Lukasievicz, Gustavo V B; Bialkowski, Stephen E

    2014-01-01

    The effect of radiation forces at the interface between dielectric materials has been a long-standing debate for over a century. Yet there has been so far only limited experimental verification in complete accordance with the theory. Here we measure the surface deformation at the air-water interface induced by continuous and pulsed laser excitation and match this to rigorous theory of radiation forces. We demonstrate that the experimental results are quantitatively described by the numerical calculations of radiation forces. The Helmholtz force is used for the surface radiation pressure. The resulting surface pressure obtained is consistent with the momentum conservation using the Minkowski momentum density expression assuming that the averaged momentum per photon is given by the Minkowski momentum. Considering the total momentum as a sum of that propagating with the electromagnetic wave and that deposited locally in the material, the Abraham momentum interpretation also appears to be appropriate. PMID:24999561

  5. Direct Aerosol Radiative Forcing: Calculations and Measurements from the Tropospheric

    NASA Technical Reports Server (NTRS)

    Russell, P. B.; Hignett, P.; Stowe, L. L.; Livingston, J. M.; Kinne, S.; Wong, J.; Chan, K. Roland (Technical Monitor)

    1997-01-01

    Radiative forcing is defined as the change in the net (downwelling minus upwelling) radiative flux at a given level in the atmosphere. This net flux is the radiative power density available to drive climatic processes in the earth-atmosphere system below that level. Recent research shows that radiative forcing by aerosol particles is a major source of uncertainty in climate predictions. To reduce those uncertainties, TARFOX was designed to determine direct (cloud-free) radiative forcing by the aerosols in one of the world's major industrial pollution plumes--that flowing from the east coast of the US over the Atlantic Ocean. TARFOX measured a variety of aerosol radiative effects (including direct forcing) while simultaneously measuring the chemical, physical, and optical properties of the aerosol particles causing those effects. The resulting data sets permit a wide variety of tests of the consistency, or closure, among the measurements and the models that link them. Because climate predictions use the same or similar model components, closure tests help to assess and reduce prediction uncertainties. In this work we use the TARFOX-determined aerosol, gas, and surface properties to compute radiative forcing for a variety of aerosol episodes, with inadvisable optical depths ranging from 0.07 to 0.6. We calculate forcing by several techniques with varying degrees of sophistication, in part to test the range of applicability of simplified techniques--which are often the only ones feasible in climate predictions by general circulation models (GCMs). We then compare computed forcing to that determined from: (1) Upwelling and downwelling fluxes (0.3-0.7 mm and 0.7-3.0 mm) measured by radiometers on the UK MRF C-130. and (2) Daily average cloud-free absorbed solar and emitted thermal radiative flux at the top of the atmosphere derived from the AVHRR radiometer on the NOAA- 14 satellite. The calculations and measurements all yield aerosol direct radiative forcing in the

  6. Cloud Radiative Forcing in the Tropics

    NASA Technical Reports Server (NTRS)

    Christopher, Sundar Anand

    1995-01-01

    Understanding the role of clouds is one of the highest priority science objectives in the global climate change program. In particular there has been a renewed interest in understanding the cloud radiative interactions in the tropical regions. Although a number of studies have emphasized the importance of cloud optical properties on the earth's radiative energy balance, information concerning cloud optical depth and particle size as a function of cloud type is lacking.

  7. Forcing the Issue on Radiation Policy

    SciTech Connect

    Rockwell, Theodore

    1999-06-06

    The recent case of a group of tobacco interests suing the U.S. Environmental Protection Agency (EPA) in Federal court on its policy on second-hand smoke has important implications for radiation policy. The issue was only tangentially about tobacco; its main thrust was at EPA's rule-making process.The EPA is at least as vulnerable to the same charges in the radiation area, particularly with respect to radon.

  8. Acoustic Radiation Force Impulse (ARFI) Imaging: a Review

    PubMed Central

    Nightingale, Kathy

    2012-01-01

    Acoustic radiation force based elasticity imaging methods are under investigation by many groups. These methods differ from traditional ultrasonic elasticity imaging methods in that they do not require compression of the transducer, and are thus expected to be less operator dependent. Methods have been developed that utilize impulsive (i.e. < 1 ms), harmonic (pulsed), and steady state radiation force excitations. The work discussed herein utilizes impulsive methods, for which two imaging approaches have been pursued: 1) monitoring the tissue response within the radiation force region of excitation (ROE) and generating images of relative differences in tissue stiffness (Acoustic Radiation Force Impulse (ARFI) imaging); and 2) monitoring the speed of shear wave propagation away from the ROE to quantify tissue stiffness (Shear Wave Elasticity Imaging (SWEI)). For these methods, a single ultrasound transducer on a commercial ultrasound system can be used to both generate acoustic radiation force in tissue, and to monitor the tissue displacement response. The response of tissue to this transient excitation is complicated and depends upon tissue geometry, radiation force field geometry, and tissue mechanical and acoustic properties. Higher shear wave speeds and smaller displacements are associated with stiffer tissues, and slower shear wave speeds and larger displacements occur with more compliant tissues. ARFI images have spatial resolution comparable to that of B-mode, often with greater contrast, providing matched, adjunctive information. SWEI images provide quantitative information about the tissue stiffness, typically with lower spatial resolution. A review these methods and examples of clinical applications are presented herein. PMID:22545033

  9. Radiative forcing from the 1991 Mount Pinatubo volcanic eruption

    NASA Astrophysics Data System (ADS)

    Stenchikov, Georgiy L.; Kirchner, Ingo; Robock, Alan; Graf, Hans-F.; AntuñA, Juan Carlos; Grainger, R. G.; Lambert, Alyn; Thomason, Larry

    1998-06-01

    Volcanic sulfate aerosols in the stratosphere produce significant long-term solar and infrared radiative perturbations in the Earth's atmosphere and at the surface, which cause a response of the climate system. Here we study the fundamental process of the development of this volcanic radiative forcing, focusing on the eruption of Mount Pinatubo in the Philippines on June 15, 1991. We develop a spectral-, space-, and time-dependent set of aerosol parameters for 2 years after the Pinatubo eruption using a combination of SAGE II aerosol extinctions and UARS-retrieved effective radii, supported by SAM II, AVHRR, lidar and balloon observations. Using these data, we calculate the aerosol radiative forcing with the ECHAM4 general circulation model (GCM) for cases with climatological and observed sea surface temperature (SST), as well as with and without climate response. We find that the aerosol radiative forcing is not sensitive to the climate variations caused by SST or the atmospheric response to the aerosols, except in regions with varying dense cloudiness. The solar forcing in the near infrared contributes substantially to the total stratospheric heating. A complete formulation of radiative forcing should include not only changes of net fluxes at the tropopause but also the vertical distribution of atmospheric heating rates and the change of downward thermal and net solar radiative fluxes at the surface. These forcing and aerosol data are available for GCM experiments with any spatial and spectral resolution.

  10. Simulated radiative forcing from contrails and contrail cirrus

    NASA Astrophysics Data System (ADS)

    Chen, C.-C.; Gettelman, A.

    2013-04-01

    A comprehensive general circulation model including ice supersaturation is used to estimate the climate impact of aviation induced contrails. The model uses a realistic aviation emissions inventory for 2006 to initiate contrails, and allows them to evolve consistently with the model hydrologic cycle. The radiative forcing from linear contrails is very sensitive to the diurnal cycle of flights. For linear contrails, including the diurnal cycle of flights reduces the estimated global radiative forcing by 55%, and for contrails cirrus estimates, the global radiative forcing is reduced by 25%. Estimated global radiative forcing from linear contrails is 0.0029±0.00125 W m-2. The instantaneous radiative forcing for contrails is found to exhibit a strong diurnal cycle. The integrated effect of contrail cirrus is much less sensitive to the diurnal cycle of flights. The estimated global radiative forcing from contrail cirrus is 0.012±0.01 W m-2. Over regions with the highest air traffic, the regional effect can be as large as 1 W m-2.

  11. 5 THE RADIATIVE FORCING DUE TO CLOUDS AND WATER VAPOR

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter utilizes results from the spaceborne Earth Radiation Budget Experiment (ERBE), launched in 1984 aboard the NOAA-9 (National Oceanic and Atmospheric Agency) satellite, to summarize our understanding of the radiative forcing due to water vapor and clouds. The effect of clouds on the rad...

  12. 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

  13. Cloud radiation forcings and feedbacks: General circulation model tests and observational validation

    SciTech Connect

    Lee, Wan-Ho; Iacobellis, S.F.; Somerville, R.C.J.

    1997-10-01

    Using an atmospheric general circulation model (the National Center for Atmospheric Research Community Climate Model: CCM2), the effects on climate sensitivity of several different cloud radiation parameterizations have been investigated. In addition to the original cloud radiation scheme of CCM2, four parameterizations incorporating prognostic cloud water were tested: one version with prescribed cloud radiative properties and three other versions with interactive cloud radiative properties. The authors` numerical experiments employ perpetual July integrations driven by globally constant sea surface temperature forcings of two degrees, both positive and negative. A diagnostic radiation calculation has been applied to investigate the partial contributions of high, middle, and low cloud to the total cloud radiative forcing, as well as the contributions of water vapor, temperature, and cloud to the net climate feedback. The high cloud net radiative forcing is positive, and the middle and low cloud net radiative forcings are negative. The total net cloud forcing is negative in all of the model versions. The effect of interactive cloud radiative properties on global climate sensitivity is significant. The net cloud radiative feedbacks consist of quite different shortwave and longwave components between the schemes with interactive cloud radiative properties and the schemes with specified properties. The increase in cloud water content in the warmer climate leads to optically thicker middle- and low-level clouds and in turn to negative shortwave feedbacks for the interactive radiative schemes, while the decrease in cloud amount simply produces a positive shortwave feedback for the schemes with a specified cloud water path. For the longwave feedbacks, the decrease in high effective cloudiness for the schemes without interactive radiative properties leads to a negative feedback, while for the other cases, the longwave feedback is positive. 29 refs., 18 figs., 6 tabs.

  14. Forcing the issue on radiation policy

    SciTech Connect

    Rockwell, T.

    1999-09-01

    For those frustrated by an inability to get a fair hearing on evidence that challenges current radiation policy, the recent case of a group of tobacco interests suing the US Environmental Protection Agency (EPA) in Federal court on its policy on second-hand smoke has important implications for radiation policy. The issue was only tangentially about tobacco; its main thrust was at EPA`s arbitrary and capricious rule-making process. The EPA is at least as vulnerable to the same charges in the radiation area, particularly with respect to radon. Radiation protection is associated in many people`s minds with the US Nuclear Regulatory Commission (NRC), but other agencies have also been involved. Radon, like second-hand smoke, has been tolerated for generations, and EPA has the burden of proving that it is a public hazard. The law and the unwritten rules of science are quite explicit in defining what must be done to make such a finding. In the case of radon, there is no prior basis for public concern. In fact, the public uses radium spas with radon concentrations up to one million times as high as the EPA permissible limit. In many countries, such spa usage is formally prescribed by physicians and paid for by national health insurance. The health effects, if any, from radon, as from second-hand smoke, are hard to quantify. But, this does not justify--in either case--the EPA`s straying from its published criteria and procedures for testing whether such health effects occur. A Federal court has now demonstrated its willingness to judge and strike down the EPA`s actions regarding second-hand smoke on their own merits, without attempting to be an arbiter of science. The result is a welcome breath of fresh air and an object lesson for those concerned about the mounting costs of treating radon as a major public health hazard.

  15. Radiation forces on small particles in the solar system

    NASA Technical Reports Server (NTRS)

    Burns, J. A.; Lamy, P. L.; Soter, S.

    1979-01-01

    Solar radiation forces on small particles in the solar system are examined, and the resulting orbital evolution of interplanetary and circumplanetary dust is considered. An expression is derived for the effects of radiation pressure and Poynting-Robertson drag on small, spherical particles using the energy and momentum transformation laws of special relativity, and numerical examples are presented to illustrate that radiation pressure and Poynting-Robertson drag are only important for particles within a narrow size range. The orbital consequences of these radiation forces are considered both for heliocentric and planetocentric orbiting particles, and the coupling between particle sizes and dynamics is discussed. A qualitative derivation is presented for the differential Doppler effect, which is due to the differential Doppler shifting of radiation from approaching and receding solar hemispheres, and the Yarkovsky effect, which is important for rotating meter-to kilometer-sized particles, is briefly described.

  16. The Potential Radiative Forcing of Global Land Use and Land Cover Change Activities

    NASA Astrophysics Data System (ADS)

    Ward, D. S.; Mahowald, N. M.; Kloster, S.

    2014-12-01

    Given the expected increase in pressure on land resources over the next century, there is a need to understand the total impacts of activities associated with land use and land cover change (LULCC). Here we quantify these impacts using the radiative forcing metric, including forcings from changes in long-lived greenhouse gases, tropospheric ozone, aerosol effects, and land surface albedo. We estimate radiative forcings from the different agents for historical LULCC and for six future projections using simulations from the National Center for Atmospheric Research Community Land Model and Community Atmosphere Models and additional offline analyses. When all forcing agents are considered together we show that 45% (+30%, -20%) of the present-day (2010) anthropogenic radiative forcing can be attributed to LULCC. Changes in the emission of non-CO2 greenhouse gases and aerosols from LULCC enhance the total LULCC radiative forcing by a factor of 2 to 3 with respect to the forcing from CO2 alone. In contrast, the non-CO2 forcings from fossil fuel burning are roughly neutral, due largely to the negative (cooling) impact of aerosols from these sources. We partition the global LULCC radiative forcing into three major sources: direct modification of land cover (e.g. deforestation), agricultural activities, and fire regime changes. Contributions from deforestation and agriculture are roughly equal in the present day, while changes to wildfire activity impose a small negative forcing globally. In 2100, deforestation activities comprise the majority of the LULCC radiative forcing for all projections except one (Representative Concentration Pathway (RCP) 4.5). This suggests that realistic scenarios of future forest area change are essential for projecting the contribution of LULCC to climate change. However, the commonly used RCP land cover change projections all include decreases in global deforestation rates over the next 85 years. To place an upper bound on the potential

  17. Annual Cycle of Cloud Forcing of Surface Radiation Budget

    NASA Technical Reports Server (NTRS)

    Wilber, Anne C.; Smith, G. Louis; Stackhouse, Paul W., Jr.; Gupta, Shashi K.

    2006-01-01

    The climate of the Earth is determined by its balance of radiation. The incoming and outgoing radiation fluxes are strongly modulated by clouds, which are not well understood. The Earth Radiation Budget Experiment (Barkstrom and Smith, 1986) provided data from which the effects of clouds on radiation at the top of the atmosphere (TOA) could be computed (Ramanathan, 1987). At TOA, clouds increase the reflected solar radiation, tending to cool the planet, and decrease the OLR, causing the planet to retain its heat (Ramanathan et al., 1989; Harrison et al., 1990). The effects of clouds on radiation fluxes are denoted cloud forcing. These shortwave and longwave forcings counter each other to various degrees, so that in the tropics the result is a near balance. Over mid and polar latitude oceans, cloud forcing at TOA results in large net loss of radiation. Here, there are large areas of stratus clouds and cloud systems associated with storms. These systems are sensitive to surface temperatures and vary strongly with the annual cycle. During winter, anticyclones form over the continents and move to the oceans during summer. This movement of major cloud systems causes large changes of surface radiation, which in turn drives the surface temperature and sensible and latent heat released to the atmosphere.

  18. Evaluation of aerosol indirect radiative forcing in MIRAGE

    NASA Astrophysics Data System (ADS)

    Ghan, Steven; Easter, Richard; Hudson, James; BréOn, Francois-Marie

    2001-03-01

    We evaluate aerosol indirect radiative forcing simulated by the Model for Integrated Research on Atmospheric Global Exchange (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. MIRAGE 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 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.

  20. CHARMM additive and polarizable force fields for biophysics and computer-aided drug design

    PubMed Central

    Vanommeslaeghe, K.

    2014-01-01

    Background Molecular Mechanics (MM) is the method of choice for computational studies of biomolecular systems owing to its modest computational cost, which makes it possible to routinely perform molecular dynamics (MD) simulations on chemical systems of biophysical and biomedical relevance. Scope of Review As one of the main factors limiting the accuracy of MD results is the empirical force field used, the present paper offers a review of recent developments in the CHARMM additive force field, one of the most popular bimolecular force fields. Additionally, we present a detailed discussion of the CHARMM Drude polarizable force field, anticipating a growth in the importance and utilization of polarizable force fields in the near future. Throughout the discussion emphasis is placed on the force fields’ parametrization philosophy and methodology. Major Conclusions Recent improvements in the CHARMM additive force field are mostly related to newly found weaknesses in the previous generation of additive force fields. Beyond the additive approximation is the newly available CHARMM Drude polarizable force field, which allows for MD simulations of up to 1 microsecond on proteins, DNA, lipids and carbohydrates. General Significance Addressing the limitations ensures the reliability of the new CHARMM36 additive force field for the types of calculations that are presently coming into routine computational reach while the availability of the Drude polarizable force fields offers a model that is an inherently more accurate model of the underlying physical forces driving macromolecular structures and dynamics. PMID:25149274

  1. Radiative forcing in the ACCMIP historical and future climate simulations

    NASA Astrophysics Data System (ADS)

    Shindell, D. T.; Lamarque, J.-F.; Schulz, M.; Flanner, M.; Jiao, C.; Chin, M.; Young, P.; Lee, Y. H.; Rotstayn, L.; Milly, G.; Faluvegi, G.; Balkanski, Y.; Collins, W. J.; Conley, A. J.; Dalsoren, S.; Easter, R.; Ghan, S.; Horowitz, L.; Liu, X.; Myhre, G.; Nagashima, T.; Naik, V.; Rumbold, S.; Skeie, R.; Sudo, K.; Szopa, S.; Takemura, T.; Voulgarakis, A.; Yoon, J.-H.

    2012-08-01

    A primary goal of the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) was to characterize the short-lived drivers of preindustrial to 2100 climate change in the current generation of climate models. Here we evaluate historical and future radiative forcing in the 10 ACCMIP models that included aerosols, 8 of which also participated in the Coupled Model Intercomparison Project phase 5 (CMIP5). The models generally reproduce present-day climatological total aerosol optical depth (AOD) relatively well. They have quite different contributions from various aerosol components to this total, however, and most appear to underestimate AOD over East Asia. The models generally capture 1980-2000 AOD trends fairly well, though they underpredict AOD increases over the Yellow/Eastern Sea. They appear to strongly underestimate absorbing AOD, especially in East Asia, South and Southeast Asia, South America and Southern Hemisphere Africa. We examined both the conventional direct radiative forcing at the tropopause (RF) and the forcing including rapid adjustments (adjusted forcing; AF, including direct and indirect effects). The models' calculated all aerosol all-sky 1850 to 2000 global mean annual average RF ranges from -0.06 to -0.49 W m-2, with a mean of -0.26 W m-2 and a median of -0.27 W m-2. Adjusting for missing aerosol components in some models brings the range to -0.12 to -0.62 W m-2, with a mean of -0.39 W m-2. Screening the models based on their ability to capture spatial patterns and magnitudes of AOD and AOD trends yields a quality-controlled mean of -0.42 W m-2 and range of -0.33 to -0.50 W m-2 (accounting for missing components). The CMIP5 subset of ACCMIP models spans -0.06 to -0.49 W m-2, suggesting some CMIP5 simulations likely have too little aerosol RF. A substantial, but not well quantified, contribution to historical aerosol RF may come from climate feedbacks (35 to -58 %). The mean aerosol AF during this period is -1.12 W m-2 (median

  2. Recent and future trends in synthetic greenhouse gas radiative forcing

    NASA Astrophysics Data System (ADS)

    Rigby, M.; Prinn, R. G.; O'Doherty, S.; Miller, B. R.; Ivy, D.; Mühle, J.; Harth, C. M.; Salameh, P. K.; Arnold, T.; Weiss, R. F.; Krummel, P. B.; Steele, L. P.; Fraser, P. J.; Young, D.; Simmonds, P. G.

    2014-04-01

    Atmospheric measurements show that emissions of hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons are now the primary drivers of the positive growth in synthetic greenhouse gas (SGHG) radiative forcing. We infer recent SGHG emissions and examine the impact of future emissions scenarios, with a particular focus on proposals to reduce HFC use under the Montreal Protocol. If these proposals are implemented, overall SGHG radiative forcing could peak at around 355 mW m-2 in 2020, before declining by approximately 26% by 2050, despite continued growth of fully fluorinated greenhouse gas emissions. Compared to "no HFC policy" projections, this amounts to a reduction in radiative forcing of between 50 and 240 mW m-2 by 2050 or a cumulative emissions saving equivalent to 0.5 to 2.8 years of CO2 emissions at current levels. However, more complete reporting of global HFC emissions is required, as less than half of global emissions are currently accounted for.

  3. Influence of urban aerosol pollution to radiative forcing

    NASA Astrophysics Data System (ADS)

    Nemuc, Anca; Stefan, Sabina; Talianu, Camelia L.

    2007-10-01

    Daily PM10 concentrations of samples collected at two sites, urban and rural from Romania have been used to estimate the aerosol direct radiative forcing. Using OPAC (Optical Properties of Aerosols and Cloud) model we determined the single scattering albedo, the aerosol optical depth and aerosol up-scatter fraction, aerosol's properties needed to estimate the magnitude and sign of direct aerosol radiative forcing. The surface albedo was assumed 0.2 for the urban site and 0.06 for the rural site for all wavelengths. For aerosol scale height we used 1km in winter and 2 km in the summer to calculate the optical depth of the boundary layer. Statistical analysis of the PM10 concentration for both sites show clear seasonal cycle with maxima in the winter. As a consequence of urban atmospheric pollution the radiative forcing for urban site appears strongly modified in comparison with rural site.

  4. Acoustic Radiation Force Elasticity Imaging in Diagnostic Ultrasound

    PubMed Central

    Doherty, Joshua R.; Trahey, Gregg E.; Nightingale, Kathryn R.; Palmeri, Mark L.

    2013-01-01

    The development of ultrasound-based elasticity imaging methods has been the focus of intense research activity since the mid-1990s. In characterizing the mechanical properties of soft tissues, these techniques image an entirely new subset of tissue properties that cannot be derived with conventional ultrasound techniques. Clinically, tissue elasticity is known to be associated with pathological condition and with the ability to image these features in vivo, elasticity imaging methods may prove to be invaluable tools for the diagnosis and/or monitoring of disease. This review focuses on ultrasound-based elasticity imaging methods that generate an acoustic radiation force to induce tissue displacements. These methods can be performed non-invasively during routine exams to provide either qualitative or quantitative metrics of tissue elasticity. A brief overview of soft tissue mechanics relevant to elasticity imaging is provided, including a derivation of acoustic radiation force, and an overview of the various acoustic radiation force elasticity imaging methods. PMID:23549529

  5. Tropospheric radiative forcing of CH{sub 4}

    SciTech Connect

    Grossman, A.S.; Grant, K.E.

    1994-04-01

    We have evaluated the tropospheric radiative forcing of CH{sub 4} in the 0-3000 cm{sup {minus}1} wavenumber range and compared this with prior published calculations. The atmospheric test cases involved perturbed methane scenarios in both a McClatchey mid latitude, summer, clear sky approximation, model atmosphere, as well as a globally and seasonally averaged model atmosphere containing a representative cloud distribution. The scenarios involved pure CH{sub 4} radiative forcing and CH{sub 4} plus a mixture of H{sub 2}O, CO{sub 2}, O{sub 3}, and N{sub 2}O. The IR radiative forcing was calculated using a correlated k-distribution transmission model. The major purposes of this paper are to first, use the correlated k-distribution model to calculate the tropospheric radiative forcing for CH{sub 4}, as the only radiatively active gas, and in a mixture with H{sub 2}O, CO{sub 2}, O{sub 3}, and N{sub 2}O, for a McClatchey mid-latitude summer, clear-sky model atmosphere, and to compare the results to those obtained in the studies mentioned above. Second, we will calculate the tropospheric methane forcing in a globally and annually averaged atmosphere with and without a representative cloud distribution in order to validate the conjecture given in IPCC (1990) that the inclusion of clouds in the forcing calculations results in forcing values which are approximately 20 percent less than those obtained using clear sky approximations.

  6. Radiation forces between dust grains in a plasma

    NASA Astrophysics Data System (ADS)

    Mendonça, J. T.; Stenflo, L.

    2008-04-01

    In this work we show that a repulsive force between nearby dust grains in a plasma can exist, due to scattering of the incident radiation. Two types of forces are discussed, one of them being formally identical to electrostatic repulsion. This leads to the definition of an effective dust charge of the dust grain, which only depends on the scattering process. Our discussion shows that such a repulsive interaction occurs in quite general physical conditions.

  7. Modulation of ultrasound to produce multifrequency radiation force1

    PubMed Central

    Urban, Matthew W.; Fatemi, Mostafa; Greenleaf, James F.

    2010-01-01

    Dynamic radiation force has been used in several types of applications, and is performed by modulating ultrasound with different methods. By modulating ultrasound, energy can be transmitted to tissue, in this case a dynamic force to elicit a low frequency cyclic displacement to inspect the material properties of the tissue. In this paper, different types of modulation are explored including amplitude modulation (AM), double sideband suppressed carrier amplitude modulation AM, linear frequency modulation, and frequency-shift keying. Generalized theory is presented for computing the radiation force through the short-term time average of the energy density for these various types of modulation. Examples of modulation with different types of signals including sine waves, square waves, and triangle waves are shown. Using different modulating signals, multifrequency radiation force with different numbers of frequency components can be created, and can be used to characterize tissue mimicking materials and soft tissue. Results for characterization of gelatin phantoms using a method of vibrating an embedded sphere are presented. Different degrees of accuracy were achieved using different modulation techniques and modulating signals. Modulating ultrasound is a very flexible technique to produce radiation force with multiple frequency components that can be used for various applications. PMID:20329821

  8. Dynamic Response of Model Lipid Membranes to Ultrasonic Radiation Force

    PubMed Central

    Prieto, Martin Loynaz; Oralkan, Ömer; Khuri-Yakub, Butrus T.; Maduke, Merritt C.

    2013-01-01

    Low-intensity ultrasound can modulate action potential firing in neurons in vitro and in vivo. It has been suggested that this effect is mediated by mechanical interactions of ultrasound with neural cell membranes. We investigated whether these proposed interactions could be reproduced for further study in a synthetic lipid bilayer system. We measured the response of protein-free model membranes to low-intensity ultrasound using electrophysiology and laser Doppler vibrometry. We find that ultrasonic radiation force causes oscillation and displacement of lipid membranes, resulting in small (<1%) changes in membrane area and capacitance. Under voltage-clamp, the changes in capacitance manifest as capacitive currents with an exponentially decaying sinusoidal time course. The membrane oscillation can be modeled as a fluid dynamic response to a step change in pressure caused by ultrasonic radiation force, which disrupts the balance of forces between bilayer tension and hydrostatic pressure. We also investigated the origin of the radiation force acting on the bilayer. Part of the radiation force results from the reflection of the ultrasound from the solution/air interface above the bilayer (an effect that is specific to our experimental configuration) but part appears to reflect a direct interaction of ultrasound with the bilayer, related to either acoustic streaming or scattering of sound by the bilayer. Based on these results, we conclude that synthetic lipid bilayers can be used to study the effects of ultrasound on cell membranes and membrane proteins. PMID:24194863

  9. Accurate Satellite-Derived Estimates of Tropospheric Ozone Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Joiner, Joanna; Schoeberl, Mark R.; Vasilkov, Alexander P.; Oreopoulos, Lazaros; Platnick, Steven; Livesey, Nathaniel J.; Levelt, Pieternel F.

    2008-01-01

    Estimates of the radiative forcing due to anthropogenically-produced tropospheric O3 are derived primarily from models. Here, we use tropospheric ozone and cloud data from several instruments in the A-train constellation of satellites as well as information from the GEOS-5 Data Assimilation System to accurately estimate the instantaneous radiative forcing from tropospheric O3 for January and July 2005. We improve upon previous estimates of tropospheric ozone mixing ratios from a residual approach using the NASA Earth Observing System (EOS) Aura Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) by incorporating cloud pressure information from OMI. Since we cannot distinguish between natural and anthropogenic sources with the satellite data, our estimates reflect the total forcing due to tropospheric O3. We focus specifically on the magnitude and spatial structure of the cloud effect on both the shortand long-wave radiative forcing. The estimates presented here can be used to validate present day O3 radiative forcing produced by models.

  10. Fully covariant radiation force on a polarizable particle

    NASA Astrophysics Data System (ADS)

    Pieplow, Gregor; Henkel, Carsten

    2013-02-01

    The electromagnetic force on a polarizable particle is calculated in a covariant framework. Local equilibrium temperatures for the electromagnetic field and the particle's dipole moment are assumed, using a relativistic formulation of the fluctuation-dissipation theorem. Two examples illustrate radiative friction forces: a particle moving through a homogeneous radiation background and above a planar interface. Previous results for arbitrary relative velocities are recovered in a compact way. The authors acknowledge the use of the Legacy Archive for Microwave Background Data Analysis (LAMBDA) in the video abstract. Support for LAMBDA is provided by the NASA Office of Space Science.

  11. TRADEOFFs in climate effects through aircraft routing: forcing due to radiatively active gases

    NASA Astrophysics Data System (ADS)

    Stordal, F.; Gauss, M.; Myhre, G.; Mancini, E.; Hauglustaine, D. A.; Köhler, M. O.; Berntsen, T.; . G Stordal, E. J.; Iachetti, D.; Pitari, G.; Isaksen, I. S. A.

    2006-10-01

    We have estimated impacts of alternative aviation routings on the radiative forcing. Changes in ozone and OH have been estimated in four Chemistry Transport Models (CTMs) participating in the TRADEOFF project. Radiative forcings due to ozone and methane have been calculated accordingly. In addition radiative forcing due to CO2 is estimated based on fuel consumption. Three alternative routing cases are investigated; one scenario assuming additional polar routes and two scenarios assuming aircraft cruising at higher (+2000 ft) and lower (-6000 ft) altitudes. Results from the base case in year 2000 are included as a reference. Taking first a steady state backward looking approach, adding the changes in the forcing from ozone, CO2 and CH4, the ranges of the models used in this work are -0.8 to -1.8 and 0.3 to 0.6 m Wm-2 in the lower (-6000 ft) and higher (+2000 ft) cruise levels, respectively. In relative terms, flying 6000ft lower reduces the forcing by 5-10% compared to the current flight pattern, whereas flying higher, while saving fuel and presumably flying time, increases the forcing by about 2-3%. Taking next a forward looking approach we have estimated the integrated forcing (m Wm-2 yr) over 20 and 100 years time horizons. The relative contributions from each of the three climate gases are somewhat different from the backward looking approach. The differences are moderate adopting 100 year time horizon, whereas under the 20 year horizon CO2 naturally becomes less important relatively. Thus the forcing agents impact climate differently on various time scales. Also, we have found significant differences between the models for ozone and methane. We conclude that we are not yet at a point where we can include non-CO2 effects of aviation in emission trading schemes. Nevertheless, the rerouting cases that have been studied here yield relatively small changes in the radiative forcing due to the radiatively active gases.

  12. A study of the acoustical radiation force considering attenuation

    NASA Astrophysics Data System (ADS)

    Wu, RongRong; Liu, XiaoZhou; Gong, XiuFen

    2013-07-01

    Acoustical tweezer is a primary application of the radiation force of a sound field. When an ultrasound focused beam passes through a micro-particle, like a cell or living biological specimens, the particle will be manipulated accurately without physical contact and invasion, due to the three-dimensional acoustical trapping force. Based on the Ray acoustics approach in the Mie regime, this work discusses the effects on the particle caused by Gaussian focused ultrasound, studies the acoustical trapping force of spherical Mie particles by ultrasound in any position, and analyzes the numerical calculation on the two-dimensional acoustical radiation force. This article also analyzes the conditions for the acoustical trapping phenomenon, and discusses the impact of the initial position and size of the particle on the magnitude of the acoustical radiation force. Furthermore, this paper considers the ultrasonic attenuation in a particle in the case of two-dimension, studies the attenuation's effects on the acoustical trapping force, and amends the calculation to the ordinary case with attenuation.

  13. Large radiative forcing efficiency of atmospheric aerosols over the Himalaya

    NASA Astrophysics Data System (ADS)

    Gasbarra, Daniele; di Sarra, Alcide; Meloni, Daniela; Bonasoni, Paolo; Di Biagio, Claudia; Gobbi, Gian Paolo; Marinoni, Angela; Pietro Verza, Gian; Vuillermoz, Elisa

    2014-05-01

    This study is based on measurements made at the Nepal Climate Observatory at Pyramid (NCO-P, 27.95 N, 86.82 E), located at 5079 m altitude in the Sagamartha National Park, Eastern Nepal Himalaya. We analised seasonal variations of solar downward irradiance (SW), columnar water vapour content (wv), aerosol optical depth at 500 nm (τ) and surface albedo (A) in the period between 2007 and 2010, in order to obtain the radiative perturbations produced by aerosols in the SW. SW measurements are carried out by a CMP21 pyranometer, while A is derived from a CNR1 radiometer. Values of wv and τ are retrieved from the measurements by the EVK2-CNR Cimel sunphotometer operating within the AERONET network. τ was found to be lower than 0.1 in 98% of the cases. However, during the pre-monsoon season, especially in the months of April and May, cases with τ reaching 0.27 were recorded. The aerosol surface shortwave radiative effect in cloud-free periods was estimated during the elevated aerosol optical depth cases using different methods. The 'hybrid method' was applied using experimental measurements of solar downward irradiance and simulations made with the MODTRAN (MODerate resolution atmospheric TRANsmission) model. The dependency of SW on A and wv was determined from MODTRAN simulations, and was used to correct experimental measurements for albedo and water vapour changes. The radiative perturbation produced by aerosol was thus obtained as the difference between the measured irradiances and the modelled values for aerosol-free conditions and the same water vapour and albedo values, and at the same solar zenith angle. The aerosol radiative effect was also derived by comparing elevated and low aerosol optical depth cases, at similar values of solar zenith angle, albedo, and column water vapour. In addition the direct method, relating SW to changes in τ, was also used. These three methods produce consistent results. Although the overall aerosol radiative perturbation is small

  14. Regional Attribution of Ozone Production and Associated Radiative Forcing: a Step to Crediting NOx Emission Reductions

    NASA Astrophysics Data System (ADS)

    Naik, V.; Mauzerall, D. L.; Horowitz, L.; Schwarzkopf, D.; Ramaswamy, V.; Oppenheimer, M.

    2004-12-01

    The global distribution of tropospheric ozone (O3) depends on the location of emissions of its precursors in addition to chemical and dynamical factors. The global picture of O3 forcing is, therefore, a sum of regional forcings arising from emissions of precursors from different sources. The Kyoto Protocol does not include ozone as a greenhouse gas, and emission reductions of ozone precursors made under Kyoto or any similar agreement would presently receive no credit. In this study, we quantitatively estimate the contribution of emissions of nitrogen oxides (NOx), the primary limiting O3 precursor in the non-urban atmosphere, from specific countries and regions of the world to global O3 concentration distributions. We then estimate radiative forcing resulting from the regional perturbations of NOx emissions. This analysis is intended as an early step towards incorporating O3 into the Kyoto Protocol or any successor agreement. Under such a system countries could obtain credit for improvements in local air quality that result in reductions of O3 concentrations because of the associated reductions in radiative forcing. We use the global chemistry transport model, MOZART-2, to simulate the global O3 distribution for base year 1990 and perturbations to this distribution caused by a 10% percent reduction in the base emissions of NOx from the United States, Europe, East Asia, India, South America, and Africa. We calculate the radiative forcing for the simulated base and perturbed O3 distributions using the GFDL radiative transfer model. The difference between the radiative forcing from O3 for the base and perturbed distributions provides an estimate of the marginal radiative forcing from a region's emissions of NOx. We will present a quantitative analysis of the magnitude, spatial, and temporal distribution of radiative forcing resulting from marginal changes in the NOx emissions from each region.

  15. High Resolution Aerosol Modeling: Decadal Changes in Radiative Forcing

    SciTech Connect

    Bergmann, D J; Chuang, C C; Govindasamy, B; Cameron-Smith, P J; Rotman, D A

    2005-02-01

    The Atmospheric Science Division of LLNL has performed high-resolution calculations of direct sulfate forcing using a DOE-provided computer resource at NERSC. We integrated our global chemistry-aerosol model (IMPACT) with the LLNL high-resolution global climate model (horizontal resolution as high as 100 km) to examine the temporal evolution of sulfate forcing since 1950. We note that all previous assessments of sulfate forcing reported in IPCC (2001) were based on global models with coarse spatial resolutions ({approx} 300 km or even coarser). However, the short lifetime of aerosols ({approx} days) results in large spatial and temporal variations of radiative forcing by sulfate. As a result, global climate models with coarse resolutions do not accurately simulate sulfate forcing on regional scales. It requires much finer spatial resolutions in order to address the effects of regional anthropogenic SO{sub 2} emissions on the global atmosphere as well as the effects of long-range transport of sulfate aerosols on the regional climate forcing. By taking advantage of the tera-scale computer resources at NERSC, we simulated the historic direct sulfate forcing at much finer spatial resolutions than ever attempted before. Furthermore, we performed high-resolution chemistry simulations and saved monthly averaged oxidant fields, which will be used in subsequent simulations of sulfate aerosol formation and their radiative impact.

  16. Black carbon radiative forcing over the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    He, Cenlin; Li, Qinbin; Liou, Kuo-Nan; Takano, Yoshi; Gu, Yu; Qi, Ling; Mao, Yuhao; Leung, L. Ruby

    2014-11-01

    We estimate the snow albedo forcing and direct radiative forcing (DRF) of black carbon (BC) in the Tibetan Plateau using a global chemical transport model in conjunction with a stochastic snow model and a radiative transfer model. The annual mean BC snow albedo forcing is 2.9 W m-2 averaged over snow-covered plateau regions, which is a factor of 3 larger than the value over global land snowpack. BC-snow internal mixing increases the albedo forcing by 40-60% compared with external mixing, and coated BC increases the forcing by 30-50% compared with uncoated BC aggregates, whereas Koch snowflakes reduce the forcing by 20-40% relative to spherical snow grains. The annual BC DRF at the top of the atmosphere is 2.3 W m-2 with uncertainties of -70-85% in the plateau after scaling the modeled BC absorption optical depth to Aerosol Robotic Network observations. The BC forcings are attributed to emissions from different regions.

  17. Black Carbon Radiative Forcing over the Tibetan Plateau

    SciTech Connect

    He, Cenlin; Li, Qinbin; Liou, K. N.; Takano, Y.; Gu, Yu; Qi, L.; Mao, Yuhao; Leung, Lai-Yung R.

    2014-11-28

    We estimate the snow albedo forcing and direct radiative forcing (DRF) of black carbon (BC) in the Tibetan Plateau using a global chemical transport model in conjunction with a stochastic snow model and a radiative transfer model. Our best estimate of the annual BC snow albedo forcing in the Plateau is 2.9 W m-2 (uncertainty: 1.5–5.0 W m-226 ). We find that BC-snow internal mixing increases the albedo forcing by 40-60% compared with external mixing and coated BC increases the forcing by 30-50% compared with uncoated BC, whereas Koch snowflakes reduce the forcing by 20-40% relative to spherical snow grains. Our best estimate of the annual BC DRF at the top of the atmosphere is 2.3 W m-2 (uncertainty: 0.7–4.3 W m-230 ) in the Plateau after scaling the modeled BC absorption optical depth to Aerosol Robotic Network (AERONET) observations. The BC forcings are attributed to emissions from different regions.

  18. Long-wave radiative forcing due to mineral dust aerosol

    NASA Astrophysics Data System (ADS)

    Gunn, L. N.; Collins, W.

    2010-12-01

    Radiative forcing due to aerosols has been identified by the IPCC as a major contributor to the total radiative forcing uncertainty budget. Optically thick plumes of dust and pollutants extending out from Africa and Asia can be lifted into the middle troposphere and often are transported over synoptic length scales. These events can decrease the upwelling long-wave fluxes at the top of the atmosphere, especially in the mid-infrared "window". Typically these effects have not been included in model simulations and the spectrally integrated effects of aerosols on the planetary long-wave energy budget have not employed satellite data to produce systematic global estimates. In this study we will show initial results for the quantitative determination of a global radiative forcing due to mineral dust calculated using A-train satellite instrument measurements from AIRS, TES, and MODIS. The initial results focus on localized dust outbreaks, over Australia, Africa and Asia, and describe the methods that will be implemented for the determination of a quantitative global radiative forcing estimate.

  19. Experimental Characterization of Radiation Forcing due to Atmospheric Aerosols

    NASA Astrophysics Data System (ADS)

    Sreenivas, K. R.; Singh, D. K.; Ponnulakshmi, V. K.; Subramanian, G.

    2011-11-01

    Micro-meteorological processes in the nocturnal atmospheric boundary layer (NBL) including the formation of radiation-fog and the development of inversion layers are controlled by heat transfer and the vertical temperature distribution close to the ground. In a recent study, it has been shown that the temperature profile close to the ground in stably-stratified, NBL is controlled by the radiative forcing due to suspended aerosols. Estimating aerosol forcing is also important in geo-engineering applications to evaluate the use of aerosols to mitigate greenhouse effects. Modeling capability in the above scenarios is limited by our knowledge of this forcing. Here, the design of an experimental setup is presented which can be used for evaluating the IR-radiation forcing on aerosols under either Rayleigh-Benard condition or under conditions corresponding to the NBL. We present results indicating the effect of surface emissivities of the top and bottom boundaries and the aerosol concentration on the temperature profiles. In order to understand the observed enhancement of the convection-threshold, we have determined the conduction-radiation time constant of an aerosol laden air layer. Our results help to explain observed temperature profiles in the NBL, the apparent stability of such profiles and indicate the need to account for the effect of aerosols in climatic/weather models.

  20. LAGEOS Solar Radiation Force: Contribution from Cube-Corner Retroreflection

    NASA Astrophysics Data System (ADS)

    Slabinski, Victor J.

    2016-05-01

    The surface of a spherical LAGEOS satellite contains 426 Cube Corner Reflectors (CCRs) for the retro-reflection of incident laser ranging beams back to their source. For practical reasons, the number of CCRs is finite, so their distribution over the surface is not perfectly uniform.At any time, the ~9 CCRs near the sub-solar point on the LAGEOS surface will also retroreflect incident sunlight back toward the Sun. This concentration of reflected sunlight into a parallel beam increases the resulting radiation force on the satellite over what occurs for the usual broad-beam specular and diffuse reflection by ordinary surfaces. Because of the non-uniform CCR distribution, the retroreflection of sunlight (and hence the solar radiation force on the satellite) varies with the Sun aspect angle, even when averaged over the spin period. The Sun aspect angle is the co-latitude of the sub-solar surface point measured from the spin pole.We use ray tracing of sunlight through the CCRs to determine the Sun angle dependence of the solar radiation force and the resulting variation in secular perturbation rates for the LAGEOS orbit, especially for the eccentricity elements. We investigate the possibility of using the observed variations in the eccentricity vector as a check on the spacecraft spin-axis attitude. Attitude information is important for computing radiation-force perturbations to the orbit node when determining the Lense-Thirring effect.

  1. On the contribution of circumferential resonance modes in acoustic radiation force experienced by cylindrical shells

    NASA Astrophysics Data System (ADS)

    Rajabi, Majid; Behzad, Mehdi

    2014-10-01

    A body insonified by a constant (time-varying) intensity sound field is known to experience a steady (oscillatory) force that is called the steady-state (dynamic) acoustic radiation force. Using the classical resonance scattering theorem (RST) which suggests the scattered field as a superposition of a resonance field and a background (non-resonance) component, we show that the radiation force acting on a cylindrical shell may be synthesized as a composition of three components: background part, resonance part and their interaction. The background component reveals the pure geometrical reflection effects and illustrates a regular behavior with respect to frequency, while the others demonstrate a singular behavior near the resonance frequencies. The results illustrate that the resonance effects associated to partial waves can be isolated by the subtraction of the background component from the total (steady-state or dynamic) radiation force function (i.e., residue component). In the case of steady-state radiation force, the components are exerted on the body as static forces. For the case of oscillatory amplitude excitation, the components are exerted at the modulation frequency with frequency-dependant phase shifts. The results demonstrate the dominant contribution of the non-resonance component of dynamic radiation force at high frequencies with respect to the residue component, which offers the potential application of ultrasound stimulated vibro-acoustic spectroscopy technique in low frequency resonance spectroscopy purposes. Furthermore, the proposed formulation may be useful essentially due to its intrinsic value in physical acoustics. In addition, it may unveil the contribution of resonance modes in the dynamic radiation force experienced by the cylindrical objects and its underlying physics.

  2. Pairwise-additive force fields for selected aqueous monovalent ions from adaptive force matching

    NASA Astrophysics Data System (ADS)

    Li, Jicun; Wang, Feng

    2015-11-01

    Simple non-polarizable potentials were developed for Na+, K+, Cl-, and Br- using the adaptive force matching (AFM) method with ab initio MP2 method as reference. Our MP2-AFM force field predicts the solvation free energies of the four salts formed by the ions with an error of no more than 5%. Other properties such as the ion-water radial distribution functions, first solvation shell water tilt angle distributions, ion diffusion constants, concentration dependent diffusion constant of water, and concentration dependent surface tension of the solutions were calculated with this potential. Very good agreement was achieved for these properties. In particular, the diffusion constants of the ions are within 6% of experimental measurements. The model predicts bromide to be enriched at the interface in the 1.6M KBr solution but predicts the ion to be repelled for the surface at lower concentration.

  3. Modeling radiation forces acting on satellites for precision orbit determination

    NASA Technical Reports Server (NTRS)

    Marshall, J. A.; Antreasian, P. G.; Rosborough, G. W.; Putney, B. H.

    1992-01-01

    Models of the TOPEX/Poseidon spacecraft are developed by means of finite-element analyses for use in generating acceleration histories for various orbit orientations which account for nonconservative radiation forces. The acceleration profiles are developed with an analysis based on the use of the 'box-wing' model in which the satellite is modeled as a combination of flat plates. The models account for the effects of solar, earth-albedo, earth-IR, and spacecraft-thermal radiation. The finite-element analysis gives the total force and induced accelerations acting on the satellite. The plate types used in the analysis have parameters that can be adjusted to optimize model performance according to the micromodel analysis and tracking observations. Acceleration related to solar radiation pressure is modeled effectively, and the techniques are shown to be useful for the precise orbit determinations required for spacecraft such as the TOPEX/Poseidon.

  4. Response of air stagnation frequency to anthropogenically enhanced radiative forcing.

    PubMed

    Horton, Daniel E; Harshvardhan; Diffenbaugh, Noah S

    2012-01-01

    Stagnant atmospheric conditions can lead to hazardous air quality by allowing ozone and particulate matter to accumulate and persist in the near-surface environment. By changing atmospheric circulation and precipitation patterns, global warming could alter the meteorological factors that regulate air stagnation frequency. We analyze the response of the National Climatic Data Center (NCDC) Air Stagnation Index (ASI) to anthropogenically enhanced radiative forcing using global climate model projections of late-21(st) century climate change (SRES A1B scenario). Our results indicate that the atmospheric conditions over the highly populated, highly industrialized regions of the eastern United States, Mediterranean Europe, and eastern China are particularly sensitive to global warming, with the occurrence of stagnant conditions projected to increase 12-to-25% relative to late-20(th) century stagnation frequencies (3-18+ days/year). Changes in the position/strength of the polar jet, in the occurrence of light surface winds, and in the number of precipitation-free days all contribute to more frequent late-21(st) century air mass stagnation over these high-population regions. In addition, we find substantial inter-model spread in the simulated response of stagnation conditions over some regions using either native or bias corrected global climate model simulations, suggesting that changes in the atmospheric circulation and/or the distribution of precipitation represent important sources of uncertainty in the response of air quality to global warming. PMID:23284587

  5. Cloud Radiation Forcings and Feedbacks: General Circulation Model Tests and Observational Validation

    NASA Technical Reports Server (NTRS)

    Lee,Wan-Ho; Iacobellis, Sam F.; Somerville, Richard C. J.

    1997-01-01

    Using an atmospheric general circulation model (the National Center for Atmospheric Research Community Climate Model: CCM2), the effects on climate sensitivity of several different cloud radiation parameterizations have been investigated. In addition to the original cloud radiation scheme of CCM2, four parameterizations incorporating prognostic cloud water were tested: one version with prescribed cloud radiative properties and three other versions with interactive cloud radiative properties. The authors' numerical experiments employ perpetual July integrations driven by globally constant sea surface temperature forcings of two degrees, both positive and negative. A diagnostic radiation calculation has been applied to investigate the partial contributions of high, middle, and low cloud to the total cloud radiative forcing, as well as the contributions of water vapor, temperature, and cloud to the net climate feedback. The high cloud net radiative forcing is positive, and the middle and low cloud net radiative forcings are negative. The total net cloud forcing is negative in all of the model versions. The effect of interactive cloud radiative properties on global climate sensitivity is significant. The net cloud radiative feedbacks consist of quite different shortwave and longwave components between the schemes with interactive cloud radiative properties and the schemes with specified properties. The increase in cloud water content in the warmer climate leads to optically thicker middle- and low-level clouds and in turn to negative shortwave feedbacks for the interactive radiative schemes, while the decrease in cloud amount simply produces a positive shortwave feedback for the schemes with a specified cloud water path. For the longwave feedbacks, the decrease in high effective cloudiness for the schemes without interactive radiative properties leads to a negative feedback, while for the other cases, the longwave feedback is positive. These cloud radiation

  6. Material properties from acoustic radiation force step response

    PubMed Central

    Orescanin, Marko; Toohey, Kathleen S.; Insana, Michael F.

    2009-01-01

    An ultrasonic technique for estimating viscoelastic properties of hydrogels, including engineered biological tissues, is being developed. An acoustic radiation force is applied to deform the gel locally while Doppler pulses track the induced movement. The system efficiently couples radiation force to the medium through an embedded scattering sphere. A single-element, spherically-focused, circular piston element transmits a continuous-wave burst to suddenly apply and remove a radiation force to the sphere. Simultaneously, a linear array and spectral Doppler technique are applied to track the position of the sphere over time. The complex shear modulus of the gel was estimated by applying a harmonic oscillator model to measurements of time-varying sphere displacement. Assuming that the stress-strain response of the surrounding gel is linear, this model yields an impulse response function for the gel system that may be used to estimate material properties for other load functions. The method is designed to explore the force-frequency landscape of cell-matrix viscoelasticity. Reported measurements of the shear modulus of gelatin gels at two concentrations are in close agreement with independent rheometer measurements of the same gels. Accurate modulus measurements require that the rate of Doppler-pulse transmission be matched to a priori estimates of gel properties. PMID:19425636

  7. Net radiative forcing from widespread deployment of photovoltaics.

    PubMed

    Nemet, Gregory F

    2009-03-15

    If photovoltaics (PV) are to contribute significantly to stabilizing the climate, they will need to be deployed on the scale of multiple terawatts. Installation of that much PV would cover substantial portions of the Earth's surface with dark-colored, sunlight-absorbing panels, reducing the Earth's albedo. How much radiative forcing would result from this change in land use? How does this amount compare to the radiative forcing avoided by substituting PV for fossil fuels? This analysis uses a series of simple equations to compare the two effects and finds that substitution dominates; the avoided radiative forcing due to substitution of PV for fossil fuels is approximately 30 times largerthan the forcing due to albedo modification. Sensitivity analysis, including discounting of future costs and benefits, identifies unfavorable yet plausible configurations in which the albedo effect substantially reduces the climatic benefits of PV. The value of PV as a climate mitigation option depends on how it is deployed, not just how much it is deployed--efficiency of PV systems and the carbon intensity of the substituted energy are particularly important PMID:19368231

  8. Axial acoustic radiation force on a sphere in Gaussian field

    SciTech Connect

    Wu, Rongrong; Liu, Xiaozhou Gong, Xiufen

    2015-10-28

    Based on the finite series method, the acoustical radiation force resulting from a Gaussian beam incident on a spherical object is investigated analytically. When the position of the particles deviating from the center of the beam, the Gaussian beam is expanded as a spherical function at the center of the particles and the expanded coefficients of the Gaussian beam is calculated. The analytical expression of the acoustic radiation force on spherical particles deviating from the Gaussian beam center is deduced. The acoustic radiation force affected by the acoustic frequency and the offset distance from the Gaussian beam center is investigated. Results have been presented for Gaussian beams with different wavelengths and it has been shown that the interaction of a Gaussian beam with a sphere can result in attractive axial force under specific operational conditions. Results indicate the capability of manipulating and separating spherical spheres based on their mechanical and acoustical properties, the results provided here may provide a theoretical basis for development of single-beam acoustical tweezers.

  9. Radiative Forcing and Balance of the World's Wetlands

    NASA Astrophysics Data System (ADS)

    Bridgham, S. D.; Megonigal, P.

    2014-12-01

    Wetlands have been important in their radiative forcing effect on the Earth's past glacial-interglacial cycles, and evidence suggests that recent interannual variations in atmospheric methane concentrations are driven partly by climatic effects on wetland methane emissions. Methane emissions from wetlands are offset by their substantial ability to sequester carbon. We use best estimates from the literature to construct a radiative mass balance for trace gas emissions and soil carbon sequestration from the world's wetlands. We also distinguish between the static radiative balance of wetlands and their radiative forcing, with only the latter affecting climate. Large uncertainties in our estimates are particularly due to uncertainties in historical and current wetland area and soil sequestration rates in mineral-soil wetlands. Overall, we conclude that destruction of mineral-soil wetlands has likely had a global cooling effect (and vice-versa for restoration), whereas destruction of peatlands and marine-associated wetlands has had a warming effect using a 100 year global warming potential. We also emphasize the myriad goods and services that wetlands provide besides their effects on climate forcing.

  10. 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.

  11. Radiation reaction as a non-conservative force

    NASA Astrophysics Data System (ADS)

    Aashish, Sandeep; Haque, Asrarul

    2016-09-01

    We study a system of a finite size charged particle interacting with a radiation field by exploiting Hamilton’s principle for a non-conservative system recently introduced by Galley [1]. This formulation leads to the equation of motion of the charged particle that turns out to be the same as that obtained by Jackson [2]. We show that the radiation reaction stems from the non-conservative part of the effective action for a charged particle. We notice that a charge interacting with a radiation field modeled as a heat bath affords a way to justify that the radiation reaction is a non-conservative force. The topic is suitable for graduate courses on advanced electrodynamics and classical theory of fields.

  12. Deformation of red blood cells using acoustic radiation forces

    PubMed Central

    Mishra, Puja; Hill, Martyn; Glynne-Jones, Peter

    2014-01-01

    Acoustic radiation forces have been used to manipulate cells and bacteria in a number of recent microfluidic applications. The net force on a cell has been subject to careful investigation over a number of decades. We demonstrate that the radiation forces also act to deform cells. An ultrasonic standing wave field is created in a 0.1 mm glass capillary at a frequency of 7.9 MHz. Using osmotically swollen red-blood cells, we show observable deformations up to an aspect ratio of 1.35, comparable to deformations created by optical tweezing. In contrast to optical technologies, ultrasonic devices are potentially capable of deforming thousands of cells simultaneously. We create a finite element model that includes both the acoustic environment of the cell, and a model of the cell membrane subject to forces resulting from the non-linear aspects of the acoustic field. The model is found to give reasonable agreement with the experimental results, and shows that the deformation is the result of variation in an acoustic force that is directed outwards at all points on the cell membrane. We foresee applications in diagnostic devices, and in the possibility of mechanically stimulating cells to promote differentiation and physiological effects. PMID:25379070

  13. 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

  14. Lorentz force and radiation pressure on a spherical cloak

    SciTech Connect

    Chen Hongsheng; Wu, B.-I.; Zhang Baile; Luo Yu; Zhang Jingjing; Ran Lixin; Kemp, Brandon A.

    2009-07-15

    The mechanical behavior of a transformation based spherical cloak under wave illumination is derived. We show that the equatorial region of the cloak is subject to much higher stress than the polar regions, where the polar axis is defined along the wave propagation direction. These forces do not exist before transformation but stem from the squeezed electromagnetic space. The trajectory of the ray can be interpreted as a result of the recoil force that the cloak exerts upon the ray. The total radiation pressure on an ideal cloak is shown to be exactly zero, effecting a stationary cloak.

  15. Air pollution radiative forcing from specific emissions sectors at 2030

    NASA Astrophysics Data System (ADS)

    Unger, Nadine; Shindell, Drew T.; Koch, Dorothy M.; Streets, David G.

    2008-01-01

    Reduction of short-lived air pollutants can contribute to mitigate global warming in the near-term with ancillary benefits to human health. However, the radiative forcings of short-lived air pollutants depend on the location and source type of the precursor emissions. We apply the Goddard Institute for Space Studies atmospheric composition-climate model to quantify near-future (2030 A1B) global annual mean radiative forcing by ozone (O3) and sulfate from six emissions sectors in seven geographic regions. At 2030 the net forcings from O3, sulfate, black and organic carbon, and indirect CH4 effects for each emission sector are (in mWm-2) biomass burning, +95; domestic, +68; transportation, +67; industry, -131; and power, -224. Biomass burning emissions in East Asia and central and southern Africa, domestic biofuel emissions in East Asia, south Asia, and central and southern Africa, and transportation emissions in Europe and North America have large net positive forcings and are therefore attractive targets to counter global warming. Power and industry emissions from East Asia, south Asia, and north Africa and the Middle East have large net negative forcings. Therefore air quality control measures that affect these regional sectors require offsetting climate measures to avoid a warming impact. Linear relationships exist between O3 forcing and biomass burning and domestic biofuel CO precursor emissions independent of region with sensitivity of +0.2 mWm-2/TgCO. Similarly, linear relationships exist between sulfate forcing and SO2 precursor emissions that depend upon region but are independent of sector with sensitivities ranging from -3 to -12 mWm-2/TgS.

  16. Cloud radiative forcing effects on observed and simulated global energetics

    NASA Technical Reports Server (NTRS)

    Sohn, Byung-Ju; Robertson, Franklin

    1993-01-01

    The research objectives are the following: (1) to examine how cloud-radiation processes generate/destroy available potential energy by altering both meridional and zonal temperature gradient; (2) to investigate how the atmospheric dynamic fields respond to the cloud-altered mass distributions through the energy conversion circuit; and (3) to examine how the improved version of CCM1 simulates observationally obtained cloud-radiative forcing and its associated energetics and circulations. Significant accomplishments in the past year towards obtaining these objectives and the focus of current research and plans for next year are discussed.

  17. 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.


  18. CHARMM General Force Field (CGenFF): A force field for drug-like molecules compatible with the CHARMM all-atom additive biological force fields

    PubMed Central

    Vanommeslaeghe, K.; Hatcher, E.; Acharya, C.; Kundu, S.; Zhong, S.; Shim, J.; Darian, E.; Guvench, O.; Lopes, P.; Vorobyov, I.; MacKerell, A. D.

    2010-01-01

    The widely used CHARMM additive all-atom force field includes parameters for proteins, nucleic acids, lipids and carbohydrates. In the present paper an extension of the CHARMM force field to drug-like molecules is presented. The resulting CHARMM General Force Field (CGenFF) covers a wide range of chemical groups present in biomolecules and drug-like molecules, including a large number of heterocyclic scaffolds. The parametrization philosophy behind the force field focuses on quality at the expense of transferability, with the implementation concentrating on an extensible force field. Statistics related to the quality of the parametrization with a focus on experimental validation are presented. Additionally, the parametrization procedure, described fully in the present paper in the context of the model systems, pyrrolidine, and 3-phenoxymethylpyrrolidine will allow users to readily extend the force field to chemical groups that are not explicitly covered in the force field as well as add functional groups to and link together molecules already available in the force field. CGenFF thus makes it possible to perform “all-CHARMM” simulations on drug-target interactions thereby extending the utility of CHARMM force fields to medicinally relevant systems. PMID:19575467

  19. Surface summertime radiative forcing by shallow cumuli at the Atmospheric Radiation Measurement Southern Great Plains site

    SciTech Connect

    Berg, Larry K.; Kassianov, Evgueni I.; Long, Charles N.; Mills Jr., David L.

    2011-01-08

    Although shallow cumuli are common over large areas of the globe, their impact on the surface radiative forcing has not been carefully evaluated. This study addresses this shortcoming by analyzing data from days with shallow cumuli collected over eight summers (2000-2007) at the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) Climate Research Facility (collectively ACRF) Southern Great Plains site. During periods with clouds, the average shortwave and longwave radiative forcings are 45.5 W m-2 and +11.6 W m-2, respectively. The forcing has been defined so that a negative (positive) forcing indicates a surface cooling (warming). On average, the shortwave forcing is negative, however, instances with positive shortwave forcing are observed approximately 20% of the time. These positive values of shortwave forcing are associated with three-dimensional radiative effects of the clouds. The three-dimensional effects are shown to be largest for intermediate cloud amounts. The magnitude of the three-dimensional effects decreased with averaging time, but it is not negligibly small even for large averaging times as long as four hours.

  20. Tissue deformation induced by radiation force from Gaussian transducers.

    PubMed

    Myers, Matthew R

    2006-05-01

    Imaging techniques based upon the tissue mechanical response to an acoustic radiation force are being actively researched. In this paper a model for predicting steady-state tissue displacement induced by a radiation force arising from the absorption of Gaussian ultrasound beams is presented. A simple analytic expression is derived that agrees closely with the numerical quadrature of the displacement convolution integrals. The analytic result reveals the dependence of the steady-state axial displacement upon the operational parameters, e.g., an inverse proportional relationship to the tissue shear modulus. The derivation requires that the transducer radius be small compared to the focal length, but accurate results were obtained for transducer radii comparable to the focal length. Favorable comparisons with displacement predictions for non-Gaussian transducers indicate that the theory is also useful for a broader range of transducer intensity profiles. PMID:16708969

  1. Aerosol radiative forcing in the European Skynet Radiometers network

    NASA Astrophysics Data System (ADS)

    Estelles, V.; Campanelli, M.; Expósito, F. J.; Utrillas, M. P.; Díaz, J. P.; Martínez-Lozano, J. A.

    2012-04-01

    The influence of the atmospheric aerosols is one of the most important factors of the Earth climate system and, despite of our present understanding have increased in last years, they are still one of the largest unknown variables. In fact, recently, the total anthropogenic radiative effect on global scale was estimated to be +1.6 (-1.0 to +0.8) Wm-2, of which -0.5 (±0.4) Wm-2 are associated to the direct radiative forcing of the atmospheric aerosols. In order to reduce the current uncertainties of the direct aerosol forcing it is important to accurately determine the aerosol effect by combining modeling techniques with experimental radiation and aerosol measurements. To model the radiative effect of the aerosols, atmospheric radiative transfer models are applied, such as SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer), GAME (Global Atmospheric Model), MODTRAN (Moderate resolution atmospheric Transmission) and RSTAR. With these models, the direct aerosol radiative forcing at ground and top of atmosphere levels is estimated as the difference between the energy flux for an atmosphere with/without aerosols. To estimate the accuracy of the models, the modeled global, diffuse and direct solar radiation at ground level is compared with experimental measurements. To characterize the aerosol properties, sun-sky radiometric measurements at ground level are also needed, usually from systems such as Cimel CE318 or Prede POM. In last years, a good amount of such studies have been performed for different areas of the world. One of the most promising efforts comes from the AERONET (Aerosol Robotic Network). AERONET is an international operative network of Cimel CE318 sky-sunphotometers that provides the most extensive aerosol database globally available. García et al. (2008) already validated the AERONET direct aerosol forcing methodology with solar radiation measurements from the SolRad-Net (Solar Radiation Network) and BSRN (Baseline Solar Ratiation Network) for

  2. Improving Estimates of Cloud Radiative Forcing over Greenland

    NASA Astrophysics Data System (ADS)

    Wang, W.; Zender, C. S.

    2014-12-01

    Multiple driving mechanisms conspire to increase melt extent and extreme melt events frequency in the Arctic: changing heat transport, shortwave radiation (SW), and longwave radiation (LW). Cloud Radiative Forcing (CRF) of Greenland's surface is amplified by a dry atmosphere and by albedo feedback, making its contribution to surface melt even more variable in time and space. Unfortunately accurate cloud observations and thus CRF estimates are hindered by Greenland's remoteness, harsh conditions, and low contrast between surface and cloud reflectance. In this study, cloud observations from satellites and reanalyses are ingested into and evaluated within a column radiative transfer model. An improved CRF dataset is obtained by correcting systematic discrepancies derived from sensitivity experiments. First, we compare the surface radiation budgets from the Column Radiation Model (CRM) driven by different cloud datasets, with surface observations from Greenland Climate Network (GC-Net). In clear skies, CRM-estimated surface radiation driven by water vapor profiles from both AIRS and MODIS during May-Sept 2010-2012 are similar, stable, and reliable. For example, although AIRS water vapor path exceeds MODIS by 1.4 kg/m2 on a daily average, the overall absolute difference in downwelling SW is < 4 W/m2. CRM estimates are within 20 W/m2 range of GC-Net downwelling SW. After calibrating CRM in clear skies, the remaining differences between CRM and observed surface radiation are primarily attributable to differences in cloud observations. We estimate CRF using cloud products from MODIS and from MERRA. The SW radiative forcing of thin clouds is mainly controlled by cloud water path (CWP). As CWP increases from near 0 to 200 g/m2, the net surface SW drops from over 100 W/m2 to 30 W/m2 almost linearly, beyond which it becomes relatively insensitive to CWP. The LW is dominated by cloud height. For clouds at all altitudes, the lower the clouds, the greater the LW forcing. By

  3. Sensitivity of the shortwave to longwave ratio in contrail radiative forcing calculations with different radiation schemes

    NASA Astrophysics Data System (ADS)

    Ponater, Michael; Dietmüller, Simone; Frömming, Christine

    2013-04-01

    Contrail radiative forcing is difficult to obtain, even if contrail parameters like coverage, ice water content, crystal size etc. are known. A substantial respective uncertainty has been documented in literature. One key problem is the considerable amount of cancellation between the positive (warming) component from the contrails' greenhouse effect and the negative (cooling) component from backscattering of solar irradiance. Furthermore, the longwave/shortwave cancellation depends on ambient parameters like temperature, co-existing natural clouds, and surface albedo. High demands are set for any radiative transfer model aiming at reliable results of the net radiative forcing. Climate models are optimally suited to provide a representation of the required variety of ambient parameters for a climatological estimate of contrail radiative forcing. However, comprehensive global climate models use simplified radiative transfer schemes for reasons of computational economy. Hence, a dedicated test of these schemes is required. We present a comparison of contrail radiative forcing estimates from two global climate models with different radiation schemes. The first estimate results from the ECHAM4 model that has been frequently used over the last ten years for contrail climate impact calculations. The second estimate originates from the more recent ECHAM5/MESSy Atmospheric Chemistry (EMAC) model that is used in current and future studies. Use is made of the so-called "Myhre benchmark test" with specified contrail parameters. Particular emphasis is given to longwave/shortwave ratios for different seasons and to daytime/nighttime differences.

  4. Distribution and Radiative Forcing of Tropical Thin Cirrus Clouds

    NASA Technical Reports Server (NTRS)

    Lee, Joonsuk; Yang, Ping; Dessler, Andrew E.; Gao, Bo-Cai; Platnick, Steven

    2009-01-01

    To understand the radiative impact of tropical thin cirrus clouds, the frequency of occurrence and optical depths of these clouds have been derived. Thin cirrus clouds are defined here as being those that are not detected by the operational Moderate Resolution Imaging Spectroradiometer (MODIS) cloud mask, corresponding to an optical depth value of approximately 0.3 or smaller, but that are detectable in terms of the cirrus reflectance product based on the MODIS 1.375-micron channel. With such a definition, thin cirrus clouds were present in more than 40% of the pixels flagged as clear sky by the operational MODIS cloud mask algorithm. It is shown that these thin cirrus clouds are frequently observed in deep convective regions in the western Pacific. Thin cirrus optical depths were derived from the cirrus reflectance product. Regions of significant cloud fraction and large optical depths were observed in the Northern Hemisphere during the boreal spring and summer and moved southward during the boreal autumn and winter. The radiative effects of tropical thin cirrus clouds were studied on the basis of the retrieved cirrus optical depths, the atmospheric profiles derived from the Atmospheric Infrared Sounder (AIRS) observations, and a radiative transfer model in conjunction with a parameterization of ice cloud spectral optical properties. To understand how these clouds regulate the radiation field in the atmosphere, the instantaneous net fluxes at the top of the atmosphere (TOA) and at the surface were calculated. The present study shows positive and negative net forcings at the TOA and at the surface, respectively. The positive (negative) net forcing at the TOA (surface) is due to the dominance of longwave (shortwave) forcing. Both the TOA and surface forcings are in a range of 0-20 W/sq m, depending on the optical depths of thin cirrus clouds.

  5. Enhanced shortwave cloud radiative forcing due to anthropogenic aerosols

    SciTech Connect

    Schwartz, S.E.; Slingo, A.

    1995-05-01

    It has been suggested that anthropogenic aerosols in the troposphere can influence the microphysical properties of clouds and in turn their reflectivity, thereby exerting a radiative influence on climate. This article presents the theoretical basis for of this so-called indirect forcing and reviews pertinent observational evidence and climate model calculations of its magnitude and geographical distribution. We restrict consideration to liquid-water clouds.

  6. Radiative Forcing by Long-Lived Greenhouse Gases: Calculations with the AER Radiative Transfer Models

    SciTech Connect

    Collins, William; Iacono, Michael J.; Delamere, Jennifer S.; Mlawer, Eli J.; Shephard, Mark W.; Clough, Shepard A.; Collins, William D.

    2008-04-01

    A primary component of the observed, recent climate change is the radiative forcing from increased concentrations of long-lived greenhouse gases (LLGHGs). Effective simulation of anthropogenic climate change by general circulation models (GCMs) is strongly dependent on the accurate representation of radiative processes associated with water vapor, ozone and LLGHGs. In the context of the increasing application of the Atmospheric and Environmental Research, Inc. (AER) radiation models within the GCM community, their capability to calculate longwave and shortwave radiative forcing for clear sky scenarios previously examined by the radiative transfer model intercomparison project (RTMIP) is presented. Forcing calculations with the AER line-by-line (LBL) models are very consistent with the RTMIP line-by-line results in the longwave and shortwave. The AER broadband models, in all but one case, calculate longwave forcings within a range of -0.20 to 0.23 W m{sup -2} of LBL calculations and shortwave forcings within a range of -0.16 to 0.38 W m{sup -2} of LBL results. These models also perform well at the surface, which RTMIP identified as a level at which GCM radiation models have particular difficulty reproducing LBL fluxes. Heating profile perturbations calculated by the broadband models generally reproduce high-resolution calculations within a few hundredths K d{sup -1} in the troposphere and within 0.15 K d{sup -1} in the peak stratospheric heating near 1 hPa. In most cases, the AER broadband models provide radiative forcing results that are in closer agreement with high 20 resolution calculations than the GCM radiation codes examined by RTMIP, which supports the application of the AER models to climate change research.

  7. Remote Sensing of Aerosol and their Radiative Forcing of Climate

    NASA Technical Reports Server (NTRS)

    Kaufman, Yoram J.; Tanre, Didier; Remer, Lorraine A.

    1999-01-01

    Remote sensing of aerosol and aerosol radiative forcing of climate is going through a major transformation. The launch in next few years of new satellites designed specifically for remote sensing of aerosol is expected to further revolutionized aerosol measurements: until five years ago satellites were not designed for remote sensing of aerosol. Aerosol optical thickness was derived as a by product, only over the oceans using one AVHRR channel with errors of approx. 50%. However it already revealed a very important first global picture of the distribution and sources of aerosol. In the last 5 years we saw the introduction of polarization and multi-view observations (POLDER and ATSR) for satellite remote sensing of aerosol over land and ocean. Better products are derived from AVHRR using its two channels. The new TOMS aerosol index shows the location and transport of aerosol over land and ocean. Now we anticipate the launch of EOS-Terra with MODIS, MISR and CERES on board for multi-view, multi-spectral remote sensing of aerosol and its radiative forcing. This will allow application of new techniques, e.g. using a wide spectral range (0.55-2.2 microns) to derive precise optical thickness, particle size and mass loading. Aerosol is transparent in the 2.2 microns channel, therefore this channel can be used to detect surface features that in turn are used to derive the aerosol optical thickness in the visible part of the spectrum. New techniques are developed to derive the aerosol single scattering albedo, a measure of absorption of sunlight, and techniques to derive directly the aerosol forcing at the top of the atmosphere. In the last 5 years a global network of sun/sky radiometers was formed, designed to communicate in real time the spectral optical thickness from 50-80 locations every day, every 15 minutes. The sky angular and spectral information is also measured and used to retrieve the aerosol size distribution, refractive index, single scattering albedo and the

  8. Small global-mean cooling due to volcanic radiative forcing

    NASA Astrophysics Data System (ADS)

    Gregory, J. M.; Andrews, T.; Good, P.; Mauritsen, T.; Forster, P. M.

    2016-03-01

    In both the observational record and atmosphere-ocean general circulation model (AOGCM) simulations of the last ˜ 150 years, short-lived negative radiative forcing due to volcanic aerosol, following explosive eruptions, causes sudden global-mean cooling of up to ˜ 0.3 K. This is about five times smaller than expected from the transient climate response parameter (TCRP, K of global-mean surface air temperature change per W m-2 of radiative forcing increase) evaluated under atmospheric CO2 concentration increasing at 1 % yr-1. Using the step model (Good et al. in Geophys Res Lett 38:L01703, 2011. doi: 10.1029/2010GL045208), we confirm the previous finding (Held et al. in J Clim 23:2418-2427, 2010. doi: 10.1175/2009JCLI3466.1) that the main reason for the discrepancy is the damping of the response to short-lived forcing by the thermal inertia of the upper ocean. Although the step model includes this effect, it still overestimates the volcanic cooling simulated by AOGCMs by about 60 %. We show that this remaining discrepancy can be explained by the magnitude of the volcanic forcing, which may be smaller in AOGCMs (by 30 % for the HadCM3 AOGCM) than in off-line calculations that do not account for rapid cloud adjustment, and the climate sensitivity parameter, which may be smaller than for increasing CO2 (40 % smaller than for 4 × CO2 in HadCM3).

  9. Radiative forcing of black carbon over eastern India

    NASA Astrophysics Data System (ADS)

    Sreekanth, V.; Niranjan, K.; Madhavan, B. L.

    2007-09-01

    Measurements of aerosol Black Carbon using a 7 channel Aethalometer at Visakhapatnam, a coastal tropical station on the east coast of India are used to study the temporal variation of surface BC mass concentration. The surface BC mass concentrations show a significant diurnal variation which is seasonally dependant. Analysis using the multi spectral data indicates that the BC mass does not show significant absorption due to non-BC aerosol species which indicates that the surface BC mass is dominated by fossil fuel sources with no indication of any other strong anthropogenic source. The Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model was used in conjunction with Optical Properties of Aerosols and Clouds (OPAC) to estimate the BC radiative forcing. The results show large negative surface forcing during winter (-35.78 W/m2), moderate during summer (-16.8 W/m2) and lower forcing during monsoon (-9.9 W/m2) and post monsoon (-2.81 W/m2). The forcing at the top of the atmosphere is positive for all the seasons.

  10. Radiative forcing calculations for CH{sub 3}Br

    SciTech Connect

    Grossman, A.S.; Blass, W.E.; Wuebbles, D.J.

    1995-06-01

    Methyl Bromide, CH{sub 3}Br, is the major organobromine species in the lower atmosphere and is a primary source of bromine in the stratosphere. It has a lifetime of 1.3 years. The IR methyl bromide spectra in the atmospheric window region, 7--13{mu}, was determined using a well tested Coriolis resonance and {ell}-doubling (and {ell}-resonance) computational system. A radiative forcing value of 0.00493 W/m{sup 2}/ppbv was obtained for CH{sub 3}Br and is approximately linear in the background abundance. This value is about 2 percent of the forcing of CFC-11 and about 278 times the forcing of C0{sub 2}, on a per molecule basis. The radiative forcing calculation is used to estimate the global warming potential (GWP) of CH{sub 3}Br. The results give GWPs for CH{sub 3}Br of the order of 13 for an integration period of 20 years and 4 for an integration period of 100 years (assuming C0{sub 2} = 1, following IPCC [1994]). While CH{sub 3}Br has a GWP which is approximately 25 percent of the GWP of CH{sub 4}, the current emission rates are too low to cause serious atmospheric greenhouse heating effects at this time.

  11. Effective radiative forcing from historical land use change

    NASA Astrophysics Data System (ADS)

    Andrews, Timothy; Betts, Richard A.; Booth, Ben B. B.; Jones, Chris D.; Jones, Gareth S.

    2016-08-01

    The effective radiative forcing (ERF) from the biogeophysical effects of historical land use change is quantified using the atmospheric component of the Met Office Hadley Centre Earth System model HadGEM2-ES. The global ERF at 2005 relative to 1860 (1700) is -0.4 (-0.5) Wm-2, making it the fourth most important anthropogenic driver of climate change over the historical period (1860-2005) in this model and larger than most other published values. The land use ERF is found to be dominated by increases in the land surface albedo, particularly in North America and Eurasia, and occurs most strongly in the northern hemisphere winter and spring when the effect of unmasking underlying snow, as well as increasing the amount of snow, is at its largest. Increased bare soil fraction enhances the seasonal cycle of atmospheric dust and further enhances the ERF. Clouds are shown to substantially mask the radiative effect of changes in the underlying surface albedo. Coupled atmosphere-ocean simulations forced only with time-varying historical land use change shows substantial global cooling (dT = -0.35 K by 2005) and the climate resistance (ERF/dT = 1.2 Wm-2 K-1) is consistent with the response of the model to increases in CO2 alone. The regional variation in land surface temperature change, in both fixed-SST and coupled atmosphere-ocean simulations, is found to be well correlated with the spatial pattern of the forced change in surface albedo. The forcing-response concept is found to work well for historical land use forcing—at least in our model and when the forcing is quantified by ERF. Our results suggest that land-use changes over the past century may represent a more important driver of historical climate change then previously recognised and an underappreciated source of uncertainty in global forcings and temperature trends over the historical period.

  12. Long-wave radiative forcing due to desert dust

    NASA Astrophysics Data System (ADS)

    Gunn, L. N.; Collins, W.

    2011-12-01

    Radiative forcing due to aerosols has been identified by the IPCC as a major contributor to the total radiative forcing uncertainty budget. Optically thick plumes of dust and pollutants extending out from Africa and Asia can be lifted into the middle troposphere and often are transported over synoptic length scales. These events can decrease the upwelling long-wave fluxes at the top of the atmosphere, especially in the mid-infrared "window". Although the long-wave effects of dust are included in model simulations, they are hard to validate in the absence of satellite-driven global estimates. Using hyper spectral satellite measurements (from NASA's AIRS instrument) it is possible to estimate the effect of dust on the outgoing long-wave radiation directly from the measured spectra, by differencing the simulated clear sky radiance spectra (which are calculated using ECMWF analysis) and the observed dust filled radiance spectra (observations from AIRS). We will summarize this method and show global estimates of the dust radiative effect in the long-wave. These global estimates will be used to validate GCM model output and help us to improve our understanding of dust in the global energy budget.

  13. Shortwave spectral radiative forcing of cumulus clouds from surface observations

    NASA Astrophysics Data System (ADS)

    Kassianov, E.; Barnard, J.; Berg, L. K.; Long, C. N.; Flynn, C.

    2011-04-01

    The spectral changes of the shortwave total, direct and diffuse cloud radiative forcing (CRF) at surface are examined for the first time using spectrally resolved all-sky flux observations and clear-sky fluxes. The latter are computed applying a physically based approach, which accounts for the spectral changes of aerosol optical properties and surface albedo. Application of this approach to 13 summertime days with single-layer continental cumuli demonstrates: (i) the substantial contribution of the diffuse component to the total CRF, (ii) the well-defined spectral variations of total CRF in the visible spectral region, and (iii) the strong statistical relationship between spectral (500 nm) and shortwave broadband values of total CRF. Our results suggest that the framework based on the visible narrowband fluxes can provide important radiative quantities for rigorous evaluation of radiative transfer parameterizations and also can be applied for estimation of the shortwave broadband CRF.

  14. Acoustic Radiation Force Impulse Measurement in Renal Transplantation

    PubMed Central

    Lee, Juhan; Oh, Young Taik; Joo, Dong Jin; Ma, Bo Gyoung; Lee, A-lan; Lee, Jae Geun; Song, Seung Hwan; Kim, Seung Up; Jung, Dae Chul; Chung, Yong Eun; Kim, Yu Seun

    2015-01-01

    Abstract Interstitial fibrosis and tubular atrophy (IF/TA) is a common cause of kidney allograft loss. Several noninvasive techniques developed to assess tissue fibrosis are widely used to examine the liver. However, relatively few studies have investigated the use of elastographic methods to assess transplanted kidneys. The aim of this study was to explore the clinical implications of the acoustic radiation force impulse (ARFI) technique in renal transplant patients. A total of 91 patients who underwent living donor renal transplantation between September 2010 and January 2013 were included in this prospective study. Shear wave velocity (SWV) was measured by ARFI at baseline and predetermined time points (1 week and 6 and 12 months after transplantation). Protocol biopsies were performed at 12 months. Instead of reflecting IF/TA, SWVs were found to be related to time elapsed after transplantation. Mean SWV increased continuously during the first postoperative year (P < 0.001). In addition, mixed model analysis showed no correlation existed between SWV and serum creatinine (r = −0.2426, P = 0.0771). There was also no evidence of a relationship between IF/TA and serum creatinine (odds ratio [OR] = 1.220, P = 0.7648). Furthermore, SWV temporal patterns were dependent on the kidney weight to body weight ratio (KW/BW). In patients with a KW/BW <3.5 g/kg, mean SWV continuously increased for 12 months, whereas it decreased after 6 months in those with a KW/BW ≥3.5 g/kg. No significant correlation was observed between SWV and IF/TA or renal dysfunction. However, SWV was found to be related to the time after transplantation. Renal hemodynamics influenced by KW/BW might impact SWV values. PMID:26426636

  15. 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.

  16. Accounting for radiative forcing from albedo change in future global land-use scenarios

    SciTech Connect

    Jones, Andrew D.; Calvin, Katherine V.; Collins, William D.; Edmonds, James A.

    2015-08-01

    We demonstrate the effectiveness of a new method for quantifying radiative forcing from land use and land cover change (LULCC) within an integrated assessment model, the Global Change Assessment Model (GCAM). The method relies on geographically differentiated estimates of radiative forcing from albedo change associated with major land cover transitions derived from the Community Earth System Model. We find that conversion of 1 km² of woody vegetation (forest and shrublands) to non-woody vegetation (crops and grassland) yields between 0 and –0.71 nW/m² of globally averaged radiative forcing determined by the vegetation characteristics, snow dynamics, and atmospheric radiation environment characteristic within each of 151 regions we consider globally. Across a set of scenarios designed to span a range of potential future LULCC, we find LULCC forcing ranging from –0.06 to –0.29 W/m² by 2070 depending on assumptions regarding future crop yield growth and whether climate policy favors afforestation or bioenergy crops. Inclusion of this previously uncounted forcing in the policy targets driving future climate mitigation efforts leads to changes in fossil fuel emissions on the order of 1.5 PgC/yr by 2070 for a climate forcing limit of 4.5 Wm–2, corresponding to a 12–67 % change in fossil fuel emissions depending on the scenario. Scenarios with significant afforestation must compensate for albedo-induced warming through additional emissions reductions, and scenarios with significant deforestation need not mitigate as aggressively due to albedo-induced cooling. In all scenarios considered, inclusion of albedo forcing in policy targets increases forest and shrub cover globally.

  17. Evaluation of aerosol direct radiative forcing in MIRAGE

    NASA Astrophysics Data System (ADS)

    Ghan, Steven; Laulainen, Nels; Easter, Richard; Wagener, Richard; Nemesure, Seth; Chapman, Elaine; Zhang, Yang; Leung, Ruby

    2001-03-01

    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 Exchange (MIRAGE). The treatment of water uptake in MIRAGE agrees with laboratory measurements, and the growth of aerosol extinction with relative humidity in MIRAGE simulations agrees with field measurements. The simulated frequency of relative humidity near 100% is about twice that of 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, but simulated optical depths are too low over Brazil and central Canada. Simulated optical depths are mostly within a factor of 2 of satellite estimates, but are too high off the east coasts of the United States and China and too low off the coast of West Africa and in the Arabian Sea. The simulated single-scatter albedo is consistent with surface measurements. MIRAGE correctly simulates a larger Ångström exponent near regions with emissions of submicron particles and aerosol precursor gases, and a smaller exponent near regions with emissions of coarse particles. The simulated sensitivity of radiative forcing to aerosol optical depth is consistent with estimates from measurements. The simulated direct forcing is within the uncertainty of estimates from measurements in the North Atlantic.

  18. Sensitivity of contrail cirrus radiative forcing to air traffic scheduling

    NASA Astrophysics Data System (ADS)

    Newinger, Christina; Burkhardt, Ulrike

    2012-05-01

    Air traffic effects high cloudiness and therefore the Earth's radiation budget by producing contrail cirrus. Contrail cirrus comprise of line-shaped contrails and irregularly shaped ice clouds that originate from them. The warming effect of contrail cirrus is disproportionally large at night, since at daytime the cooling due to the short wave cloud albedo effect acts toward compensating the long wave warming effect. Therefore it has been suggested to restrict air traffic to daytime in order to reduce its climate impact. The potential for reducing the contrail cirrus radiative forcing by shifting air traffic to daytime depends on the diurnal cycle of contrail cirrus coverage which is in turn determined by the diurnal cycle of air traffic and the contrail cirrus lifetimes. Simulations with a global atmospheric general circulation model indicate that the annual mean contrail cirrus coverage may be almost constant over the day even in areas where air traffic is close to zero at night. A conceptual model describing the temporal evolution of contrail cirrus coverage reveals that this is due to the large variability in contrail cirrus lifetimes in combination with the spreading of contrail cirrus. This large variability of lifetimes is consistent with observational evidence but more observations are needed to constrain the contrail lifetime distribution. An idealized mitigation experiment, shifting nighttime flights to daytime, indicates that contrail cirrus radiative forcing is not significantly changed.

  19. RCP4.5: A Pathway for Stabilization of Radiative Forcing by 2100

    SciTech Connect

    Thomson, Allison M.; Calvin, Katherine V.; Smith, Steven J.; Kyle, G. Page; Volke, April C.; Patel, Pralit L.; Delgado Arias, Sabrina; Bond-Lamberty, Benjamin; Wise, Marshall A.; Clarke, Leon E.; Edmonds, James A.

    2011-07-29

    Representative Concentration Pathway (RCP) 4.5 is a scenario that stabilizes radiative forcing at 4.5 W m{sup -2} in the year 2100 without ever exceeding that value. Simulated with the Global Change Assessment Model (GCAM), RCP4.5 includes long-term, global emissions of greenhouse gases, short-lived species, and land-use-land-cover in a global economic framework. RCP4.5 was updated from earlier GCAM scenarios to incorporate historical emissions and land cover information common to the RCP process and follows a cost-minimizing pathway to reach the target radiative forcing. The imperative to limit emissions in order to reach this target drives changes in the energy system, including shifts to electricity, to lower emissions energy technologies and to the deployment of carbon capture and geologic storage technology. In addition, the RCP4.5 emissions price also applies to land use emissions; as a result, forest lands expand from their present day extent. The simulated future emissions and land use were downscaled from the regional simulation to a grid to facilitate transfer to climate models. While there are many alternative pathways to achieve a radiative forcing level of 4.5 W m{sup -2}, the application of the RCP4.5 provides a common platform for climate models to explore the climate system response to stabilizing the anthropogenic components of radiative forcing.

  20. Dust radiative forcing in snow of the Upper Colorado River Basin: 2. Interannual variability in radiative forcing and snowmelt rates

    NASA Astrophysics Data System (ADS)

    Skiles, S. Mckenzie; Painter, Thomas H.; Deems, Jeffrey S.; Bryant, Ann C.; Landry, Christopher C.

    2012-07-01

    Here we present the radiative and snowmelt impacts of dust deposition to snow cover using a 6-year energy balance record (2005-2010) at alpine and subalpine micrometeorological towers in the Senator Beck Basin Study Area (SBBSA) in southwestern Colorado, USA. These results follow from the measurements described in part I. We simulate the evolution of snow water equivalent at each station under scenarios of observed and dust-free conditions, and +2°C and +4°C melt-season temperature perturbations to these scenarios. Over the 6 years of record, daily mean dust radiative forcing ranged from 0 to 214 W m-2, with hourly peaks up to 409 W m-2. Mean springtime dust radiative forcings across the period ranged from 31 to 49 W m-2 at the alpine site and 45 to 75 W m-2 at the subalpine site, in turn shortening snow cover duration by 21 to 51 days. The dust-advanced loss of snow cover (days) is linearly related to total dust concentration at the end of snow cover, despite temporal variability in dust exposure and solar irradiance. Under clean snow conditions, the temperature increases shorten snow cover by 5-18 days, whereas in the presence of dust they only shorten snow duration by 0-6 days. Dust radiative forcing also causes faster and earlier peak snowmelt outflow with daily mean snowpack outflow doubling under the heaviest dust conditions. On average, snow cover at the towers is lost 2.5 days after peak outflow in dusty conditions, and 1-2 weeks after peak outflow in clean conditions.

  1. 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.

  2. Do diurnal aerosol changes affect daily average radiative forcing?

    NASA Astrophysics Data System (ADS)

    Kassianov, Evgueni; Barnard, James; Pekour, Mikhail; Berg, Larry K.; Michalsky, Joseph; Lantz, Kathy; Hodges, Gary

    2013-06-01

    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 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.

  3. Vertical profiles of aerosol radiative forcing - a comparison of AEROCOM phase 2 model submissions

    NASA Astrophysics Data System (ADS)

    Samset, B. H.; Myhre, G.

    2012-04-01

    Aerosols in the earth's atmosphere affect the radiation balance of the planet. The radiative forcing (RF) induced by a given aerosol burden is however sensitive to its vertical density profile, in addition to aerosol optical properties, cloud distributions and surface albedo. Differences in vertical profiles are thought to be among the causes for the large intermodel differences in RF of the aerosol direct effect. As part of the AEROCOM phase 2 direct radiative forcing experiment, this study compares 3D concentration fields of black carbon from fossil fuel burning (BC) and sulphate (SO4) from a set of major global climate models. The participating models were run using a prescribed set of emissions of aerosol and aerosol precursors and the same meteorological year. We assume that model differences due to the aerosol vertical profile can be factored out from other differences such as aerosol physics, radiative transfer or ground albedo. We consequently analyse model RF variability using profiles of normalized RF (radiative forcing per unit mass, NDRF) calculated from a single model. This tool allows us to quantify the fraction of the intermodel variability due to differences in aerosol vertical profiles. We show that there are still significant differences between both modelled vertical density profiles, treatment of aerosol physics and other factors influencing the RF profiles.

  4. Climate Response of Direct Radiative Forcing of Anthropogenic Black Carbon

    NASA Technical Reports Server (NTRS)

    Chung, Serena H.; Seinfeld,John H.

    2008-01-01

    The equilibrium climate effect of direct radiative forcing of anthropogenic black carbon (BC) is examined by 100-year simulations in the Goddard Institute for Space Studies General Circulation Model II-prime coupled to a mixed-layer ocean model. Anthropogenic BC is predicted to raise globally and annually averaged equilibrium surface air temperature by 0.20 K if BC is assumed to be externally mixed. The predicted increase is significantly greater in the Northern Hemisphere (0.29 K) than in the Southern Hemisphere (0.11 K). If BC is assumed to be internally mixed with the present day level of sulfate aerosol, the predicted annual mean surface temperature increase rises to 0.37 K globally, 0.54 K for the Northern Hemisphere, and 0.20 K for the Southern Hemisphere. The climate sensitivity of BC direct radiative forcing is calculated to be 0.6 K W (sup -1) square meters, which is about 70% of that of CO2, independent of the assumption of BC mixing state. The largest surface temperature response occurs over the northern high latitudes during winter and early spring. In the tropics and midlatitudes, the largest temperature increase is predicted to occur in the upper troposphere. Direct radiative forcing of anthropogenic BC is also predicted to lead to a change of precipitation patterns in the tropics; precipitation is predicted to increase between 0 and 20 N and decrease between 0 and 20 S, shifting the intertropical convergence zone northward. If BC is assumed to be internally mixed with sulfate instead of externally mixed, the change in precipitation pattern is enhanced. The change in precipitation pattern is not predicted to alter the global burden of BC significantly because the change occurs predominantly in regions removed from BC sources.

  5. Radiation force on a single atom in a cavity

    NASA Technical Reports Server (NTRS)

    Kim, M. S.

    1992-01-01

    We consider the radiation pressure microscopically. Two perfectly conducting plates are parallelly placed in a vacuum. As the vacuum field hits the plates they get pressure from the vacuum. The excessive outside modes of the vacuum field push the plates together, which is known as the Casimer force. We investigate the quantization of the standing wave between the plates to study the interaction between this wave and the atoms on the plates or between the plates. We show that even the vacuum field pushes the atom to place it at nodes of the standing wave.

  6. Nonlinear aspects of acoustic radiation force in biomedical applications

    SciTech Connect

    Ostrovsky, Lev; Tsyuryupa, Sergey; Sarvazyan, Armen

    2015-10-28

    In the past decade acoustic radiation force (ARF) became a powerful tool in numerous biomedical applications. ARF from a focused ultrasound beam acts as a virtual “finger” for remote probing of internal anatomical structures and obtaining diagnostic information. This presentation deals with generation of shear waves by nonlinear focused beams. Albeit the ARF has intrinsically nonlinear origin, in most cases the primary ultrasonic wave was considered in the linear approximation. In this presentation, we consider the effects of nonlinearly distorted beams on generation of shear waves by such beams.

  7. 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.

  8. Additional interfacial force in lattice Boltzmann models for incompressible multiphase flows.

    PubMed

    Li, Q; Luo, K H; Gao, Y J; He, Y L

    2012-02-01

    The existing lattice Boltzmann models for incompressible multiphase flows are mostly constructed with two distribution functions: one is the order parameter distribution function, which is used to track the interface between different phases, and the other is the pressure distribution function for solving the velocity field. In this paper, it is shown that in these models the recovered momentum equation is inconsistent with the target one: an additional force is included in the recovered momentum equation. The additional force has the following features. First, it is proportional to the macroscopic velocity. Second, it is zero in every single-phase region but is nonzero in the interface. Therefore it can be interpreted as an interfacial force. To investigate the effects of the additional interfacial force, numerical simulations are carried out for the problem of Rayleigh-Taylor instability, droplet splashing on a thin liquid film, and the evolution of a falling droplet under gravity. Numerical results demonstrate that, with the increase of the velocity or the Reynolds number, the additional interfacial force will gradually have an important influence on the interface and affect the numerical accuracy. PMID:22463354

  9. Postfire influences of snag attrition on albedo and radiative forcing

    NASA Astrophysics Data System (ADS)

    O'Halloran, Thomas L.; Acker, Steven A.; Joerger, Verena M.; Kertis, Jane; Law, Beverly E.

    2014-12-01

    This paper examines albedo perturbation and radiative forcing after a high-severity fire in a mature forest in the Oregon Cascade Range. Correlations between postfire albedo and seedling, sapling, and snag (standing dead tree) density were investigated across fire severity classes and seasons for years 4-15 after fire. Albedo perturbation was 14 times larger in winter compared to summer and increased with fire severity class for the first several years. Albedo perturbation increased linearly with time over the study period. Correlations between albedo perturbations and the vegetation densities were strongest with snags, and significant in all fire classes in both summer and winter (R < -0.92, p < 0.01). The resulting annual radiative forcing at the top of the atmosphere became more negative linearly at a rate of -0.86 W m-2 yr-1, reaching -15 W m-2 in year 15 after fire. This suggests that snags can be the dominant controller of postfire albedo on decadal time scales.

  10. Temperature rise and safety considerations for radiation force ultrasound imaging

    NASA Astrophysics Data System (ADS)

    Herman, Bruce A.; Harris, Gerald R.

    2002-11-01

    Current models for estimating temperature increase during ultrasound exposure calculate the steady-state rise, using time-averaged acoustic output, as the worst case for safety consideration. While valid for the typically very short (microsecond) pulses used by conventional diagnostic techniques, this analysis does not necessarily correspond to a worst case scenario for the longer pulses or pulse bursts used by a new method, radiation force imaging. Radiation force imaging, employing ultrasound pulse durations up to hundreds of milliseconds, produces and detects motion in solid tissue or acoustic streaming in fluids via a high intensity beam. Models that calculate the transient temperature rise from these pulses are developed for both the bone at focus and soft tissue cases. Based on accepted time-temperature dose criteria, it is shown that for pulse lengths and intensities utilized by this technique, temperature may increase to levels that raise safety concerns for bone at the focus of the ultrasound beam. Also, the impact on this modality of the current U.S. Food and Drug Administration output limits for diagnostic ultrasound devices is discussed.

  11. Radiative forcing in the ACCMIP historical and future climate simulations

    SciTech Connect

    Shindell, D. T.; Lamarque, J. -F.; Schulz, M.; Flanner, M.; Jiao, C.; Chin, M.; Young, P. J.; Lee, Y. H.; Rotstayn, L.; Mahowald, N.; Milly, G.; Faluvegi, G.; Balkanski, Y.; Collins, W. J.; Conley, A. J.; Dalsoren, S.; Easter, R.; Ghan, S.; Horowitz, L.; Liu, X.; Myhre, G.; Nagashima, T.; Naik, V.; Rumbold, S. T.; Skeie, R.; Sudo, K.; Szopa, S.; Takemura, T.; Voulgarakis, A.; Yoon, J. -H.; Lo, F.

    2013-01-01

    The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) examined the short-lived drivers of climate change in current climate models. Here we evaluate the 10 ACCMIP models that included aerosols, 8 of which also participated in the Coupled Model Intercomparison Project phase 5 (CMIP5). The models reproduce present-day total aerosol optical depth (AOD) relatively well, though many are biased low. Contributions from individual aerosol components are quite different, however, and most models underestimate east Asian AOD. The models capture most 1980-2000 AOD trends well, but underpredict increases over the Yellow/Eastern Sea. They strongly underestimate absorbing AOD in many regions. We examine both the direct radiative forcing (RF) and the forcing including rapid adjustments (effective radiative forcing; ERF, including direct and indirect effects). The models’ all-sky 1850 to 2000 global mean annual average total aerosol RF is (mean; range) -0.26Wm-2-2. Screening based on model skill in capturing observed AOD yields a best estimate of -0.42Wm-2-2-2-2forcing than direct RF. Despite this, the multi-model spread relative to the mean is typically the same for ERF as it is for RF, or even smaller, over areas with substantial forcing. The largest 1850 to 2000 negative aerosol RF and ERF values are over and near Europe, south and east Asia and North America. ERF, however, is positive over the Sahara, the Karakoram, high Southern latitudes and especially the Arctic. Global

  12. Contrasting regional versus global radiative forcing by megacity pollution emissions

    NASA Astrophysics Data System (ADS)

    Dang, H.; Unger, N.

    2015-10-01

    We assess the regional and global integrated radiative forcing on 20- and 100-year time horizons caused by a one-year pulse of present day pollution emissions from 10 megacity areas: Los Angeles, Mexico City, New York City, Sao Paulo, Lagos, Cairo, New Delhi, Beijing, Shanghai and Manila. The assessment includes well-mixed greenhouse gases: carbon dioxide (CO2), nitrous oxide (N2O), methane (CH4); and short-lived climate forcers: tropospheric ozone (O3) and fine mode aerosol particles (sulfate, nitrate, black carbon, primary and secondary organic aerosol). All megacities contribute net global warming on both time horizons. Most of the 10 megacity areas exert a net negative effect on their own regional radiation budget that is 10-100 times larger in magnitude than their global radiative effects. Of the cities examined, Beijing, New Delhi, Shanghai and New York contribute most to global warming with values ranging from +0.03 to 0.05 Wm-2yr on short timescales and +0.07-0.10 Wm-2yr on long timescales. Regional net 20-year radiative effects are largest for Mexico City (-0.84 Wm-2yr) and Beijing (-0.78 Wm-2yr). Megacity reduction of non-CH4 O3 precursors to improve air quality offers zero co-benefits to global climate. Megacity reduction of aerosols to improve air quality offers co-benefits to the regional radiative budget but minimal or no co-benefits to global climate with the exception of black carbon reductions in a few cities, especially Beijing and New Delhi. Results suggest that air pollution and global climate change mitigation can be treated as separate environmental issues in policy at the megacity level with the exception of CH4 action. Individual megacity reduction of CO2 and CH4 emissions can mitigate global warming and therefore offers climate safety improvements to the entire planet.

  13. Radiation Force Caused by Scattering, Absorption, and Emission of Light by Nonspherical Particles

    NASA Technical Reports Server (NTRS)

    Mishchenko, Michael I.; Hansen, James E. (Technical Monitor)

    2001-01-01

    General formulas for computing the radiation force exerted on arbitrarily oriented and arbitrarily shaped nonspherical particles due to scattering, absorption, and emission of electromagnetic radiation are derived. For randomly oriented particles with a plane of symmetry, the formula for the average radiation force caused by the particle response to external illumination reduces to the standard Debye formula derived from the Lorenz-Mie theory, whereas the average radiation force caused by emission vanishes.

  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. Radiative Forcing in the ACCMIP Historical and Future Climate Simulations

    NASA Technical Reports Server (NTRS)

    Shindell, Drew Todd; Lamarque, J.-F.; Schulz, M.; Flanner, M.; Jiao, C.; Chin, M.; Young, P. J.; Lee, Y. H.; Rotstayn, L.; Mahowald, N.; Milly, G.; Faluvegi, G.; Balkanski, Y.; Collins, W. J.; Conley, A. J.; Dalsoren, S.; Easter, R.; Ghan, S.; Horowitz, L.; Liu, X.; Myhre, G.; Nagashima, T.; Naik, V.; Rumbold, S. T.; Skeie, R.; Voulgarakis, A.

    2013-01-01

    A primary goal of the Atmospheric Chemistry and Climate Model IntercomparisonProject (ACCMIP) was to characterize the short-lived drivers of preindustrial to 2100climate change in the current generation of climate models. Here we evaluate historicaland 5 future radiative forcing in the 10 ACCMIP models that included aerosols, 8 of whichalso participated in the Coupled Model Intercomparison Project phase 5 (CMIP5).The models generally reproduce present-day climatological total aerosol opticaldepth (AOD) relatively well. components to this total, however, and most appear to underestimate AOD over East10 Asia. The models generally capture 1980-2000 AOD trends fairly well, though theyunderpredict AOD increases over the YellowEastern Sea. They appear to strongly underestimate absorbing AOD, especially in East Asia, South and Southeast Asia, SouthAmerica and Southern Hemisphere Africa.We examined both the conventional direct radiative forcing at the tropopause (RF) and the forcing including rapid adjustments (adjusted forcing AF, including direct andindirect effects). The models calculated all aerosol all-sky 1850 to 2000 global meanannual average RF ranges from 0.06 to 0.49 W m(sup -2), with a mean of 0.26 W m(sup -2) and a median of 0.27 W m(sup -2. Adjusting for missing aerosol components in some modelsbrings the range to 0.12 to 0.62W m(sup -2), with a mean of 0.39W m(sup -2). Screen20ing the models based on their ability to capture spatial patterns and magnitudes ofAOD and AOD trends yields a quality-controlled mean of 0.42W m(sup -2) and range of0.33 to 0.50 W m(sup -2) (accounting for missing components). The CMIP5 subset of ACCMIPmodels spans 0.06 to 0.49W m(sup -2), suggesting some CMIP5 simulations likelyhave too little aerosol RF. A substantial, but not well quantified, contribution to histori25cal aerosol RF may come from climate feedbacks (35 to 58). The mean aerosol AF during this period is 1.12W m(sup -2) (median value 1.16W m(sup -2), range 0.72 to1.44W m

  16. Analysis of clot formation with acoustic radiation force

    NASA Astrophysics Data System (ADS)

    Viola, Francesco; Longo, Diane M.; Lawrence, Michael B.; Walker, William F.

    2002-04-01

    Inappropriate blood coagulation plays an important role in diseases including stroke, heart attack, and deep vein thrombosis (DVT). DVT arises when a blood clot forms in a large vein of the leg. DVT is detrimental because the blood flow may be partially or completely obstructed. More importantly, a potentially fatal situation may arise if part of the clot travels to the arteries in the lungs, forming a pulmonary embolism (PE). Characterization of the mechanical properties of DVT could improve diagnosis and suggest appropriate treatment. We are developing a technique to assess mechanical properties of forming thrombi. The technique uses acoustic radiation force as a means to produce small, localized displacements within the sample. Returned ultrasound echoes are processed to estimate the time dependent displacement of the sample. Appropriate mechanical modeling and signal processing produce plots depicting relative mechanical properties (relative elasticity and relative viscosity) and force-free parameters (time constant, damping ratio, and natural frequency). We present time displacement curves of blood samples obtained during coagulation, and show associated relative and force-free parameter plots. These results show that the Voigt model with added mass accurately characterizes blood behavior during clot formation.

  17. 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.

  18. Toward Standardized Acoustic Radiation Force (ARF)-Based Ultrasound Elasticity Measurements With Robotic Force Control

    PubMed Central

    Kumar, Shalki; Lily, Kuo; Sen, H. Tutkun; Iordachita, Iulian; Kazanzides, Peter

    2016-01-01

    Objective Acoustic radiation force (ARF)-based approaches to measure tissue elasticity require transmission of a focused high-energy acoustic pulse from a stationary ultrasound probe and ultrasound-based tracking of the resulting tissue displacements to obtain stiffness images or shear wave speed estimates. The method has established benefits in biomedical applications such as tumor detection and tissue fibrosis staging. One limitation, however, is the dependence on applied probe pressure, which is difficult to control manually and prohibits standardization of quantitative measurements. To overcome this limitation, we built a robot prototype that controls probe contact forces for shear wave speed quantification. Methods The robot was evaluated with controlled force increments applied to a tissue-mimicking phantom and in vivo abdominal tissue from three human volunteers. Results The root-mean-square error between the desired and measured forces was 0.07 N in the phantom and higher for the fatty layer of in vivo abdominal tissue. The mean shear wave speeds increased from 3.7 to 4.5 m/s in the phantom and 1.0 to 3.0 m/s in the in vivo fat for compressive forces ranging from 2.5 to 30 N. The standard deviation of shear wave speeds obtained with the robotic approach were low in most cases (< 0.2 m/s) and comparable to that obtained with a semiquantitative landmark-based method. Conclusion Results are promising for the introduction of robotic systems to control the applied probe pressure for ARF-based measurements of tissue elasticity. Significance This approach has potential benefits in longitudinal studies of disease progression, comparative studies between patients, and large-scale multidimensional elasticity imaging. PMID:26552071

  19. Acoustic radiation force and torque on an absorbing compressible particle in an inviscid fluid.

    PubMed

    Silva, Glauber T

    2014-11-01

    Exact formulas of the acoustic radiation force and torque exerted by an arbitrary time-harmonic wave on an absorbing compressible particle that is suspended in an inviscid fluid are presented. It is considered that the particle diameter is much smaller than the incident wavelength, i.e., the so-called Rayleigh scattering limit. Moreover, the particle absorption assumed here is due to the attenuation of compressional waves only. Shear waves inside and outside the particle are neglected, since the inner and outer viscous boundary layer of the particle are supposed to be much smaller than the particle radius. The obtained radiation force formulas are used to establish the trapping conditions of a particle by a single-beam acoustical tweezer based on a spherically focused ultrasound transducer. In this case, it is shown that the particle absorption has a pivotal role in single-beam trapping at the transducer focal region. Furthermore, it is found that only the first-order Bessel vortex beam can generate the radiation torque on a small particle. In addition, numerical evaluation of the radiation force and torque exerted on a benzene and an olive oil droplet suspended in water are presented and discussed. PMID:25373943

  20. Implications of Representative Concentration Pathway 4.5 Methane Emissions to Stabilize Radiative Forcing

    SciTech Connect

    Emanuel, William R.; Janetos, Anthony C.

    2013-02-01

    Increases in the abundance of methane (CH4) in the Earth’s atmosphere are responsible for significant radiative forcing of climate change (Forster et al., 2007; Wuebbles and Hayhoe, 2002). Since 1750, a 2.5 fold increase in atmospheric CH4 contributed 0.5 W/m2 to direct radiative forcing and an additional 0.2 W/m2 indirectly through changes in atmospheric chemistry. Next to water and carbon dioxide (CO2), methane is the most abundant greenhouse gas in the troposphere. Additionally, CH4 is significantly more effective as a greenhouse gas on a per molecule basis than is CO2, and increasing atmospheric CH4 has been second only to CO2 in radiative forcing (Forster et al., 2007). The chemical reactivity of CH4 is important to both tropospheric and stratospheric chemistry. Along with carbon monoxide, methane helps control the amount of the hydroxyl radical (OH) in the troposphere where oxidation of CH4 by OH leads to the formation of formaldehyde, carbon monoxide, and ozone.

  1. The effects of acoustic radiation force on contrast agents: Experimental and theoretial analysis

    NASA Astrophysics Data System (ADS)

    Dayton, Paul Alexander

    The goal of this research is to understand the response of ultrasound contrast agents to acoustic radiation force. Ultrasound contrast agents are encapsulated microbubbles similar in size and rheologic behavior to human erythrocytes. A core of either air or a high- molecular weight gas makes these microbubbles extremely compressible and highly echogenic. Clinically, the detection of blood is difficult without contrast agents because the echoes from blood cells are typically 30-40 dB less than tissue echoes. Ultrasound contrast agents have been shown to be extremely useful in assisting delineation of perfused tissue in echocardiography, and are being increasingly used for tumor detection in radiology. The high compressibility of gas-filled contrast agents makes these microbubbles susceptible to translation due to radiation force. Thus, it is important to understand the effects of this force in order to avoid erroneous measurements based on the location and flow velocity of microbubbles. In addition, the ability to displace and concentrate microbubbles may be an advantage in targeted imaging, targeted therapy, or industrial applications where it is desired to localize microbubbles in a region. In this study, experimental and theoretical tools are combined to investigate the interaction between microbubbles and an acoustic pulse. Several unique experimental systems allow visualization and analysis of the radius-time curves of individual microbubbles, the displacement of individual microbubbles in-vitro, and the displacement of microbubbles in-vivo. Theoretical analysis illustrates that the effect of radiation force on microbubbles is directly proportional to the product of the bubble volume and the acoustic pressure gradient. A model designed to simulate the radius-time behavior of individual microbubbles is verified from experimental data, and used to estimate the magnitude of radiation force. The resulting bubble translation is determined using a second model

  2. 47 CFR 15.215 - Additional provisions to the general radiated emission limitations.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... RADIO FREQUENCY DEVICES Intentional Radiators Radiated Emission Limits, Additional Provisions § 15.215... 15.257 provide alternatives to the general radiated emission limits for intentional radiators... § 15.209. In no case shall the level of the unwanted emissions from an intentional radiator...

  3. 47 CFR 15.215 - Additional provisions to the general radiated emission limitations.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... RADIO FREQUENCY DEVICES Intentional Radiators Radiated Emission Limits, Additional Provisions § 15.215... 15.257 provide alternatives to the general radiated emission limits for intentional radiators... § 15.209. In no case shall the level of the unwanted emissions from an intentional radiator...

  4. 47 CFR 15.215 - Additional provisions to the general radiated emission limitations.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... RADIO FREQUENCY DEVICES Intentional Radiators Radiated Emission Limits, Additional Provisions § 15.215... 15.257 provide alternatives to the general radiated emission limits for intentional radiators... § 15.209. In no case shall the level of the unwanted emissions from an intentional radiator...

  5. 47 CFR 15.215 - Additional provisions to the general radiated emission limitations.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... RADIO FREQUENCY DEVICES Intentional Radiators Radiated Emission Limits, Additional Provisions § 15.215... 15.257 provide alternatives to the general radiated emission limits for intentional radiators... § 15.209. In no case shall the level of the unwanted emissions from an intentional radiator...

  6. 47 CFR 15.215 - Additional provisions to the general radiated emission limitations.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... RADIO FREQUENCY DEVICES Intentional Radiators Radiated Emission Limits, Additional Provisions § 15.215... 15.257 provide alternatives to the general radiated emission limits for intentional radiators... § 15.209. In no case shall the level of the unwanted emissions from an intentional radiator...

  7. Characterizing the stiffness of Human Prostates using Acoustic Radiation Force

    PubMed Central

    Zhai, Liang; Madden, John; Foo, Wen-Chi; Mouraviev, Vladimir; Polascik, Thomas J.; Palmeri, Mark L.; Nightingale, Kathryn R.

    2012-01-01

    Acoustic Radiation Force Impulse (ARFI) imaging has been previously reported to portray normal anatomic structures and pathologies in ex vivo human prostates with good contrast and resolution. These findings were based on comparison with histological slides and McNeal’s zonal anatomy. In ARFI images, the central zone (CZ) appears darker (smaller displacement) than other anatomic zones, and prostate cancer (PCa) is darker than normal tissue in the peripheral zone (PZ). Since displacement amplitudes in ARFI images are determined by both the underlying tissue stiffness and the amplitude of acoustic radiation force which varies with acoustic attenuation, one question that arises is: how are the relative displacements in prostate ARFI images related to the underlying prostatic tissue stiffness? In linear, isotropic elastic materials and in tissues that are relatively uniform in acoustic attenuation (e.g. liver), relative displacement in ARFI images has been shown to be correlated with underlying tissue stiffness. However, the prostate is known to be heterogeneous. Variations in acoustic attenuation of prostatic structures could confound the interpretation of ARFI images due to the associated variations in the applied acoustic radiation force. Therefore, in this study, co-registered three-dimensional (3D) ARFI datasets and quantitative shear wave elasticity imaging (SWEI) datasets were acquired in freshly excised human prostates to investigate the relationship between displacement amplitudes in ARFI prostate images and the matched reconstructed shear moduli. The lateral time-to-peak (LTTP) algorithm was applied to the SWEI data to compute the shear wave speed and reconstruct the shear moduli. Five types of prostatic tissue (PZ, CZ, transition zone (TZ) and benign prostatic hyperplasia (BPH), PCa, and atrophy) were identified, whose shear moduli were quantified to be 4.1±0.8 kPa, 9.9±0.9 kPa, 4.8±0.6 kPa, 10.0±1.0 kPa and 8.0 kPa, respectively. Linear regression was

  8. Identifying Vulnerable Plaques with Acoustic Radiation Force Impulse Imaging

    NASA Astrophysics Data System (ADS)

    Doherty, Joshua Ryan

    The rupture of arterial plaques is the most common cause of ischemic complications including stroke, the fourth leading cause of death and number one cause of long term disability in the United States. Unfortunately, because conventional diagnostic tools fail to identify plaques that confer the highest risk, often a disabling stroke and/or sudden death is the first sign of disease. A diagnostic method capable of characterizing plaque vulnerability would likely enhance the predictive ability and ultimately the treatment of stroke before the onset of clinical events. This dissertation evaluates the hypothesis that Acoustic Radiation Force Impulse (ARFI) imaging can noninvasively identify lipid regions, that have been shown to increase a plaque's propensity to rupture, within carotid artery plaques in vivo. The work detailed herein describes development efforts and results from simulations and experiments that were performed to evaluate this hypothesis. To first demonstrate feasibility and evaluate potential safety concerns, finite- element method simulations are used to model the response of carotid artery plaques to an acoustic radiation force excitation. Lipid pool visualization is shown to vary as a function of lipid pool geometry and stiffness. A comparison of the resulting Von Mises stresses indicates that stresses induced by an ARFI excitation are three orders of magnitude lower than those induced by blood pressure. This thesis also presents the development of a novel pulse inversion harmonic tracking method to reduce clutter-imposed errors in ultrasound-based tissue displacement estimates. This method is validated in phantoms and was found to reduce bias and jitter displacement errors for a marked improvement in image quality in vivo. Lastly, this dissertation presents results from a preliminary in vivo study that compares ARFI imaging derived plaque stiffness with spatially registered composition determined by a Magnetic Resonance Imaging (MRI) gold standard

  9. Retrievals of Dust and Black Carbon Radiative Forcing in Snow using Imaging Spectroscopy

    NASA Astrophysics Data System (ADS)

    Seidel, F. C.; Painter, T.; Bryant, A. C.; Skiles, M.; Rittger, K. E.

    2012-12-01

    The reduction of snow albedo due to impurities of dust and black carbon provides an additional energy flux into a snowpack. This positive radiative forcing accelerates snowmelt, reduces snow cover duration and water runoff. Extensive information in time and space on dust and black carbon radiative forcing in snow are therefore required to model and predict water availability from snow and ice reservoirs. We present a novel processing chain to retrieve dust and black carbon radiative forcing in snow from orthorectified remote sensing data. We use JPL's classic version of the Airborne Visible / Infrared Imaging Spectrometer (AVIRIS) to measure upwelling solar radiance at the sensor level. The first stage of processing comprises the modeling and compensation for atmospheric and topographic influences on the AVIRIS data. The resulting directional surface reflectance factor is used to determine snow cover and to retrieve the snow grain size distribution. The latter requires a simple inversion strategy using a look up table with pre-calculated values of spectral ice absorption features, which depend to the first order on the snow grain size. Spectral snow albedo is determined by generalizing the directional snow surface spectral reflectance with the anisotropy factor given by the bidirectional reflectance distribution function. The integration over the visible spectral range of solar light yields the broadband snow albedo. The difference of the latter with a modeled clean snow albedo multiplied by the irradiance provides the spatial distribution of the radiative forcing in snow. In addition, we validate the spectral irradiance and directional surface reflectance of snow against independent in-situ reference observations in the Senator Beck Basin Study Area, Upper Colorado River Basin, San Juan Mountains, Colorado, USA. The results indicate that the products derived from AVIRIS data enable us to retrieve and monitor quantitative snow surface properties relevant to

  10. Solar Radiation as Driving Force In Early Evolution

    NASA Technical Reports Server (NTRS)

    Rothschild, Lynn J.; Peterson, David L. (Technical Monitor)

    2002-01-01

    Ultraviolet radiation (UVR) has provided an evolutionary challenge to life on Earth in that it is both an agent of mutation and as well as a selective force. Today surface fluxes of UVR vary diurnally, seasonally, etc. Still, the UVR flux was probably substantially higher during the early phases of evolution, suggesting that its role in evolution was even more prominent during this time. In this presentation, the creative role of UVR in evolution is discussed, specifically in connection with the role that UVR may have played in the evolution of early microbial ecosystems. The presentation will include discussions of the direct influence of UVR on such processes as photosynthesis and genetic damage, as well as the indirect influence of UVR as mediated through the production of reactive oxygen species. These biological effects of UVR will be viewed against the backdrop of the physical nature of the early Earth, surely a very different place then than now.

  11. Radiation pressure force from optical cycling on a polyatomic molecule

    NASA Astrophysics Data System (ADS)

    Kozyryev, Ivan; Baum, Louis; Matsuda, Kyle; Hemmerling, Boerge; Doyle, John M.

    2016-07-01

    We demonstrate multiple photon cycling and radiative force deflection on the triatomic free radical strontium monohydroxide (SrOH). Optical cycling is achieved on SrOH in a cryogenic buffer-gas beam by employing the rotationally closed P(N\\prime\\prime =1) branch of the vibronic transition {\\tilde{X}}2{{{Σ }}}+(000)≤ftrightarrow {\\tilde{A}}2{{{\\Pi }}}1/2(000). A single repumping laser excites the Sr–O stretching vibrational mode, and photon cycling of the molecule deflects the SrOH beam by an angle of 0.2^\\circ via scattering of ∼100 photons per molecule. This approach can be used for direct laser cooling of SrOH and more complex, isoelectronic species.

  12. Acoustic Radiation Force Impulse (ARFI) Imaging-Based Needle Visualization

    PubMed Central

    Rotemberg, Veronica; Palmeri, Mark; Rosenzweig, Stephen; Grant, Stuart; Macleod, David; Nightingale, Kathryn

    2011-01-01

    Ultrasound-guided needle placement is widely used in the clinical setting, particularly for central venous catheter placement, tissue biopsy and regional anesthesia. Difficulties with ultrasound guidance in these areas often result from steep needle insertion angles and spatial offsets between the imaging plane and the needle. Acoustic Radiation Force Impulse (ARFI) imaging leads to improved needle visualization because it uses a standard diagnostic scanner to perform radiation force based elasticity imaging, creating a displacement map that displays tissue stiffness variations. The needle visualization in ARFI images is independent of needle-insertion angle and also extends needle visibility out of plane. Although ARFI images portray needles well, they often do not contain the usual B-mode landmarks. Therefore, a three-step segmentation algorithm has been developed to identify a needle in an ARFI image and overlay the needle prediction on a coregistered B-mode image. The steps are: (1) contrast enhancement by median filtration and Laplacian operator filtration, (2) noise suppression through displacement estimate correlation coefficient thresholding and (3) smoothing by removal of outliers and best-fit line prediction. The algorithm was applied to data sets from horizontal 18, 21 and 25 gauge needles between 0–4 mm offset in elevation from the transducer imaging plane and to 18G needles on the transducer axis (in plane) between 10° and 35° from the horizontal. Needle tips were visualized within 2 mm of their actual position for both horizontal needle orientations up to 1.5 mm off set in elevation from the transducer imaging plane and on-axis angled needles between 10°–35° above the horizontal orientation. We conclude that segmented ARFI images overlaid on matched B-mode images hold promise for improved needle visibility in many clinical applications. PMID:21608445

  13. Quantifying immediate radiative forcing by black carbon and organic matter with the Specific Forcing Pulse

    NASA Astrophysics Data System (ADS)

    Bond, T. C.; Zarzycki, C.; Flanner, M. G.; Koch, D. M.

    2010-06-01

    We propose a measure to quantify climate warming or cooling by pollutants with atmospheric lifetimes of less than one year: the Specific Forcing Pulse (SFP). SFP is the amount of energy added to the Earth system per mass of pollutant emitted. Global average SFP for black carbon, including atmosphere and cryosphere, is 1.12 GJ g-1 and that for organic matter is -0.061 GJ g-1. We provide regional values for black carbon (BC) and organic matter (OM) emitted from 23 source-region combinations, divided between atmosphere and cryosphere impacts and identifying forcing by latitude. Regional SFP varies by about 40% for black carbon. This variation is relatively small because of compensating effects; particles from regions that affect ice albedo typically have shorter atmospheric lifetimes because of lower convection. The ratio between BC and OM SFP implies that, for direct forcing, an OM:BC mass ratio of 15 has a neutral effect on top-of-atmosphere direct forcing for any region, and any lower ratio induces direct warming. However, important processes, particularly cloud changes that tend toward cooling, have not been included here. We demonstrate ensemble adjustment, in which we produce a "best estimate" by combining a suite of diverse but simple models and enhanced models of greater complexity. Adjustments for black carbon internal mixing and for regional variability are discussed; regions with convection are implicated in greater model diversity. SFP expresses scientific uncertainty and separates it from policy uncertainty; the latter is caused by disagreements about the relevant time horizon, impact, or spatial scale of interest. However, metrics used in policy discussions, such as global warming potentials, are easily derived from SFP. Global-average SFP for biofuel and fossil fuel emissions translates to a 100-year GWP of about 760 for black carbon and -40 for organic matter when snow forcing is included. Ensemble-adjusted estimates of atmospheric radiative impact by

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. Effects Of Radiation On Electronics-Additional References

    NASA Technical Reports Server (NTRS)

    Bouquet, Frank L.

    1988-01-01

    Bibliography abstracts summarizing literature on effects of radiation on new electronic devices. This and second volume cover years 1984 and 1985. Third volume, covers 1982 and 1983 (previously published).

  19. Arctic stratospheric sulphur injections: radiative forcings and cloud responses

    NASA Astrophysics Data System (ADS)

    Lohmann, U.; Gasparini, B.; Miriam, K.; Kravitz, B.; Rasch, P. J.

    2014-12-01

    Observations and climate projections show a high sensitivity of the Arctic climate to the increase in greenhouse gas emissions, known as the polar amplification. This study evaluates the options of counteracting the rising polar temperatures by stratospheric sulphur injections in the Northern Hemisphere high latitudes.10 Mt of sulphur dioxide are emitted in a point emission source setup centred at the 100 hPa pressure level over Svalbard island (80°N,15°E). We perform simulations with the general circulation models ECHAM5, ECHAM6, and GISS ModelE. We study pulsed emission simulations that differ among themselves by the injection starting date (March-September), injection length (1, 30, or 90 day emission period), and the vertical resolution of the model (for ECHAM6). We find injections in April to be the most efficient in terms of the shortwave radiative forcing at the top-of-the atmosphere over the Arctic region. The distribution of sulphate aerosol spreads out beyond the injection region, with a significant share reaching the Southern Hemisphere. Results from ModelE show high latitude injections could counteract the spring and summer temperature increase due to higher atmospheric CO2 concentrations. Preliminary results with a more realistic description of clouds in ECHAM-HAM reveal a complex pattern of responses, most notably: a decrease in Northern Hemisphere cirrus clouds strengthening the effect of stratospheric aerosols in ECHAM5 a decrease in low-level clouds over the Arctic increasing the incoming solar radiation and causing a net positive radiative balance cirrus clouds are resilient to stratospheric sulphur injections in the absence of sulphate warming

  20. Non-additivity of molecule-surface van der Waals potentials from force measurements

    NASA Astrophysics Data System (ADS)

    Tautz, Stefan

    2014-03-01

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Their description as an inherently quantum mechanical phenomenon was developed for single atoms and homogeneous macroscopic bodies by London, Casimir, and Lifshitz. For intermediate-sized objects like organic molecules an atomistic description is required, but explicit first principles calculations are very difficult since correlations between many interacting electrons have to be considered. Hence, semi-empirical correction schemes are often used that simplify the vdW interaction to a sum over atom-pair potentials. A similar gap exists between successful measurements of vdW and Casimir forces for single atoms on the one hand and macroscopic bodies on the other, as comparable experiments for molecules are absent. I will present experiments in which long-range vdW potentials between a series of related molecules and a metal surface have been determined experimentally. The experiments rely on the extremely sensitive force detection of an atomic force microscope in combination with its molecular manipulation capabilities. The results allow us to confirm the asymptotic force law and to quantify the non-additive part of the vdW interaction which is particularly challenging for theory. In the present case, cooperative effects account for 10% of the total interaction. This effect is of general validity in molecules and thus relevant at the intersection of chemistry, physics, biology, and materials science.

  1. Matching of additive and polarizable force fields for multiscale condensed phase simulations

    PubMed Central

    Baker, Christopher M.; Best, Robert B.

    2013-01-01

    Inclusion of electronic polarization effects is one of the key aspects in which the accuracy of current biomolecular force fields may be improved. The principal drawback of such approaches is the computational cost, which typically ranges from 3 – 10 times that of the equivalent additive model, and may be greater for more sophisticated treatments of polarization or other many-body effects. Here, we present a multiscale approach which may be used to enhance the sampling in simulations with polarizable models, by using the additive model as a tool to explore configuration space. We use a method based on information theory to determine the charges for an additive model that has optimal overlap with the polarizable one, and we demonstrate the feasibility of enhancing sampling via a hybrid replica exchange scheme for several model systems. An additional advantage is that, in the process, we obtain a systematic method for deriving charges for an additive model that will be the natural complement to its polarizable parent. The additive charges are found by an effective coarse-graining of the polarizable force field, rather than by ad hoc procedures. PMID:23997691

  2. Aerosol Radiative Forcing over North India during Pre-Monsoon Season using WRF-Chem

    NASA Astrophysics Data System (ADS)

    Misra, A.; Kumar, K.; Michael, M.; Tripathi, S. N.

    2013-12-01

    Study of aerosols is important for a fair understanding of the Earth climate system. This requires knowledge of the physical, chemical, optical, and morphological properties of aerosols. Aerosol radiative forcing provides information on the effect of aerosols on the Earth radiation budget. Radiative forcing estimates using model data provide an opportunity to examine the contribution of individual aerosol species to overall radiative forcing. We have used Weather Research and Forecast with Online Chemistry (WRF-Chem) derived aerosol concentration data to compute aerosol radiative forcing over north India during pre-monsoon season of 2008, 2009, and 2010. WRF-Chem derived mass concentrations are converted to number concentrations using standard procedure. Optical Properties of Aerosol and Cloud (OPAC) software package is used to compute extinction and scattering coefficients, and asymmetry parameter. Computations are performed at different altitudes and the obtained values are integrated to get the column optical properties. Santa Barbara Discrete Ordinate Radiative Transfer (SBDART) model is used to calculate the radiative forcing at surface and top-of-atmosphere. Higher values of aerosol radiative forcing are observed over desert region in western Indian state of Rajasthan, and Punjab of Pakistan. Contribution of individual aerosol species to atmospheric radiative forcing is also assessed. Dust radiative forcing is high over western India. Radiative forcing due to BC and water-soluble (WASO) aerosols are higher over north-west Indian states of Punjab and Haryana, and the Indo-Gangetic Basin. A pool of high WASO optical depth and radiative forcing is observed over the Indo-Bangladesh border. The findings of aerosol optical depth and radiative forcing are consistent with the geography and prevailing aerosol climatology of various regions. Heating rate profiles due to total aerosols and only due to BC have been evaluated at selected stations in north India. They show

  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. 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

  5. Lorentz force correction to the Boltzmann radiation transport equation and its implications for Monte Carlo algorithms

    NASA Astrophysics Data System (ADS)

    Bouchard, Hugo; Bielajew, Alex

    2015-07-01

    To establish a theoretical framework for generalizing Monte Carlo transport algorithms by adding external electromagnetic fields to the Boltzmann radiation transport equation in a rigorous and consistent fashion. Using first principles, the Boltzmann radiation transport equation is modified by adding a term describing the variation of the particle distribution due to the Lorentz force. The implications of this new equation are evaluated by investigating the validity of Fano’s theorem. Additionally, Lewis’ approach to multiple scattering theory in infinite homogeneous media is redefined to account for the presence of external electromagnetic fields. The equation is modified and yields a description consistent with the deterministic laws of motion as well as probabilistic methods of solution. The time-independent Boltzmann radiation transport equation is generalized to account for the electromagnetic forces in an additional operator similar to the interaction term. Fano’s and Lewis’ approaches are stated in this new equation. Fano’s theorem is found not to apply in the presence of electromagnetic fields. Lewis’ theory for electron multiple scattering and moments, accounting for the coupling between the Lorentz force and multiple elastic scattering, is found. However, further investigation is required to develop useful algorithms for Monte Carlo and deterministic transport methods. To test the accuracy of Monte Carlo transport algorithms in the presence of electromagnetic fields, the Fano cavity test, as currently defined, cannot be applied. Therefore, new tests must be designed for this specific application. A multiple scattering theory that accurately couples the Lorentz force with elastic scattering could improve Monte Carlo efficiency. The present study proposes a new theoretical framework to develop such algorithms.

  6. Lorentz force correction to the Boltzmann radiation transport equation and its implications for Monte Carlo algorithms.

    PubMed

    Bouchard, Hugo; Bielajew, Alex

    2015-07-01

    To establish a theoretical framework for generalizing Monte Carlo transport algorithms by adding external electromagnetic fields to the Boltzmann radiation transport equation in a rigorous and consistent fashion. Using first principles, the Boltzmann radiation transport equation is modified by adding a term describing the variation of the particle distribution due to the Lorentz force. The implications of this new equation are evaluated by investigating the validity of Fano's theorem. Additionally, Lewis' approach to multiple scattering theory in infinite homogeneous media is redefined to account for the presence of external electromagnetic fields. The equation is modified and yields a description consistent with the deterministic laws of motion as well as probabilistic methods of solution. The time-independent Boltzmann radiation transport equation is generalized to account for the electromagnetic forces in an additional operator similar to the interaction term. Fano's and Lewis' approaches are stated in this new equation. Fano's theorem is found not to apply in the presence of electromagnetic fields. Lewis' theory for electron multiple scattering and moments, accounting for the coupling between the Lorentz force and multiple elastic scattering, is found. However, further investigation is required to develop useful algorithms for Monte Carlo and deterministic transport methods. To test the accuracy of Monte Carlo transport algorithms in the presence of electromagnetic fields, the Fano cavity test, as currently defined, cannot be applied. Therefore, new tests must be designed for this specific application. A multiple scattering theory that accurately couples the Lorentz force with elastic scattering could improve Monte Carlo efficiency. The present study proposes a new theoretical framework to develop such algorithms. PMID:26061045

  7. Non-additivity of molecule-surface van der Waals potentials from force measurements

    NASA Astrophysics Data System (ADS)

    Wagner, Christian; Fournier, Norman; Ruiz, Victor G.; Li, Chen; Müllen, Klaus; Rohlfing, Michael; Tkatchenko, Alexandre; Temirov, Ruslan; Tautz, F. Stefan

    2014-11-01

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Despite being weak on an atomic level, they substantially influence molecular and biological systems due to their long range and system-size scaling. The difficulty to isolate and measure vdW forces on a single-molecule level causes our present understanding to be strongly theory based. Here we show measurements of the attractive potential between differently sized organic molecules and a metal surface using an atomic force microscope. Our choice of molecules and the large molecule-surface separation cause this attraction to be purely of vdW type. The experiment allows testing the asymptotic vdW force law and its validity range. We find a superlinear growth of the vdW attraction with molecular size, originating from the increased deconfinement of electrons in the molecules. Because such non-additive vdW contributions are not accounted for in most first-principles or empirical calculations, we suggest further development in that direction.

  8. Non-additivity of molecule-surface van der Waals potentials from force measurements

    PubMed Central

    Wagner, Christian; Fournier, Norman; Ruiz, Victor G.; Li, Chen; Müllen, Klaus; Rohlfing, Michael; Tkatchenko, Alexandre; Temirov, Ruslan; Tautz, F. Stefan

    2014-01-01

    Van der Waals (vdW) forces act ubiquitously in condensed matter. Despite being weak on an atomic level, they substantially influence molecular and biological systems due to their long range and system-size scaling. The difficulty to isolate and measure vdW forces on a single-molecule level causes our present understanding to be strongly theory based. Here we show measurements of the attractive potential between differently sized organic molecules and a metal surface using an atomic force microscope. Our choice of molecules and the large molecule-surface separation cause this attraction to be purely of vdW type. The experiment allows testing the asymptotic vdW force law and its validity range. We find a superlinear growth of the vdW attraction with molecular size, originating from the increased deconfinement of electrons in the molecules. Because such non-additive vdW contributions are not accounted for in most first-principles or empirical calculations, we suggest further development in that direction. PMID:25424490

  9. Experimental study of acoustic radiation force of an ultrasound beam on absorbing and scattering objects

    SciTech Connect

    Nikolaeva, Anastasiia V. Kryzhanovsky, Maxim A.; Tsysar, Sergey A.; Kreider, Wayne; Sapozhnikov, Oleg A.

    2015-10-28

    Acoustic radiation force is a nonlinear acoustic effect caused by the transfer of wave momentum to absorbing or scattering objects. This phenomenon is exploited in modern ultrasound metrology for measurement of the acoustic power radiated by a source and is used for both therapeutic and diagnostic sources in medical applications. To calculate radiation force an acoustic hologram can be used in conjunction with analytical expressions based on the angular spectrum of the measured field. The results of an experimental investigation of radiation forces in two different cases are presented in this paper. In one case, the radiation force of an obliquely incident ultrasound beam on a large absorber (which completely absorbs the beam) is considered. The second case concerns measurement of the radiation force on a spherical target that is small compared to the beam diameter.

  10. Experimental Study of Acoustic Radiation Force of an Ultrasound Beam on Absorbing and Scattering Objects

    PubMed Central

    Nikolaeva, Anastasiia V.; Kryzhanovsky, Maxim A.; Tsysar, Sergey A.; Kreider, Wayne; Sapozhnikov, Oleg A.

    2016-01-01

    Acoustic radiation force is a nonlinear acoustic effect caused by the transfer of wave momentum to absorbing or scattering objects. This phenomenon is exploited in modern ultrasound metrology for measurement of the acoustic power radiated by a source and is used for both therapeutic and diagnostic sources in medical applications. To calculate radiation force an acoustic hologram can be used in conjunction with analytical expressions based on the angular spectrum of the measured field. The results of an experimental investigation of radiation forces in two different cases are presented in this paper. In one case, the radiation force of an obliquely incident ultrasound beam on a large absorber (which completely absorbs the beam) is considered. The second case concerns measurement of the radiation force on a spherical target that is small compared to the beam diameter. PMID:27147775

  11. Experimental study of acoustic radiation force of an ultrasound beam on absorbing and scattering objects

    NASA Astrophysics Data System (ADS)

    Nikolaeva, Anastasiia V.; Kryzhanovsky, Maxim A.; Tsysar, Sergey A.; Kreider, Wayne; Sapozhnikov, Oleg A.

    2015-10-01

    Acoustic radiation force is a nonlinear acoustic effect caused by the transfer of wave momentum to absorbing or scattering objects. This phenomenon is exploited in modern ultrasound metrology for measurement of the acoustic power radiated by a source and is used for both therapeutic and diagnostic sources in medical applications. To calculate radiation force an acoustic hologram can be used in conjunction with analytical expressions based on the angular spectrum of the measured field. The results of an experimental investigation of radiation forces in two different cases are presented in this paper. In one case, the radiation force of an obliquely incident ultrasound beam on a large absorber (which completely absorbs the beam) is considered. The second case concerns measurement of the radiation force on a spherical target that is small compared to the beam diameter.

  12. The importance of the diurnal and annual cycle of air traffic for contrail radiative forcing

    NASA Astrophysics Data System (ADS)

    Stuber, Nicola; Forster, Piers; Rädel, Gaby; Shine, Keith

    2006-06-01

    Air traffic condensation trails, or contrails, are believed to have a net atmospheric warming effect, although one that is currently small compared to that induced by other sources of human emissions. However, the comparably large growth rate of air traffic requires an improved understanding of the resulting impact of aircraft radiative forcing on climate. Contrails have an effect on the Earth's energy balance similar to that of high thin ice clouds. Their trapping of outgoing longwave radiation emitted by the Earth and atmosphere (positive radiative forcing) is partly compensated by their reflection of incoming solar radiation (negative radiative forcing). On average, the longwave effect dominates and the net contrail radiative forcing is believed to be positive. Over daily and annual timescales, varying levels of air traffic, meteorological conditions, and solar insolation influence the net forcing effect of contrails. Here we determine the factors most important for contrail climate forcing using a sophisticated radiative transfer model for a site in southeast England, located in the entrance to the North Atlantic flight corridor. We find that night-time flights during winter (December to February) are responsible for most of the contrail radiative forcing. Night flights account for only 25 per cent of daily air traffic, but contribute 60 to 80 per cent of the contrail forcing. Further, winter flights account for only 22 per cent of annual air traffic, but contribute half of the annual mean forcing. These results suggest that flight rescheduling could help to minimize the climate impact of aviation.

  13. The importance of the diurnal and annual cycle of air traffic for contrail radiative forcing.

    PubMed

    Stuber, Nicola; Forster, Piers; Rädel, Gaby; Shine, Keith

    2006-06-15

    Air traffic condensation trails, or contrails, are believed to have a net atmospheric warming effect, although one that is currently small compared to that induced by other sources of human emissions. However, the comparably large growth rate of air traffic requires an improved understanding of the resulting impact of aircraft radiative forcing on climate. Contrails have an effect on the Earth's energy balance similar to that of high thin ice clouds. Their trapping of outgoing longwave radiation emitted by the Earth and atmosphere (positive radiative forcing) is partly compensated by their reflection of incoming solar radiation (negative radiative forcing). On average, the longwave effect dominates and the net contrail radiative forcing is believed to be positive. Over daily and annual timescales, varying levels of air traffic, meteorological conditions, and solar insolation influence the net forcing effect of contrails. Here we determine the factors most important for contrail climate forcing using a sophisticated radiative transfer model for a site in southeast England, located in the entrance to the North Atlantic flight corridor. We find that night-time flights during winter (December to February) are responsible for most of the contrail radiative forcing. Night flights account for only 25 per cent of daily air traffic, but contribute 60 to 80 per cent of the contrail forcing. Further, winter flights account for only 22 per cent of annual air traffic, but contribute half of the annual mean forcing. These results suggest that flight rescheduling could help to minimize the climate impact of aviation. PMID:16778887

  14. Radiative forcing over the conterminous United States due to contemporary land cover land use albedo change

    NASA Astrophysics Data System (ADS)

    Barnes, C. A.; Roy, D. P.

    2009-04-01

    Land cover and land use (LCLU) change affects Earth surface properties including albedo that impose a radiative forcing on the climate. Recently available satellite derived LCLU change data for the conterminous United States (CONUS) are used to study the impact of LCLU change from 1973 to 2000 on surface albedo and radiative forcing for 61 ecoregions covering 73% of the CONUS. Mean monthly broadband Moderate Resolution Imaging Spectroradiometer snow and snow-free albedo values are derived from decadal Landsat 60m LCLU classification maps located within ecoregions using a stratified random sampling methodology. These data and European Center for Medium-Range Weather Forecasts incoming surface solar radiation reanalysis are used to estimate ecoregion estimates of LCLU induced albedo change and surface radiative forcing. The results illustrate that radiative forcing due to contemporary LCLU albedo change varies geographically in sign and magnitude, with the most positive radiative forcing due to conversion of agriculture to other LCLU types, and the most negative radiative forcing due to forest loss, with snow modifying the results. At the ecoregion level this magnitude of radiative forcing is not insignificant, being similar in magnitude to global radiative forcing estimates due to LCLU change during the twentieth century.

  15. Ultrasonic Measurement of Microdisplacement Induced by Acoustic Radiation Force

    NASA Astrophysics Data System (ADS)

    Nagaoka, Ryo; Izumi, Takuya; Komatsu, Yosuke; Kobayashi, Kazuto; Saijo, Yoshifumi

    2013-07-01

    Quantitative evaluation of human skin aging is achieved by measuring the viscoelasticity of the skin. In the present study, microdisplacement induced by acoustic radiation force (ARF) is quantitatively measured by high-frequency ultrasonography (HFUS) and the result is confirmed by laser-Doppler velocimetry (LDV). Poly(vinyl alcohol) (PVA) with 1% cellulose particles was used as the biological phantom. A concave piezoelectric zirconate titanate (PZT) transducer with a diameter and focal length of 3 cm was used as an applicator to generate ARF. Microdisplacement at each depth of PVA was measured by the phased tracking method at 100 MHz of ultrasound with a repetition rate of 2000 Hz. When 80 tone-burst pulses were applied, the displacement measured by HFUS was 9 µm and the same result was obtained by LDV. As the displacement at each depth of PVA is measurable using ARF and the HFUS system, the system could be applied to measuring the viscoelasticity of the layered structure of the human skin.

  16. Revisit on dynamic radiation forces induced by pulsed Gaussian beams.

    PubMed

    Wang, Li-Gang; Chai, Hai-Shui

    2011-07-18

    Motivated by the recent optical trapping experiments using ultra-short pulsed lasers [Opt. Express 18, 7554 (2010); Appl. Opt. 48, G33 (2009)], in this paper we have re-investigated the trapping effects of the pulsed radiation force (PRF), which is induced by a pulsed Gaussian beam acting on a Rayleigh dielectric sphere. Based on our previous model [Opt. Express 15, 10615 (2007)], we have considered the effects arisen from both the transverse and axial PRFs, which lead to the different behaviors of both velocities and displacements of a Rayleigh particle within a pulse duration. Our analysis shows that, for the small-sized Rayleigh particles, when the pulse has the large pulse duration, it might provide the three-dimensional optical trapping; and when the pulse has the short pulse duration, it only provides the two-dimensional optical trapping with the axial movement along the pulse propagation. When the particle is in the vacuum or in the situation with the very weak Brownian motion, the particle can always be trapped stably due to the particle's cumulative momentum transferred from the pulse, and only in this case the trapping effect is independent of pulse duration. Finally, we have predicted that for the large-sized Rayleigh particles, the pulse beam can only provide the two-dimensional optical trap (optical guiding). Our results provide the important information about the trapping mechanism of pulsed tweezers. PMID:21934801

  17. Addition Laws for Intensities of Radiation Emerging from Scattering Atmospheres Containing Energy Sources

    NASA Astrophysics Data System (ADS)

    Nikoghossian, A. G.; Kapanadze, N. G.

    2016-03-01

    A group theoretical approach is developed for solving astrophysical radiative transfer problems described in a previous series of papers. Addition laws for observed radiative intensities are derived for the case in which atmospheres not only absorb and scatter radiation incident on them, but radiate themselves because of energy sources contained within them. As an illustration of the application of these laws, several special radiative transfer problems which we believe are of practical interest are discussed.

  18. Direct weakening of tropical circulations from masked CO2 radiative forcing

    PubMed Central

    Merlis, Timothy M.

    2015-01-01

    Climate models robustly simulate weakened mean circulations of the tropical atmosphere in direct response to increased carbon dioxide (CO2). The direct response to CO2, defined by the response to radiative forcing in the absence of changes in sea surface temperature, affects tropical precipitation and tropical cyclone genesis, and these changes have been tied to the weakening of the mean tropical circulation. The mechanism underlying this direct CO2-forced circulation change has not been elucidated. Here, I demonstrate that this circulation weakening results from spatial structure in CO2’s radiative forcing. In regions of ascending circulation, such as the intertropical convergence zone, the CO2 radiative forcing is reduced, or “masked,” by deep-convective clouds and high humidity; in subsiding regions, such as the subtropics, the CO2 radiative forcing is larger because the atmosphere is drier and deep-convective clouds are infrequent. The spatial structure of the radiative forcing reduces the need for the atmosphere to transport energy. This, in turn, weakens the mass overturning of the tropical circulation. The previously unidentified mechanism is demonstrated in a hierarchy of atmospheric general circulation model simulations with altered radiative transfer to suppress the cloud masking of the radiative forcing. The mechanism depends on the climatological distribution of clouds and humidity, rather than uncertain changes in these quantities. Masked radiative forcing thereby offers an explanation for the robustness of the direct circulation weakening under increased CO2. PMID:26460034

  19. Direct weakening of tropical circulations from masked CO2 radiative forcing.

    PubMed

    Merlis, Timothy M

    2015-10-27

    Climate models robustly simulate weakened mean circulations of the tropical atmosphere in direct response to increased carbon dioxide (CO2). The direct response to CO2, defined by the response to radiative forcing in the absence of changes in sea surface temperature, affects tropical precipitation and tropical cyclone genesis, and these changes have been tied to the weakening of the mean tropical circulation. The mechanism underlying this direct CO2-forced circulation change has not been elucidated. Here, I demonstrate that this circulation weakening results from spatial structure in CO2's radiative forcing. In regions of ascending circulation, such as the intertropical convergence zone, the CO2 radiative forcing is reduced, or "masked," by deep-convective clouds and high humidity; in subsiding regions, such as the subtropics, the CO2 radiative forcing is larger because the atmosphere is drier and deep-convective clouds are infrequent. The spatial structure of the radiative forcing reduces the need for the atmosphere to transport energy. This, in turn, weakens the mass overturning of the tropical circulation. The previously unidentified mechanism is demonstrated in a hierarchy of atmospheric general circulation model simulations with altered radiative transfer to suppress the cloud masking of the radiative forcing. The mechanism depends on the climatological distribution of clouds and humidity, rather than uncertain changes in these quantities. Masked radiative forcing thereby offers an explanation for the robustness of the direct circulation weakening under increased CO2. PMID:26460034

  20. Uncertainties in Carbon Dioxide Radiative Forcing in Atmospheric General Circulation Models

    NASA Technical Reports Server (NTRS)

    Cess, R. D.; Zhang, M.-H.; Potter, G. L.; Gates, W. L.; Taylor, K. E.; Barker, H. W.; Colman, R. A.; Fraser, J. R.; McAvaney, B. J.; Dazlich, D. A.; Randall, D. A.; DelGenio, A. D.; Lacis, A. A.; Esch, M.; Roeckner, E.; Galin, V.; Hack, J. J.; Kiehl, J. T.; Ingram, W. J.; LeTreut, H.

    1993-01-01

    Global warming, caused by an increase in the concentrations of greenhouse gases, is the direct result of greenhouse gas-induced radiative forcing. When a doubling of atmospheric carbon dioxide is considered, this forcing differed substantially among 15 atmospheric general circulation models. Although there are several potential causes, the largest contributor was the carbon dioxide radiation parameterizations of the models.

  1. Radiated power and radiation reaction forces of coherently oscillating charged particles in classical electrodynamics

    NASA Astrophysics Data System (ADS)

    Niknejadi, Pardis; Madey, John M. J.; Kowalczyk, Jeremy M. D.

    2015-05-01

    For the foreseeable future, the analysis and design of the complex systems needed to generate intense beams of radiation via the process of coherent emission into free-space will depend on the principles and methods of classical electrodynamics (CED). But the fields and forces predicted by the currently accepted CED theory are manifestly incompatible with Maxwell's equations' energy integral as applied to the process of coherent emission into free-space. It is the purpose of this paper to review the evidence for these limitations of conventional CED, to identify an alternative formulation of CED that does not suffer from these defects, and to describe how the predictions of this more physically realistic formulation of electrodynamics, including the role of the advanced interactions allowed by Maxwell's equations and thermodynamics, might be tested by experiment and applied to enhance the capabilities of devices and systems employing the mechanism of "radiation into free-space."

  2. Surface shortwave aerosol radiative forcing during the Atmospheric Radiation Measurement Mobile Facility deployment in Niamey, Niger

    NASA Astrophysics Data System (ADS)

    McFarlane, S. A.; Kassianov, E. I.; Barnard, J.; Flynn, C.; Ackerman, T. P.

    2009-07-01

    The Atmospheric Radiation Measurement (ARM) Program's Mobile Facility (AMF) was deployed to Niamey, Niger, during 2006. Niamey, which is located in sub-Saharan Africa, is affected by both dust and biomass burning emissions. Column aerosol optical properties were derived from multifilter rotating shadowband radiometer, measurements and the vertical distribution of aerosol extinction was derived from a micropulse lidar during the two observed dry seasons (January-April and October-December). Mean aerosol optical depth (AOD) and single scattering albedo (SSA) at 500 nm during January-April were 0.53 ± 0.4 and 0.94 ± 0.05, while during October-December mean AOD and SSA were 0.33 ± 0.25 and 0.99 ± 0.01. Aerosol extinction profiles peaked near 500 m during the January-April period and near 100 m during the October-December period. Broadband shortwave surface fluxes and heating rate profiles were calculated using retrieved aerosol properties. Comparisons for noncloudy periods indicated that the remote sensing retrievals provided a reasonable estimation of the aerosol optical properties, with mean differences between calculated and observed fluxes of less than 5 W m-2 and RMS differences less than 25 W m-2. Sensitivity tests showed that the observed fluxes could be matched with variations of <10% in the inputs to the radiative transfer model. The calculated 24-h averaged SW instantaneous surface aerosol radiative forcing (ARF) was -21.1 ± 14.3 W m-2 and was estimated to account for 80% of the total radiative forcing at the surface. The ARF was larger during January-April (-28.5 ± 13.5 W m-2) than October-December (-11.9 ± 8.9 W m-2).

  3. Atmospheric radiation measurement: A program for improving radiative forcing and feedback in general circulation models

    SciTech Connect

    Patrinos, A.A.; Renne, D.S.; Stokes, G.M.; Ellingson, R.G.

    1991-01-01

    The Atmospheric Radiation Measurement (ARM) Program is a key element of the Department of Energy`s (DOE`s) global change research strategy. ARM represents a long-term commitment to conduct comprehensive studies of the spectral atmospheric radiative energy balance profile for a wide range of cloud conditions and surface types, and to develop the knowledge necessary to improve parameterizations of radiative processes under various cloud regimes for use in general circulation models (GCMs) and related models. The importance of the ARM program is a apparent from the results of model assessments of the impact on global climate change. Recent studies suggest that radiatively active trace gas emissions caused by human activity can lead to a global warming of 1.5 to 4.5 degrees Celsius and to important changes in water availability during the next century (Cess, et al. 1989). These broad-scale changes can be even more significant at regional levels, where large shifts in temperature and precipitation patterns are shown to occur. However, these analyses also indicate that considerable uncertainty exists in these estimates, with the manner in which cloud radiative processes are parameterized among the most significant uncertainty. Thus, although the findings have significant policy implications in assessment of global and regional climate change, their uncertainties greatly influence the policy debate. ARM`s highly focused observational and analytical research is intended to accelerate improvements and reduce key uncertainties associated with the way in which GCMs treat cloud cover and cloud characteristics and the resulting radiative forcing. This paper summarizes the scientific context for ARM, ARM`s experimental approach, and recent activities within the ARM program.

  4. Atmospheric radiation measurement: A program for improving radiative forcing and feedback in general circulation models

    SciTech Connect

    Patrinos, A.A. ); Renne, D.S.; Stokes, G.M. ); Ellingson, R.G. )

    1991-01-01

    The Atmospheric Radiation Measurement (ARM) Program is a key element of the Department of Energy's (DOE's) global change research strategy. ARM represents a long-term commitment to conduct comprehensive studies of the spectral atmospheric radiative energy balance profile for a wide range of cloud conditions and surface types, and to develop the knowledge necessary to improve parameterizations of radiative processes under various cloud regimes for use in general circulation models (GCMs) and related models. The importance of the ARM program is a apparent from the results of model assessments of the impact on global climate change. Recent studies suggest that radiatively active trace gas emissions caused by human activity can lead to a global warming of 1.5 to 4.5 degrees Celsius and to important changes in water availability during the next century (Cess, et al. 1989). These broad-scale changes can be even more significant at regional levels, where large shifts in temperature and precipitation patterns are shown to occur. However, these analyses also indicate that considerable uncertainty exists in these estimates, with the manner in which cloud radiative processes are parameterized among the most significant uncertainty. Thus, although the findings have significant policy implications in assessment of global and regional climate change, their uncertainties greatly influence the policy debate. ARM's highly focused observational and analytical research is intended to accelerate improvements and reduce key uncertainties associated with the way in which GCMs treat cloud cover and cloud characteristics and the resulting radiative forcing. This paper summarizes the scientific context for ARM, ARM's experimental approach, and recent activities within the ARM program.

  5. Radiative forcing impacts of boreal forest biofuels: a scenario study for Norway in light of albedo.

    PubMed

    Bright, Ryan M; Strømman, Anders Hammer; Peters, Glen P

    2011-09-01

    Radiative forcing impacts due to increased harvesting of boreal forests for use as transportation biofuel in Norway are quantified using simple climate models together with life cycle emission data, MODIS surface albedo data, and a dynamic land use model tracking carbon flux and clear-cut area changes within productive forests over a 100-year management period. We approximate the magnitude of radiative forcing due to albedo changes and compare it to the forcing due to changes in the carbon cycle for purposes of attributing the net result, along with changes in fossil fuel emissions, to the combined anthropogenic land use plus transport fuel system. Depending on albedo uncertainty and uncertainty about the geographic distribution of future logging activity, we report a range of results, thus only general conclusions about the magnitude of the carbon offset potential due to changes in surface albedo can be drawn. Nevertheless, our results have important implications for how forests might be managed for mitigating climate change in light of this additional biophysical criterion, and in particular, on future biofuel policies throughout the region. Future research efforts should be directed at understanding the relationships between the physical properties of managed forests and albedo, and how albedo changes in time as a result of specific management interventions. PMID:21797227

  6. Observations of x-ray radiation pressure force on individual gold nanocrystals

    SciTech Connect

    Sasaki, Yuji C.; Okumura, Yasuaki; Miyazaki, Takuya; Higurashi, Takashi; Oishi, Noboru

    2006-07-31

    We report observations of x-ray radiation pressure force on individual single nanocrystals using an x-ray single molecular methodology. The observed gold nanocrystals are linked to the adsorbed protein molecules. We observed the directed Brownian motion of individual linked nanocrystals. The observed force is estimated at about 0.13-0.63 aN. We will be able to control and measure dynamics of micro- or nanocrystalline materials using x-ray radiation pressure force.

  7. Influence of X-ray radiation on the hot star wind ionization state and on the radiative force

    NASA Astrophysics Data System (ADS)

    Krtička, Jiří; Kubát, Jiří

    2016-09-01

    Hot stars emit large amounts of X-rays, which are assumed to originate in the supersonic stellar wind. Part of the emitted X-rays is subsequently absorbed in the wind and influences its ionization state. Because hot star winds are driven radiatively, the modified ionization equilibrium affects the radiative force. We review the recent progress in modeling the influence of X-rays on the radiative equilibrium and on the radiative force. We focus particularly on single stars with X-rays produced in wind shocks and on binaries with massive components, which belong to the most luminous objects in X-rays.

  8. Influence of Polarization on Carbohydrate Hydration: A Comparative Study Using Additive and Polarizable Force Fields.

    PubMed

    Pandey, Poonam; Mallajosyula, Sairam S

    2016-07-14

    Carbohydrates are known to closely modulate their surrounding solvent structures and influence solvation dynamics. Spectroscopic investigations studying far-IR regions (below 1000 cm(-1)) have observed spectral shifts in the libration band (around 600 cm(-1)) of water in the presence of monosaccharides and polysaccharides. In this paper, we use molecular dynamics simulations to gain atomistic insight into carbohydrate-water interactions and to specifically highlight the differences between additive (nonpolarizable) and polarizable simulations. A total of six monosaccharide systems, α and β anomers of glucose, galactose, and mannose, were studied using additive and polarizable Chemistry at HARvard Macromolecular Mechanics (CHARMM) carbohydrate force fields. Solvents were modeled using three additive water models TIP3P, TIP4P, and TIP5P in additive simulations and polarizable water model SWM4 in polarizable simulations. The presence of carbohydrate has a significant effect on the microscopic water structure, with the effects being pronounced for proximal water molecules. Notably, disruption of the tetrahedral arrangement of proximal water molecules was observed due to the formation of strong carbohydrate-water hydrogen bonds in both additive and polarizable simulations. However, the inclusion of polarization resulted in significant water-bridge occupancies, improved ordered water structures (tetrahedral order parameter), and longer carbohydrate-water H-bond correlations as compared to those for additive simulations. Additionally, polarizable simulations also allowed the calculation of power spectra from the dipole-dipole autocorrelation function, which corresponds to the IR spectra. From the power spectra, we could identify spectral signatures differentiating the proximal and bulk water structures, which could not be captured from additive simulations. PMID:27266974

  9. Influence of Additional Tensile Force on Springback of Tube Under Rotary Draw Bending

    NASA Astrophysics Data System (ADS)

    E, Daxin; Guan, Zhiping; Chen, Jisheng

    2012-11-01

    According to the characteristics of tube under rotary draw bending, the formulae were derived to calculate the springback angles of tubes subjected to combined bending and additional tension. Especially, as the neutral layer (NL) moves to the inner concave surface of the bend, the analytical values agree very well with the experimental results. The analysis shows that the additional tensile force causes the movement of the NL toward the bending center and makes the deformation behavior under rotary draw bending or numerically controlled (NC) bending different with that under pure bending, and also it could enlarge the springback angle if taking the movement of the NL into consideration. In some range, the springback angle would increase slightly with larger wall thickness/diameter ratio and decrease with wall thinning. The investigation could provide reference for the analysis of rotary draw bending, the design of NC tube bender and the related techniques.

  10. 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.

  11. Transferability and additivity of dihedral parameters in polarizable and nonpolarizable empirical force fields.

    PubMed

    Zgarbová, Marie; Rosnik, Andreana M; Luque, F Javier; Curutchet, Carles; Jurečka, Petr

    2015-09-30

    Recent advances in polarizable force fields have revealed that major reparameterization is necessary when the polarization energy is treated explicitly. This study is focused on the torsional parameters, which are crucial for the accurate description of conformational equilibria in biomolecules. In particular, attention is paid to the influence of polarization on the (i) transferability of dihedral terms between molecules, (ii) transferability between different environments, and (iii) additivity of dihedral energies. To this end, three polarizable force fields based on the induced point dipole model designed for use in AMBER are tested, including two recent ff02 reparameterizations. Attention is paid to the contributions due to short range interactions (1-2, 1-3, and 1-4) within the four atoms defining the dihedral angle. The results show that when short range 1-2 and 1-3 polarization interactions are omitted, as for instance in ff02, the 1-4 polarization contribution is rather small and unlikely to improve the description of the torsional energy. Conversely, when screened 1-2 and 1-3 interactions are included, the polarization contribution is sizeable and shows potential to improve the transferability of parameters between different molecules and environments as well as the additivity of dihedral terms. However, to reproduce intramolecular polarization effects accurately, further fine-tuning of the short range damping of polarization is necessary. PMID:26224547

  12. CHARMM Additive All-Atom Force Field for Acyclic Polyalcohols, Acyclic Carbohydrates and Inositol

    PubMed Central

    Hatcher, Elizabeth; Guvench, Olgun; MacKerell, Alexander D.

    2009-01-01

    Parametrization of the additive all-atom CHARMM force field for acyclic polyalcohols, acyclic carbohydrates and inositol is conducted. Initial parameters were transferred from the alkanes and hexopyranose carbohydrates, with subsequent development and optimization of parameters unique to the molecules considered in this study. Using the model compounds acetone and acetaldehyde, nonbonded parameters for carbonyls were optimized targeting quantum mechanical interaction data for solute-water pairs and pure solvent thermodynamic data. Bond and angle parameters were adjusted by comparing optimized geometries to small molecule crystal survey data and by performing vibrational analyses on acetone, acetaldehyde and glycerol. C-C-C-C, C-C-C-O, C-C-OH and O-C-C-O torsional parameters for polyol chains were fit to quantum mechanical dihedral potential energy scans comprising over 1500 RIMP2/cc-pVTZ//MP2/6-31G(d) conformations using an automated Monte Carlo simulated annealing procedure. Comparison of computed condensed-phase data, including crystal lattice parameters and densities, NMR proton-proton couplings, densities and diffusion coefficients of aqueous solutions, to experimental data validated the optimized parameters. Parameter development for these compounds proved particularly challenging because of the flexibility of the acyclic sugars and polyalcohols as well as the intramolecular hydrogen bonding between vicinal hydroxyls for all of the compounds. The newly optimized additive CHARMM force field parameters are anticipated to be of utility for atomic level of detail simulations of acyclic polyalcohols, acyclic carbohydrates and inositol in solution. PMID:20160980

  13. Quantifying the contributions of individual NO x sources to the trend in ozone radiative forcing

    NASA Astrophysics Data System (ADS)

    Dahlmann, K.; Grewe, V.; Ponater, M.; Matthes, S.

    2011-06-01

    Source attribution of ozone radiative forcing (RF) is a prerequisite for developing adequate emission mitigation strategies with regards to climate impact. Decadal means of ozone fields from transient climate-chemistry simulations (1960-2019) are analysed and the temporal development of ozone RF resulting from individual NO x sources, e.g. road traffic, industry and air traffic, is investigated. We calculated an ozone production efficiency which is mainly dependent on the altitude of NO x emission and on the amount of background NO x with values varying over one order of magnitude. Air traffic and lightning are identified as NO x sources with a two and five times higher ozone production efficiency, respectively, than ground based sources. Second, radiative efficiency of source attributed ozone (i.e. total induced radiative flux change per column ozone) shows clear dependence on latitudinal structure of the ozone anomaly and, to a lesser extent, to its altitude. Lightning induced ozone shows the highest radiative efficiency because lightning primarily enhances ozone in low latitudes in the mid-troposphere (higher altitudes). Superimposed on these effects, a saturation effect causes a decreasing radiative efficiency with increasing background ozone concentrations. Changes in RF attributed to NO x induced ozone from 1960 to 2019 are controlled by three factors: changes in emissions, changes in ozone production efficiency and changes in the radiative efficiency. Leading effect is emission increase, but changes in ozone production efficiency increase ozone RF by a factor of three for air traffic, or reduce ozone RF by around 30% for ships. Additionally, changes in the radiative efficiency due to saturation effects change ozone RF by 2-5%.

  14. Relationship between acoustic power and acoustic radiation force on absorbing and reflecting targets for spherically focusing radiators.

    PubMed

    Gélat, Pierre; Shaw, Adam

    2015-03-01

    Total acoustic output power is an important parameter required by standards for most ultrasonic medical equipment including high-intensity focused ultrasound (HIFU) systems. Radiation force balances are routinely used; however, radiation force is not strictly dependent on the ultrasound power but, rather, on the wave momentum resolved in one direction. Consequently, measurements based on radiation force become progressively less accurate as the ultrasound wave deviates further from a true plane wave. HIFU transducers can be very strongly focused with F-numbers less than one: under these conditions, the uncertainty associated with use of the radiation force method becomes very significant. International Standards IEC 61161 and IEC 62555 suggest plane-wave correction factors for unfocused transducers radiating onto an ideal absorbing target and focusing corrections for focused transducers radiating onto ideal absorbing targets and onto conical reflecting targets (IEC 61161). Previous models have relied on calculations based on the Rayleigh integral, which is not strictly correct for curved sources. In the work described here, an approach combining finite element methods with a discretization of the Helmholtz equation was developed, making it possible to model the boundary condition at the structure/fluid interface more correctly. This has been used to calculate the relationship between radiation force and total power for both absorbing and conical reflecting targets for transducers ranging from planar to an F-number of 0.5 (hemispherical) and to compare with the recommendations of IEC 61161 and IEC 62555. PMID:25683223

  15. Effect of aerosol radiative forcing on the seasonal variation of snow over the northern hemisphere

    NASA Astrophysics Data System (ADS)

    Kim, M.; Lau, W. K.; Lee, W.; Kim, K.

    2009-12-01

    In this study, the effect of aerosol radiative forcing on the seasonal variation of snow is studied based on GCM simulation with prescribed aerosols. Numerical experiments are conducted using NASA fvGCM with McRAS. Monthly mean distribution of five aerosol species (black carbon, organic carbon, dust, sulfate, and sea salt) is obtained from GOCART model. In the control run, all five aerosol species are included. For sensitivity test, we carry out an experiment without any aerosol radiative forcing and three additional runs, which are identical to the control run, except for exclusion of black carbon, of dust, and of sulfate, to show the effect of different types of aerosols. The results show that atmospheric warming by absorbing aerosols, dust and black carbon, initiate the elevated heat pump (EHP) and subsequently warm the atmosphere and land surface, especially over Tibetan Plateau (TP). As a results snow over TP reduced greatly in April and May, and the reduction of snow cover decrease surface albedo. Surface energy balance analysis shows that the surface warming due to absorbing aerosol cause early snow melting and further increase surface-atmosphere warming through snow/ice albedo feedback. The similar relations between aerosol radiative forcing and snow melt are also found over other higher latitude region in the Northern Hemisphere. The intensity and duration of earlier snow melt by black carbon aerosol is more significant than that of dust aerosol over the higher latitude in the Northern Hemisphere while over the Tibetan Plateau both black carbon and dust aerosol are important in driving earlier snow melt.

  16. 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.

  17. 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.

  18. Intercomparison of Models Representing Direct Shortwave Radiative Forcing by Sulfate Aerosols

    NASA Technical Reports Server (NTRS)

    Boucher, O.; Schwartz, S. E.; Ackerman, T. P.; Anderson, T. L.; Bergstrom, B.; Bonnel, B.; Dahlback, A.; Fouquart, Y.; Chylek, P.; Fu, Q.; Halthore, R. N.; Haywood, J. M.; Iversen, T.; Kato, S.; Kinne, S.; Kirkevag, A.; Knapp, K. R.; Lacis, A.; Laszlo, I.; Mishchenko, M. I.

    2000-01-01

    The importance of aerosols as agents of climate change has recently been highlighted. However, the magnitude of aerosol forcing by scattering of shortwave radiation (direct forcing) is still very uncertain even for the relatively well characterized sulfate aerosol. A potential source of uncertainty is in the model representation of aerosol optical properties and aerosol influences on radiative transfer in the atmosphere. Although radiative transfer methods and codes have been compared in the past, these comparisons have not focused on aerosol forcing (change in net radiative flux at the top of the atmosphere). Here we report results of a project involving 12 groups using 15 models to examine radiative forcing by sulfate aerosol for a wide range of values of particle radius, aerosol optical depth, surface albedo, and solar zenith angle. Among the models that were employed were high and low spectral resolution models incorporating a variety of radiative transfer approximations as well as a line-by-line model. The normalized forcings (forcing per sulfate column burden) obtained with the several radiative transfer models were examined, and the discrepancies were characterized. All models simulate forcings of comparable amplitude and exhibit a similar dependence on input parameters. As expected for a non-light-absorbing aerosol, forcings were negative (cooling influence) except at high surface albedo combined with small solar zenith angle. The relative standard deviation of the zenith-angle-averaged normalized broadband forcing for 15 models-was 8% for particle radius near the maximum in this forcing (approx. 0.2 microns) and at low surface albedo. Somewhat greater model-to-model discrepancies were exhibited at specific solar zenith angles. Still greater discrepancies were exhibited at small particle radii and much greater discrepancies were exhibited at high surface albedos, at which the forcing changes sign; in these situations, however, the normalized forcing is

  19. Simulation of uphill/downhill running on a level treadmill using additional horizontal force.

    PubMed

    Gimenez, Philippe; Arnal, Pierrick J; Samozino, Pierre; Millet, Guillaume Y; Morin, Jean-Benoit

    2014-07-18

    Tilting treadmills allow a convenient study of biomechanics during uphill/downhill running, but they are not commonly available and there is even fewer tilting force-measuring treadmill. The aim of the present study was to compare uphill/downhill running on a treadmill (inclination of ± 8%) with running on a level treadmill using additional backward or forward pulling forces to simulate the effect of gravity. This comparison specifically focused on the energy cost of running, stride frequency (SF), electromyographic activity (EMG), leg and foot angles at foot strike, and ground impact shock. The main results are that SF, impact shock, and leg and foot angle parameters determined were very similar and significantly correlated between the two methods, the intercept and slope of the linear regression not differing significantly from zero and unity, respectively. The correlation of oxygen uptake (V̇O2) data between both methods was not significant during uphill running (r=0.42; P>0.05). V̇O2 data were correlated during downhill running (r=0.74; P<0.01) but there was a significant difference between the methods (bias=-2.51 ± 1.94 ml min(-1) kg(-1)). Linear regressions for EMG of vastus lateralis, biceps femoris, gastrocnemius lateralis, soleus and tibialis anterior were not different from the identity line but the systematic bias was elevated for this parameter. In conclusion, this method seems appropriate for the study of SF, leg and foot angle, impact shock parameters but is less applicable for physiological variables (EMG and energy cost) during uphill/downhill running when using a tilting force-measuring treadmill is not possible. PMID:24811045

  20. CHARMM Additive All-Atom Force Field for Aldopentofuranoses, Methyl-Aldopentofuranosides and Fructofuranose

    PubMed Central

    Hatcher, Elizabeth; Guvench, Olgun; MacKerell, Alexander D.

    2009-01-01

    An additive all-atom empirical force field for aldopentofuranoses, methyl-aldopentofuranosides (Me-aldopentofuranosides) and fructofuranose carbohydrates, compatible with existing CHARMM carbohydrate parameters, is presented. Building on existing parameters transferred from cyclic ethers and hexopyranoses, parameters were further developed using target data for complete furanose carbohydrates as well as O-methyl tetrahydrofuran. The bond and angle equilibrium parameters were adjusted to reproduce target geometries from a survey of furanose crystal structures, and dihedral parameters were fit to over 1700 quantum mechanical (QM) MP2/cc-pVTZ//MP2/6-31G(d) conformational energies. The conformational energies were for a variety of complete furanose monosaccharides, and included two-dimensional ring pucker energy surfaces. Bonded parameter optimization led to the correct description of the ring pucker for a large set of furanose compounds, while furanose-water interaction energies and distances reproduced QM HF/6-31G(d) results for a number of furanose monosaccharides, thereby validating the nonbonded parameters. Crystal lattice unit cell parameters and volumes, aqueous-phase densities, and aqueous NMR ring pucker and exocyclic data were used to validate the parameters in condensed-phase environments. Conformational sampling analysis of the ring pucker and exocyclic group showed excellent agreement with experimental NMR data, demonstrating that the conformational energetics in aqueous solution are accurately described by the optimized force field. Overall, the parameters reproduce available experimental data well and are anticipated to be of utility in future computational studies of carbohydrates, including in the context of proteins, nucleic acids and/or lipids when combined with existing CHARMM biomolecular force fields. PMID:19694450

  1. Negative axial radiation forces on solid spheres and shells in a Bessel beam.

    PubMed

    Marston, Philip L

    2007-12-01

    Prior computations predict that fluid spheres illuminated by an acoustic Bessel beam can be subjected to a radiation force directed opposite the direction of beam propagation. The prediction of negative acoustic radiation force is extended to the cases of a solid poly(methylmethacrylate) PMMA sphere in water and an empty aluminum spherical shell in water. Compared with the angular scattering patterns for plane wave illumination, the scattering into the back hemisphere is suppressed when the radiation force is negative. This investigation may be helpful in the development of acoustic tweezers and in the development of methods for manipulating objects during space flight. PMID:18247728

  2. 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).

  3. Radiative forcing and temperature change at Potsdam between 1893 and 2012

    NASA Astrophysics Data System (ADS)

    Stanhill, Gerald; Ahiman, Ori

    2014-08-01

    Radiative forcing in both the short and long-wave lengths reaching the Earth's surface accounted for more than 80% of the inter-annual variations in the mean yearly temperatures measured at Potsdam, Germany, during the last 120 years. Three quarters of the increase in the long-wave flux was due to changes in the water content of the lower atmosphere; the remainder was attributed to increases in CO2 and other anthropogenic, radiatively active gases. Over the period radiative forcing in the short-wave flux slightly exceeded that in the long wave, but its effect on air temperature was much less as the climate sensitivity to atmospheric radiation, 0.187°C per W m-2, was three times greater than to short-wave global radiation. This anomalous finding, similar to that previously reported at two coastal sites, awaits explanation as does the complex interaction existing between radiative forcing and advection in determining temperature change.

  4. Energy conservation equation for a radiating pointlike charge in the context of the Abraham-Lorentz versus the Abraham-Becker radiation-reaction force

    NASA Astrophysics Data System (ADS)

    Bellotti, U.; Bornatici, M.

    1997-12-01

    With reference to a radiating pointlike charge, the energy conservation equation comprising the effect of the Abraham-Lorentz radiation-reaction force is contrasted with the incorrect energy conservation equation obtained by Hartemann and Luhmann [Phys. Rev. Lett. 74, 1107 (1995)] on considering instead the Abraham-Becker force that accounts only for a part of the instantaneous radiation-reaction force.

  5. Radiative forcing of organic aerosol in the atmosphere and on snow: incorporation of SOA and brown carbon

    NASA Astrophysics Data System (ADS)

    Lin, G.; Flanner, M.; Penner, J. E.

    2013-12-01

    Organic aerosols (OA) play an important role in climate change through their radiative forcing. Secondary organic aerosol (SOA) contributes a large portion of total organic aerosol, especially in remote regions. Organic aerosol has been shown to be an important source of solar-light absorption. However, very few global model calculations of the radiative forcing due to organic aerosol include SOA or the light-absorbing part of OA (brown carbon). Here, we use a global chemical transport model with a detailed SOA formation mechanism to investigate the change in SOA between present day and pre-industrial conditions. We employ a radiative transfer model to assess the radiative forcing associated with the change in SOA. We also reassess the radiative forcing of total OA by considering previously neglected brown carbon. In addition to the OA in the atmosphere, we examine for the first time the radiative forcing of OA deposited in snow and sea-ice by using the NCAR Community Land Model 4 (CLM4) for the land snow simulation and the Community Ice CodE 4 (CICE) for the sea-ice simulation. Anthropogenic emissions of NOx, CO, sulfate, biomass burning and fossil fuel organic aerosol are shown to influence the formation rate of SOA substantially, causing it to increase by 35 Tg/yr (41%) since pre-industrial times. The increase of SOA results in a direct forcing ranging from -0.12 to -0.34 Wm-2 and a first indirect forcing in warm phase clouds ranging from -0.24 to -0.32 Wm-2, with the range due to different assumed size distributions for SOA and different refractive indices. The global burden of primary organic aerosol (POA) is estimated to increase by 0.53 Tg since pre-industrial times. Based on different refractive indices assumed for brown carbon, the increase of POA leads to a direct forcing varying from -0.07 to -0.12 Wm-2. The change in total OA exerts a direct radiative forcing ranging from -0.17 to -0.46 Wm-2. Atmospheric absorption from brown carbon ranges from +0.13 to

  6. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  7. 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.

  8. Signatures of semi-direct radiative forcing by absorbing aerosols in satellite observations and models

    NASA Astrophysics Data System (ADS)

    Wilcox, E. M.; Hosseinpour, F.; Colarco, P. R.

    2014-12-01

    Semi-direct radiative forcing of climate occurs when interactions between aerosols and radiative fluxes in the atmosphere yield a dynamical response in clouds. Semi-direct forcing is typically thought to be a positive radiative forcing whereby soot and biomass burning aerosols absorb sunlight and burn-off clouds. However, a negative semi-direct forcing is suspected in at least two regimes, the summertime Southeast Atlantic Ocean and the wintertime North Indian Ocean, where the heating profile by aerosol absorption by solar radiation is elevated above the elevation of the low clouds. Here we use a combination of satellite data and a model simulation to further characterize the signature of semi-direct radiative forcing in these two locations and elsewhere on the globe. We apply CERES albedos, Calipso profiles of aerosol extinction and cloud-top altitude, and a simulation with the Goddard Earth Observing System Model version 5 (GEOS-5) Earth system model with meteorology constrained by MERRA and an assimilation of MODIS AOT (MERRAero). to quantify the vertical heating profile by aerosols under clear and cloudy skies. We seek to determine: (1) where aerosol heating by soot and biomass burning aerosol is occurring; (2) where vertically in the column the heating is occurring relative to the observed level of low cloud development; and (3) whether the variations of albedo with aerosol forcing suggest a positive, negative, or inconclusive semi-direct radiative forcing.

  9. 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.

  10. Resolution of the uncertainties in the radiative forcing of HFC-134a

    NASA Astrophysics Data System (ADS)

    Forster, Piers M. De F.; Burkholder, J. B.; Clerbaux, C.; Coheur, P. F.; Dutta, M.; Gohar, L. K.; Hurley, M. D.; Myhre, G.; Portmann, R. W.; Shine, K. P.; Wallington, T. J.; Wuebbles, D.

    2005-07-01

    HFC-134a (CF3CH2F) is the most rapidly growing hydrofluorocarbon in terms of atmospheric abundance. It is currently used in a large number of household refrigerators and air-conditioning systems and its concentration in the atmosphere is forecast to increase substantially over the next 50 100 years. Previous estimates of its radiative forcing per unit concentration have differed significantly ˜25%. This paper uses a two-step approach to resolve this discrepancy. In the first step six independent absorption cross section datasets are analysed. We find that, for the integrated cross section in the spectral bands that contribute most to the radiative forcing, the differences between the various datasets are typically smaller than 5% and that the dependence on pressure and temperature is not significant. A “recommended'' HFC-134a infrared absorption spectrum was obtained based on the average band intensities of the strongest bands. In the second step, the “recommended'' HFC-134a spectrum was used in six different radiative transfer models to calculate the HFC-134a radiative forcing efficiency. The clear-sky instantaneous radiative forcing, using a single global and annual mean profile, differed by 8%, between the 6 models, and the latitudinally-resolved adjusted cloudy sky radiative forcing estimates differed by a similar amount. We calculate that the radiative forcing efficiency of HFC-134a is 0.16±0.02Wmppbv.

  11. Surprises and anomalies in acoustical and optical scattering and radiation forces

    NASA Astrophysics Data System (ADS)

    Marston, Philip L.

    2015-09-01

    Experiments on radiation torques and negative radiation forces by various researchers display how the underlying wave-field geometry influences radiation forces. Other situations strongly influenced by wave-field geometry include high-order caustics present in light-scattering patterns of objects as simple as oblate drops of water or oblate bubbles of air in water. Related theoretical and experimental investigations are considered. Acoustic scattering enhancements associated with various guided waves are also examined. These include guided waves having negative group velocities and guided wave radiating wavefronts having a vanishing Gaussian curvature.

  12. CHARMM Additive All-Atom Force Field for Phosphate and Sulfate Linked to Carbohydrates

    PubMed Central

    Mallajosyula, Sairam S.; Guvench, Olgun; Hatcher, Elizabeth; MacKerell, Alexander D.

    2012-01-01

    Presented is an extension of the CHARMM additive all-atom carbohydrate force field to enable the modeling of phosphate and sulfate linked to carbohydrates. The parameters are developed in a hierarchical fashion using model compounds containing the key atoms in the full carbohydrates. Target data for parameter optimization included full two-dimensional energy surfaces defined by the glycosidic dihedral angle pairs in the phosphate/sulfate model compound analogs of hexopyranose monosaccharide phosphates and sulfates, as determined by quantum mechanical (QM) MP2/cc-pVTZ single point energies on MP2/6-31+G(d) optimized structures. In order to achieve balanced, transferable dihedral parameters for the dihedral angles, surfaces for all possible anomeric and conformational states were included during the parametrization process. In addition, to model physiologically relevant systems both the mono- and di-anionic charged states were studied for the phosphates. This resulted in over 7000 MP2/cc-pVTZ//MP2/6-31G+(d) model compound conformational energies which, supplemented with QM geometries, were the main target data for the parametrization. Parameters were validated against crystals of relevant monosaccharide derivatives obtained from the Cambridge Structural Database (CSD) and larger systems, namely inositol-(tri/tetra/penta) phosphates non-covalently bound to the pleckstrin homology (PH) domain and oligomeric chondroitin sulfate in solution and in complex with cathepsin K protein. PMID:22685386

  13. Solar Radiation and Cloud Radiative Forcing in the Pacific Warm Pool Estimated Using TOGA COARE Measurements

    NASA Technical Reports Server (NTRS)

    Chou, Ming-Dah; Chou, Shu-Hsien; Zhao, Wenzhong

    1999-01-01

    The energy budget of the tropical western Pacific (TWP) is particularly important because this is one of the most energetic convection regions on the Earth. Nearly half of the solar radiation incident at the top of atmosphere is absorbed at the surface and only about 22% absorbed in the atmosphere. A large portion of the excess heat absorbed at the surface is transferred to the atmosphere through evaporation, which provides energy and water for convection and precipitation. The western equatorial Pacific is characterized by the highest sea surface temperature (SST) and heaviest rainfall in the world ocean. A small variation of SST associated with the eastward shift of the warm pool during El-Nino/Souther Oscillation changes the atmospheric circulation pattern and affects the global climate. In a study of the TWP surface heat and momentum fluxes during the Tropical Ocean and Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) Intensive observing period (IOP) from November 1992 to February have found that the solar radiation is the most important component of the surface energy budget, which undergoes significant temporal and spatial variation. The variations are influenced by the two 40-50 days Madden Julian Oscillations (MJOs) which propagated eastward from the Indian Ocean to the Central Pacific during the IOP. The TWP surface solar radiation during the COARE IOP was investigated by a number of studies. In addition, the effects of clouds on the solar heating of the atmosphere in the TWP was studied using energy budget analysis. In this study, we present some results of the TWP surface solar shortwave or SW radiation budget and the effect of clouds on the atmospheric solar heating using the surface radiation measurements and Japan's Geostationary Meteorological Satellite 4 radiance measurements during COARE IOP.

  14. Liver reserve function assessment by acoustic radiation force impulse imaging

    PubMed Central

    Sun, Xiao-Lan; Liang, Li-Wei; Cao, Hui; Men, Qiong; Hou, Ke-Zhu; Chen, Zhen; Zhao, Ya-E

    2015-01-01

    AIM: To evaluate the utility of liver reserve function by acoustic radiation force impulse (ARFI) imaging in patients with liver tumors. METHODS: Seventy-six patients with liver tumors were enrolled in this study. Serum biochemical indexes, such as aminotransferase (ALT), aspartate aminotransferase (AST), serum albumin (ALB), total bilirubin (T-Bil), and other indicators were observed. Liver stiffness (LS) was measured by ARFI imaging, measurements were repeated 10 times, and the average value of the results was taken as the final LS value. Indocyanine green (ICG) retention was performed, and ICG-K and ICG-R15 were recorded. Child-Pugh (CP) scores were carried out based on patient’s preoperative biochemical tests and physical condition. Correlations among CP scores, ICG-R15, ICG-K and LS values were observed and analyzed using either the Pearson correlation coefficient or the Spearman rank correlation coefficient. Kruskal-Wallis test was used to compare LS values of CP scores, and the receiver-operator characteristic (ROC) curve was used to analyze liver reserve function assessment accuracy. RESULTS: LS in the ICG-R15 10%-20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.19 ± 0.27 vs 1.59 ± 0.32, P < 0.01). LS in the ICG-R15 > 20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.92 ± 0.29 vs 1.59 ± 0.32, P < 0.01). The LS value in patients with CP class A was lower than in patients with CP class B (1.57 ± 0.34 vs 1.86 ± 0.27, P < 0.05), while the LS value in patients with CP class B was lower than in patients with CP class C (1.86 ± 0.27 vs 2.47 ± 0.33, P < 0.01). LS was positively correlated with ICG-R15 (r = 0.617, P < 0.01) and CP score (r = 0.772, P < 0.01). Meanwhile, LS was negatively correlated with ICG-K (r = -0.673, P < 0.01). AST, ALT and T-Bil were positively correlated with LS, while ALB was negatively

  15. 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.

  16. Radiation pressure excitation of Low Temperature Atomic Force & Magnetic Force Microscope (LT-AFM/MFM) for Imaging

    NASA Astrophysics Data System (ADS)

    Karci, Ozgur; Celik, Umit; Oral, Ahmet; NanoMagnetics Instruments Ltd. Team; Middle East Tech Univ Team

    2015-03-01

    We describe a novel method for excitation of Atomic Force Microscope (AFM) cantilevers by means of radiation pressure for imaging in an AFM for the first time. Piezo excitation is the most common method for cantilever excitation, but it may cause spurious resonance peaks. A fiber optic interferometer with 1310 nm laser was used both to measure the deflection of cantilever and apply a force to the cantilever in a LT-AFM/MFM from NanoMagnetics Instruments. The laser power was modulated at the cantilever`s resonance frequency by a digital Phase Lock Loop (PLL). The force exerted by the radiation pressure on a perfectly reflecting surface by a laser beam of power P is F = 2P/c. We typically modulate the laser beam by ~ 800 μW and obtain 10nm oscillation amplitude with Q ~ 8,000 at 2.5x10-4 mbar. The cantilever's stiffness can be accurately calibrated by using the radiation pressure. We have demonstrated performance of the radiation pressure excitation in AFM/MFM by imaging a hard disk sample between 4-300K and Abrikosov vortex lattice in BSCCO single crystal at 4K to for the first time.

  17. Non-Kyoto Radiative Forcing in Long-Run Greenhouse Gas Emissions and Climate Change Scenarios

    SciTech Connect

    Rose, Steven K.; Richels, Richard G.; Smith, Steven J.; Riahi, Keywan; Stefler, Jessica; Van Vuuren, Detlef

    2014-04-27

    Climate policies designed to achieve climate change objectives must consider radiative forcing from the Kyoto greenhouse gas, as well as other forcing constituents, such as aerosols and tropospheric ozone. Net positive forcing leads to global average temperature increases. Modeling of non-Kyoto forcing is a relatively new component of climate management scenarios. Five of the nineteen models in the EMF-27 Study model both Kyoto and non-Kyoto forcing. This paper describes and assesses current non-Kyoto radiative forcing modeling within these integrated assessment models. The study finds negative forcing from aerosols masking significant positive forcing in reference non-climate policy projections. There are however large differences across models in projected non-Kyoto emissions and forcing, with differences stemming from differences in relationships between Kyoto and non-Kyoto emissions and fundamental differences in modeling structure and assumptions. Air pollution and non-Kyoto forcing decline in the climate policy scenarios. However, non-Kyoto forcing appears to be influencing mitigation results, including allowable carbon dioxide emissions, and further evaluation is merited. Overall, there is substantial uncertainty related to non-Kyoto forcing that must be considered.

  18. Impact on Climate due to Changes in Radiative Forcing from Stratospheric Aircraft Emissions

    NASA Astrophysics Data System (ADS)

    Dutta, M.; Wuebbles, D. J.; Herman, R.; Baughcum, S. L.

    2004-05-01

    Aircraft emissions can affect climate both directly and indirectly. The 1999 Intergovernmental Panel on Climate Change report on Aviation and The Global Atmosphere estimated that emissions from a fleet of one thousand High Speed Civil Transport aircraft (flying at Mach 2.4) could produce a non-negligible impact on the radiative forcing driving changes in climate. In this study we reexamine the radiative forcing from fleets of aircraft flying at stratospheric altitudes and predominantly in the northern hemisphere mid-latitude regions. We use our narrowband radiative transfer model in these studies, along with model calculations of calculated changes in ozone and water vapor from our zonally-averaged model of atmospheric chemical and physical processes. The radiative transfer model has higher resolution in the tropopause and lower stratosphere region than the models used in the 1999 IPCC assessment. Our results suggest that the radiative forcing for the water vapor emissions from aircraft was overestimated previously.

  19. The effects of cloud radiative forcing on an ocean-covered planet

    NASA Technical Reports Server (NTRS)

    Randall, David A.

    1990-01-01

    Cumulus anvil clouds, whose importance has been emphasized by observationalists in recent years, exert a very powerful influence on deep tropical convection by tending to radiatively destabilize the troposphere. In addition, they radiatively warm the column in which they reside. Their strong influence on the simulated climate argues for a much more refined parameterization in the General Circulation Model (GCM). For Seaworld, the atmospheric cloud radiative forcing (ACRF) has a powerful influence on such basic climate parameters as the strength of the Hadley circulation, the existence of a single narrow InterTropical Convergence Zone (ITCZ), and the precipitable water content of the atmosphere. It seems likely, however, that in the real world the surface CRF feeds back negatively to suppress moist convection and the associated cloudiness, and so tends to counteract the effects of the ACRF. Many current climate models have fixed sea surface temperatures but variable land-surface temperatures. The tropical circulations of such models may experience a position feedback due to ACRF over the oceans, and a negative or weak feedback due to surface CRF over the land. The overall effects of the CRF on the climate system can only be firmly established through much further analysis, which can benefit greatly from the use of a coupled ocean-atmospheric model.

  20. Experimental verification of theoretical equations for acoustic radiation force on compressible spherical particles in traveling waves

    NASA Astrophysics Data System (ADS)

    Johnson, Kennita A.; Vormohr, Hannah R.; Doinikov, Alexander A.; Bouakaz, Ayache; Shields, C. Wyatt; López, Gabriel P.; Dayton, Paul A.

    2016-05-01

    Acoustophoresis uses acoustic radiation force to remotely manipulate particles suspended in a host fluid for many scientific, technological, and medical applications, such as acoustic levitation, acoustic coagulation, contrast ultrasound imaging, ultrasound-assisted drug delivery, etc. To estimate the magnitude of acoustic radiation forces, equations derived for an inviscid host fluid are commonly used. However, there are theoretical predictions that, in the case of a traveling wave, viscous effects can dramatically change the magnitude of acoustic radiation forces, which make the equations obtained for an inviscid host fluid invalid for proper estimation of acoustic radiation forces. To date, experimental verification of these predictions has not been published. Experimental measurements of viscous effects on acoustic radiation forces in a traveling wave were conducted using a confocal optical and acoustic system and values were compared with available theories. Our results show that, even in a low-viscosity fluid such as water, the magnitude of acoustic radiation forces is increased manyfold by viscous effects in comparison with what follows from the equations derived for an inviscid fluid.

  1. Experimental verification of theoretical equations for acoustic radiation force on compressible spherical particles in traveling waves.

    PubMed

    Johnson, Kennita A; Vormohr, Hannah R; Doinikov, Alexander A; Bouakaz, Ayache; Shields, C Wyatt; López, Gabriel P; Dayton, Paul A

    2016-05-01

    Acoustophoresis uses acoustic radiation force to remotely manipulate particles suspended in a host fluid for many scientific, technological, and medical applications, such as acoustic levitation, acoustic coagulation, contrast ultrasound imaging, ultrasound-assisted drug delivery, etc. To estimate the magnitude of acoustic radiation forces, equations derived for an inviscid host fluid are commonly used. However, there are theoretical predictions that, in the case of a traveling wave, viscous effects can dramatically change the magnitude of acoustic radiation forces, which make the equations obtained for an inviscid host fluid invalid for proper estimation of acoustic radiation forces. To date, experimental verification of these predictions has not been published. Experimental measurements of viscous effects on acoustic radiation forces in a traveling wave were conducted using a confocal optical and acoustic system and values were compared with available theories. Our results show that, even in a low-viscosity fluid such as water, the magnitude of acoustic radiation forces is increased manyfold by viscous effects in comparison with what follows from the equations derived for an inviscid fluid. PMID:27300980

  2. The directional sensitivity of the acoustic radiation force to particle diameter.

    PubMed

    Ran, W; Saylor, J R

    2015-06-01

    When viscous corrections to the inviscid acoustic radiation force theory are implemented and applied to a standing wave field, the direction of the acoustic radiation force on particles varies from theory to theory. Specifically, some theories predict that the direction of the force depends on the particle diameter, while others reveal that the direction of the force is independent of particle diameter. The present study is an experimental investigation of the direction of the acoustic radiation force which suggests that particle diameter does affect the direction. Experiments were conducted in air using an ultrasonic standing wave field with a nominal frequency of 30 kHz. Smoke particles and fine water droplets having a range of diameters were flowed into the region of a standing wave field. The direction of the acoustic radiation force was determined by observing whether the particles accumulated in the nodes or the anti-nodes of the standing wave. Results show a change in the direction of the acoustic radiation force at a particle diameter of 0.3±0.1 μm, which corresponds to a particle diameter to acoustic-boundary-layer thickness ratio of 0.023±0.008. PMID:26093419

  3. Radiative forcing perturbation due to observed increases in tropospheric ozone at Hohenpeissenberg

    NASA Technical Reports Server (NTRS)

    Wang, Wei-Chyung; Bojkov, Rumen D.; Zhuang, Yi-Cheng

    1994-01-01

    The effect on surface temperature due to changes in atmospheric O3 depends highly on the latitude where the change occurs. Previous sensitivity calculations indicate that ozone changes in the upper troposphere and lower stratosphere are more effective in causing surface temperature change (Wang et al., 1980). Long term ground-based observations show that tropospheric ozone, especially at the tropopause region, has been increasing at middle and high latitudes in the Northern Hemisphere (NATO, 1988; Quadrennial Ozone Symposium, 1992). These increases will enhance the greenhouse effect and increase the radiative forcing to the troposphere-surface system, which is opposite to the negative radiative forcing calculated from the observed stratospheric ozone depletion recently reported in WMO (1992). We used more than two thousands regularly measured ozonesondes providing reliable vertical O3 distribution at Hohenpeissenberg (47N; 11E) for the 1967-1990 to study the instantaneous solar and longwave radiative forcing the two decades 1971-1990 and compare the forcing with those caused by increasing CO2, CH4, N2O, and CFCs. Calculations are also made to compare the O3 radiative forcing between stratospheric depletion and tropospheric increase. Results indicate that the O3 changes will induce a positive radiative forcing dominated by tropospheric O3 increase and the magnitude of the forcing is comparable to that due to CO2 increases during the two decades. The significant implications of the tropospheric O3 increase to the global climate are discussed.

  4. 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.

  5. GENERATION OF SEED MAGNETIC FIELD AROUND FIRST STARS: EFFECTS OF RADIATION FORCE

    SciTech Connect

    Ando, Masashi; Doi, Kentaro; Susa, Hajime E-mail: mn921009@center.konan-u.ac.j

    2010-06-20

    We investigate seed magnetic field generation in the early universe by the radiation force of first stars. In a previous study with the steady assumption, large amplitudes ({approx}10{sup -15} G for first stars, {approx}10{sup -11} G for QSOs) are predicted. In this study, we formulate this issue in an unsteady framework. Then, we consider a specific model of magnetic field generation around a very massive first star. Consequently, we (1) find that the steady assumption is not valid in realistic situations and (2) obtain a much smaller magnetic field strength than that predicted by Langer et al. In addition, we find that the momentum transfer process during photoionization is more important than Thomson scattering. The resultant magnetic flux density around the first star is {approx_lt}10{sup -19} G. This seed magnetic field will not affect subsequent star formation in the neighborhood of first stars.

  6. Generation of Seed Magnetic Field Around First Stars: Effects of Radiation Force

    NASA Astrophysics Data System (ADS)

    Ando, Masashi; Doi, Kentaro; Susa, Hajime

    2010-06-01

    We investigate seed magnetic field generation in the early universe by the radiation force of first stars. In a previous study with the steady assumption, large amplitudes (~10-15 G for first stars, ~10-11 G for QSOs) are predicted. In this study, we formulate this issue in an unsteady framework. Then, we consider a specific model of magnetic field generation around a very massive first star. Consequently, we (1) find that the steady assumption is not valid in realistic situations and (2) obtain a much smaller magnetic field strength than that predicted by Langer et al. In addition, we find that the momentum transfer process during photoionization is more important than Thomson scattering. The resultant magnetic flux density around the first star is lsim10-19 G. This seed magnetic field will not affect subsequent star formation in the neighborhood of first stars.

  7. 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.

  8. ENSO surface longwave radiation forcing over the tropical Pacific

    NASA Astrophysics Data System (ADS)

    Pavlakis, K. G.; Hatzidimitriou, D.; Drakakis, E.; Matsoukas, C.; Fotiadi, A.; Hatzianastassiou, N.; Vardavas, I.

    2006-12-01

    We have studied the spatial and temporal variation of the surface longwave radiation (downwelling and net) over a 21-year period in the tropical and subtropical Pacific Ocean (40 S-40 N, 90 E-75 W). The fluxes were computed using a deterministic model for atmospheric radiation transfer, along with satellite data from the ISCCP-D2 database and reanalysis data from NCEP/NCAR (acronyms explained in main text), for the key atmospheric and surface input parameters. An excellent correlation was found between the downwelling longwave radiation (DLR) anomaly and the Niño-3.4 index time-series, over the Niño-3.4 region located in the central Pacific. A high anti-correlation was also found over the western Pacific (15-0 S, 105-130 E). There is convincing evidence that the time series of the mean downwelling longwave radiation anomaly in the western Pacific precedes that in the Niño-3.4 region by 3-4 months. Thus, the downwelling longwave radiation anomaly is a complementary index to the SST anomaly for the study of ENSO events and can be used to asses whether or not El Niño or La Niña conditions prevail. Over the Niño-3.4 region, the mean DLR anomaly values range from +20 Wm-2 during El Niño episodes to -20 Wm-2 during La Niña events, while over the western Pacific (15-0 S, 105-130 E) these values range from -15 Wm-2 to +10 Wm-2, respectively. The long- term average (1984-2004) distribution of the net surface longwave radiation to the surface over the tropical and subtropical Pacific for the three month period November-December-January shows a net thermal cooling of the ocean surface. When El Niño conditions prevail, the thermal radiative cooling in the central and south-eastern tropical Pacific becomes weaker by 10 Wm-2 south of the equator in the central Pacific (7-0 S, 160-120 W) for the three-month period of NDJ, because the DLR increase is larger than the increase in surface thermal emission. In contrast

  9. ENSO surface longwave radiation forcing over the tropical Pacific

    NASA Astrophysics Data System (ADS)

    Pavlakis, K. G.; Hatzidimitriou, D.; Drakakis, E.; Matsoukas, C.; Fotiadi, A.; Hatzianastassiou, N.; Vardavas, I.

    2007-04-01

    We have studied the spatial and temporal variation of the surface longwave radiation (downwelling and net) over a 21-year period in the tropical and subtropical Pacific Ocean (40 S-40 N, 90 E-75 W). The fluxes were computed using a deterministic model for atmospheric radiation transfer, along with satellite data from the ISCCP-D2 database and reanalysis data from NCEP/NCAR (acronyms explained in main text), for the key atmospheric and surface input parameters. An excellent correlation was found between the downwelling longwave radiation (DLR) anomaly and the Niño-3.4 index time-series, over the Niño-3.4 region located in the central Pacific. A high anti-correlation was also found over the western Pacific (15-0 S, 105-130 E). There is convincing evidence that the time series of the mean downwelling longwave radiation anomaly in the western Pacific precedes that in the Niño-3.4 region by 3-4 months. Thus, the downwelling longwave radiation anomaly is a complementary index to the SST anomaly for the study of ENSO events and can be used to asses whether or not El Niño or La Niña conditions prevail. Over the Niño-3.4 region, the mean DLR anomaly values range from +20 Wm-2 during El Niño episodes to -20 Wm-2 during La Niña events, while over the western Pacific (15-0 S, 105-130 E) these values range from -15 Wm-2 to +10 Wm-2, respectively. The long- term average (1984-2004) distribution of the net downwelling longwave radiation at the surface over the tropical and subtropical Pacific for the three month period November-December-January shows a net thermal cooling of the ocean surface. When El Niño conditions prevail, the thermal radiative cooling in the central and south-eastern tropical Pacific becomes weaker by 10 Wm-2 south of the equator in the central Pacific (7-0 S, 160-120 W) for the three-month period of NDJ, because the DLR increase is larger than the increase in surface thermal emission. In contrast

  10. Observation of Nonclassical Radiation Pressure Forces on a Mechanical Oscillator

    NASA Astrophysics Data System (ADS)

    Clark, Jeremy; Lecocq, Florent; Simmonds, Raymond; Aumentado, Jose; Teufel, John

    Squeezed states of light are known to be useful for enhancing mechanical displacement sensing since they can be tailored to reduce the ``photon counting noise'' that limits the measurement's noise floor. On the other hand, recent experiments in cavity optomechanics have reached measurement regimes where an interrogating light field exerts radiation pressure noise on a mechanical oscillator. One outstanding challenge has been to explore the intersection between such experiments. I will present data obtained using a superconducting cavity optomechanical system wherein a mechanical oscillator is driven by nonclassical radiation pressure imparted by squeezed microwave fields. JBC acknowledges the NRC for financial support.

  11. 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).

  12. Mapping of laser diode radiation intensity by atomic-force microscopy

    NASA Astrophysics Data System (ADS)

    Alekseev, P. A.; Dunaevskii, M. S.; Slipchenko, S. O.; Podoskin, A. A.; Tarasov, I. S.

    2015-09-01

    The distribution of the intensity of laser diode radiation has been studied using an original method based on atomic-force microscopy (AFM). It is shown that the laser radiation intensity in both the near field and transition zone of a high-power semiconductor laser under room-temperature conditions can be mapped by AFM at a subwavelength resolution. The obtained patterns of radiation intensity distribution agree with the data of modeling and the results of near-field optical microscopy measurements.

  13. 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.

  14. 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.

  15. Acoustic radiation force impulse (ARFI) imaging: Characterizing the mechanical properties of tissues using their transient response to localized force

    NASA Astrophysics Data System (ADS)

    Nightingale, Kathryn R.; Palmeri, Mark L.; Congdon, Amy N.; Frinkely, Kristin D.; Trahey, Gregg E.

    2001-05-01

    Acoustic radiation force impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in tissue, and conventional diagnostic ultrasound methods to detect the resulting tissue displacements in order to image the relative mechanical properties of tissue. The magnitude and spatial extent of the applied force is dependent upon the transmit beam parameters and the tissue attenuation. Forcing volumes are on the order of 5 mm3, pulse durations are less than 1 ms, and tissue displacements are typically several microns. Images of tissue displacement reflect local tissue stiffness, with softer tissues (e.g., fat) displacing farther than stiffer tissues (e.g., muscle). Parametric images of maximum displacement, time to peak displacement, and recovery time provide information about tissue material properties and structure. In both in vivo and ex vivo data, structures shown in matched B-mode images are in good agreement with those shown in ARFI images, with comparable resolution. Potential clinical applications under investigation include soft tissue lesion characterization, assessment of focal atherosclerosis, and imaging of thermal lesion formation during tissue ablation procedures. Results from ongoing studies will be presented. [Work supported by NIH Grant R01 EB002132-03, and the Whitaker Foundation. System support from Siemens Medical Solutions USA, Inc.

  16. Microwave radiation force and torque on a disk resonator excited by a circularly polarized plane wave

    NASA Astrophysics Data System (ADS)

    Makarov, S.; Kulkarni, S.

    2004-05-01

    A numerical simulation method [S. Makarov and S. Kulkarni, Appl. Phys. Lett. 84, 1600 (2004)] is used in order to determine the radiation force and radiation torque on a parallel-plate disk resonator, whose size is comparable to wavelength. The method is based on the MOM solution of the electric-field integral equation, accurate calculation of the near field, and removal of the self-interaction terms responsible for the pinch effect. The local force/torque distribution at the normal incidence of a circularly polarized plane wave is found. It is observed that, at the resonance, the individual disks are subject to unexpectedly large local force densities, despite the fact that the net radiation force on the resonator remains very small. On the other hand, the total axial torque on the disk resonator also increases at the resonance.

  17. Radiative forcing over the conterminous United States due to contemporary land cover land use albedo change

    USGS Publications Warehouse

    Barnes, Christopher; Roy, David P.

    2008-01-01

    Recently available satellite land cover land use (LCLU) and albedo data are used to study the impact of LCLU change from 1973 to 2000 on surface albedo and radiative forcing for 36 ecoregions covering 43% of the conterminous United States (CONUS). Moderate Resolution Imaging Spectroradiometer (MODIS) snow-free broadband albedo values are derived from Landsat LCLU classification maps located using a stratified random sampling methodology to estimate ecoregion estimates of LCLU induced albedo change and surface radiative forcing. The results illustrate that radiative forcing due to LCLU change may be disguised when spatially and temporally explicit data sets are not used. The radiative forcing due to contemporary LCLU albedo change varies geographically in sign and magnitude, with the most positive forcings (up to 0.284 Wm−2) due to conversion of agriculture to other LCLU types, and the most negative forcings (as low as −0.247 Wm−2) due to forest loss. For the 36 ecoregions considered a small net positive forcing (i.e., warming) of 0.012 Wm−2 is estimated.

  18. Off-axial acoustic radiation force of repulsor and tractor bessel beams on a sphere.

    PubMed

    Silva, Glauber T; Lopes, J Henrique; Mitri, Farid G

    2013-06-01

    Acoustic Bessel beams are known to produce an axial radiation force on a sphere centered on the beam axis (on-axial configuration) that exhibits both repulsor and tractor behaviors. The repulsor and the tractor forces are oriented along the beam's direction of propagation and opposite to it, respectively. The behavior of the acoustic radiation force generated by Bessel beams when the sphere lies outside the beam's axis (off-axial configuration) is unknown. Using the 3-D radiation force formulas given in terms of the partial wave expansion coefficients for the incident and scattered waves, both axial and transverse components of the force exerted on a silicone- oil sphere are obtained for a zero- and a first-order Bessel vortex beam. As the sphere departs from the beam's axis, the tractor force becomes weaker. Moreover, the behavior of the transverse radiation force field may vary with the sphere's size factor ka (where k is the wavenumber and a is the sphere radius). Both stable and unstable equilibrium regions around the beam's axis are found, depending on ka values. These results are particularly important for the design of acoustical tractor beam devices operating with Bessel beams. PMID:25004483

  19. Radiative forcing over the conterminous United States due to contemporary land cover land use albedo change

    NASA Astrophysics Data System (ADS)

    Barnes, Christopher A.; Roy, David P.

    2008-05-01

    Recently available satellite land cover land use (LCLU) and albedo data are used to study the impact of LCLU change from 1973 to 2000 on surface albedo and radiative forcing for 36 ecoregions covering 43% of the conterminous United States (CONUS). Moderate Resolution Imaging Spectroradiometer (MODIS) snow-free broadband albedo values are derived from Landsat LCLU classification maps located using a stratified random sampling methodology to estimate ecoregion estimates of LCLU induced albedo change and surface radiative forcing. The results illustrate that radiative forcing due to LCLU change may be disguised when spatially and temporally explicit data sets are not used. The radiative forcing due to contemporary LCLU albedo change varies geographically in sign and magnitude, with the most positive forcings (up to 0.284 Wm-2) due to conversion of agriculture to other LCLU types, and the most negative forcings (as low as -0.247 Wm-2) due to forest loss. For the 36 ecoregions considered a small net positive forcing (i.e., warming) of 0.012 Wm-2 is estimated.

  20. Analysis of radiation exposure, Task Force RAZOR. Exercise Desert Rock VI, Operation Teapot. Technical report

    SciTech Connect

    Edwards, R.; Goetz, J.; Klemm, J.

    1983-07-15

    The radiation dose to Task Force RAZOR personnel participating in Shot Apple II of Operation Teapot, Exercise Desert Rock VI, is reconstructed. Task force personnel were exposed to initial radiation while in their vehicles or in trenches at the time of Apple II detonation. They were also exposed to residual radiation during their subsequent manuever and during an inspection of the equipment display area. The calculated total gamma doses to fully-participating Task Force RAZOR personnel range from about 0.8 rem to 1.8 rem. The highest dose was received by personnel of the armored infantry platoon on right flank nearest ground zero. Internal radiation dose commitments to maximally exposed personnel inside vehicles are estimated to be about 0.4 rem to the thyroid, 0.003 rem to the whole body, and 0.002 rem to the bone.

  1. The relationship between aerosol model uncertainty and radiative forcing uncertainty

    NASA Astrophysics Data System (ADS)

    Carslaw, Ken; Lee, Lindsay; Reddington, Carly

    2016-04-01

    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 aerosol-cloud forcing between pre-industrial and present day periods. One factor is the low sensitivity of present-day aerosol to natural emissions that determine the pre-industrial aerosol state. But 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, but this hides a range of very different aerosol models. These multiple so-called "equifinal" model variants predict a wide range of forcings. 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.

  2. Case Studies of the Vertical Structure of the Direct Shortwave Aerosol Radiative Forcing During TARFOX

    NASA Technical Reports Server (NTRS)

    Redemann, J.; Turco, R. P.; Liou, K. N.; Hobbs, P. V.; Hartley, W. S.; Bergstrom, R. W.; Browell, E. V.; Russell, P. B.

    2000-01-01

    The vertical structure of aerosol-induced radiative flux changes in the Earth's troposphere affects local heating rates and thereby convective processes, the formation and lifetime of clouds, and hence the distribution of chemical constituents. We present observationally-based estimates of the vertical structure of direct shortwave aerosol radiative forcing for two case studies from the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) which took place on the US East coast in July 1996. The aerosol radiative forcings are computed using the Fu-Liou broadband radiative transfer model. The aerosol optical properties used in the radiative transfer simulations are calculated from independent vertically-resolved estimates of the complex aerosol indices of refraction in two to three distinct vertical layers, using profiles of in situ particle size distributions measured aboard the University of Washington research aircraft. Aerosol single-scattering albedos at 450 nm thus determined range from 0.9 to 0.985, while the asymmetry factor varies from 0.6 to 0.8. The instantaneous shortwave aerosol radiative forcings derived from the optical profiles of the aerosols are of the order of -36 W/sq m at the top of the atmosphere and about -56 W/sq m at the surface for both case studies.

  3. Case Studies of the Vertical Structure of the Direct Shortwave Aerosol Radiative Forcing During TARFOX

    NASA Technical Reports Server (NTRS)

    Redemann, J.; Turco, R. P.; Liou, K. N.; Hobbs, P. V.; Hartley, W. S.; Bergstrom, R. W.; Browell, E. V.; Russell, P. B.

    2000-01-01

    The vertical structure of aerosol-induced radiative flux changes in the Earth's troposphere affects local heating rates and thereby convective processes, the formation and lifetime of clouds, and hence the distribution of chemical constituents. We present observationally based estimates of the vertical structure of direct shortwave aerosol radiative forcing for two case studies from the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) which took place on the U.S. east coast in July 1996. The aerosol radiative forcings are computed using the Fu-Liou broadband radiative transfer model. The aerosol optical properties used in the radiative transfer simulations are calculated from independent vertically resolved estimates of the complex aerosol indices of refraction in two to three distinct vertical layers, using profiles of in situ particle size distributions measured aboard the University of Washington research aircraft. Aerosol single-scattering albedos at 450 nm thus determined range from 0.9 to 0.985, while the asymmetry factor varies from 0.6 to 0.8. The instantaneous shortwave aerosol radiative forcings derived from the optical properties of the aerosols are of the order of -36 Wm(exp -2) at the top of the atmosphere and about -56 Wm(exp -2) at the surface for both case studies.

  4. Possible effects of protracted exposure on the additivity of risks from space radiations

    NASA Technical Reports Server (NTRS)

    Curtis, S. B.

    1996-01-01

    Conventional radiation risk assessments are presently based on the additivity assumption. This assumption states that risks from individual components of a complex radiation field involving many different types of radiation can be added to yield the total risk of the complex radiation field. If the assumption is not correct, the summations and integrations performed to obtain the presently quoted risk estimates are not appropriate. This problem is particularly important in the area of space radiation risk evaluation because of the many different types of high- and low-LET radiation present in the galactic cosmic ray environment. For both low- and high-LET radiations at low enough dose rates, the present convention is that the addivity assumption holds. Mathematically, the total risk, Rtot is assumed to be Rtot = summation (i) Ri where the summation runs over the different types of radiation present. If the total dose (or fluence) from each component is such that the interaction between biological lesions caused by separate single track traversals is negligible within a given cell, it is presently considered to be reasonable to accept the additivity assumption. However, when the exposure is protracted over many cell doubling times (as will be the case for extended missions to the moon or Mars), the possibility exists that radiation effects that depend on multiple cellular events over a long time period, such as is probably the case in radiation-induced carcinogenesis, may not be additive in the above sense and the exposure interval may have to be included in the evaluation procedure. It is shown, however, that "inverse" dose-rate effects are not expected from intermediate LET radiations arising from the galactic cosmic ray environment due to the "sensitive-window-in-the-cell-cycle" hypothesis.

  5. Demonstration of non-additivity and asymmetry in the lateral Casimir force

    NASA Astrophysics Data System (ADS)

    Chiu, Hsiang-Chih

    2009-10-01

    The Casimir effect is a purely quantum mechanical phenomenon which has drawn extensive attention in the last decade. With the rapid development of modern scientific instruments, it has been demonstrated and measured with unprecedented precision. Because of its unique dependence on the separation and geometry, the Casimir force is expected to play an important role in modern nano-electro-mechanical systems. An understanding of the shape dependence of the Casimir force and its control has become a very important research topic for the future nano-technology. Since the demonstration of the lateral Casimir force in 2002 at UC Riverside, this special effect has inspired a lot of theoretical research. The asymmetry of the lateral Casimir has been predicted and exact theories which take into account diffraction-like correlation effect between the scattered zero point photons from the boundaries have been proposed. We improved the experimental setup and experimental conditions (grating period of order of the separation distance) to study these new phenomenon. In this research, we demonstrate the asymmetrical lateral Casimir force for the first time. The experimental results show very good agreement with a recently developed exact theory based on the scattering approach with no tting parameters. The measured force also show the expected deviation from the commonly used proximity force approximation. The results provide a further understanding of the shape dependence of the Casimir force and will enhance the capabilities for its application in nano technology, especially for the frictionless transmission of lateral motion.

  6. Acoustic radiation force expressed using complex phase shifts and momentum-transfer cross sections.

    PubMed

    Zhang, Likun; Marston, Philip L

    2016-08-01

    Acoustic radiation force is expressed using complex phase shifts of partial wave scattering functions and the momentum-transfer cross section, herein incorporated into acoustics from quantum mechanisms. Imaginary parts of the phase shifts represent dissipation in the object and/or in the boundary layer adjacent to the object. The formula simplifies the force as summation of functions of complex phase shifts of adjacent partial waves involving differences of real parts and sums of imaginary parts, providing an efficient way of exploring the force parameter-space. The formula for the force is proportional to a generalized momentum-transfer cross section for plane waves and no dissipation. PMID:27586777

  7. 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)

  8. Role of radiatively forced temperature changes in enhanced semi-arid warming over East Asia

    NASA Astrophysics Data System (ADS)

    Guan, X.; Huang, J.; Guo, R.; Lin, P.; Zhang, Y.

    2015-08-01

    As the climate change occurred over East Asia since 1950s, intense interest and debate have arisen concerning the contribution of human activities to the warming observed in previous decades. In this study, we investigate surface temperature change using a recently developed methodology that can successfully identify and separate the dynamically induced temperature (DIT) and radiatively forced temperature (RFT) changes in raw surface air temperature (SAT) data. For regional averages, DIT and RFT make 43.7 and 56.3 % contributions to the SAT over East Asia, respectively. The DIT changes dominate the SAT decadal variability and are mainly determined by internal climate variability, such as the North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and Atlantic Multi-decadal Oscillation (AMO). The radiatively forced SAT changes made major contribution to the global-scale warming trend and the regional-scale enhanced semi-arid warming (ESAW). Such enhanced warming is also found in radiatively forced daily maximum and minimum SAT. The long-term global-mean SAT warming trend is mainly related to radiative forcing produced by global well-mixed greenhouse gases. The regional anthropogenic radiative forcing, however, caused the enhanced warming in the semi-arid region, which may be closely associated with local human activities. Finally, the relationship between global warming hiatus and regional enhanced warming is discussed.

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

    NASA Astrophysics Data System (ADS)

    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

    2016-05-01

    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.

  10. Ozone precursors have regionally variable effect on radiative forcing

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2013-02-01

    When released near the surface, carbon monoxide, assorted nitrogen oxides (NOx ), and nonmethane hydrocarbons (NMHC) contribute to the production of ozone, a key component of photochemical smog, which is known to have serious deleterious effects on human health. However, when ozone gets lifted into the troposphere, it is a greenhouse gas. That these ozone precursors have such a dual-pronged effect—affecting both human health and the global radiation budget—suggests that mitigating their emissions could be a potential method to both improve air quality and dampen the rate of anthropogenic climate change.

  11. 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.

  12. Global analysis of radiative forcing from fire-induced shortwave albedo change

    NASA Astrophysics Data System (ADS)

    López-Saldaña, G.; Bistinas, I.; Pereira, J. M. C.

    2015-01-01

    Land surface albedo, a key parameter to derive Earth's surface energy balance, is used in the parameterization of numerical weather prediction, climate monitoring and climate change impact assessments. Changes in albedo due to fire have not been fully investigated on a continental and global scale. The main goal of this study, therefore, is to quantify the changes in instantaneous shortwave albedo produced by biomass burning activities and their associated radiative forcing. The study relies on the MODerate-resolution Imaging Spectroradiometer (MODIS) MCD64A1 burned-area product to create an annual composite of areas affected by fire and the MCD43C2 bidirectional reflectance distribution function (BRDF) albedo snow-free product to compute a bihemispherical reflectance time series. The approximate day of burning is used to calculate the instantaneous change in shortwave albedo. Using the corresponding National Centers for Environmental Prediction (NCEP) monthly mean downward solar radiation flux at the surface, the global radiative forcing associated with fire was computed. The analysis reveals a mean decrease in shortwave albedo of -0.014 (1σ = 0.017), causing a mean positive radiative forcing of 3.99 Wm-2 (1σ = 4.89) over the 2002-20012 time period in areas affected by fire. The greatest drop in mean shortwave albedo change occurs in 2002, which corresponds to the highest total area burned (378 Mha) observed in the same year and produces the highest mean radiative forcing (4.5 Wm-2). Africa is the main contributor in terms of burned area, but forests globally give the highest radiative forcing per unit area and thus give detectable changes in shortwave albedo. The global mean radiative forcing for the whole period studied (~0.0275 Wm-2) shows that the contribution of fires to the Earth system is not insignificant.

  13. Importance of representing optical depth variability for estimates of global line-shaped contrail radiative forcing

    PubMed Central

    Kärcher, Bernd; Burkhardt, Ulrike; Ponater, Michael; Frömming, Christine

    2010-01-01

    Estimates of the global radiative forcing by line-shaped contrails differ mainly due to the large uncertainty in contrail optical depth. Most contrails are optically thin so that their radiative forcing is roughly proportional to their optical depth and increases with contrail coverage. In recent assessments, the best estimate of mean contrail radiative forcing was significantly reduced, because global climate model simulations pointed at lower optical depth values than earlier studies. We revise these estimates by comparing the probability distribution of contrail optical depth diagnosed with a climate model with the distribution derived from a microphysical, cloud-scale model constrained by satellite observations over the United States. By assuming that the optical depth distribution from the cloud model is more realistic than that from the climate model, and by taking the difference between the observed and simulated optical depth over the United States as globally representative, we quantify uncertainties in the climate model’s diagnostic contrail parameterization. Revising the climate model results accordingly increases the global mean radiative forcing estimate for line-shaped contrails by a factor of 3.3, from 3.5 mW/m2 to 11.6 mW/m2 for the year 1992. Furthermore, the satellite observations and the cloud model point at higher global mean optical depth of detectable contrails than often assumed in radiative transfer (off-line) studies. Therefore, we correct estimates of contrail radiative forcing from off-line studies as well. We suggest that the global net radiative forcing of line-shaped persistent contrails is in the range 8–20 mW/m2 for the air traffic in the year 2000. PMID:20974909

  14. Importance of representing optical depth variability for estimates of global line-shaped contrail radiative forcing.

    PubMed

    Kärcher, Bernd; Burkhardt, Ulrike; Ponater, Michael; Frömming, Christine

    2010-11-01

    Estimates of the global radiative forcing by line-shaped contrails differ mainly due to the large uncertainty in contrail optical depth. Most contrails are optically thin so that their radiative forcing is roughly proportional to their optical depth and increases with contrail coverage. In recent assessments, the best estimate of mean contrail radiative forcing was significantly reduced, because global climate model simulations pointed at lower optical depth values than earlier studies. We revise these estimates by comparing the probability distribution of contrail optical depth diagnosed with a climate model with the distribution derived from a microphysical, cloud-scale model constrained by satellite observations over the United States. By assuming that the optical depth distribution from the cloud model is more realistic than that from the climate model, and by taking the difference between the observed and simulated optical depth over the United States as globally representative, we quantify uncertainties in the climate model's diagnostic contrail parameterization. Revising the climate model results accordingly increases the global mean radiative forcing estimate for line-shaped contrails by a factor of 3.3, from 3.5 mW/m(2) to 11.6 mW/m(2) for the year 1992. Furthermore, the satellite observations and the cloud model point at higher global mean optical depth of detectable contrails than often assumed in radiative transfer (off-line) studies. Therefore, we correct estimates of contrail radiative forcing from off-line studies as well. We suggest that the global net radiative forcing of line-shaped persistent contrails is in the range 8-20 mW/m(2) for the air traffic in the year 2000. PMID:20974909

  15. Cytotoxic Effects of Temozolomide and Radiation are Additive- and Schedule-Dependent

    SciTech Connect

    Chalmers, Anthony J.; Ruff, Elliot M.; Martindale, Christine; Lovegrove, Nadia; Short, Susan C.

    2009-12-01

    Purpose: Despite aggressive therapy comprising radical radiation and temozolomide (TMZ) chemotherapy, the prognosis for patients with glioblastoma multiforme (GBM) remains poor, particularly if tumors express O{sup 6}-methylguanine-DNA-methyltransferase (MGMT). The interactions between radiation and TMZ remain unclear and have important implications for scheduling and for developing strategies to improve outcomes. Methods and Materials: Factors determining the effects of combination therapy on clonogenic survival, cell-cycle checkpoint signaling and DNA repair were investigated in four human glioma cell lines (T98G, U373-MG, UVW, U87-MG). Results: Combining TMZ and radiation yielded additive cytotoxicity, but only when TMZ was delivered 72 h before radiation. Radiosensitization was not observed. TMZ induced G2/M cell-cycle arrest at 48-72 h, coincident with phosphorylation of Chk1 and Chk2. Additive G2/M arrest and Chk1/Chk2 phosphorylation was only observed when TMZ preceded radiation by 72 h. The ataxia-telangiectasia mutated (ATM) inhibitor KU-55933 increased radiation sensitivity and delayed repair of radiation-induced DNA breaks, but did not influence TMZ effects. The multiple kinase inhibitor caffeine enhanced the cytotoxicity of chemoradiation and exacerbated DNA damage. Conclusions: TMZ is not a radiosensitizing agent but yields additive cytotoxicity in combination with radiation. Our data indicate that TMZ treatment should commence at least 3 days before radiation to achieve maximum benefit. Activation of G2/M checkpoint signaling by TMZ and radiation has a cytoprotective effect that can be overcome by dual inhibition of ATM and ATR. More specific inhibition of checkpoint signaling will be required to increase treatment efficacy without exacerbating toxicity.

  16. Radiation Pressure Force from Optical Cycling on a Polyatomic Molecule SrOH

    NASA Astrophysics Data System (ADS)

    Kozyryev, Ivan; Baum, Louis; Matsuda, Kyle; Sedlack, Alex; Hemmerling, Boerge; Doyle, John

    2016-05-01

    Polyatomic molecules hold promise for many applications in physics and chemistry due to their rotational and vibrational degrees of freedom. The starting point for our approach to the production of ultracold strontium monohydroxide (SrOH) is buffer-gas cooling followed by laser manipulation. Linear geometry, diagonal Franck-Condon factors, short radiative lifetimes and unresolved hyperfine splittings make SrOH a particularly attractive candidate for direct laser cooling. We report deflection of the SrOH beam through radiative force from optical cycling on the X~2Σ+ <-->Ã2Π1 / 2 transition. We observe × 12 fluorescence enhancement with closed spin-rotation splitting and demonstrate cycling between different vibrational levels with the Sr <--> O mode repumping laser. Observed deflection and detection signals correspond to the scattering of ~ 100 photons. Additional repumping laser for the bending mode would lead to scattering of ~ 1 , 000 photons allowing for transverse laser cooling of the SrOH beam. We will also describe our experimental efforts towards laser slowing and trapping of SrOH.

  17. United States Land Cover Land Use Change, Albedo and Surface Radiative Forcing 1973 to 2000

    NASA Astrophysics Data System (ADS)

    Barnes, C. A.; Roy, D. P.

    2007-12-01

    This research responds to the recent recommendations made by the U.S. National Research Council for regional forcing studies to better understand climatic responses to land cover land use change. Surface albedo affects the earth's radiative energy balance, by controlling how much incoming solar radiation is absorbed and reflected. It is well established that Land Cover Land Use (LCLU) change results in changes in the surface albedo which has a radiative forcing effect, however, to date, studies have been limited due to data uncertainties. New spatially explicit satellite derived LCLU change and albedo data for the conterminous U.S. are used to study the impact of LCLU change from 1973 to 2000 on surface albedo and radiative forcing. The methodology and preliminary results for 42% of the U.S. processed to date are presented as spatially explicit maps and summary statistics. The results indicate a negative (cooling) radiative forcing effect due to U.S. LCLU change over the last three decades. Data used include USGS Landsat based decadal land cover maps of the conterminous U.S. located using a stratified sampling methodology across 84 ecoregions, mean 2000-2002 MODIS broadband albedo values extracted in each ecoregion for the 10 mapped LCLU classes, and monthly mean surface incoming solar radiation from the recent European Center for Medium Range Weather Forecast 40 year Reanalysis (ERA40) product.

  18. Contrail radiative forcing over the Northern Hemisphere from 2006 Aqua MODIS data

    NASA Astrophysics Data System (ADS)

    Spangenberg, Douglas A.; Minnis, Patrick; Bedka, Sarah T.; Palikonda, Rabindra; Duda, David P.; Rose, Fred G.

    2013-02-01

    Abstract <span class="hlt">Radiative</span> <span class="hlt">forcing</span> due to linear-shaped jet contrails is calculated over the Northern Hemisphere for four seasonal months using 2006 Aqua Moderate-resolution Imaging Spectroradiometer cloud and contrail property retrieval data in a <span class="hlt">radiative</span> transfer model. The 4 month mean shortwave, longwave, and net <span class="hlt">radiative</span> <span class="hlt">forcings</span> normalized to 100% contrail cover are -5.7, 14.2, and 8.5 Wm-2. Mean total net <span class="hlt">forcing</span> over the northern half of the globe varies from 9.1 mW m-2 during October to 12.1 mW m-2 in January and is only representative at 01:30 and 13:30 LT in nonpolar regions. In some dense flight traffic corridors, the mean net <span class="hlt">forcing</span> approaches 80 mW m-2. Scaling the 4 month average of 10.6 mW m-2 to the Southern Hemisphere air traffic yields global mean net <span class="hlt">forcing</span> of 5.7 mW m-2, which is smaller than most model estimates. Nighttime net <span class="hlt">forcing</span> is 3.6 times greater than during daytime, when net <span class="hlt">forcing</span> is greatest over low clouds. Effects from contrail cirrus clouds that evolve from linear contrails are not considered in these results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AtmEn.125..512S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AtmEn.125..512S"><span id="translatedtitle">Seasonal differences in aerosol abundance and <span class="hlt">radiative</span> <span class="hlt">forcing</span> in months of contrasting emissions and rainfall over northern South Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sadavarte, P.; Venkataraman, C.; Cherian, R.; Patil, N.; Madhavan, B. L.; Gupta, T.; Kulkarni, S.; Carmichael, G. R.; Adhikary, B.</p> <p>2016-01-01</p> <p>A modeling framework was used to examine gaps in understanding of seasonal and spatial heterogeneity in aerosol abundance and <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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, <span class="hlt">additionally</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> and heating rate, calculated from OPAC-SBDART, using modeled aerosol fields, and corrected by MODIS AOD observations, showed regionally uniform atmospheric <span class="hlt">forcing</span> in April, compared to that in other months, influenced by both dust and black carbon abundance. A strong spatial heterogeneity of <span class="hlt">radiative</span> <span class="hlt">forcing</span> and heating rate was found, with factor of 2.5-3.5 lower atmospheric <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011AIPC.1315..227D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011AIPC.1315..227D&link_type=ABSTRACT"><span id="translatedtitle">Sealing <span class="hlt">Force</span> Increasing of ACM Gasket through Electron Beam <span class="hlt">Radiation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>dos Santos, D. J.; Batalha, G. F.</p> <p>2011-01-01</p> <p>Rubber is an engineering material largely used as sealing parts, in form of O-rings, solid gaskets and liquid gaskets, materials applied in liquid state with posterior vulcanization and sealing. Stress relaxation is a rubber characteristic which impacts negatively in such industrial applications (rings and solid gaskets). This work has the purpose to investigate the use of electron beam <span class="hlt">radiation</span> (EB) as a technology able to decrease the stress relaxation in acrylic rubber (ACM), consequently increasing the sealing capability of this material. ACM samples were irradiated with dose of 100 kGy and 250 kGy, its behavior was comparatively investigated using, dynamic mechanical analysis (DMA) and compression stress relaxation (CSR) experiments. The results obtained by DMA shown an increase of Tg and changes in dynamic mechanical behavior.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22305805','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22305805"><span id="translatedtitle">Acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on a double-layer microsphere by a Gaussian focused beam</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wu, Rongrong; Cheng, Kaixuan; Liu, Jiehui; Mao, Yiwei; Gong, Xiufen; Liu, Xiaozhou</p> <p>2014-10-14</p> <p>A new model for calculating the <span class="hlt">radiation</span> <span class="hlt">force</span> on double-layer microsphere is proposed based on the ray acoustics approach. The axial acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> resulting from a focused Gaussian beam incident on spherical shells immersed in water is examined theoretically in relation to its thickness and the contents of its double-layer. The attenuation both in the water and inside the sphere is considered in this method, which cannot be ignored while the high frequency ultrasonic is used. Results of numerical calculations are presented for fat and low density polyethylene materials, with the hollow region filled with animal oil, water, or air. These results show how the acoustic impedance and the sound velocity of both layers, together with the thickness of the shell, affect the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JaJAP..49gHF11K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JaJAP..49gHF11K"><span id="translatedtitle">Production of Local Acoustic <span class="hlt">Radiation</span> <span class="hlt">Force</span> to Constrain Direction of Microcapsules in Flow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kohji Masuda,; Nobuyuki Watarai,; Ryusuke Nakamoto,; Yusuke Muramatsu,</p> <p>2010-07-01</p> <p>We have ever reported our attempt to control the direction of microcapsules in flow by acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>. However, the diameter of capsules was too large to be applied in vivo. Furthermore, the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> affected only the focal area because focused ultrasound was used. Thus, we have improved our experiment by using microcapsules as small as blood cells and introducing a plane wave of ultrasound. We prepared an artificial blood vessel including a Y-form bifurcation established in two observation areas. Then, we newly defined the induction index to evaluate the difference in capsule density in two downstream paths. As a result, the optimum angle of ultrasound emission to induct to the desired path was derived. The induction index increased in proportion to the central frequency of ultrasound, which is affected by the aggregation of capsules to receive more acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JAP...116n4903W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JAP...116n4903W"><span id="translatedtitle">Acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on a double-layer microsphere by a Gaussian focused beam</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wu, Rongrong; Cheng, Kaixuan; Liu, Xiaozhou; Liu, Jiehui; Mao, Yiwei; Gong, Xiufen</p> <p>2014-10-01</p> <p>A new model for calculating the <span class="hlt">radiation</span> <span class="hlt">force</span> on double-layer microsphere is proposed based on the ray acoustics approach. The axial acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> resulting from a focused Gaussian beam incident on spherical shells immersed in water is examined theoretically in relation to its thickness and the contents of its double-layer. The attenuation both in the water and inside the sphere is considered in this method, which cannot be ignored while the high frequency ultrasonic is used. Results of numerical calculations are presented for fat and low density polyethylene materials, with the hollow region filled with animal oil, water, or air. These results show how the acoustic impedance and the sound velocity of both layers, together with the thickness of the shell, affect the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22492632','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22492632"><span id="translatedtitle">Acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> due to arbitrary incident fields on spherical particles in soft tissue</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Treweek, Benjamin C. Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F.</p> <p>2015-10-28</p> <p>Acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> is of interest in a wide variety of biomedical applications ranging from tissue characterization (e.g. elastography) to tissue treatment (e.g. high intensity focused ultrasound, kidney stone fragment removal). As tissue mechanical properties are reliable indicators of tissue health, the former is the focus of the present contribution. This is accomplished through an investigation of the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on a spherical scatterer embedded in tissue. Properties of both the scatterer and the surrounding tissue are important in determining the magnitude and the direction of the <span class="hlt">force</span>. As these properties vary, the <span class="hlt">force</span> computation shows changes in magnitude and direction, which may enable more accurate noninvasive determination of tissue properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1685d0008T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1685d0008T"><span id="translatedtitle">Acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> due to arbitrary incident fields on spherical particles in soft tissue</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Treweek, Benjamin C.; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F.</p> <p>2015-10-01</p> <p>Acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> is of interest in a wide variety of biomedical applications ranging from tissue characterization (e.g. elastography) to tissue treatment (e.g. high intensity focused ultrasound, kidney stone fragment removal). As tissue mechanical properties are reliable indicators of tissue health, the former is the focus of the present contribution. This is accomplished through an investigation of the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on a spherical scatterer embedded in tissue. Properties of both the scatterer and the surrounding tissue are important in determining the magnitude and the direction of the <span class="hlt">force</span>. As these properties vary, the <span class="hlt">force</span> computation shows changes in magnitude and direction, which may enable more accurate noninvasive determination of tissue properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015NatSR...513485S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015NatSR...513485S&link_type=ABSTRACT"><span id="translatedtitle">Experimental Demonstration of a Synthetic Lorentz <span class="hlt">Force</span> by Using <span class="hlt">Radiation</span> Pressure</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Šantić, N.; Dubček, T.; Aumiler, D.; Buljan, H.; Ban, T.</p> <p>2015-09-01</p> <p>Synthetic magnetism in cold atomic gases opened the doors to many exciting novel physical systems and phenomena. Ubiquitous are the methods used for the creation of synthetic magnetic fields. They include rapidly rotating Bose-Einstein condensates employing the analogy between the Coriolis and the Lorentz <span class="hlt">force</span>, and laser-atom interactions employing the analogy between the Berry phase and the Aharonov-Bohm phase. Interestingly, <span class="hlt">radiation</span> pressure - being one of the most common <span class="hlt">forces</span> induced by light - has not yet been used for synthetic magnetism. We experimentally demonstrate a synthetic Lorentz <span class="hlt">force</span>, based on the <span class="hlt">radiation</span> pressure and the Doppler effect, by observing the centre-of-mass motion of a cold atomic cloud. The <span class="hlt">force</span> is perpendicular to the velocity of the cold atomic cloud, and zero for the cloud at rest. Our novel concept is straightforward to implement in a large volume, for a broad range of velocities, and can be extended to different geometries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4556972','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4556972"><span id="translatedtitle">Experimental Demonstration of a Synthetic Lorentz <span class="hlt">Force</span> by Using <span class="hlt">Radiation</span> Pressure</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Šantić, N.; Dubček, T.; Aumiler, D.; Buljan, H.; Ban, T.</p> <p>2015-01-01</p> <p>Synthetic magnetism in cold atomic gases opened the doors to many exciting novel physical systems and phenomena. Ubiquitous are the methods used for the creation of synthetic magnetic fields. They include rapidly rotating Bose-Einstein condensates employing the analogy between the Coriolis and the Lorentz <span class="hlt">force</span>, and laser-atom interactions employing the analogy between the Berry phase and the Aharonov-Bohm phase. Interestingly, <span class="hlt">radiation</span> pressure - being one of the most common <span class="hlt">forces</span> induced by light - has not yet been used for synthetic magnetism. We experimentally demonstrate a synthetic Lorentz <span class="hlt">force</span>, based on the <span class="hlt">radiation</span> pressure and the Doppler effect, by observing the centre-of-mass motion of a cold atomic cloud. The <span class="hlt">force</span> is perpendicular to the velocity of the cold atomic cloud, and zero for the cloud at rest. Our novel concept is straightforward to implement in a large volume, for a broad range of velocities, and can be extended to different geometries. PMID:26330327</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26330327','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26330327"><span id="translatedtitle">Experimental Demonstration of a Synthetic Lorentz <span class="hlt">Force</span> by Using <span class="hlt">Radiation</span> Pressure.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Šantić, N; Dubček, T; Aumiler, D; Buljan, H; Ban, T</p> <p>2015-01-01</p> <p>Synthetic magnetism in cold atomic gases opened the doors to many exciting novel physical systems and phenomena. Ubiquitous are the methods used for the creation of synthetic magnetic fields. They include rapidly rotating Bose-Einstein condensates employing the analogy between the Coriolis and the Lorentz <span class="hlt">force</span>, and laser-atom interactions employing the analogy between the Berry phase and the Aharonov-Bohm phase. Interestingly, <span class="hlt">radiation</span> pressure - being one of the most common <span class="hlt">forces</span> induced by light - has not yet been used for synthetic magnetism. We experimentally demonstrate a synthetic Lorentz <span class="hlt">force</span>, based on the <span class="hlt">radiation</span> pressure and the Doppler effect, by observing the centre-of-mass motion of a cold atomic cloud. The <span class="hlt">force</span> is perpendicular to the velocity of the cold atomic cloud, and zero for the cloud at rest. Our novel concept is straightforward to implement in a large volume, for a broad range of velocities, and can be extended to different geometries. PMID:26330327</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050180337','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050180337"><span id="translatedtitle">Atmospheric Teleconnection over Eurasia Induced by Aerosol <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> During Boreal Spring</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kim, Maeng-Ki; Lau, K. M.; Chin, Mian; Kim, Kyu-Myong; Sud, Y. C.; Walker, Greg K.</p> <p>2005-01-01</p> <p>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 <span class="hlt">Radiation</span> and Transport model (GOCART). The aerosol extinction coefficient, single scattering albedo, and asymmetric factor are computed as wavelength-dependent <span class="hlt">radiative</span> <span class="hlt">forcing</span> in the <span class="hlt">radiative</span> 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. <span class="hlt">Additionally</span>, 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AtmEn..44.3066P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AtmEn..44.3066P"><span id="translatedtitle">On the contribution of black carbon to the composite aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> over an urban environment</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Panicker, A. S.; Pandithurai, G.; Safai, P. D.; Dipu, S.; Lee, Dong-In</p> <p>2010-08-01</p> <p>This paper discusses the extent of Black Carbon (BC) <span class="hlt">radiative</span> <span class="hlt">forcing</span> in the total aerosol atmospheric <span class="hlt">radiative</span> <span class="hlt">forcing</span> over Pune, an urban site in India. Collocated measurements of aerosol optical properties, chemical composition and BC were carried out for a period of six months (during October 2004 to May 2005) over the site. Observed aerosol chemical composition in terms of water soluble, insoluble and BC components were used in Optical Properties of Aerosols and Clouds (OPAC) to derive aerosol optical properties of composite aerosols. The BC fraction alone was used in OPAC to derive optical properties of BC aerosols. The aerosol optical properties for composite and BC aerosols were separately used in SBDART model to derive direct aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> due to composite and BC aerosols. The atmospheric <span class="hlt">radiative</span> <span class="hlt">forcing</span> for composite aerosols were found to be +35.5, +32.9 and +47.6 Wm -2 during post-monsoon, winter and pre-monsoon seasons, respectively. The average BC mass fraction found to be 4.83, 6.33 and 4 μg m -3 during the above seasons contributing around 2.2 to 5.8% to the total aerosol load. The atmospheric <span class="hlt">radiative</span> <span class="hlt">forcing</span> estimated due to BC aerosols was +18.8, +23.4 and +17.2 Wm -2, respectively during the above seasons. The study suggests that even though BC contributes only 2.2-6% to the total aerosol load; it is contributing an average of around 55% to the total lower atmospheric aerosol <span class="hlt">forcing</span> due to strong <span class="hlt">radiative</span> absorption, and thus enhancing greenhouse warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000013616&hterms=aerosols+desert&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Daerosols%2Bdesert','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000013616&hterms=aerosols+desert&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Daerosols%2Bdesert"><span id="translatedtitle">Global Aerosol <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> Derived from Sea WiFS-Inferred Aerosol Optical Properties</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chou, Ming-Dah; Chan, Pui-King; Wang, Menghua</p> <p>1999-01-01</p> <p>Aerosol optical properties inferred from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) radiance measurements are used to compute the aerosol shortwave <span class="hlt">radiative</span> <span class="hlt">forcing</span> using a <span class="hlt">radiative</span> 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 <span class="hlt">radiative</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> is computed over global oceans for four months (January, April, July, and October, 1998) to represent four seasons. It is found that the aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> is approximately 7 W/sq m at the top of the atmosphere. This large <span class="hlt">radiative</span> <span class="hlt">forcing</span> is expected to have a significant cooling effect on the Earth's climate as implied from simulations of a number of general circulation models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4746633','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4746633"><span id="translatedtitle">Quantitative assessment of <span class="hlt">radiation</span> <span class="hlt">force</span> effect at the dielectric air-liquid interface</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Capeloto, Otávio Augusto; Zanuto, Vitor Santaella; Malacarne, Luis Carlos; Baesso, Mauro Luciano; Lukasievicz, Gustavo Vinicius Bassi; Bialkowski, Stephen Edward; Astrath, Nelson Guilherme Castelli</p> <p>2016-01-01</p> <p>We induce nanometer-scale surface deformation by exploiting momentum conservation of the interaction between laser light and dielectric liquids. The effect of <span class="hlt">radiation</span> <span class="hlt">force</span> at the air-liquid interface is quantitatively assessed for fluids with different density, viscosity and surface tension. The imparted pressure on the liquids by continuous or pulsed laser light excitation is fully described by the Helmholtz electromagnetic <span class="hlt">force</span> density. PMID:26856622</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20080032559&hterms=General+chemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DGeneral%2Bchemistry','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20080032559&hterms=General+chemistry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DGeneral%2Bchemistry"><span id="translatedtitle">Global <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> of Coupled Tropospheric Ozone and Aerosols in a Unified General Circulation Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liao, Hong; Seinfeld, John H.; Adams, Peter J.; Mickley, Loretta J.</p> <p>2008-01-01</p> <p>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, <span class="hlt">radiative</span> <span class="hlt">forcing</span>, 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> by tropospheric ozone and all natural and anthropogenic aerosol components. The global annual mean value of the <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> of aerosols by 17% and influence global mean TOA <span class="hlt">forcing</span> of tropospheric ozone by 15%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20000052534&hterms=effects+columns&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Deffects%2Bcolumns','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20000052534&hterms=effects+columns&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Deffects%2Bcolumns"><span id="translatedtitle">Aerosol Climate Effects: Local <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> and Column Closure Experiments</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Russell, P. B.; Bergstrom, Robert W.; Kinne, S. A.</p> <p>2000-01-01</p> <p>In an effort to reduce uncertainties in climate change predictions, experiments are being planned and conducted to measure anthropogenic aerosol properties and effects, including effects on <span class="hlt">radiative</span> fields. The global average, direct anthropogenic aerosol effect on upwelling shortwave fluxes is estimated to be about +1/2 W/sq m, whereas errors in flux changes measured with airborne and spaceborne radiometers are 2 to 8 W/sq m or larger. This poses the question of whether flux changes expected in field experiments will be large enough to measure accurately. This paper obtains a new expression for the aerosol-induced change in upwelling flux, compares it to two-stream and adding-doubling (AD) results, and uses all three methods to estimate expected flux changes. The new expression accounts for the solar zenith angle dependences of aerosol transmission and reflection, as well as of surface albedo, all of which can have a strong effect in determining flux changes measured in field experiments. Despite its relative simplicity, the new expression gives results similar to previous two-stream results. Relative to AD results, it agrees within a few watts per square meter for the intermediate solar elevation angles where the flux changes peak (roughly 10 to 30 degrees), but it has negative errors for higher Sun and positive errors for lower Sun. All three techniques yield aerosol-induced changes in upwelling flux of +8 to +50 W/sq m for aerosol midvisible optical depths of 0.1 to 0.5. Because such aerosol optical depths occur frequently off the U.S. and European Atlantic coasts in summer, the flux changes they induce should be measurable by airborne, and possibly by spaceborne, radiometers, provided sufficient care is taken in experiment design (including measurements to separate aerosol <span class="hlt">radiative</span> effects from those of absorbing gases). The expected flux changes are about 15 to 100 times larger than the global average flux change expected for the global average</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGC21B0887B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGC21B0887B"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">Forcing</span> over the Conterminous United States due to 1973 to 2000 Land Cover Albedo Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barnes, C. A.; Roy, D. P.</p> <p>2011-12-01</p> <p>Satellite derived land cover land use (LCLU), snow and albedo data, and incoming surface solar <span class="hlt">radiation</span> reanalysis data, were used to study the impact of LCLU change on surface albedo and <span class="hlt">radiative</span> <span class="hlt">forcing</span> for 84 ecoregions across the conterminous United States. A net continental scale negative <span class="hlt">radiative</span> <span class="hlt">forcing</span> of -0.008 Wm-2 due to LCLU albedo change from 1973 to 2000 was estimated associated with decreasing agricultural and forested land and increasing developed land. The <span class="hlt">radiative</span> <span class="hlt">forcing</span> for individual ecoregions varied geographically in sign and magnitude, with the most negative (as low as -1.303 Wm-2) due to forest loss and the most positive <span class="hlt">forcings</span> (up to 0.358 Wm-2) due to the conversion of grassland/shrub. In snow prone ecoregions, where the dominant LCLU transitions were between snow-hiding (e.g., forest) and snow-revealing (e.g., agriculture) LCLU classes, the negative and positive ecoregion <span class="hlt">forcing</span> estimates were amplified. The results make an important contribution to advancing understanding of the role of LCLU change on the climate system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22258593','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22258593"><span id="translatedtitle">Confocal acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> optical coherence elastography using a ring ultrasonic transducer</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Qi, Wenjuan; Li, Rui; Ma, Teng; Kirk Shung, K.; Zhou, Qifa; Chen, Zhongping</p> <p>2014-03-24</p> <p>We designed and developed a confocal acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> optical coherence elastography system. A ring ultrasound transducer was used to achieve reflection mode excitation and generate an oscillating acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> in order to generate displacements within the tissue, which were detected using the phase-resolved optical coherence elastography method. Both phantom and human tissue tests indicate that this system is able to sense the stiffness difference of samples and quantitatively map the elastic property of materials. Our confocal setup promises a great potential for point by point elastic imaging in vivo and differentiation of diseased tissues from normal tissue.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22492626','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22492626"><span id="translatedtitle">Tunable optical lens array using viscoelastic material and acoustic <span class="hlt">radiation</span> <span class="hlt">force</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Koyama, Daisuke Kashihara, Yuta; Matsukawa, Mami; Hatanaka, Megumi; Nakamura, Kentaro</p> <p>2015-10-28</p> <p>A movable optical lens array that uses acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> was investigated. The lens array consists of a glass plate, two piezoelectric bimorph transducers, and a transparent viscoelastic gel film. A cylindrical lens array with a lens pitch of 4.6 mm was fabricated using the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> generated by the flexural vibration of the glass plate. The focal point and the positioning of the lenses can be changed using the input voltage and the driving phase difference between the two transducers, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1986PhRvD..34..452B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1986PhRvD..34..452B"><span id="translatedtitle">Classical extended charge subjected to linear <span class="hlt">forces</span> and Rayleigh-Jeans <span class="hlt">radiation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blanco, R.; Pesquera, L.; Jimenez, J. L.</p> <p>1986-07-01</p> <p>We study a rigid classical extended charge in the nonrelativistic approximation, first subjected to a linear <span class="hlt">force</span>, and second immersed in an electromagnetic <span class="hlt">radiation</span> with a Rayleigh-Jeans (RJ) spectrum. A Yukawa distribution is considered for the charge, when necessary, to get explicit results. A comparison with the Abraham-Lorentz (AL) model is made. Our results show that the AL model is a good approximation for the extended charge only if the external <span class="hlt">forces</span> do not contain high frequencies. However, if we consider RJ <span class="hlt">radiation</span> big discrepancies appear. We also find that the linear system follows the Maxwell-Boltzmann law only for large enough values of the radius.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMGC43A1030W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMGC43A1030W"><span id="translatedtitle">Contributions of projected land use to global <span class="hlt">radiative</span> <span class="hlt">forcing</span> ascribed to local sources</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ward, D. S.; Mahowald, N. M.; Kloster, S.</p> <p>2013-12-01</p> <p>With global demand for food expected to dramatically increase and put <span class="hlt">additional</span> pressures on natural lands, there is a need to understand the environmental impacts of land use and land cover change (LULCC). Previous studies have shown that the magnitude and even the sign of the <span class="hlt">radiative</span> <span class="hlt">forcing</span> (RF) of biogeophysical effects from LULCC depends on the latitude and forest ecology of the disturbed region. Here we ascribe the contributions to the global RF by land-use related anthropogenic activities to their local sources, organized on a grid of 1.9 degrees latitude by 2.5 degrees longitude. We use RF estimates for the year 2100, using five future LULCC projections, computed from simulations with the National Center for Atmospheric Research Community Land Model and Community Atmosphere Models and <span class="hlt">additional</span> offline analyses. Our definition of the LULCC RF includes changes to terrestrial carbon storage, methane and nitrous oxide emissions, atmospheric chemistry, aerosol emissions, and surface albedo. We ascribe the RF to gridded locations based on LULCC-related emissions of relevant trace gases and aerosols, including emissions from fires. We find that the largest contributions to the global RF in year 2100 from LULCC originate in the tropics for all future scenarios. In fact, LULCC is the largest tropical source of anthropogenic RF. The LULCC RF in the tropics is dominated by emissions of CO2 from deforestation and methane emissions from livestock and soils. Land surface albedo change is rarely the dominant <span class="hlt">forcing</span> agent in any of the future LULCC projections, at any location. By combining the five future scenarios we find that deforested area at a specific tropical location can be used to predict the contribution to global RF from LULCC at that location (the relationship does not hold as well in the extratropics). This information could support global efforts like REDD (Reducing Emissions from Deforestation and Forest Degradation), that aim to reduce greenhouse gas</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JaJAP..55gLB05C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016JaJAP..55gLB05C&link_type=ABSTRACT"><span id="translatedtitle"><span class="hlt">Radiative</span> properties of ceramic metal-halide high intensity discharge lamps containing <span class="hlt">additives</span> in argon plasma</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cressault, Yann; Teulet, Philippe; Zissis, Georges</p> <p>2016-07-01</p> <p>The lighting represents a consumption of about 19% of the world electricity production. We are thus searching new effective and environment-friendlier light sources. The ceramic metal-halide high intensity lamps (C-MHL) are one of the options for illuminating very high area. The new C-MHL lamps contain <span class="hlt">additives</span> species that reduce mercury inside and lead to a richer spectrum in specific spectral intervals, a better colour temperature or colour rendering index. This work is particularly focused on the power <span class="hlt">radiated</span> by these lamps, estimated using the net emission coefficient, and depending on several <span class="hlt">additives</span> (calcium, sodium, tungsten, dysprosium, and thallium or strontium iodides). The results show the strong influence of the <span class="hlt">additives</span> on the power <span class="hlt">radiated</span> despite of their small quantity in the mixtures and the increase of visible <span class="hlt">radiation</span> portion in presence of dysprosium.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19930062015&hterms=Byung&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DByung','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19930062015&hterms=Byung&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DByung"><span id="translatedtitle">Intercomparison of observed cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> - A zonal and global perspective</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sohn, Byung-Ju; Robertson, Franklin R.</p> <p>1993-01-01</p> <p>Cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> determined by the Earth <span class="hlt">Radiation</span> Budget Experiment (ERBE) scene identification method and two regression methods is compared using identical data sources and the same analysis periods. Results confirm that from the global perspective the increased reflection of SW <span class="hlt">radiation</span> induced by clouds is greater than outgoing longwave energy trapped by clouds. The estimates of net effect obtained from the three methods are found to be in good agreement (within 3.5 W/sq m). It is concluded that differences in published global mean values of net cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> are mainly due to different data sources and analysis periods. The best estimated annual mean among all previous estimates is considered to be the ERBE measurement (-17.3 W/sq m).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27254398','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27254398"><span id="translatedtitle">Acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> and torque exerted on a small viscoelastic particle in an ideal fluid.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Leão-Neto, J P; Silva, G T</p> <p>2016-09-01</p> <p>We provide a detailed analysis on the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> and torque exerted on a homogeneous viscoelastic particle in the long-wave limit (i.e. the particle radius is much smaller than the incident wavelength) by an arbitrary wave. We assume that the particle behaves as a linear viscoelastic solid, which obeys the fractional Kelvin-Voigt model. Simple analytical expressions for the <span class="hlt">radiation</span> <span class="hlt">force</span> and torque are obtained. The developed theory is used to describe the interaction of acoustic waves (traveling and standing plane waves, and zero- and first-order Bessel beams) in the MHz-range with polymeric particles, namely lexan, low-density (LDPE) and high-density (HDPE) polyethylene. We found that particle absorption is chiefly the cause of the <span class="hlt">radiation</span> <span class="hlt">force</span> due to a traveling plane wave and zero-order Bessel beam when the frequency is smaller than 5MHz (HDPE), 3.9MHz (LDPE), and 0.9MHz (lexan). Whereas in a standing wave field, the <span class="hlt">radiation</span> <span class="hlt">force</span> is mildly changed due to dispersion inside the particle. We also show that the <span class="hlt">radiation</span> torque caused by a first-order Bessel beam varies nearly quadratic with frequency. These findings may enable new possibilities of particle handling in acoustophoretic techniques. PMID:27254398</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014GeoRL..41.1665H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014GeoRL..41.1665H&link_type=ABSTRACT"><span id="translatedtitle">The implication of <span class="hlt">radiative</span> <span class="hlt">forcing</span> and feedback for meridional energy transport</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, Yi; Zhang, Minghong</p> <p>2014-03-01</p> <p>The distributions of <span class="hlt">radiative</span> <span class="hlt">forcing</span> and feedback in the Coupled Model Intercomparison Project phase 5 abrupt4xCO2 and Historical experiments are diagnosed, with a focus on their effects on the zonal mean structure of the top-of-the-atmosphere <span class="hlt">radiation</span> anomalies and implications for the meridional energy transport. It is found that because the greenhouse gas longwave <span class="hlt">forcing</span> peaks in the low latitudes, it reinforces the equator-to-pole net <span class="hlt">radiation</span> gradient and accounts for the increase in the poleward energy transport in both hemispheres under global warming. The shortwave <span class="hlt">forcing</span> by aerosol, ozone, etc. peaks in the Northern Hemisphere and instead implies an interhemispheric energy transport. Although the water vapor feedback also reinforces the equator-to-pole gradient of the net <span class="hlt">radiation</span>, the temperature and albedo feedback act against it. The feedback tend to offset the zonal mean <span class="hlt">radiation</span> anomaly caused by the <span class="hlt">forcing</span>, although the overall feedback effect on the energy transport is rather uncertain, mainly due to the uncertainty in the cloud feedback.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/15002314','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/15002314"><span id="translatedtitle">A Physically-Based Estimate of <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> by Anthropogenic Sulfate Aerosol</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>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.)</p> <p>2001-04-01</p> <p>Estimates of direct and indirect <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> due to anthropogenic sulfate are estimated to be -0.3 to -0.5 and -1.5 to -3.0 W m-2, respectively. The <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> is due to changes in droplet radius and half to increased cloud liquid water.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000JGR...105.6903N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000JGR...105.6903N"><span id="translatedtitle">Consistent sets of atmospheric lifetimes and <span class="hlt">radiative</span> <span class="hlt">forcings</span> on climate for CFC replacements: HCFCs and HFCs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Naik, Vaishali; Jain, Atul K.; Patten, Kenneth O.; Wuebbles, Donald J.</p> <p>2000-03-01</p> <p>Recognition of deleterious effects of chlorine and bromine on ozone and climate over the last several decades has resulted in international accords to halt the production of chlorine-containing chlorofluorocarbons (CFCs) and bromine-containing halons. It is well recognized, however, that these chemicals have had important uses to society, particularly as refrigerants, as solvents, as plastic blowing agents, as fire retardants and as aerosol propellants. This has led to an extensive search for substitute chemicals with appropriate properties to be used in place of the CFCs and halons. The purpose of this study is to evaluate in a consistent manner the atmospheric lifetime and <span class="hlt">radiative</span> <span class="hlt">forcing</span> on climate for a number of replacement compounds. The unique aspect of this study is its attempt to resolve inconsistencies in previous evaluations of atmospheric lifetimes and <span class="hlt">radiative</span> <span class="hlt">forcings</span> for these compounds by adopting a uniform approach. Using the latest version of our two-dimensional chemical-<span class="hlt">radiative</span>-transport model of the global atmosphere, we have determined the atmospheric lifetimes of 28 hydrohalocarbons (HCFCs and HFCs). Through the comparison of the model-calculated lifetimes with lifetimes derived using a simple scaling method, our study adds to earlier findings that consideration of stratospheric losses is important in determining the lifetimes of gases. Discrepancies were found in the reported lifetimes of several replacement compounds reported in the international assessment of stratospheric ozone published by the World Meteorological Organization [Granier et al., 1999] and have been resolved. We have also derived the adjusted and instantaneous <span class="hlt">radiative</span> <span class="hlt">forcings</span> for CFC-11 and 20 other halocarbons using our <span class="hlt">radiative</span> transfer model. The sensitivity of <span class="hlt">radiative</span> <span class="hlt">forcings</span> to the vertical distribution of these gases is investigated in this study and is shown to be significant. The difference in the global <span class="hlt">radiative</span> <span class="hlt">forcing</span> arising from the assumption of a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26937678','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26937678"><span id="translatedtitle">Lamb Wave-Based Acoustic <span class="hlt">Radiation</span> <span class="hlt">Force</span>-Driven Particle Ring Formation Inside a Sessile Droplet.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Destgeer, Ghulam; Ha, Byunghang; Park, Jinsoo; Sung, Hyung Jin</p> <p>2016-04-01</p> <p>We demonstrate an acoustofluidic device using Lamb waves (LWs) to manipulate polystyrene (PS) microparticles suspended in a sessile droplet of water. The LW-based acoustofluidic platform used in this study is advantageous in that the device is actuated over a range of frequencies without changing the device structure or electrode pattern. In <span class="hlt">addition</span>, the device is simple to operate and cheap to fabricate. The LWs, produced on a piezoelectric substrate, attenuate inside the fluid and create acoustic streaming flow (ASF) in the form of a poloidal flow with toroidal vortices. The PS particles experience direct acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> (ARF) in <span class="hlt">addition</span> to being influenced by the ASF, which drive the concentration of particles to form a ring. This phenomenon was previously attributed to the ASF alone, but the present experimental results confirm that the ARF plays an important role in forming the particle ring, which would not be possible in the presence of only the ASF. We used a range of actuation frequencies (45-280 MHz), PS particle diameters (1-10 μm), and droplet volumes (5, 7.5, and 10 μL) to experimentally demonstrate this phenomenon. PMID:26937678</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1184283','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1184283"><span id="translatedtitle">Observational determination of surface <span class="hlt">radiative</span> <span class="hlt">forcing</span> by CO2 from 2000 to 2010</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Feldman, Daniel R.; Collins, William D.; Gero, P. Johnathan; Torn, Margaret S.; Mlawer, Eli J.; Shippert, Timothy R.</p> <p>2015-02-25</p> <p>The climatic impact of CO2 and other greenhouse gases is usually quantified in terms of <span class="hlt">radiative</span> <span class="hlt">forcing</span>1, calculated as the difference between estimates of the Earth’s <span class="hlt">radiation</span> field from pre-industrial and present-day concentrations of these gases. <span class="hlt">Radiative</span> transfer models calculate that the increase in CO2 since 1750 corresponds to a global annual-mean <span class="hlt">radiative</span> <span class="hlt">forcing</span> at the tropopause of 1.82 ± 0.19 W m<sup>-2</sup> (ref. 2). However, despite widespread scientific discussion and modelling of the climate impacts of well-mixed greenhouse gases, there is little direct observational evidence of the <span class="hlt">radiative</span> impact of increasing atmospheric CO2. Here we present observationally based evidence of clear-sky CO2 surface <span class="hlt">radiative</span> <span class="hlt">forcing</span> that is directly attributable to the increase, between 2000 and 2010, of 22 parts per million atmospheric CO2. The time series of this <span class="hlt">forcing</span> at the two locations—the Southern Great Plains and the North Slope of Alaska—are derived from Atmospheric Emitted Radiance Interferometer spectra3 together with ancillary measurements and thoroughly corroborated <span class="hlt">radiative</span> transfer calculations4. The time series both show statistically significant trends of 0.2 W m<sup>-2</sup> per decade (with respective uncertainties of ±0.06 W m<sup>-2</sup> per decade and ±0.07 W m-2 per decade) and have seasonal ranges of 0.1–0.2 W m<sup>-2</sup>. This is approximately ten per cent of the trend in downwelling longwave <span class="hlt">radiation</span>5, 6, 7. These results confirm theoretical predictions of the atmospheric greenhouse effect due to anthropogenic emissions, and provide empirical evidence of how rising CO2 levels, mediated by temporal variations due to photosynthesis and respiration, are affecting the surface energy balance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25731165','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25731165"><span id="translatedtitle">Observational determination of surface <span class="hlt">radiative</span> <span class="hlt">forcing</span> by CO2 from 2000 to 2010.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Feldman, D R; Collins, W D; Gero, P J; Torn, M S; Mlawer, E J; Shippert, T R</p> <p>2015-03-19</p> <p>The climatic impact of CO2 and other greenhouse gases is usually quantified in terms of <span class="hlt">radiative</span> <span class="hlt">forcing</span>, calculated as the difference between estimates of the Earth's <span class="hlt">radiation</span> field from pre-industrial and present-day concentrations of these gases. <span class="hlt">Radiative</span> transfer models calculate that the increase in CO2 since 1750 corresponds to a global annual-mean <span class="hlt">radiative</span> <span class="hlt">forcing</span> at the tropopause of 1.82 ± 0.19 W m(-2) (ref. 2). However, despite widespread scientific discussion and modelling of the climate impacts of well-mixed greenhouse gases, there is little direct observational evidence of the <span class="hlt">radiative</span> impact of increasing atmospheric CO2. Here we present observationally based evidence of clear-sky CO2 surface <span class="hlt">radiative</span> <span class="hlt">forcing</span> that is directly attributable to the increase, between 2000 and 2010, of 22 parts per million atmospheric CO2. The time series of this <span class="hlt">forcing</span> at the two locations-the Southern Great Plains and the North Slope of Alaska-are derived from Atmospheric Emitted Radiance Interferometer spectra together with ancillary measurements and thoroughly corroborated <span class="hlt">radiative</span> transfer calculations. The time series both show statistically significant trends of 0.2 W m(-2) per decade (with respective uncertainties of ±0.06 W m(-2) per decade and ±0.07 W m(-2) per decade) and have seasonal ranges of 0.1-0.2 W m(-2). This is approximately ten per cent of the trend in downwelling longwave <span class="hlt">radiation</span>. These results confirm theoretical predictions of the atmospheric greenhouse effect due to anthropogenic emissions, and provide empirical evidence of how rising CO2 levels, mediated by temporal variations due to photosynthesis and respiration, are affecting the surface energy balance. PMID:25731165</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.B21I..01P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.B21I..01P"><span id="translatedtitle">Hydrological and ecological implications of <span class="hlt">radiative</span> <span class="hlt">forcing</span> by dust in snow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Painter, T.; Bryant, A. C.; Deems, J. S.; Skiles, M.</p> <p>2012-12-01</p> <p>The runoff from the Colorado River supplies water to over 30 million people in seven US states and Mexico. Climate change projections suggest that this runoff will decrease in the next 50 years by 7-20% due to increases in evapotranspiration and decreases in the ratio of snowfall to rain. Such scenarios challenge the sustainability of the freshwater supply to the southwest US. Recent research however has shown that <span class="hlt">radiative</span> <span class="hlt">forcing</span> by dust in snow has been shortening snow cover duration by several weeks due to a 5-7-fold increase in dust loading relative to prior to the European-settlement of the western US in the mid-1800s. In the mountains of the Upper Colorado River, the absolute dust <span class="hlt">radiative</span> <span class="hlt">forcing</span> across the period ranges from 30 to 75 W m-2, in turn shortening snow cover duration by 21 to 51 days. Extended to the scale of the Upper Colorado River Basin, this impact has brought peak normalized runoff at Lee's Ferry, AZ (Lake Powell) more than three weeks earlier and reduced the total annual runoff by an average of ~5%. In this region, earlier snowmelt <span class="hlt">forced</span> by dust <span class="hlt">radiative</span> <span class="hlt">forcing</span> impacts alpine vegetation by increasing synchronicity in phenology across the alpine landscape with increasingly earlier snowmelt. Whereas reduced dust load results in topographically-sensitive melt and loss of snow cover, the more spatially-uniform snowmelt from dust <span class="hlt">radiative</span> <span class="hlt">forcing</span> leads to synchronized growth and flowering across the landscape. Water managers in the Upper Colorado basin now seek detailed real-time knowledge of dust presence, <span class="hlt">radiative</span> <span class="hlt">forcing</span>, and its potential to accelerate snowmelt, as well as understanding its implications for water supply under current conditions and in a changed climate. Likewise, water stakeholder groups, water conservation districts, and state and federal agencies are discussing efforts to restabilize soil surfaces in the dust-emitting regions to mitigate impacts of dust on snowmelt and runoff. However, as these policy</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140011119','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140011119"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">Forcing</span> Due to Major Aerosol Emitting Sectors in China and India</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Streets, David G.; Shindell, Drew Todd; Lu, Zifeng; Faluvegi, Greg</p> <p>2013-01-01</p> <p>Understanding the <span class="hlt">radiative</span> <span class="hlt">forcing</span> caused by anthropogenic aerosol sources is essential for making effective emission control decisions to mitigate climate change. We examined the net direct plus indirect <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">forcings</span> due mainly to the direct and indirect effects of BC. Emissions from these two sectors in China have near-zero net global <span class="hlt">forcings</span>. Coal-fired power plants in both countries exert a negative <span class="hlt">forcing</span> of about -30 mW/ sq. m from production of sulfate. Aerosol <span class="hlt">forcings</span> are largest locally, with direct <span class="hlt">forcings</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980007547','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980007547"><span id="translatedtitle">Infrared <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> and Atmospheric Lifetimes of Trace Species Based on Observations from UARS</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Minschwaner, K.; Carver, R. W.; Briegleb, B. P.</p> <p>1997-01-01</p> <p>Observations from instruments on the Upper Atmosphere Research Satellite (UARS) have been used to constrain calculations of infrared <span class="hlt">radiative</span> <span class="hlt">forcing</span> by CH4, CCl2F2 and N2O, and to determine lifetimes Of CCl2F2 and N2O- <span class="hlt">Radiative</span> <span class="hlt">forcing</span> is calculated as a change in net infrared flux at the tropopause that results from an increase in trace gas amount from pre-industrial (1750) to contemporary (1992) times. Latitudinal and seasonal variations are considered explicitly, using distributions of trace gases and temperature in the stratosphere from UARS measurements and seasonally averaged cloud statistics from the International Satellite Cloud Climatology Project. Top-of-atmosphere fluxes calculated for the contemporary period are in good agreement with satellite measurements from the Earth <span class="hlt">Radiation</span> Budget Experiment. Globally averaged values of the <span class="hlt">radiative</span> <span class="hlt">forcing</span> are 0.536, 0.125, and 0.108 W m-2 for CH4, CCl2F2, and N2O, respectively. The largest <span class="hlt">forcing</span> occurs near subtropical latitudes during summer, predominantly as a result of the combination of cloud-free skies and a high, cold tropopause. Clouds are found to play a significant role in regulating infrared <span class="hlt">forcing</span>, reducing the magnitude of the <span class="hlt">forcing</span> by 30-40% compared to the case of clear skies. The vertical profile of CCl2F2 is important in determining its <span class="hlt">radiative</span> <span class="hlt">forcing</span>; use of a height-independent mixing ratio in the stratosphere leads to an over prediction of the <span class="hlt">forcing</span> by 10%. The impact of stratospheric profiles on <span class="hlt">radiative</span> <span class="hlt">forcing</span> by CH4 and N2O is less than 2%. UARS-based distributions of CCl2F2 and N2O are used also to determine global destruction rates and instantaneous lifetimes of these gases. Rates of photolytic destruction in the stratosphere are calculated using solar ultraviolet irradiances measured on UARS and a line-by-line model of absorption in the oxygen Schumann-Runge bands. Lifetimes are 114 +/- 22 and 118 +/- 25 years for CCl2F2 and N2O, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130009938','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130009938"><span id="translatedtitle"><span class="hlt">Addition</span> of Electrostatic <span class="hlt">Forces</span> to EDEM with Applications to Triboelectrically Charged Particles</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hogue, Michael D.; Calle, Carlos; Curry, David</p> <p>2008-01-01</p> <p>Tribocharging of particles is common in many processes including fine powder handling and mixing, printer toner transport and dust extraction. In a lunar environment with its high vacuum and lack of water, electrostatic <span class="hlt">forces</span> are an important factor to consider when designing and operating equipment. Dust mitigation and management is critical to safe and predictable performance of people and equipment. The extreme nature of lunar conditions makes it difficult and costly to carryout experiments on earth which are necessary to better understand how particles gather and transfer charge between each other and with equipment surfaces. DEM (Discrete Element Modeling) provides an excellent virtual laboratory for studying tribocharging of particles as well as for design of devices for dust mitigation and for other purposes related to handling and processing of lunar regolith. Theoretical and experimental work has been performed pursuant to incorporating screened Coulombic electrostatic <span class="hlt">forces</span> into EDEM Tm, a commercial DEM software package. The DEM software is used to model the trajectories of large numbers of particles for industrial particulate handling and processing applications and can be coupled with other solvers and numerical models to calculate particle interaction with surrounding media and <span class="hlt">force</span> fields. In this paper we will present overview of the theoretical calculations and experimental data and their comparison to the results of the DEM simulations. We will also discuss current plans to revise the DEM software with advanced electrodynamic and mechanical algorithms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AtmEn..39.4609P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AtmEn..39.4609P"><span id="translatedtitle">Large-scale changes in the cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> over the Indian region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Patil, S. D.; Yadav, R. K.</p> <p></p> <p>Based on earth <span class="hlt">radiation</span> budget experiment (ERBE) data, earlier studies have shown that in tropical deep-convective regions there is a near cancellation between shortwave and longwave cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> and El Nino event affects the cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> in the Pacific Ocean. The present study investigates these features over the Indian region (0-30°N, 60-120°E) in the peak monsoon month July, (being a representative month of the southwest monsoon season) using satellite measurements of ERBE and International Satellite Cloud Climatology Project (ISCCP) cloud data during the period 1985-1989. It has been observed from the study that a unique imbalance is seen between shortwave cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> (SWCRF) and longwave cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> (LWCRF). It is found to be prominent when the magnitude of LWCRF is higher than 50 W m -2. Net cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> (NCRF) is highly negative in the Indian region from Arabian sea to Indochina and near zero in the equatorial Indian Ocean. The ratio N, i.e., N=-SWCRF/LWCRF, is showing significantly higher values for all the years, the variation of observed N against SWCRF also shows higher values with SWCRF during average of 1985-1989, 1987 and 1988 because it is more than (N=˜1) that mentioned by Kiehl and Ramanathan (1990, Comparison of cloud <span class="hlt">forcing</span> derived from the earth <span class="hlt">radiation</span> budget experiment with that simulated by NCAR community climate model. Journal of Geophysical Research 95, 11679-11698) suggesting more imbalance between SWCRF and LWCRF and the lowering of the cloud top pressure particularly in 1987. Cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> (CRF) components are undergoing year-to-year variability with maximum magnitude in 1988 and minimum in 1987 similar to rainfall variation over the region, indicating an association between monsoon rainfall activity and CRF. Large-scale reduction occurred in the magnitudes of CRF and cloud physical properties in the Arabian Sea and south Bay of Bengal especially in 1987, and NCEP</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUSM.H34C..04P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUSM.H34C..04P"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">Forcing</span> of Dust in Mountain Snow from MODIS surface reflectance data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Painter, T. H.</p> <p>2009-05-01</p> <p>Here I present an algorithm that retrieves the <span class="hlt">radiative</span> <span class="hlt">forcing</span> by desert dust in mountain snow cover from surface reflectance data from NASA Moderate Resolution Imaging Spectroradiometer (MODIS). Dust emitted from natural and disturbed lands frequently deposits to mountain snow cover through dry and wet deposition, particularly in spring when synoptic scale storms entrain material from recently dried surfaces. Dust decreases snow spectral albedo, primarily in the visible wavelengths where the imaginary parts of the complex refractive indices of dust and ice have the greatest contrast. This surface <span class="hlt">radiative</span> <span class="hlt">forcing</span> accelerates melt and contributes to the snow-albedo feedback. In the Rocky Mountains of Colorado, this has been shown to shorten the duration of snow cover by approximately a month. The algorithm presented here, MODIS Dust <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> in Snow (MOD-DRFS), determines the per pixel <span class="hlt">radiative</span> <span class="hlt">forcing</span> by dust in snow from a coupled <span class="hlt">radiative</span> transfer model that infers the reflectance difference between clean snow spectra and dust- laden snow spectra according to a grain size matching in the near infrared and shortwave infrared wavelengths that are not affected by dust absorption. The spectral residuals are splined to a high spectral resolution and convolved with the at surface spectral irradiance modulated by local topography, and subsequently integrated to the instantaneous surface <span class="hlt">radiative</span> <span class="hlt">forcing</span>. I demonstrate the model with retrievals in the Zagros Mountains, Iran and the San Juan Mountains, Colorado, USA. Preliminary validation of the model with in situ detailed pyranometer measurements in the San Juan Mountains indicates that the model has uncertainties of < 7 W/m2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AtmRe.171...56X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AtmRe.171...56X"><span id="translatedtitle">Aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> in desert and semi-desert regions of northwestern China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xin, Jinyuan; Gong, Chongshui; Wang, Shigong; Wang, Yuesi</p> <p>2016-05-01</p> <p>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. <span class="hlt">Radiation</span> <span class="hlt">forcing</span> was identified by using the Santa Barbara DISORT Atmospheric <span class="hlt">Radiative</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> was confirmed to heat the atmosphere (50-53 W/m2) and cool the surface (- 39 to - 48 W/m2) above the analyzed desert. <span class="hlt">Radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span>. The annual averaged heating rates for aerosols close to the ground (1 km) were approximately 0.80-0.85 K/day.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ACPD...1318809V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ACPD...1318809V"><span id="translatedtitle">A new method for evaluating the impact of vertical distribution on aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> in general circulation models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vuolo, M. R.; Schulz, M.; Balkanski, Y.; Takemura, T.</p> <p>2013-07-01</p> <p>The quantification and understanding of direct aerosol <span class="hlt">forcing</span> is essential in the study of climate. One of the main issues that makes its quantification difficult is the lack of a complete comprehension of the role of the aerosol and clouds vertical distribution. This work aims at reducing the incertitude of aerosol <span class="hlt">forcing</span> due to the vertical superposition of several short-lived atmospheric components, in particular different aerosols species and clouds. We propose a method to quantify the contribution of different parts of the atmospheric column to the <span class="hlt">forcing</span>, and to evaluate model differences by isolating the effect of <span class="hlt">radiative</span> interactions only. Any microphysical or thermo-dynamical interactions between aerosols and clouds are deactivated in the model, to isolate the effects of <span class="hlt">radiative</span> flux coupling. We investigate the contribution of aerosol above, below and in clouds, by using added diagnostics in the aerosol-climate model LMDz. We also compute the difference between the <span class="hlt">forcing</span> of the ensemble of the aerosols and the sum of the <span class="hlt">forcings</span> from individual species, in clear-sky. This difference is found to be moderate on global average (14%) but can reach high values regionally (up to 100%). The non-<span class="hlt">additivity</span> of <span class="hlt">forcing</span> already for clear-sky conditions shows, that in <span class="hlt">addition</span> to represent well the amount of individual aerosol species, it is critical to capture the vertical distribution of all aerosols. Nonlinear effects are even more important when superposing aerosols and clouds. Four <span class="hlt">forcing</span> computations are performed, one where the full aerosol 3-D distribution is used, and then three where aerosols are confined to regions above, inside and below clouds respectively. We find that the <span class="hlt">forcing</span> of aerosols depends crucially on the presence of clouds and on their position relative to that of the aerosol, in particular for black carbon (BC). We observe a strong enhancement of the <span class="hlt">forcing</span> of BC above clouds, attenuation for BC below clouds, and a moderate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.A11M0227N&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.A11M0227N&link_type=ABSTRACT"><span id="translatedtitle">Dependence of the <span class="hlt">radiative</span> <span class="hlt">forcing</span> of the climate system on fossil fuel type</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nunez, L. I.</p> <p>2015-12-01</p> <p>Climate change mitigation strategies are greatly directed towards the reduction of CO2 emissions and other greenhouse gases from fossil fuel combustion to limit warming to 2º C in this century. For example, the Clean Power Plan aims to reduce CO2 emissions from the power sector by 32% of 2005 levels by 2030 by increasing power plant efficiency but also by switching from coal-fired power plants to natural gas-fired power plants. It is important to understand the impact of such fuel switching on climate change. While all fossil fuels emit CO2, they also emit other pollutants with varying effects on climate, health and agriculture. First, The emission of CO2 per joule of energy produced varies significantly between coal, oil and natural gas. Second, the complexity that the co-emitted pollutants add to the perturbations in the climate system necessitates the detangling of <span class="hlt">radiative</span> <span class="hlt">forcing</span> for each type of fossil fuel. The historical (1850-2011) net <span class="hlt">radiative</span> <span class="hlt">forcing</span> of climate as a function of fuel type (coal, oil, natural gas and biofuel) is reconstructed. The results reveal the significant dependence of the CO2 and the non-CO2 <span class="hlt">forcing</span> on fuel type. The CO2 <span class="hlt">forcing</span> per joule of energy is largest for coal. <span class="hlt">Radiative</span> <span class="hlt">forcing</span> from the co-emitted pollutants (black carbon, methane, nitrogen oxides, organic carbon, sulfate aerosols) changes the global mean CO2 <span class="hlt">forcing</span> attributed to coal and oil significantly. For natural gas, the CO2-only <span class="hlt">radiative</span> <span class="hlt">forcing</span> from gas is increased by about 60% when the co-emitted pollutants are included.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013RaPC...84..218K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013RaPC...84..218K"><span id="translatedtitle"><span class="hlt">Radiation</span> processing of thermoplastic starch by blending aromatic <span class="hlt">additives</span>: Effect of blend composition and <span class="hlt">radiation</span> parameters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khandal, Dhriti; Mikus, Pierre-Yves; Dole, Patrice; Coqueret, Xavier</p> <p>2013-03-01</p> <p>This paper reports on the effects of electron beam (EB) irradiation on poly α-1,4-glucose oligomers (maltodextrins) in the presence of water and of various aromatic <span class="hlt">additives</span>, as model blends for gaining a better understanding at a molecular level the modifications occurring in amorphous starch-lignin blends submitted to ionizing irradiation for improving the properties of this type of bio-based thermoplastic material. A series of aromatic compounds, namely p-methoxy benzyl alcohol, benzene dimethanol, cinnamyl alcohol and some related carboxylic acids namely cinnamic acid, coumaric acid, and ferulic acid, was thus studied for assessing the ability of each <span class="hlt">additive</span> to counteract chain scission of the polysaccharide and induce interchain covalent linkages. Gel formation in EB-irradiated blends comprising of maltodextrin was shown to be dependent on three main factors: the type of aromatic <span class="hlt">additive</span>, presence of glycerol, and irradiation dose. The chain scission versus grafting phenomenon as a function of blend composition and dose were studied using Size Exclusion Chromatography by determining the changes in molecular weight distribution (MWD) from Refractive Index (RI) chromatograms and the presence of aromatic grafts onto the maltodextrin chains from UV chromatograms. The occurrence of crosslinking was quantified by gel fraction measurements allowing for ranking the cross-linking efficiency of the <span class="hlt">additives</span>. When applying the method to destructurized starch blends, gel formation was also shown to be strongly affected by the moisture content of the sample submitted to irradiation. The results demonstrate the possibility to tune the reactivity of tailored blend for minimizing chain degradation and control the degree of cross-linking.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RScI...87a6101K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RScI...87a6101K"><span id="translatedtitle">Note: Measurement system for the <span class="hlt">radiative</span> <span class="hlt">forcing</span> of greenhouse gases in a laboratory scale</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kawamura, Yoshiyuki</p> <p>2016-01-01</p> <p>The <span class="hlt">radiative</span> <span class="hlt">forcing</span> of the greenhouse gases has been studied being based on computational simulations or the observation of the real atmosphere meteorologically. In order to know the greenhouse effect more deeply and to study it from various viewpoints, the study on it in a laboratory scale is important. We have developed a direct measurement system for the infrared back <span class="hlt">radiation</span> from the carbon dioxide (CO2) gas. The system configuration is similar with that of the practical earth-atmosphere-space system. Using this system, the back <span class="hlt">radiation</span> from the CO2 gas was directly measured in a laboratory scale, which roughly coincides with meteorologically predicted value.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26827362','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26827362"><span id="translatedtitle">Note: Measurement system for the <span class="hlt">radiative</span> <span class="hlt">forcing</span> of greenhouse gases in a laboratory scale.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kawamura, Yoshiyuki</p> <p>2016-01-01</p> <p>The <span class="hlt">radiative</span> <span class="hlt">forcing</span> of the greenhouse gases has been studied being based on computational simulations or the observation of the real atmosphere meteorologically. In order to know the greenhouse effect more deeply and to study it from various viewpoints, the study on it in a laboratory scale is important. We have developed a direct measurement system for the infrared back <span class="hlt">radiation</span> from the carbon dioxide (CO2) gas. The system configuration is similar with that of the practical earth-atmosphere-space system. Using this system, the back <span class="hlt">radiation</span> from the CO2 gas was directly measured in a laboratory scale, which roughly coincides with meteorologically predicted value. PMID:26827362</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4076688','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4076688"><span id="translatedtitle">Soot superaggregates from flaming wildfires and their direct <span class="hlt">radiative</span> <span class="hlt">forcing</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Chakrabarty, Rajan K.; Beres, Nicholas D.; Moosmüller, Hans; China, Swarup; Mazzoleni, Claudio; Dubey, Manvendra K.; Liu, Li; Mishchenko, Michael I.</p> <p>2014-01-01</p> <p>Wildfires contribute significantly to global soot emissions, yet their aerosol formation mechanisms and resulting particle properties are poorly understood and parameterized in climate models. The conventional view holds that soot is formed via the cluster-dilute aggregation mechanism in wildfires and emitted as aggregates with fractal dimension Df ≈ 1.8 mobility diameter Dm ≤ 1 μm, and aerodynamic diameter Da ≤ 300 nm. Here we report the ubiquitous presence of soot superaggregates (SAs) in the outflow from a major wildfire in India. SAs are porous, low-density aggregates of cluster-dilute aggregates with characteristic Df ≈ 2.6, Dm > 1 μm, and Da ≤ 300 nm that form via the cluster-dense aggregation mechanism. We present <span class="hlt">additional</span> observations of soot SAs in wildfire smoke-laden air masses over Northern California, New Mexico, and Mexico City. We estimate that SAs contribute, per unit optical depth, up to 35% less atmospheric warming than freshly-emitted (Df ≈ 1.8) aggregates, and ≈90% more warming than the volume-equivalent spherical soot particles simulated in climate models. PMID:24981204</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140017420','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140017420"><span id="translatedtitle">Soot Superaggregates from Flaming Wildfires and Their Direct <span class="hlt">Radiative</span> <span class="hlt">Forcing</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chakrabarty, Rajan K.; Beres, Nicholas D.; Moosmuller,Hans; China, Swarup; Mazzoleni, Claudio; Dubey, Manvendra K.; Liu, Li; Mishchenko, Michael I.</p> <p>2014-01-01</p> <p>Wildfires contribute significantly to global soot emissions, yet their aerosol formation mechanisms and resulting particle properties are poorly understood and parameterized in climate models. The conventional view holds that soot is formed via the cluster-dilute aggregation mechanism in wildfires and emitted as aggregates with fractal dimension D(sub f) approximately equals 1.8 mobility diameter D(sub m) (is) less than or equal to 1 micron, and aerodynamic diameter D(sub a) (is) less than or equal to 300 nm. Here we report the ubiquitous presence of soot superaggregates (SAs) in the outflow from a major wildfire in India. SAs are porous, low-density aggregates of cluster-dilute aggregates with characteristic D(sub f) approximately equals 2.6,D(sub m) (is) greater than 1 micron, and D(sub a) is less than or equal to 300 nm that form via the cluster-dense aggregation mechanism.We present <span class="hlt">additional</span> observations of soot SAs in wildfire smoke-laden air masses over Northern California, New Mexico, and Mexico City. We estimate that SAs contribute, per unit optical depth, up to 35% less atmospheric warming than freshly-emitted (D(sub f) approximately equals 1.8) aggregates, and approximately equals 90% more warming than the volume-equivalent spherical soot particles simulated in climate models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013RaPC...90...98G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013RaPC...90...98G"><span id="translatedtitle">Modification of silicone sealant to improve gamma <span class="hlt">radiation</span> resistance, by <span class="hlt">addition</span> of protective agents</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>González-Pérez, Giovanni; Burillo, Guillermina</p> <p>2013-09-01</p> <p>Poly (dimethylsiloxane) (PDMS) sealant (SS) was modified with the <span class="hlt">addition</span> of different protective compounds to conserve its physical-chemical properties during gamma irradiation. 2-Vinyl naphthalene (2-VN), bisphenol-A (BPA) and poly (vinyl carbazole) (PVK) were used to evaluate <span class="hlt">radiation</span> protection through the crosslinking effect of <span class="hlt">radiation</span>. The samples were irradiated with doses from 100 kGy to 500 kGy at room temperature in air, with a 60Co gamma source, and the changes in molecular weight, thermal behavior, elastic properties and infrared spectra (FTIR-ATR) absorbance analysis were determined. The molecular weight of unmodified silicone sealant increases with the absorbed dose because of crosslinking as predominant effect. However, the crosslinking effect was inhibited with the <span class="hlt">addition</span> of protective agent due to the aromatic compounds present. Modified silicone sealant films present better <span class="hlt">radiation</span> resistance than unmodified system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19640035','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19640035"><span id="translatedtitle">The <span class="hlt">forced</span> <span class="hlt">radiation</span> efficiency of finite size flat panels that are excited by incident sound.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Davy, John L</p> <p>2009-08-01</p> <p>The <span class="hlt">radiation</span> efficiency of an infinite flat panel that <span class="hlt">radiates</span> 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 <span class="hlt">radiation</span> efficiency tends to infinity as the angle tends to 90 degrees causes problems with simple theories of sound insulation. Sato calculated numerical values of <span class="hlt">radiation</span> efficiency for a finite size rectangular panel in an infinite baffle whose motion is <span class="hlt">forced</span> 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 <span class="hlt">radiation</span>, rather than its width that is important in determining its <span class="hlt">radiation</span> 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 <span class="hlt">forced</span> <span class="hlt">radiation</span> efficiency of a panel. PMID:19640035</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010SPIE.8203E..1EH','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010SPIE.8203E..1EH"><span id="translatedtitle">Aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> at the top of atmosphere based on satellite remote sensing over China Seas: a preliminary study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hao, Zengzhou; Pan, Delu; Gong, Fang</p> <p>2010-09-01</p> <p><span class="hlt">Radiative</span> <span class="hlt">forcing</span> as an index of climate change can reflect the relative effect of climate factors. To understand climatic implications of aerosols over the China Seas, the aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> at the top of atmosphere (TOA) is computed using three-year collocated Clouds and the Earth's Radiant Energy System (CERES) <span class="hlt">radiation</span> fluxes and Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical thickness data on the platform Terra. The upward <span class="hlt">radiation</span> flux for clear skies is a key for the aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> at the TOA. A linear relationship is found between the solar <span class="hlt">radiation</span> fluxes at the TOA from CERES and the aerosol optical thickness is at 550 nm from MODIS over the China Seas. In a linear regression Eq., the intercept for zero aerosol optical thickness is the <span class="hlt">radiation</span> flux at the TOA for clear skies. Based on the definition of the aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> at TOA and the diurnal correction factor from a simulated <span class="hlt">radiative</span> <span class="hlt">forcing</span> using <span class="hlt">radiation</span> transfer model, the daily averaged aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> at the TOA is estimated and its seasonal variations over the cloud-free China Seas are presented. In total, the aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> over the China Seas is negative. It implies that the aerosol over the China Seas is mainly a cooling effect on climate change, which is opposite to the greenhouse effect. The largest aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> is found in spring, while the smallest is in summer. The aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> over the coastal region is always more than that in the open ocean in four seasons. The method in the study can be used for evaluation of the aerosols impact on global or region climate from satellite measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JaJAP..48gGK03M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JaJAP..48gGK03M"><span id="translatedtitle">Active Path Selection of Fluid Microcapsules in Artificial Blood Vessel by Acoustic <span class="hlt">Radiation</span> <span class="hlt">Force</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masuda, Kohji; Muramatsu, Yusuke; Ueda, Sawami; Nakamoto, Ryusuke; Nakayashiki, Yusuke; Ishihara, Ken</p> <p>2009-07-01</p> <p>Micrometer-sized microcapsules collapse upon exposure to ultrasound. Use of this phenomenon for a drug delivery system (DDS), not only for local delivery of medication but also for gene therapy, should be possible. However, enhancing the efficiency of medication is limited because capsules in suspension diffuse in the human body after injection, since the motion of capsules in blood flow cannot be controlled. To control the behavior of microcapsules, acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> was introduced. We detected local changes in microcapsule density by producing acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> in an artificial blood vessel. Furthermore, we theoretically estimated the conditions required for active path selection of capsules at a bifurcation point in the artificial blood vessel. We observed the difference in capsule density at both in the bifurcation point and in alternative paths downstream of the bifurcation point for different acoustic <span class="hlt">radiation</span> <span class="hlt">forces</span>. Comparing the experimental results with those obtained theoretically, the conditions for active path selection were calculated from the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> and fluid resistance of the capsules. The possibility of controlling capsule flow towards a specific point in a blood vessel was demonstrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.A13K0334G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.A13K0334G"><span id="translatedtitle">Long-wave <span class="hlt">radiative</span> <span class="hlt">forcing</span> due to dust aerosols: observations and climatology comparisons</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gunn, L. N.; Collins, W.</p> <p>2012-12-01</p> <p>Dust aerosols have been identified by the Intergovernmental Panel for Climate Change as a major source of uncertainty in the <span class="hlt">radiative</span> <span class="hlt">forcing</span> of the climate system. Optically thick plumes of dust and pollutants originating from arid regions can be lifted into the middle troposphere and are often transported over synoptic length scales. These events can decrease the upwelling long-wave fluxes at the top of atmosphere (TOA), especially in the mid-infrared portion of the spectrum. Although the long-wave effects of dust are included in model simulations, it is difficult to validate these effects in the absence of satellite-derived global estimates. Using hyper-spectral measurements from NASA's AIRS instrument, we estimate long-wave <span class="hlt">radiative</span> <span class="hlt">forcing</span> due to dust over the oceans for the year 2007. Firstly, we will present the results of these global, year long, <span class="hlt">radiative</span> <span class="hlt">forcing</span> estimates and secondly, we will use these estimates, along with other variables available from A-train instruments (e.g. MODIS aerosol optical depth) to evaluate the long-wave <span class="hlt">radiative</span> <span class="hlt">forcing</span> values from climatological data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4668332','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4668332"><span id="translatedtitle">Intravascular Ultrasound Catheter to Enhance Microbubble-Based Drug Delivery via Acoustic <span class="hlt">Radiation</span> <span class="hlt">Force</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kilroy, Joseph P.; Klibanov, Alexander L.; Wamhoff, Brian R.; Hossack, John A.</p> <p>2015-01-01</p> <p>Previous research has demonstrated that acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> enhances intravascular microbubble adhesion to blood vessels in the presence of flow for molecular-targeted ultrasound imaging and drug delivery. A prototype acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> intravascular ultrasound (ARFIVUS) catheter was designed and fabricated to displace a microbubble contrast agent in flow representative of conditions encountered in the human carotid artery. The prototype ARFIVUS transducer was designed to match the resonance frequency of 1.4- to 2.6-μm-diameter microbubbles modeled by an experimentally verified 1-D microbubble acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> translation model. The transducer element was an elongated Navy Type I (hard) lead zirconate titanate (PZT) ceramic designed to operate at 3 MHz. Fabricated devices operated with center frequencies of 3.3 and 3.6 MHz with −6-dB fractional bandwidths of 55% and 50%, respectively. Microbubble translation velocities as high as 0.86 m/s were measured using a high-speed streak camera when insonating with the ARFIVUS transducer. Finally, the prototype was used to displace microbubbles in a flow phantom while imaging with a commercial 45-MHz imaging IVUS transducer. A sustained increase of 31 dB in average video intensity was measured following insonation with the ARFIVUS, indicating microbubble accumulation resulting from the application of acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>. PMID:23143566</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26042775','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26042775"><span id="translatedtitle">Integration of acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> and optical imaging for blood plasma clot stiffness measurement.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Caroline W; Perez, Matthew J; Helmke, Brian P; Viola, Francesco; Lawrence, Michael B</p> <p>2015-01-01</p> <p>Despite the life-preserving function blood clotting serves in the body, inadequate or excessive blood clot stiffness has been associated with life-threatening diseases such as stroke, hemorrhage, and heart attack. The relationship between blood clot stiffness and vascular diseases underscores the importance of quantifying the magnitude and kinetics of blood's transformation from a fluid to a viscoelastic solid. To measure blood plasma clot stiffness, we have developed a method that uses ultrasound acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> (ARF) to induce micron-scaled displacements (1-500 μm) on microbeads suspended in blood plasma. The displacements were detected by optical microscopy and took place within a micro-liter sized clot region formed within a larger volume (2 mL sample) to minimize container surface effects. Modulation of the ultrasound generated acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> allowed stiffness measurements to be made in blood plasma from before its gel point to the stage where it was a fully developed viscoelastic solid. A 0.5 wt % agarose hydrogel was 9.8-fold stiffer than the plasma (platelet-rich) clot at 1 h post-kaolin stimulus. The acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> microbead method was sensitive to the presence of platelets and strength of coagulation stimulus. Platelet depletion reduced clot stiffness 6.9 fold relative to platelet rich plasma. The sensitivity of acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> based stiffness assessment may allow for studying platelet regulation of both incipient and mature clot mechanical properties. PMID:26042775</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4456080','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4456080"><span id="translatedtitle">Integration of Acoustic <span class="hlt">Radiation</span> <span class="hlt">Force</span> and Optical Imaging for Blood Plasma Clot Stiffness Measurement</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wang, Caroline W.; Perez, Matthew J.; Helmke, Brian P.; Viola, Francesco; Lawrence, Michael B.</p> <p>2015-01-01</p> <p>Despite the life-preserving function blood clotting serves in the body, inadequate or excessive blood clot stiffness has been associated with life-threatening diseases such as stroke, hemorrhage, and heart attack. The relationship between blood clot stiffness and vascular diseases underscores the importance of quantifying the magnitude and kinetics of blood’s transformation from a fluid to a viscoelastic solid. To measure blood plasma clot stiffness, we have developed a method that uses ultrasound acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> (ARF) to induce micron-scaled displacements (1-500 μm) on microbeads suspended in blood plasma. The displacements were detected by optical microscopy and took place within a micro-liter sized clot region formed within a larger volume (2 mL sample) to minimize container surface effects. Modulation of the ultrasound generated acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> allowed stiffness measurements to be made in blood plasma from before its gel point to the stage where it was a fully developed viscoelastic solid. A 0.5 wt % agarose hydrogel was 9.8-fold stiffer than the plasma (platelet-rich) clot at 1 h post-kaolin stimulus. The acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> microbead method was sensitive to the presence of platelets and strength of coagulation stimulus. Platelet depletion reduced clot stiffness 6.9 fold relative to platelet rich plasma. The sensitivity of acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> based stiffness assessment may allow for studying platelet regulation of both incipient and mature clot mechanical properties. PMID:26042775</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19820002193','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19820002193"><span id="translatedtitle">A general method for computing the total solar <span class="hlt">radiation</span> <span class="hlt">force</span> on complex spacecraft structures</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chan, F. K.</p> <p>1981-01-01</p> <p>The method circumvents many of the existing difficulties in computational logic presently encountered in the direct analytical or numerical evaluation of the appropriate surface integral. It may be applied to complex spacecraft structures for computing the total <span class="hlt">force</span> arising from either specular or diffuse reflection or even from non-Lambertian reflection and re-<span class="hlt">radiation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JaJAP..47.4193O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JaJAP..47.4193O"><span id="translatedtitle">Ultrasonic Measurement of Strain Distribution Inside Object Cyclically Compressed by Dual Acoustic <span class="hlt">Radiation</span> <span class="hlt">Force</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Odagiri, Yoshitaka; Hasegawa, Hideyuki; Kanai, Hiroshi</p> <p>2008-05-01</p> <p>One possible way to evaluate acupuncture therapy quantitatively is to measure the change in the elastic property of muscle after application of the therapy. Many studies have been conducted to measure mechanical properties of tissues using ultrasound-induced acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>. To assess mechanical properties, strain must be generated in an object. However, a single <span class="hlt">radiation</span> <span class="hlt">force</span> is not effective because it mainly generates translational motion when the object is much harder than the surrounding medium. In this study, two cyclic <span class="hlt">radiation</span> <span class="hlt">forces</span> are simultaneously applied to a muscle phantom from two opposite horizontal directions so that the object is cyclically compressed in the horizontal direction. By the horizontal compression, the object is expanded vertically based on its incompressibility. The resultant vertical displacement is measured using another ultrasound pulse. Two ultrasonic transducers for actuation were both driven by the sum of two continuous sinusoidal signals at two slightly different frequencies [1 MHz and (1 M + 5) Hz]. The displacement of several micrometers in amplitude, which fluctuated at 5 Hz, was measured by the ultrasonic phased tracking method. Increase in thickness inside the object was observed just when acoustic <span class="hlt">radiation</span> <span class="hlt">forces</span> increased. Such changes in thickness correspond to vertical expansion due to horizontal compression.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012RScI...83a4902J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012RScI...83a4902J"><span id="translatedtitle">A contactless methodology of picking up micro-particles from rigid surfaces by acoustic <span class="hlt">radiation</span> <span class="hlt">force</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jia, Kun; Yang, Keji; Fan, Zongwei; Ju, Bing-Feng</p> <p>2012-01-01</p> <p>Controlled movement and pick up of small object from a rigid surface is a primary challenge in many applications. In this paper, a contactless methodology of picking up micro-particles within deionized water from rigid surfaces by acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> is presented. In order to achieve this, an acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> was generated by 1.75 MHz transducers. A custom built setup facilitates the optimization of the sound field by varying the parameters such as sound source size and source position. The three-dimensional pressure distributions are measured and its relative sound field is also characterized accordingly. The standing wave field has been formed and it is mainly composed of two obliquely incident plane waves and their reflectors. We demonstrated the gripping and positioning of silica beads, SiO2, and aluminum micro-particles of 100 μm to 500 μm in size with this method using acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>. The acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> generated is well controlled, contactless, and in the tens of nano-Newton range which allowed us to manipulate relative big micro objects such as MEMS components as well as moving objects such as living cells. The proposed method provided an alternative form of contactless operating environment with scalable dimensions suitable for the manipulating of small objects. This permits high-throughput processing and reduction in time required for MEMS assembling, cell biomechanics, and biotechnology applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=275870&keyword=production+AND+plant&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=65360745&CFTOKEN=27157419','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=275870&keyword=production+AND+plant&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=65360745&CFTOKEN=27157419"><span id="translatedtitle">Impacts of Human Alteration of the Nitrogen Cycle in the U.S. on <span class="hlt">Radiative</span> <span class="hlt">Forcing</span></span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Nitrogen cycling processes affect <span class="hlt">radiative</span> <span class="hlt">forcing</span> directly through emissions of nitrous oxide (N2O) and indirectly because emissions of nitrogen oxide (NO x ) and ammonia (NH3) affect atmospheric concentrations of methane (CH4), carbon dioxide (CO2), water vapor (H2O), ozone (O...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26811462','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26811462"><span id="translatedtitle">Near-linear response of mean monsoon strength to a broad range of <span class="hlt">radiative</span> <span class="hlt">forcings</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Boos, William R; Storelvmo, Trude</p> <p>2016-02-01</p> <p>Theoretical models have been used to argue that seasonal mean monsoons will shift abruptly and discontinuously from wet to dry stable states as their <span class="hlt">radiative</span> <span class="hlt">forcings</span> pass a critical threshold, sometimes referred to as a "tipping point." Further support for a strongly nonlinear response of monsoons to <span class="hlt">radiative</span> <span class="hlt">forcings</span> is found in the seasonal onset of the South Asian summer monsoon, which is abrupt compared with the annual cycle of insolation. Here it is shown that the seasonal mean strength of monsoons instead exhibits a nearly linear dependence on a wide range of <span class="hlt">radiative</span> <span class="hlt">forcings</span>. First, a previous theory that predicted a discontinuous, threshold response is shown to omit a dominant stabilizing term in the equations of motion; a corrected theory predicts a continuous and nearly linear response of seasonal mean monsoon strength to <span class="hlt">forcings</span>. A comprehensive global climate model is then used to show that the seasonal mean South Asian monsoon exhibits a near-linear dependence on a wide range of isolated greenhouse gas, aerosol, and surface albedo <span class="hlt">forcings</span>. This model reproduces the observed abrupt seasonal onset of the South Asian monsoon but produces a near-linear response of the mean monsoon by changing the duration of the summer circulation and the latitude of that circulation's ascent branch. Thus, neither a physically correct theoretical model nor a comprehensive climate model support the idea that seasonal mean monsoons will undergo abrupt, nonlinear shifts in response to changes in greenhouse gas concentrations, aerosol emissions, or land surface albedo. PMID:26811462</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMGC11C0999D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMGC11C0999D"><span id="translatedtitle">Study of Ocean Response to Periodic and Constant Volcanic <span class="hlt">Radiative</span> <span class="hlt">Forcing</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dogar, M.; Stenchikov, G. L.</p> <p>2013-12-01</p> <p>It is known that volcanic <span class="hlt">radiative</span> impacts could produce long-term perturbations of the ocean heat content. In this study we systematically compare the effect of periodic volcanic <span class="hlt">forcing</span> with an equivalent time-average <span class="hlt">radiative</span> cooling. One could expect that a sporadic strong cooling should initiate more vigorous vertical mixing of the upper ocean layer and therefore cools the ocean more effectively than a uniform <span class="hlt">radiative</span> <span class="hlt">forcing</span>. However, the long-term simulations show that on average the ocean heat content responses to periodic and constant <span class="hlt">forcings</span> are almost identical. To better understand this controversy we conducted two sets of parallel simulations, the first one with uniform volcanic <span class="hlt">forcing</span> and the second one with periodic volcanic <span class="hlt">forcing</span> with 10 and 50 years repeating cycle using Geophysical Fluid Dynamics Laboratory Coupled Model CM2.1. We found that average perturbations of surface temperature, precipitation, ocean heat content, and sea level rise in both sets of simulations are similar but responses of Atlantic Meridional Overturning Circulation are significantly different, which explains the differences in the relaxation processes. These findings could be important for ocean initialization in long-tern climate studies and for geoengineering applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A44G..03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A44G..03S"><span id="translatedtitle">Importance of tropospheric volcanic aerosol for indirect <span class="hlt">radiative</span> <span class="hlt">forcing</span> of climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmidt, A.; Carslaw, K. S.; Mann, G.; Rap, A.; Pringle, K. J.; Spracklen, D. V.; Wilson, M.; Forster, P.</p> <p>2013-12-01</p> <p>Observations and models have shown that continuously degassing volcanoes have a potentially large effect on the natural background aerosol loading and the <span class="hlt">radiative</span> state of the atmosphere. We use a global aerosol microphysics model to quantify the impact of these volcanic emissions on the cloud albedo <span class="hlt">radiative</span> <span class="hlt">forcing</span> under pre-industrial (PI) and present-day (PD) conditions. We find that volcanic degassing increases global annual mean cloud droplet number concentrations by 40% under PI conditions, but by only 10% under PD conditions. Consequently, volcanic degassing causes a global annual mean cloud albedo effect of -1.06 W m-2 in the PI era but only -0.56 W m-2 in the PD era. This non-equal effect is explained partly by the lower background aerosol concentrations in the PI era, but also because more aerosol particles are produced per unit of volcanic sulphur emission in the PI atmosphere. The higher sensitivity of the PI atmosphere to volcanic emissions has an important consequence for the anthropogenic cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> because the large uncertainty in volcanic emissions translates into an uncertainty in the PI baseline cloud <span class="hlt">radiative</span> state. Assuming a -50/+100% uncertainty range in the volcanic sulphur flux, we estimate the annual mean anthropogenic cloud albedo <span class="hlt">forcing</span> to lie between -1.16 W m-2 and -0.86 W m-2. Therefore, the volcanically induced uncertainty in the PI baseline cloud <span class="hlt">radiative</span> state substantially adds to the already large uncertainty in the magnitude of the indirect <span class="hlt">radiative</span> <span class="hlt">forcing</span> of climate. Effect of uncertain volcanic sulphur emissions on the annual global mean cloud albedo effect and anthropogenic cloud albedo <span class="hlt">forcing</span>. The grey and blue bars show the magnitude and the uncertainty range for the volcanic cloud albedo effect for present-day (PD) and pre-industrial (PI), respectively. In the central panel, the top red bar shows the magnitude of the anthropogenic cloud albedo <span class="hlt">forcing</span> as estimated by IPCC based on a range of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1685d0007L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1685d0007L"><span id="translatedtitle">Effect of particle-particle interactions on the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> in an ultrasonic standing wave</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lipkens, Bart; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.</p> <p>2015-10-01</p> <p>Ultrasonic standing waves are widely used for separation applications. In MEMS applications, a half wavelength standing wave field is generated perpendicular to a laminar flow. The acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> exerted on the particle drives the particle to the center of the MEMS channel, where concentrated particles are harvested. In macro-scale applications, the ultrasonic standing wave spans multiple wavelengths. Examples of such applications are oil/water emulsion splitting [1], and blood/lipid separation [2]. In macro-scale applications, particles are typically trapped in the standing wave, resulting in clumping or coalescence of particles/droplets. Subsequent gravitational settling results in separation of the secondary phase. An often used expression for the <span class="hlt">radiation</span> <span class="hlt">force</span> on a particle is that derived by Gorkov [3]. The assumptions are that the particle size is small relative to the wavelength, and therefore, only monopole and dipole scattering contributions are used to calculate the <span class="hlt">radiation</span> <span class="hlt">force</span>. This framework seems satisfactory for MEMS scale applications where each particle is treated separately by the standing wave, and concentrations are typically low. In macro-scale applications, particle concentration is high, and particle clumping or droplet coalescence results in particle sizes not necessarily small relative to the wavelength. Ilinskii et al. developed a framework for calculation of the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> valid for any size particle [4]. However, this model does not take into account particle to particle effects, which can become important as particle concentration increases. It is known that an acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on a particle or a droplet is determined by the local field. An acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> expression is developed that includes the effect of particle to particle interaction. The case of two neighboring particles is considered. The approach is based on sound scattering by the particles. The acoustic field at the location of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22492631','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22492631"><span id="translatedtitle">Effect of particle-particle interactions on the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> in an ultrasonic standing wave</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lipkens, Bart; Ilinskii, Yurii A. Zabolotskaya, Evgenia A.</p> <p>2015-10-28</p> <p>Ultrasonic standing waves are widely used for separation applications. In MEMS applications, a half wavelength standing wave field is generated perpendicular to a laminar flow. The acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> exerted on the particle drives the particle to the center of the MEMS channel, where concentrated particles are harvested. In macro-scale applications, the ultrasonic standing wave spans multiple wavelengths. Examples of such applications are oil/water emulsion splitting [1], and blood/lipid separation [2]. In macro-scale applications, particles are typically trapped in the standing wave, resulting in clumping or coalescence of particles/droplets. Subsequent gravitational settling results in separation of the secondary phase. An often used expression for the <span class="hlt">radiation</span> <span class="hlt">force</span> on a particle is that derived by Gorkov [3]. The assumptions are that the particle size is small relative to the wavelength, and therefore, only monopole and dipole scattering contributions are used to calculate the <span class="hlt">radiation</span> <span class="hlt">force</span>. This framework seems satisfactory for MEMS scale applications where each particle is treated separately by the standing wave, and concentrations are typically low. In macro-scale applications, particle concentration is high, and particle clumping or droplet coalescence results in particle sizes not necessarily small relative to the wavelength. Ilinskii et al. developed a framework for calculation of the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> valid for any size particle [4]. However, this model does not take into account particle to particle effects, which can become important as particle concentration increases. It is known that an acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on a particle or a droplet is determined by the local field. An acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> expression is developed that includes the effect of particle to particle interaction. The case of two neighboring particles is considered. The approach is based on sound scattering by the particles. The acoustic field at the location of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SPIE.9876E..2NB&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016SPIE.9876E..2NB&link_type=ABSTRACT"><span id="translatedtitle">Evapo-transpiration, role of aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span>: a study over a dense canopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bhanage, VInayak; Latha, R.; Murthy, B. S.</p> <p>2016-05-01</p> <p>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 <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> (ARF) is calculated by using the MERRA data sets of `clean-clear <span class="hlt">radiation</span>' and `clear-<span class="hlt">radiation</span>' at surface over the study area. Maximum aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C32A..05K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C32A..05K"><span id="translatedtitle">Snow surface temperature, <span class="hlt">radiative</span> <span class="hlt">forcing</span> and snow depth as determinants of snow density</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kirchner, P. B.; Painter, T. H.; Skiles, M.; Deems, J. S.</p> <p>2014-12-01</p> <p>Watershed scale observations of snow water equivalence (SWE) are becoming increasingly important globally as the quantity and timing of snowmelt has become less predictable. In the Colorado River watershed, where dust deposition can hasten snowmelt by several weeks, the need for these observations is critical. While advances in measuring snow depth and albedo from the NASA Airborne Snow Observatory have greatly improved our ability to constrain snow depth and <span class="hlt">radiative</span> <span class="hlt">forcing</span>, we have yet to develop a method for remotely observing snow density, which is required for calculating SWE. We evaluate measured and modeled variables of snow- infrared surface temperature, <span class="hlt">radiative</span> <span class="hlt">forcing</span> and snow depth as predictors of snow density. We use 10 seasons of in situ measured snow surface temperature, cumulative modeled dust in snow <span class="hlt">radiative</span> <span class="hlt">forcing</span>, snow depth and manually measured snow density from locations in the Rocky Mountains of southwestern Colorado. We also use measured snow depth and SWE from the 2013 and 2014 water years, from 23-35 locations stratified by modeled downwelling short wave <span class="hlt">radiation</span>, and evaluate them as predictors of snow density. Our analysis shows that daily mean snow surface temperature (R2 0.61, p = <0.001) and cumulative <span class="hlt">radiative</span> <span class="hlt">forcing</span> (R2 0.54, p = <0.001) individually have significant coefficients of determination whereas snow depth alone was not significant. Multiple regression with all three variables (R2 0.84, p = <0.001) was the best predictor of density. Furthermore, when snowpack conditions were isothermal at 0° C, the diurnal coefficient of variation, of measured hourly surface temperature, exhibited consistently high variance. In 2013 we found significant correlations between spatially distributed measurements of snow density (R2 0.33, p = <0.001) and modeled downwelling short wave <span class="hlt">radiation</span>. However, in 2014 the correlation was very low, supporting our hypothesis that seasonal differences in dust driven <span class="hlt">radiative</span> <span class="hlt">forcing</span> are also</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ThApC.121..445L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ThApC.121..445L"><span id="translatedtitle">Past and future direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> of nitrate aerosol in East Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Jiandong; Wang, Wei-Chyung; Liao, Hong; Chang, Wenyuan</p> <p>2015-08-01</p> <p>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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> (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 <span class="hlt">forcing</span> 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 <span class="hlt">addition</span>, 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A53H3312H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A53H3312H"><span id="translatedtitle">An Energetic Perspective on Aerosol <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> and Interactions with Atmospheric Wave Activity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hosseinpour, F.; Wilcox, E. M.; Colarco, P. R.</p> <p>2014-12-01</p> <p>Aerosols have the capability to alter regional-scale atmospheric circulations. A better understanding of the contribution of aerosols to multi-scale atmospheric phenomena and their transient changes is crucial for efforts to evaluate climate predictions using next generation climate models. In this study we address the following questions: (1) Is there a mechanistic relationship between variability of oceanic dust aerosol <span class="hlt">forcing</span> and transient changes in the African easterly jet- African easterly wave (AEJ-AEW) system? (2) What are the long-term impacts of possible aerosol-wave interactions on climate dynamics of eastern tropical Atlantic Ocean and western African monsoon (WAM) region during boreal summer seasons? Our hypothesis is that aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> may act as <span class="hlt">additional</span> energy source to fuel the development of African easterly waves on the northern and southern sides of the AEJ. Evidence in support of this hypothesis is presented based on analysis of an ensemble of NASA satellite data sets, including aerosol optical thickness (AOT) observations from the Moderate Resolution Imaging Spectro-radiometer (MODIS) and the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS), as well as an atmospheric reanalysis from the Modern-Era Retrospective Analysis for Research and Applications (MERRA) and a simulation of global aerosol distributions made with the Goddard Earth Observing System Model version 5 (GEOS-5) Earth system model with meteorology constrained by MERRA and an assimilation of MODIS AOT (MERRAero). We propose that the impacts of Saharan aerosols on the regional climate dynamics occur through contributions to the eddy energy of waves with 2—7-day and 7—11-day variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20070031188&hterms=central+asia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dcentral%2Basia','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20070031188&hterms=central+asia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dcentral%2Basia"><span id="translatedtitle">Atmospheric Teleconnection over Eurasia Induced by Aerosol <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> during Boreal Spring</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kim, Maeng-Ki; Lau, William K. M.; Chin, Mian; Kim, Kyu-Myong; Sud, Y. C.; Walker, Greg K.</p> <p>2006-01-01</p> <p>The direct effects of aerosols on global and regional climate during boreal spring are investigated based on numerical simulations with the NASA Global Modeling and Assimilation Office finite-volume general circulation model (fvGCM) with Microphyics of Clouds with the Relaxed Arakawa Schubert Scheme (McRAS), using aerosol <span class="hlt">forcing</span> functions derived from the Goddard Ozone Chemistry Aerosol <span class="hlt">Radiation</span> and Transport model (GOCART). The authors find that anomalous atmospheric heat sources induced by absorbing aerosols (dust and black carbon) excite 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, that is, South Asia, East Asia, and northern and western Africa. Significant atmospheric heating is found in regions with large loading of dust (over northern Africa and the Middle East) and black carbon (over Southeast 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 concentrations are low. Analyses of circulation anomalies show that the dipole anomaly is a part of an atmospheric teleconnection pattern 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 associated with the regional circulations. The surface temperature signature associated with the aerosol-induced teleconnection bears striking resemblance to the spatial pattern of observed long-term trend in surface temperature over Eurasia. <span class="hlt">Additionally</span>, the boreal spring wave train pattern is similar to that reported by Fukutomi et al. associated with the boreal summer</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.A51C0068P&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AGUFM.A51C0068P&link_type=ABSTRACT"><span id="translatedtitle">Ozone <span class="hlt">Radiative</span> Feedback in Global Warming Simulations with CO2 and non-CO2 <span class="hlt">Forcings</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ponater, M.; Rieger, V.; Dietmüller, S.</p> <p>2015-12-01</p> <p>It has been found that ozone <span class="hlt">radiative</span> feedback acts to reduce the climate sensitivity in global warming simulations including interactive atmospheric chemistry, if the <span class="hlt">radiative</span> <span class="hlt">forcing</span> origins from CO2 increase. The effect can be traced to a negative feedback from stratospheric ozone changes and it is amplified by a reduced positive feedback from stratospheric water vapor.These findings cannot be simply transferred to simulations in which the warming is driven by a non-CO2 <span class="hlt">radiative</span> <span class="hlt">forcing</span>. Using a perturbation of surface NOx and CO emissions as an example, we demonstrate that a tropospheric ozone feedback may have significant impacts on physical feedbacks. These interactions can act to an extent that the effect of a negative ozone feedback can be reversed by changes in other feedbacks, thus increasing the climate sensitivity instead of reducing it. We also address some conceptual issues showing up as chemical feedbacks are added to set of physical feedbacks in simulation with interactive chemistry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AcAau..84..206K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AcAau..84..206K"><span id="translatedtitle">Effect of a drag <span class="hlt">force</span> due to absorption of solar <span class="hlt">radiation</span> on solar sail orbital dynamics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kezerashvili, Roman Ya.; Vázquez-Poritz, Justin F.</p> <p>2013-03-01</p> <p>While solar electromagnetic <span class="hlt">radiation</span> can be used to propel a solar sail, it is shown that the Poynting-Robertson effect related to the absorbed portion of the <span class="hlt">radiation</span> leads to a drag <span class="hlt">force</span> in the transversal direction. The Poynting-Robertson effect is considered for escape trajectories, Heliocentric bound orbits and non-Keplerian bound orbits. For escape trajectories, this drag <span class="hlt">force</span> diminishes the cruising velocity, which has a cumulative effect on the Heliocentric distance. For Heliocentric and non-Keplerian bound orbits, the Poynting-Robertson effect decreases its orbital speed, thereby causing it to slowly spiral towards the Sun. Since the Poynting-Robertson effect is due to the absorbed portion of the electromagnetic <span class="hlt">radiation</span>, degradation of a solar sail implies that this effect becomes enhanced during a mission.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ACPD...1523931T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ACPD...1523931T"><span id="translatedtitle">Sensitivity of modelled sulfate <span class="hlt">radiative</span> <span class="hlt">forcing</span> to DMS concentration and air-sea flux formulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tesdal, J.-E.; Christian, J. R.; Monahan, A. H.; von Salzen, K.</p> <p>2015-09-01</p> <p>In this study, we use an atmospheric general circulation model with explicit aerosol chemistry (CanAM4.1) and several climatologies of surface ocean DMS concentration to assess uncertainties about the climate impact of ocean DMS efflux. Despite substantial variation in the spatial pattern and seasonal evolution of simulated DMS fluxes, the global mean <span class="hlt">radiative</span> <span class="hlt">forcing</span> is approximately linearly proportional to the global mean surface flux of DMS; the spatial and temporal distribution of ocean DMS efflux has only a minor effect on the global <span class="hlt">radiation</span> balance. The effect of the spatial structure, however, generates statistically significant changes in the global mean concentrations of some aerosol species. The effect of seasonality on net <span class="hlt">radiative</span> <span class="hlt">forcing</span> is larger than that of spatial distribution, and is significant at global scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090032051','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090032051"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">Forcing</span> and Temperature Response to Changes in Urban Albedos and Associated CO2 Offsets</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Menon, Surabi; Akbari, Hashem; Mahanama, Sarith; Sednev, Igor; Levinson, Ronnen</p> <p>2009-01-01</p> <p>The two main <span class="hlt">forcings</span> that can counteract to some extent the positive <span class="hlt">forcings</span> from greenhouse gases from pre-industrial times to present-day are the aerosol and related aerosol-cloud <span class="hlt">forcings</span>, and the <span class="hlt">radiative</span> response to changes in surface albedo. Here, we quantify the change in <span class="hlt">radiative</span> <span class="hlt">forcing</span> and surface temperature that may be obtained by increasing the albedos of roofs and pavements in urban areas in temperate and tropical regions of the globe. Using the catchment land surface model (the land model coupled to the GEOS-5 Atmospheric General Circulation Model), we quantify the response of the total outgoing (outgoing shortwave+longwave) <span class="hlt">radiation</span> to urban albedo changes. Globally, the total outgoing <span class="hlt">radiation</span> increased by 0.5 W/square m and temperature decreased by -0.008 K for an average 0.003 increase in albedo. For the U.S. the total outgoing total <span class="hlt">radiation</span> increased by 2.3 W/square meter, and temperature decreased by approximately 0.03 K for an average 0.01 increase in albedo. These values are for the boreal summer (Tune-July-August). Based on these <span class="hlt">forcings</span>, the expected emitted CO2 offset for a plausible 0.25 and 0.15 increase in albedos of roofs and pavements, respectively, for all global urban areas, was found to be approximately 57 Gt CO2 . A more meaningful evaluation of the impacts of urban albedo increases on climate and the expected CO2 offsets would require simulations which better characterizes urban surfaces and represents the full annual cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4889346','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4889346"><span id="translatedtitle">Challenges in constraining anthropogenic aerosol effects on cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> using present-day spatiotemporal variability</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>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</p> <p>2016-01-01</p> <p>A large number of processes are involved in the chain from emissions of aerosol precursor gases and primary particles to impacts on cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span>. Those processes are manifest in a number of relationships that can be expressed as factors dlnX/dlnY driving aerosol effects on cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span>. 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span>. PMID:26921324</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011AtmEn..45.6576H&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011AtmEn..45.6576H&link_type=ABSTRACT"><span id="translatedtitle">Simulation of aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> with RAMS-CMAQ in East Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Han, Xiao; Zhang, Meigen; Han, Zhiwei; Xin, Jinyuan; Liu, Xiaohong</p> <p>2011-11-01</p> <p>The air quality modeling system RAMS-CMAQ is developed to assess aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> by linking simulated meteorological parameters and aerosol mass concentration with the aerosol optical properties/<span class="hlt">radiative</span> transfer module in this study. The module is capable of accounting for important factors that affect aerosol optical properties and <span class="hlt">radiative</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> patterns generally followed the AOD patterns. The strongest <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011AGUFM.A34A..06Z&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011AGUFM.A34A..06Z&link_type=ABSTRACT"><span id="translatedtitle">Simulation of aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> with RAMS-CMAQ in East Asia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, M.; Han, X.; Liu, X.</p> <p>2011-12-01</p> <p>The air quality modeling system RAMS-CMAQ is developed to assess aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> by linking simulated meteorological parameters and aerosol mass concentration with the aerosol optical properties/<span class="hlt">radiative</span> transfer module in this study. The module is capable of accounting for important factors that affect aerosol optical properties and <span class="hlt">radiative</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> patterns generally followed the AOD patterns. The strongest <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JGRD..118.9511P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JGRD..118.9511P"><span id="translatedtitle">Imaging spectroscopy of albedo and <span class="hlt">radiative</span> <span class="hlt">forcing</span> by light-absorbing impurities in mountain snow</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Painter, Thomas H.; Seidel, Felix C.; Bryant, Ann C.; McKenzie Skiles, S.; Rittger, Karl</p> <p>2013-09-01</p> <p>Recent studies show that deposition of dust and black carbon to snow and ice accelerates snowmelt and perturbs regional climate and hydrologic cycles. <span class="hlt">Radiative</span> <span class="hlt">forcing</span> by aerosols is often neglected in climate and hydrological models in part due to scarcity of observations. Here we describe and validate an algorithm suite (Imaging Spectrometer-Snow Albedo and <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> (IS-SnARF)) that provides quantitative retrievals of snow grain size, snow albedo, and <span class="hlt">radiative</span> <span class="hlt">forcing</span> by light-absorbing impurities in snow and ice (LAISI) from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data collected on 15 June 2011 in the Senator Beck Basin Study Area (SBBSA), SW Colorado, USA. <span class="hlt">Radiative</span> <span class="hlt">forcing</span> by LAISI is retrieved by the integral of the convolution of spectral irradiance with spectral differences between the spectral albedo (scaled from the observed hemispherical-directional reflectance factor (HDRF)) and modeled clean snow spectral albedo. The modeled surface irradiance at time of acquisition at test sites was 1052 W m-2 compared to 1048 W m-2 measured with the field spectroradiometer measurements, a relative difference of 0.4%. HDRF retrievals at snow and bare soil sites had mean errors relative to in situ measurements of -0.4 ± 0.1% reflectance averaged across the spectrum and root-mean-square errors of 1.5 ± 0.1%. Comparisons of snow albedo and <span class="hlt">radiative</span> <span class="hlt">forcing</span> retrievals from AVIRIS with in situ measurements in SBBSA showed errors of 0.001-0.004 and 2.1 ± 5.1 W m-2, respectively. A counterintuitive result was that, in the presence of light absorbing impurities, near-surface snow grain size increased with elevation, whereas we generally expect that at lower elevation the grain size would be larger.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26921324','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26921324"><span id="translatedtitle">Challenges in constraining anthropogenic aerosol effects on cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> using present-day spatiotemporal variability.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>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</p> <p>2016-05-24</p> <p>A large number of processes are involved in the chain from emissions of aerosol precursor gases and primary particles to impacts on cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span>. Those processes are manifest in a number of relationships that can be expressed as factors dlnX/dlnY driving aerosol effects on cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span>. 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span>. PMID:26921324</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/983488','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/983488"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">forcing</span> and temperature response to changes in urban albedos and associated CO2 offsets</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Menon, Surabi; Akbari, Hashem; Mahanama, Sarith; Sednev, Igor; Levinson, Ronnen</p> <p>2010-02-12</p> <p>The two main <span class="hlt">forcings</span> that can counteract to some extent the positive <span class="hlt">forcings</span> from greenhouse gases from pre-industrial times to present-day are the aerosol and related aerosol-cloud <span class="hlt">forcings</span>, and the <span class="hlt">radiative</span> response to changes in surface albedo. Here, we quantify the change in <span class="hlt">radiative</span> <span class="hlt">forcing</span> and land surface temperature that may be obtained by increasing the albedos of roofs and pavements in urban areas in temperate and tropical regions of the globe by 0.1. Using the catchment land surface model (the land model coupled to the GEOS-5 Atmospheric General Circulation Model), we quantify the change in the total outgoing (outgoing shortwave+longwave) <span class="hlt">radiation</span> and land surface temperature to a 0.1 increase in urban albedos for all global land areas. The global average increase in the total outgoing <span class="hlt">radiation</span> was 0.5 Wm{sup -2}, and temperature decreased by {approx}0.008 K for an average 0.003 increase in surface albedo. These averages represent all global land areas where data were available from the land surface model used and are for the boreal summer (June-July-August). For the continental U.S. the total outgoing <span class="hlt">radiation</span> increased by 2.3 Wm{sup -2}, and land surface temperature decreased by {approx}0.03 K for an average 0.01 increase in surface albedo. Based on these <span class="hlt">forcings</span>, the expected emitted CO{sub 2} offset for a plausible 0.25 and 0.15 increase in albedos of roofs and pavements, respectively, for all global urban areas, was found to be {approx} 57 Gt CO{sub 2}. A more meaningful evaluation of the impacts of urban albedo increases on global climate and the expected CO{sub 2} offsets would require simulations which better characterizes urban surfaces and represents the full annual cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22493004','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22493004"><span id="translatedtitle">Acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on a rigid elliptical cylinder in plane (quasi)standing waves</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mitri, F. G.</p> <p>2015-12-07</p> <p>The acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on a 2D elliptical (non-circular) cylinder centered on the axis of wave propagation of plane quasi-standing and standing waves is derived, based on the partial-wave series expansion (PWSE) method in cylindrical coordinates. A non-dimensional acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> function, which is the <span class="hlt">radiation</span> <span class="hlt">force</span> per unit length, per characteristic energy density and per unit cross-sectional surface of the ellipse, is defined in terms of the scattering coefficients that are determined by applying the Neumann boundary condition for an immovable surface. A system of linear equations involving a single numerical integration procedure is solved by matrix inversion. Numerical simulations showing the transition from the quasi-standing to the (equi-amplitude) standing wave behaviour are performed with particular emphasis on the aspect ratio a/b, where a and b are the ellipse semi-axes, as well as the dimensionless size parameter kb (where k is the wavenumber), without the restriction to a particular range of frequencies. It is found that at high kb values > 1, the <span class="hlt">radiation</span> <span class="hlt">force</span> per length with broadside incidence is larger, whereas the opposite situation occurs in the long-wavelength limit (i.e., kb < 1). The results are particularly relevant in acoustic levitation of elliptical cylinders, the acoustic stabilization of liquid columns in a host medium, acousto-fluidics devices, and other particle dynamics applications to name a few. Moreover, the formalism presented here may be effectively applied to compute the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on other 2D surfaces of arbitrary shape such as super-ellipses, Chebyshev cylindrical particles, or other non-circular geometries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/538437','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/538437"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">forcing</span> calculations for CH{sub 3}Cl and CH{sub 3}Br</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Grossman, A.S.; Grant, K.E.; Blass, W.E.; Wuebbles, D.J.</p> <p>1997-06-01</p> <p>Methyl chloride, CH{sub 3}Cl, and methyl bromide, CH{sub 3}Br, are particularly important in the global atmosphere as major natural sources of chlorine and bromine to the stratosphere. The production of these gases is dominated by natural sources, but smaller, important anthropogenic sources, such as agricultural fumigation and/or biomass burning, also exist. As absorbers of infrared <span class="hlt">radiation</span> these gases are of interest for their potential effect on the tropospheric energy balance as well as for chemical interactions. In this study we estimate the <span class="hlt">radiative</span> <span class="hlt">forcing</span> and Global Warming Potentials (GWPs) of CH{sub 3}Cl and CH{sub 3}Br. Our calculations use an infrared <span class="hlt">radiative</span> transfer model based on the correlated k-distribution algorithm for band absorption. <span class="hlt">Radiative</span> <span class="hlt">forcing</span> values of 0.0047W/m{sup 2} per part per billion by volume (ppbv) for CH{sub 3}Cl in the troposphere and 0.0049W/m{sup 2} per ppbv for CH{sub 3}Br in the troposphere were obtained. On a per molecule basis the <span class="hlt">radiative</span> <span class="hlt">forcing</span> values are about 2{percent} of the <span class="hlt">forcing</span> of CFC-11 and about 270 times the <span class="hlt">forcing</span> of CO{sub 2}. GWPs for these gases are about 8 for CH{sub 3}Cl and about 4 for CH{sub 3}Br (100 year time integration, CO{sub 2}=1). These results indicate that while CH{sub 3}Cl and CH{sub 3}Br have direct GWPs similar to that of CH{sub 4}, the current emission rates are too low to contribute meaningfully to atmospheric greenhouse heating effects.{copyright} 1997 American Geophysical Union</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1031413','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1031413"><span id="translatedtitle">Simulation of aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> with RAMS-CMAQ in East Asia</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Han, Xiao; Zhang, Meigen; Han, Zhiewi; Xin, Jin-Yuan; Liu, Xiaohong</p> <p>2011-11-14</p> <p>The air quality modeling system RAMS-CMAQ is developed to assess aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> by linking simulated meteorological parameters and aerosol mass concentration with the aerosol optical properties/<span class="hlt">radiative</span> transfer module in this study. The module is capable of accounting for important factors that affect aerosol optical properties and <span class="hlt">radiative</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> patterns generally followed the AOD patterns. The strongest <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26726146','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26726146"><span id="translatedtitle">Acoustic backscattering and <span class="hlt">radiation</span> <span class="hlt">force</span> on a rigid elliptical cylinder in plane progressive waves.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mitri, F G</p> <p>2016-03-01</p> <p>This work proposes a formal analytical theory using the partial-wave series expansion (PWSE) method in cylindrical coordinates, to calculate the acoustic backscattering form function as well as the <span class="hlt">radiation</span> <span class="hlt">force</span>-per-length on an infinitely long elliptical (non-circular) cylinder in plane progressive waves. The major (or minor) semi-axis of the ellipse coincides with the direction of the incident waves. The scattering coefficients for the rigid elliptical cylinder are determined by imposing the Neumann boundary condition for an immovable surface and solving a resulting system of linear equations by matrix inversion. The present method, which utilizes standard cylindrical (Bessel and Hankel) wave functions, presents an advantage over the solution for the scattering that is ordinarily expressed in a basis of elliptical Mathieu functions (which are generally non-orthogonal). Furthermore, an integral equation showing the direct connection of the <span class="hlt">radiation</span> <span class="hlt">force</span> function with the square of the scattering form function in the far-field from the scatterer (applicable for plane waves only), is noted and discussed. An important application of this integral equation is the adequate evaluation of the <span class="hlt">radiation</span> <span class="hlt">force</span> function from a bistatic measurement (i.e., in the polar plane) of the far-field scattering from any 2D object of arbitrary shape. Numerical predictions are evaluated for the acoustic backscattering form function and the <span class="hlt">radiation</span> <span class="hlt">force</span> function, which is the <span class="hlt">radiation</span> <span class="hlt">force</span> per unit length, per characteristic energy density, and per unit cross-sectional surface of the ellipse, with particular emphasis on the aspect ratio a/b, where a and b are the semi-axes, as well as the dimensionless size parameter kb, without the restriction to a particular range of frequencies. The results are particularly relevant in acoustic levitation, acousto-fluidics and particle dynamics applications. PMID:26726146</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JAP...118u4903M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JAP...118u4903M&link_type=ABSTRACT"><span id="translatedtitle">Acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on a rigid elliptical cylinder in plane (quasi)standing waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mitri, F. G.</p> <p>2015-12-01</p> <p>The acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on a 2D elliptical (non-circular) cylinder centered on the axis of wave propagation of plane quasi-standing and standing waves is derived, based on the partial-wave series expansion (PWSE) method in cylindrical coordinates. A non-dimensional acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> function, which is the <span class="hlt">radiation</span> <span class="hlt">force</span> per unit length, per characteristic energy density and per unit cross-sectional surface of the ellipse, is defined in terms of the scattering coefficients that are determined by applying the Neumann boundary condition for an immovable surface. A system of linear equations involving a single numerical integration procedure is solved by matrix inversion. Numerical simulations showing the transition from the quasi-standing to the (equi-amplitude) standing wave behaviour are performed with particular emphasis on the aspect ratio a/b, where a and b are the ellipse semi-axes, as well as the dimensionless size parameter kb (where k is the wavenumber), without the restriction to a particular range of frequencies. It is found that at high kb values > 1, the <span class="hlt">radiation</span> <span class="hlt">force</span> per length with broadside incidence is larger, whereas the opposite situation occurs in the long-wavelength limit (i.e., kb < 1). The results are particularly relevant in acoustic levitation of elliptical cylinders, the acoustic stabilization of liquid columns in a host medium, acousto-fluidics devices, and other particle dynamics applications to name a few. Moreover, the formalism presented here may be effectively applied to compute the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on other 2D surfaces of arbitrary shape such as super-ellipses, Chebyshev cylindrical particles, or other non-circular geometries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ACP....12.7321S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ACP....12.7321S"><span id="translatedtitle">Importance of tropospheric volcanic aerosol for indirect <span class="hlt">radiative</span> <span class="hlt">forcing</span> of climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmidt, A.; Carslaw, K. S.; Mann, G. W.; Rap, A.; Pringle, K. J.; Spracklen, D. V.; Wilson, M.; Forster, P. M.</p> <p>2012-08-01</p> <p>Observations and models have shown that continuously degassing volcanoes have a potentially large effect on the natural background aerosol loading and the <span class="hlt">radiative</span> state of the atmosphere. We use a global aerosol microphysics model to quantify the impact of these volcanic emissions on the cloud albedo <span class="hlt">radiative</span> <span class="hlt">forcing</span> under pre-industrial (PI) and present-day (PD) conditions. We find that volcanic degassing increases global annual mean cloud droplet number concentrations by 40% under PI conditions, but by only 10% under PD conditions. Consequently, volcanic degassing causes a global annual mean cloud albedo effect of -1.06 W m-2 in the PI era but only -0.56 W m-2 in the PD era. This non-equal effect is explained partly by the lower background aerosol concentrations in the PI era, but also because more aerosol particles are produced per unit of volcanic sulphur emission in the PI atmosphere. The higher sensitivity of the PI atmosphere to volcanic emissions has an important consequence for the anthropogenic cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> because the large uncertainty in volcanic emissions translates into an uncertainty in the PI baseline cloud <span class="hlt">radiative</span> state. Assuming a -50/+100% uncertainty range in the volcanic sulphur flux, we estimate the annual mean anthropogenic cloud albedo <span class="hlt">forcing</span> to lie between -1.16 W m-2 and -0.86 W m-2. Therefore, the volcanically induced uncertainty in the PI baseline cloud <span class="hlt">radiative</span> state substantially adds to the already large uncertainty in the magnitude of the indirect <span class="hlt">radiative</span> <span class="hlt">forcing</span> of climate.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ACPD...12.8009S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ACPD...12.8009S"><span id="translatedtitle">Importance of tropospheric volcanic aerosol for indirect <span class="hlt">radiative</span> <span class="hlt">forcing</span> of climate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schmidt, A.; Carslaw, K. S.; Mann, G. W.; Rap, A.; Pringle, K. J.; Spracklen, D. V.; Wilson, M.; Forster, P. M.</p> <p>2012-03-01</p> <p>Observations and models have shown that continuously degassing volcanoes have a potentially large effect on the natural background aerosol loading and the <span class="hlt">radiative</span> state of the atmosphere. Here, we use a global aerosol microphysics model to quantify the impact of these volcanic emissions on the cloud albedo <span class="hlt">radiative</span> <span class="hlt">forcing</span> under pre-industrial (PI) and present-day (PD) conditions. We find that volcanic degassing increases global annual mean cloud droplet number concentrations by 40% under PI conditions, but by only 10% under PD conditions. Consequently, volcanic degassing causes a global annual mean cloud albedo effect of -1.06 W m-2 in the PI era but only -0.56 W m-2 in the PD era. This non-equal effect is explained partly by the lower background aerosol concentrations in the PI era, but also because more aerosol particles are produced per unit of volcanic sulphur emission in the PI atmosphere. The higher sensitivity of the PI atmosphere to volcanic emissions has an important consequence for the anthropogenic cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> because the large uncertainty in volcanic emissions translates into an uncertainty in the PI baseline cloud <span class="hlt">radiative</span> state. Assuming a -50/+100% uncertainty range in the volcanic sulphur flux, we estimate the annual mean anthropogenic cloud albedo <span class="hlt">forcing</span> to lie between -1.16 W m-2 and -0.86 W m-2. Therefore, the volcanically induced uncertainty in the PI baseline cloud <span class="hlt">radiative</span> state substantially adds to the already large uncertainty in the magnitude of the indirect <span class="hlt">radiative</span> <span class="hlt">forcing</span> of climate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JGRD..120.1445K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JGRD..120.1445K"><span id="translatedtitle">Near-cloud aerosols in monsoon environment and its impact on <span class="hlt">radiative</span> <span class="hlt">forcing</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Konwar, M.; Panicker, A. S.; Axisa, D.; Prabha, T. V.</p> <p>2015-02-01</p> <p>In order to understand the near-cloud aerosol properties and their impact on <span class="hlt">radiative</span> <span class="hlt">forcing</span>, we utilized in situ aircraft measurements of aerosol particles and cloud droplets during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment carried out over the Indian subcontinent in the monsoon season. From the measurement of aerosol size distribution of diameter range from 0.1 to 50 µm, we reported that aerosol concentrations could be enhanced by 81% and the effective diameter (deff, µm) by a factor of 2 near the cloud edges when compared with regions far from the cloud. These enhanced aerosol concentrations are a function of the relative humidity (RH) in the cloud-free zone, attributed to mixing and entrainment processes in the cloud edges. It is also found that for warm clouds, RH increases exponentially in the near-cloud regions. In <span class="hlt">addition</span>, deff was increased linearly with RH. Through model simulations, we found that aerosol optical depth decreases with distance from the cloud edge. Further, aerosols in cloud edges were found to increase the reflected flux by 20% compared to cloud-free regions, thus brightening the near-cloud areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A13D0363B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A13D0363B"><span id="translatedtitle">Contrail microphysical properties and <span class="hlt">radiative</span> <span class="hlt">forcing</span> over the Northern Hemisphere derived using MODIS infrared observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bedka, S. T.; Minnis, P.; Duda, D. P.; Spangenberg, D.; Chee, T.; Khlopenkov, K. V.</p> <p>2015-12-01</p> <p>One of the primary ways that air traffic affects the Earth's <span class="hlt">radiation</span> budget is through the formation of contrails. In order to quantify the <span class="hlt">radiative</span> impact of contrails, one must assess their macro and microphysical properties (e.g. contrail temperature, optical depth and effective particle size) as well as the characteristics of the environment in which they occur (e.g. background <span class="hlt">radiation</span> field and cloud properties). In-situ measurements of contrail microphysical properties are limited, and hence the retrieval of such properties from remotely sensed satellite data is useful. This paper details the ongoing progress being made to retrieve contrail properties and calculate the contrail <span class="hlt">radiative</span> <span class="hlt">forcing</span> from 2 years of MODIS (Moderate Resolution Imaging Spectroradiometer) Aqua and Terra data. Contrail microphysical properties from the seasonal months (January, April, July, October) of 2006 and 2012 are derived using an infrared-only heritage algorithm developed at NASA Langley for the Clouds and the Earth's Radiant Energy System (CERES) program. Results are subset by day/night, although the same retrieval algorithm will be used for all granules. Contrail properties and background cloud properties are then used as input into the Fu-Liou <span class="hlt">radiative</span> transfer model to compute the overall contrail <span class="hlt">radiative</span> <span class="hlt">forcing</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18..428M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016EGUGA..18..428M&link_type=ABSTRACT"><span id="translatedtitle">Holocene carbon dynamics and <span class="hlt">radiative</span> <span class="hlt">forcing</span> of three different types of peatlands in Finland</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mathijssen, Paul; Väliranta, Minna; Lohila, Annalea; Minkkinen, Kari; Tuittila, Eeva-Stiina; Tuovinen, Juha-Pekka; Korrensalo, Aino</p> <p>2016-04-01</p> <p> total carbon budget of the peatlands throughout the Holocene. We combined the long-term effect of carbon accumulation and CH4 emission and modelled Holocene atmospheric <span class="hlt">radiative</span> <span class="hlt">forcing</span>. The <span class="hlt">radiative</span> <span class="hlt">forcing</span> models show that these peatlands had a warming effect on the atmosphere for the first 1 to 2 thousand years since peat accumulation started, after which they had an increasing cooling effect as a result of the long term effect of uptake and storage of CO2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001JGR...10614875C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001JGR...10614875C"><span id="translatedtitle">Effects of 1997 Indonesian forest fires on tropospheric ozone enhancement, <span class="hlt">radiative</span> <span class="hlt">forcing</span>, and temperature change over the Hong Kong region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chan, C. Y.; Chan, L. Y.; Zheng, Y. G.; Harris, J. M.; Oltmans, S. J.; Christopher, S.</p> <p>2001-07-01</p> <p>Tropospheric ozone enhancements were measured over Hong Kong (22.2°N, 114.3°E) by electrochemical concentration cell ozonesondes during the 1997 period when many forest fires were burning in Indonesia. The enhancements have a maximum ozone concentration of up to 130 ppbv and an ozone-enhanced layer depth of 10 km. We used Total Ozone Mapping Spectrometer, advanced very high resolution radiometer satellite image, and back air trajectory to identify the source region and the transport pattern of ozone. The strong tropospheric ozone enhancements covered all of tropical Southeast Asia and subtropical south China. They were due to photochemical ozone buildup from the biomass burning emissions from the Indonesian fires. The ozone-rich air mass was transported to Hong Kong following the east Asia local Hadley circulation and an abnormal anticyclonic flow related to the El Niño phenomenon in the tropical western Pacific. A rough estimation of the <span class="hlt">radiative</span> <span class="hlt">forcing</span> due to the ozone enhancement was carried out for two cases in October and December in 1997 using a normalized tropospheric ozone <span class="hlt">radiative</span> <span class="hlt">forcing</span> parameter derived from the Unified Chemistry-Climate model [Mickley et al., 1999]. The ozone enhancements induced an <span class="hlt">additional</span> <span class="hlt">radiative</span> <span class="hlt">forcing</span> of 0.26 and 0.48 Wm-2 compared to the normal total <span class="hlt">forcing</span> of 0.48 and 0.39 Wm-2 in October and December over the Hong Kong region. Estimation of the associated surface temperature change suggests that enhanced ozone from biomass burning on the scale of the 1997 Indonesian fires may have significant impact on regional surface temperature change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JCli...16.2086T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JCli...16.2086T"><span id="translatedtitle">A Simple Moist Tropical Atmosphere Model: The Role of Cloud <span class="hlt">Radiative</span> <span class="hlt">Forcing</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tian, Baijun; Ramanathan, V.</p> <p>2003-06-01</p> <p>A simple moist model for the large-scale tropical atmospheric circulation is constructed by combining the simple models of Gill and Neelin and Held. The model describes the first baroclinic mode of the moist troposphere with variable `gross moist stability' in response to given thermodynamic <span class="hlt">forcing</span> from surface evaporation and atmospheric cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> (CRF), which is a measure of the <span class="hlt">radiative</span> effects of clouds in the atmospheric <span class="hlt">radiative</span> heating. When the present model is <span class="hlt">forced</span> solely by the observed atmospheric CRF, quantitatively reasonable Hadley and Walker circulations are obtained, such as the trades, the ascending branches in the intertropical convergence zone (ITCZ) and the South Pacific Convergence Zone (SPCZ), as well as the descending branches in the cold tongue and subtropics. However, when the model is <span class="hlt">forced</span> only by the observed surface evaporation, the Walker circulation totally disappears, and the Hadley circulation reverses. These results indicate that, in the context of a moist dynamic model, the spatial variations of atmospheric CRF are more important in terms of driving and maintaining the Hadley and Walker circulations than the spatial variation of surface evaporation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3574112','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3574112"><span id="translatedtitle"><span class="hlt">Radiation</span> <span class="hlt">force</span> of an arbitrary acoustic beam on an elastic sphere in a fluid</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sapozhnikov, Oleg A.; Bailey, Michael R.</p> <p>2013-01-01</p> <p>A theoretical approach is developed to calculate the <span class="hlt">radiation</span> <span class="hlt">force</span> of an arbitrary acoustic beam on an elastic sphere in a liquid or gas medium. First, the incident beam is described as a sum of plane waves by employing conventional angular spectrum decomposition. Then, the classical solution for the scattering of a plane wave from an elastic sphere is applied for each plane-wave component of the incident field. The net scattered field is expressed as a superposition of the scattered fields from all angular spectrum components of the incident beam. With this formulation, the incident and scattered waves are superposed in the far field to derive expressions for components of the <span class="hlt">radiation</span> stress tensor. These expressions are then integrated over a spherical surface to analytically describe the <span class="hlt">radiation</span> <span class="hlt">force</span> on an elastic sphere. Limiting cases for particular types of incident beams are presented and are shown to agree with known results. Finally, the analytical expressions are used to calculate <span class="hlt">radiation</span> <span class="hlt">forces</span> associated with two specific focusing transducers. PMID:23363086</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A43H3388A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A43H3388A"><span id="translatedtitle">Impact of Mixing State on Anthropogenic Aerosol <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> and Associated Climate Response</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Avramov, A.; Shin, H. J.; Wang, C.</p> <p>2014-12-01</p> <p>Atmospheric aerosols affect Earth's <span class="hlt">radiation</span> balance directly by scattering and absorbing solar <span class="hlt">radiation</span> and, indirectly, by changing the microphysical structure, lifetime and spatial extent of clouds. The aerosol mixing state to a large extent determines not only their optical properties (direct effect) but also their ability to serve as cloud condensation nuclei or ice nuclei (indirect effect). Results from previous research have highlighted the importance of the aerosol mixing assumptions in <span class="hlt">radiative</span> <span class="hlt">forcing</span> estimates in model simulations. Here we take a step further to analyze the differences in associated climate responses, using a multimodal, size- and mixing-dependent aerosol model (MARC) incorporated within the Community Earth System Model (CESM). The new model allows for a detailed representation of aerosol-<span class="hlt">radiation</span> and aerosol-cloud interactions by including an improved treatment of aerosol mixing state and composition. First, we estimate and compare the magnitudes of direct and indirect <span class="hlt">forcing</span> of anthropogenic aerosols under different mixing assumptions. We then carry out several century-long fully-coupled climate simulations designed to isolate the climate responses to direct and indirect <span class="hlt">forcings</span> under the same aerosol mixing assumptions. In our analysis, we specifically focus on the following three climate response components: 1) cloud distribution and coverage; 2) precipitation amount and distribution; and 3) changes in circulation patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeoRL..40.1760S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeoRL..40.1760S"><span id="translatedtitle"><span class="hlt">Radiation</span> of inertial kinetic energy as near-inertial waves <span class="hlt">forced</span> by tropical Pacific Easterly waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Soares, S. M.; Richards, K. J.</p> <p>2013-05-01</p> <p>Easterly waves (EW) are low level tropical atmospheric disturbances able to resonantly <span class="hlt">force</span> strong mixed layer inertial currents. Using data from two Tropical Atmosphere Ocean/Eastern Pacific Investigation of Climate Processes (TAO/EPIC) buoys located along 95°W and a multiparameterization one-dimensional turbulence model, we examine how the EW-<span class="hlt">forced</span> surface inertial kinetic energy (IKE) loss is partitioned between turbulent dissipation and near-inertial wave (NIW) <span class="hlt">radiation</span>. Several EW-<span class="hlt">forcing</span> events are individually simulated with a version of the General Ocean Turbulence Model modified to include a linear damping coefficient to account for the NIW <span class="hlt">radiation</span> energy sink. The kinetic energy budget of these simulations shows that NIW <span class="hlt">radiation</span> accounted for typically 50-60% of the IKE loss and in some cases up to 80%. These empirically derived estimates of the contribution of the <span class="hlt">radiated</span> NIWs to the loss of wind-induced surface IKE are substantially higher than recently published numerical estimates. Furthermore, the results indicate that the vertical NIW energy flux increases linearly with the wind input of IKE, an easily obtained quantity. The NIW vertical energy flux estimated for a single near-resonant event is comparable to extreme north Pacific wintertime-averaged fluxes, indicating the existence of important episodic sources of near-inertial energy available for mixing within and below the thermocline in the tropical region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.A54C..02S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.A54C..02S"><span id="translatedtitle">Present and potential future contributions of sulfate, black and organic carbon aerosols from China to global air quality, premature mortality and <span class="hlt">radiative</span> <span class="hlt">forcing</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Saikawa, E.; Naik, V.; Horowitz, L. W.; Liu, J.; Mauzerall, D. L.</p> <p>2008-12-01</p> <p>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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> (cooling) while BC exerts positive <span class="hlt">forcing</span> (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 <span class="hlt">radiative</span> <span class="hlt">forcing</span>. Using global models of chemical transport (MOZART-2) and <span class="hlt">radiative</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> in 2000 and 2030. In 2000, we estimate these aerosols cause 385,320 premature deaths in China and an <span class="hlt">additional</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> from SO42- and OC is larger than the positive <span class="hlt">forcing</span> from BC, the Chinese aerosols lead to global net direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AdAtS..23..317S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AdAtS..23..317S"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">forcing</span> of SO2 and NOx: A case study in Beijing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Z. A.; Wang, X. Y.; Zeng, X. N.</p> <p>2006-03-01</p> <p>A case study was performed in Beijing in 2000 to observe concentrations Of SO2 and NO, in the atmosphere and to evaluate their <span class="hlt">radiative</span> impact. It was found that the concentrations of these gases are usually high in the morning due to a temperature inversion in the boundary layer. The average concentrations obtained from the observations are much higher than those used in the McClatchey reference atmosphere. The <span class="hlt">radiative</span> impacts of these gases are calculated using a line-by-line <span class="hlt">radiative</span> transfer model. The results show that the <span class="hlt">radiative</span> <span class="hlt">forcing</span> at the surface due to SO2 is 0.0576 W m(-2) and that due to NOx is 0.0032 W m(-2). These figures are almost compatible with that due to CFC11.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/pages/biblio/1209153-magnetic-force-microscopy-study-zr2co11-based-nanocrystalline-materials-effect-mo-addition','SCIGOV-DOEP'); return false;" href="http://www.osti.gov/pages/biblio/1209153-magnetic-force-microscopy-study-zr2co11-based-nanocrystalline-materials-effect-mo-addition"><span id="translatedtitle">Magnetic <span class="hlt">Force</span> Microscopy Study of Zr2Co11 -Based Nanocrystalline Materials: Effect of Mo <span class="hlt">Addition</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGESBeta</a></p> <p>Yue, Lanping; Jin, Yunlong; Zhang, Wenyong; Sellmyer, David J.</p> <p>2015-01-01</p> <p>Tmore » he <span class="hlt">addition</span> of Molybdenum was used to modify the nanostructure and enhance coercivity of rare-earth-free Zr2Co11-based nanocrystalline permanent magnets. he effect of Mo <span class="hlt">addition</span> on magnetic domain structures of melt spun nanocrystalline Zr16Co84-xMox(x=0, 0.5, 1, 1.5, and 2.0) ribbons has been investigated. It was found that magnetic properties and local domain structures are strongly influenced by Mo doping. he coercivity of the samples increases with the increase in Mo content (x≤1.5). he maximum energy product(BH)maxincreases with increasingxfrom 0.5 MGOe forx=0to a maximum value of 4.2 MGOe forx=1.5. he smallest domain size with a relatively short magnetic correlation length of 128 nm and largest root-mean-square phase shiftΦrmsvalue of 0.66° are observed for thex=1.5. he optimal Mo <span class="hlt">addition</span> promotes magnetic domain structure refinement and thus leads to a significant increase in coercivity and energy product in this sample.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AnGeo..20.2105S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AnGeo..20.2105S"><span id="translatedtitle">Aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> over land: effect of surface and cloud reflection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Satheesh, S. K.</p> <p>2002-12-01</p> <p>It is now clearly understood that atmospheric aerosols have a significant impact on climate due to their important role in modifying the incoming solar and outgoing infrared <span class="hlt">radiation</span>. The question of whether aerosol cools (negative <span class="hlt">forcing</span>) or warms (positive <span class="hlt">forcing</span>) the planet depends on the relative dominance of absorbing aerosols. Recent investigations over the tropical Indian Ocean have shown that, irrespective of the comparatively small percentage contribution in optical depth ( ~ 11%), soot has an important role in the overall <span class="hlt">radiative</span> <span class="hlt">forcing</span>. However, when the amount of absorbing aerosols such as soot are significant, aerosol optical depth and chemical composition are not the only determinants of aerosol climate effects, but the altitude of the aerosol layer and the altitude and type of clouds are also important. In this paper, the aerosol <span class="hlt">forcing</span> in the presence of clouds and the effect of different surface types (ocean, soil, vegetation, and different combinations of soil and vegetation) are examined based on model simulations, demonstrating that aerosol <span class="hlt">forcing</span> changes sign from negative (cooling) to positive (warming) when reflection from below (either due to land or clouds) is high.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014AmJPh..82...95D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014AmJPh..82...95D&link_type=ABSTRACT"><span id="translatedtitle">Acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> due to a diverging wave: Demonstration and theory</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Denardo, Bruce C.; Freemyers, Stanley G.; Schock, Michael P.; Sundem, Scott T.</p> <p>2014-02-01</p> <p>A <span class="hlt">radiation</span> <span class="hlt">force</span> is the time-averaged <span class="hlt">force</span> exerted by any kind of wave on a body. In the case of a divergent traveling acoustic wave, it is known that a relatively small rigid body can experience a <span class="hlt">radiation</span> <span class="hlt">force</span> that is directed toward the source. We show that this effect can be readily demonstrated with a styrofoam sphere pendulum near a horizontally directed loudspeaker that is emitting sound of sufficiently high amplitude and low frequency. The attraction is surprising because repulsive <span class="hlt">forces</span> are exerted by a traveling plane wave and by an outward jetting or "wind" from the loudspeaker. We argue that the attractive <span class="hlt">force</span> near a source that is small compared to the wavelength can be roughly understood and calculated as a time-averaged Bernoulli effect, if scattering is ignored. The result is within a factor of two of rigorous published results based on scattering calculations, when these results are specialized to the case of a rigid body whose average density is much greater than the density of the fluid. However, repulsion occurs when the average density of the body is less than the density of the fluid, in which case our Bernoulli result completely fails.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22218631','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22218631"><span id="translatedtitle">Ponderomotive <span class="hlt">force</span> on solitary structures created during <span class="hlt">radiation</span> pressure acceleration of thin foils</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tripathi, Vipin K.; Sharma, Anamika</p> <p>2013-05-15</p> <p>We estimate the ponderomotive <span class="hlt">force</span> on an expanded inhomogeneous electron density profile, created in the later phase of laser irradiated diamond like ultrathin foil. When ions are uniformly distributed along the plasma slab and electron density obeys the Poisson's equation with space charge potential equal to negative of ponderomotive potential, φ=−φ{sub p}=−(mc{sup 2}/e)(γ−1), where γ=(1+|a|{sup 2}){sup 1/2}, and |a| is the normalized local laser amplitude inside the slab; the net ponderomotive <span class="hlt">force</span> on the slab per unit area is demonstrated analytically to be equal to <span class="hlt">radiation</span> pressure <span class="hlt">force</span> for both overdense and underdense plasmas. In case electron density is taken to be frozen as a Gaussian profile with peak density close to relativistic critical density, the ponderomotive <span class="hlt">force</span> has non-monotonic spatial variation and sums up on all electrons per unit area to equal <span class="hlt">radiation</span> pressure <span class="hlt">force</span> at all laser intensities. The same result is obtained for the case of Gaussian ion density profile and self consistent electron density profile, obeying Poisson's equation with φ=−φ{sub p}.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.B53E0721B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.B53E0721B"><span id="translatedtitle">Conterminous United States Surface <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> due to Contemporary Land Cover Land Use Albedo Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barnes, C. A.; Roy, D. P.</p> <p>2012-12-01</p> <p>Recently available Landsat land cover land use (LCLU) change information for four epochs, 1973-1980, 1980-1986, 1986-1992 and 1992-2000, and MODerate Resolution Imaging Spectroradiometer (MODIS) albedo and snow cover data are used to estimate LCLU albedo change surface <span class="hlt">radiative</span> <span class="hlt">forcing</span> for the conterminous United States (CONUS) for each epoch and for 1973 to 2000. Landsat 10 × 10 km or 20 × 20 km LCLU classification maps for 1973, 1980, 1986, 1992 and 2000 located using a stratified random sampling methodology with respect to 84 contiguous CONUS ecoregions are used to provide ecoregion and CONUS estimates. A CONUS scale warming (0.0037 Wm-2) due to LCLU albedo change from 1973 to 2000 is estimated associated with decreasing agricultural and forested lands and increasing developed and grassland/shrublands. The 1986 to 1992 period had the highest overall CONUS <span class="hlt">forcing</span> (0.0093 Wm-2) due to agricultural land conversion, attributed primarily to the 1985 Farm Bill that established the Conservation Reserve Program. The <span class="hlt">radiative</span> <span class="hlt">forcing</span> for individual ecoregions varied geographically in sign and magnitude, with the most negative <span class="hlt">forcings</span> (as low as -0.8630 Wm-2) due to forest loss, and the most positive <span class="hlt">forcings</span> (up to 0.2640 Wm-2) due to the conversion of grasslands/shrublands. These results make an important contribution to quantifying the role of LCLU change on the climate system, and underscore the need for repeat, wall-to-wall, spatially-explicit national LCLU mapping.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1049015','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1049015"><span id="translatedtitle">Global Distribution and Climate <span class="hlt">Forcing</span> of Marine Organic Aerosol - Part 2: Effects on Cloud Properties and <span class="hlt">Radiative</span> <span class="hlt">Forcing</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gantt, Brett; Xu, Jun; Meskhidze, N.; Zhang, Yang; Nenes, Athanasios; Ghan, Steven J.; Liu, Xiaohong; Easter, Richard C.; Zaveri, Rahul A.</p> <p>2012-07-25</p> <p>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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> resulting from marine organic aerosols. Model simulations show that the anthropogenic aerosol indirect <span class="hlt">forcing</span> (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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4297281','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4297281"><span id="translatedtitle">A simulation technique for 3D MR-guided acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> imaging</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Payne, Allison; de Bever, Josh; Farrer, Alexis; Coats, Brittany; Parker, Dennis L.; Christensen, Douglas A.</p> <p>2015-01-01</p> <p>Purpose: In magnetic resonance-guided focused ultrasound (MRgFUS) therapies, the in situ characterization of the focal spot location and quality is critical. MR acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> imaging (MR-ARFI) is a technique that measures the tissue displacement caused by the <span class="hlt">radiation</span> <span class="hlt">force</span> exerted by the ultrasound beam. This work presents a new technique to model the displacements caused by the <span class="hlt">radiation</span> <span class="hlt">force</span> of an ultrasound beam in a homogeneous tissue model. Methods: When a steady-state point-source <span class="hlt">force</span> acts internally in an infinite homogeneous medium, the displacement of the material in all directions is given by the Somigliana elastostatic tensor. The <span class="hlt">radiation</span> <span class="hlt">force</span> field, which is caused by absorption and reflection of the incident ultrasound intensity pattern, will be spatially distributed, and the tensor formulation takes the form of a convolution of a 3D Green’s function with the <span class="hlt">force</span> field. The dynamic accumulation of MR phase during the ultrasound pulse can be theoretically accounted for through a time-of-arrival weighting of the Green’s function. This theoretical model was evaluated experimentally in gelatin phantoms of varied stiffness (125-, 175-, and 250-bloom). The acoustic and mechanical properties of the phantoms used as parameters of the model were measured using independent techniques. Displacements at focal depths of 30- and 45-mm in the phantoms were measured by a 3D spin echo MR-ARFI segmented-EPI sequence. Results: The simulated displacements agreed with the MR-ARFI measured displacements for all bloom values and focal depths with a normalized RMS difference of 0.055 (range 0.028–0.12). The displacement magnitude decreased and the displacement pattern broadened with increased bloom value for both focal depths, as predicted by the theory. Conclusions: A new technique that models the displacements caused by the <span class="hlt">radiation</span> <span class="hlt">force</span> of an ultrasound beam in a homogeneous tissue model theory has been rigorously validated through comparison</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22413433','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22413433"><span id="translatedtitle">A simulation technique for 3D MR-guided acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> imaging</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Payne, Allison; Bever, Josh de; Farrer, Alexis; Coats, Brittany; Parker, Dennis L.; Christensen, Douglas A.</p> <p>2015-02-15</p> <p>Purpose: In magnetic resonance-guided focused ultrasound (MRgFUS) therapies, the in situ characterization of the focal spot location and quality is critical. MR acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> imaging (MR-ARFI) is a technique that measures the tissue displacement caused by the <span class="hlt">radiation</span> <span class="hlt">force</span> exerted by the ultrasound beam. This work presents a new technique to model the displacements caused by the <span class="hlt">radiation</span> <span class="hlt">force</span> of an ultrasound beam in a homogeneous tissue model. Methods: When a steady-state point-source <span class="hlt">force</span> acts internally in an infinite homogeneous medium, the displacement of the material in all directions is given by the Somigliana elastostatic tensor. The <span class="hlt">radiation</span> <span class="hlt">force</span> field, which is caused by absorption and reflection of the incident ultrasound intensity pattern, will be spatially distributed, and the tensor formulation takes the form of a convolution of a 3D Green’s function with the <span class="hlt">force</span> field. The dynamic accumulation of MR phase during the ultrasound pulse can be theoretically accounted for through a time-of-arrival weighting of the Green’s function. This theoretical model was evaluated experimentally in gelatin phantoms of varied stiffness (125-, 175-, and 250-bloom). The acoustic and mechanical properties of the phantoms used as parameters of the model were measured using independent techniques. Displacements at focal depths of 30- and 45-mm in the phantoms were measured by a 3D spin echo MR-ARFI segmented-EPI sequence. Results: The simulated displacements agreed with the MR-ARFI measured displacements for all bloom values and focal depths with a normalized RMS difference of 0.055 (range 0.028–0.12). The displacement magnitude decreased and the displacement pattern broadened with increased bloom value for both focal depths, as predicted by the theory. Conclusions: A new technique that models the displacements caused by the <span class="hlt">radiation</span> <span class="hlt">force</span> of an ultrasound beam in a homogeneous tissue model theory has been rigorously validated through comparison</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1083402','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1083402"><span id="translatedtitle">Host Model Uncertainties in Aerosol <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> Estimates: Results from the AeroCom Prescribed Intercomparison Study</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>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</p> <p>2013-03-20</p> <p>Simulated multi-model "diversity" in aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> estimates is often perceived as mea- sure of aerosol uncertainty. However, current models used for aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> calculations vary considerably in model components relevant for <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> experiments through prescription of identical aerosol <span class="hlt">radiative</span> properties in nine participating models. Even with prescribed aerosol <span class="hlt">radiative</span> properties,simulated clear-sky and all-sky aerosol <span class="hlt">radiative</span> <span class="hlt">forcings</span> show significant diversity. For a purely scattering case with globally constant optical depth of 0.2, the global-mean all-sky top-of-atmosphere <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> variability owing to absorption is low, with relative standard deviations of 9% clear-sky and 12% all-sky. Scaling the <span class="hlt">forcing</span> standard deviation for a purely scattering case to match the sulfate <span class="hlt">radiative</span> in the AeroCom Direct Effect experiment, demonstrates that host model uncertain- ties could explain about half of the overall sulfate <span class="hlt">forcing</span> diversity of 0.13 Wm-2 in the AeroCom Direct <span class="hlt">Radiative</span> Effect experiment. Host model errors in aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> are largest in regions of uncertain host model components, such as stratocumulus cloud decks or areas with poorly constrained.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26745353','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26745353"><span id="translatedtitle">Ground-Level Ozone Following Astrophysical Ionizing <span class="hlt">Radiation</span> Events: An <span class="hlt">Additional</span> Biological Hazard?</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thomas, Brian C; Goracke, Byron D</p> <p>2016-01-01</p> <p>Astrophysical ionizing <span class="hlt">radiation</span> events such as supernovae, gamma-ray bursts, and solar proton events have been recognized as a potential threat to life on Earth, primarily through depletion of stratospheric ozone and subsequent increase in solar UV <span class="hlt">radiation</span> at Earth's surface and in the upper levels of the ocean. Other work has also considered the potential impact of nitric acid rainout, concluding that no significant threat is likely. Not yet studied to date is the potential impact of ozone produced in the lower atmosphere following an ionizing <span class="hlt">radiation</span> event. Ozone is a known irritant to organisms on land and in water and therefore may be a significant <span class="hlt">additional</span> hazard. Using previously completed atmospheric chemistry modeling, we examined the amount of ozone produced in the lower atmosphere for the case of a gamma-ray burst and found that the values are too small to pose a significant <span class="hlt">additional</span> threat to the biosphere. These results may be extended to other ionizing <span class="hlt">radiation</span> events, including supernovae and extreme solar proton events. PMID:26745353</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/951034','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/951034"><span id="translatedtitle">Surface shortwave aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> during the Atmospheric <span class="hlt">Radiation</span> Measurement Mobile Facility deployment in Niamey, Niger</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>McFarlane, Sally A.; Kassianov, Evgueni I.; Barnard, James C.; Flynn, Connor J.; Ackerman, Thomas P.</p> <p>2009-03-18</p> <p>This study presents ground-based remote sensing measurements of aerosol optical properties and corresponding shortwave surface <span class="hlt">radiative</span> effect calculations for the deployment of the Atmospheric <span class="hlt">Radiation</span> Measurement (ARM) Program’s Mobile Facility (AMF) to Niamey, Niger during 2006. Aerosol optical properties including aerosol optical depth (AOD), single scattering albedo (SSA), and asymmetry parameter (AP) were derived from multi-filter rotating shadowband radiometer (MFRSR) measurements during the two dry seasons (Jan-Apr and Oct-Dec) at Niamey. The vertical distribution of aerosol extinction was derived from the collocated micropulse lidar (MPL). The aerosol optical properties and vertical distribution of extinction varied significantly throughout the year, with higher AOD, lower SSA, and deeper aerosol layers during the Jan-Apr time period, when biomass burning aerosol layers were more frequent. Using the retrieved aerosol properties and vertical extinction profiles, broadband shortwave surface fluxes and atmospheric heating rate profiles were calculated. Corresponding calculations with no aerosol were used to estimate the aerosol direct <span class="hlt">radiative</span> effect at the surface. Comparison of the calculated surface fluxes to observed fluxes for non-cloudy periods indicated that the remote sensing retrievals provided a reasonable estimation of the optical properties, with mean differences between calculated and observed fluxes of less than 5 W/m2 and RMS differences less than 25 W/m2. Sensitivity tests for a particular case study showed that the observed fluxes could be matched with variations of < 10% in the inputs to the <span class="hlt">radiative</span> transfer model. We estimated the daily-averaged aerosol <span class="hlt">radiative</span> effect at the surface by subtracting the clear calculations from the aerosol calculations. The average daily SW aerosol <span class="hlt">radiative</span> effect over the study period was -27 W/m2, which is comparable to values estimated from satellite data and from climate models with sophisticated</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006cosp...36.1251S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006cosp...36.1251S"><span id="translatedtitle">Seasonal variation of atmospheric aerosols and its impact on aerosol <span class="hlt">radiation</span> <span class="hlt">forcing</span> over Delhi</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Singh, S.; Srivastava, M. K.; Bano, T.; Nath, S.; Tanwar, R. S.; Singh, R.</p> <p></p> <p>Seasonal variability in suspended particulate matter concentration optical properties of aerosol and <span class="hlt">radiation</span> flux have been studied for Delhi station India using long-term data that comprised of ground based and satellite-borne observations Ground based measurements were taken by a hand-held portable spectrometer MICROTOPS II Solar Light Co Inc USA operating at central wavelengths 340 500 675 870 and 1020 nms FWHM pm 2-10 nm The global <span class="hlt">radiation</span> flux was measured using the CM-21 pyranometer Kipp and Zonen Germany for wavelength range 305-2800 nm The flux for 290-320 nm wavelength range was measured using UV-Biometer Solar Light Co Inc USA The seasonal change in <span class="hlt">radiative</span> <span class="hlt">forcing</span> due to seasonal variability in number density and character of the aerosols is done using Santa Barbara Discrete Ordinate <span class="hlt">Radiation</span> Transfer model SBDART Since the chemical character of the dominating aerosols for different season was not readily available an estimation of the aerosol composition was done using Optical Properties of Aerosols and Cloud OPAC model The output of the OPAC model gives the required parameters for the estimation of <span class="hlt">radiation</span> <span class="hlt">forcing</span> by SBDART These include single scattering albedo and asymmetry parameter Initial results reveal three specific seasonal characteristics of aerosols pre-monsoon post monsoon and the winter excluding monsoon period when data is highly irregular due to predominantly cloudy conditions and heavy downpour During pre-monsoon high aerosol optical depth AOD and near zero often</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27369138','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27369138"><span id="translatedtitle">Unphysical consequences of negative absorbed power in linear passive scattering: Implications for <span class="hlt">radiation</span> <span class="hlt">force</span> and torque.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Marston, Philip L; Zhang, Likun</p> <p>2016-06-01</p> <p>Contrary to some claims, the absorbed power associated with linear scattering of sound by passive objects in ideal fluids must be non-negative. Such unphysical claims suggest analytical or computational error, or use of an unphysical constitutive relation for material properties. The close connection with the evaluation of acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on targets according to Westervelt's formulation [J. Acoust. Soc. Am. 29, 26-29 (1957)], recently generalized to certain acoustic beams, is briefly reviewed along with the theory of acoustic <span class="hlt">radiation</span> torque on axisymmetric targets with power absorption. Applications to viscous dissipation and to issues pertaining to active targets are also examined. PMID:27369138</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995RaPC...45..191H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995RaPC...45..191H"><span id="translatedtitle"><span class="hlt">Radiation</span> graft modification of ethylene-propylene rubber—II. Effect of <span class="hlt">additives</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Haddadi-Asl, V.; Burford, R. P.; Garnett, J. L.</p> <p>1995-02-01</p> <p>The effect of multifunctional acrylic <span class="hlt">additives</span> including TMPTA, PEGDA and PGTA on the <span class="hlt">radiation</span> grafting of hydrophilic vinyl monomers onto ethylene—propylene elastomer (EPM rubbers) was studied. This work centres upon gamma irradiation-induced grafting of acrylamide (AAm), N-vinyl-2-pyrrolidone (NVP), 2-hydroxyethyl methacrylate (HEMA) and acrylonitrile (AN) onto EPM rubber by the simultaneous method. Water proved to be an effective solvent but methanol lowered grafting. Sulphuric acid was detrimental to both homopolymerisation and grafting, a result consistent with the theory proposed for the role of this <span class="hlt">additive</span> in polymer grafting systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26066270','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26066270"><span id="translatedtitle">Influence of <span class="hlt">radiation</span> reaction <span class="hlt">force</span> on ultraintense laser-driven ion acceleration.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Capdessus, R; McKenna, P</p> <p>2015-05-01</p> <p>The role of the <span class="hlt">radiation</span> reaction <span class="hlt">force</span> in ultraintense laser-driven ion acceleration is investigated. For laser intensities ∼10(23)W/cm(2), the action of this <span class="hlt">force</span> on electrons is demonstrated in relativistic particle-in-cell simulations to significantly enhance the energy transfer to ions in relativistically transparent targets, but strongly reduce the ion energy in dense plasma targets. An expression is derived for the revised piston velocity, and hence ion energy, taking account of energy loses to synchrotron <span class="hlt">radiation</span> generated by electrons accelerated in the laser field. Ion mass is demonstrated to be important by comparing results obtained with proton and deuteron plasma. The results can be verified in experiments with cryogenic hydrogen and deuterium targets. PMID:26066270</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19683381','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19683381"><span id="translatedtitle">In vivo quantification of liver stiffness in a rat model of hepatic fibrosis with acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Michael H; Palmeri, Mark L; Guy, Cynthia D; Yang, Liu; Hedlund, Laurence W; Diehl, Anna Mae; Nightingale, Kathryn R</p> <p>2009-10-01</p> <p>Liver fibrosis is currently staged using needle biopsy, a highly invasive procedure with a number of disadvantages. Measurement of liver stiffness changes that accompany progression of the disease may provide a quantitative and noninvasive method to assess the health of the liver. The purpose of this study is to investigate the correlation between liver stiffness measured by <span class="hlt">radiation</span> <span class="hlt">force</span> induced shear waves and disease related changes in the liver. An <span class="hlt">additional</span> aim is to present initial findings on the effects of liver viscosity on <span class="hlt">radiation</span> <span class="hlt">force</span> induced shear wave morphology. Liver fibrosis was induced in 10 rats using carbon tetrachloride (CCl(4)), while five rats acted as controls. Liver stiffness was measured in vivo in all rats after a treatment period of 8 weeks using a modified Siemens SONOLINE Antares scanner (Siemens Medical Solutions USA, Ultrasound Division, Issaquah, WA, USA). The spatial coherence of <span class="hlt">radiation</span> <span class="hlt">force</span> induced shear waves propagating in the viscoelastic rat liver decreased significantly with propagation distance, compared with shear waves in an elastic phantom and a finite element model of a purely elastic medium. Animals were sacrificed after imaging and liver samples were taken for histopathologic analysis and collagen quantification using picrosirius red staining and hydroxyproline assay. At the end of the treatment period, five rats had healthy livers (stage F0), while six had severe fibrosis (F3) and the rest had light to moderate fibrosis (F1 and F2). The measured liver stiffness for the F0 group was 1.5+/-0.1 kPa (mean+/-95% confidence interval) and for F3 livers was 1.8+/-0.2 kPa. In this study, liver stiffness was found to be linearly correlated with the amount of collagen in the liver measured by picrosirius red staining (r(2)=0.43, p=0.008). In <span class="hlt">addition</span>, stiffness spatial heterogeneity was also linearly correlated with liver collagen content (r(2)=0.58, p=0.001) by picrosirius red staining. These results are consistent</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014GeoRL..41.9040R&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014GeoRL..41.9040R&link_type=ABSTRACT"><span id="translatedtitle">Uncertainty in the magnitude of aerosol-cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> over recent decades</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>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.</p> <p>2014-12-01</p> <p>Aerosols and their effect on the <span class="hlt">radiative</span> 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 <span class="hlt">forcing</span> 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 <span class="hlt">forcings</span> leads to a near-zero global mean cloud albedo effect <span class="hlt">forcing</span>. 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 <span class="hlt">forced</span> response. Proportional contributions to <span class="hlt">forcing</span> variance from aerosol processes and natural and anthropogenic emissions are found to be period dependent. To better constrain <span class="hlt">forcing</span> estimates, the processes that dominate uncertainty on the timescale of interest must be better understood.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19950039683&hterms=magnitudes+derived&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmagnitudes%2Bderived','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19950039683&hterms=magnitudes+derived&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dmagnitudes%2Bderived"><span id="translatedtitle">Seasonal variation of surface and atmospheric cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> over the globe derived from satellite data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gupta, Shashi K.; Staylor, W. Frank; Darnell, Wayne L.; Wilber, Anne C.; Ritchey, Nancy A.</p> <p>1993-01-01</p> <p>Global distributions of surface and atmospheric cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> parameters have been derived using parameterized <span class="hlt">radiation</span> models with satellite meteorological data from the International Satellite Cloud Climatology Project, and directly measured top-of-atmosphere <span class="hlt">radiative</span> fluxes from the Earth <span class="hlt">Radiation</span> Budget Experiment. Specifically, shortwave, longwave, and total cloud <span class="hlt">forcing</span> at the surface, and column-averaged values of longwave cloud <span class="hlt">forcing</span> of the atmosphere were derived for the midseasonal months of April, July, and October 1985 and January 1986, covering a complete annual cycle. Seasonal variability is illustrated by comparing the results for July 1985 and January 1986, which represent the seasonal extremes. Surface shortwave cloud <span class="hlt">forcing</span> is always negative, representing a cooling of the surface, with strongest cooling (-120 to -180 W/sq m) occurring over midlatitude storm tracks of the summer hemisphere. Surface longwave cloud <span class="hlt">forcing</span> is always positive, representing a warming of the surface, with strongest warming (60 to 75 W/sq m) occurring over storm tracks of the winter hemisphere. Zonal averages show the entire summer hemisphere dominated by shortwave cooling, the middle and high latitudes of the winter hemisphere dominated by longwave warming, and a broad zone of transition in between. The globally averaged total cloud <span class="hlt">forcing</span> amounts to a cooling throughout the year, ranging from a low of about -12 W/sq m for July 1985 to a high of about -25 W/sq m for January 1986. The longwave cloud <span class="hlt">forcing</span> of the atmosphere shows a strong warming over deep convective regions in the tropics and a moderate cooling outside the tropics, amounting to a weak cooling (-2 to -5 W/sq m) in the global average. Comparisons of the results with general circulation model simulations show broad qualitative agreement regarding the locations of prominent warming and cooling regions. Quantitative comparisons, on the other hand, show significant differences between the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/934395','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/934395"><span id="translatedtitle">Effects of aerosol optical properties on deep convective clouds and <span class="hlt">radiative</span> <span class="hlt">forcing</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Fan, Jiwen; Zhang, Renyi; Tao, Wei-Kuo; Mohr, Karen I</p> <p>2008-04-23</p> <p>The aerosol <span class="hlt">radiative</span> effects (ARE) on the deep convective clouds are investigated by using a spectral-bin cloud-resolving model coupled with a <span class="hlt">radiation</span> scheme and an explicit land surface model. The sensitivity of cloud properties and the associated <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 without ARE, the cloud fraction and optical depth decrease by about 18% and 20%, respectively. Ice particle number concentrations, liquid water path, ice water path, and droplet size decrease by more than 15% 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 0.6 K day<sup>-1</sup> higher at 2 km), both of which lead to a more stable atmosphere and hence weaker convection. The weaker convection explains the less cloudiness, lower cloud optical depth, less LWP and IWP, smaller droplet size, and less precipitation resulting from the ARE. The daytime-mean direct <span class="hlt">forcing</span> induced by black carbon is about 2.2 W m<sup>-2</sup> at the top of atmosphere (TOA) and -17.4 W m<sup>-2</sup> at the surface for SSA of 0.85. The semi-direct <span class="hlt">forcing</span> is positive, about 10 and 11.2 W m<sup>-2</sup> at the TOA and surface, respectively. Both the TOA and surface total <span class="hlt">radiative</span> <span class="hlt">forcing</span> values are strongly negative for the deep convective clouds, attributed mostly to aerosol indirect <span class="hlt">forcing</span>. Aerosol direct and semi-direct effects are very sensitive to SSA when aerosol optical depth is high. Because the positive semi-direct <span class="hlt">forcing</span> compensates the negative direct <span class="hlt">forcing</span> 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 atmosphere due to enhanced</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008JGRD..113.8209F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008JGRD..113.8209F"><span id="translatedtitle">Effects of aerosol optical properties on deep convective clouds and <span class="hlt">radiative</span> <span class="hlt">forcing</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fan, Jiwen; Zhang, Renyi; Tao, Wei-Kuo; Mohr, Karen I.</p> <p>2008-04-01</p> <p>The aerosol <span class="hlt">radiative</span> effects (ARE) on the deep convective clouds are investigated by using a spectral-bin cloud-resolving model coupled with a <span class="hlt">radiation</span> scheme and an explicit land surface model. The sensitivity of cloud properties and the associated <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 without ARE, the cloud fraction and optical depth decrease by about 18% and 20%, respectively. Ice particle number concentrations, liquid water path, ice water path, and droplet size decrease by more than 15% 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 0.6 K day-1 higher at 2 km), both of which lead to a more stable atmosphere and hence weaker convection. The weaker convection explains the less cloudiness, lower cloud optical depth, less LWP and IWP, smaller droplet size, and less precipitation resulting from the ARE. The daytime-mean direct <span class="hlt">forcing</span> induced by black carbon is about 2.2 W m-2 at the top of atmosphere (TOA) and -17.4 W m-2 at the surface for SSA of 0.85. The semi-direct <span class="hlt">forcing</span> is positive, about 10 and 11.2 W m-2 at the TOA and surface, respectively. Both the TOA and surface total <span class="hlt">radiative</span> <span class="hlt">forcing</span> values are strongly negative for the deep convective clouds, attributed mostly to aerosol indirect <span class="hlt">forcing</span>. Aerosol direct and semi-direct effects are very sensitive to SSA when aerosol optical depth is high. Because the positive semi-direct <span class="hlt">forcing</span> compensates the negative direct <span class="hlt">forcing</span> 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 atmosphere due to enhanced surface cooling and atmospheric heating.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ACP....15.7841L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ACP....15.7841L"><span id="translatedtitle">Brown carbon aerosol in the North American continental troposphere: sources, abundance, and <span class="hlt">radiative</span> <span class="hlt">forcing</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, J.; Scheuer, E.; Dibb, J.; Diskin, G. S.; Ziemba, L. D.; Thornhill, K. L.; Anderson, B. E.; Wisthaler, A.; Mikoviny, T.; Devi, J. J.; Bergin, M.; Perring, A. E.; Markovic, M. Z.; Schwarz, J. P.; Campuzano-Jost, P.; Day, D. A.; Jimenez, J. L.; Weber, R. J.</p> <p>2015-07-01</p> <p>Chemical components of organic aerosol (OA) selectively absorb light at short wavelengths. In this study, the prevalence, sources, and optical importance of this so-called brown carbon (BrC) aerosol component are investigated throughout the North American continental tropospheric column during a summer of extensive biomass burning. Spectrophotometric absorption measurements on extracts of bulk aerosol samples collected from an aircraft over the central USA were analyzed to directly quantify BrC abundance. BrC was found to be prevalent throughout the 1 to 12 km altitude measurement range, with dramatic enhancements in biomass-burning plumes. BrC to black carbon (BC) ratios, under background tropospheric conditions, increased with altitude, consistent with a corresponding increase in the absorption Ångström exponent (AAE) determined from a three-wavelength particle soot absorption photometer (PSAP). The sum of inferred BC absorption and measured BrC absorption at 365 nm was within 3 % of the measured PSAP absorption for background conditions and 22 % for biomass burning. A <span class="hlt">radiative</span> transfer model showed that BrC absorption reduced top-of-atmosphere (TOA) aerosol <span class="hlt">forcing</span> by ~ 20 % in the background troposphere. Extensive <span class="hlt">radiative</span> model simulations applying this study background tropospheric conditions provided a look-up chart for determining <span class="hlt">radiative</span> <span class="hlt">forcing</span> efficiencies of BrC as a function of a surface-measured BrC : BC ratio and single scattering albedo (SSA). The chart is a first attempt to provide a tool for better assessment of brown carbon's <span class="hlt">forcing</span> effect when one is limited to only surface data. These results indicate that BrC is an important contributor to direct aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AtmEn..77...98P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AtmEn..77...98P"><span id="translatedtitle">Observations of Black Carbon characteristics and <span class="hlt">radiative</span> <span class="hlt">forcing</span> over a Global Atmosphere Watch supersite in Korea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Panicker, A. S.; Park, Sung-Hwa; Lee, Dong-In; Kim, Dong-Chul; Jung, Woon-Seon; Jang, Sang-Min; Jeong, Jong-Hoon; Kim, Dong-Soon; Yu, Jegyu; Jeong, Harrison</p> <p>2013-10-01</p> <p>This paper provides an account of observed variations in Black carbon (BC) mass concentrations and BC induced <span class="hlt">radiative</span> <span class="hlt">forcing</span> for the first time over a background Global Atmosphere Watch (GAW) site, Anmyeon in South Korea. BC concentrations were continuously measured over the site during January 2003-December 2004 periods using an Aethalometer. BC showed higher concentrations during 2003 in majority of the months (except in January, August and October). BC found to be showing higher concentrations in September 2003, with values reaching up to 3 μg m-3 over the site. It also showed higher peaks in May and December in 2003. BC values were found to be comparatively less during wet season (July-August; especially august), which could be associated with the rainout and washout associated with the Changma season (summer monsoon). Optical Properties of Aerosols and Clouds (OPAC) model in combination with a <span class="hlt">radiative</span> transfer model (SBDART) were used to estimate aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> separately for composite aerosols (total aerosols) and solely for BC aerosols using chemical composition data sets of Total Suspended Particulates (TSP) and BC. The atmospheric <span class="hlt">forcing</span> for composite aerosols found to be +14.9 to +25.9 W m-2 during spring, +13.4 to +20.4 W m-2 in summer, +12.9 to +19.1 W m-2 in autumn and +16 to +18.2 W m-2 during winter,respectively. The respective BC atmospheric <span class="hlt">forcings</span> were +8.1 to +11.8 W m-2, +8.4 to +11.1 W m-2, +8.7 to +11.4 W m-2 and +8.8 to +11.7 W m-2 during spring, summer, autumn and winter. The study suggests that BC induced atmospheric <span class="hlt">forcing</span> can contribute up to 88% of total aerosol induced atmospheric warming.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C24A..08P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C24A..08P"><span id="translatedtitle">Global mountain snow and ice loss driven by dust and black carbon <span class="hlt">radiative</span> <span class="hlt">forcing</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Painter, T. H.</p> <p>2014-12-01</p> <p>Changes in mountain snow and glaciers have been our strongest indicators of the effects of changing climate. Earlier melt of snow and losses of glacier mass have perturbed regional water cycling, regional climate, and ecosystem dynamics, and contributed strongly to sea level rise. Recent studies however have revealed that in some regions, the reduction of albedo by light absorbing impurities in snow and ice such as dust and black carbon can be distinctly more powerful than regional warming at melting snow and ice. In the Rocky Mountains, dust deposition has increased 5 to 7 fold in the last 150 years, leading to ~3 weeks earlier loss of snow cover from <span class="hlt">forced</span> melt. In absolute terms, in some years dust <span class="hlt">radiative</span> <span class="hlt">forcing</span> there can shorten snow cover duration by nearly two months. Remote sensing retrievals are beginning to reveal powerful dust and black carbon <span class="hlt">radiative</span> <span class="hlt">forcing</span> in the Hindu Kush through Himalaya. In light of recent ice cores that show pronounced increases in loading of dust and BC during the Anthropocene, these <span class="hlt">forcings</span> may have contributed far more to glacier retreat than previously thought. For example, we have shown that the paradoxical end of the Little Ice Age in the European Alps beginning around 1850 (when glaciers began to retreat but temperatures continued to decline and precipitation was unchanged) very likely was driven by the massive increases in deposition to snow and ice of black carbon from industrialization in surrounding nations. A more robust understanding of changes in mountain snow and ice during the Anthropocene requires that we move past simplistic treatments (e.g. temperature-index modeling) to energy balance approaches that assess changes in the individual <span class="hlt">forcings</span> such as the most powerful component for melt - net solar <span class="hlt">radiation</span>. Remote sensing retrievals from imaging spectrometers and multispectral sensors are giving us more powerful insights into the time-space variation of snow and ice albedo.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4760792','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4760792"><span id="translatedtitle">Near-linear response of mean monsoon strength to a broad range of <span class="hlt">radiative</span> <span class="hlt">forcings</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Boos, William R.; Storelvmo, Trude</p> <p>2016-01-01</p> <p>Theoretical models have been used to argue that seasonal mean monsoons will shift abruptly and discontinuously from wet to dry stable states as their <span class="hlt">radiative</span> <span class="hlt">forcings</span> pass a critical threshold, sometimes referred to as a “tipping point.” Further support for a strongly nonlinear response of monsoons to <span class="hlt">radiative</span> <span class="hlt">forcings</span> is found in the seasonal onset of the South Asian summer monsoon, which is abrupt compared with the annual cycle of insolation. Here it is shown that the seasonal mean strength of monsoons instead exhibits a nearly linear dependence on a wide range of <span class="hlt">radiative</span> <span class="hlt">forcings</span>. First, a previous theory that predicted a discontinuous, threshold response is shown to omit a dominant stabilizing term in the equations of motion; a corrected theory predicts a continuous and nearly linear response of seasonal mean monsoon strength to <span class="hlt">forcings</span>. A comprehensive global climate model is then used to show that the seasonal mean South Asian monsoon exhibits a near-linear dependence on a wide range of isolated greenhouse gas, aerosol, and surface albedo <span class="hlt">forcings</span>. This model reproduces the observed abrupt seasonal onset of the South Asian monsoon but produces a near-linear response of the mean monsoon by changing the duration of the summer circulation and the latitude of that circulation’s ascent branch. Thus, neither a physically correct theoretical model nor a comprehensive climate model support the idea that seasonal mean monsoons will undergo abrupt, nonlinear shifts in response to changes in greenhouse gas concentrations, aerosol emissions, or land surface albedo. PMID:26811462</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993JaJAP..32.2369T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993JaJAP..32.2369T"><span id="translatedtitle">Coriolis <span class="hlt">Force</span> Mass-Flow Meter Composed of a Straight Pipe and an <span class="hlt">Additional</span> Resonance-Vibrator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tsutsui, Hirohide; Tomikawa, Yoshiro</p> <p>1993-05-01</p> <p>This paper deals with a new construction for a mass-flow meter using Coriolis <span class="hlt">force</span>, and its basic experimental results. Some Coriolis <span class="hlt">force</span> mass-flow meters, proposed up to now, are of a twin construction of, for example, a U-type pipe or a straight-type pipe, where the mass-flow is determined by measuring the relative displacement between the pipes. Therefore, their structure is too complex. To improve this situation, the authors propose a new mass-flow meter using one straight pipe, together with an <span class="hlt">additional</span> flexural resonance-vibrator. The experimental results prove that a mass-flow meter can be realized by such a simple construction as dealt with here.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PMB....57.1263A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PMB....57.1263A"><span id="translatedtitle">Loss tangent and complex modulus estimated by acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> creep and shear wave dispersion</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Amador, Carolina; Urban, Matthew W.; Chen, Shigao; Greenleaf, James F.</p> <p>2012-03-01</p> <p>Elasticity imaging methods have been used to study tissue mechanical properties and have demonstrated that tissue elasticity changes with disease state. In current shear wave elasticity imaging methods typically only shear wave speed is measured and rheological models, e.g. Kelvin-Voigt, Maxwell and Standard Linear Solid, are used to solve for tissue mechanical properties such as the shear viscoelastic complex modulus. This paper presents a method to quantify viscoelastic material properties in a model-independent way by estimating the complex shear elastic modulus over a wide frequency range using time-dependent creep response induced by acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>. This <span class="hlt">radiation</span> <span class="hlt">force</span> induced creep method uses a conversion formula that is the analytic solution of a constitutive equation. The proposed method in combination with shearwave dispersion ultrasound vibrometry is used to measure the complex modulus so that knowledge of the applied <span class="hlt">radiation</span> <span class="hlt">force</span> magnitude is not necessary. The conversion formula is shown to be sensitive to sampling frequency and the first reliable measure in time according to numerical simulations using the Kelvin-Voigt model creep strain and compliance. Representative model-free shear complex moduli from homogeneous tissue mimicking phantoms and one excised swine kidney were obtained. This work proposes a novel model-free ultrasound-based elasticity method that does not require a rheological model with associated fitting requirements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1092654','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1092654"><span id="translatedtitle">Scenarios of Future Socio-Economics, Energy, Land Use, and <span class="hlt">Radiative</span> <span class="hlt">Forcing</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Eom, Jiyong; Moss, Richard H.; Edmonds, James A.; Calvin, Katherine V.; Clarke, Leon E.; Dooley, James J.; Kim, Son H.; Kopp, Roberrt; Kyle, G. Page; Luckow, Patrick W.; Patel, Pralit L.; Thomson, Allison M.; Wise, Marshall A.; Zhou, Yuyu</p> <p>2013-04-13</p> <p>This chapter explores uncertainty in future scenarios of energy, land use, emissions and <span class="hlt">radiative</span> <span class="hlt">forcing</span> that span the range in the literature for <span class="hlt">radiative</span> <span class="hlt">forcing</span>, but also consider uncertainty in two other dimensions, challenges to mitigation and challenges to adaptation. We develop a set of six scenarios that we explore in detail including the underlying the context in which they are set, assumptions that drive the scenarios, the Global Change Assessment Model (GCAM), used to produce quantified implications for those assumptions, and results for the global energy and land-use systems as well as emissions, concentrations and <span class="hlt">radiative</span> <span class="hlt">forcing</span>. We also describe the history of scenario development and the present state of development of this branch of climate change research. We discuss the implications of alternative social, economic, demographic, and technology development possibilities, as well as potential stabilization regimes for the supply of and demand for energy, the choice of energy technologies, and prices of energy and agricultural commodities. Land use and land cover will also be discussed with the emphasis on the interaction between the demand for bioenergy and crops, crop yields, crop prices, and policy settings to limit greenhouse gas emissions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/945697','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/945697"><span id="translatedtitle">Adjustable virtual pore-size filter for automated sample preparation using acoustic <span class="hlt">radiation</span> <span class="hlt">force</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jung, B; Fisher, K; Ness, K; Rose, K; Mariella, R</p> <p>2008-05-22</p> <p>We present a rapid and robust size-based separation method for high throughput microfluidic devices using acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>. We developed a finite element modeling tool to predict the two-dimensional acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> field perpendicular to the flow direction in microfluidic devices. Here we compare the results from this model with experimental parametric studies including variations of the PZT driving frequencies and voltages as well as various particle sizes and compressidensities. These experimental parametric studies also provide insight into the development of an adjustable 'virtual' pore-size filter as well as optimal operating conditions for various microparticle sizes. We demonstrated the separation of Saccharomyces cerevisiae and MS2 bacteriophage using acoustic focusing. The acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> did not affect the MS2 viruses, and their concentration profile remained unchanged. With optimized design of our microfluidic flow system we were able to achieve yields of > 90% for the MS2 with > 80% of the S. cerevisiae being removed in this continuous-flow sample preparation device.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/22345425','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/22345425"><span id="translatedtitle">Loss tangent and complex modulus estimated by acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> creep and shear wave dispersion.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Amador, Carolina; Urban, Matthew W; Chen, Shigao; Greenleaf, James F</p> <p>2012-03-01</p> <p>Elasticity imaging methods have been used to study tissue mechanical properties and have demonstrated that tissue elasticity changes with disease state. In current shear wave elasticity imaging methods typically only shear wave speed is measured and rheological models, e.g. Kelvin-Voigt, Maxwell and Standard Linear Solid, are used to solve for tissue mechanical properties such as the shear viscoelastic complex modulus. This paper presents a method to quantify viscoelastic material properties in a model-independent way by estimating the complex shear elastic modulus over a wide frequency range using time-dependent creep response induced by acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>. This <span class="hlt">radiation</span> <span class="hlt">force</span> induced creep method uses a conversion formula that is the analytic solution of a constitutive equation. The proposed method in combination with shearwave dispersion ultrasound vibrometry is used to measure the complex modulus so that knowledge of the applied <span class="hlt">radiation</span> <span class="hlt">force</span> magnitude is not necessary. The conversion formula is shown to be sensitive to sampling frequency and the first reliable measure in time according to numerical simulations using the Kelvin-Voigt model creep strain and compliance. Representative model-free shear complex moduli from homogeneous tissue mimicking phantoms and one excised swine kidney were obtained. This work proposes a novel model-free ultrasound-based elasticity method that does not require a rheological model with associated fitting requirements. PMID:22345425</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3376913','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3376913"><span id="translatedtitle">Loss tangent and complex modulus estimated by acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> creep and shear wave dispersion</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Amador, Carolina; Urban, Matthew W; Chen, Shigao; Greenleaf, James F</p> <p>2012-01-01</p> <p>Elasticity imaging methods have been used to study tissue mechanical properties and have demonstrated that tissue elasticity changes with disease state. In current shear wave elasticity imaging methods typically only shear wave speed is measured and rheological models, e.g., Kelvin-Voigt, Maxwell and Standard Linear Solid, are used to solve for tissue mechanical properties such as the shear viscoelastic complex modulus. This paper presents a method to quantify viscoelastic material properties in a model-independent way by estimating the complex shear elastic modulus over a wide frequency range using time-dependent creep response induced by acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>. This <span class="hlt">radiation</span> <span class="hlt">force</span> induced creep (RFIC) method uses a conversion formula that is the analytic solution of a constitutive equation. The proposed method in combination with Shearwave Dispersion Ultrasound Vibrometry (SDUV) is used to measure the complex modulus so that knowledge of the applied <span class="hlt">radiation</span> <span class="hlt">force</span> magnitude is not necessary. The conversion formula is shown to be sensitive to sampling frequency and the first reliable measure in time according to numerical simulations using the Kelvin-Voigt model creep strain and compliance. Representative model-free shear complex moduli from homogeneous tissue mimicking phantoms and one excised swine kidney were obtained. This work proposes a novel model-free ultrasound-based elasticity method that does not require a rheological model with associated fitting requirements. PMID:22345425</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25474778','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25474778"><span id="translatedtitle">Toric focusing for <span class="hlt">radiation</span> <span class="hlt">force</span> applications using a toric lens coupled to a spherically focused transducer.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Arnal, Bastien; Nguyen, Thu-Mai; O'Donnell, Matthew</p> <p>2014-12-01</p> <p>Dynamic elastography using <span class="hlt">radiation</span> <span class="hlt">force</span> requires that an ultrasound field be focused during hundreds of microseconds at a pressure of several megapascals. Here, we address the importance of the focal geometry. Although there is usually no control of the elevational focal width in generating a tissue mechanical response, we propose a tunable approach to adapt the focus geometry that can significantly improve <span class="hlt">radiation</span> <span class="hlt">force</span> efficiency. Several thin, in-house-made polydimethylsiloxane lenses were designed to modify the focal spot of a spherical transducer. They exhibited low absorption and the focal spot widths were extended up to 8-fold in the elevation direction. <span class="hlt">Radiation</span> <span class="hlt">force</span> experiments demonstrated an 8-fold increase in tissue displacements using the same pressure level in a tissue-mimicking phantom with a similar shear wave spectrum, meaning it does not affect elastography resolution. Our results demonstrate that larger tissue responses can be obtained for a given pressure level, or that similar response can be reached at a much lower mechanical index (MI). We envision that this work will impact 3-D elastography using 2-D phased arrays, where such shaping can be achieved electronically with the potential for adaptive optimization. PMID:25474778</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/19213633','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/19213633"><span id="translatedtitle">Image quality, tissue heating, and frame rate trade-offs in acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> impulse imaging.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bouchard, Richard R; Dahl, Jeremy J; Hsu, Stephen J; Palmeri, Mark L; Trahey, Gregg E</p> <p>2009-01-01</p> <p>The real-time application of acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> impulse (ARFI) imaging requires both short acquisition times for a single ARFI image and repeated acquisition of these frames. Due to the high energy of pulses required to generate appreciable <span class="hlt">radiation</span> <span class="hlt">force</span>, however, repeated acquisitions could result in substantial transducer face and tissue heating. We describe and evaluate several novel beam sequencing schemes which, along with parallel-receive acquisition, are designed to reduce acquisition time and heating. These techniques reduce the total number of <span class="hlt">radiation</span> <span class="hlt">force</span> impulses needed to generate an image and minimize the time between successive impulses. We present qualitative and quantitative analyses of the trade-offs in image quality resulting from the acquisition schemes. Results indicate that these techniques yield a significant improvement in frame rate with only moderate decreases in image quality. Tissue and transducer face heating resulting from these schemes is assessed through finite element method modeling and thermocouple measurements. Results indicate that heating issues can be mitigated by employing ARFI acquisition sequences that utilize the highest track-to-excitation ratio possible. PMID:19213633</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4408860','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4408860"><span id="translatedtitle">Stratospheric sulfur and its implications for <span class="hlt">radiative</span> <span class="hlt">forcing</span> simulated by the chemistry climate model EMAC</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Brühl, C; Lelieveld, J; Tost, H; Höpfner, M; Glatthor, N</p> <p>2015-01-01</p> <p>Multiyear simulations with the atmospheric chemistry general circulation model EMAC with a microphysical modal aerosol module at high vertical resolution demonstrate that the sulfur gases COS and SO2, the latter from low-latitude and midlatitude volcanic eruptions, predominantly control the formation of stratospheric aerosol. Marine dimethyl sulfide (DMS) and other SO2 sources, including strong anthropogenic emissions in China, are found to play a minor role except in the lowermost stratosphere. Estimates of volcanic SO2 emissions are based on satellite observations using Total Ozone Mapping Spectrometer and Ozone Monitoring Instrument for total injected mass and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat or Stratospheric Aerosol and Gases Experiment for the spatial distribution. The 10 year SO2 and COS data set of MIPAS is also used for model evaluation. The calculated <span class="hlt">radiative</span> <span class="hlt">forcing</span> of stratospheric background aerosol including sulfate from COS and small contributions by DMS oxidation, and organic aerosol from biomass burning, is about 0.07W/m2. For stratospheric sulfate aerosol from medium and small volcanic eruptions between 2005 and 2011 a global <span class="hlt">radiative</span> <span class="hlt">forcing</span> up to 0.2W/m2 is calculated, moderating climate warming, while for the major Pinatubo eruption the simulated <span class="hlt">forcing</span> reaches 5W/m2, leading to temporary climate cooling. The Pinatubo simulation demonstrates the importance of <span class="hlt">radiative</span> feedback on dynamics, e.g., enhanced tropical upwelling, for large volcanic eruptions. PMID:25932352</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMGC41B1096J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMGC41B1096J"><span id="translatedtitle">The Impact of Desert Dust Aerosol <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> on Global and West African Precipitation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jordan, A.; Zaitchik, B. F.; Gnanadesikan, A.; Dezfuli, A. K.</p> <p>2015-12-01</p> <p>Desert dust aerosols exert a <span class="hlt">radiative</span> <span class="hlt">forcing</span> on the atmosphere, influencing atmospheric temperature structure and modifying <span class="hlt">radiative</span> fluxes at the top of the atmosphere (TOA) and surface. As dust aerosols perturb <span class="hlt">radiative</span> 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 <span class="hlt">radiative</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> and climate response affecting West Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..APR.Y7005M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..APR.Y7005M"><span id="translatedtitle"><span class="hlt">Radiation</span>-Reaction <span class="hlt">Force</span> on a Small Charged Body to Second Order</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Moxon, Jordan; Flanagan, Eanna</p> <p>2015-04-01</p> <p>In classical electrodynamics, an accelerating charge emits <span class="hlt">radiation</span> and experiences a corresponding <span class="hlt">radiation</span> reaction <span class="hlt">force</span>, or self <span class="hlt">force</span>. We extend to greater precision (higher order in perturbation theory) a previous rigorous derivation of the electromagnetic self <span class="hlt">force</span> in flat spacetime by Gralla, Harte, and Wald. The method introduced by Gralla, Harte, and Wald computes the self-<span class="hlt">force</span> from the Maxwell field equations and conservation of stress-energy, and does not require regularization of a singular point charge, as has been necessary in prior computations. For our higher order compuation, it becomes necessary to adopt an adjusted definition of the mass of the body to avoid including self-energy from the electromagnetic field sourced during the history of the body. We derive the evolution equations for the mass, spin, and center of mass position of an extended body through second order using our adjusted formalism. The final equations give an acceleration dependent evolution of the spin (self-torque), as well as a mixing between the extended body effects and the acceleration dependent effects on the overall body motion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008PhDT.......418S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008PhDT.......418S"><span id="translatedtitle">Sensitivity of sea-ice cover and ocean properties to wind-stress and <span class="hlt">radiative</span> <span class="hlt">forcings</span> from 1500 to 2000</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sedlacek, Jan</p> <p></p> <p> warming afterwards. The simulated sea-ice area and volume in the Northern Hemisphere were larger during the LIA as compared to the present. The comparison between wind-driven and <span class="hlt">radiatively</span>-driven changes shows that both <span class="hlt">forcings</span> result in equal magnitude changes in the case of ice volume; for ice area, the wind-driven part is twice as large as the <span class="hlt">radiatively</span>-driven part. The simulations suggest that the main <span class="hlt">radiative</span> <span class="hlt">forcing</span> before 1850 was volcanic <span class="hlt">forcing</span>, whereas after 1850 the greenhouse gas changes dominated the <span class="hlt">forcing</span> field. <span class="hlt">Additionally</span>, an increased ice volume export from the Arctic to the North Atlantic has no significant effect on the maximum strength of the Atlantic meridional overturning circulation. In the Southern Hemisphere, no long-term trends are visible in the simulated sea-ice area and volume. The wind-driven changes are about four times larger than the <span class="hlt">radiatively</span>-driven changes. The above mentioned work is extended to several ocean properties. The ocean heat content changes in the upper 300 m from the tropical to mid-latitudes are mainly driven by the changes in <span class="hlt">radiative</span> <span class="hlt">forcing</span>. In the high-latitudes the changes in heat content are wind-driven. In the full ocean (0--3000 m) the wind-stress <span class="hlt">forcing</span> reduces the <span class="hlt">radiatively</span>-driven downward trend prior to 1700. After 1700 no wind-driven effect is visible in the simulations. The ocean temperature changes from the LIA to the industrial era show a <span class="hlt">radiative</span> cooling in the upper 600 m and a dynamical downward transport of cool water to lower depths during the LIA. Changes in salinity are mainly located in the northern high-latitudes. In the surface layers the water was saltier in the Arctic Ocean and fresher in the North Atlantic during the LIA due to increased sea-ice formation and subsequent transport to the south and melting during this period. In the subsurface layers of the Arctic Ocean there was a stronger inflow of saline water during the LIA. The simulated density changes are a composite</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010110721','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010110721"><span id="translatedtitle">A Study of Direct and Cloud-Mediated <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> of Climate Due to Aerosols</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yu, Shao-Cai</p> <p>1999-01-01</p> <p>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 <span class="hlt">radiative</span> <span class="hlt">forcing</span>. 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 <span class="hlt">forcing</span> due to both greenhouse gases and aerosols was completely counteracted by the shortwave aerosol <span class="hlt">forcing</span> 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 <span class="hlt">addition</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21443467','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21443467"><span id="translatedtitle"><span class="hlt">Radiation</span> of nitrogen molecules in a dielectric barrier discharge with small <span class="hlt">additives</span> of chlorine and bromine</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Avtaeva, S. V.; Avdeev, S. M.; Sosnin, E. A.</p> <p>2010-08-15</p> <p>Spectral and energy characteristics of nitrogen molecule <span class="hlt">radiation</span> in dielectric barrier discharges in Ar-N{sub 2}, Ar-N{sub 2}-Cl{sub 2}, and Ar-N{sub 2}-Br{sub 2} mixtures were investigated experimentally. Small <span class="hlt">additives</span> of molecular chlorine or bromine to an Ar-N{sub 2} mixture are found to increase the <span class="hlt">radiation</span> intensity of the second positive system of nitrogen. The conditions at which the <span class="hlt">radiation</span> spectrum predominantly consists of vibronic bands of this system are determined. Using a numerical model of plasmachemical processes, it is shown that, at electron temperatures typical of gas discharges (2-4 eV), a minor <span class="hlt">additive</span> of molecular chlorine to an Ar-N{sub 2} mixture leads to an increase in the concentrations of electrons, positive ions, and metastable argon atoms. In turn, collisional energy transfer from metastable argon atoms to nitrogen molecules results in the excitation of the N{sub 2}(C{sup 3{Pi}}{sub u}) state.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.A41A0019K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.A41A0019K"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">Forcing</span> at the Surface by Clouds, Aerosols, and Water Vapor Over Tropical Oceans</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Key, E.; Minnett, P.; Szczodrak, G.; Caniaux, G.; Voss, K.; Bourras, D.</p> <p>2007-12-01</p> <p>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 <span class="hlt">radiative</span> <span class="hlt">forcing</span>, 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 <span class="hlt">radiative</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> of clouds, aerosols, and water vapor on the sea surface skin temperature, towards the improvement of current diurnal warming models, which simplify atmospheric <span class="hlt">radiative</span> effects into a general cloud parameter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..MARH35011W&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016APS..MARH35011W&link_type=ABSTRACT"><span id="translatedtitle">A new model for biological effects of <span class="hlt">radiation</span> and the driven <span class="hlt">force</span> of molecular evolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wada, Takahiro; Manabe, Yuichiro; Nakajima, Hiroo; Tsunoyama, Yuichi; Bando, Masako</p> <p></p> <p>We proposed a new mathematical model to estimate biological effects of <span class="hlt">radiation</span>, which we call Whack-A-Mole (WAM) model. A special feature of WAM model is that it involves the dose rate of <span class="hlt">radiation</span> as a key ingredient. We succeeded to reproduce the experimental data of various species concerning the <span class="hlt">radiation</span> induced mutation frequencies. From the analysis of the mega-mouse experiments, we obtained the mutation rate per base-pair per year for mice which is consistent with the so-called molecular clock in evolution genetics, 10-9 mutation/base-pair/year. Another important quantity is the equivalent dose rate for the whole spontaneous mutation, deff. The value of deff for mice is 1.1*10-3 Gy/hour which is much larger than the dose rate of natural <span class="hlt">radiation</span> (10- (6 - 7) Gy/hour) by several orders of magnitude. We also analyzed Drosophila data and obtained essentially the same numbers. This clearly indicates that the natural <span class="hlt">radiation</span> is not the dominant driving <span class="hlt">force</span> of the molecular evolution, but we should look for other factors, such as miscopy of DNA in duplication process. We believe this is the first quantitative proof of the small contribution of the natural <span class="hlt">radiation</span> in the molecular evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23861919','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23861919"><span id="translatedtitle">In vivo study of transverse carpal ligament stiffness using acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> impulse (ARFI) imaging.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shen, Zhilei Liu; Vince, D Geoffrey; Li, Zong-Ming</p> <p>2013-01-01</p> <p>The transverse carpal ligament (TCL) forms the volar boundary of the carpal tunnel and may provide mechanical constraint to the median nerve, leading to carpal tunnel syndrome. Therefore, the mechanical properties of the TCL are essential to better understand the etiology of carpal tunnel syndrome. The purpose of this study was to investigate the in vivo TCL stiffness using acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> impulse (ARFI) imaging. The shear wave velocity (SWV) of the TCL was measured using Virtual Touch IQ(TM) software in 15 healthy, male subjects. The skin and the thenar muscles were also examined as reference tissues. In <span class="hlt">addition</span>, the effects of measurement location and ultrasound transducer compression on the SWV were studied. The SWV of the TCL was dependent on the tissue location, with greater SWV values within the muscle-attached region than those outside of the muscle-attached region. The SWV of the TCL was significantly smaller without compression (5.21 ± 1.08 m/s) than with compression (6.62 ± 1.18 m/s). The SWV measurements of the skin and the thenar muscles were also affected by transducer compression, but to different extents than the SWV of the TCL. Therefore to standardize the ARFI imaging procedure, it is recommended that a layer of ultrasound gel be maintained to minimize the effects of tissue compression. This study demonstrated the feasibility of ARFI imaging for assessing the stiffness characteristics of the TCL in vivo, which has the potential to identify pathomechanical changes of the tissue. PMID:23861919</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26426636','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26426636"><span id="translatedtitle">Acoustic <span class="hlt">Radiation</span> <span class="hlt">Force</span> Impulse Measurement in Renal Transplantation: A Prospective, Longitudinal Study With Protocol Biopsies.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Juhan; Oh, Young Taik; Joo, Dong Jin; Ma, Bo Gyoung; Lee, A-lan; Lee, Jae Geun; Song, Seung Hwan; Kim, Seung Up; Jung, Dae Chul; Chung, Yong Eun; Kim, Yu Seun</p> <p>2015-09-01</p> <p>Interstitial fibrosis and tubular atrophy (IF/TA) is a common cause of kidney allograft loss. Several noninvasive techniques developed to assess tissue fibrosis are widely used to examine the liver. However, relatively few studies have investigated the use of elastographic methods to assess transplanted kidneys. The aim of this study was to explore the clinical implications of the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> impulse (ARFI) technique in renal transplant patients. A total of 91 patients who underwent living donor renal transplantation between September 2010 and January 2013 were included in this prospective study. Shear wave velocity (SWV) was measured by ARFI at baseline and predetermined time points (1 week and 6 and 12 months after transplantation). Protocol biopsies were performed at 12 months. Instead of reflecting IF/TA, SWVs were found to be related to time elapsed after transplantation. Mean SWV increased continuously during the first postoperative year (P < 0.001). In <span class="hlt">addition</span>, mixed model analysis showed no correlation existed between SWV and serum creatinine (r = -0.2426, P = 0.0771). There was also no evidence of a relationship between IF/TA and serum creatinine (odds ratio [OR] = 1.220, P = 0.7648). Furthermore, SWV temporal patterns were dependent on the kidney weight to body weight ratio (KW/BW). In patients with a KW/BW < 3.5 g/kg, mean SWV continuously increased for 12 months, whereas it decreased after 6 months in those with a KW/BW ≥ 3.5 g/kg.No significant correlation was observed between SWV and IF/TA or renal dysfunction. However, SWV was found to be related to the time after transplantation. Renal hemodynamics influenced by KW/BW might impact SWV values. PMID:26426636</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4176895','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4176895"><span id="translatedtitle">Acoustic <span class="hlt">Radiation</span> <span class="hlt">Force</span> Impulse Imaging (ARFI) on an IVUS Circular Array</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Patel, Vivek; Dahl, Jeremy; Bradway, David; Doherty, Joshua; Lee, Seung Yun; Smith, Stephen</p> <p>2014-01-01</p> <p>Our long-term goal is the detection and characterization of vulnerable plaque in the coronary arteries of the heart using IVUS catheters. Vulnerable plaque, characterized by a thin fibrous cap and a soft, lipid-rich, necrotic core is a pre-cursor to heart attack and stroke. Early detection of such plaques may potentially alter the course of treatment of the patient in order to prevent ischemic events. We have previously described the characterization of carotid plaques using external linear arrays operating at 9 MHz. In <span class="hlt">addition</span>, we previously modified circular array IVUS catheters by short-circuiting several neighboring elements to produce fixed beam-widths for intra-vascular hyperthermia applications. In this paper we modified Volcano Visions 8.2 French, 9 MHz catheters and Volcano Platinum 3.5 French, 20 MHz catheters by short circuiting portions of the array for ARFI applications. The catheters had an effective transmit aperture size of 2 mm and 1.5 mm respectively. The catheters were connected to a Verasonics scanner and driven with pushing pulses of 180 V p-p to acquire ARFI data from a soft gel phantom with a Young’s modulus of 2.9 kPa. The dynamic response of the tissue-mimicking material demonstrates a typical ARFI motion of 1–2 microns as the gel phantom displaces away and recovers back to its normal position. The hardware modifications applied to our IVUS catheters mimic potential beamforming modifications that could be implemented on IVUS scanners. Our results demonstrate that the generation of <span class="hlt">radiation</span> <span class="hlt">force</span> from IVUS catheters and the development of intra-vascular ARFI may be feasible. PMID:24554291</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AtmEn.104...69S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015AtmEn.104...69S&link_type=ABSTRACT"><span id="translatedtitle">Variation of <span class="hlt">radiative</span> <span class="hlt">forcings</span> and global warming potentials from regional aviation NOx emissions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Skowron, Agnieszka; Lee, David S.; De León, Ruben R.</p> <p>2015-03-01</p> <p>The response to hemispherical and regional aircraft NOx emissions is explored by using two climate metrics: <span class="hlt">radiative</span> <span class="hlt">forcing</span> (RF) and Global Warming Potential (GWP). The global chemistry transport model, MOZART-3 CTM, is applied in this study for a series of incremental aircraft NOx emission integrations to different regions. It was found that the sensitivity of chemical responses per unit emission rate from regional aircraft NOx emissions varies with size of aircraft NOx emission rate and that climate metric values decrease with increasing aircraft NOx emission rates, except for Southeast Asia. Previous work has recognized that aircraft NOx GWPs may vary regionally. However, the way in which these regional GWPs are calculated are critical. Previous studies have added a fixed amount of NOx to different regions. This approach can heavily bias the results of a regional GWP because of the well-established sensitivity of O3 production to background NOx whereby the Ozone Production Efficiency (OPE) is greater at small background NOx. Thus, even a small <span class="hlt">addition</span> of NOx in a clean-air area can produce a large O3 response. Using this 'fixed <span class="hlt">addition</span>' method of 0.035 Tg(N) yr-1, results in the greatest effect observed for North Atlantic and Brazil, ∼10.0 mW m-2/Tg(N) yr-1. An alternative 'proportional approach' is also taken that preserves the subtle balance of local NOx-O3-CH4 systems with the existing emission patterns of aircraft and background NOx, whereby a proportional amount of aircraft NOx, 5% (N) yr-1, is added to each region in order to determine the response. This results in the greatest effect observed for North Pacific that with its net NOx RF of 23.7 mW m-2/Tg(N) yr-1 is in contrast with the 'fixed <span class="hlt">addition</span>' method. For determining regional NOx GWPs, it is argued that the 'proportional' approach gives more representative results. However, a constraint of both approaches is that the regional GWP determined is dependent on the relative global emission pattern</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/22351352','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/22351352"><span id="translatedtitle">The outflows accelerated by the magnetic fields and <span class="hlt">radiation</span> <span class="hlt">force</span> of accretion disks</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Cao, Xinwu</p> <p>2014-03-01</p> <p>The inner region of a luminous accretion disk is <span class="hlt">radiation</span>-pressure-dominated. We estimate the surface temperature of a <span class="hlt">radiation</span>-pressure-dominated accretion disk, Θ=c{sub s}{sup 2}/r{sup 2}Ω{sub K}{sup 2}≪(H/r){sup 2}, which is significantly lower than that of a gas-pressure-dominated disk, Θ ∼ (H/r){sup 2}. This means that the outflow can be launched magnetically from the photosphere of the <span class="hlt">radiation</span>-pressure-dominated disk only if the effective potential barrier along the magnetic field line is extremely shallow or no potential barrier is present. For the latter case, the slow sonic point in the outflow will probably be in the disk, which leads to a slow circular dense flow above the disk. This implies that hot gas (probably in the corona) is necessary for launching an outflow from the <span class="hlt">radiation</span>-pressure-dominated disk, which provides a natural explanation for the observational evidence that the relativistic jets are related to hot plasma in some X-ray binaries and active galactic nuclei. We investigate the outflows accelerated from the hot corona above the disk by the magnetic field and <span class="hlt">radiation</span> <span class="hlt">force</span> of the accretion disk. We find that with the help of the <span class="hlt">radiation</span> <span class="hlt">force</span>, the mass loss rate in the outflow is high, which leads to a slow outflow. This may be why the jets in radio-loud narrow-line Seyfert galaxies are in general mildly relativistic compared with those in blazars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/963770','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/963770"><span id="translatedtitle">Lessons Learned at the Idaho National Laboratory for the Entry into <span class="hlt">Force</span> of the U.S. <span class="hlt">Additional</span> Protocol</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jeffrey C. Joe; Shauna A. Hoiland</p> <p>2009-07-01</p> <p>For a number of years, the Idaho National Laboratory (INL) has been preparing for the entry into <span class="hlt">force</span> of the U.S. <span class="hlt">Additional</span> Protocol (AP). These preparations included attending training, participating in tabletop exercises, preparing draft declarations, developing INL-specific guidance documents, preparing for and hosting a mock complementary access visit, and preparing declarations for official submittal. All of these activities, the training materials, and software developed by other U.S. DOE national laboratories (PNNL, ORNL, LANL, and BNL) were very helpful in preparing for the entry into <span class="hlt">force</span> of the AP. As with any endeavor of this size and complexity, however, there are always instances where even the best preparations and advanced planning do not anticipate every challenge. As the DOE's lead nuclear energy research and development facility, the INL faced many unique challenges. The majority of research conducted at the INL is nuclear fuel cycle related, most of which is not protected by the National Security Exclusion. This paper describes the lessons learned from the INL’s experience of preparing for the entry into <span class="hlt">force</span> of the AP, specifically how translating and implementing general principles into actual activities proved to be one of many challenges, and provides general suggestions on how to respond effectively and efficiently to routine annual data calls and other AP requests.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PNAS..113.5820L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PNAS..113.5820L"><span id="translatedtitle">On the relationship between aerosol model uncertainty and <span class="hlt">radiative</span> <span class="hlt">forcing</span> uncertainty</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Lindsay A.; Reddington, Carly L.; Carslaw, Kenneth S.</p> <p>2016-05-01</p> <p>The largest uncertainty in the historical <span class="hlt">radiative</span> <span class="hlt">forcing</span> of climate is caused by the interaction of aerosols with clouds. Historical <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span>. 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 <span class="hlt">forcing</span> 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 <span class="hlt">forcings</span>. 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26848136','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26848136"><span id="translatedtitle">On the relationship between aerosol model uncertainty and <span class="hlt">radiative</span> <span class="hlt">forcing</span> uncertainty.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lee, Lindsay A; Reddington, Carly L; Carslaw, Kenneth S</p> <p>2016-05-24</p> <p>The largest uncertainty in the historical <span class="hlt">radiative</span> <span class="hlt">forcing</span> of climate is caused by the interaction of aerosols with clouds. Historical <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span>. 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 <span class="hlt">forcing</span> 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 <span class="hlt">forcings</span>. 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRD..11613112F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRD..11613112F"><span id="translatedtitle">Response of Earth's surface temperature to <span class="hlt">radiative</span> <span class="hlt">forcing</span> over A.D. 1-2009</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Friend, A. D.</p> <p>2011-07-01</p> <p>An energy balance model (EBM) of the annual global mean surface temperature is described and calibrated to the sensitivity and temporal dynamics of the Goddard Institute for Space Studies modelE global climate model (GCM). The effective <span class="hlt">radiative</span> <span class="hlt">forcings</span> of 10 agents are estimated over the past 2009 years and used as inputs to the model. Temperatures are relatively stable from around A.D. 300 until a "Medieval Climate Anomaly" starting around A.D. 1050. This is ended by a massive volcanic eruption in A.D. 1258, which initiates a multicentury era of low and relatively variable global mean temperatures, including a "Little Ice Age" A.D. 1588-1720. This era only ends at the beginning of the 20th century. The model estimate of <span class="hlt">forced</span> centennial variability is smaller than the observed variability in reconstructions over the past two millennia. Also, the default parameterization results in less warming than observed over A.D. 1910-1944. Prediction uncertainty in the pre-industrial era is dominated by solar <span class="hlt">forcing</span>, with the climate feedback factor and volcanic aerosols also playing important roles. In contrast, prediction uncertainty post-A.D. 1750 is much higher and dominated by uncertainties in direct and indirect aerosol and land use <span class="hlt">forcings</span>. Improving estimates of these will greatly increase our ability to attribute observed temperature variability to contemporary <span class="hlt">forcings</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4889342','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4889342"><span id="translatedtitle">On the relationship between aerosol model uncertainty and <span class="hlt">radiative</span> <span class="hlt">forcing</span> uncertainty</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Reddington, Carly L.; Carslaw, Kenneth S.</p> <p>2016-01-01</p> <p>The largest uncertainty in the historical <span class="hlt">radiative</span> <span class="hlt">forcing</span> of climate is caused by the interaction of aerosols with clouds. Historical <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span>. 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 <span class="hlt">forcing</span> 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 <span class="hlt">forcings</span>. 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/21097176','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/21097176"><span id="translatedtitle">A new apparatus for analysis of viscoelastic fluids by ultrasound <span class="hlt">radiation</span> <span class="hlt">force</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Almeida, Thiago W J; Kamimura, Hermes A S; Carneiro, Antonio A O</p> <p>2010-01-01</p> <p>The acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> has been used as the method to examine the physical properties of materials in several areas. Vibro-acoustography is an acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> technique that is being used to perform analysis of mechanical properties of materials. In this application a focused acoustic modulated <span class="hlt">force</span> excites target which vibrates at the frequency of modulation. The emitted sound is characteristic of the medium mechanical impedance and it is measured using a dedicated hydrophone. In this paper, we propose a modification of the vibro-acoustography (VAG) technique and apply a technique called vibro-acustomagnetography (VAMG) by replacing the hydrophone by a magnetic sensor with high sensitivity. In this case, the modulated acoustic <span class="hlt">radiation</span> will be applied on a magnetized target immersed in the fluid under study. With this procedure, static and dynamic displacement of the magnetic target (ball) will be measured when acoustically excited. In this study, we used a magnetoresistive sensor with resolution of about nT for mounting the transducer to detect displacement of the magnetic target. The vibration of the target was induced by a non-contact <span class="hlt">force</span>, using an ultrasonic beam modulated by two concentric beams generated by confocal piezoelectric elements with equal area and common focus to 7 cm. The target used was a magnetic sphere of NdFeB with a radius of 2.36 mm. The apparatus was evaluated through of measurements in water and oil. Viscoelastic parameters were estimated fitting the nonlinear response of the magnetic transducer function of frequency modulation. PMID:21097176</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/26448531','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/26448531"><span id="translatedtitle">Numerical simulation of acoustofluidic manipulation by <span class="hlt">radiation</span> <span class="hlt">forces</span> and acoustic streaming for complex particles.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hahn, Philipp; Leibacher, Ivo; Baasch, Thierry; Dual, Jurg</p> <p>2015-11-21</p> <p>The numerical prediction of acoustofluidic particle motion is of great help for the design, the analysis, and the physical understanding of acoustofluidic devices as it allows for a simple and direct comparison with experimental observations. However, such a numerical setup requires detailed modeling of the acoustofluidic device with all its components and thorough understanding of the acoustofluidic <span class="hlt">forces</span> inducing the particle motion. In this work, we present a 3D trajectory simulation setup that covers the full spectrum, comprising a time-harmonic device model, an acoustic streaming model of the fluid cavity, a <span class="hlt">radiation</span> <span class="hlt">force</span> simulation, and the calculation of the hydrodynamic drag. In order to make quantitatively accurate predictions of the device vibration and the acoustic field, we include the viscous boundary layer damping. Using a semi-analytical method based on Nyborg's calculations, the boundary-driven acoustic streaming is derived directly from the device simulation and takes into account cavity wall vibrations which have often been neglected in the literature. The acoustic <span class="hlt">radiation</span> <span class="hlt">forces</span> and the hydrodynamic drag are calculated numerically to handle particles of arbitrary shape, structure, and size. In this way, complex 3D particle translation and rotation inside experimental microdevices can be predicted. We simulate the rotation of a microfiber in an amplitude-modulated 2D field and analyze the results with respect to experimental observations. For a quantitative verification, the motion of an alumina microdisk is compared to a simple experiment. Demonstrating the potential of the simulation setup, we compute the trajectory of a red blood cell inside a realistic microdevice under the simultaneous effects of acoustic streaming and <span class="hlt">radiation</span> <span class="hlt">forces</span>. PMID:26448531</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19990100663','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19990100663"><span id="translatedtitle">Determination of <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> of Saharan Dust using Combined TOMS and ERBE Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hsu, N. Christina; Herman, Jay R.; Weaver, Clark</p> <p>1999-01-01</p> <p>The direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> of Saharan dust aerosols has been determined by combining aerosol information derived from Nimbus-7 TOMS with <span class="hlt">radiation</span> measurements observed at the top of atmosphere (TOA) by NOAA-9 ERBE made during February-July 1985. Cloud parameters and precipitable water derived from the NOAA-9 HIRS2 instrument were used to aid in screening for clouds and water vapor in the analyses. Our results indicate that under "cloud-free" and "dry" conditions there is a good correlation between the ERBE TOA outgoing longwave fluxes and the TOMS aerosol index measurements over both land and ocean in areas under the influence of airborne Saharan dust. The ERBE TOA outgoing shortwave fluxes were also found to correlate well with the dust loading derived from TOMS over ocean. However, the calculated shortwave <span class="hlt">forcing</span> of Saharan dust aerosols is very weak and noisy over land for the range of solar zenith angle viewed by the NOAA-9 ERBE in 1985. Sensitivity factors of the TOA outgoing fluxes to changes in aerosol index were estimated using a linear regression fit to the ERBE and TOMS measurements. The ratio of the shortwave-to-longwave response to changes in dust loading over the ocean is found to be roughly 2 to 3, but opposite in sign. The monthly averaged "clear-sky" TOA direct <span class="hlt">forcing</span> of airborne Saharan dust was also calculated by multiplying these sensitivity factors by the TOMS monthly averaged "clear-sky" aerosol index. Both the observational and theoretical analyses indicate that the dust layer height, ambient moisture content as well as the presence of cloud all play an important role in determining the TOA direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> due to mineral aerosols.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9640E..0JB','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9640E..0JB"><span id="translatedtitle">Estimation of aerosol direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> in Lecce during the 2013 ADRIMED campaign</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barragan, Ruben; Romano, Salvatore; Sicard, Michaël.; Burlizzi, Pasquale; Perrone, Maria-Rita; Comeron, Adolfo</p> <p>2015-10-01</p> <p>In the framework of the ChArMEx (Chemistry-Aerosol Mediterranean Experiment, http://charmex.lsce.ipsl.fr/) initiative, a field campaign took place in the western Mediterranean Basin between 10 June and 5 July 2013 within the ADRIMED (Aerosol Direct <span class="hlt">Radiative</span> Impact on the regional climate in the MEDiterranean region) project. The scientific objectives of ADRIMED are the characterization of the typical "Mediterranean aerosol" and its direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> (column closure and regional scale). This work is focused on the multi-intrusion Saharan dust transport period of moderate intensity that occurred over the western and central Mediterranean Basin during the period 14 - 27 June. The dust plumes were detected by the EARLINET/ACTRIS (European Aerosol Research Lidar Network / Aerosols, Clouds, and Trace gases Research InfraStructure Network, http://www.actris.net/) lidar stations of Barcelona (16 and 17 June) and Lecce (22 June). First, two well-known and robust <span class="hlt">radiative</span> transfer models, parametrized by lidar profiles for the aerosol vertical distribution, are validated both in the shortwave and longwave spectral range 1) at the surface with down- and up-ward flux measurements from radiometers and 2) at the top of the atmosphere with upward flux measurements from the CERES (Clouds and the Earth's Radiant Energy System) radiometers on board the AQUA and TERRA satellites. The differences between models and their limitations are discussed. The instantaneous and clear-sky direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> of mineral dust is then estimated using lidar data for parametrizing the particle vertical distribution at Lecce. The difference between the obtained <span class="hlt">forcings</span> is discussed in regard to the mineralogy and vertical structure of the dust plume.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.A53F0324B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.A53F0324B"><span id="translatedtitle">Satellite observational constraints on ozone <span class="hlt">radiative</span> <span class="hlt">forcing</span> in chemistry-climate models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bowman, K. W.; Aghedo, A. M.; Worden, H. M.; Kulawik, S. S.; Shindell, D. T.; Lamarque, J.; Faluvegi, G.; Parrington, M.; Jones, D. B.; Rast, S.; Naik, V.; Horowitz, L. W.</p> <p>2010-12-01</p> <p>Tropospheric ozone <span class="hlt">radiative</span> <span class="hlt">forcing</span> is primarily driven by longwave absorption, and its accurate estimation is contingent on the ability of models to simulate the spatial and vertical distribution of ozone within the entire troposphere. Based on model calculations, the fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC AR4) estimated tropospheric ozone <span class="hlt">radiative</span> <span class="hlt">forcing</span> as 0.35 Wm-2 (with a multi-model spread of 0.25 - 0.65 Wm-2), making the greenhouse effect of tropospheric ozone the third largest following carbon dioxide and methane. However since the IPCC second assessment report, the estimate has not changed substantially and the uncertainties have slightly increased. We demonstrate the application of Tropospheric Emission Spectrometer (TES) all-sky instantaneous <span class="hlt">radiative</span> <span class="hlt">forcing</span> (IRF) kernels as a new and unique way for an observationally constrained evaluation of ozone calculated by models. These IRF kernels are the changes in the top-of-the-atmosphere <span class="hlt">radiative</span> flux due to vertical and spatial distribution of ozone. The discrepancies between TES and five state-of-the-art chemistry climate models, which are AM2-Chem, AM3-Chem, CAM-Chem, ECHAM5-MOZ and GISS-PUCCINI in August 2006 resulted in tropospheric IRF biases from -0.4 to +0.7 W/m2 over large regions within the tropics and mid-latitudes, due to ozone differences over the region in the lower and middle troposphere, enhanced by persistent bias in the upper- troposphere lower-stratospheric region. The zonal mean IRF biases also range from -30 to +40 milli-Watts/m2 for the models with an ensemble mean total tropospheric IRF bias of less than 0.2 W/m2 within the entire troposphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20070020527&hterms=estimated&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Destimated','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20070020527&hterms=estimated&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Destimated"><span id="translatedtitle">Multidecadal Changes in Near-Global Cloud Cover and Estimated Cloud Cover <span class="hlt">Radiative</span> <span class="hlt">Forcing</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Norris, Joel</p> <p>2005-01-01</p> <p>The first paper was Multidecadal changes in near-global cloud cover and estimated cloud cover <span class="hlt">radiative</span> <span class="hlt">forcing</span>, by J. R. Norris (2005, J. Geophys. Res. - Atmos., 110, D08206, doi: lO.l029/2004JD005600). This study examined variability in zonal mean surface-observed upper-level (combined midlevel and high-level) and low-level cloud cover over land during 1971-1 996 and over ocean during 1952-1997. These data were averaged from individual synoptic reports in the Extended Edited Cloud Report Archive (EECRA). Although substantial interdecadal variability is present in the time series, long-term decreases in upper-level cloud cover occur over land and ocean at low and middle latitudes in both hemispheres. Near-global upper-level cloud cover declined by 1.5%-sky-cover over land between 1971 and 1996 and by 1.3%-sky-cover over ocean between 1952 and 1997. Consistency between EECRA upper-level cloud cover anomalies and those from the International Satellite Cloud Climatology Project (ISCCP) during 1984-1 997 suggests the surface-observed trends are real. The reduction in surface-observed upper-level cloud cover between the 1980s and 1990s is also consistent with the decadal increase in all-sky outgoing longwave <span class="hlt">radiation</span> reported by the Earth <span class="hlt">Radiation</span> Budget Satellite (EMS). Discrepancies occur between time series of EECRA and ISCCP low-level cloud cover due to identified and probable artifacts in satellite and surface cloud data. <span class="hlt">Radiative</span> effects of surface-observed cloud cover anomalies, called "cloud cover <span class="hlt">radiative</span> <span class="hlt">forcing</span> (CCRF) anomalies," are estimated based on a linear relationship to climatological cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> per unit cloud cover. Zonal mean estimated longwave CCRF has decreased over most of the globe. Estimated shortwave CCRF has become slightly stronger over northern midlatitude oceans and slightly weaker over northern midlatitude land areas. A long-term decline in the magnitude of estimated shortwave CCRF occurs over low-latitude land and ocean</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AtmEn..60...59L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012AtmEn..60...59L&link_type=ABSTRACT"><span id="translatedtitle">Aerosol hygroscopicity and its impact on atmospheric visibility and <span class="hlt">radiative</span> <span class="hlt">forcing</span> in Guangzhou during the 2006 PRIDE-PRD campaign</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Xingang; Zhang, Yuanhang; Cheng, Yafang; Hu, Min; Han, Tingting</p> <p>2012-12-01</p> <p>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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> (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 <span class="hlt">addition</span>, 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span>, especially in the regions with high RH.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000PhDT........32D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000PhDT........32D"><span id="translatedtitle">Speciated local aerosol characteristics and <span class="hlt">radiative</span> <span class="hlt">forcing</span> at a rural midwestern site</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dillner, Ann Marie</p> <p>2000-11-01</p> <p>In this research, physical and chemical properties of ambient aerosols were measured at a rural perturbed mid- latitude site (Bondville, IL) and used to calculate the aerosol optical properties and the resulting direct <span class="hlt">radiative</span> <span class="hlt">forcing</span>. Size-segregated aerosol samples were collected during the summer of 1997 using three parallel MOUDIs operating at ambient relative humidity. Two sample sets were used to obtain sulfate, organic carbon (OC), elemental carbon (EC), carbonate and total aerosol mass. The third sample set was used to obtain the size-specific and wavelength-dependent extinction efficiency of EC. The measured submicrometer mass concentration was 11.4 +/- 4.0 μg m-3. Ammonium sulfate comprised nearly half of the submicrometer aerosol and OC plus EC comprised 25%. Water content for ammonium sulfate and OC was estimated using both Köhler theory and parameterized water uptake curves from the literature. Water content for internally mixed aerosols was determined using a ZSR method. Aerosol optical properties (extinction efficiency, asymmetry parameter, single scatter albedo) were calculated from measured size distributions and wavelength dependent refractive indexes for each species and for internal and external mixtures using Mie theory. A technique, utilizing transmission measurements through extracts of size segregated ambient aerosol samples, was developed to obtain the extinction efficiency of EC. Measured EC extinction efficiencies ranged from 7.3 to 1.7 m2 g-1 at 550 nm, depending on particle diameter. Normalized direct aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> (W g-1 ) was calculated using the Column <span class="hlt">Radiation</span> Module (CRM) of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3). Aerosol optical properties, used in the model, were assumed to be uniform throughout the lowest one kilometer of the atmosphere. The normalized <span class="hlt">forcing</span> due to ammonium sulfate was -340 +/- 10 W g-1. OC was 1/3 larger and residue was 1/3 smaller. EC within an</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ACP....1512681W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ACP....1512681W"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">forcing</span> and climate response to projected 21st century aerosol decreases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Westervelt, D. M.; Horowitz, L. W.; Naik, V.; Golaz, J.-C.; Mauzerall, D. L.</p> <p>2015-11-01</p> <p>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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> and climate response resulting from the aerosol reductions. We find that the projected global <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> (-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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20030054376&hterms=safari&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsafari','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20030054376&hterms=safari&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dsafari"><span id="translatedtitle">Calculations of Aerosol <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> in the SAFARI Region from MODIS Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Remer, L. A.; Ichoku, C.; Kaufman, Y. J.; Chu, D. A.</p> <p>2003-01-01</p> <p>SAFARI 2000 provided the opportunity to validate MODIS aerosol retrievals and to correct any assumptions in the retrieval process. By comparing MODIS retrievals with ground-based sunphotometer data, we quantified the degree to which the MODIS algorithm underestimated the aerosol optical thickness. This discrepancy was attributed to underestimating the degree of light absorption by the southern African smoke aerosol. Correcting for this underestimation of absorption, produces more realistic aerosol retrievals that allow various applications of the MODIS aerosol products. One such application is the calculation of the aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> at the top and bottom of the atmosphere. The combination of MODIS accuracy, coverage, resolution and the ability to separate fine and coarse mode make this calculation substantially advanced over previous attempts with other satellites. We focus on the oceans adjacent to southern Africa and use a solar <span class="hlt">radiative</span> transfer model to perform the flux calculations. The <span class="hlt">forcing</span> at the top of atmosphere is calculated to be 10 W/sq m, while the <span class="hlt">forcing</span> at the surface is -26 W/sq m. These results resemble those calculated from INDOEX data, and are most sensitive to assumptions of aerosol absorption, the same parameter that initially interfered with our retrievals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080015434','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080015434"><span id="translatedtitle">The Effect of Asian Dust Aerosols on Cloud Properties and <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> from MODIS and CERES</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Huang, Jianping; Minnis, Patrick; Lin, Bing; Wang, Tianhe; Yi, Yuhong; Hu, Yongxiang; Sun-Mack, Sunny; Ayers, Kirk</p> <p>2005-01-01</p> <p>The effects of dust storms on cloud properties and <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> during later winter and early spring dust storm seasons over the studied region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25093939','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25093939"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">forcing</span> associated with particulate carbon emissions resulting from the use of mercury control technology.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lin, Guangxing; Penner, Joyce E; Clack, Herek L</p> <p>2014-09-01</p> <p>Injection of powdered activated carbon (PAC) adsorbents into the flue gas of coal fired power plants with electrostatic precipitators (ESPs) is the most mature technology to control mercury emissions for coal combustion. However, the PAC itself can penetrate ESPs to emit into the atmosphere. These emitted PACs have similar size and optical properties to submicron black carbon (BC) and thus could increase BC <span class="hlt">radiative</span> <span class="hlt">forcing</span> unintentionally. The present paper estimates, for the first time, the potential emission of PAC together with their climate <span class="hlt">forcing</span>. The global average maximum potential emissions of PAC is 98.4 Gg/yr for the year 2030, arising from the assumed adoption of the maximum potential PAC injection technology, the minimum collection efficiency, and the maximum PAC injection rate. These emissions cause a global warming of 2.10 mW m(-2) at the top of atmosphere and a cooling of -2.96 mW m(-2) at the surface. This warming represents about 2% of the warming that is caused by BC from direct fossil fuel burning and 0.86% of the warming associated with CO2 emissions from coal burning in power plants. Its warming is 8 times more efficient than the emitted CO2 as measured by the 20-year-integrated <span class="hlt">radiative</span> <span class="hlt">forcing</span> per unit of carbon input (the 20-year Global Warming Potential). PMID:25093939</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25096087','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25096087"><span id="translatedtitle">The average specific <span class="hlt">forced</span> <span class="hlt">radiation</span> wave impedance of a finite rectangular panel.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Davy, John L; Larner, David J; Wareing, Robin R; Pearse, John R</p> <p>2014-08-01</p> <p>The average specific <span class="hlt">forced</span> <span class="hlt">radiation</span> wave impedance of a finite rectangular panel is of importance for the prediction of both sound insulation and sound absorption. In 1982, Thomasson published numerical calculations of the average specific <span class="hlt">forced</span> <span class="hlt">radiation</span> wave impedance of a square of side length 2e for wave number k in half octave steps of ke from 0.25 to 64. Thomasson's calculations were for the case when the <span class="hlt">forced</span> bending wave number kb was less than or equal to k. Thomasson also published approximate formulas for values of ke above and below the published results. This paper combines Thomasson's high and low frequency formulas and compares this combined formula with Thomasson's numerical calculations. The real part of the approximate formula is between 0.7 dB higher and -1 dB lower than the numerical calculations. The imaginary part of the approximate formula is between 2.3 dB higher and -2.6 dB lower than the numerical calculations. This paper also gives approximate formulas for the case when kb is greater than or equal to k. The differences are between 0.8 and -1.2 dB for the imaginary part and between 6.2 and -2.4 dB for the real part. PMID:25096087</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DFD.R4006N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DFD.R4006N"><span id="translatedtitle">Numerics of surface acoustic wave (SAW) driven acoustic streaming and <span class="hlt">radiation</span> <span class="hlt">force</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nama, Nitesh; Barnkob, Rune; Kahler, Christian; Costanzo, Francesco; Jun Huang, Tony</p> <p>2015-11-01</p> <p>Recently, surface acoustic wave (SAW) based systems have shown great potential for various lab-on-a-chip applications. However, the physical understanding of the precise acoustic fields and associated acoustophoresis is rather limited. In this work, we present a numerical study of the acoustophoretic particle motion inside a SAW-actuated, liquid-filled polydimethylsiloxane (PDMS) microchannel. We utilize a perturbation approach to divide the flow variables into first- and second-order components. The first-order fields result in a time-averaged acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on suspended particles, as well as the time-averaged body <span class="hlt">force</span> terms that drive the second-order fields. We model the SAW actuation by a displacement function while we utilize impedance boundary conditions to model the PDMS walls. We identify the precise acoustic fields generated inside the microchannel and investigate a range of particle sizes to characterize the transition from streaming-dominated acoustophoresis to <span class="hlt">radiation-force</span>-dominated acoustophoresis. Lastly, we demonstrate the ability of SAW devices to tune the position of vertical pressure node inside the microchannel by tuning the phase difference between the two incoming surface acoustic waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhyS...91a5602S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhyS...91a5602S"><span id="translatedtitle"><span class="hlt">Radiative</span> condensation instability in partially ionized dusty plasma with polarization <span class="hlt">force</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharma, Prerana; Jain, Shweta</p> <p>2016-01-01</p> <p>This paper studies the effect of polarization <span class="hlt">force</span> on the <span class="hlt">radiative</span> condensation (RC) instability of a partially ionized dusty medium both in the presence and absence of self-gravitation. The temperature and density dependent heat loss function is considered in the process of heating and <span class="hlt">radiative</span> cooling. The linear-perturbation analysis is used to derive general dispersion relation and criteria for both the Jeans and RC instability. The condition of Jeans instability is modified due to the RC, polarization <span class="hlt">force</span>, magnetic field and dust thermal speed, whereas in the case of RC instability the instability criterion is modified due to the presence of dust thermal speed, magnetic field and polarization <span class="hlt">force</span>. The effects of various parameters have been numerically estimated on RC instability. It is clear from figure that the presence of polarization parameter and density dependent heat-loss function destabilize the system while the presence of temperature dependent heat-loss function, dust neutral collision frequency and ratio of neutral dust density stabilize the system. These findings are relevant for many areas of space and laboratory plasma research prime examples being the formation of dense molecular clouds in interstellar and intergalactic medium, condensations in planetary nebulae and in laboratory plasmas like tokamak edge plasma.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PMB....61..712M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PMB....61..712M"><span id="translatedtitle">Variable ultrasound trigger delay for improved magnetic resonance acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> imaging</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mougenot, Charles; Waspe, Adam; Looi, Thomas; Drake, James M.</p> <p>2016-01-01</p> <p>Magnetic resonance acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> imaging (MR-ARFI) allows the quantification of microscopic displacements induced by ultrasound pulses, which are proportional to the local acoustic intensity. This study describes a new method to acquire MR-ARFI maps, which reduces the measurement noise in the quantification of displacement as well as improving its robustness in the presence of motion. Two MR-ARFI sequences were compared in this study. The first sequence ‘variable MSG’ involves switching the polarity of the motion sensitive gradient (MSG) between odd and even image frames. The second sequence named ‘static MSG’ involves a variable ultrasound trigger delay to sonicate during the first or second MSG for odd and even image frames, respectively. As previously published, the data acquired with a variable MSG required the use of reference data acquired prior to any sonication to process displacement maps. In contrary, data acquired with a static MSG were converted to displacement maps without using reference data acquired prior to the sonication. Displacement maps acquired with both sequences were compared by performing sonications for three different conditions: in a polyacrylamide phantom, in the leg muscle of a freely breathing pig and in the leg muscle of pig under apnea. The comparison of images acquired at even image frames and odd image frames indicates that the sequence with a static MSG provides a significantly better steady state (p  <  0.001 based on a Student’s t-test) than the images acquired with a variable MSG. In <span class="hlt">addition</span> no reference data prior to sonication were required to process displacement maps for data acquired with a static MSG. The absence of reference data prior to sonication provided a 41% reduction of the spatial distribution of noise (p  <  0.001 based on a Student’s t-test) and reduced the sensitivity to motion for displacements acquired with a static MSG. No significant differences were expected and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011JGRD..116.1305A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011JGRD..116.1305A"><span id="translatedtitle">The vertical distribution of ozone instantaneous <span class="hlt">radiative</span> <span class="hlt">forcing</span> from satellite and chemistry climate models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aghedo, A. M.; Bowman, K. W.; Worden, H. M.; Kulawik, S. S.; Shindell, D. T.; Lamarque, J. F.; Faluvegi, G.; Parrington, M.; Jones, D. B. A.; Rast, S.</p> <p>2011-01-01</p> <p>We evaluate the instantaneous <span class="hlt">radiative</span> <span class="hlt">forcing</span> (IRF) of tropospheric ozone predicted by four state-of-the-art global chemistry climate models (AM2-Chem, CAM-Chem, ECHAM5-MOZ, and GISS-PUCCINI) against ozone distribution observed from the NASA Tropospheric Emission Spectrometer (TES) during August 2006. The IRF is computed through the application of an observationally constrained instantaneous <span class="hlt">radiative</span> <span class="hlt">forcing</span> kernels (IRFK) to the difference between TES and model-predicted ozone. The IRFK represent the sensitivity of outgoing longwave <span class="hlt">radiation</span> to the vertical and spatial distribution of ozone under all-sky condition. Through this technique, we find total tropospheric IRF biases from -0.4 to + 0.7 W/m2 over large regions within the tropics and midlatitudes, due to ozone differences over the region in the lower and middle troposphere, enhanced by persistent bias in the upper troposphere-lower stratospheric region. The zonal mean biases also range from -30 to +50 mW/m2 for the models. However, the ensemble mean total tropospheric IRF bias is less than 0.2 W/m2 within the entire troposphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/20930841','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/20930841"><span id="translatedtitle">An influence of solar spectral variations on <span class="hlt">radiative</span> <span class="hlt">forcing</span> of climate.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Haigh, Joanna D; Winning, Ann R; Toumi, Ralf; Harder, Jerald W</p> <p>2010-10-01</p> <p>The thermal structure and composition of the atmosphere is determined fundamentally by the incoming solar irradiance. <span class="hlt">Radiation</span> at ultraviolet wavelengths dissociates atmospheric molecules, initiating chains of chemical reactions-specifically those producing stratospheric ozone-and providing the major source of heating for the middle atmosphere, while <span class="hlt">radiation</span> at visible and near-infrared wavelengths mainly reaches and warms the lower atmosphere and the Earth's surface. Thus the spectral composition of solar <span class="hlt">radiation</span> is crucial in determining atmospheric structure, as well as surface temperature, and it follows that the response of the atmosphere to variations in solar irradiance depends on the spectrum. Daily measurements of the solar spectrum between 0.2 µm and 2.4 µm, made by the Spectral Irradiance Monitor (SIM) instrument on the Solar <span class="hlt">Radiation</span> and Climate Experiment (SORCE) satellite since April 2004, have revealed that over this declining phase of the solar cycle there was a four to six times larger decline in ultraviolet than would have been predicted on the basis of our previous understanding. This reduction was partially compensated in the total solar output by an increase in <span class="hlt">radiation</span> at visible wavelengths. Here we show that these spectral changes appear to have led to a significant decline from 2004 to 2007 in stratospheric ozone below an altitude of 45 km, with an increase above this altitude. Our results, simulated with a <span class="hlt">radiative</span>-photochemical model, are consistent with contemporaneous measurements of ozone from the Aura-MLS satellite, although the short time period makes precise attribution to solar effects difficult. We also show, using the SIM data, that solar <span class="hlt">radiative</span> <span class="hlt">forcing</span> of surface climate is out of phase with solar activity. Currently there is insufficient observational evidence to validate the spectral variations observed by SIM, or to fully characterize other solar cycles, but our findings raise the possibility that the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19920056625&hterms=Byung&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DByung','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19920056625&hterms=Byung&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DByung"><span id="translatedtitle">The significance of cloud-<span class="hlt">radiative</span> <span class="hlt">forcing</span> to the general circulation on climate time scales - A satellite interpretation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sohn, Byung-Ju; Smith, Eric A.</p> <p>1992-01-01</p> <p>This paper focuses on the role of cloud- and surface-atmosphere <span class="hlt">forcing</span> on the net <span class="hlt">radiation</span> balance and their potential impact on the general circulation at climate time scales. The globally averaged cloud-<span class="hlt">forcing</span> estimates and cloud sensitivity values taken from various recent studies are summarized. It is shown that the net <span class="hlt">radiative</span> heating over the tropics is principally due to high clouds, while the net cooling in mid- and high latitudes is dominated by low and middle clouds.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/991569','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/991569"><span id="translatedtitle">Anthropogenic Aerosol <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> in Asia Derived From Regional Models With Atmospheric and Aerosol Data Assimilation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Chung, Chul Eddy; Ramanathan, V.; Carmichael, Gregory; Kulkarni, S.; Tang, Youhua; Adhikary, Bhupesh; Leung, Lai-Yung R.; Qian, Yun</p> <p>2010-07-05</p> <p>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 <span class="hlt">Radiation</span> (MACR) model to produce total and anthropogenic aerosol direct solar <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> is -1.3 Wm<sup>-2 </sup>(TOA), +7.3 Wm<sup>-2</sup> (atmosphere) and -8.6 Wm<sup>-2</sup> (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<sup>-2</sup> (TOA), +4.5 Wm<sup>-2</sup> (atmosphere) and -6.8 Wm<sup>-2</sup> (surface), averaged in Asia. In the vertical, monthly <span class="hlt">forcing</span> is mainly concentrated below 600hPa with maxima around 800hPa. Seasonally, low-level <span class="hlt">forcing</span> is far larger in dry season than in wet season in South Asia, whereas the wet season <span class="hlt">forcing</span> exceeds the dry season <span class="hlt">forcing</span> in East Asia. The anthropogenic <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..MARY50003E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..MARY50003E"><span id="translatedtitle">Fluctuation-Induced Interactions in external magnetic fields: Casimir <span class="hlt">force</span> and <span class="hlt">Radiative</span> Heat Transfer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Esquivel-Sirvent, Raul</p> <p></p> <p>Thermally induced electromagnetic fields give rise to the Casimir <span class="hlt">force</span> and the near field heat transfer between two bodies separated by a gap. These phenomena are described by Rytova's theory of fluctuating electromagnetic fields and both the Casimir <span class="hlt">force</span> and the near field heat transfer depend on the local dielectric function of the bodies. In this work we present a theoretical calculation on the modulation of fluctuation-induced interactions in the presence of an external magnetic field. The system consists of two parallel plates separated by a gap d. Each plate is isotropic and has a local dielectric function. Applying an external magnetic field parallel to the plates, in the so called Voigt configuration, the plates become anisotropic. In particular, we consider plates of InSb. For the Casimir <span class="hlt">force</span> the two plates are kept at the same temperature and the external field reduces the magnitude of the <span class="hlt">force</span>. Similarly if the two plates are kept at different temperature the near field <span class="hlt">radiative</span> heat transfer is modulated by the magnitude of the external magnetic field. The results are extended to semiconducting quantum wells. In both cases, the excitation of magnetoplasmons provides an explanation for the observed effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016CeMDA.tmp...32X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016CeMDA.tmp...32X"><span id="translatedtitle"><span class="hlt">Forced</span> periodic motions by solar <span class="hlt">radiation</span> pressure around uniformly rotating asteroids</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xin, Xiaosheng; Scheeres, Daniel J.; Hou, Xiyun</p> <p>2016-06-01</p> <p>Since asteroids generally have relatively weak gravity fields, solar <span class="hlt">radiation</span> pressure (SRP) is a major perturbation for orbits in their vicinity, which under certain circumstances can be even larger than the third-body gravitational perturbations. In this work, by adopting a triaxial ellipsoid model for the asteroid and taking into account of SRP, the <span class="hlt">forced</span> periodic motions caused by SRP around equilibrium points are studied in the body-fixed frame of the asteroid. For <span class="hlt">forced</span> periodic motions around saddle equilibrium points, we find that the SRP does not alter their stability yet does change the morphology of the associated invariant manifolds. For <span class="hlt">forced</span> periodic motions around center equilibrium points, different types of orbits are identified. Their stability changes with different parameters, i.e., the asteroid's shape and spin period, the latitude of the Sun, and the magnitude of SRP. Evolution of these <span class="hlt">forced</span> periodic motions is described in detail and some interesting phenomena are found. Stability results found for our ideal model with the Sun at a fixed distance and latitude are shown to predict stability regions in a realistic model with the Sun on inclined and elliptic orbits. Though our work is based on the simplified triaxial ellipsoid model, similar computation method and conclusions should also be applicable to real asteroids.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=19900023749&hterms=friends&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dfriends','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=19900023749&hterms=friends&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dfriends"><span id="translatedtitle">A <span class="hlt">radiation</span>-driven stellar wind model with a line <span class="hlt">force</span> cutoff</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abbott, Mark J.; Friend, David B.</p> <p>1989-01-01</p> <p>This paper presents a model for a <span class="hlt">radiation</span>-driven stellar wind in which the driving <span class="hlt">force</span> is abruptly cut off at an adjustable distance from the star. The model is intended to give a first approximation of the effects of ionizing shocks in a stellar wind on the terminal velocity and mass-loss rate. As expected, the wind velocity is found to decrease after the line <span class="hlt">force</span> is cut off. The terminal velocity depends directly on the velocity of the wind at the point where the driving <span class="hlt">force</span> is cut off. The mass-loss rate is found to be unaffected as long as the cutoff is outside the critical point of the flow. The model is applied to the star Tau Sco, a strong X-ray source with an anomalously low terminal velocity. It is shown that this low terminal velocity can be caused by a cutoff of the line <span class="hlt">force</span> at a distance which is consistent with the idea that the observed X-rate emission is produced by shocks in the wind.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/21027627','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/21027627"><span id="translatedtitle">Role of <span class="hlt">radiation</span> reaction <span class="hlt">forces</span> in the dynamics of centrifugally accelerated particles</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Dalakishvili, G. T.; Rogava, A. D.; Berezhiani, V. I.</p> <p>2007-08-15</p> <p>In this paper we study the influence of <span class="hlt">radiation</span> reaction (RR) <span class="hlt">forces</span> on the dynamics of centrifugally accelerated particles. It is assumed that the particles move along magnetic field lines anchored in the rotating central object. The common 'bead-on-the-wire' approximation is used. The solutions are found and analyzed for cases when the form of the prescribed trajectory (rigidly rotating field line) is approximated by: (a) straight line, and (b) Archimedes spiral. Dynamics of neutral and charged particles are compared with the emphasis on the role of RR <span class="hlt">forces</span> in the latter case. It is shown that for charged particles there exist locations of stable equilibrium. It is demonstrated that for particular initial conditions RR <span class="hlt">forces</span> cause centripetal motion of the particles: their 'falling' on the central rotating object. It is found that in the case of Archimedes spiral both neutral and charged particles can reach infinity where their motion has asymptotically <span class="hlt">force</span>-free character. The possible importance of these processes for the acceleration of relativistic, charged particles by rotating magnetospheres in the context of the generation of nonthermal, high-energy emission of AGN and pulsars is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007PhRvD..76d5003D&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007PhRvD..76d5003D&link_type=ABSTRACT"><span id="translatedtitle">Role of <span class="hlt">radiation</span> reaction <span class="hlt">forces</span> in the dynamics of centrifugally accelerated particles</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dalakishvili, G. T.; Rogava, A. D.; Berezhiani, V. I.</p> <p>2007-08-01</p> <p>In this paper we study the influence of <span class="hlt">radiation</span> reaction (RR) <span class="hlt">forces</span> on the dynamics of centrifugally accelerated particles. It is assumed that the particles move along magnetic field lines anchored in the rotating central object. The common “bead-on-the-wire” approximation is used. The solutions are found and analyzed for cases when the form of the prescribed trajectory (rigidly rotating field line) is approximated by: (a) straight line, and (b) Archimedes spiral. Dynamics of neutral and charged particles are compared with the emphasis on the role of RR <span class="hlt">forces</span> in the latter case. It is shown that for charged particles there exist locations of stable equilibrium. It is demonstrated that for particular initial conditions RR <span class="hlt">forces</span> cause centripetal motion of the particles: their “falling” on the central rotating object. It is found that in the case of Archimedes spiral both neutral and charged particles can reach infinity where their motion has asymptotically <span class="hlt">force</span>-free character. The possible importance of these processes for the acceleration of relativistic, charged particles by rotating magnetospheres in the context of the generation of nonthermal, high-energy emission of AGN and pulsars is discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/23297880','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/23297880"><span id="translatedtitle">Three-dimensional acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on an arbitrarily located elastic sphere.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Baresch, Diego; Thomas, Jean-Louis; Marchiano, Régis</p> <p>2013-01-01</p> <p>This work aims to model the acoustic <span class="hlt">radiation</span> <span class="hlt">forces</span> acting on an elastic sphere placed in an inviscid fluid. An expression of the axial and transverse <span class="hlt">forces</span> exerted on the sphere is derived. The analysis is based on the scattering of an arbitrary acoustic field expanded in the spherical coordinate system centered on the spherical scatterer. The sphere is allowed to be arbitrarily located. The special case of high order Bessel beams, acoustical vortices, are considered. These types of beams have a helicoidal wave front, i.e., a screw-type phase singularity and hence, the beam has a central dark core of zero amplitude surrounded by an intense ring. Depending on the sphere's radius, different radial equilibrium positions may exist and the sphere can be set in rotation around the beam axis by an azimuthal <span class="hlt">force</span>. This confirms the pseudo-angular moment transfer from the beam to the sphere. Cases where the axial <span class="hlt">force</span> is directed opposite to the direction of the beam propagation are investigated and the potential use of Bessel beams as tractor beams is demonstrated. Numerical results provide an impetus for further designing acoustical tweezers for potential applications in particle entrapment and remote controlled manipulation. PMID:23297880</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://ntrs.nasa.gov/search.jsp?R=20020087576&hterms=Vapor+pressure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3D%2528Vapor%2Bpressure%2529','NASA-TRS'); return false;" href="http://ntrs.nasa.gov/search.jsp?R=20020087576&hterms=Vapor+pressure&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3D%2528Vapor%2Bpressure%2529"><span id="translatedtitle">The Action of Pressure-<span class="hlt">Radiation</span> <span class="hlt">Forces</span> on Pulsating Vapor Bubbles</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hao, Y.; Oguz, N.; Prosperetti, A.</p> <p>2001-01-01</p> <p>The action of pressure-<span class="hlt">radiation</span> (or Bjerknes) <span class="hlt">forces</span> on gas bubbles is well understood. This paper studies the analogous phenomenon for vapor bubbles, about which much less is known. A possible practical application is the removal of boiling bubbles from the neighborhood of a heated surface in the case of a downward facing surface or in the absence of gravity. For this reason, the case of a bubble near a plane rigid surface is considered in detail. It is shown that, when the acoustic wave fronts are parallel to the surface, the bubble remains trapped due to secondary Bjerknes <span class="hlt">force</span> caused by an "image bubble." When the wave fronts are perpendicular to the surface, on the other hand, the bubble can be made to slide laterally.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.5318M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.5318M"><span id="translatedtitle">The spectroscopic foundation of <span class="hlt">radiative</span> <span class="hlt">forcing</span> of climate by carbon dioxide</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mlynczak, Martin G.; Daniels, Taumi S.; Kratz, David P.; Feldman, Daniel R.; Collins, William D.; Mlawer, Eli J.; Alvarado, Matthew J.; Lawler, James E.; Anderson, L. W.; Fahey, David W.; Hunt, Linda A.; Mast, Jeffrey C.</p> <p>2016-05-01</p> <p>The <span class="hlt">radiative</span> <span class="hlt">forcing</span> (RF) of carbon dioxide (CO2) is the leading contribution to climate change from anthropogenic activities. Calculating CO2 RF requires detailed knowledge of spectral line parameters for thousands of infrared absorption lines. A reliable spectroscopic characterization of CO2 <span class="hlt">forcing</span> is critical to scientific and policy assessments of present climate and climate change. Our results show that CO2 RF in a variety of atmospheres is remarkably insensitive to known uncertainties in the three main CO2 spectroscopic parameters: the line shapes, line strengths, and half widths. We specifically examine uncertainty in RF due to line mixing as this process is critical in determining line shapes in the far wings of CO2 absorption lines. RF computed with a Voigt line shape is also examined. Overall, the spectroscopic uncertainty in present-day CO2 RF is less than 1%, indicating a robust foundation in our understanding of how rising CO2 warms the climate system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1130721','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1130721"><span id="translatedtitle">Estimating the <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> of Carbonaceous Aerosols over California based on Satellite and Ground Observations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Xu, Yangyang; Bahadur, R.; Zhao, Chun; Leung, Lai-Yung R.</p> <p>2013-10-04</p> <p>Carbonaceous aerosols have the potential to impact climate both through directly absorbing incoming solar <span class="hlt">radiation</span>, 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 <span class="hlt">radiative</span> <span class="hlt">forcing</span>. This study makes the first observationally constrained assessment of the direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AtmRe.157...29R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AtmRe.157...29R"><span id="translatedtitle">Black carbon <span class="hlt">radiative</span> <span class="hlt">forcing</span> over the Indian Arctic station, Himadri during the Arctic Summer of 2012</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Raju, M. P.; Safai, P. D.; Sonbawne, S. M.; Naidu, C. V.</p> <p>2015-04-01</p> <p>The warming of Arctic region has recently gained worldwide attention due to its projected impacts on global climate system. The effect of anthropogenic black carbon (BC) aerosol on snow is of enduring interest due to its role in aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> and further consequences for Arctic and global climate change. Using an A ethalometer, measurements of BC aerosols were continuously carried out over the Indian Arctic Station, Himadri during the Arctic Summer (23 July to 19 August) of 2012. Monthly mean BC mass concentration during July and August was found to be 0.093 ± 0.046 and 0.069 ± 0.050 μg/m3, respectively. BC mass concentration showed maximum loading during 0800-1600 LT. Transport from distant sources (as observed from air mass back trajectories) apart from some local anthropogenic activities (emissions from shipping and power plant) could be the possible sources for observed BC concentration at Himadri. Using the OPAC and SBDART models, optical properties and aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> (ARF) in the spectral range 0.2 to 4 μm for composite aerosol and without-BC aerosol at the top of the atmosphere, surface and atmosphere were computed. The presence of BC resulted in positive <span class="hlt">radiative</span> <span class="hlt">forcing</span> in the atmosphere leading to warming effect (+ 2.1 W/m2) whereas cooling was observed at the top of the atmosphere (- 0.4 W/m2) and at surface (- 2.5 W/m2). BC formed about 57% of atmospheric ARF.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3118908','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3118908"><span id="translatedtitle">ACOUSTIC <span class="hlt">RADIATION</span> <span class="hlt">FORCE</span>-DRIVEN ASSESSMENT OF MYOCARDIAL ELASTICITY USING THE DISPLACEMENT RATIO RATE (DRR) METHOD</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bouchard, Richard R.; Hsu, Stephen J.; Palmeri, Mark L.; Rouze, Ned C.; Nightingale, Kathryn R.; Trahey, Gregg E.</p> <p>2011-01-01</p> <p>A noninvasive method of characterizing myocardial stiffness could have significant implications in diagnosing cardiac disease. Acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> (ARF)–driven techniques have demonstrated their ability to discern elastic properties of soft tissue. For the purpose of myocardial elasticity imaging, a novel ARF-based imaging technique, the displacement ratio rate (DRR) method, was developed to rank the relative stiffnesses of dynamically varying tissue. The basis and performance of this technique was demonstrated through numerical and phantom imaging results. This new method requires a relatively small temporal (<1 ms) and spatial (tenths of mm2) sampling window and appears to be independent of applied ARF magnitude. The DRR method was implemented in two in vivo canine studies, during which data were acquired through the full cardiac cycle by imaging directly on the exposed epicardium. These data were then compared with results obtained by acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> impulse (ARFI) imaging and shear wave velocimetry, with the latter being used as the gold standard. Through the cardiac cycle, velocimetry results portray a range of shear wave velocities from 0.76–1.97 m/s, with the highest velocities observed during systole and the lowest observed during diastole. If a basic shear wave elasticity model is assumed, such a velocity result would suggest a period of increased stiffness during systole (when compared with diastole). Despite drawbacks of the DRR method (i.e., sensitivity to noise and limited stiffness range), its results predicted a similar cyclic stiffness variation to that offered by velocimetry while being insensitive to variations in applied <span class="hlt">radiation</span> <span class="hlt">force</span>. PMID:21645966</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMGC24A..06S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMGC24A..06S"><span id="translatedtitle">Cumulative <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> Implications of Deployment Strategies for Carbon Capture and Storage</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sathre, R. C.; Masanet, E.</p> <p>2011-12-01</p> <p>Carbon capture and storage (CCS) is increasingly discussed as a potential means of mitigating the climate disruption associated with fossil fuel use. Some technologies for capturing, transporting, and sequestering carbon dioxide (CO2) are already mature, while others technologies under development may lead to more cost- and energy-efficient CCS systems. Various elements of CCS systems are currently in operation at relatively small scale, but will need to be scaled up very substantially in order to make a significant contribution to climate change mitigation. Because the rate of fossil fuel CO2 emission is continuing to increase and the emitted CO2 will remain in the atmosphere for long time periods, the speed at which CCS is deployed will strongly affect the cumulative CO2 emission and the climate impacts. To better understand these issues, in this analysis we integrate scenario forecasting of energy supply systems, life cycle emission modeling, and time-dependent calculations of cumulative <span class="hlt">radiative</span> <span class="hlt">forcing</span>. We develop a series of CCS deployment scenarios that describe plausible future trajectories for CCS implementation in the US electric power plant fleet. The scenarios incorporate dimensions such as speed of deployment build-out, year of initiating deployment, efficiency of capture technology, and installation in new power plants vs. retrofitting existing plants. We conduct life cycle greenhouse gas (GHG) emissions analyses of each scenario to estimate annual emission profiles of CO2, CH4, and N2O over a 90-year time horizon, from 2010 to 2100. We then model the atmospheric dynamics of the emitted GHGs including atmospheric decay and instantaneous <span class="hlt">radiative</span> <span class="hlt">forcing</span> patterns over time. Finally, we determine the cumulative <span class="hlt">radiative</span> <span class="hlt">forcing</span> of each scenario, which we use as a proxy for surface temperature change and resulting disruption to physical, ecological and social systems. The results show strong climate mitigation benefits of early, aggressive</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A33E0266D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A33E0266D"><span id="translatedtitle">The impacts of land use, <span class="hlt">radiative</span> <span class="hlt">forcing</span>, and biological changes on regional climate in Japan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dairaku, K.; Pielke, R. A., Sr.</p> <p>2013-12-01</p> <p>Because regional responses of surface hydrological and biogeochemical changes are particularly complex, it is necessary to develop assessment tools for regional scale adaptation to climate. We developed a dynamical downscaling method using the regional climate model (NIED-RAMS) over Japan. The NIED-RAMS model includes a plant model that considers biological processes, the General Energy and Mass Transfer Model (GEMTM) which adds spatial resolution to accurately assess critical interactions within the regional climate system for vulnerability assessments to climate change. We digitalized a potential vegetation map that formerly existed only on paper into Geographic Information System data. It quantified information on the reduction of green spaces and the expansion of urban and agricultural areas in Japan. We conducted regional climate sensitivity experiments of land use and land cover (LULC) change, <span class="hlt">radiative</span> <span class="hlt">forcing</span>, and biological effects by using the NIED-RAMS with horizontal grid spacing of 20 km. We investigated regional climate responses in Japan for three experimental scenarios: 1. land use and land cover is changed from current to potential vegetation; 2. <span class="hlt">radiative</span> <span class="hlt">forcing</span> is changed from 1 x CO2 to 2 x CO2; and 3. biological CO2 partial pressures in plants are doubled. The experiments show good accuracy in reproducing the surface air temperature and precipitation. The experiments indicate the distinct change of hydrological cycles in various aspects due to anthropogenic LULC change, <span class="hlt">radiative</span> <span class="hlt">forcing</span>, and biological effects. The relative impacts of those changes are discussed and compared. Acknowledgments This study was conducted as part of the research subject "Vulnerability and Adaptation to Climate Change in Water Hazard Assessed Using Regional Climate Scenarios in the Tokyo Region' (National Research Institute for Earth Science and Disaster Prevention; PI: Koji Dairaku) of Research Program on Climate Change Adaptation (RECCA), and was supported by the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013APS..DFDA24007A&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013APS..DFDA24007A&link_type=ABSTRACT"><span id="translatedtitle">Acoustic <span class="hlt">Radiation</span> <span class="hlt">Force</span> on a Finite-Sized Particle due to an Acoustic Field in a Viscous Compressible Fluid</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Annamalai, Subramanian; Parmar, Manoj; Balachandar, S.</p> <p>2013-11-01</p> <p>Particles when subjected to acoustic waves experience a time-averaged second-order <span class="hlt">force</span> known as the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>, which is of prime importance in the fields of microfluidics and acoustic levitation. Here, the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> on a rigid spherical particle in a viscous compressible medium due to progressive and standing waves is considered. The relevant length scales include: particle radius (a), acoustic wavelength (λ) and viscous penetration depth (δ). While a / λ and a / δ are arbitrary, δ << λ . A farfield derivation approach has been used in determining the <span class="hlt">radiated</span> <span class="hlt">force</span>. Expressing the flow-field as a sum of the incident and scattered fields, an analytical expression for the <span class="hlt">force</span> is obtained as a summation over infinite series (monopole, dipole and higher sources). These results indicate that the contributions from monopole, dipole and their cross-interaction are sufficient to describe the acoustic <span class="hlt">radiation</span> <span class="hlt">force</span>. Subsequently, the monopole and dipole strengths are represented in terms of the particle surface and volume averages of the incoming velocity. This generalization allows one to evaluate the <span class="hlt">radiation</span> <span class="hlt">force</span> for an incoming wave of any functional form. However acoustic streaming effects are neglected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002JGRD..107.8028C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002JGRD..107.8028C"><span id="translatedtitle">Simulation of aerosol distributions and <span class="hlt">radiative</span> <span class="hlt">forcing</span> for INDOEX: Regional climate impacts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Collins, William D.; Rasch, Phillip J.; Eaton, Brian E.; Fillmore, David W.; Kiehl, Jeffrey T.; Beck, C. Trevor; Zender, Charles S.</p> <p>2002-10-01</p> <p>The direct <span class="hlt">radiative</span> <span class="hlt">forcing</span> by aerosols over the Indian Ocean region is simulated for the Indian Ocean Experiment (INDOEX) Intensive Field Phase during Spring 1999. The <span class="hlt">forcing</span> is calculated for the top-of-atmosphere (TOA), surface, and atmosphere by differencing shortwave fluxes computed with and without aerosols. The calculation includes the effects of sea-salt, sulfate, carbonaceous, and soil-dust aerosols. The aerosol distributions are obtained from a global aerosol simulation including assimilation of satellite retrievals of aerosol optical thickness (AOT). The time-dependent, three-dimensional aerosol distributions are derived with a chemical transport model driven with meteorological analyses for this period. The surface albedos are obtained from a land-surface model <span class="hlt">forced</span> with an identical meteorological analysis and satellite-derived rainfall and insolation. These calculations are consistent with in situ observations of the surface insolation over the central Indian Ocean and with satellite measurements of the reflected shortwave <span class="hlt">radiation</span>. The calculations show that the surface insolation under clear skies is reduced by as much as 40 W/m2 over the Indian subcontinent by natural and anthropogenic aerosols. This reduction in insolation is accompanied by an increase in shortwave flux absorbed in the atmosphere by 25 W/m2. The inclusion of clouds in the calculations changes the direct effect by less than 2 W/m2 over the Indian subcontinent, although the reduction is much larger over China. The magnitude of the difference between all-sky and clear-sky <span class="hlt">forcing</span> is quite sensitive to the three-dimensional spatial relationship between the aerosol and cloud fields, and other estimates of the difference for the INDOEX Intensive Field Phase are as large as 5 W/m2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AMTD....5.4041Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AMTD....5.4041Z"><span id="translatedtitle">Effect of spectrally varying albedo of vegetation surfaces on shortwave <span class="hlt">radiation</span> fluxes and direct aerosol <span class="hlt">forcing</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, L.; Martins, J. V.; Yu, H.</p> <p>2012-06-01</p> <p>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 <span class="hlt">forcing</span> 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 <span class="hlt">radiation</span>; the other two corrections are less sensitive due to the weaker solar <span class="hlt">radiation</span> 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 <span class="hlt">forcing</span> by over 10 W m-2. Specifically, for Amazon vegetation types, MEVA can improve the accuracy of daily averaged aerosol <span class="hlt">forcing</span> at equator at equinox by 3.7 W m-2 (about 70% of the aerosol <span class="hlt">forcing</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ACPD...1110875C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ACPD...1110875C"><span id="translatedtitle">Ozone database in support of CMIP5 simulations: results and corresponding <span class="hlt">radiative</span> <span class="hlt">forcing</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cionni, I.; Eyring, V.; Lamarque, J. F.; Randel, W. J.; Stevenson, D. S.; Wu, F.; Bodeker, G. E.; Shepherd, T. G.; Shindell, D. T.; Waugh, D. W.</p> <p>2011-04-01</p> <p>A continuous tropospheric and stratospheric vertically resolved ozone time series, from 1850 to 2099, has been generated to be used as <span class="hlt">forcing</span> in global climate models that do not include interactive chemistry. A multiple linear regression analysis of SAGE I+II satellite observations and polar ozonesonde measurements is used for the stratospheric zonal mean dataset during the well-observed period from 1979 to 2009. In <span class="hlt">addition</span> to terms describing the mean annual cycle, the regression includes terms representing equivalent effective stratospheric chlorine (EESC) and the 11-yr solar cycle variability. The EESC regression fit coefficients, together with pre-1979 EESC values, are used to extrapolate the stratospheric ozone time series backward to 1850. While a similar procedure could be used to extrapolate into the future, coupled chemistry climate model (CCM) simulations indicate that future stratospheric ozone abundances are likely to be significantly affected by climate change, and capturing such effects through a regression model approach is not feasible. Therefore, the stratospheric ozone dataset is extended into the future (merged in 2009) with multi-model mean projections from 13 CCMs that performed a simulation until 2099 under the SRES (Special Report on Emission Scenarios) A1B greenhouse gas scenario and the A1 adjusted halogen scenario in the second round of the Chemistry-Climate Model Validation (CCMVal-2) Activity. The stratospheric zonal mean ozone time series is merged with a three-dimensional tropospheric data set extracted from simulations of the past by two CCMs (CAM3.5 and PUCCINI) and of the future by one CCM (CAM3.5). The future tropospheric ozone time series continues the historical CAM3.5 simulation until 2099 following the four different Representative Concentration Pathways (RCPs). Generally good agreement is found between the historical segment of the ozone database and satellite observations, although it should be noted that total column</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011ACP....1111267C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011ACP....1111267C"><span id="translatedtitle">Ozone database in support of CMIP5 simulations: results and corresponding <span class="hlt">radiative</span> <span class="hlt">forcing</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cionni, I.; Eyring, V.; Lamarque, J. F.; Randel, W. J.; Stevenson, D. S.; Wu, F.; Bodeker, G. E.; Shepherd, T. G.; Shindell, D. T.; Waugh, D. W.</p> <p>2011-11-01</p> <p>A continuous tropospheric and stratospheric vertically resolved ozone time series, from 1850 to 2099, has been generated to be used as <span class="hlt">forcing</span> in global climate models that do not include interactive chemistry. A multiple linear regression analysis of SAGE I+II satellite observations and polar ozonesonde measurements is used for the stratospheric zonal mean dataset during the well-observed period from 1979 to 2009. In <span class="hlt">addition</span> to terms describing the mean annual cycle, the regression includes terms representing equivalent effective stratospheric chlorine (EESC) and the 11-yr solar cycle variability. The EESC regression fit coefficients, together with pre-1979 EESC values, are used to extrapolate the stratospheric ozone time series backward to 1850. While a similar procedure could be used to extrapolate into the future, coupled chemistry climate model (CCM) simulations indicate that future stratospheric ozone abundances are likely to be significantly affected by climate change, and capturing such effects through a regression model approach is not feasible. Therefore, the stratospheric ozone dataset is extended into the future (merged in 2009) with multi-model mean projections from 13 CCMs that performed a simulation until 2099 under the SRES (Special Report on Emission Scenarios) A1B greenhouse gas scenario and the A1 adjusted halogen scenario in the second round of the Chemistry-Climate Model Validation (CCMVal-2) Activity. The stratospheric zonal mean ozone time series is merged with a three-dimensional tropospheric data set extracted from simulations of the past by two CCMs (CAM3.5 and GISS-PUCCINI) and of the future by one CCM (CAM3.5). The future tropospheric ozone time series continues the historical CAM3.5 simulation until 2099 following the four different Representative Concentration Pathways (RCPs). Generally good agreement is found between the historical segment of the ozone database and satellite observations, although it should be noted that total column</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPhCS.656a2001S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPhCS.656a2001S"><span id="translatedtitle">Estimation of mechanical properties of gelatin using a microbubble under acoustic <span class="hlt">radiation</span> <span class="hlt">force</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shirota, Eriko; Ando, Keita</p> <p>2015-12-01</p> <p>This paper is concerned with observations of the translation of a microbubble (80 μm or 137 μm in radius) in a viscoelastic medium (3 w% gelatin), which is induced by acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> originating from 1 MHz focused ultrasound. An optical system using a high-speed camera was designed to visualize the bubble translation and deformation. If the bubble remains its spherical shape under the sonication, the bubble translation we observed can be described by theory based on the Voigt model for linear viscoelastic solids; mechanical properties of the gelatin are calculated from measurements of the terminal displacement under the sonication.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3771831','PMC'); return false;" href="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3771831"><span id="translatedtitle">Optical theorem for acoustic non-diffracting beams and application to <span class="hlt">radiation</span> <span class="hlt">force</span> and torque</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhang, Likun; Marston, Philip L.</p> <p>2013-01-01</p> <p>Acoustical and optical non-diffracting beams are potentially useful for manipulating particles and larger objects. An extended optical theorem for a non-diffracting beam was given recently in the context of acoustics. The theorem relates the extinction by an object to the scattering at the forward direction of the beam’s plane wave components. Here we use this theorem to examine the extinction cross section of a sphere centered on the axis of the beam, with a non-diffracting Bessel beam as an example. The results are applied to recover the axial <span class="hlt">radiation</span> <span class="hlt">force</span> and torque on the sphere by the Bessel beam. PMID:24049681</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatPh..12..683C&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016NatPh..12..683C&link_type=ABSTRACT"><span id="translatedtitle">Observation of strong <span class="hlt">radiation</span> pressure <span class="hlt">forces</span> from squeezed light on a mechanical oscillator</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Clark, Jeremy B.; Lecocq, Florent; Simmonds, Raymond W.; Aumentado, José; Teufel, John D.</p> <p>2016-07-01</p> <p>In quantum-enhanced sensing, non-classical states are used to improve the sensitivity of a measurement. Squeezed light, in particular, has proved a useful resource in enhanced mechanical displacement sensing, although the fundamental limit to this enhancement due to the Heisenberg uncertainty principle has not been encountered experimentally. Here we use a microwave cavity optomechanical system to observe the squeezing-dependent <span class="hlt">radiation</span> pressure noise that necessarily accompanies any quantum enhancement of the measurement precision and ultimately limits the measurement noise performance. By increasing the measurement strength so that <span class="hlt">radiation</span> pressure <span class="hlt">forces</span> dominate the thermal motion of the mechanical oscillator, we exploit the optomechanical interaction to implement an efficient quantum nondemolition measurement of the squeezed light. Thus, our results show how the mechanical oscillator improves the measurement of non-classical light, just as non-classical light enhances the measurement of the motion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000039435','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000039435"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">Forcing</span> of the Pinatubo Aerosol as a Function of Latitude and Time</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bergstrom, R. W.; Kinne, S.; Russell, P. B.; Bauman, J. J.; Minnis, P.</p> <p>1996-01-01</p> <p>We present calculations of the <span class="hlt">radiative</span> <span class="hlt">forcing</span> 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 <span class="hlt">radiative</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014APS..DFDA13002M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2014APS..DFDA13002M&link_type=ABSTRACT"><span id="translatedtitle">Acoustical <span class="hlt">radiation</span> torque and <span class="hlt">force</span> for spheres and Bessel beam extinction efficiency</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Marston, Philip L.; Zhang, Likun</p> <p>2014-11-01</p> <p>The scattering of optical and acoustical beams is relevant to the levitation and manipulation of drops. Here we examine theoretical developments in the acoustical case. We previously showed how the optical theorem for extinction can be extended to invariant beams. The example of a sphere in a Bessel beam facilitates the direct comparison with a circular disc computed using Babinet's principle and the Kirchhoff approximation. In related work, by considering traveling or standing wave first-order vortex beams we previously showed that the <span class="hlt">radiation</span> torque is the ratio of the absorbed power and the radian acoustic frequency. By modifying the scattering to account for the viscosity of the surrounding fluid in the analysis of the absorbed power, approximations for <span class="hlt">radiation</span> torque and <span class="hlt">force</span> are obtained at long wavelengths in special cases and these can be compared with results published elsewhere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016HMT....52..361A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016HMT....52..361A"><span id="translatedtitle">Numerical analysis of interaction between non-gray <span class="hlt">radiation</span> and <span class="hlt">forced</span> convection flow over a recess using the full-spectrum k-distribution method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Atashafrooz, M.; Gandjalikhan Nassab, S. A.; Lari, K.</p> <p>2016-02-01</p> <p>In the present work, the interaction between non-gray <span class="hlt">radiation</span> and <span class="hlt">forced</span> convection in a laminar <span class="hlt">radiating</span> gas flow over a recess including two backward and forward facing steps in a duct is investigated numerically. Distributions of absorption coefficients across the spectrum (50 cm-1 < η < 20,000 cm-1) are obtained from the HITRAN2008 database. The full-spectrum k-distribution method is used to account for non-gray <span class="hlt">radiation</span> properties, while the gray <span class="hlt">radiation</span> calculations are carried out using the Planck mean absorption coefficient. To find the divergence of <span class="hlt">radiative</span> heat flux distribution, the <span class="hlt">radiative</span> transfer equation is solved by the discrete ordinates method. The effects of <span class="hlt">radiation</span>-conduction parameter, wall emissivity, scattering coefficient and recess length on heat transfer behaviors of the convection-<span class="hlt">radiation</span> system are investigated for both gray and non-gray mediums. In <span class="hlt">addition</span>, the results of gray medium are compared with non-gray results in order to judge if the differences between these two approaches are significant enough to justify the usage of non-gray models. Results show that for air mixture with 10 % CO2 and 20 % H2O, use of gray model for the <span class="hlt">radiative</span> properties may cause significant errors and should be avoided.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011ACPD...1132647G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011ACPD...1132647G&link_type=ABSTRACT"><span id="translatedtitle">Shortwave <span class="hlt">radiative</span> <span class="hlt">forcing</span> and efficiency of key aerosol types using AERONET data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>García, O. E.; Díaz, J. P.; Expósito, F. J.; Díaz, A. M.; Dubovik, O.; Derimian, Y.; Dubuisson, P.; Roger, J.-C.</p> <p>2011-12-01</p> <p>The shortwave <span class="hlt">radiative</span> <span class="hlt">forcing</span> (ΔF) and the <span class="hlt">radiative</span> <span class="hlt">forcing</span> efficiency (ΔFeff) of natural and anthropogenic aerosols have been analyzed using estimates of <span class="hlt">radiation</span> 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 <span class="hlt">radiative</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012ACP....12.5129G&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012ACP....12.5129G&link_type=ABSTRACT"><span id="translatedtitle">Shortwave <span class="hlt">radiative</span> <span class="hlt">forcing</span> and efficiency of key aerosol types using AERONET data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>García, O. E.; Díaz, J. P.; Expósito, F. J.; Díaz, A. M.; Dubovik, O.; Derimian, Y.; Dubuisson, P.; Roger, J.-C.</p> <p>2012-06-01</p> <p>The shortwave <span class="hlt">radiative</span> <span class="hlt">forcing</span> (ΔF) and the <span class="hlt">radiative</span> <span class="hlt">forcing</span> efficiency (ΔFeff) of natural and anthropogenic aerosols have been analyzed using estimates of <span class="hlt">radiation</span> 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 <span class="hlt">radiative</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JMetR..29..779L&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2015JMetR..29..779L&link_type=ABSTRACT"><span id="translatedtitle">Cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span> induced by layered clouds and associated impact on the atmospheric heating rate</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lü, Qiaoyi; Li, Jiming; Wang, Tianhe; Huang, Jianping</p> <p>2015-10-01</p> <p>A quantitative analysis of cloud fraction, cloud <span class="hlt">radiative</span> <span class="hlt">forcing</span>, and cloud <span class="hlt">radiative</span> heating rate (CRH) of the single-layered cloud (SLC) and the multi-layered cloud (MLC), and their differences is presented, based on the 2B-CLDCLASS-LIDAR and 2B-FLXHR-LIDAR products on the global scale. The CRH at a given atmospheric level is defined as the cloudy minus clear-sky <span class="hlt">radiative</span> heating rate. The statistical results show that the globally averaged cloud fraction of the MLC (24.9%), which is primarily prevalent in equatorial regions, is smaller than that of the SLC (46.6%). The globally averaged net <span class="hlt">radiative</span> <span class="hlt">forcings</span> (NET CRFs) induced by the SLC (MLC) at the top and bottom of the atmosphere (TOA and BOA) and in the atmosphere (ATM) are-60.8 (-40.9),-67.5 (-49.6), and 6.6 (8.7) W m-2, respectively, where the MLC contributes approximately 40.2%, 42.4%, and 57% to the NET CRF at the TOA, BOA, and in the ATM, respectively. The MLC exhibits distinct differences to the SLC in terms of CRH. The shortwave CRH of the SLC (MLC) reaches a heating peak at 9.75 (7.5) km, with a value of 0.35 (0.60) K day-1, and the differences between SLC and MLC transform from positive to negative with increasing altitude. However, the longwave CRH of the SLC (MLC) reaches a cooling peak at 2 (8) km, with a value of-0.45 (-0.42) K day-1, and the differences transform from negative to positive with increasing altitude. In general, the NET CRH differences between SLC and MLC are negative below 7.5 km. These results provide an observational basis for the assessment and improvement of the cloud parameterization schemes in global models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/25444720','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/25444720"><span id="translatedtitle">Repeated <span class="hlt">forced</span> swim stress has <span class="hlt">additive</span> effects in anxiety behavior and in cathecolamine levels of adult rats exposed to deltamethrin.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Habr, Soraya F; Macrini, Daclé J; Florio, Jorge C; Bernardi, Maria M</p> <p>2014-01-01</p> <p>Deltamethrin (DTM) is a type II pyrethroid insecticide that elicits autonomic and neuroendocrine responses that indicate high levels of stress, presumably caused by the neurotoxic effect of the insecticide. This study investigated the effect of DTM exposure (10 mg/kg, p.o.) and an <span class="hlt">additional</span> stress induced in the <span class="hlt">forced</span> swim test (FST) in behavioral tasks related to anxiety, serum corticosterone levels, and striatal neurotransmitter levels. Open field behavior and social interaction were evaluated after DTM administration (10 mg kg(-1), p.o). DTM per se reduced rearing frequency in the open field, but no alterations in locomotion frequency or immobility duration were detected. Stress increased immobility duration compared with non-stressed animals. DTM reduced social interaction and increased corticosterone levels, and these effects were enhanced in stressed animals. Mainly stress affected dopaminergic and serotoninergic activity. In anxiety behavior and in both neurotransmitters and metabolites levels it was observed an <span class="hlt">additive</span> effect of stress in DTM treated rat data. These results indicate that DTM enhanced the anxiogenic responses and stress had an <span class="hlt">additive</span> effect over the DTM stress. The neurochemical data did not indicate an interaction between stress and DTM exposure. The present results maybe important for implementing pyrethroid insecticide safety standards. PMID:25444720</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFM.C13D..02S&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2013AGUFM.C13D..02S&link_type=ABSTRACT"><span id="translatedtitle">Analysis of Snow Albedo, Grain Size and <span class="hlt">Radiative</span> <span class="hlt">Forcing</span> based on the Airborne Snow Observatory (ASO) Imaging Spectroscopy Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seidel, F. C.; Painter, T. H.</p> <p>2013-12-01</p> <p>Climate is expected to be most vulnerable in mountainous and arctic regions where the atmosphere and the hydrosphere are directly linked to the cryosphere. A combination of modeling and large-scale observational efforts is required to investigate related scientific questions. NASA's Airborne Snow Observatory (ASO) at the Jet Propulsion Laboratory addresses some of these needs by establishing new quantitative observational capabilities in regional mapping of mountain snow properties. In <span class="hlt">addition</span>, ASO's key products showed that we are able to achieve societal benefits by improving water resources management. We will show the first analysis of snow optical products (albedo, grain size, and <span class="hlt">radiative</span> <span class="hlt">forcing</span>) from the spring 2013 ASO campaign in the Sierra Nevada, CA, USA. In <span class="hlt">addition</span>, we will present the retrieval methods used to derive these products based on airborne imaging spectroscopy, LiDAR, as well as <span class="hlt">radiative</span> transfer models. The preliminary findings provide new important insights into the temporal and spatial aspects of Western US mountain snow and its melt.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PMB....61.5724M&link_type=ABSTRACT','NASAADS'); return false;" href="http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2016PMB....61.5724M&link_type=ABSTRACT"><span id="translatedtitle">A rapid magnetic resonance acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> imaging sequence for ultrasonic refocusing</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mougenot, Charles; Pichardo, Samuel; Engler, Steven; Waspe, Adam; Constanciel Colas, Elodie; Drake, James M.</p> <p>2016-08-01</p> <p>Magnetic resonance guided acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> imaging (MR-ARFI) is being used to correct for aberrations induced by tissue heterogeneities when using high intensity focusing ultrasound (HIFU). A compromise between published MR-ARFI adaptive solutions is proposed to achieve efficient refocusing of the ultrasound beam in under 10 min. In <span class="hlt">addition</span>, an ARFI sequence based on an EPI gradient echo sequence was used to simultaneously monitor displacement and temperature with a large SNR and low distortion. This study was conducted inside an Achieva 3T clinical MRI using a Philips Sonalleve MR-HIFU system to emit a 1 ms pulsed sonication with duty cycle of 2.3% at 300 Wac inside a polymer phantom. Virtual elements defined by a Hadamard array with sonication patterns composed of 6 phase steps were used to characterize 64 groups of 4 elements to find the optimal phase of the 256 elements of the transducer. The 384 sonication patterns were acquired in 580 s to identify the set of phases that maximize the displacement at the focal point. Three aberrators (neonatal skull, 8 year old skull and a checkered pattern) were added to each sonication pattern to evaluate the performance of this refocusing algorithm (n  =  4). These aberrators reduced the relative intensities to 95.3%, 69.6% and 25.5% for the neonatal skull, 8 year old skull, and checkered pattern virtual aberrators respectively. Using a 10 min refocusing algorithm, relative intensities of 101.6%, 91.3% and 93.3% were obtained. Better relative intensities of 103.9%, 94.3% and 101% were achieved using a 25 min refocusing algorithm. An average temperature increase of 4.2 °C per refocusing test was induced for the 10 min refocusing algorithm, resulting in a negligible thermal dose of 2 EM. A rapid refocusing of the beam can be achieved while keeping thermal effects to a minimum.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/27401452','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/27401452"><span id="translatedtitle">A rapid magnetic resonance acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> imaging sequence for ultrasonic refocusing.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mougenot, Charles; Pichardo, Samuel; Engler, Steven; Waspe, Adam; Colas, Elodie Constanciel; Drake, James M</p> <p>2016-08-01</p> <p>Magnetic resonance guided acoustic <span class="hlt">radiation</span> <span class="hlt">force</span> imaging (MR-ARFI) is being used to correct for aberrations induced by tissue heterogeneities when using high intensity focusing ultrasound (HIFU). A compromise between published MR-ARFI adaptive solutions is proposed to achieve efficient refocusing of the ultrasound beam in under 10 min. In <span class="hlt">addition</span>, an ARFI sequence based on an EPI gradient echo sequence was used to simultaneously monitor displacement and temperature with a large SNR and low distortion. This study was conducted inside an Achieva 3T clinical MRI using a Philips Sonalleve MR-HIFU system to emit a 1 ms pulsed sonication with duty cycle of 2.3% at 300 Wac inside a polymer phantom. Virtual elements defined by a Hadamard array with sonication patterns composed of 6 phase steps were used to characterize 64 groups of 4 elements to find the optimal phase of the 256 elements of the transducer. The 384 sonication patterns were acquired in 580 s to identify the set of phases that maximize the displacement at the focal point. Three aberrators (neonatal skull, 8 year old skull and a checkered pattern) were added to each sonication pattern to evaluate the performance of this refocusing algorithm (n  =  4). These aberrators reduced the relative intensities to 95.3%, 69.6% and 25.5% for the neonatal skull, 8 year old skull, and checkered pattern virtual aberrators respectively. Using a 10 min refocusing algorithm, relative intensities of 101.6%, 91.3% and 93.3% were obtained. Better relative intensities of 103.9%, 94.3% and 101% were achieved using a 25 min refocusing algorithm. An average temperature increase of 4.2 °C per refocusing test was induced for the 10 min refocusing algorithm, resulting in a negligible thermal dose of 2 EM. A rapid refocusing of the beam can be achieved while keeping thermal effects to a minimum. PMID:27401452</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/biblio/1072881','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/biblio/1072881"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">forcing</span> of the direct aerosol effect from AeroCom Phase II simulations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>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.</p> <p>2013-01-01</p> <p>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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> (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 <span class="hlt">addition</span> 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<sup>-2</sup>, with a mean of -0.27 Wm<sup>-2</sup> 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<sup>-2</sup>. 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010488','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010488"><span id="translatedtitle"><span class="hlt">Radiative</span> <span class="hlt">Forcing</span> of the Direct Aerosol Effect from AeroCom Phase II Simulations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>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.</p> <p>2013-01-01</p> <p>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 <span class="hlt">radiative</span> <span class="hlt">forcing</span> (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 <span class="hlt">addition</span> 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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ncbi.nlm.nih.gov/pubmed/17458510','PUBMED'); return false;" href="http://www.ncbi.nlm.nih.gov/pubmed/17458510"><span id="translatedtitle">Aerosol characteristics and surface <span class="hlt">radiative</span> <span class="hlt">forcing</span> components during a dust outbreak in Gwangju, Republic of Korea.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ogunjobi, K O; Kim, Y J</p> <p>2008-02-01</p> <p>Atmospheric surface aerosol <span class="hlt">radiative</span> <span class="hlt">forcing</span> (SARF) DeltaF, <span class="hlt">forcing</span> efficiency DeltaF(e) and fractional <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> 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 <span class="hlt">forcing</span> efficiency DeltaFDF(e) were -15.8 +/- 0.64%/tau (501 nm) an