WorldWideScience

Sample records for aerosol radiative forcing

  1. Factors Affecting Aerosol Radiative Forcing

    Science.gov (United States)

    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

  2. Sensitivity of aerosol direct radiative forcing to aerosol vertical profile

    OpenAIRE

    Chung, Chul E.; Choi, Jung-Ok

    2014-01-01

    Aerosol vertical profile significantly affects the aerosol direct radiative forcing at the TOA level. The degree to which the aerosol profile impacts the aerosol forcing depends on many factors such as presence of cloud, surface albedo and aerosol single scattering albedo (SSA). Using a radiation model, we show that for absorbing aerosols (with an SSA of 0.7–0.8) whether aerosols are located above cloud or below induces at least one order of magnitude larger changes of the aerosol forcing tha...

  3. Direct SW aerosol radiative forcing over Portugal

    Directory of Open Access Journals (Sweden)

    D. Santos

    2008-05-01

    Full Text Available The estimation of radiative forcing due to desert dust and forest fires aerosols is a very important issue since these particles are very efficient at scattering and absorbing both short and longwave radiation. In this work, the evaluation of the aerosol radiative forcing at the top of the atmosphere over the south of Portugal is made, particularly in the regions of Évora and of Cabo da Roca.

    The radiative transfer calculations combine ground-based and satellite measurements, to estimate the top of the atmosphere direct SW aerosol radiative forcing. The method developed to retrieve the surface spectral reflectance is also presented, based on ground-based measurements of the aerosol optical properties combined with the satellite-measured radiances.

    The aerosol direct radiative effect is shown to be very sensitive to the underlying surface, since different surface spectral reflectance values may originate different forcing values. The results obtained also illustrate the importance of considering the actual aerosol properties, in this case measured by ground-based instrumentation, particularly the aerosol single scattering albedo, because different aerosol single scattering albedo values can flip the sign of the direct SW aerosol radiative forcing.

    The instantaneous direct SW aerosol radiative forcing values obtained at the top of the atmosphere are, in the majority of the cases, negative, indicating a tendency for cooling the Earth. For Desert Dust aerosols, over Évora land region, the average forcing efficiency is estimated to be −25 W/m2/AOT0.55 whereas for Cabo da Roca area, the average forcing efficiency is −46 W/m2/AOT0.55. In the presence of Forest Fire aerosols, over Cabo da Roca region, the average value of forcing efficiency is −28 W/m2/AOT0.55 and over Évora region an average value of −33 W/m2/AOT0.55 is found.

  4. Direct SW aerosol radiative forcing over Portugal

    Directory of Open Access Journals (Sweden)

    D. Santos

    2008-10-01

    Full Text Available In this work, the evaluation of the aerosol radiative forcing at the top of the atmosphere as well as at the surface over the south of Portugal is made, particularly in the regions of Évora (38°34' N, 7°54' W and of Cabo da Roca (38°46' N, 9°38' W, during years 2004 and 2005.

    The radiative transfer calculations, using the radiative transfer code Second Simulation of the Satellite Signal in the Solar Spectrum (6S, combine ground-based measurements, from Aerosol Robotic NETwork (AERONET, and satellite measurements, from MODerate Imaging Spectroradiometer (MODIS, to estimate the direct SW aerosol radiative forcing. The method developed to retrieve the surface spectral reflectance is also presented, based on ground-based measurements (AERONET of the aerosol optical properties combined with the satellite-measured radiances (MODIS.

    The instantaneous direct SW aerosol radiative forcing values obtained at the top of the atmosphere are, in the majority of the cases, negative, indicating a tendency for cooling the Earth at the top of the atmosphere. For Desert Dust aerosols, over the Évora land region, the average forcing efficiency is estimated to be −25 Wm−2/AOT0.55 whereas for the Cabo da Roca area, the average forcing efficiency is −46 Wm−2/AOT0.55. In the presence of Forest Fire aerosols, both from short and long distances, the average value of forcing efficiency at the top of the atmosphere over Cabo da Roca is found to be −28 Wm−2/AOT0.55 and, over Évora, −27 Wm−2/AOT0.55. For specific situations, discussed in this work, the average surface direct SW aerosol radiative forcing efficiency due to the Desert Dust aerosols, in Évora region, is −66 Wm−2/AOT0.55, whereas in Cabo da Roca region, the corresponding average value is −38 Wm−2/AOT0.55

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

    Directory of Open Access Journals (Sweden)

    U. Lohmann

    2010-04-01

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

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

    Directory of Open Access Journals (Sweden)

    D. Koch

    2009-11-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-09-25

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

  8. Experimental Characterization of Radiation Forcing due to Atmospheric Aerosols

    Science.gov (United States)

    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.

  9. Aerosol radiative forcing in the European Skynet Radiometers network

    Science.gov (United States)

    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

  10. Aerosol types and radiative forcing estimates over East Asia

    Science.gov (United States)

    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. Historical anthropogenic radiative forcing of changes in biogenic secondary aerosol

    Science.gov (United States)

    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.

  12. Aerosol and ozone radiative forcing 1990-2015

    Science.gov (United States)

    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.

  13. THE IMPACT OF RELATIVE HUMIDITY ON THE RADIATIVE PROPERTY AND RADIATIVE FORCING OF SULFATE AEROSOL

    Institute of Scientific and Technical Information of China (English)

    张立盛; 石广玉

    2001-01-01

    With the data of complex refractive index of sulfate aerosol, the radiative properties of the aerosol under 8 relative humidity conditions are calculated in this paper. By using the concentration distribution from two CTM models and LASG GOALS/AGCM, the radiative forcing due to hygroscopic sulfate aerosol is simulated. The results show that: (1) With the increase of relative humidity, the mass extinction coefficiency factor decreases in the shortwave spectrum: single scattering albedo keeps unchanged except for a little increase in longwave spectrum, and asymmetry factor increases in whole spectrum. (2) Larger differences occur in radiative forcing simulated by using two CTM data, and the global mean forcing is -0. 268 and -0. 816 W/m2,respectively. (3) When the impact of relative humidity on radiative property is taken into account,the distribution pattern of radiative forcing due to the wet particles is very similar to that of dry sulfate, but the forcing value decreases by 6%.

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

    OpenAIRE

    Khlystov, A.

    1998-01-01

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

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

    NARCIS (Netherlands)

    Khlystov, A.

    1998-01-01

    This thesis discusses properties of ambient aerosols in the Netherlands which are controlling the magnitude of the local aerosol radiative forcing. Anthropogenic aerosols influence climate by changing the radiative transfer through the atmosphere via two effects, one is direct and a second is indire

  16. Remote sensing of aerosol characteristics and radiative forcing in Pakistan

    International Nuclear Information System (INIS)

    This thesis investigates the aerosol characteristics over different cities of Pakistan through satellite borne sensors, namely the Total Ozone Mapping Spectrometer (TOMS), the Moderate Resolution Imaging Spectroradiometer (MODIS), and the Multi-angle Imaging Spectroradiometer (MISR), and ground-based instruments such as Aerosol Robotic Network (AERONET) and GRIMM 1.109 dust monitor. A Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model was used for trajectory analysis in order to visualize the origins of air masses and understand the spatio-temporal variability of aerosol concentrations. An assessment of seasonal variability in aerosol optical depth (AOD) for industrial, urban, semi-urban, rural, and semi-arid areas revealed maximum AOD values during summer over all the areas under investigation. The correlation between AERONET and MODIS/MISR AODs during 2007 was also analyzed for Karachi and Lahore. The correlation coefficient for Karachi was found to be relatively high between AERONET and MISR and lower between AERONET and MODIS. In contrast, the correlation coefficient for Lahore was higher between AERONET and MODIS than between AERONET and MISR. The results suggest that the MISR sensor provides better AOD estimates near the ocean while AOD estimates from the MODIS sensor are better over terrestrial regions (especially over vegetated surfaces). The assessment of aerosol optical properties and aerosol radiative forcing (ARF) through the ground-based Aerosol Robotic Network (AERONET) over Lahore and Karachi has also been investigated in this study. The monthly mean of AOD at 500 nm over Lahore and Karachi ranges from 0.39 to 0.76, and the monthly mean Angstrom Exponent ranges from 0.29 to 1.22. The relationship between the Absorption Angstrom Exponent and the Extinction Angstrom Exponent provided an indication of relative proportions of urban-industrial and mineral dust aerosols over both sites. The single scattering albedo (SSA) ranged from 0

  17. Direct Radiative Forcing of Anthropogenic Aerosols over Oceans from Satellite Observations

    Institute of Scientific and Technical Information of China (English)

    CHEN Lin; SHI Guangyu; QIN Shiguang; YANG Su; ZHANG Peng

    2011-01-01

    Anthropogenic aerosols play an important role in the atmospheric energy balance. Anthropogenic aerosol optical depth (AOD) and its accompanying shortwave radiative forcing (RF) are usually simulated by numerical models. Recently, with the development of space-borne instruments and sophisticated retrieval algorithms, it has become possible to estimate aerosol radiative forcing based on satellite observations. In this study, we have estimated shortwave direct radiative forcing due to anthropogenic aerosols over oceans in all-sky conditions by combining clouds and the Single Scanner Footprint data of the Clouds and Earth's Radiant Energy System (CERES/SSF) experiment, which provide measurements of upward shortwave fluxes at the top of atmosphere, with Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol and cloud products. We found that globally averaged aerosol radiative forcing over oceans in the clear-sky conditions and all-sky conditions were -1.03±0.48 W m-2 and -0.34 ±0.16 W m-2, respectively. Direct radiative forcing by anthropogenic aerosols shows large regional and seasonal variations. In some regions and in particular seasons, the magnitude of direct forcing by anthropogenic aerosols can be comparable to the forcing of greenhouse gases. However, it shows that aerosols caused the cooling effect, rather than warming effect from global scale, which is different from greenhouse gases.

  18. Ground-based measurements of aerosol optical properties and radiative forcing in North China

    Institute of Scientific and Technical Information of China (English)

    Hongbin Chen; Xiangao Xia; Pucai Wang; Wenxing Zhang

    2007-01-01

    In order to gain an insight into the aerosol properties and their climatic effect over the continental source regions of China, it is of significance to carry out long-term ground-based measurements of aerosol optical properties and radiative forcing. A couple of temporary and permanent Aerosol Robotic Network (AERONET) sites and three comprehensive radiative sites were established in China as a result of international cooperation in recent years. Heavy aerosol loading and significant temporal and spatial variation over North China are revealed by the AERONET data.Aerosol-induced reductions in surface radiation budget are examined on the basis of collocated observations by sun photometers and pyranometers.

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

    Directory of Open Access Journals (Sweden)

    F. Yu

    2012-12-01

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

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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 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).

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

    Science.gov (United States)

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

    2000-01-01

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

  3. Study of Radiative Forcing of Dust Aerosols and its impact on Climate Characteristics

    KAUST Repository

    Qureshi, Fawwad H

    2012-12-01

    The purpose of following project is to study the effect of dust aerosols on the radiative forcing which is directly related to the surface temperature. A single column radiative convective model is used for simulation purpose. A series of simulations have been performed by varying the amount of dust aerosols present in the atmosphere to study the trends in ground temperature, heating rate and radiative forcing for both its longwave and shortwave components. A case study for dust storm is also performed as dust storms are common in Arabian Peninsula. A sensitivity analyses is also performed to study the relationship of surface temperature minimum and maximum against aerosol concentration, single scattering albedo and asymmetry factor. These analyses are performed to get more insight into the role of dust aerosols on radiative forcing.

  4. Implications of multiple scattering on the assessment of black carbon aerosol radiative forcing

    International Nuclear Information System (INIS)

    The effects of radiative coupling between scattering and absorbing aerosols, in an external mixture, on the aerosol radiative forcing (ARF) due to black carbon (BC), its sensitivity to the composite aerosol loading and composition, and surface reflectance are investigated using radiative transfer model simulations. The ARF due to BC is found to depend significantly on the optical properties of the ‘neighboring’ (non-BC) aerosol species. The scattering due to these species significantly increases the top of the atmospheric warming due to black carbon aerosols, and significant changes in the radiative forcing efficiency of BC. This is especially significant over dark surfaces (such as oceans), despite the ARF due to BC being higher over snow and land-surfaces. The spatial heterogeneity of this effect (coupling or multiple scattering by neighboring aerosol species) imposes large uncertainty in the estimation ARF due to BC aerosols, especially over the oceans. - Highlights: • Non-BC aerosol scattering in an external mixture increases TOA warming due to BC. • Effect of multiple scattering on BC ARF increases with total aerosol optical depth. • Contribution of multiple scattering on BC ARF is higher over oceans than over land

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2011-12-01

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

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

    Directory of Open Access Journals (Sweden)

    D. G. Streets

    2012-04-01

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

  8. Modeling Study of the Global Distribution of Radiative Forcing by Dust Aerosol

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hua; MA Jinghui; ZHENG Youfei

    2010-01-01

    To quantitatively understand the dust aerosol effects on climate change, we calculated the global dis-tribution of direct radiative forcing due to dust aerosol under clear and cloudy skies in both winter and summer, by using an improved radiative transfer model and the global distribution of dust mass concentra-tion given by GADS (Global Aerosol Data Set). The results show that the global means of the solar forcing due to dust aerosol at the tropopause for winter and summer are -0.48 and -0.50 W m-2, respectively; the corresponding values for the longwave forcing due to dust are 0.11 and 0.09 W m-2, respectively. At the surface, the global means of the solar forcing clue to dust are -1.36 W m-2 for winter and -1.56 W m-2 for summer, whereas the corresponding values for the longwave forcing are 0.27 and 0.23 W m-2, respectively. This work points out that the absolute values of the solar forcing due to dust aerosol at both the tropopause and surface increase linearly with the cosine of solar zenith angle and surface albedo. The solar zenith angle influences both the strength and distribution of the solar forcing greatly. Clouds exert great effects on the direct radiative forcing of dust, depending on many factors including cloud cover, cloud height, cloud water path, surface albedo, solar zenith angle, etc. The effects of low clouds and middle clouds are larger than those of high clouds. The existence of clouds reduces the longwave radiative forcing at the tropopause, where the influences of low clouds are the most obvious. Therefore, the impacts of clouds should not be ignored when estimating the direct radiative forcing due to dust aerosol.

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

    Science.gov (United States)

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

    2016-05-01

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

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

    Science.gov (United States)

    Srivastava, R.; Ramachandran, S.

    2012-12-01

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

  11. Monthly-averaged anthropogenic aerosol direct radiative forcing over the Mediterranean from AERONET derived aerosol properties

    OpenAIRE

    Bergamo, A.; A. M. Tafuro; Kinne, S.; De Tomasi, F.; Perrone, M. R.

    2008-01-01

    The all-sky direct radiative effect by anthropogenic aerosol (DREa) is calculated in the solar (0.3–4 μm) and infrared (4–200 μm) spectral ranges for six Mediterranean sites. The sites are differently affected by pollution and together reflect typical aerosol impacts that are expected over land sites of the central Mediterranean basin. Central to the simulations are aerosol optical properties from AERONET sun-/sky-photometer statistics for the year 2003. A discussion on the variability of the...

  12. Monthly-averaged anthropogenic aerosol direct radiative forcing over the Mediterranean based on AERONET aerosol properties

    OpenAIRE

    Bergamo, A.; A. M. Tafuro; Kinne, S.; De Tomasi, F.; Perrone, M. R.

    2008-01-01

    The all-sky direct radiative effect by anthropogenic aerosol (DREa) is calculated in the solar (0.3–4 μm) and infrared (4–200 μm) spectral ranges for six Mediterranean sites. The sites are differently affected by pollution and together reflect typical aerosol impacts that are expected over land and coastal sites of the central Mediterranean basin. Central to the simulations are aerosol optical properties from AERONET sun-/sky-photometer statistics for the year 2003. A d...

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2015-11-01

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

  15. Aerosol and cloud forcing on surface reaching solar radiation over different stations in India

    Science.gov (United States)

    Kumari B., Padma; N, Goswami B.

    2010-05-01

    Surface reaching solar radiation (S) is a key component of the net radiation balance at the surface determining the regional climate. Reduction in S called solar dimming is probably due to the increased presence of aerosols in the atmosphere, caused by both natural and human activities, and clouds. But, the processes involved in aerosol-cloud-radiation interactions have not yet been fully understood. Daily mean surface reaching solar radiation (S) and sunshine duration (SD) data over 12 different stations (Trivandrum, Chennai, Goa, Visakhapatnam, Pune, Mumbai, Nagpur, Kolkatta, Ahmedabad, Varanasi, Jodhpur, and New Delhi), which are widely distributed over the Indian region, have been evaluated for the period 1981- 2006. Annual mean sunshine duration under all sky conditions showed drastic decrease over all stations with an average reduction of ~ 0.34 h/decade. Daily mean S data has been segregated into clear and cloudy sky composites and annual means have been computed. All the stations showed decreasing trends under both clear sky (except two stations Chennai and Pune) and cloudy sky conditions. Aerosol forcing dominated over trends in cloud forcing at Kolkatta, equally contributed at stations New Delhi, Varanasi and Goa, and over all other stations cloud forcing dominated over trends in aerosol forcing resulting in a net decrease in surface solar radiation. The solar dimming (averaged over all 12 stations) under all sky conditions is ~ 9 W/m2 per decade, under clear sky conditions it is ~ 6 W/m2 per decade and under cloudy sky conditions it is almost double, ~ 12 W/m2 per decade. The interaction between aerosol and cloud complicate to understand their separate effects on radiation. However, in the present study efforts are being made to understand the climatic effects of aerosols and clouds separately on the surface reaching solar radiation.

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

    Science.gov (United States)

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

    2006-11-01

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

  17. The Impacts of Optical Properties on Radiative Forcing Due to Dust Aerosol

    Institute of Scientific and Technical Information of China (English)

    WANG Hong; SHI Guangyu; LI Shuyan; LI Wei; WANG Biao; HUANG Yanbin

    2006-01-01

    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.

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

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    H. Yu

    2006-01-01

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

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

    Science.gov (United States)

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

    2013-01-01

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

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

    Directory of Open Access Journals (Sweden)

    G. E. Thomas

    2012-07-01

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

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

    Directory of Open Access Journals (Sweden)

    G. E. Thomas

    2013-01-01

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

  3. Brown carbon aerosol in the North American continental troposphere: sources, abundance, and radiative forcing

    Science.gov (United States)

    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.

    2015-07-01

    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 radiative transfer model showed that BrC absorption reduced top-of-atmosphere (TOA) aerosol forcing by ~ 20 % in the background troposphere. Extensive radiative model simulations applying this study background tropospheric conditions provided a look-up chart for determining radiative forcing 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 forcing effect when one is limited to only surface data. These results indicate that BrC is an important contributor to direct aerosol radiative forcing.

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

    Directory of Open Access Journals (Sweden)

    M. A. Pfeffer

    2011-10-01

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

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

    Directory of Open Access Journals (Sweden)

    A. Schmidt

    2012-03-01

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

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

    Directory of Open Access Journals (Sweden)

    D. M. Westervelt

    2015-03-01

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

  7. Monthly-averaged anthropogenic aerosol direct radiative forcing over the Mediterranean based on AERONET aerosol properties

    Directory of Open Access Journals (Sweden)

    A. Bergamo

    2008-12-01

    Full Text Available The all-sky direct radiative effect by anthropogenic aerosol (DREa is calculated in the solar (0.3–4 μm and infrared (4–200 μm spectral ranges for six Mediterranean sites. The sites are differently affected by pollution and together reflect typical aerosol impacts that are expected over land and coastal sites of the central Mediterranean basin. Central to the simulations are aerosol optical properties from AERONET sun-/sky-photometer statistics for the year 2003. A discussion on the variability of the overall (natural + anthropogenic aerosol properties with site location is provided. Supplementary data include MODIS satellite sensor based solar surface albedos, ISCCP products for high- mid- and low cloud cover and estimates for the anthropogenic aerosol fraction from global aerosol models. Since anthropogenic aerosol particles are considered to be smaller than 1 μm in size, mainly the solar radiation transfer is affected with impacts only during sun-light hours. At all sites the (daily average solar DREa is negative all year round at the top of the atmosphere (ToA. Hence, anthropogenic particles produce over coastal and land sites of the central Mediterranean a significant cooling effect. Monthly DREa values vary from site to site and are seasonally dependent as a consequence of the seasonal dependence of available sun-light and microphysical aerosol properties. At the ToA the monthly average DREa is −(4±1 W m−2 during spring-summer (SS, April–September and −(2±1 W m−2 during autumn-winter (AW, October–March at the polluted sites. In contrast, it varies between −(3±1 W m−2 and −(1±1 W m−2 on SS and AW, respectively at the less polluted site. Due to atmospheric absorption the DREa at the surface is larger than at the ToA. At the surface the monthly average DREa varies between the most and the least polluted

  8. Monthly-averaged anthropogenic aerosol direct radiative forcing over the Mediterranean from AERONET derived aerosol properties

    Directory of Open Access Journals (Sweden)

    A. Bergamo

    2008-07-01

    Full Text Available The all-sky direct radiative effect by anthropogenic aerosol (DREa is calculated in the solar (0.3–4 μm and infrared (4–200 μm spectral ranges for six Mediterranean sites. The sites are differently affected by pollution and together reflect typical aerosol impacts that are expected over land sites of the central Mediterranean basin. Central to the simulations are aerosol optical properties from AERONET sun-/sky-photometer statistics for the year 2003. A discussion on the variability of the overall (natural+anthropogenic aerosol properties with site location is provided. Supplementary data include MODIS satellite sensor based solar surface albedos, ISCCP products for high- mid- and low cloud cover and estimates for the anthropogenic aerosol fraction from global modelling. Since anthropogenic aerosol particles are considered to be smaller than 1 μm in size, mainly the solar radiation transfer is affected with impacts only during sun-light hours. At all sites the (daily average solar DREa is negative all year round at the top of the atmosphere (ToA. Hence, anthropogenic particles produce over land sites of the central Mediterranean a significant cooling effect. Monthly DREa values vary from site to site and are seasonal dependent as a consequence of the seasonal dependence of available sun-light and microphysical aerosol properties. At the ToA the monthly average DREa is −(4±1 W m−2 during spring-summer (SS, April–September and −(2±1 W m−2 during autumn-winter (AW, October–March at the polluted sites. In contrast, it varies between −(3±1 W m−2 and −(1±1 W m−2 on SS and AW, respectively at the less polluted site. Due to atmospheric absorption the DREa at the surface is larger than at the ToA. At the surface the monthly average DREa varies between the most and the least polluted site between −(7±1 W m−2 and

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

    KAUST Repository

    Brindley, Helen

    2015-04-01

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

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

    Science.gov (United States)

    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.

  11. Is the radiative forcing due to black carbon aerosols as large as some recent studies suggest?

    Science.gov (United States)

    Boucher, O.; Wang, R.; Balkanski, Y.; Tao, S.; Myhre, G.; Valari, M.; Huneeus, N.

    2013-12-01

    Anthropogenic black carbon aerosols is responsible for a radiative forcing due to aerosol-radiation interactions (RFari), aerosol-cloud interactions (RFaci) and aerosol-snow interactions (RFasi). All estimates are very uncertain but some recent studies (e.g. Chung et al., 2012; Bond et al., 2013) have suggested that global models significantly underestimate aerosol absorption and have applied scaling factors to correct for this underestimation. As a result Bond et al. estimate RFari to be +0.5 (+0.1 to +0.9) Wm-2 for fossil fuel and biofuel only. The fifth assessment report adopted an estimate of +0.4 (+0.05 to +0.8) Wm-2. In this presentation we will show that a number of factors are likely to lead to overestimate the discrepancy in aerosol absorption between observations and models, which questions the need for very large scaling factors to reconcile models with observations. Issues with past methodological include a too small correction for NO2 absorption in AERONET retrievals of aerosol absorption optical depth (AAOD) at 440 nm, representativity errors when comparing outputs from global models with AERONET retrievals, and model biases in aerosol vertical profiles. We will show in particular how a new emission inventory and high-resolution aerosol modelling over Asia can resolve a significant fraction of the discrepancy with observations. Bond, T. C., et al., 2013: Bounding the role of black carbon in the climate system: A scientific assessment. Journal of Geophysical Research, 118, 5380-5552, doi:10.1002/jgrd.50171. Chung, C. E., V. Ramanathan, and D. Decremer, 2012: Observationally constrained estimates of carbonaceous aerosol radiative forcing. Proceedings of the National Academy of Sciences of the United States of America, 109, 11624-11629 Geographic distributions of BC emission density (A, MACCity; B, PKU-BC), modeled surface BC concentrations (C, by MACCity/INCA; D, by PKU-BC/INCA-zA), and modeled BC AAOD (E, by MACCity/INCA; F, by PKU-BC/INCA-zA). The

  12. An Energetic Perspective on Aerosol Radiative Forcing and Interactions with Atmospheric Wave Activity

    Science.gov (United States)

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

    2014-12-01

    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 forcing 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 radiative forcing may act as additional 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.

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

    Science.gov (United States)

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

    2015-10-01

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

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

    Science.gov (United States)

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

    2007-12-01

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

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Directory of Open Access Journals (Sweden)

    S. D. D'Andrea

    2014-10-01

    +0.163 W m−2 and the global mean cloud-albedo aerosol indirect effect of between −0.008 and −0.056 W m−2. This change in aerosols, and the associated radiative forcing, could be a~largely overlooked and important anthropogenic aerosol effect on regional climates.

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

    Directory of Open Access Journals (Sweden)

    O. E. García

    2012-06-01

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

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

    Science.gov (United States)

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

    2008-01-01

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

  19. Direct radiative forcing of aerosols over a typical tropical urban environment

    International Nuclear Information System (INIS)

    Aerosols reduce the surface reaching solar flux by scattering the incoming solar radiation out to space. Various model studies on climate change suggest that surface cooling induced by aerosol scattering is the largest source of uncertainty in predicting the future climate. In the present study measurements of aerosol optical depth (AOD) and its direct radiative forcing efficiency has been presented over a typical tropical urban environment namely Hyderabad during 2001 and 2002. Diurnal variation of AOD suggesting that AOD is high during afternoon hours. AOD decreases with increase in wavelength, i.e. maximum AOD observed at 380 nm. Average monthly variation of AOD at different wavelengths observed to be minimum in January, moderately high in February to March, maximum in April and decreasing in May. AOD has been observed to be high during 2002 compared to 2001. AOD showed positive correlation with air temperature and negative correlation with rainfall. A statistical fit between AOD (500 nm) and photosynthetic active radiation (PAR which is in the range of 400-700 nm solar spectrum) shows negative correlation. The present study suggests -23 W m-2 reduction in the ground reaching solar flux for every 0.1 increase in aerosol optical depth over the study area. (author)

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

    Directory of Open Access Journals (Sweden)

    L. Zhu

    2012-06-01

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

  1. Radiative forcing due to dust aerosol over east Asia-north Pacific region during spring,2001

    Institute of Scientific and Technical Information of China (English)

    WANG Hong; SHI Guangyu; Aoki Teruo; WANG Biao; ZHAO Tianliang

    2004-01-01

    An optical model accounting for the East Asian dust is proposed as a result of theory calculation and composition analysis of the aerosol samples collected in China desert during the international project, "Studies on the Origin and Transport of Aeolian Dust and its Effects on Climate (ADEC)". Study indicates that dust aerosols emitting from China deserts have smaller imaginary parts of refractive indices, therefore absorb less and scatter more solar radiation than the most dust optical models published so far. Furthermore, the forward fraction of scattering is less and the backscattering is stronger than those of the other models. The seasonal averaged radiative forcing in spring, 2001 over east Asia-north Pacific region is simulated employing the new dust optical model. The net forcing at the top of atmosphere (TOA) is estimated as -0.943 W·m-2 for regional and seasonal mean, with shortwave and longwave contributions of -1.700 and 0.759 W·m-2, respectively. The surface net forcing is calculated to be -5.445 W·m-2, and made up of shortwave component of -6.250 W·m-2 and longwave component of +0.759 W·m-2. The distributions of TOA and surface net forcing over this region are also analyzed in this study.

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

    Science.gov (United States)

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

    2012-03-01

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Myhre, G.; Samset, B. H.; Schulz, M.; Balkanski, Y.; Bauer, S.; Berntsen, T. K.; Bian, H.; Bellouin, N.; Chin, M.; Diehl, T.; Easter, R. C.; Feichter, J.; Ghan, S. J.; Hauglustaine, D.; Iversen, T.; Kinne, S.; Kirkevag, A.; Lamarque, J.-F.; Lin, G.; Liu, X.; Lund, M. T.; Luo, G.; Ma, X.; vanNoije, T.; Penner, J. E.; Rasch, P. J.; Ruiz, A.; Seland, O.; Skeie, R. B.; Stier, P.; Takemura, T.; Tsigaridis, K.; Wang, P.; Wang, Z.; Xu, L.; Yu, H.; Yu, F.; Yoon, J. -H.; Zhang, K.; Zhang, H.; Zhou, C.

    2013-01-01

    We report on the AeroCom Phase II direct aerosol effect (DAE) experiment where 16 detailed global aerosol models have been used to simulate the changes in the aerosol distribution over the industrial era. All 16 models have estimated the radiative forcing (RF) of the anthropogenic DAE, and have taken into account anthropogenic sulphate, black carbon (BC) and organic aerosols (OA) from fossil fuel, biofuel, and biomass burning emissions. In addition several models have simulated the DAE of anthropogenic nitrate and anthropogenic influenced secondary organic aerosols (SOA). The model simulated all-sky RF of the DAE from total anthropogenic aerosols has a range from -0.58 to -0.02 W m(sup-2), with a mean of -0.27 W m(sup-2 for the 16 models. Several models did not include nitrate or SOA and modifying the estimate by accounting for this with information slightly strengthens the mean. Modifying the model estimates for missing aerosol components and for the time period 1750 to 2010 results in a mean RF for the DAE of -0.35 W m(sup-2). Compared to AeroCom Phase I (Schulz et al., 2006) we find very similar spreads in both total DAE and aerosol component RF. However, the RF of the total DAE is stronger negative and RF from BC from fossil fuel and biofuel emissions are stronger positive in the present study than in the previous AeroCom study.We find a tendency for models having a strong (positive) BC RF to also have strong (negative) sulphate or OA RF. This relationship leads to smaller uncertainty in the total RF of the DAE compared to the RF of the sum of the individual aerosol components. The spread in results for the individual aerosol components is substantial, and can be divided into diversities in burden, mass extinction coefficient (MEC), and normalized RF with respect to AOD. We find that these three factors give similar contributions to the spread in results

  5. Impact of Two Intense Dust Storms on Aerosol Characteristics and Radiative Forcing over Patiala, Northwestern India

    Directory of Open Access Journals (Sweden)

    Deepti Sharma

    2012-01-01

    Full Text Available Impact of dust storms on the aerosol characteristics and radiative forcing over Patiala, northwestern India has been studied during April-June of 2010 using satellite observations and ground-based measurements. Six dust events (DE have been identified during the study period with average values of Aqua-MODIS AOD550 and Microtops-II AOD500 over Patiala as 1.00±0.51 and 0.84±0.41, respectively while Aura-OMI AI exhibits high values ranging from 2.01 to 6.74. The Ångström coefficients α380–870 and β range from 0.12 to 0.31 and 0.95 to 1.40, respectively. The measured spectral AODs, the OPAC-derived aerosol properties and the surface albedo obtained from MODIS were used as main inputs in SBDART model for the calculation of aerosol radiative forcing (ARF over Patiala. The ARF at surface (SRF and top of atmosphere (TOA ranges from ∼−50 to −100 Wm−2 and from ∼−10 to −25 Wm−2, respectively during the maximum of dust storms. The radiative forcing efficiency was found to be −66 Wm−2AOD−1 at SRF and −14 Wm−2AOD−1 at TOA. High values of ARF in the atmosphere (ATM, ranging between ∼+40 Wm−2 and +80.0 Wm−2 during the DE days, might have significant effect on the warming of the lower and middle atmosphere and, hence, on climate over northwestern India.

  6. Model Assessment of the Ability of MODIS to Measure Top-of-Atmosphere Direct Radiative Forcing from Smoke Aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Remer, L. A.; Kaufman, Yoram J.; Levin, Zev; Ghan, Steven J.

    2002-02-01

    The new generation of satellite sensors such as the MODerate resolution Imaging Spectroradiometer (MODIS) will be able to detect and characterize global aerosols with an unprecedented accuracy. The question remains whether this accuracy will be sufficient to narrow the uncertainties in our estimates of aerosol radiative forcing at the top of the atmosphere. We narrow the discussion to cloud free direct forcing. Satellite remote sensing detects aerosol optical thickness with the least amount of relative error when aerosol loading is high. Satellites are less effective when aerosol loading is low. We use the monthly mean results of two global aerosol transport models to simulate the spatial distribution of smoke aerosol in the Southern Hemisphere during the tropical biomass burning season. This spatial distribution allows us to determine that 87-94% of the smoke aerosol forcing at the top of the atmosphere occurs in grid squares with sufficient signal to noise ratio to be detectable from space. The uncertainty of quantifying the smoke aerosol forcing in the Southern Hemisphere depends on the uncertainty introduced by errors in estimating the background aerosol, errors resulting from uncertainties in surface properties and errors resulting from uncertainties in assumptions of aerosol properties. These three errors combine to give overall uncertainties of 1.2 to 2.2 Wm-2 (16-60%) in determining the Southern Hemisphere smoke aerosol forcing at the top of the atmosphere. The range of values depend on which estimate of MODIS retrieval uncertainty is used, either the theoretical calculation (upper bound) or the empirical estimate (lower bound). Strategies that use the satellite data to derive flux directly or use the data in conjunction with ground-based remote sensing and aerosol transport models can reduce these uncertainties.

  7. Carbonaceous aerosols and pollutants over Delhi urban environment: Temporal evolution, source apportionment and radiative forcing

    International Nuclear Information System (INIS)

    Particulate matter (PM2.5) samples were collected over Delhi, India during January to December 2012 and analysed for carbonaceous aerosols and inorganic ions (SO42− and NO3−) in order to examine variations in atmospheric chemistry, combustion sources and influence of long-range transport. The PM2.5 samples are measured (offline) via medium volume air samplers and analysed gravimetrically for carbonaceous (organic carbon, OC; elemental carbon, EC) aerosols and inorganic ions (SO42− and NO3−). Furthermore, continuous (online) measurements of PM2.5 (via Beta-attenuation analyser), black carbon (BC) mass concentration (via Magee scientific Aethalometer) and carbon monoxide (via CO-analyser) are carried out. PM2.5 (online) range from 18.2 to 500.6 μg m−3 (annual mean of 124.6 ± 87.9 μg m−3) exhibiting higher night-time (129.4 μg m−3) than daytime (103.8 μg m−3) concentrations. The online concentrations are 38% and 28% lower than the offline during night and day, respectively. In general, larger night-time concentrations are found for the BC, OC, NO3−and SO42−, which are seasonally dependent with larger differences during late post-monsoon and winter. The high correlation (R2 = 0.74) between OC and EC along with the OC/EC of 7.09 (day time) and 4.55 (night-time), suggest significant influence of biomass-burning emissions (burning of wood and agricultural waste) as well as secondary organic aerosol formation during daytime. Concentrated weighted trajectory (CWT) analysis reveals that the potential sources for the carbonaceous aerosols and pollutants are local emissions within the urban environment and transported smoke from agricultural burning in northwest India during post-monsoon. BC radiative forcing estimates result in very high atmospheric heating rates (~ 1.8–2.0 K day−1) due to agricultural burning effects during the 2012 post-monsoon season. - Highlights: • Very high PM2.5 (> 200 µg m−3) levels over Delhi during agricultural

  8. Carbonaceous aerosols and pollutants over Delhi urban environment: Temporal evolution, source apportionment and radiative forcing

    Energy Technology Data Exchange (ETDEWEB)

    Bisht, D.S. [Indian Institute of Tropical Meteorology, New Delhi (India); Dumka, U.C., E-mail: dumka@aries.res.in [Aryabhatta Research Institute of Observational Sciences, Nainital (India); Kaskaoutis, D.G. [School of Natural Sciences, Shiv Nadar University, Tehsil Dadri (India); Pipal, A.S. [Department of Chemistry, Savitribai Phule Pune University, Pune (India); Srivastava, A.K. [Indian Institute of Tropical Meteorology, New Delhi (India); Soni, V.K.; Attri, S.D.; Sateesh, M. [India Meteorology Department, Lodhi Road, New Delhi (India); Tiwari, S. [Indian Institute of Tropical Meteorology, New Delhi (India)

    2015-07-15

    Particulate matter (PM{sub 2.5}) samples were collected over Delhi, India during January to December 2012 and analysed for carbonaceous aerosols and inorganic ions (SO{sub 4}{sup 2−} and NO{sub 3}{sup −}) in order to examine variations in atmospheric chemistry, combustion sources and influence of long-range transport. The PM{sub 2.5} samples are measured (offline) via medium volume air samplers and analysed gravimetrically for carbonaceous (organic carbon, OC; elemental carbon, EC) aerosols and inorganic ions (SO{sub 4}{sup 2−} and NO{sub 3}{sup −}). Furthermore, continuous (online) measurements of PM{sub 2.5} (via Beta-attenuation analyser), black carbon (BC) mass concentration (via Magee scientific Aethalometer) and carbon monoxide (via CO-analyser) are carried out. PM{sub 2.5} (online) range from 18.2 to 500.6 μg m{sup −3} (annual mean of 124.6 ± 87.9 μg m{sup −3}) exhibiting higher night-time (129.4 μg m{sup −3}) than daytime (103.8 μg m{sup −3}) concentrations. The online concentrations are 38% and 28% lower than the offline during night and day, respectively. In general, larger night-time concentrations are found for the BC, OC, NO{sub 3}{sup −}and SO{sub 4}{sup 2−}, which are seasonally dependent with larger differences during late post-monsoon and winter. The high correlation (R{sup 2} = 0.74) between OC and EC along with the OC/EC of 7.09 (day time) and 4.55 (night-time), suggest significant influence of biomass-burning emissions (burning of wood and agricultural waste) as well as secondary organic aerosol formation during daytime. Concentrated weighted trajectory (CWT) analysis reveals that the potential sources for the carbonaceous aerosols and pollutants are local emissions within the urban environment and transported smoke from agricultural burning in northwest India during post-monsoon. BC radiative forcing estimates result in very high atmospheric heating rates (~ 1.8–2.0 K day{sup −1}) due to agricultural burning effects

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

    Science.gov (United States)

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

    2016-09-01

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

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

    Science.gov (United States)

    Yu, Shao-Cai

    1999-01-01

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

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

    OpenAIRE

    Mallet, Marc; Dulac, François; Formenti, Paola; Nabat, Pierre; Sclare, J.; Roberts, Gregory; Pelon, Jacques; Ancellet, Gérard; Tanré, Didier; Parol, Frédéric; A. di Sarra; Alados, L.; Arndt, J.; Auriol, Frédérique; L. Blarel

    2015-01-01

    The Chemistry-Aerosol Mediterranean Experiment (ChArMEx; http://charmex.lsce.ipsl.fr) is a collaborative research program federating international activities to investigate Mediterranean regional chemistry-climate interactions. A special observing period (SOP-1a) including intensive airborne measurements was performed in the framework of the Aerosol Direct Radiative Forcing on the Mediterranean Climate (ADRIMED) project during the Mediterranean dry season over the western and central Mediterr...

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

    OpenAIRE

    M. Mallet; Dulac, F.; Formenti, P.; P. Nabat; Sciare, J; Roberts, G; Pelon, J.; G. Ancellet; Tanré, D.; F. Parol; A. di Sarra; Alados, L.; Arndt, J; F. Auriol; Blarel, L.

    2015-01-01

    The Chemistry-Aerosol Mediterranean Experiment (ChArMEx; http://charmex.lsce.ipsl.fr) is a collaborative research program federating international activities to investigate Mediterranean regional chemistry-climate interactions. A special observing period (SOP-1a) including intensive airborne measurements was performed in the framework of the Aerosol Direct Radiative Forcing on the Mediterranean Climate (ADRIMED) project during the Mediterranean dry season ove...

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

    OpenAIRE

    Mallet, Marc; DULAC, FRANÇOIS; Formenti, Paola; Nabat, Pierre; Sclare, J.; Roberts, Gregory; Pelon, Jacques; Ancellet, Gérard; Tanré, Didier; Parol, Frédéric; A. Di Sarra; L. Alados; Arndt, J; Auriol, Frédérique; Blarel, L.

    2015-01-01

    International audience The Chemistry-Aerosol Mediterranean Experiment (ChArMEx; http://charmex.lsce.ipsl.fr) is a collaborative research program federating international activities to investigate Mediterranean regional chemistry-climate interactions. A special observing period (SOP-1a) including intensive airborne measurements was performed in the framework of the Aerosol Direct Radiative Forcing on the Mediterranean Climate (ADRIMED) project during the Mediterranean dry season over the we...

  14. Aerosol shortwave direct radiative effect and forcing based on MODIS Level 2 data in the Eastern Mediterranean (Crete

    Directory of Open Access Journals (Sweden)

    N. Benas

    2011-12-01

    Full Text Available The shortwave (SW radiation budget was computed on a 10 km × 10 km resolution above FORTH-CRETE AERONET station in Crete, Greece, for the 11-year period from 2000 to 2010. The area is representative of the Eastern Mediterranean region, where air pollution and diminishing water resources are exacerbated by high aerosol loads and climate change. The present study aims to quantify the aerosol direct effect and forcing on the local surface and atmospheric energy budget. A radiative transfer model was used, with climatological data from the Moderate Resolution Imaging Spectroradiometer (MODIS, on board NASA's Terra and Aqua satellites. The instantaneous radiative fluxes were computed for satellite overpass times at the surface, within the atmosphere and at the top of atmosphere (TOA. Downward surface fluxes and aerosol input data were validated against ground measurements. Output fluxes reveal the direct radiative effects of dust events, with instantaneous values reaching up to −215, 139 and −46 Wm−2 at the surface (cooling, within the atmosphere (warming and at TOA (cooling, respectively. Mean monthly values show a decreasing trend of the aerosol direct radiative effect, in agreement with a similar trend in AOT. The analysis of the contribution of anthropogenic and natural aerosol show major peaks of natural aerosol direct effect occurring mainly in spring, while a summer maximum is attributed to anthropogenic aerosol. During their peaks, anthropogenic aerosol forcing can reach values of −24 Wm−2 at the surface, 19 Wm−2 in the atmosphere and over −4 Wm−2 at TOA (monthly mean instantaneous values. The corresponding monthly peak values for natural aerosol are over −20 Wm−2, 12 Wm−2 and −9 Wm−2.

  15. A Modeling Study of the Effects of Direct Radiative Forcing Due to Carbonaceous Aerosol on the Climate in East Asia

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hua; WANG Zhili; GUO Pinwen; WANG Zaizhi

    2009-01-01

    The study investigated the effects of global direct radiative forcing due to carbonaceous aerosol on the climate in East Asia, using the CAM3 developed by NCAR. The results showed that carbonaceous aerosols cause negative forcing at the top of the atmosphere (TOA) and surface under clear sky conditions, but positive forcing at the TOA and weak negative forcing at the surface under all sky conditions. Hence, clouds could change the sign of the direct radiative forcing at the TOA, and weaken the forcing at the surface. Carbonaceous aerosols have distinct effects on the summer climate in East Asia. In southern China and India, it caused the surface temperature to increase, but the total cloud cover and precipitation to decrease. However, the opposite effects are caused for most of northern China and Bangladesh. Given the changes in temperature, vertical velocity, and surface streamflow caused by carbonaceous aerosol in this simulation, carbonaceous aerosol could also induce summer precipitation to decrease in southern China but increase in northern China.

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

    Science.gov (United States)

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

    2005-01-01

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

  17. Analysis of Aerosol Radiative Forcing over Beijing under Different Air Quality Conditions Using Ground-Based Sun-Photometers between 2013 and 2015

    OpenAIRE

    Wei Chen; Lei Yan; Nan Ding; Mengdie Xie; Ming Lu; Fan Zhang; Yongxu Duan; Shuo Zong

    2016-01-01

    Aerosol particles can strongly affect both air quality and the radiation budget of the atmosphere. Above Beijing, the capital city of China, large amounts of aerosols within the atmospheric column have caused the deterioration of local air quality and have influenced radiative forcings at both the top and the bottom of the atmosphere (BOA and TOA). Observations of aerosol radiative forcing and its efficiency have been made using two sun-photometers in urban Beijing between 2013 and 2015, and ...

  18. Closing the Confidence Gap in Aerosol Contributions to Direct Radiative Forcing Using Space-based and Suborbital Resources

    Science.gov (United States)

    Kahn, R. A.

    2009-12-01

    As expected, the aerosol data products from the NASA Earth Observing System’s MISR and MODIS instruments provide significant advances in regional and global aerosol optical depth (AOD) mapping, aerosol type measurement, and source plume characterization from space. Although these products have been and are being used for many applications, ranging from regional air quality assessment, to aerosol air mass type evolution, to aerosol injection height and aerosol transport model validation, uncertainties still limit the quantitative constraints these satellite data place on global-scale direct aerosol radiative forcing. Some further refinement of the current aerosol products is possible, but a major advance in this area seems to require a different paradigm, involving the integration of satellite and suborbital data with models. This presentation will briefly summarize where we stand, and what incremental advances we can expect, with the current aerosol products, and will then elaborate on some initial steps aimed at the necessary integration. Many other AGU presentations, covering parts of the community’s emerging efforts in this direction, will be referenced, and key points from the recently released CCSP-SAP (US Climate Change Program - Synthesis and Assessment Product) 2.3 - Atmospheric aerosols: Properties and Climate Impacts, will be included in the discussion.

  19. Spatial variability of the direct radiative forcing of biomass burning aerosols and the effects of land use change in Amazonia

    Directory of Open Access Journals (Sweden)

    E. T. Sena

    2013-02-01

    Full Text Available This paper addresses the Amazonian shortwave radiative budget over cloud-free conditions after considering three aspects of deforestation: (i the emission of aerosols from biomass burning due to forest fires; (ii changes in surface albedo after deforestation; and (iii modifications in the column water vapour amount over deforested areas. Simultaneous Clouds and the Earth's Radiant Energy System (CERES shortwave fluxes and aerosol optical depth (AOD retrievals from the Moderate Resolution Imaging SpectroRadiometer (MODIS were analysed during the peak of the biomass burning seasons (August and September from 2000 to 2009. A discrete-ordinate radiative transfer (DISORT code was used to extend instantaneous remote sensing radiative forcing assessments into 24-h averages.

    The mean direct radiative forcing of aerosols at the top of the atmosphere (TOA during the biomass burning season for the 10-yr studied period was −5.6 ± 1.7 W m−2. Furthermore, the spatial distribution of the direct radiative forcing of aerosols over Amazonia was obtained for the biomass burning season of each year. It was observed that for high AOD (larger than 1 at 550 nm the maximum daily direct aerosol radiative forcing at the TOA may be as high as −20 W m−2 locally. The surface reflectance plays a major role in the aerosol direct radiative effect. The study of the effects of biomass burning aerosols over different surface types shows that the direct radiative forcing is systematically more negative over forest than over savannah-like covered areas. Values of −15.7 ± 2.4 W m−2τ550 nm and −9.3 ± 1.7 W m−2τ550 nm were calculated for the mean daily aerosol forcing efficiencies over forest and savannah-like vegetation respectively. The overall mean annual land use change radiative forcing due to deforestation over the state of Rondônia, Brazil, was determined as −7.3 ± 0.9 W m

  20. Aerosol shortwave daily radiative effect and forcing based on MODIS Level 2 data in the Eastern Mediterranean (Crete

    Directory of Open Access Journals (Sweden)

    N. Benas

    2011-07-01

    Full Text Available The mean daily shortwave (SW radiation budget was computed on a 10 km × 10 km resolution above FORTH-CRETE AERONET station in Crete, Greece, for the 9-yr period from 2000 to 2008. The area is representative of the Eastern Mediterranean region, where air pollution and diminishing water resources are exacerbated by high aerosol loads and climate change. The present study aims to quantify the aerosol direct effect and forcing on the local energy budget. A radiative transfer model was used, with daily climatological data from the Moderate Resolution Imaging Spectroradiometer (MODIS, on board NASA's Terra and Aqua satellites. The radiative fluxes were computed at the surface, within the atmosphere and at the top of atmosphere (TOA. Downward surface fluxes and aerosol optical thickness (AOT were validated against ground measurements. Daily fluxes reveal the direct radiative effects of dust events, with mean daily values reaching up to −100, 55 and −30 W m−2 at the surface (cooling, within the atmosphere (warming and at TOA (cooling, respectively. Mean monthly values show a decreasing trend of the aerosol direct radiative effect, in agreement with a similar trend in AOT. The analysis of the contribution of anthropogenic and natural aerosol show major peaks of natural aerosol direct effect occurring mainly in spring, while a summer maximum is attributed to anthropogenic aerosol. During their peaks, anthropogenic aerosol forcing can reach values of −15 W m−2 at the surface, 8 W m−2 in the atmosphere and over −4 W m−2 at TOA (monthly mean values. The corresponding daily peak values for natural aerosol are over −10 W m−2, 6 W m−2 and −3 W m−2. Annual mean values and standard deviations (interannual variability of anthropogenic aerosol forcing are −10 ± 3 W m−2 at the surface, 5 ± 1 W m−2 in the atmosphere and −3 ± 1 W m

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

    Science.gov (United States)

    Goren, Tom; Rosenfeld, Daniel

    2015-06-01

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

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

    Directory of Open Access Journals (Sweden)

    L. Zhu

    2012-12-01

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

    Compared to traditional approaches, MEVA also improves the accuracy of the outgoing solar flux between 0.3 to 2.5 μm at TOA by over 60 W m−2 (for aspen 3 surface and aerosol DRF by over 10 W m−2 (for dry grass. Specifically, for Amazon vegetation types, MEVA can improve the accuracy of daily averaged aerosol radiative forcing in the spectral range of 0.3 to 2.5 μm at

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

    Science.gov (United States)

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

    2012-01-01

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

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

    Science.gov (United States)

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

    2012-12-01

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

  5. Carbonaceous aerosols and pollutants over Delhi urban environment: Temporal evolution, source apportionment and radiative forcing.

    Science.gov (United States)

    Bisht, D S; Dumka, U C; Kaskaoutis, D G; Pipal, A S; Srivastava, A K; Soni, V K; Attri, S D; Sateesh, M; Tiwari, S

    2015-07-15

    Particulate matter (PM2.5) samples were collected over Delhi, India during January to December 2012 and analysed for carbonaceous aerosols and inorganic ions (SO4(2-) and NO3(-)) in order to examine variations in atmospheric chemistry, combustion sources and influence of long-range transport. The PM2.5 samples are measured (offline) via medium volume air samplers and analysed gravimetrically for carbonaceous (organic carbon, OC; elemental carbon, EC) aerosols and inorganic ions (SO4(2-) and NO3(-)). Furthermore, continuous (online) measurements of PM2.5 (via Beta-attenuation analyser), black carbon (BC) mass concentration (via Magee scientific Aethalometer) and carbon monoxide (via CO-analyser) are carried out. PM2.5 (online) range from 18.2 to 500.6μgm(-3) (annual mean of 124.6±87.9μgm(-3)) exhibiting higher night-time (129.4μgm(-3)) than daytime (103.8μgm(-3)) concentrations. The online concentrations are 38% and 28% lower than the offline during night and day, respectively. In general, larger night-time concentrations are found for the BC, OC, NO3(-)and SO4(2-), which are seasonally dependent with larger differences during late post-monsoon and winter. The high correlation (R(2)=0.74) between OC and EC along with the OC/EC of 7.09 (day time) and 4.55 (night-time), suggest significant influence of biomass-burning emissions (burning of wood and agricultural waste) as well as secondary organic aerosol formation during daytime. Concentrated weighted trajectory (CWT) analysis reveals that the potential sources for the carbonaceous aerosols and pollutants are local emissions within the urban environment and transported smoke from agricultural burning in northwest India during post-monsoon. BC radiative forcing estimates result in very high atmospheric heating rates (~1.8-2.0Kday(-1)) due to agricultural burning effects during the 2012 post-monsoon season. PMID:25864155

  6. Modeling Study of the Impact of Heterogeneous Reactions on Dust Surfaces on Aerosol Optical Depth and Direct Radiative Forcing over East Asia in Springtime

    Institute of Scientific and Technical Information of China (English)

    LI Jia-Wei; HAN Zhi-Wei

    2011-01-01

    The spatial distributions and interannual variations of aerosol concentrations, aerosol optical depth (AOD), aerosol direct radiative forcings, and their responses to heterogeneous reactions on dust surfaces over East Asia in March 2006-10 were investigated by utilizing a regional coupled climate-chemistry/aerosol model. Anthropogenic aerosol concentrations (inorganic + carbonaceous) were higher in March 2006 and 2008, whereas soil dust reached its highest levels in March 2006 and 2010, resulting in stronger aerosol radiative forcings in these periods. The domain and five-year (2006-10) monthly mean concentrations of anthropogenic and dust aerosols, AOD, and radiative forcings at the surface (SURF) and at the top of the atmosphere (TOA) in March were 2.4 μg m 3 13.1 lag m^-3, 0.18, -19.0 W m^-2, and -7.4 W m^-2, respectively. Heterogeneous reactions led to an increase of total inorganic aerosol concentration; however, the ambient inorganic aerosol concentration decreased, resulting in a smaller AOD and weaker aerosol radiative forcings. In March 2006 and 2010, the changes in ambient inorganic aerosols, AOD, and aerosol radiative forcings were more evident. In terms of the domain and five-year averages, the total inorganic aerosol concentrations increased by 13.7% (0.17 μg m^-3) due to heterogeneous reactions, but the ambient inorganic aerosol concentrations were reduced by 10.5% (0.13 lag m-3). As a result, the changes in AOD, SURF and TOA radiative forcings were estimated to be -3.9% (-0.007), -1.7% (0.34 W m^-2), and -4.3% (0.34 W m^-2), respectively, in March over East Asia.

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

    Science.gov (United States)

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

    2016-01-01

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

  8. Radiative Forcing of Climate Change

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Effects of the physical state of tropospheric ammonium-sulfate-nitrate particles on global aerosol direct radiative forcing

    Directory of Open Access Journals (Sweden)

    S. T. Martin

    2004-01-01

    Full Text Available The effect of aqueous versus crystalline sulfate-nitrate-ammonium tropospheric particles on global aerosol direct radiative forcing is assessed. A global three-dimensional chemical transport model predicts sulfate, nitrate, and ammonium aerosol mass. An aerosol thermodynamics model is called twice, once for the upper side (US and once for lower side (LS of the hysteresis loop of particle phase. On the LS, the sulfate mass budget is 40% solid ammonium sulfate, 12% letovicite, 11% ammonium bisulfate, and 37% aqueous. The LS nitrate mass budget is 26% solid ammonium nitrate, 7% aqueous, and 67% gas-phase nitric acid release due to increased volatility upon crystallization. The LS ammonium budget is 45% solid ammonium sulfate, 10% letovicite, 6% ammonium bisulfate, 4% ammonium nitrate, 7% ammonia release due to increased volatility, and 28% aqueous. LS aerosol water mass partitions as 22% effloresced to the gas-phase and 78% remaining as aerosol mass. The predicted US/LS global fields of aerosol mass are employed in a Mie scattering model to generate global US/LS aerosol optical properties, including scattering efficiency, single scattering albedo, and asymmetry parameter. Global annual average LS optical depth and mass scattering efficiency are, respectively, 0.023 and 10.7 m2 (g SO4-2-1, which compare to US values of 0.030 and 13.9 m2 (g SO4-2-1. Radiative transport is computed, first for a base case having no aerosol and then for the two global fields corresponding to the US and LS of the hysteresis loop. Regional, global, seasonal, and annual averages of top-of-the-atmosphere aerosol radiative forcing on the LS and US (FL and FU, respectively, in W m-2 are calculated. Including both anthropogenic and natural emissions, we obtain global annual averages of FL=-0.750, FU=-0.930, and DFU,L=24% for full sky calculations without clouds and FL=-0.485, FU=-0.605, and DFU,L=25% when clouds are included. Regionally, DFU,L=48% over the USA, 55% over Europe

  10. Retrieval of dust aerosols during night: improved assessment of long wave dust radiative forcing over Afro-Asian regions

    Science.gov (United States)

    Deepshikha, S.; Srinivasan, J.

    2010-08-01

    Several investigators in the past have used the radiance depression (with respect to clear-sky infrared radiance), resulting from the presence of mineral dust aerosols in the atmosphere, as an index of dust aerosol load in the atmosphere during local noon. Here, we have used a modified approach to retrieve dust index during night since assessment of diurnal average infrared dust forcing essentially requires information on dust aerosols during night. For this purpose, we used infrared radiance (10.5-12.5 μm), acquired from the METEOSAT-5 satellite (~ 5 km resolution). We found that the "dust index" algorithm, valid for daytime, will no longer hold during the night because dust is then hotter than the theoretical dust-free reference. Hence we followed a "minimum reference" approach instead of a conventional "maximum reference" approach. A detailed analysis suggests that the maximum dust load occurs during the daytime. Over the desert regions of India and Africa, maximum change in dust load is as much as a factor of four between day and night and factor of two variations are commonly observed. By realizing the consequent impact on long wave dust forcing, sensitivity studies were carried out, which indicate that utilizing day time data for estimating the diurnally averaged long-wave dust radiative forcing results in significant errors (as much as 50 to 70%). Annually and regionally averaged long wave dust radiative forcing (which account for the diurnal variation of dust) at the top of the atmosphere over Afro-Asian region is 2.6 ± 1.8 W m-2, which is 30 to 50% lower than those reported earlier. Our studies indicate that neglecting diurnal variation of dust while assessing its radiative impact leads to an overestimation of dust radiative forcing, which in turn result in underestimation of the radiative impact of anthropogenic aerosols.

  11. Retrieval of dust aerosols during night. Improved assessment of long wave dust radiative forcing over Afro-Asian regions

    Energy Technology Data Exchange (ETDEWEB)

    Deepshikha, S. [Indian Institute of Science, Bangalore (India). Centre for Atmospheric and Oceanic Sciences; Srinivasan, J. [Indian Institute of Science, Bangalore (India). Centre for Atmospheric and Oceanic Sciences; Indian Institute of Science, Bangalore (India). Divecha Centre for Climate Change

    2010-07-01

    Several investigators in the past have used the radiance depression (with respect to clear-sky infrared radiance), resulting from the presence of mineral dust aerosols in the atmosphere, as an index of dust aerosol load in the atmosphere during local noon. Here, we have used a modified approach to retrieve dust index during night since assessment of diurnal average infrared dust forcing essentially requires information on dust aerosols during night. For this purpose, we used infrared radiance (10.5-12.5 {mu}m), acquired from the METEOSAT-5 satellite ({proportional_to}5 km resolution). We found that the ''dust index'' algorithm, valid for daytime, will no longer hold during the night because dust is then hotter than the theoretical dust-free reference. Hence we followed a ''minimum reference'' approach instead of a conventional ''maximum reference'' approach. A detailed analysis suggests that the maximum dust load occurs during the daytime. Over the desert regions of India and Africa, maximum change in dust load is as much as a factor of four between day and night and factor of two variations are commonly observed. By realizing the consequent impact on long wave dust forcing, sensitivity studies were carried out, which indicate that utilizing day time data for estimating the diurnally averaged long-wave dust radiative forcing results in significant errors (as much as 50 to 70%). Annually and regionally averaged long wave dust radiative forcing (which account for the diurnal variation of dust) at the top of the atmosphere over Afro-Asian region is 2.6{+-}1.8Wm{sup +2}, which is 30 to 50% lower than those reported earlier. Our studies indicate that neglecting diurnal variation of dust while assessing its radiative impact leads to an overestimation of dust radiative forcing, which in turn result in underestimation of the radiative impact of anthropogenic aerosols. (orig.)

  12. Retrieval of dust aerosols during night: improved assessment of long wave dust radiative forcing over Afro-Asian regions

    Directory of Open Access Journals (Sweden)

    S. Deepshikha

    2010-08-01

    Full Text Available Several investigators in the past have used the radiance depression (with respect to clear-sky infrared radiance, resulting from the presence of mineral dust aerosols in the atmosphere, as an index of dust aerosol load in the atmosphere during local noon. Here, we have used a modified approach to retrieve dust index during night since assessment of diurnal average infrared dust forcing essentially requires information on dust aerosols during night. For this purpose, we used infrared radiance (10.5–12.5 μm, acquired from the METEOSAT-5 satellite (~ 5 km resolution. We found that the "dust index" algorithm, valid for daytime, will no longer hold during the night because dust is then hotter than the theoretical dust-free reference. Hence we followed a "minimum reference" approach instead of a conventional "maximum reference" approach. A detailed analysis suggests that the maximum dust load occurs during the daytime. Over the desert regions of India and Africa, maximum change in dust load is as much as a factor of four between day and night and factor of two variations are commonly observed. By realizing the consequent impact on long wave dust forcing, sensitivity studies were carried out, which indicate that utilizing day time data for estimating the diurnally averaged long-wave dust radiative forcing results in significant errors (as much as 50 to 70%. Annually and regionally averaged long wave dust radiative forcing (which account for the diurnal variation of dust at the top of the atmosphere over Afro-Asian region is 2.6 ± 1.8 W m−2, which is 30 to 50% lower than those reported earlier. Our studies indicate that neglecting diurnal variation of dust while assessing its radiative impact leads to an overestimation of dust radiative forcing, which in turn result in underestimation of the radiative impact of anthropogenic aerosols.

  13. Carbonaceous aerosols recorded in a Southeastern Tibetan glacier: variations, sources and radiative forcing

    Directory of Open Access Journals (Sweden)

    M. Wang

    2014-07-01

    Full Text Available High temporal resolution measurements of black carbon (BC and organic carbon (OC covering the time period of 1956–2006 in an ice core over the southeastern Tibetan Plateau show a distinct seasonal dependence of OC / BC ratio with higher values in the non-monsoon season than during the summer monsoon. We use a global aerosol-climate model, in which BC emitted from different source regions can be explicitly tracked, to quantify BC source-receptor relationships between four Asian source regions and the southeastern Tibetan Plateau as a receptor. The model results show that South Asia is a primary contributor during the non-monsoon season (October to May (81% and on an annual basis (74%, followed by East Asia (14% and 21%, respectively. The ice-core record also indicates stable and relatively low BC and OC deposition fluxes from late 1950s to 1980, followed by an overall increase to recent years. This trend is consistent with the BC and OC emission inventories and the fuel consumption of South Asia as the primary contributor. Moreover, the increasing trend of OC / BC ratio since the early 1990s indicates a growing contribution of coal combustion and biomass burning to the emissions. The estimated radiative forcing induced by BC and OC impurities in snow has increased since 1980, suggesting an increasing influence of carbonaceous aerosols on the Tibetan glacier melting and the availability of water resources in the surrounding regions. Our study indicates that more attention to OC is merited because of its non-negligible light absorption and the recent rapid increases evident in the ice core record.

  14. Carbonaceous aerosols recorded in a Southeastern Tibetan glacier: variations, sources and radiative forcing

    Science.gov (United States)

    Wang, M.; Xu, B.; Cao, J.; Tie, X.; Wang, H.; Zhang, R.; Qian, Y.; Rasch, P. J.; Zhao, S.; Wu, G.; Zhao, H.; Joswiak, D. R.; Li, J.; Xie, Y.

    2014-07-01

    High temporal resolution measurements of black carbon (BC) and organic carbon (OC) covering the time period of 1956-2006 in an ice core over the southeastern Tibetan Plateau show a distinct seasonal dependence of OC / BC ratio with higher values in the non-monsoon season than during the summer monsoon. We use a global aerosol-climate model, in which BC emitted from different source regions can be explicitly tracked, to quantify BC source-receptor relationships between four Asian source regions and the southeastern Tibetan Plateau as a receptor. The model results show that South Asia is a primary contributor during the non-monsoon season (October to May) (81%) and on an annual basis (74%), followed by East Asia (14% and 21%, respectively). The ice-core record also indicates stable and relatively low BC and OC deposition fluxes from late 1950s to 1980, followed by an overall increase to recent years. This trend is consistent with the BC and OC emission inventories and the fuel consumption of South Asia as the primary contributor. Moreover, the increasing trend of OC / BC ratio since the early 1990s indicates a growing contribution of coal combustion and biomass burning to the emissions. The estimated radiative forcing induced by BC and OC impurities in snow has increased since 1980, suggesting an increasing influence of carbonaceous aerosols on the Tibetan glacier melting and the availability of water resources in the surrounding regions. Our study indicates that more attention to OC is merited because of its non-negligible light absorption and the recent rapid increases evident in the ice core record.

  15. Estimate of surface direct radiative forcing of desert dust from atmospheric modulation of the aerosol optical depth

    Directory of Open Access Journals (Sweden)

    A. di Sarra

    2013-06-01

    Full Text Available Measurements carried out on the island of Lampedusa, in the central Mediterranean, on 7 September 2005, show the occurrence of a quasi-periodic oscillation of aerosol optical depth, column water vapour, and surface irradiance in different spectral bands. The oscillation has a period of about 13 min and is attributed to the propagation of a gravity wave able to modify the vertical structure of the planetary boundary layer, as also confirmed by satellite images. The wave occurred during a Saharan dust event. The oscillation amplitude is about 0.1 for the aerosol optical depth, and about 0.4 cm for the column water vapour. The modulation of the downward surface irradiances is in opposition of phase with respect to aerosol optical depth and water vapour column variations. The perturbation of the downward irradiance produced by the aerosols is determined by comparing the measured irradiances with estimated irradiances at a fixed value of the aerosol optical depth, and by correcting for the effect of the water vapour in the shortwave spectral range. The direct radiative forcing efficiency, i.e., the radiative perturbation of the net surface irradiance produced by a unit of optical depth aerosol layer, is determined at different solar zenith angles as the slope of the irradiance perturbation versus the aerosol optical depth. The estimated direct surface forcing efficiency at about 60° solar zenith angle is −(181 ± 17 W m−2 in the shortwave, and −(83 ± 7 W m−2 in the photosynthetic spectral range. The estimated daily average forcing efficiencies are of about −79 and −46 W m−2 for the shortwave and photosynthetic spectral range, respectively.

  16. Estimate of surface direct radiative forcing of desert dust from atmospheric modulation of the aerosol optical depth

    Directory of Open Access Journals (Sweden)

    A. di Sarra

    2013-01-01

    Full Text Available Measurements carried out on the island of Lampedusa, in the central Mediterranean, on 7 September 2005, show the occurrence of a quasi periodic oscillation of aerosol optical depth, column water vapour, and surface irradiance in different spectral bands. The oscillation has a period of about 13 min and is attributed to the propagation of a gravity wave able to modify the vertical structure of the planetary boundary layer. The wave occurred during an event of Saharan dust at Lampedusa. The oscillation amplitude is about 0.1 for the aerosol optical depth, and about 0.4 cm for the column water vapour. The modulation of the downward surface irradiances is in opposition of phase with respect to aerosol optical depth and water vapour column variations. The perturbation to the downward irradiance produced by the aerosols is determined by comparing the measured irradiances with estimated irradiances at a fixed value of the aerosol optical depth, and by correcting for the effect of the water vapour in the shortwave spectral range. The direct radiative forcing efficiency, i.e. the radiative perturbation to the net surface irradiance produced by a unit optical depth aerosol layer, is determined at different solar zenith angles as the slope of the irradiance perturbation versus the aerosol optical depth. The estimated direct surface forcing efficiency at 60° solar zenith angle is −(181 ± 17 W m−2 in the shortwave, and −(83 ± 7 W m−2 in the photosynthetic spectral range. The estimated daily average forcing efficiencies are of about −79 and −46 W m−2 for the shortwave and photosynthetic spectral range, respectively.

  17. Radiative forcing by aerosols as derived from the AeroCom present-day and pre-industrial simulations

    Directory of Open Access Journals (Sweden)

    M. Schulz

    2006-01-01

    Full Text Available Nine different global models with detailed aerosol modules have independently produced instantaneous direct radiative forcing due to anthropogenic aerosols. The anthropogenic impact is derived from the difference of two model simulations with prescribed aerosol emissions, one for present-day and one for pre-industrial conditions. The difference in the solar energy budget at the top of the atmosphere (ToA yields a new harmonized estimate for the aerosol direct radiative forcing (RF under all-sky conditions. On a global annual basis RF is −0.22 Wm−2, ranging from +0.04 to −0.41 Wm−2, with a standard deviation of ±0.16 Wm−2. Anthropogenic nitrate and dust are not included in this estimate. No model shows a significant positive all-sky RF. The corresponding clear-sky RF is −0.68 Wm−2. The cloud-sky RF was derived based on all-sky and clear-sky RF and modelled cloud cover. It was significantly different from zero and ranged between −0.16 and +0.34 Wm−2. A sensitivity analysis shows that the total aerosol RF is influenced by considerable diversity in simulated residence times, mass extinction coefficients and most importantly forcing efficiencies (forcing per unit optical depth. The clear-sky forcing efficiency (forcing per unit optical depth has diversity comparable to that for the all-sky/ clear-sky forcing ratio. While the diversity in clear-sky forcing efficiency is impacted by factors such as aerosol absorption, size, and surface albedo, we can show that the all-sky/clear-sky forcing ratio is important because all-sky forcing estimates require proper representation of cloud fields and the correct relative altitude placement between absorbing aerosol and clouds. The analysis of the sulphate RF shows that long sulphate residence times are compensated by low mass extinction coefficients and vice versa. This is explained by more sulphate particle humidity growth and thus higher extinction in those models where short-lived sulphate

  18. Effects of sea surface winds on marine aerosols characteristics and impacts on longwave radiative forcing over the Arabian Sea

    Directory of Open Access Journals (Sweden)

    Vijayakumar S. Nair

    2008-08-01

    Full Text Available Collocated measurements of spectral aerosol optical depths (AODs, total and BC mass concentrations, and number size distributions of near surface aerosols, along with sea surface winds, made onboard a scientific cruise over southeastern Arabian Sea, are used to delineate the effects of changes in the wind speed on aerosol properties and its implication on the shortwave and longwave radiative forcing. The results indicated that an increase in the sea-surface wind speed from calm to moderate (<1 to 8 m s−1 values results in a selective increase of the particle concentrations in the size range 0.5 to 5 μm, leading to significant changes in the size distribution, increase in the mass concentration, decrease in the BC mass fraction, a remarkable increase in AODs in the near infrared and a flattening of the AOD spectrum. The consequent increase in the longwave direct radiative forcing almost entirely offsets the corresponding increase in the short wave direct radiative forcing (or even overcompensates at the top of the atmosphere; while the surface forcing is offset by about 50%.

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

    Science.gov (United States)

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

    2016-08-01

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

  20. Aerosol nucleation and its role for clouds and Earth's radiative forcing in the aerosol-climate model ECHAM5-HAM

    Directory of Open Access Journals (Sweden)

    J. Kazil

    2010-05-01

    Full Text Available Nucleation from the gas phase is an important source of aerosol particles in the Earth's atmosphere, contributing to the number of cloud condensation nuclei, which form cloud droplets. We have implemented in the aerosol-climate model ECHAM5-HAM a new scheme for neutral and charged nucleation of sulfuric acid and water based on laboratory data, and nucleation of an organic compound and sulfuric acid using a parametrization of cluster activation based on field measurements. We give details of the implementation, compare results with observations, and investigate the role of the individual aerosol nucleation mechanisms for clouds and the Earth's radiative budget. The results of our simulations are most consistent with observations when neutral and charged nucleation of sulfuric acid proceed throughout the troposphere and nucleation due to cluster activation is limited to the forested boundary layer. The globally averaged annual mean contributions of the individual nucleation processes to total absorbed solar short-wave radiation via the direct, semi-direct, indirect cloud-albedo and cloud-lifetime effects in our simulations are −1.15 W/m2 for charged H2SO4/H2O nucleation, −0.235 W/m2 for cluster activation, and −0.05 W/m2 for neutral H2SO4/H2O nucleation. The overall effect of nucleation is −2.55 W/m2, which exceeds the sum of the individual terms due to feedbacks and interactions in the model. Aerosol nucleation contributes over the oceans with −2.18 W/m2 to total absorbed solar short-wave radiation, compared to −0.37 W/m2 over land. We explain the higher effect of aerosol nucleation on Earth's radiative budget over the oceans with the larger area covered by ocean clouds, due to the larger contrast in albedo between clouds and the ocean surface compared to continents, and the larger susceptibility of

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

    Science.gov (United States)

    Artaxo, Paulo

    2016-07-01

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

  2. Dust emission size distribution impact on aerosol budget and radiative forcing over the Mediterranean region: a regional climate model approach

    Directory of Open Access Journals (Sweden)

    P. Nabat

    2012-07-01

    Full Text Available The present study investigates the dust emission and load over the Mediterranean basin using the coupled-chemistry-aerosol regional climate model RegCM-4. The first step of this work focuses on dust particle emission size distribution modeling. We compare a parameterization in which the emission is based on the individual kinetic energy of the aggregates striking the surface to a recent parameterization based on an analogy with the fragmentation of brittle materials. The main difference between the two dust schemes concerns the mass proportion of fine aerosol which is reduced in the case of the new dust parameterization, with consequences for optical properties. At the episodic scale, comparisons between RegCM-4 simulations, satellite and ground-based data show a clear improvement using the new dust distribution in terms of Aerosol Optical Depth (AOD values and geographic gradients. These results are confirmed at the seasonal scale for the investigated year 2008. A multi-annual simulation is finally carried out using the new dust distribution over the period 2000–2009. This change of dust distribution has sensitive impacts on the simulated regional dust budget, notably dry dust deposition and the regional direct aerosol radiative forcing over the Mediterranean basin. This could clearly modify the possible effects of dust aerosols on the biogeochemical activity and climate of the Mediterranean basin. In particular, we find that the new size distribution produces a higher dust deposition flux, and smaller top of atmosphere (TOA dust radiative cooling.

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

    Science.gov (United States)

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

    2012-12-01

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

  4. Aerosol chemistry and the effect of aerosol water content on visibility impairment and radiative forcing in Guangzhou during the 2006 Pearl River Delta campaign.

    Science.gov (United States)

    Jung, Jinsang; Lee, Hanlim; Kim, Young J; Liu, Xingang; Zhang, Yuanhang; Gu, Jianwei; Fan, Shaojia

    2009-08-01

    Optical and chemical aerosol measurements were obtained from 2 to 31 July 2006 at an urban site in the metropolitan area of Guangzhou (China) as part of the Program of Regional Integrated Experiment of Air Quality over Pearl River Delta (PRIDE-PRD2006) to investigate aerosol chemistry and the effect of aerosol water content on visibility impairment and radiative forcing. During the PRIDE-PRD2006 campaign, the average contributions of ammonium sulfate, organic mass by carbon (OMC), elemental carbon (EC), and sea salt (SS) to total PM(2.5) mass were measured to be 36.5%, 5.7%, 27.1%, 7.8%, and 3.7%, respectively. Compared with the clean marine period, (NH(4))(2)SO(4), NH(4)NO(3), and OMC were all greatly enhanced (by up to 430%) during local haze periods via the accumulation of a secondary aerosol component. The OMC dominance increased when high levels of biomass burning influenced the measurement site while (NH(4))(2)SO(4) and OMC did when both biomass burning and industrial emissions influenced it. The effect of aerosol water content on the total light-extinction coefficient was estimated to be 34.2%, of which 25.8% was due to aerosol water in (NH(4))(2)SO(4), 5.1% that in NH(4)NO(3), and 3.3% that in SS. The average mass-scattering efficiency (MSE) of PM(10) particles was determined to be 2.2+/-0.6 and 4.6+/-1.7m(2)g(-1) under dry (RHalbedo (SSA) was 0.80+/-0.08 and 0.90+/-0.04 under dry and ambient conditions, respectively. Not only are the extinction and scattering coefficients greatly enhanced by aerosol water content, but MSE and SSA are also highly sensitive. It can be concluded that sulfate and carbonaceous aerosol, as well as aerosol water content, play important roles in the processes that determine visibility impairment and radiative forcing in the ambient atmosphere of the Guangzhou urban area. PMID:19523748

  5. Impacts of Global Wildfire Aerosols on Direct Radiative, Cloud and Surface-Albedo Forcings Simulated with CAM5

    OpenAIRE

    Jiang, Yiquan; Lu, Zheng; Liu, Xiaohong; Qian, Yun; Zhang, Kai; Wang, Yuhang; Yang, Xiu-Qun

    2016-01-01

    Aerosols from wild-land fires could significantly perturb the global radiation balance and induce the climate change. In this study, the Community Atmospheric Model version 5 (CAM5) with prescribed daily fire aerosol emissions is used to investigate the spatial and seasonal characteristics of radiative effects (REs) of wildfire aerosols including black carbon (BC) and particulate organic matter (POM). The global annual mean direct radiative effect (DRE) of all fire aerosols is 0.155 ± 0.01 W ...

  6. Direct radiative forcing due to aerosols in East Asia during a Hwangsa (Asian dust) event observed on 19-23 March 2002 in Korea

    Energy Technology Data Exchange (ETDEWEB)

    Soonung Park; Limseok Chang; Eunhee Lee [Seoul National Univ., School of Earth and Environmental Sciences, Seoul (Korea)

    2005-05-01

    The Asian dust aerosol model (ADAM) and the aerosol dynamic model with the output of the fifth generation of mesoscale model (MM5) in a grid of 30 x 30 km{sup 2} have been employed to simulate the temporal and spatial distribution of the Asian dust aerosol and the anthropogenic aerosol concentrations in East Asia for the period of 19-23 March 2002 when a severe Asian dust (Hwangsa) event was observed in Korea. The simulated aerosols are implemented to estimate radiative forcing at the surface and the top of atmosphere (TOA) with the use of the National Center for Atmospheric Research (NCAR) column radiation model (CRM) of community climate model 3 (CCM3). The results indicate that the ADAM model simulates quite well the spectral-mass concentration distribution with the R{sup 2} value of 0.7 whereas the aerosol dynamic model underestimates the observed anthropogenic aerosol by a factor of 4 over Korea. The estimated mean total aerosol mass in the analysis domain for the period of 19-20 March 2002 is found to be about 880 mg m{sup -2}, of which 98% and 2% are, respectively contributed by the Asian dust aerosol and the anthropogenic aerosol. However, the direct radiative forcing contributed by the anthropogenic aerosol are about 40% of the mean radiative forcing at the surface (-11 W m{sup -2}) and 45% of the mean radiative forcing at TOA (-6 W m{sup -2}), implying the importance of the anthropogenic aerosol on the direct radiative forcings at both the surface and TOA. The difference between the radiative forcing at TOA and the surface that indicates the atmospheric absorption is found to be 5 W m{sup -2}, of which 3 and 2 W m{sup -2} are, respectively contributed by the Asian dust aerosol and the anthropogenic aerosol, suggesting the importance of the Asian dust aerosol on the regional radiative energy balance especially in the high occurrence frequency season of spring. (Author)

  7. Reevaluation of Mineral aerosol radiative forcings suggests a better agreement with satellite and AERONET data

    Directory of Open Access Journals (Sweden)

    Y. Balkanski

    2007-01-01

    Full Text Available Modelling studies and satellite retrievals do not agree on the amplitude and/or sign of the direct radiative perturbation from dust. Modelling studies have systematically overpredicted mineral dust absorption compared to estimates based upon satellite retrievals. In this paper we first point out the source of this discrepancy, which originates from the shortwave refractive index of dust used in models. The imaginary part of the refractive index retrieved from AERONET over the range 300 to 700 nm is 3 to 6 times smaller than that used previously to model dust. We attempt to constrain these refractive indices using a mineralogical database and varying the abundances of iron oxides (the main absorber in the visible. We first consider the optically active mineral constituents of dust and compute the refractive indices from internal and external mixtures of minerals with relative amounts encountered in parent soils. We then compute the radiative perturbation due to mineral aerosols for internally and externally mixed minerals for 3 different hematite contents, 0.9%, 1.5% and 2.7% by volume. These constant amounts of hematite allow bracketing the influence of dust aerosol when it is respectively an inefficient, standard and a very efficient absorber. These values represent low, central and high content of iron oxides in dust determined from the mineralogical database. Linke et al. (2006 determined independently that iron-oxides represent 1.0 to 2.5% by volume using x-Ray fluorescence on 4 different samples collected over Morocco and Egypt. Based upon values of the refractive index retrieved from AERONET, we show that the best agreement between 440 and 1020 nm occurs for mineral dust internally mixed with 1.5% volume weighted hematite. This representation of mineral dust allows us to compute, using a general circulation model, a new global estimate of mineral dust perturbation between –0.47 and –0.24 Wm−2 at the top of the atmosphere, and between

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

    Science.gov (United States)

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

    2016-01-01

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

  9. Impact of Direct Radiative Forcing of Anthropogenic Aerosols on Diurnal Temperature Range in January in Eastern China

    Institute of Scientific and Technical Information of China (English)

    CHANG Wen-Yuan; LIAO Hong

    2011-01-01

    This study investigates the changes in January diurnal temperature range (DTR) in China during 1961- 2000. The observed DTR changes during 1981-2000 relative to 1961-80 are first analyzed based on the daily temperature data at 546 weather stations. These observed DTR changes are classified into six cases depending on the changes in daily maximum and minimum temperatures, and then the occurrence frequency and magnitude of DTR change in each case are presented. Three transient simulations are then performed to understand the impact of greenhouse gases (GHGs) and aerosol direct forcing on DTR change: one without anthropogenic radiative forcing, one with anthropogenic GHGs, and another one with the combined forcing of GHGs and five species of anthropogenic aerosols. The predicted daily DTR changes during the years 1981-2000 are also classified into six cases and are compared with the observations. Results show that the previously proposed reason for DTR reduction, a stronger nocturnal warming than a daytime warming, explains only 19.8% of the observed DTR reduction days. DTR reduc- tions are found to generally occur in northeastern China, coinciding with significant regional warming. The simu- lation with GHG forcing alone reproduces this type of DTR reduction with an occurrence frequency of 32.9%, which is larger than the observed value. Aerosol direct forcing reduces DTR mainly by daytime cooling. Consideration of aerosol cooling improves the simulation of occurrence frequencies of different types of DTR changes as compared to the simulation with GHGs alone, but it cannot improve the prediction of the magnitude of DTR changes.

  10. Aerosol direct radiative forcing during Sahara dust intrusions in the central Mediterranean

    Directory of Open Access Journals (Sweden)

    M. R. Perrone

    2009-10-01

    Full Text Available The clear-sky, instantaneous Direct Radiative Effect (DRE by all and anthropogenic particles is calculated during Sahara dust intrusions in the Mediterranean basin, to evaluate the role of anthropogenic particle's radiative effects and to get a better estimate of the DRE by desert dust. The clear-sky aerosol DRE is calculated by a two stream radiative transfer model in the solar (0.3–4 μm and infrared (4–200 μm spectral range, at the top of the atmosphere (ToA and at the Earth's surface (sfc. Aerosol optical properties by AERONET sun-sky photometer measurements and aerosol vertical profiles by EARLINET lidar measurements, both performed at Lecce (40.33° N, 18.10° E during Sahara dust intrusions occurred from 2003 to 2006 year, are used to initialize radiative transfer simulations. Instantaneous values at 0.44 μm of the real (n and imaginary (k refractive index and of the of aerosol optical depth (AOD vary within the 1.33–1.55, 0.0037–0.014, and 0.2–0.7 range, respectively during the analyzed dust outbreaks. Fine mode particles contribute from 34% to 85% to the AOD by all particles. The complex atmospheric chemistry of the Mediterranean basin that is also influenced by regional and long-range transported emissions from continental Europe and the dependence of dust optical properties on soil properties of source regions and transport pathways are responsible for the high variability of n, k, and AOD values and of the fine mode particle contribution. Instantaneous net (solar+infrared DREs that are negative as a consequence of the cooling effect by aerosol particles, span the – (32–10 W m−2 and the – (44–20 W m−2 range at the ToA and surface, respectively. The instantaneous net DRE by anthropogenic particles that is negative, varies within −(13–8 W m−2 and −(17–11 W m−2 at the ToA and surface, respectively. It represents from 41 up to 89

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

    Science.gov (United States)

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

    2010-05-01

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

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

    Directory of Open Access Journals (Sweden)

    D. A. Hauglustaine

    2014-03-01

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

  13. Airborne lidar study of the vertical distribution of aerosols over Hyderabad, an urban site in central India, and its implication for radiative forcing calculations

    Directory of Open Access Journals (Sweden)

    H. Gadhavi

    2006-10-01

    Full Text Available Use of a compact, low power commercial lidar onboard a small aircraft for aerosol studies is demonstrated. A Micro Pulse Lidar fitted upside down in a Beech Superking aircraft is used to measure the vertical distribution of aerosols in and around Hyderabad, an urban location in the central India. Two sorties were made, one on 17 February 2004 evening hours and the other on 18 February 2004 morning hours for a total flight duration of four hours. Three different algorithms, proposed by Klett (1985, Stephens et al. (2001 and Palm et al. (2002 for deriving the aerosol extinction coefficient profile from lidar data are studied and is shown that the results obtained from the three methods compare within 2%. The result obtained from the airborne lidar is shown more useful to study the aerosol distribution in the free troposphere than that obtained by using the same lidar from ground. Using standard radiative transfer model the aerosol radiative forcing is calculated and is shown that knowledge on the vertical distribution of aerosols is very important to get more realistic values than using model vertical profiles of aerosols. We show that for the same aerosol optical depth, single scattering albedo and asymmetry parameter but for different vertical profiles of aerosol extinction the computed forcing values differ with increasing altitude and improper selection of the vertical profile can even flip the sign of the forcing at tropopause level.

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Science.gov (United States)

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

    2015-08-01

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

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

    Science.gov (United States)

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

    2016-03-01

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

  17. Aerosol Characteristics at a High Altitude Location in Central Himalayas: Optical Properties and Radiative Forcing

    OpenAIRE

    Pant, P.; Hegde, P; Dumka, U. C.; Sagar, Ram; S. K. Satheesh; Moorthy, K. Krishna

    2006-01-01

    Collocated measurements of the mass concentrations of aerosol black carbon (BC) and composite aerosols near the surface were carried out along with spectral aerosol optical depths (AODs) from a high altitude station, Manora Peak in Central Himalayas, during a comprehensive aerosol field campaign in December 2004. Despite being a pristine location in the Shivalik Ranges of Central Himalayas, and having a monthly mean AOD (at 500 nm) of 0.059 $\\pm$ 0.033 (typical to this site), total suspended ...

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Directory of Open Access Journals (Sweden)

    M. Mallet

    2015-07-01

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

  20. Aerosols optical and physical characteristics and direct radiative forcing during a "Shamal" dust storm, a case study

    Directory of Open Access Journals (Sweden)

    T. M. Saeed

    2013-09-01

    Full Text Available Dust aerosols are analyzed for their optical and physical properties during an episode of dust storm that hit Kuwait on 26 March 2003 when "Iraqi Freedom" military operation was in full swing. The intensity of the dust storm was such that it left a thick suspension of dust throughout the following day, 27 March, resulting in a considerable cooling effect at the surface on both days. Ground-based measurements of aerosol optical thickness reached 3.617 and 4.17 on 26–27 March respectively while Ångstrom coefficient, α870/440, dropped to −0.0234 and −0.0318. Particulate matter concentration of diameter 10 μm or less, PM10, peaked at 4800 μg m−3 during dust storm hours of 26 March. Moderate resolution imaging spectrometer (MODIS retrieved optical and physical characteristics that exhibited extreme values as well. The synoptic of the dust storm is presented and source regions are identified using total ozone mapping spectrometer (TOMS aerosol index retrieved images. The vertical profile of the dust layer was simulated using SKIRON atmospheric model. Instantaneous net direct radiative forcing is calculated at top of atmosphere (TOA and surface level. The thick dust layer of 26 March resulted in cooling the TOA by −60 Wm−2 and surface level by −175 Wm−2 for a surface albedo of 0.35. Slightly higher values were obtained for 27 March due to the increase in aerosol optical thickness. The large reduction in the radiative flux at the surface level had caused a drop in surface temperature by approximately 6 °C below its average value. Radiative heating/cooling rates in the shortwave and longwave bands were also examined. Shortwave heating rate reached a maximum value of 2 °K day−1 between 3 and 5 km, dropped to 1.5 °K day−1 at 6 km and diminished at 8 km. Longwave radiation initially heated the lower atmosphere by a maximum value of 0.2 °K day−1 at surface level, declined sharply at increasing altitude and diminished at 4 km

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

    Energy Technology Data Exchange (ETDEWEB)

    John H. Seinfeld

    2011-12-08

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

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

    Science.gov (United States)

    Mishra, Manoj Kumar; Rajeev, K.

    2016-08-01

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

  3. Influence of aerosol-radiative forcings on the diurnal and seasonal cycles of rainfall over West Africa and Eastern Atlantic Ocean using GCM simulations

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kyu-Myong [University of Maryland Baltimore County, Baltimore, MD (United States); Lau, William K.M.; Sud, Yogesh C. [Laboratory for Atmospheres, NASA/GSFC, Greenbelt, MD (United States); Walker, Gregory K. [SAIC/General Sciences Operation, Beltsville, MD (United States)

    2010-07-15

    Effects of aerosol radiative forcing on the diurnal and seasonal cycles of precipitation over West Africa and eastern Atlantic Ocean are investigated for the boreal summer season: June-July-August. An eight year (2000-2007) average of GCM simulated rainfall data is compared with the corresponding TRMM rainfall data. The comparison shows that the amplitude of the diurnal cycles of rainfall over land and ocean are reasonably well simulated. Over land, the phase of the simulated diurnal cycle of precipitation peaks several hours earlier than that of the TRMM data. Corresponding differences over the ocean(s) are relatively smaller. Some of the key features of the aerosol induced model simulated field anomalies are: (a) aerosol direct radiative forcing which increases the atmospheric stability and reduces the daytime moist convection and convective precipitation; (b) the aerosol induced changes in the diurnal cycle of precipitation are out of phase with those of the TRMM data over land, but are in-phase over the ocean; (c) aerosols reduce the amplitude of the diurnal cycle of precipitation over land and enhance it over ocean. However, the phase of the diurnal cycle is not affected much by the aerosol radiative forcing both over land and ocean. During the boreal summer, aerosol radiative forcing and induced circulation and precipitation cool the Sahel and the southern part of Sahara desert more than the adjacent areas to the north and south, thereby shifting the peak meridional temperature gradient northward. Consequently, an anomalous easterly jet is found north of its climatological location. This anomalous jet is associated with increased cyclonic circulation to the south of its axis, resulting in an anomalous monsoon rain belt in the Sahel. (orig.)

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

    OpenAIRE

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

    2015-01-01

    It is widely expected that global emissions of atmospheric aerosols and their precursors will decrease strongly throughout the remainder of the 21st century, due to emission reduction policies enacted to protect human health. For instance, global emissions of aerosols and their precursors are projected to decrease by as much as 80% by the year 2100, according to the four Representative Concentration Pathway (RCP) sce...

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

    OpenAIRE

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

    2011-01-01

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

  6. Aerosol Characteristics at a High Altitude Location in Central Himalayas: Optical Properties and Radiative Forcing

    CERN Document Server

    Pant, P; Dumka, U C; Sagar, R; Satheesh, S K; Moorthy, K K; Sagar, Ram

    2006-01-01

    Collocated measurements of the mass concentrations of aerosol black carbon (BC) and composite aerosols near the surface were carried out along with spectral aerosol optical depths (AODs) from a high altitude station, Manora Peak in Central Himalayas, during a comprehensive aerosol field campaign in December 2004. Despite being a pristine location in the Shivalik Ranges of Central Himalayas, and having a monthly mean AOD (at 500 nm) of 0.059 $\\pm$ 0.033 (typical to this site), total suspended particulate (TSP) concentration was in the range 15 - 40 micro g m^(-3) (mean value 27.1 $\\pm$ 8.3 micro g m^(-3)). Interestingly, aerosol BC had a mean concentration of 1.36 $\\pm$ 0.99 micro g m^(-3), contributed to ~5.0 $\\pm$ 1.3 % to the composite aerosol mass. This large abundance of BC is found to have linkages to the human activities in the adjoining valley and to the boundary layer dynamics. Consequently, the inferred single scattering albedo lies in the range of 0.87 to 0.94 (mean value 0.90 $\\pm$ 0.03), indicatin...

  7. Radiative forcing by contrails

    Directory of Open Access Journals (Sweden)

    R. Meerkötter

    Full Text Available 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 atmosphere. 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 Wm-2 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.

    Key words. Atmospheric composition and structure (aerosols and particles · Meteorology and atmospheric dynamics (climatology · radiative processes

  8. Temporal variation of aerosol optical depth and associated shortwave radiative forcing over a coastal site along the west coast of India

    Energy Technology Data Exchange (ETDEWEB)

    Menon, Harilal B., E-mail: harilalm@gmail.com [Department of Marine Sciences, Goa University, Taleigao Plateau, Panjim, Goa 403602 (India); Shirodkar, Shilpa [Department of Marine Sciences, Goa University, Taleigao Plateau, Panjim, Goa 403602 (India); Kedia, Sumita; Ramachandran, S. [Physical Research Laboratory, Navarangpura, Ahmedabad, Gujarat State 380009 (India); Babu, Suresh; Moorthy, K. Krishna [Space Physics Laboratory, Vikram Sarabhai Space Center, Thiruvananthapuram, Kerala (India)

    2014-01-01

    Optical characterization of aerosol was performed by assessing the columnar aerosol optical depth (AOD) and angstrom wavelength exponent (α) using data from the Microtops II Sunphotometer. The data were collected on cloud free days over Goa, a coastal site along the west coast of India, from January to December 2008. Along with the composite aerosol, the black carbon (BC) mass concentration from the Aethalometer was also analyzed. The AOD{sub 0}.{sub 500} {sub μm} and angstrom wavelength exponent (α) were in the range of 0.26 to 0.7 and 0.52 to 1.33, respectively, indicative of a significant seasonal shift in aerosol characteristics during the study period. The monthly mean AOD{sub 0.500} {sub μm} exhibited a bi-modal distribution, with a primary peak in April (0.7) and a secondary peak in October (0.54), whereas the minimum of 0.26 was observed in May. The monthly mean BC mass concentration varied between 0.31 μg/m{sup 3} and 4.5 μg/m{sup 3}, and the single scattering albedo (SSA), estimated using the OPAC model, ranged from 0.87 to 0.97. Modeled aerosol optical properties were used to estimate the direct aerosol shortwave radiative forcing (DASRF) in the wavelength range 0.25 μm4.0 μm. The monthly mean forcing at the surface, at the top of the atmosphere (TOA) and in the atmosphere varied between − 14.1 W m{sup −2} and − 35.6 W m{sup −2}, − 6.7 W m{sup −2} and − 13.4 W m{sup −2} and 5.5 W m{sup −2} to 22.5 W m{sup −2}, respectively. These results indicate that the annual SSA cycle in the atmosphere is regulated by BC (absorbing aerosol), resulting in a positive forcing; however, the surface forcing was governed by the natural aerosol scattering, which yielded a negative forcing. These two conditions neutralized, resulting in a negative forcing at the TOA that remains nearly constant throughout the year. - Highlights: • Temporal variation of AOD during the year 2008 exhibits a bimodal distribution. • SSA in the atmosphere is

  9. Temporal variation of aerosol optical depth and associated shortwave radiative forcing over a coastal site along the west coast of India

    International Nuclear Information System (INIS)

    Optical characterization of aerosol was performed by assessing the columnar aerosol optical depth (AOD) and angstrom wavelength exponent (α) using data from the Microtops II Sunphotometer. The data were collected on cloud free days over Goa, a coastal site along the west coast of India, from January to December 2008. Along with the composite aerosol, the black carbon (BC) mass concentration from the Aethalometer was also analyzed. The AOD0.500μm and angstrom wavelength exponent (α) were in the range of 0.26 to 0.7 and 0.52 to 1.33, respectively, indicative of a significant seasonal shift in aerosol characteristics during the study period. The monthly mean AOD0.500μm exhibited a bi-modal distribution, with a primary peak in April (0.7) and a secondary peak in October (0.54), whereas the minimum of 0.26 was observed in May. The monthly mean BC mass concentration varied between 0.31 μg/m3 and 4.5 μg/m3, and the single scattering albedo (SSA), estimated using the OPAC model, ranged from 0.87 to 0.97. Modeled aerosol optical properties were used to estimate the direct aerosol shortwave radiative forcing (DASRF) in the wavelength range 0.25 μm4.0 μm. The monthly mean forcing at the surface, at the top of the atmosphere (TOA) and in the atmosphere varied between − 14.1 W m−2 and − 35.6 W m−2, − 6.7 W m−2 and − 13.4 W m−2 and 5.5 W m−2 to 22.5 W m−2, respectively. These results indicate that the annual SSA cycle in the atmosphere is regulated by BC (absorbing aerosol), resulting in a positive forcing; however, the surface forcing was governed by the natural aerosol scattering, which yielded a negative forcing. These two conditions neutralized, resulting in a negative forcing at the TOA that remains nearly constant throughout the year. - Highlights: • Temporal variation of AOD during the year 2008 exhibits a bimodal distribution. • SSA in the atmosphere is regulated by BC, which results in a positive forcing. • The surface forcing is

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

    Directory of Open Access Journals (Sweden)

    Hongru Yan

    2014-02-01

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

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

    Directory of Open Access Journals (Sweden)

    A. Chrastansky

    2012-12-01

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

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

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

  12. Experimental synergy combining lidar measurements so as to optically characterize aerosols: applications to air quality and radiative forcing

    International Nuclear Information System (INIS)

    The work carried out in this study is devoted to a better understanding of the evolution of aerosol physical, chemical and optical properties for urban pollution aerosols, dust and biomass burning particles. It mainly concerns the complex refractive index and the single-scattering albedo. Such a characterisation is indeed necessary so as to fulfil the requirements of scientific and societal air quality and global climate evolution questions. Our study is based on a synergy between different measurements platforms: ground-based or airborne measurements, together with active and passive remote sensing observations. Lidar in particular turns out to be an essential tool in order to assess horizontal and vertical variability of aerosol micro-physical and optical properties in the atmospheric boundary layer, but also in the residual layer, as well as in layers transported from the boundary layer to the free troposphere. The original methodology we developed highlights the importance of the geographical origin, the impact of aging and dynamical processes in the evolution of structural, optical and hygroscopic aerosol features. The related accurate determination of the properties in each aerosol layer is required for radiative fluxes and heating rates calculations in the atmospheric column. The radiative impact of both dust particles and biomass burning aerosols observed over the region of Niamey (Niger) was thus assessed during the dry season. These results reveal the need of a better characterisation of those significant aerosol properties for each layer in models. (author)

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

    Science.gov (United States)

    Wang, M.; Xu, B.; Cao, J.; Tie, X.; Wang, H.; Zhang, R.; Qian, Y.; Rasch, P. J.; Zhao, S.; Wu, G.; Zhao, H.; Joswiak, D. R.; Li, J.; Xie, Y.

    2015-02-01

    High temporal resolution measurements of black carbon (BC) and organic carbon (OC) covering the time period of 1956-2006 in an ice core over the southeastern Tibetan Plateau show a distinct seasonal dependence of BC and OC with higher respective concentrations but a lower OC / BC ratio in the non-monsoon season than during the summer monsoon. We use a global aerosol-climate model, in which BC emitted from different source regions can be explicitly tracked, to quantify BC source-receptor relationships between four Asian source regions and the southeastern Tibetan Plateau as a receptor. The model results show that South Asia has the largest contribution to the present-day (1996-2005) mean BC deposition at the ice-core drilling site during the non-monsoon season (October to May) (81%) and all year round (74%), followed by East Asia (14% to the non-monsoon mean and 21% to the annual mean). The ice-core record also indicates stable and relatively low BC and OC deposition fluxes from the late 1950s to 1980, followed by an overall increase to recent years. This trend is consistent with the BC and OC emission inventories and the fuel consumption of South Asia (as the primary contributor to annual mean BC deposition). Moreover, the increasing trend of the OC / BC ratio since the early 1990s indicates a growing contribution of coal combustion and/or biomass burning to the emissions. The estimated radiative forcing induced by BC and OC impurities in snow has increased since 1980, suggesting an increasing potential influence of carbonaceous aerosols on the Tibetan glacier melting and the availability of water resources in the surrounding regions. Our study indicates that more attention to OC is merited because of its non-negligible light absorption and the recent rapid increases evident in the ice-core record.

  14. Why Is the Climate Forcing of Sulfate Aerosols So Uncertain?

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Sulfate aerosol particles have strong scattering effect on the solar radiation transfer which results in increasing the planet albedo and, hence, tend to cool the earth-atmosphere system. Also, aerosols can act as the cloud condensation nuclei (CCN) which tend to increase the albedo of clouds and cool the global warming. The ARPEGE-Climat version 3 AGCM with FMR radiation scheme is used to estimate the direct and indirect radiative forcing of sulfate aerosols. For minimizing the uncertainties in assessing this kind of cooling effect, all kinds of factors are analyzed which have been mixed in the assessment process and may lead to the different results of the radiative forcing of aerosols. It is noticed that one of the uncertainties to assess the climate forcing of aerosols by GCM results from the different definition of radiative forcing that was used. In order to clarify this vague idea, the off-line case for considering no feedbacks and on-line case for including all the feedbacks have been used for assessment. The direct forcing of sulfate aerosols in off-line case is -0.57 W/m2 and -0.38 W/m2 for the clear sky and all sky respectively. The value of on-line case appears to be a little larger than that in off-line case chiefly due to the feedback of clouds. The indirect forcing of sulfate aerosols in off-line case is -1.4 W / m2 and -1.0 W / m2 in on-line case. The radiative forcing of sulfate aerosols has obvious regional characteristics. There is a larger negative radiative forcing over North America, Europe and East Asia. If the direct and indirect forcing are added together, it is enough to offset the positive radiative forcing induced by the greenhouse gases in these regions.

  15. Estimation of aerosol radiative forcing over an aged-background aerosol feature during advection and non-advection events using a ground-based data obtained from a Prede Skyradiometer observation

    Science.gov (United States)

    Ningombam, Shantikumar S.; Bagare, S. P.; Khatri, P.; Sohn, B. J.; Song, H.-J.

    2015-10-01

    Estimation of aerosol radiative forcing (ARF) was performed using a radiative transfer model (Rstar6b) along with physical and optical parameters of aerosols obtained from sky radiometer observation over Indian Astronomical Observatory (IAO), Hanle, Ladakh, during 2008-2010 from dust, anthropogenic, and aged background observing conditions. ARF was estimated at the top of the atmosphere (TOA), in the atmosphere, and at the surface during the three observing conditions. During dust and anthropogenic events, average aerosol optical depth (AOD at 500 nm) went up to 0.24 from the aged background observing condition 0.04. Such enhancement of AOD is associated by the combination of desert-dust and anthropogenic aerosols transported from distant sources as noticed from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Such three types of aerosols are also identified from the observed properties of single scattering albedo (SSA), aerosol asymmetry (AS) parameter, and aerosol size distribution. The estimated ARFs at TOA, at the surface, and in atmosphere are - 3.73, - 6.82, and 3.40 Wm- 2, respectively during the dust advection period. On the contrary, the respective ARFs during the aged background observing condition are - 1.50, - 2.22, and 0.70 Wm- 2, respectively. A significant difference of spectral AOD is observed during dust, anthropogenic, and aged background observing conditions. Ångström exponent (AE) decreases from 1.05 in the aged background observing condition to 0.40 in the dust event. A significant difference of coarse-fine mode volume distribution is also observed between the dust and the anthropogenic cases. Further, the study reveals high aerosols induced during the dust and the anthropogenic episodes caused warming at atmosphere and cooling at surface which collectively may affect the local atmospheric circulation.

  16. A study of uncertainties in the sulfate distribution and its radiative forcing associated with sulfur chemistry in a global aerosol model

    Directory of Open Access Journals (Sweden)

    D. Goto

    2011-11-01

    Full Text Available The direct radiative forcing by sulfate aerosols is still uncertain, mainly because the uncertainties are largely derived from differences in sulfate column burdens and its vertical distributions among global aerosol models. One possible reason for the large difference in the computed values is that the radiative forcing delicately depends on various simplifications of the sulfur processes made in the models. In this study, therefore, we investigated impacts of different parts of the sulfur chemistry module in a global aerosol model, SPRINTARS, on the sulfate distribution and its radiative forcing. Important studies were effects of simplified and more physical-based sulfur processes in terms of treatment of sulfur chemistry, oxidant chemistry, and dry deposition process of sulfur components. The results showed that the difference in the aqueous-phase sulfur chemistry among these treatments has the largest impact on the sulfate distribution. Introduction of all the improvements mentioned above brought the model values noticeably closer to in-situ measurements than those in the simplified methods used in the original SPRINTARS model. At the same time, these improvements also brought the computed sulfate column burdens and its vertical distributions into good agreement with other AEROCOM model values. The global annual mean radiative forcing due to the direct effect of anthropogenic sulfate aerosol was thus estimated to be −0.26 W m−2 (−0.30 W m−2 with a different SO2 inventory, whereas the original SPRINTARS model showed −0.18 W m−2 (−0.21 W m−2 with a different SO2 inventory. The magnitude of the difference between original and improved methods was approximately 50% of the uncertainty among estimates by the world's global aerosol models reported by the IPCC-AR4 assessment report. Findings in the present study, therefore, may suggest that the model differences in the

  17. Sources of carbonaceous aerosols and deposited black carbon in the Arctic in winter-spring: implications for radiative forcing

    Directory of Open Access Journals (Sweden)

    Q. Wang

    2011-12-01

    Full Text Available We use a global chemical transport model (GEOS-Chem CTM to interpret observations of black carbon (BC and organic aerosol (OA from the NASA ARCTAS aircraft campaign over the North American Arctic in April 2008, as well as longer-term records in surface air and in snow (2007–2009. BC emission inventories for North America, Europe, and Asia in the model are tested by comparison with surface air observations over these source regions. Russian open fires were the dominant source of OA in the Arctic troposphere during ARCTAS but we find that BC was of prevailingly anthropogenic (fossil fuel and biofuel origin, particularly in surface air. This source attribution is confirmed by correlation of BC and OA with acetonitrile and sulfate in the model and in the observations. Asian emissions are the main anthropogenic source of BC in the free troposphere but European, Russian and North American sources are also important in surface air. Russian anthropogenic emissions appear to dominate the source of BC in Arctic surface air in winter. Model simulations for 2007–2009 (to account for interannual variability of fires show much higher BC snow content in the Eurasian than the North American Arctic, consistent with the limited observations. We find that anthropogenic sources contribute 90% of BC deposited to Arctic snow in January-March and 60% in April–May 2007–2009. The mean decrease in Arctic snow albedo from BC deposition is estimated to be 0.6% in spring, resulting in a regional surface radiative forcing consistent with previous estimates.

  18. Sources of carbonaceous aerosols and deposited black carbon in the Arctic in winter–spring: implications for radiative forcing

    Directory of Open Access Journals (Sweden)

    Q. Wang

    2011-07-01

    Full Text Available We use a global chemical transport model (GEOS-Chem CTM to interpret observations of black carbon (BC and organic aerosol (OA from the NASA ARCTAS aircraft campaign over the North American Arctic in April 2008, together with longer-term records in surface air and in snow. We find that Russian open fires were the dominant source of OA in the troposphere during ARCTAS but that BC was more of anthropogenic origin, particularly in surface air. This source attribution is confirmed by correlation of BC and OA with acetonitrile and sulfate in the model and in the observations. Asian emissions are the main anthropogenic source of BC in the free troposphere but European, Russian and North American sources are also important in surface air. Russian anthropogenic emissions appear to dominate the Arctic source of BC in surface air in winter. Open fire influences on Arctic surface BC in spring are much higher in the Eurasian than in the North American sector. Most of the BC transported to the Arctic in the lower troposphere is deposited within the Arctic, in contrast to the BC transported at higher altitudes. Pan-Arctic 2007–2009 observations of BC concentrations in snow are well reproduced by the model, with maximum values in the Russian Arctic and much lower values in the North American Arctic. We find that anthropogenic sources contribute 90% of BC deposited to Arctic snow in January–March and 57% in April–May 2007–2009. The mean decrease in Arctic snow albedo from BC deposition is estimated to be 0.6% in spring 2007–2009, resulting in a regional surface radiative forcing consistent with previous estimates.

  19. Aerosol optical properties and radiative forcing in the high Himalaya based on measurements at the Nepal Climate Observatory – pyramid site (5100 m a.s.l

    Directory of Open Access Journals (Sweden)

    S. Marcq

    2010-02-01

    Full Text Available Intense anthropogenic emissions over the Indian sub-continent lead to the formation of layers of particulate pollution that can be transported to the high altitude regions of the Himalaya-Hindu-Kush (HKH. Aerosol particles contain a substantial fraction of strongly absorbing material, including black carbon (BC, organic compounds (OC, and dust all of which can contribute to atmospheric warming, in addition to greenhouse gases. Using a 3-year record of continuous measurements of aerosol optical properties, we present a time series of key climate relevant aerosol properties including the aerosol absorption (σap and scattering (σsp coefficients as well as the single-scattering albedo (w. Results of this investigation show substantial seasonal variability of these properties, with long range transport during the pre- and post-monsoon seasons and efficient precipitation scavenging of aerosol particles during the monsoon season. The monthly averaged scattering coefficients range from 0.1 Mm−1 (monsoon to 20 Mm−1 while the average absorption coefficients range from 0.5 Mm−1 to 3.5 Mm−1. Both have their maximum values during the pre-monsoon period (April and reach a minimum during Monsoon (July–August. This leads to w values from 0.86 (pre-monsoon to 0.79 (monsoon seasons. Significant diurnal variability due to valley wind circulation is also reported. Using typical air mass trajectories encountered at the station, and aerosol optical depth (aod measurements, we calculated the resulting direct local radiative forcing due to aerosols. We found that the presence of absorbing particulate material can locally induce an additional top of the atmosphere (TOA forcing of 10 to 20 W m−2 for the first atmospheric layer (500 m above surface. The TOA positive forcing depends on the presence of snow at the surface, and takes place preferentially during episodes

  20. Aerosol optical properties and radiative forcing in the high Himalaya based on measurements at the Nepal Climate Observatory-Pyramid site (5079 m a.s.l.

    Directory of Open Access Journals (Sweden)

    S. Marcq

    2010-07-01

    Full Text Available Intense anthropogenic emissions over the Indian sub-continent lead to the formation of layers of particulate pollution that can be transported to the high altitude regions of the Himalaya-Hindu-Kush (HKH. Aerosol particles contain a substantial fraction of strongly absorbing material, including black carbon (BC, organic compounds (OC, and dust all of which can contribute to atmospheric warming, in addition to greenhouse gases. Using a 3-year record of continuous measurements of aerosol optical properties, we present a time series of key climate relevant aerosol properties including the aerosol absorption (σap and scattering (σsp coefficients as well as the single-scattering albedo (w0. Results of this investigation show substantial seasonal variability of these properties, with long range transport during the pre- and post-monsoon seasons and efficient precipitation scavenging of aerosol particles during the monsoon season. The monthly averaged scattering coefficients range from 0.1 Mm−1 (monsoon to 20 Mm−1 while the average absorption coefficients range from 0.5 Mm−1 to 3.5 Mm−1. Both have their maximum values during the pre-monsoon period (April and reach a minimum during Monsoon (July–August. This leads to dry w0 values from 0.86 (pre-monsoon to 0.79 (monsoon seasons. Significant diurnal variability due to valley wind circulation is also reported. Using aerosol optical depth (AOD measurements, we calculated the resulting direct local radiative forcing due to aerosols for selected air mass cases. We found that the presence of absorbing particulate material can locally induce an additional top of the atmosphere (TOA forcing of 10 to 20 W m−2 for the first atmospheric layer (500 m above surface. The TOA positive forcing depends on the presence of snow at the surface, and takes place preferentially during episodes of

  1. Influence of aerosol vertical distribution on radiative budget and climate

    Science.gov (United States)

    Nabat, Pierre; Michou, Martine; Saint-Martin, David; Watson, Laura

    2016-04-01

    Aerosols interact with shortwave and longwave radiation with ensuing consequences on radiative budget and climate. Aerosols are represented in climate models either using an interactive aerosol scheme including prognostic aerosol variables, or using climatologies, such as monthly aerosol optical depth (AOD) fields. In the first case, aerosol vertical distribution can vary rapidly, at a daily or even hourly scale, following the aerosol evolution calculated by the interactive scheme. On the contrary, in the second case, a fixed aerosol vertical distribution is generally imposed by climatological profiles. The objective of this work is to study the impact of aerosol vertical distribution on aerosol radiative forcing, with ensuing effects on climate. Simulations have thus been carried out using CNRM-CM, which is a global climate model including an interactive aerosol scheme representing the five main aerosol species (desert dust, sea-salt, sulfate, black carbon and organic matter). Several multi-annual simulations covering the past recent years are compared, including either the prognostic aerosol variables, or monthly AOD fields with different aerosol vertical distributions. In the second case, AOD fields directly come from the first simulation, so that all simulations have the same integrated aerosol loads. The results show that modifying the aerosol vertical distribution has a significant impact on radiative budget, with consequences on global climate. These differences, highlighting the importance of aerosol vertical distribution in climate models, probably come from the modification of atmospheric circulation induced by changes in the heights of the different aerosols. Besides, nonlinear effects in the superposition of aerosol and clouds reinforce the impact of aerosol vertical distribution, since aerosol radiative forcing depends highly upon the presence of clouds, and upon the relative vertical position of aerosols and clouds.

  2. Anomalies of the Asian Monsoon Induced by Aerosol Forcings

    Science.gov (United States)

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

    2004-01-01

    Impacts of aerosols on the Asian summer monsoon are studied using the NASA finite volume General Circulation Model (fvGCM), with radiative forcing derived from three-dimensional distributions of five aerosol species i.e., black carbon, organic carbon, soil dust, and sea salt from the Goddard Chemistry Aerosol Radiation and Transport Model (GOCART). Results show that absorbing aerosols, i.e., black carbon and dust, induce large-scale upper-level heating anomaly over the Tibetan Plateau in April and May, ushering in & early onset of the Indian summer monsoon. Absorbing aerosols also I i enhance lower-level heating and anomalous ascent over northern India, intensifying the Indian monsoon. Overall, the aerosol-induced large-scale surface' temperature cooling leads to a reduction of monsoon rainfall over the East Asia continent, and adjacent oceanic regions.

  3. Hygroscopic properties of atmospheric aerosol particles over the Eastern Mediterranean: implications for regional direct radiative forcing under clean and polluted conditions

    Science.gov (United States)

    Stock, M.; Cheng, Y. F.; Birmili, W.; Massling, A.; Wehner, B.; Müller, T.; Leinert, S.; Kalivitis, N.; Mihalopoulos, N.; Wiedensohler, A.

    2011-05-01

    This work examines the effect of direct radiative forcing of aerosols in the eastern Mediterranean troposphere as a function of air mass composition, particle size distribution and hygroscopicity, and relative humidity (RH). During intensive field measurements on the island of Crete, Greece, the hygroscopic properties of atmospheric particles were determined using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) and a Hygroscopicity Differential Mobility Analyzer-Aerodynamic Particle Sizer (H-DMA-APS). Similar to former studies, the H-TDMA identified three hygroscopic sub-fractions of particles in the sub-μm range: a more hygroscopic group, a less hygroscopic group and a nearly hydrophobic particle group. The average hygroscopic particle growth factors at 90 % RH were a significant function of particle mobility diameter (Dp): 1.42 (± 0.05) at 30 nm compared to 1.63 (± 0.07) at 250 nm. The H-DMA-APS identified up to three hygroscopic sub-fractions at mobility diameters of 1.0 and 1.2 μm. The data recorded between 12 August and 20 October 2005 were classified into four distinct synoptic-scale air mass types distinguishing between different regions of origin (western Mediterranean vs. the Aegean Sea) as well as the degree of continental pollution (marine vs. continentally influenced). The hygroscopic properties of particles with diameter Dp≥150 nm showed the most pronounced dependency on air mass origin, with growth factors in marine air masses exceeding those in continentally influenced air masses. Particle size distributions and hygroscopic growth factors were used to calculate aerosol light scattering coefficients at ambient RH using a Mie model. A main result was the pronounced enhancement of particle scattering over the eastern Mediterranean due to hygroscopic growth, both in the marine and continentally influenced air masses. When RH reached its summer daytime values around 70-80 %, up to 50-70 % of the calculated visibility reduction was

  4. Aerosol optical properties in a rural environment near the mega-city Guangzhou, China: implications for regional air pollution, radiative forcing and remote sensing

    OpenAIRE

    Zhang, Y. H.; L. M. Zeng; M. Shao; Hu, M.; Kondo, Y.; Miyazaki, Y.; K. Kita; Wiedensohler, A.; Takegawa, N.; Nowak, A.; P. Achtert; Rose, D.; Schmid, O.; Yang, H.; R. M. Garland

    2008-01-01

    The scattering and absorption of solar radiation by atmospheric aerosols is a key element of the Earth's radiative energy balance and climate. The optical properties of aerosol particles are, however, highly variable and not well characterized, especially near newly emerging mega-cities. In this study, aerosol optical properties were measured at a rural site approximately 60 km northwest of the mega-city Guangzhou in southeast China. The measurements were part of the PRIDE-PRD2006 intens...

  5. Aerosol optical properties in a rural environment near the mega-city Guangzhou, China: implications for regional air pollution and radiative forcing

    OpenAIRE

    R. M. Garland; Yang, H.; Schmid, O.; Rose, D.; Nowak, A.; P. Achtert; Wiedensohler, A.; Takegawa, N.; K. Kita; Miyazaki, Y.; Kondo, Y.; Hu, M.; M. Shao; Zeng, L; Zhang, Y.

    2008-01-01

    The scattering and absorption of solar radiation by atmospheric aerosols is a key element of the Earth's radiative energy balance and climate. The optical properties of aerosol particles are, however, highly variable and not well characterized, especially near newly emerging mega-cities. In this study, aerosol optical properties were measured at a regional background site approximately 60 km northwest of the mega-city Guangzhou in southeast China. The measurements were part of the "...

  6. A novel methodology using MODIS and CERES for assessing the daily radiative forcing of smoke aerosols in large scale over the Amazonia

    Science.gov (United States)

    Sena, E. T.; Artaxo, P.

    2014-12-01

    A new methodology was developed for obtaining daily retrievals of the direct radiative forcing of aerosols (24h-DARF) at the top of the atmosphere (TOA) using satellite remote sensing. For that, simultaneous CERES (Clouds and Earth's Radiant Energy System) shortwave flux at the top of the atmosphere (TOA) and MODIS (Moderate Resolution Spectroradiometer) aerosol optical depth (AOD) retrievals were used. This methodology is applied over a large region of Brazilian Amazonia. We focused our studies on the peak of the biomass burning season (August to September) from 2000 to 2009 to analyse the impact of forest smoke on the radiation balance. To assess the spatial distribution of the DARF, background scenes without biomass burning impacts, were defined as scenes with MODIS AOD code SBDART (Santa Barbara DISORT Radiative Transfer model) was used to expand instantaneous DARFs to 24 h averages. With this methodology it is possible to assess the DARF both at large scale and at high temporal resolution. This new methodology also showed to be more robust, because it considerably reduces statistical sources of uncertainties in the estimates of the DARF, when compared to previous assessments of the DARF using satellite remote sensing. The spatial distribution of the 24h-DARF shows that, for some cases, the mean 24h-DARF presents local values as high as -30 W m-2. The temporal variability of the 24h-DARF along the biomass burning season was also studied and showed large intraseasonal and interannual variability. In an attempt to validate the radiative forcing obtained in this work using CERES and MODIS, those results were compared to coincident AERONET ground based estimates of the DARF. This analysis showed that CERES-MODIS and AERONET 24h-DARF are related as DARFCERES-MODIS24 h = (1.07 ± 0.04)DARFAERONET24 h -(0.0 ± 0.6). This is a significant result, considering that the 24h-DARF retrievals were obtained by applying completely different methodologies, and using different

  7. Direct Radiative Effect and Heating Rate of black carbon aerosol: high time resolution measurements and source-identified forcing effects

    Science.gov (United States)

    Ferrero, Luca; Mocnik, Grisa; Cogliati, Sergio; Comi, Alberto; Degni, Francesca; Di Mauro, Biagio; Colombo, Roberto; Bolzacchini, Ezio

    2016-04-01

    Black carbon (BC) absorbs sunlight in the atmosphere heating it. However, up to now, heating rate (HR) calculations from the divergence of the net radiative flux with altitude or from the modelling activity are too sparse. This work fills the aforementioned gap presenting a new methodology based on a full set of physical equations to experimentally determine both the radiative power density absorbed into a ground-based atmospheric layer (ADRE), and the consequent HR induced by the absorptive component of aerosol. In urban context, it is essentially related to the BC. The methodology is also applicable to natural components (i.e. dust) and is obtained solving the first derivative of the main radiative transfer equations. The ADRE and the consequent HR can be determined coupling spectral aerosol absorption measurements with the spectrally resolved measurements of the direct, diffuse downward radiation and the surface reflected radiance components. Moreover, the spectral absorption of BC aerosol allows its source apportionment (traffic and biomass burning (BB)) allowing the same apportionment on HR. This work reports one year of high-time resolution measurements (5 min) of sunlight absorption and HR induced by BC aerosol over Milan. A unique sampling site was set up from March 2015 with: 1) Aethalometer (AE-31, Magee Scientific, 7-λ), 2) the Multiplexer-Radiometer-Irradiometer which detects downward and reflected radiance (350-1000 nm in 3648 spectral bands) coupled with a rotating shadow-band to measure spectrally-resolved global and diffuse radiation (thus direct), 3) a meteorological station (LSI-Lastem) equipped with 3 pyranometers (global, diffuse and refrected radiation; 300-3000 nm), a thermohygrometer, a barometer, an anemometer, 4) condensation and optical particle counters (TSI 3775 and Grimm 1.107), 5) low volume sampler (FAI Hydra dual sampler, PM2.5 and PM10) for sample collection and chemistry determination. Results concerning the radiative power

  8. Aerosol influence on radiative cooling

    OpenAIRE

    Grassl, Hartmut

    2011-01-01

    Aerosol particles have a complex index of refraction and therefore contribute to atmospheric emission and radiative cooling rates. In this paper calculations of the longwave flux divergence within the atmosphere at different heights are presented including water vapour and aerosol particles as emitters and absorbers. The spectral region covered is 5 to 100 microns divided into 23 spectral intervals. The relevant properties of the aerosol particles, the single scattering albedo and the extinct...

  9. Modulation of aerosol radiative forcing due to mixing state in clear and cloudy-sky: A case study from Delhi National Capital Region, India

    Science.gov (United States)

    Srivastava, Parul; Dey, Sagnik; Srivastava, Atul K.; Singh, Sachchidanand; Tiwari, Suresh; Agarwal, Poornima

    2016-04-01

    Aerosol properties change with the change in mixing state of aerosols and therefore it is a source of uncertainty in estimated aerosol radiative forcing (ARF) from observations or by models assuming a specific mixing state. The problem is important in the Indo-Gangetic Basin, Northern India, where various aerosol types mix and show strong seasonal variations. Quantifying the modulation of ARF by mixing state is hindered by lack of knowledge about proper aerosol composition. Hence, first a detailed chemical composition analysis of aerosols for Delhi National capital region (NCR) is carried out. Aerosol composition is arranged quantitatively into five major aerosol types - accumulation dust, coarse dust, water soluble (WS), water insoluble (WINS), and black carbon (BC) (directly measured by Athelometer). Eight different mixing cases - external mixing, internal mixing, and six combinations of core- shell mixing (BC over dust, WS over dust, WS over BC, BC over WS, WS over WINS, and BC over WINS; each of the combinations externally mixed with other species) have been considered. The spectral aerosol optical properties - extinction coefficient, single scattering albedo (SSA) and asymmetry parameter (g) for each of the mixing cases are calculated and finally 'clear-sky' and 'cloudy-sky' ARF at the top-of-the-atmosphere (TOA) and surface are estimated using a radiative transfer model. Comparison of surface-reaching flux for each of the cases with MERRA downward shortwave surface flux reveals the most likely mixing state. 'BC-WINS+WS+Dust' show least deviation relative to MERRA during the pre-monsoon (MAMJ) and monsoon (JAS) seasons and hence is the most probable mixing states. During the winter season (DJF), 'BC-Dust+WS+WINS' case shows the closest match with MERRA, while external mixing is the most probable mixing state in the post-monsoon season (ON). Lowest values for both TOA and surface 'clear-sky' ARF is observed for 'BC-WINS+WS+ Dust' mixing case. TOA ARF is 0.28±2

  10. Biomass burning emissions over northern Australia constrained by aerosol measurements: II—Model validation, and impacts on air quality and radiative forcing

    Science.gov (United States)

    Luhar, Ashok K.; Mitchell, Ross M.; (Mick) Meyer, C. P.; Qin, Yi; Campbell, Susan; Gras, John L.; Parry, David

    This two-part series investigates the emission and transport of biomass burning aerosol (or particulate matter) across the Top End of the Northern Territory of Australia. In Part I, Meyer et al. [2008. Biomass burning emissions over northern Australia constrained by aerosol measurements: I—Modelling the distribution of hourly emissions. Atmospheric Environment, in press, doi:10.1016/j.atmosenv.2007.10.089.] used a fuel load distribution coupled with a satellite-derived imagery of fire scars and hotspots and the diurnal variation of a fire danger index to estimate hourly emission rates of particulate matter with an aerodynamic diameter of 2.5 μm or less (PM 2.5) for the dry season April-November 2004 at a spatial resolution of 1 km×1 km. In the present paper, these emission rates are used in TAPM, a three-dimensional meteorological and air pollution model, and the modelled PM 2.5 concentrations and aerosol optical depths are compared with satellite and ground-based measurements. This exercise also seeks to fine-tune and validate the emission calculation methodology, a process through which it is found that cases with hotspots without any corresponding fire scars (e.g. in mountainous terrain), which were initially ignored, need to be included to improve the accuracy of model predictions. Overall, the model is able to describe the measurements satisfactorily, considering the issues associated with the model resolution, emission uncertainty, and modelled meteorology. The model hindcasts numerous exceedences of the advisory maximum PM 2.5 exposure limit across the study region, with large areas in excess of 30 exceedences during the study period. Estimated mean top of atmosphere direct radiative forcing due to aerosol shows a seasonal mean of -1.8 W m -2 with a region of strong enhancement over the western portion of the Top End.

  11. Aerosol optical properties in a rural environment near the mega-city Guangzhou, China: implications for regional air pollution, radiative forcing and remote sensing

    Directory of Open Access Journals (Sweden)

    Y. H. Zhang

    2008-09-01

    strongly influenced by fresh emissions into a shallow nocturnal boundary layer. In spite of high photochemical activity during daytime, we found no evidence for strong local production of secondary aerosol mass.

    The average mass scattering efficiencies with respect to PM10 and PM1 concentrations derived from particle size distribution measurements were 2.8 m2 g−1 and 4.1 m2 g−1, respectively. The Ångström exponent exhibited a wavelength dependence (curvature that was related to the ratio of fine and coarse particle mass (PM1/PM10 as well as the surface mode diameter of the fine particle fraction. The results demonstrate consistency between in situ measurements and a remote sensing formalism with regard to the fine particle fraction and volume mode diameter, but there are also systematic deviations for the larger mode diameters. Thus we suggest that more data sets from in situ measurements of aerosol optical parameters and particle size distributions should be used to evaluate formalisms applied in aerosol remote sensing. Moreover, we observed a negative correlation between single scattering albedo and backscatter fraction, and we found that it affects the impact that these parameters have on aerosol radiative forcing efficiency and should be considered in model studies of the PRD and similarly polluted mega-city regions.

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

    OpenAIRE

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

    2005-01-01

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

  13. Spatio-temporal characteristics of aerosol distribution over Tibetan Plateau and numerical simulation of radiative forcing and climate response

    Institute of Scientific and Technical Information of China (English)

    李维亮; 于胜民

    2001-01-01

    In this paper we have analyzed aerosol distribution over the Tibetan Plateau by using the global monthly mean satellite data of Stratospheric Aerosol and Gas Experiment Ⅱ (SAGE Ⅱ).The results are as follows: (1) Stratospheric aerosol optical depth can oscillate in the four seasons. It means that the aerosol optical depth is the thickest in winter and a little thinner in spring and the thinnest in summer and then a little thicker in autumn. We have found that the oscillation is caused by the oscillation of tropopause in different seasons. (2) Stratospheric aerosol comes mainly from sprays of volcano. After eruption of Mount Pinatubo aerosol optical depth in stratosphere over the Tibetan Plateau increases 10 times compared with before. (3) The characteristic of aerosol vertical distribution over the Tibetan Plateau is that there is an extremely high value at the altitude of 70 hPa. The most interesting thing is that the extremely high value can oscillate between 50 hPa and 100 hPa. We have verified that

  14. Indirect determination of single scattering albedo and complex refractive index of atmospheric aerosol from combined spectral sun- and sky-radiance- as well spectral radiation flux-measurements and determination of radiative forcing. Final report; Indirekte Bestimmung der Single Scattering Albedo und des komplexen Brechungsindex des atmosphaerischen Aerosols aus kombinierten spektralen Sonnen- und Himmelsstrahlungs- sowie spektralen Strahlungsflussmessungen und Ermittlung des Strahlungsantriebs. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Hoyningen-Huene, W. von; Burrows, J.P.; Schmidt, T.; Freitag, M.; Waltersdorf, M.; Roth, S.

    2001-07-01

    The insufficient knowledge of radiation parameters of the atmospheric aerosol yields a highly insufficient evaluation of the aerosol impact in different tasks. Climate research (determination of radiative forcing by aerosols), environmental control and monitoring (determination of aerosol impact), satellite remote sensing (atmospheric correction) and aerosol research (radiative properties) require the exact knowledge and complete data sets of optical aerosol parameters. During the closure experiment LACE-98 the main radiative aerosol parameters have been derived experimentally by closure of different atmospheric radiation measurements: spectral aerosol optical thickness, phase function and single scattering albedo. The use of spectral down-welling flux measurements enables the determination of spectral single scattering albedo. Radiative transfer calculations with these parameters have been used for the determination of the top-of-atmosphere radiance to be compared with satellite data (SeaWiFS). Resulting from these comparisons a dynamical surface reflectance model for land surfaces has been derived used in a retrieval procedure for the determination of the aerosol optical thickness from top-of-atmosphere reflectance from multi-spectral satellite data, applicable over land surface. The optical aerosol parameters, the retrieval procedure developed and the obtained regional distribution of the aerosol optical thickness over Germany are presented. (orig.) [German] Die unzureichende Kenntnis von strahlungsrelevanten Aerosolparametern fuehrt zu hohen Unsicherheiten bei der Bewertung des Aerosoleinflusses in verschiedenen Aufgabenbereichen. Klimaforschung (Bestimmung des Strahlungsantriebs durch Aerosole), Umweltkontrolle und Ueberwachung (Bestimmung des Aerosolimpakts), Fernerkundung (Atmosphaerenkorrektur) und Aerosolforschung (Strahlungseigenschaften) benoetigten exakte Kenntnis und komplette Saetze von optischen Aerosolparametern. Durch Schliessung verschiedener

  15. Aerosol optical properties in a rural environment near the mega-city Guangzhou, China: implications for regional air pollution and radiative forcing

    Directory of Open Access Journals (Sweden)

    R. M. Garland

    2008-04-01

    suitable for climate modeling purposes than the 24-h average of 0.82, as the latter value is strongly influenced by fresh emissions into a shallow nocturnal boundary layer. In spite of high photochemical activity during daytime, we found no evidence for strong local production of secondary aerosol mass.

    The relatively low average mass scattering efficiency with respect to PM10 (2.84±0.037 m2 g−1, λ=550 nm indicates a high proportion of mass in the coarse particle fraction (diameter >1 μm. During high pollution episodes, however, the Ångström exponent exhibited a dependence on wavelength, which indicates an enhancement of the fine particle fraction during these periods. A negative correlation between single scattering albedo and backscatter fraction was observed and found to affect the impact that these parameters have on aerosol radiative forcing efficiency.

  16. Observation Study of Aerosol Radiative Properities over China

    Institute of Scientific and Technical Information of China (English)

    MAO Jietai; LI Chengcai

    2006-01-01

    With a simplified radiation balance model, study is performed of aerosol direct radiation forcing in relation to its optical properties and surface reflectance, indicating that with the thickened aerosol layer the earth-atmosphere system may increase or weaken the solar radiation albedo, depending upon different combinations of aerosol single scattering albedo (SSA, ω0), asymmetry factor (g), and surface albedo (αg)rather than relying directly on the aerosol optical depth (δ), which has its value just in proportion to the changed range of albedo alone.As indicated by the model results, systematic observations of aerosol radiative properties are required to make quantitative study of aerosol direct radiative forcing. Observational research of the properties has been undertaken based on ground and space measurements over China, including ground-based sunphotometeraerosol optical depth (AOD), nephelometer-aerosol scattering coefficients, aethalometer-aerosol absorption coefficients, and MODIS products-retrieved AOD. The satellite retrieved AOD is validated against in situ sun photometer measured AOD, ind icating that for eastern China remote sensing given AODs are acceptable owing mainly to lower surface reflectance there whereas for poor vegetation in the north of China the surface reflectance may be underestimated in AOD retrieval. However, appropriate modification of the scheme of aerosol remote sensing is likely to improve the retrieval accuracy. The aerosol single scattering albedo in dry condition is around 0.80 from surface-measured scattering and absorption coefficients. It requires further studies based on more observations to improve our understanding of the issue.

  17. Precipitation Response to Regional Radiative Forcing

    Science.gov (United States)

    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.

  18. Precipitation response to regional radiative forcing

    Directory of Open Access Journals (Sweden)

    D. T. Shindell

    2012-02-01

    Full Text Available 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 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 Potential (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 changes in temperature, they have large benefits for reducing regional disruption of the hydrologic cycle.

  19. Precipitation response to regional radiative forcing

    Directory of Open Access Journals (Sweden)

    D. T. Shindell

    2012-08-01

    Full Text Available 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.

  20. Radiation monitoring by radiation effect of aerosol

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  2. Radiative forcing by contrails

    Energy Technology Data Exchange (ETDEWEB)

    Meerkoetter, R.; Schumann, U. [DLR Oberpfaffenhofen, Wessling (Germany). Inst. fuer Phys. der Atmosphaere; Doelling, D.R.; Minnis, P. [National Aeronautics and Space Administration, Hampton, VA (United States). Langley Research Center; Nakajima, T.; Tsushima, Y. [Tokyo Univ. (Japan). Center for Climate System Research

    1999-08-01

    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 atmosphere. The ice water content is varied as a function of ambient temperature. The model atmospheres include tropical, midlatitude, 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 Wm{sup -2} 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. (orig.) 78 refs.

  3. Natural aerosol direct and indirect radiative effects

    OpenAIRE

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

    2013-01-01

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

  4. Aerosol radiative effects over BIMSTEC regions

    Science.gov (United States)

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

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

  5. Radiative Forcing of the Stratosphere by SO_2 Gas, Silicate Ash, and H_2SO_4 Aerosols Shortly after the 1982 Eruptions of El Chichón

    OpenAIRE

    Gerstell, M. F.; Crisp, Joy; Crisp, David

    1995-01-01

    The 1982 eruptions of the El Chichón volcano injected large quantities of sulfur dioxide gas and silicate ash into the stratosphere. Several studies have shown that the long-lived sulfuric acid aerosols derived from these volcanic effluents produced measurable changes in the radiative heating rates and the global circulation. The radiative and dynamical perturbations associated with the short-lived but more strongly absorbing sulfur dioxide and ash clouds have received much 1ess attention. Th...

  6. Assessment of the Interactions Among Tropospheric Aerosol Loading, Radiative Balance and Clouds Through Examination of Their Multi-decadal Trends

    Science.gov (United States)

    While aerosol radiative effects have been recognized as some of the largest sources of uncertainty among the forcers of climate change, the verification of the spatial and temporal variability of aerosol radiative forcing has remained challenging. Anthropogenic emissions of prima...

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2001-01-01

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

  9. Cloud-Aerosol-Radiation (CAR ensemble modeling system

    Directory of Open Access Journals (Sweden)

    X.-Z. Liang

    2013-04-01

    Full Text Available A Cloud-Aerosol-Radiation (CAR ensemble modeling system has been developed to incorporate the largest choices of alternative parameterizations for cloud properties (cover, water, radius, optics, geometry, aerosol properties (type, profile, optics, radiation transfers (solar, infrared, and their interactions. These schemes form the most comprehensive collection currently available in the literature, including those used by the world leading general circulation models (GCMs. The CAR provides a unique framework to determine (via intercomparison across all schemes, reduce (via optimized ensemble simulations, and attribute specific key factors for (via physical process sensitivity analyses the model discrepancies and uncertainties in representing greenhouse gas, aerosol and cloud radiative forcing effects. This study presents a general description of the CAR system and illustrates its capabilities for climate modeling applications, especially in the context of estimating climate sensitivity and uncertainty range caused by cloud-aerosol-radiation interactions. For demonstration purpose, the evaluation is based on several CAR standalone and coupled climate model experiments, each comparing a limited subset of the full system ensemble with up to 896 members. It is shown that the quantification of radiative forcings and climate impacts strongly depends on the choices of the cloud, aerosol and radiation schemes. The prevailing schemes used in current GCMs are likely insufficient in variety and physically biased in a significant way. There exists large room for improvement by optimally combining radiation transfer with cloud property schemes.

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

    Science.gov (United States)

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

    2016-07-01

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

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

    Science.gov (United States)

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

    2010-05-01

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

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

    Science.gov (United States)

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

    2016-04-01

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

  13. Radiative signature of absorbing aerosol over the Eastern Mediterranean Basin

    Directory of Open Access Journals (Sweden)

    A. K. Mishra

    2014-01-01

    Full Text Available The effects of absorbing aerosols on the atmospheric radiation budget and dynamics over the Eastern Mediterranean region are studied using satellites and ground-based observations, and model calculations, under summer conditions. Climatology of aerosol optical depth (AOD, single scattering albedo (SSA and size parameters were analyzed using multi-year (1999–2012 observations from MODIS, MISR and AERONET. CALIOP-derived aerosol vertical distributions and their classifications are used to calculate the AOD of 4 dominant aerosol types: dust, polluted dust, polluted continental and marine aerosol over the region. The seasonal mean (June–August 2010 AODs are 0.22 ± 0.02, 0.11 ± 0.04, 0.10 ± 0.04 and 0.06 ± 0.01 for polluted dust, polluted continental, dust and marine aerosol, respectively. Changes in the atmospheric temperature profile as a function of absorbing aerosol loading were derived for the same period using observations from the AIRS satellite. We inferred heating rates in the aerosol layer of ~1.7 ± 0.8 K day−1 between 925 and 850 hPa, which is attributed to aerosol absorption of incoming solar radiation. Radiative transfer model (RTM calculations show significant atmospheric warming for dominant absorbing aerosol over the region. A maximum atmospheric forcing of +16.5 ± 7.5 W m−2 is calculated in the case of polluted dust, followed by polluted continental (+7.6 ± 4.4 W m−2 and dust (+7.1 ± 4.3 W m−2. RTM-derived heating rate profiles for dominant absorbing aerosol show warming of 0.1–0.9 K day−1 in the aerosol layer (< 3.0 km altitudes, which primarily depend on AODs of the different aerosol types. Diabatic heating due to absorbing aerosol stabilizes the lower atmosphere, which could significantly reduce the atmospheric ventilation. These conditions can enhance the "pollution pool" over the Eastern Mediterranean.

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

    Science.gov (United States)

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

    2011-02-01

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

  15. Long-term AOD timeseries by Precision Filter Radiometer and assessment of radiative forcing due to the aerosol direct effect at four sites in Switzerland over the last two decades.

    Science.gov (United States)

    Martucci, Giovanni; Vuilleumier, Laurent

    2016-04-01

    In association with the WMO GAW Precision Filter Radiometer network, MeteoSwiss operates four automatic stations measuring the direct solar irradiance in 16 narrow spectral bands within the range 305-1024 nm since 1998. The four sites are (i) Payerne (timeseries 2002-2016), characterized by rural environment (Swiss plateau), (ii) Davos (timeseries 1998-2016), characterized by alpine environment, (iii) Jungfraujoch (timeseries 1999-2016), characterized by alpine environment and partial free tropospheric conditions (mainly in winter, Hermann et al, 2015), and (iv) Locarno-Monti (timeseries 2001-2016), characterized by semi-alpine and urban environment (southern side of the Swiss-Italian Alps). WE present the long-term, almost uninterrupted, timeseries of Aerosol Optical Depth (AOD) in the spectral range 368-1024 nm that has been calculated for each of the four sites along the last two decades. Additionally, we present a study of the trends over almost twenty years of the AOD at different wavelengths. Based on the simulations of the LibRadtran software package for radiative transfer calculations (Meyer and Kylling, 2005) and on the PFR-based timeseries of AOD it has been possible to assess the radiative forcing due to the direct effect of aerosols over Switzerland since 1998.

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

    Science.gov (United States)

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

  17. Aerosol direct radiative impact over the INDOEX area based on passive and active remote sensing

    Science.gov (United States)

    Léon, J.-F.; Chazette, P.; Pelon, J.; Dulac, F.; Randriamiarisoa, H.

    2002-08-01

    This study is dedicated to the direct radiative impact assessment of the pollution aerosol particles during the Indian Ocean Experiment (INDOEX). We use here an instrumental synergy based on active and passive ground-based (Goa University, India), airborne (Mystere 20 research aircraft), and spaceborne (Meteosat-5) devices. An original method based on ground-based active actinic flux measurements is developed to assess the atmospheric, columnar aerosol single scattering albedo. This parameter has been found between 0.88 and 0.93 (at 440 nm) with an absolute uncertainty of 0.04 during the operating period from 11 to 23 March 1999. We have also assessed this parameter off the West Indian coast by comparing simultaneous airborne lidar and flux measurements with radiative transfer simulations. The value retrieved for the atmospheric column is close to 0.83 +/- 0.05 (at 523 nm) in agreement with the coastal value. The horizontal and vertical extent of the aerosol plume is investigated using airborne lidar and Meteosat-5 satellite. Using the Meteosat-5-derived aerosol optical thickness, we have estimated the regional extent of the shortwave aerosol direct radiative forcing. The vertical profile of the aerosol extinction coefficient derived from lidar sounding is used to assess the atmospheric shortwave heating rate induced by the aerosol layer. For an aerosol optical thickness of 0.6 (+/-0.12), as it has been observed in the aerosol plume in late March, the top of atmosphere direct aerosol forcing is -17 (+/-5) W m-2. The surface forcing is between 2.5 and 4.5 higher than the top of atmosphere forcing. This difference leads to a significant heating of the three lowest kilometers of the atmosphere by the aerosols. For an aerosol optical thickness of 0.6, the atmospheric heating rate induced by aerosols is between 0.8 and 1.2 Kd-1 depending on the aerosol single scattering albedo value.

  18. Impacts of emission reductions on aerosol radiative effects

    Science.gov (United States)

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

    2015-05-01

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

  19. Direct radiative forcing of urban aerosols over Pretoria (25.75°S, 28.28°E) using AERONET Sunphotometer data:First scientific results and environmental impact

    Institute of Scientific and Technical Information of China (English)

    Ayodele Joseph Adesina; Kanike Raghavendra Kumar; Venkataraman Sivakumar; Derek Griffith

    2014-01-01

    The present study uses the data collected from Cimel Sunphotometer of Aerosol Robotic Network (AERONET) for the period from January to December,2012 over an urban site,Pretoria (PTR; 25.75°S,28.28°E,1449 m above sea level),South Africa.We found that monthly mean aerosol optical depth (AOD,Ta) exhibits two maxima that occurred in summer (February) and winter (August) having values of 0.36 ± 0.19 and 0.25 ± 0.14,respectively,high-to-moderate values in spring and thereafter,decreases from autumn with a minima in early winter (June) 0.12 ± 0.07.The Angstrom exponents (α440-870) likewise,have its peak in summer (January) 1.70 ± 0.21 and lowest in early winter (June) 1.38 ± 0.26,while the columnar water vapor (CWV) followed AOD pattem with high values (summer) at the beginning of the year (February,2.10 ± 0.37 cm) and low values (winter) in the middle of the year (July,0.66 ± 0.21 cm).The volume size distribution (VSD) in the fine-mode is higher in the summer and spring seasons,whereas in the coarse mode the VSD is higher in the winter and lower in the summer due to the hygroscopic growth of aerosol particles.The single scattering albedo (SSA) ranged from 0.85 to 0.96 at 440 nm over PTR for the entire study period.The averaged aerosol radiative forcing (ARF) computed using SBDART model at the top of the atmosphere (TOA) was-8.78 ± 3.1 W/m2,while at the surface it was-25.69 ± 8.1 W/m2 leading to an atmospheric forcing of +16.91 ± 6.8 W/m2,indicating significant heating of the atmosphere with a mean of 0.47 K/day.

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

    OpenAIRE

    2015-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Nemesure, S.; Wagener, R.; Schwartz, S.E. [Brookhaven National Lab., Upton, New York (United States)

    1996-04-01

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

  2. Direct radiative effect of aerosols emitted by transport: from road, shipping and aviation

    Directory of Open Access Journals (Sweden)

    Y. Balkanski

    2010-05-01

    Full Text Available Aerosols and their precursors are emitted abundantly by transport activities. Transportation constitutes one of the fastest growing activities and its growth is predicted to increase significantly in the future. Previous studies have estimated the aerosol direct radiative forcing from one transport sub-sector, but only one study to our knowledge estimated the range of radiative forcing from the main aerosol components (sulphate, black carbon (BC and organic carbon for the whole transportation sector. In this study, we compare results from two different chemical transport models and three radiation codes under different hypothesis of mixing: internal and external mixing using emission inventories for the year 2000. The main results from this study consist of a positive direct radiative forcing for aerosols emitted by road traffic of +20±11 mW m−2 for an externally mixed aerosol, and of +32±13 mW m−2 when BC is internally mixed. These direct radiative forcings are much higher than the previously published estimate of +3±11 mW m−2. For transport activities from shipping, the net direct aerosol radiative forcing is negative. This forcing is dominated by the contribution of the sulphate. For both an external and an internal mixture, the radiative forcing from shipping is estimated at −26±4 mW m−2. These estimates are in very good agreement with the range of a previously published one (from −46 to −13 mW m−2 but with a much narrower range. By contrast, the direct aerosol forcing from aviation is estimated to be small, and in the range −0.9 to +0.3 mW m−2.

  3. The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure

    Directory of Open Access Journals (Sweden)

    M. Toohey

    2014-06-01

    Full Text Available Observations and simple theoretical arguments suggest that the Northern Hemisphere (NH stratospheric polar vortex is stronger in winters following major volcanic eruptions. However, recent studies show that climate models forced by prescribed volcanic aerosol fields fail to reproduce this effect. We investigate the impact of volcanic aerosol forcing on stratospheric dynamics, including the strength of the NH polar vortex, in ensemble simulations with the Max Planck Institute Earth System Model. The model is forced by four different prescribed forcing sets representing the radiative properties of stratospheric aerosol following the 1991 eruption of Mt. Pinatubo: two forcing sets are based on observations, and are commonly used in climate model simulations, and two forcing sets are constructed based on coupled aerosol–climate model simulations. For all forcings, we find that temperature and zonal wind anomalies in the NH high latitudes are not directly impacted by anomalous volcanic aerosol heating. Instead, high latitude effects result from robust enhancements in stratospheric residual circulation, which in turn result, at least in part, from enhanced stratospheric wave activity. High latitude effects are therefore much less robust than would be expected if they were the direct result of aerosol heating. While there is significant ensemble variability in the high latitude response to each aerosol forcing set, the mean response is sensitive to the forcing set used. Significant differences, for example, are found in the NH polar stratosphere temperature and zonal wind response to two different forcing data sets constructed from different versions of SAGE II aerosol observations. Significant strengthening of the polar vortex, in rough agreement with the expected response, is achieved only using aerosol forcing extracted from prior coupled aerosol–climate model simulations. Differences in the dynamical response to the different forcing sets used

  4. Radiation closure and diurnal cycle of the clear-sky dust instantaneous direct radiative forcing over Arabian Peninsula

    KAUST Repository

    Osipov, Sergey

    2015-04-01

    To better quantify radiative effects of dust over the Arabian Peninsula we have developed a standalone column radiation transport model coupled with the Mie calculations and driven by reanalysis meteorological fields and atmospheric composition. Numerical experiments are carried out for a wide range of aerosol optical depths, including extreme values developed during the dust storm on 18-20 March 2012. Comprehensive ground-based observations and satellite retrievals are used to estimate aerosol optical properties, validate calculations and carry out radiation closure. The broadband surface albedo, fluxes at the bottom and top of the atmosphere as well as instantaneous dust radiative forcing are estimated both from the model and from observations. Diurnal cycle of the the shortwave instantaneous dust direct radiative forcing is studied for a range of aerosol and surface characteristics representative for the Arabian Peninsula. Mechanisms and parameters responsible for diurnal variability of the radiative forcing are evaluated. We found that intrinsic variability of the surface albedo and its dependence on atmospheric conditions along with anisotropic aerosol scattering are mostly responsible for diurnal effects. We also discuss estimates of the climatological dust instantaneous direct radiative forcing over land and the Red Sea using two approaches. The first approach is based on the probability density function of the aerosol optical depth, and the second is based on the climatologically average Spinning Enhanced Visible and Infrared Imager (SEVIRI) aerosol optical depth. Results are compared with Geostationary Earth Radiation Budget (GERB) derived top of the atmosphere climatological forcing over the Red Sea.

  5. Taklimakan dust aerosol radiative heating derived from CALIPSO observations using the Fu-Liou radiation model with CERES constraints

    Directory of Open Access Journals (Sweden)

    J. Huang

    2009-03-01

    Full Text Available The dust aerosol radiative forcing and heating rate over the Taklimakan Desert in northwestern China in July 2006 are estimated using the Fu-Liou radiative transfer model along with satellite observations. The vertical distributions of the dust aerosol extinction coefficient are derived from the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations lidar measurements. The CERES (Cloud and the Earth's Energy Budget Scanner measurements of reflected solar radiation are used to constrain the dust aerosol type in the radiative transfer model, which determines the dust aerosol single-scattering albedo and asymmetry factor as well as the aerosol optical properties spectral dependencies. We find that the dust aerosol radiative heating and effect have a significant impact on the energy budget over the Taklimakan desert. In the atmospheres containing light, moderate and heavy dust layers, the dust aerosols heat the atmosphere by up to 1, 2, and 3 K day−1, respectively. The maximum daily mean radiative heating rate reaches 5.5 K day−1 at 5 km on 29 July. The averaged daily mean net radiative effect of the dust are 44.4, −41.9, and 86.3 W m−2, respectively, at the top of the atmosphere (TOA, surface, and in the atmosphere. Among these effects about two thirds of the warming effect at the TOA is related to the longwave radiation, while about 90% of the atmospheric warming is contributed by the solar radiation. At the surface, about one third of the dust solar radiative cooling effect is compensated by its longwave warming effect. The large modifications of radiative energy budget by the dust aerosols over Taklimakan Desert should have important implications for the atmospheric circulation and regional climate, topics for future investigations.

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

    Science.gov (United States)

    While aerosol radiative effects have been recognized as some of the largest sources of uncertainty among the forcers of climate change, the verification of the spatial and temporal variability of the magnitude and directionality of aerosol radiative forcing has remained challengi...

  7. Impacts of emission reductions on aerosol radiative effects

    Directory of Open Access Journals (Sweden)

    J.-P. Pietikäinen

    2015-05-01

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

  8. Aerosol optical properties and radiative effects over Manora Peak in the Himalayan foothills: seasonal variability and role of transported aerosols

    International Nuclear Information System (INIS)

    The higher altitude regions of Himalayas and Tibetan Plateau are influenced by the dust and black carbon (BC) aerosols from the emissions and long-range transport from the adjoining areas. In this study, we present impacts of advection of polluted air masses of natural and anthropogenic emissions, on aerosol optical and radiative properties at Manora Peak (∼ 2000 m amsl) in central Himalaya over a period of more than two years (February 2006–May 2008). We used the most updated and comprehensive data of chemical and optical properties available in one of the most climatically sensitive region, the Himalaya, to estimate atmospheric radiative forcing and heating rate. Aerosol optical depth (AOD) was found to vary from 0.04 to 0.45 with significantly higher values in summer mainly due to an increase in mineral dust and biomass burning aerosols due to transport. In contrast, single scattering albedo (SSA) varied from 0.74 to 0.88 with relatively lower values during summer, suggesting an increase in absorbing BC and mineral dust aerosols. As a result, a large positive atmospheric radiative forcing (about 28 ± 5 Wm−2) and high values of corresponding heating rate (0.80 ± 0.14 Kday−1) has been found during summer. During the entire observation period, radiative forcing at the top of the atmosphere varied from − 2 to + 14 Wm−2 and from − 3 to − 50 Wm−2 at the surface whereas atmospheric forcing was in the range of 3 to 65 Wm−2 resulting in a heating rate of 0.1–1.8 Kday−1. - Highlights: • Aerosol chemical and optical properties at Manora Peak, in central Himalaya, were significantly affected by dust and black carbon (BC) aerosols from the emissions and long-range transport from the adjoining areas. • Elevated AOD and lower SSA values were observed at Manora Peak during summer. • Enhancement in absorbing aerosols was observed during summer. • Large aerosol radiative forcing and heating rate was observed over the station in the Himalayas

  9. Aerosol optical properties and radiative effects over Manora Peak in the Himalayan foothills: seasonal variability and role of transported aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, A.K. [Indian Institute of Tropical Meteorology (Branch), Prof Ramnath Vij Marg, New Delhi (India); Ram, K. [Institute of Environment and Sustainable Development, Banaras Hindu University, Varanasi (India); Singh, Sachchidanand, E-mail: ssingh@nplindia.org [Radio and Atmospheric Sciences Division, CSIR-National Physical Laboratory, New Delhi (India); Kumar, Sanjeev [Radio and Atmospheric Sciences Division, CSIR-National Physical Laboratory, New Delhi (India); Tiwari, S. [Indian Institute of Tropical Meteorology (Branch), Prof Ramnath Vij Marg, New Delhi (India)

    2015-01-01

    The higher altitude regions of Himalayas and Tibetan Plateau are influenced by the dust and black carbon (BC) aerosols from the emissions and long-range transport from the adjoining areas. In this study, we present impacts of advection of polluted air masses of natural and anthropogenic emissions, on aerosol optical and radiative properties at Manora Peak (∼ 2000 m amsl) in central Himalaya over a period of more than two years (February 2006–May 2008). We used the most updated and comprehensive data of chemical and optical properties available in one of the most climatically sensitive region, the Himalaya, to estimate atmospheric radiative forcing and heating rate. Aerosol optical depth (AOD) was found to vary from 0.04 to 0.45 with significantly higher values in summer mainly due to an increase in mineral dust and biomass burning aerosols due to transport. In contrast, single scattering albedo (SSA) varied from 0.74 to 0.88 with relatively lower values during summer, suggesting an increase in absorbing BC and mineral dust aerosols. As a result, a large positive atmospheric radiative forcing (about 28 ± 5 Wm{sup −2}) and high values of corresponding heating rate (0.80 ± 0.14 Kday{sup −1}) has been found during summer. During the entire observation period, radiative forcing at the top of the atmosphere varied from − 2 to + 14 Wm{sup −2} and from − 3 to − 50 Wm{sup −2} at the surface whereas atmospheric forcing was in the range of 3 to 65 Wm{sup −2} resulting in a heating rate of 0.1–1.8 Kday{sup −1}. - Highlights: • Aerosol chemical and optical properties at Manora Peak, in central Himalaya, were significantly affected by dust and black carbon (BC) aerosols from the emissions and long-range transport from the adjoining areas. • Elevated AOD and lower SSA values were observed at Manora Peak during summer. • Enhancement in absorbing aerosols was observed during summer. • Large aerosol radiative forcing and heating rate was observed

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

    Science.gov (United States)

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

    2000-01-01

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

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

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

    Directory of Open Access Journals (Sweden)

    Y. Gu

    2012-02-01

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

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

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

    Science.gov (United States)

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

    1996-01-01

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

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

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    D. T. Shindell

    2012-08-01

    Full Text Available 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

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

    OpenAIRE

    Strada, Susanna; Unger, Nadine

    2016-01-01

    A global Earth system model is applied to quantify the impacts of direct anthropogenic aerosol effective radiative forcing on gross primary productivity (GPP) and isoprene emission. The impacts of different pollution aerosol sources (anthropogenic, biomass burning, and non-biomass burning) are investigated by performing sensitivity experiments. The model framework includes all known light and meteorological responses of photosynthesis, but uses fixed canopy structures and ph...

  18. New approaches to quantifying aerosol influence on the cloud radiative effect

    OpenAIRE

    G. Feingold; McComiskey, A.; Yamaguchi, T.; Johnson, JS; Carslaw, KS; Schmidt, KS

    2016-01-01

    The topic of cloud radiative forcing associated with the atmospheric aerosol has been the focus of intense scrutiny for decades. The enormity of the problem is reflected in the need to understand aspects such as aerosol composition, optical properties, cloud condensation, and ice nucleation potential, along with the global distribution of these properties, controlled by emissions, transport, transformation, and sinks. Equally daunting is that clouds themselves are complex, turbulent, microphy...

  19. New Approaches to Quantifying Aerosol Influence on the Cloud Radiative Effect

    OpenAIRE

    Feingold, G; McComiskey, A.; Yamaguchi, T.; Johnson, JS; Carslaw, KS; Schmidt, KS

    2016-01-01

    The topic of cloud radiative forcing associated with the atmospheric aerosol has been the focus of intense scrutiny for decades. The enormity of the problem is reflected in the need to understand aspects such as aerosol composition, optical properties, cloud condensation, and ice nucleation potential, along with the global distribution of these properties, controlled by emissions, transport, transformation, and sinks. Equally daunting is that clouds themselves are complex, turbulent, microphy...

  20. Enhancement of the aerosol direct radiative effect by semi-volatile aerosol components: airborne measurements in North-Western Europe

    Directory of Open Access Journals (Sweden)

    W. T. Morgan

    2010-09-01

    Full Text Available A case study of atmospheric aerosol measurements exploring the impact of the vertical distribution of aerosol chemical composition upon the radiative budget in North-Western Europe is presented. Sub-micron aerosol chemical composition was measured by an Aerodyne Aerosol Mass Spectrometer (AMS on both an airborne platform and a ground-based site at Cabauw in the Netherlands. The examined period in May 2008 was characterised by enhanced pollution loadings in North-Western Europe and was dominated by ammonium nitrate and Organic Matter (OM. Both ammonium nitrate and OM were observed to increase with altitude in the atmospheric boundary layer. This is primarily attributed to partitioning of semi-volatile gas phase species to the particle phase at reduced temperature and enhanced relative humidity. Increased ammonium nitrate concentrations in particular were found to strongly increase the ambient scattering potential of the aerosol burden, which was a consequence of the large amount of associated water as well as the enhanced mass. During particularly polluted conditions, increases in aerosol optical depth of 50–100% were estimated to occur due to the observed increase in secondary aerosol mass and associated water uptake. Furthermore, the single scattering albedo was also shown to increase with height in the boundary layer. These enhancements combined to increase the negative direct aerosol radiative forcing by close to a factor of two at the median percentile level. Such increases have major ramifications for regional climate predictions as semi-volatile components are often not included in aerosol models.

    The results presented here provide an ideal opportunity to test regional and global representations of both the aerosol vertical distribution and subsequent impacts in North-Western Europe. North-Western Europe can be viewed as an analogue for the possible future air quality over other polluted regions of the Northern Hemisphere, where

  1. Enhancement of the aerosol direct radiative effect by semi-volatile aerosol components: airborne measurements in North-Western Europe

    Directory of Open Access Journals (Sweden)

    W. T. Morgan

    2010-04-01

    Full Text Available A case study of atmospheric aerosol measurements exploring the impact of the vertical distribution of aerosol chemical composition upon the radiative budget in North-Western Europe is presented. Sub-micron aerosol chemical composition was measured by an Aerodyne Aerosol Mass Spectrometer (AMS on both an airborne platform and a ground-based site at Cabauw in the Netherlands. The examined period in May 2008 was characterised by enhanced pollution loadings in North-Western Europe and was dominated by ammonium nitrate and Organic Matter (OM. Both ammonium nitrate and OM were observed to increase with altitude in the atmospheric boundary layer. This is primarily attributed to partitioning of semi-volatile gas phase species to the particle phase at reduced temperature and enhanced relative humidity. Increased ammonium nitrate concentrations in particular were found to strongly increase the ambient scattering potential of the aerosol burden, which was a consequence of the large amount of associated water as well as the enhanced mass. During particularly polluted conditions, increases in aerosol optical depth of 50–100% were estimated to occur due to the observed increase in secondary aerosol mass and associated water uptake. Furthermore, the single scattering albedo was also shown to increase with height in the boundary layer. These enhancements combined to increase the negative direct aerosol radiative forcing by close to a factor of two at the median percentile level. Such increases have major ramifications for regional climate predictions as semi-volatile components are often not included in aerosol models.

    The results presented here provide an ideal opportunity to test regional and global representations of both the aerosol vertical distribution and subsequent impacts in North-Western Europe. North-Western Europe can be viewed as an analogue for the possible future air quality over other polluted regions of the Northern Hemisphere, where

  2. Modelled and observed changes in aerosols and surface solar radiation over Europe between 1960 and 2009

    Directory of Open Access Journals (Sweden)

    S. T. Turnock

    2015-05-01

    Full Text Available Substantial changes in anthropogenic aerosols and precursor gas emissions have occurred over recent decades due to the implementation of air pollution control legislation and economic growth. The response of atmospheric aerosols to these changes and the impact on climate are poorly constrained, particularly in studies using detailed aerosol chemistry climate models. Here we compare the HadGEM3-UKCA coupled chemistry-climate model for the period 1960 to 2009 against extensive ground based observations of sulfate aerosol mass (1978–2009, total suspended particle matter (SPM, 1978–1998, PM10 (1997–2009, aerosol optical depth (AOD, 2000–2009 and surface solar radiation (SSR, 1960–2009 over Europe. The model underestimates observed sulfate aerosol mass (normalised mean bias factor (NMBF = −0.4, SPM (NMBF = −0.9, PM10 (NMBF = −0.2 and aerosol optical depth (AOD, NMBF = −0.01 but slightly overpredicts SSR (NMBF = 0.02. Trends in aerosol over the observational period are well simulated by the model, with observed (simulated changes in sulfate of −68% (−78%, SPM of −42% (−20%, PM10 of −9% (−8% and AOD of −11% (−14%. Discrepancies in the magnitude of simulated aerosol mass do not affect the ability of the model to reproduce the observed SSR trends. The positive change in observed European SSR (5% during 1990–2009 ("brightening" is better reproduced by the model when aerosol radiative effects (ARE are included (3%, compared to simulations where ARE are excluded (0.2%. The simulated top-of-the-atmosphere aerosol radiative forcing over Europe under all-sky conditions increased by 3 W m−2 during the period 1970–2009 in response to changes in anthropogenic emissions and aerosol concentrations.

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

    Science.gov (United States)

    Strada, S.; Unger, N.

    2015-09-01

    A global Earth system model is applied to quantify the impacts of direct anthropogenic aerosol effective radiative forcing on gross primary productivity (GPP) and isoprene emission. The impacts of different pollution aerosol sources (all anthropogenic, biomass burning and non-biomass burning) are investigated by performing sensitivity experiments. On the global scale, our results show that land carbon fluxes (GPP and isoprene emission) are not sensitive to pollution aerosols, even under a global decline in surface solar radiation (direct + diffuse) by ~ 9 %. At the regional scale, plant productivity (GPP) and isoprene emission show a robust but opposite sensitivity to pollution aerosols, in regions where complex canopies dominate. In eastern North America and Europe, anthropogenic pollution aerosols (mainly from non-biomass burning sources) enhance GPP by +8-12 % on an annual average, with a stronger increase during the growing season (> 12 %). In the Amazon basin and central Africa, biomass burning aerosols increase GPP by +2-5 % on an annual average, with a peak in the Amazon basin during the dry-fire season (+5-8 %). In Europe and China, anthropogenic pollution aerosols drive a decrease in isoprene emission of -2 to -12 % on the annual average. Anthropogenic aerosols affect land carbon fluxes via different mechanisms and we suggest that the dominant mechanism varies across regions: (1) light scattering dominates in the eastern US; (2) cooling in the Amazon basin; and (3) reduction in direct radiation in Europe and China.

  4. Satellite-based estimate of aerosol direct radiative effect over the South-East Atlantic

    Directory of Open Access Journals (Sweden)

    L. Costantino

    2013-09-01

    Full Text Available The net effect of aerosol Direct Radiative Forcing (DRF is the balance between the scattering effect that reflects solar radiation back to space (cooling, and the absorption that decreases the reflected sunlight (warming. The amplitude of these two effects and their balance depends on the aerosol load, its absorptivity, the cloud fraction and the respective position of aerosol and cloud layers. In this study, we use the information provided by CALIOP (CALIPSO satellite and MODIS (AQUA satellite instruments as input data to a Rapid Radiative Transfer Model (RRTM and quantify the shortwave (SW aerosol direct atmospheric forcing, over the South-East Atlantic. The combination of the passive and active measurements allows estimates of the horizontal and vertical distributions of the aerosol and cloud parameters. We use a parametrization of the Single Scattering Albedo (SSA based on the satellite-derived Angstrom coefficient. The South East Atlantic is a particular region, where bright stratocumulus clouds are often topped by absorbing smoke particles. Results from radiative transfer simulations confirm the similar amplitude of the cooling effect, due to light scattering by the aerosols, and the warming effect, due to the absorption by the same particles. Over six years of satellite retrievals, from 2005 to 2010, the South-East Atlantic all-sky SW DRF is −0.03 W m−2, with a spatial standard deviation of 8.03 W m−2. In good agreement with previous estimates, statistics show that a cloud fraction larger than 0.5 is generally associated with positive all-sky DRF. In case of cloudy-sky and aerosol located only above the cloud top, a SSA larger than 0.91 and cloud optical thickness larger than 4 can be considered as threshold values, beyond which the resulting radiative forcing becomes positive.

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

    Science.gov (United States)

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

    2016-06-01

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

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

    Science.gov (United States)

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

    2016-04-01

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

  7. Large methane releases lead to strong aerosol forcing and reduced cloudiness

    DEFF Research Database (Denmark)

    Kurten, T.; Zhou, L.; Makkonen, R.;

    2011-01-01

    contributions from the associated carbon dioxide or ozone increases. Here, we study the effect of strongly elevated methane (CH4) levels on oxidant and aerosol particle concentrations using a combination of chemistry-transport and general circulation models. A 10-fold increase in methane concentrations is......The release of vast quantities of methane into the atmosphere as a result of clathrate destabilization is a potential mechanism for rapid amplification of global warming. Previous studies have calculated the enhanced warming based mainly on the radiative effect of the methane itself, with smaller...... forcing that is comparable in magnitude to the long-wave radiative forcing ("enhanced greenhouse effect") of the added methane. Together, the indirect CH4-O-3 and CH4-OHaerosol forcings could more than double the warming effect of large methane increases. Our findings may help explain the anomalously...

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

    Directory of Open Access Journals (Sweden)

    A. Arola

    2013-08-01

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

  9. Coupling aerosol-cloud-radiative processes in the WRF-Chem model: investigating the radiative impact of elevated point sources

    Directory of Open Access Journals (Sweden)

    E. G. Chapman

    2008-08-01

    Full Text Available The local and regional influence of elevated point sources on summertime aerosol forcing and cloud-aerosol interactions in northeastern North America was investigated using the WRF-Chem community model. The direct effects of aerosols on incoming solar radiation were simulated using existing modules to relate aerosol sizes and chemical composition to aerosol optical properties. Indirect effects were simulated by adding a prognostic treatment of cloud droplet number and adding modules that activate aerosol particles to form cloud droplets, simulate aqueous-phase chemistry, and tie a two-moment treatment of cloud water (cloud water mass and cloud droplet number to an existing radiation scheme. Fully interactive feedbacks thus were created within the modified model, with aerosols affecting cloud droplet number and cloud radiative properties, and clouds altering aerosol size and composition via aqueous processes, wet scavenging, and gas-phase-related photolytic processes. Comparisons of a baseline simulation with observations show that the model captured the general temporal cycle of aerosol optical depths (AODs and produced clouds of comparable thickness to observations at approximately the proper times and places. The model overpredicted SO2 mixing ratios and PM2.5 mass, but reproduced the range of observed SO2 to sulfate aerosol ratios, suggesting that atmospheric oxidation processes leading to aerosol sulfate formation are captured in the model. The baseline simulation was compared to a sensitivity simulation in which all emissions at model levels above the surface layer were set to zero, thus removing stack emissions. Instantaneous, site-specific differences for aerosol and cloud related properties between the two simulations could be quite large, as removing above-surface emission sources influenced when and where clouds formed within the modeling domain. When summed spatially over the finest resolution model

  10. Large methane releases lead to strong aerosol forcing and reduced cloudiness

    Directory of Open Access Journals (Sweden)

    T. Kurtén

    2011-07-01

    Full Text Available The release of vast quantities of methane into the atmosphere as a result of clathrate destabilization is a potential mechanism for rapid amplification of global warming. Previous studies have calculated the enhanced warming based mainly on the radiative effect of the methane itself, with smaller contributions from the associated carbon dioxide or ozone increases. Here, we study the effect of strongly elevated methane (CH4 levels on oxidant and aerosol particle concentrations using a combination of chemistry-transport and general circulation models. A 10-fold increase in methane concentrations is predicted to significantly decrease hydroxyl radical (OH concentrations, while moderately increasing ozone (O3. These changes lead to a 70 % increase in the atmospheric lifetime of methane, and an 18 % decrease in global mean cloud droplet number concentrations (CDNC. The CDNC change causes a radiative forcing that is comparable in magnitude to the longwave radiative forcing ("enhanced greenhouse effect" of the added methane. Together, the indirect CH4-O3 and CH4-OH-aerosol forcings could more than double the warming effect of large methane increases. Our findings may help explain the anomalously large temperature changes associated with historic methane releases.

  11. Large methane releases lead to strong aerosol forcing and reduced cloudiness

    Directory of Open Access Journals (Sweden)

    T. Kurtén

    2011-03-01

    Full Text Available The release of vast quantities of methane into the atmosphere as a result of clathrate destabilization is a potential mechanism for rapid amplification of global warming. Previous studies have calculated the enhanced warming based mainly on the radiative effect of the methane itself, with smaller contributions from the associated carbon dioxide or ozone increases. Here, we study the effect of strongly elevated methane (CH4 levels on oxidant and aerosol particle concentrations using a combination of chemistry-transport and general circulation models. A 10-fold increase in methane concentrations is predicted to significantly decrease hydroxyl radical (OH concentrations, while moderately increasing ozone (O3. These changes lead to a 70% increase in the atmospheric lifetime of methane, and an 18% decrease in global mean cloud droplet number concentrations (CDNC. The CDNC change causes a radiative forcing that is comparable in magnitude to the longwave radiative forcing ("enhanced greenhouse effect" of the added methane. Together, the indirect CH4-O3 and CH4-OH-aerosol forcings could more than double the warming effect of large methane increases. Our findings may help explain the anomalously large temperature changes associated with historic methane releases.

  12. Wave like signatures in aerosol optical depth and associated radiative impacts over the central Himalayan region

    Science.gov (United States)

    Shukla, K. K.; Phanikumar, D. V.; Kumar, K. Niranjan; Reddy, Kishore; Kotamarthi, V. R.; Newsom, Rob K.; Ouarda, Taha B. M. J.

    2015-10-01

    Doppler Lidar and Multi-Filter Rotating Shadowband Radiometer (MFRSR) observations are utilized to show wave like signatures in aerosol optical depth (AOD) during daytime boundary layer evolution over the Himalayan region. Fourier analysis depicted 60-80 min periods dominant during afternoon hours, implying that observed modulations could be plausible reason for the AOD forenoon-afternoon asymmetry which was previously reported. Inclusion of wave amplitude in diurnal variation of aerosol radiative forcing estimates showed ~40% additional warming in the atmosphere relative to mean AOD. The present observations emphasize the importance of wave induced variations in AOD and radiation budget over the site.

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

    Science.gov (United States)

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

    2010-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Lee, S; Richard Dimenna, R

    2007-09-27

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

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

    OpenAIRE

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

    2016-01-01

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

  16. Boundary layer aerosol characteristics at Mahabubnagar during CAIPEEX-IGOC: Modeling the optical and radiative properties

    International Nuclear Information System (INIS)

    An Integrated Ground Observational Campaign (IGOC) was conducted at Mahabubnagar — a tropical rural station in the southern peninsular India, under the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) program during the period from July to November 2011. Measured chemical composition and carbonaceous aerosols from PM2.5 samples were used in an aerosol optical model to deduce crucial aerosol optical properties, which were then used in a radiative transfer model for radiative forcing estimations. The model derived aerosol optical depth (AOD at 500 nm), varied from 0.13 to 0.76 (mean of 0.40 ± 0.18) whereas Ångström exponent (AE) between 0.10 and 0.65 (mean of 0.33 ± 0.17) suggests relative dominance of coarse particles over the station. On the other hand, single scattering albedo (SSA at 500 nm) was found to vary from 0.78 to 0.92 (mean of 0.87 ± 0.04) during the measurement period. The magnitude of absorption Ångström exponent (AAE), varied from 0.83 to 1.33 (mean of 1.10 ± 0.15), suggests mixed type aerosols over the station. Aerosol direct radiative forcing was estimated and found to vary from − 8.9 to − 49.3 W m−2 (mean of − 27.4 ± 11.8 W m−2) at the surface and + 9.7 to + 44.5 W m−2 (mean of + 21.3 ± 9.4 W m−2) in the atmosphere during the course of measurements. The atmospheric forcing was observed to be ∼ 30% higher during October (+ 29 ± 9 W m−2) as compared to August (+ 21 ± 7 W m−2) when the station is mostly influenced by continental polluted aerosols. The result suggests an additional atmospheric heating rate of 0.24 K day−1 during October, which may be crucial for various boundary layer processes in favorable atmospheric conditions. - Highlights: • Modeling the optical and radiative properties of aerosols using measured chemical composition. • Based on optical properties, mixed type aerosols were observed over the station. • Atmospheric forcing was ∼ 30% higher during October as

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

    Science.gov (United States)

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

    2015-04-01

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

  18. Simulating Changes in Tropospheric Aerosol Burden and its Radiative Effects across the Northern Hemisphere: Contrasting Multi-Decadal Trends between Asia and North America

    Science.gov (United States)

    Though aerosol radiative effects have been recognized as some of the largest sources of uncertainty among the forcers of climate change, the verification of the spatial and temporal variability of the magnitude and directionality of aerosol radiative forcing has remained challeng...

  19. Radiative screening of fifth forces

    CERN Document Server

    Burrage, Clare; Millington, Peter

    2016-01-01

    We describe a symmetron model in which the screening of fifth forces arises at the one-loop level through the Coleman-Weinberg mechanism of spontaneous symmetry breaking. We show that such a theory can avoid current constraints on the existence of fifth forces, but still has the potential to give rise to observable deviations from general relativity.

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

    Science.gov (United States)

    Strada, Susanna; Unger, Nadine

    2016-04-01

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

  1. Electromagnetic Radiation can affect the Lift Force

    OpenAIRE

    De Aquino, Fran

    2015-01-01

    Here we show that, under certain circumstances, electromagnetic radiations can strongly reduce the lift force. An aircraft for example, can be shot down when reached by a flux of specific electromagnetic radiation. This discovery can help the aircraft pilots to avoid regions where there are electromagnetic radiations potentially dangerous. Not only the flight of the aircrafts are affected by the electromagnetic radiation, but also the flight of any flying object whose flight depends on the li...

  2. Overview of ACE-Asia Spring 2001 Investigations On Aerosol-Radiation Interactions

    Science.gov (United States)

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

    2002-01-01

    ACE-Asia's extensive measurements from land, ocean, air and space quantified aerosol-radiation interactions. Results from each platform type, plus satellite-suborbital combinations, include: 1. Time series of multiwavelength aerosol optical depth (ADD), Angstrom exponent (alpha), single-scattering albedo (SSA), and size distribution from AERONET radiometry at 13 stations. In China and Korea AOD and alpha were strongly anticorrelated (reflecting transient dust events); dust volume-size modes peaked near 8 microns diameter; and SSA(dust) greater than SSA(pollution). 2. Calculations and measurements of photosynthetically active radiation and aerosols in China yield 24-h average downward surface radiative forcing per AOD(500 nm) of -27 W/sq m (400-700 nm). 3. The Hawaii-Japan cruise sampled a gradient with AOD(500 nm) extremes of 0.1 and 1.1. Shipboard measurements showed that adding dust to pollution increased SSA(550 nm, 55% RH), typically from -0.91 to approx. 0.97. Downwelling 8-12 micron radiances showed aerosol effects, especially in the major April dust event, with longwave forcing estimated at -5 to 15 W/sq m. 4. Extinction profiles from airborne sunphotometry and total-direct-diffuse radiometry show wavelength dependence often varying strongly with height, reflecting layering of dust-dominated over pollution-dominated aerosols. Comparing sunphotometric extinction profiles to those from in situ measurements (number and composition vs size, or scattering and absorption) shows layer heights agree, but extinction sometimes differs. 5. Airborne solar spectral flux radiometry yields absorption spectra for layers. Combining with AOD spectra yields best-fit aerosol single scattering albedo spectra. 6. Visible, NIR and total solar fluxes combined with AOD give radiative forcing efficiencies at surface and aloft.

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Directory of Open Access Journals (Sweden)

    Y. Gu

    2011-12-01

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

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

  5. About Radiation Reaction with Force Approach

    CERN Document Server

    Velazquez, Gustavo Lopez

    2015-01-01

    The difficulty of usual approach to radiation reaction is pointed out , and a possible approach based on the force acting to the charged particle which produces the acceleration itself, is presented. This approach brings about an expression such that acceleration is zero whenever the external force is zero.

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

    Science.gov (United States)

    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.

  7. Testing the linearity of the response to combined greenhouse gas and sulfate aerosol forcing

    OpenAIRE

    Gillett, N.P.; Wehner, M.F.; S. F. B. Tett; Weaver, A. J.

    2004-01-01

    Detection and attribution studies of the temperature response to anthropogenic greenhouse gases and tropospheric sulfate aerosol have relied on the assumption that the responses to each of these forcings add linearly. Using surface temperature from three ensembles of integrations of the second Hadley Centre coupled model (HadCM2) forced with observed changes in greenhouse gases alone, the direct effect of sulfate aerosol alone, and combined changes in greenhouse gases and sulfate aerosol, we ...

  8. Elevated aerosol layers and their radiative impact over Kanpur during monsoon onset period

    Science.gov (United States)

    Sarangi, Chandan; Tripathi, S. N.; Mishra, A. K.; Goel, A.; Welton, E. J.

    2016-07-01

    Accurate information about aerosol vertical distribution is needed to reduce uncertainties in aerosol radiative forcing and its effect on atmospheric dynamics. The present study deals with synergistic analyses of aerosol vertical distribution and aerosol optical depth (AOD) with meteorological variables using multisatellite and ground-based remote sensors over Kanpur in central Indo-Gangetic Plain (IGP). Micro-Pulse Lidar Network-derived aerosol vertical extinction (σ) profiles are analyzed to quantify the interannual and daytime variations during monsoon onset period (May-June) for 2009-2011. The mean aerosol profile is broadly categorized into two layers viz., a surface layer (SL) extending up to 1.5 km (where σ decreased exponentially with height) and an elevated aerosol layer (EAL) extending between 1.5 and 5.5 km. The increase in total columnar aerosol loading is associated with relatively higher increase in contribution from EAL loading than that from SL. The mean contributions of EALs are about 60%, 51%, and 50% to total columnar AOD during 2009, 2010, and 2011, respectively. We observe distinct parabolic EALs during early morning and late evening but uniformly mixed EALs during midday. The interannual and daytime variations of EALs are mainly influenced by long-range transport and convective capacity of the local emissions, respectively. Radiative flux analysis shows that clear-sky incoming solar radiation at surface is reduced with increase in AOD, which indicates significant cooling at surface. Collocated analysis of atmospheric temperature and aerosol loading reveals that increase in AOD not only resulted in surface dimming but also reduced the temperature (˜2-3°C) of lower troposphere (below 3 km altitude). Radiative transfer simulations indicate that the reduction of incoming solar radiation at surface is mainly due to increased absorption by EALs (with increase in total AOD). The observed cooling in lower troposphere in high aerosol loading

  9. Radiation force and balance of electromagnetic momentum

    Science.gov (United States)

    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.

  10. The electric charge of the aerosols under gamma radiation

    International Nuclear Information System (INIS)

    During a PWR type reactor accident, the gamma radiation may create a high ionized atmosphere. In such a situation the aerosols properties knowledge is useful to simulate the particles transport and deposit in the enclosed. The aim of this study is to determine the aerosol charges distribution in a high ionized medium, in function of the ionic properties of the medium. (A.L.B.)

  11. Diurnal cycle of the dust instantaneous direct radiative forcing over the Arabian Peninsula

    KAUST Repository

    Osipov, S.

    2015-08-27

    In this study we attempted to better quantify radiative effects of dust over the Arabian Peninsula and their dependence on input parameters. For this purpose we have developed a stand-alone column radiation transport model coupled with the Mie, T-matrix and geometric optics calculations and driven by reanalysis meteorological fields and atmospheric composition. Numerical experiments were carried out for a wide range of aerosol optical depths, including extreme values developed during the dust storm on 18–20 March 2012. Comprehensive ground-based observations and satellite retrievals were used to estimate aerosol optical properties, validate calculations and carry out radiation closure. The broadband surface albedo, fluxes at the bottom and top of the atmosphere as well as instantaneous dust radiative forcing were estimated both from the model and observations. Diurnal cycle of the shortwave instantaneous dust direct radiative forcing was studied for a range of aerosol and surface characteristics representative of the Arabian Peninsula. Mechanisms and parameters responsible for diurnal variability of the radiative forcing were evaluated. We found that intrinsic variability of the surface albedo and its dependence on atmospheric conditions, along with anisotropic aerosol scattering, are mostly responsible for diurnal effects.

  12. Diurnal cycle of the dust instantaneous direct radiative forcing over the Arabian Peninsula

    Directory of Open Access Journals (Sweden)

    S. Osipov

    2015-04-01

    Full Text Available In this study we attempted to better quantify radiative effects of dust over the Arabian Peninsula and their dependence on input parameters. For this purpose we have developed a standalone column radiation transport model coupled with the Mie calculations and driven by reanalysis meteorological fields and atmospheric composition. Numerical experiments were carried out for a wide range of aerosol optical depths, including extreme values developed during the dust storm on 18–20 March 2012. Comprehensive ground-based observations and satellite retrievals were used to estimate aerosol optical properties, validate calculations and carry out radiation closure. The broadband surface albedo, fluxes at the bottom and top of the atmosphere as well as instantaneous dust radiative forcing were estimated both from the model and observations. Diurnal cycle of the the shortwave instantaneous dust direct radiative forcing was studied for a range of aerosol and surface characteristics representative for the Arabian Peninsula. Mechanisms and parameters responsible for diurnal variability of the radiative forcing were evaluated. We found that intrinsic variability of the surface albedo and its dependence on atmospheric conditions, along with anisotropic aerosol scattering, are mostly responsible for diurnal effects.

  13. Quantifying Aerosol influences on the Cloud Radiative Effect

    Science.gov (United States)

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

    2016-04-01

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

  14. Aerosol radiative effects in the ultraviolet, visible, and near-infrared spectral ranges using long-term aerosol data series over the Iberian Peninsula

    Directory of Open Access Journals (Sweden)

    D. Mateos

    2014-04-01

    Full Text Available A better understanding of the aerosol radiative properties is a crucial challenge for climate change studies. This study aims to provide a complete characterization of aerosol radiative effects in different spectral ranges within the shortwave (SW solar spectrum. For this purpose, long-term datasets of aerosol properties from six AERONET stations located in the Iberian Peninsula (Southwestern Europe are analyzed in term of climatology characterization and trends. Aerosol information is used as input to the libRadtran model in order to determine the aerosol radiative effect at the surface in the ultraviolet (AREUV, visible (AREVIS, near-infrared (ARENIR, and the entire SW range (ARESW under cloud-free conditions. Over the whole Iberian Peninsula, aerosol radiative effects in the different spectral ranges are: −1.1 UV −2, −5.7 VIS −2, −2.8 NIR −2, and −9.5 SW −2. The four variables showed positive statistically significant trends between 2004 and 2012, e.g., ARESW increased +3.6 W m−2 per decade. This fact is linked to the decrease in the aerosol load, which presents a trend of −0.04 per unit of aerosol optical depth at 500 nm per decade, hence a reduction of aerosol effect on solar radiation at the surface is seen. Monthly means of ARE show a seasonal pattern with larger values in spring and summer. The aerosol forcing efficiency (AFE, ARE per unit of aerosol optical depth, is also evaluated in the four spectral ranges. AFE exhibits a dependence on single scattering albedo and a weaker one on Ångström exponent. AFE is larger (in absolute value for small and absorbing particles. The contributions of the UV, VIS, and NIR ranges to the SW efficiency vary with the aerosol types. Aerosol size determines the fractions of AFEVIS/AFESW and AFENIR/AFESW. VIS range is the dominant region for all types, although non-absorbing large particles cause a more equal contribution of VIS and NIR intervals. The AFEUV / AFESW ratio shows a

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

    Science.gov (United States)

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

    2016-01-01

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

  16. Radiative Forcing Over Ocean by Ship Wakes

    Science.gov (United States)

    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.

  17. Collective effects in the radiation pressure force

    CERN Document Server

    Bachelard, R; Guerin, W; Kaiser, R

    2016-01-01

    We discuss the role of diffuse, Mie and cooperative scattering on the radiation pressure force acting on the center of mass of a cloud of cold atoms. Even though a mean-field Ansatz (the `timed Dicke state'), previously derived from a cooperative scattering approach, has been shown to agree satisfactorily with experiments, diffuse scattering also describes very well most features of the radiation pressure force on large atomic clouds. We compare in detail an incoherent, random walk model for photons and a diffraction approach to the more complete description based on coherently coupled dipoles. We show that a cooperative scattering approach, although it provides a quite complete description of the scattering process, is not necessary to explain the previous experiments on the radiation pressure force.

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

    Science.gov (United States)

    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).

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-07-11

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

  20. Radiation Transfer Model for Aerosol Events in the Earth Atmosphere

    Science.gov (United States)

    Mukai, Sonoyo; Yokomae, Takuma; Nakata, Makiko; Sano, Itaru

    Recently large scale-forest fire, which damages the Earth environment as biomass burning and emission of carbonaceous particles, frequently occurs due to the unstable climate and/or global warming tendency. It is also known that the heavy soil dust is transported from the China continent to Japan on westerly winds, especially in spring. Furthermore the increasing emis-sions of anthropogenic particles associated with continuing economic growth scatter serious air pollutants. Thus atmospheric aerosols, especially in Asia, are very complex and heavy loading, which is called aerosol event. In the case of aerosol events, it is rather difficult to do the sun/sky photometry from the ground, however satellite observation is an effective for aerosol monitoring. Here the detection algorithms from space for such aerosol events as dust storm or biomass burn-ing are dealt with multispectral satellite data as ADEOS-2/GLI, Terra/Aqua/MODIS and/or GOSAT/CAI first. And then aerosol retrieval algorithms are examined based on new radiation transfer code for semi-infinite atmosphere model. The derived space-based results are validated with ground-based measurements and/or model simulations. Namely the space-or surface-based measurements, multiple scattering calculations and model simulations are synthesized together for aerosol retrieval in this work.

  1. Organic aerosols

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2013-12-01

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

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

    Directory of Open Access Journals (Sweden)

    A. Arola

    2007-08-01

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

  4. Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling

    Directory of Open Access Journals (Sweden)

    T. S. Bates

    2006-01-01

    Full Text Available The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001. Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regions downwind of major urban/population centers (North Indian Ocean (NIO during INDOEX, the Northwest Pacific Ocean (NWP during ACE-Asia, and the Northwest Atlantic Ocean (NWA during ICARTT, incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART. Measurements of burdens, extinction optical depth (AOD, and direct radiative effect of aerosols (DRE – change in radiative flux due to total aerosols are used as measurement-model check points to assess uncertainties. In-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity are used as input parameters to two radiative transfer models (GFDL and University of Michigan to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative

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

    Science.gov (United States)

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

    2016-04-01

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

  6. Sensitivity Analysis on Fu-Liou-Gu Radiative Transfer Model for different lidar aerosol and cloud profiles

    Science.gov (United States)

    Lolli, Simone; Madonna, Fabio; Rosoldi, Marco; Pappalardo, Gelsomina; Welton, Ellsworth J.

    2016-04-01

    The aerosol and cloud impact on climate change is evaluated in terms of enhancement or reduction of the radiative energy, or heat, available in the atmosphere and at the Earth's surface, from the surface (SFC) to the Top Of the Atmosphere (TOA) covering a spectral range from the UV (extraterrestrial shortwave solar radiation) to the far-IR (outgoing terrestrial longwave radiation). Systematic Lidar network measurements from permanent observational sites across the globe are available from the beginning of this current millennium. From the retrieved lidar atmospheric extinction profiles, inputted in the Fu-Liou-Gu (FLG) Radiative Transfer code, it is possible to evaluate the net radiative effect and heating rate of the different aerosol species and clouds. Nevertheless, the lidar instruments may use different techniques (elastic lidar, Raman lidar, multi-wavelength lidar, etc) that translate into uncertainty of the lidar extinction retrieval. The goal of this study is to assess, applying a MonteCarlo technique and the FLG Radiative Transfer model, the sensitivity in calculating the net radiative effect and heating rate of aerosols and clouds for the different lidar techniques, using both synthetic and real lidar data. This sensitivity study is the first step to implement an automatic algorithm to retrieve the net radiative forcing effect of aerosols and clouds from the long records of aerosol measurements available in the frame of EARLINET and MPLNET lidar networks.

  7. Inhomogeneous radiative forcing of homogeneous greenhouse gases

    Science.gov (United States)

    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.

  8. Radiative forcing calculations for CH3Cl

    International Nuclear Information System (INIS)

    Methyl chloride, CH3Cl, is the major natural source of chlorine to the stratosphere. The production of CH3Cl is dominated by biological sources from the oceans and biomass burning. Production has a seasonal cycle which couples with the short lifetime of tropospheric CH3Cl to produce nonuniform global mixing. As an absorber of infrared radiation, CH3Cl is of interest for its potential affect on the tropospheric energy balance as well as for its chemical interactions. In this study, we estimate the radiative forcing and global warming potential (GWP) of CH3Cl. Our calculations use an infrared radiative transfer model based on the correlated k-distribution algorithm for band absorption. Global and annual average vertical profiles of temperature and trace gas concentration were assumed. The effects of clouds are modeled using three layers of global and annual average cloud optical properties. A radiative forcing value of 0.0053 W/m2ppbv was obtained for CH3Cl and is approximately linear in the background abundance. This value is about 2 percent of the forcing of CFC-11 and about 300 times the forcing of CO2, on a per molecule basis. The radiative forcing calculation for CH3Cl is used to estimate the global warming potential (GWP) of CH3Cl. The results give GWPs for CH3Cl of the order of 25 at a time of 20 years(CO2 = 1). This result indicates that CH3Cl has the potential to be a major greenhouse gas if significant human related emissions were introduced into the atmosphere

  9. Assessment of Individual Direct Radiative Effects of Major Aerosol Species in East Asia

    Institute of Scientific and Technical Information of China (English)

    HAN Xiao; ZHANG Mei-Gen

    2012-01-01

    To assess individual direct radiative effects of diverse aerosol species on a regional scale, the air quality modeling system RAMS-CMAQ (Regional Atmospheric Modeling System and Community Multiscale Air Quality) coupled with an aerosol optical properties/radiative transfer module was used to simulate the temporal and spatial distributions of their optical and radiative properties over East Asia throughout 2005. Annual and seasonal averaged aerosol direct radiative forcing (ADRF) of all important aerosols and individual components, such as sulfate, nitrate, ammonium, black carbon (BC), organic carbon (OC), and dust at top-of-atmosphere (TOA) in clear sky are analyzed. Analysis of the model results shows that the annual average ADRF of all important aerosols was in the range of 0 to -18 W m-z, with the maximum values mainly distributed over the Sichuan Basin. The direct radiative effects of sulfate, nitrate, and ammonium make up most of the total ADRF in East Asia, being concentrated mainly over North and Southeast China. The model domain is also divided into seven regions based on different administrative regions or countries to investigate detailed information about regional ADRF variations over East Asia. The model results show that the ADRFs of sulfate, ammonium, BC, and OC were stronger in summer and weaker in winter over most regions of East Asia, except over Southeast Asia. The seasonal variation in the ADRF of nitrate exhibited the opposite trend. A strong ADRF of dust mainly appeared in spring over Northwest China and Mongolia.

  10. Changes in Atmospheric Constituents and in Radiative Forcing. Chapter 2

    International Nuclear Information System (INIS)

    This chapter updates information taken from Chapters 3 to 6 of the IPCC Working Group I Third Assessment Report. It concerns itself with trends in forcing agents and their precursors since 1750, and estimates their contribution to the radiative forcing (RF) of the climate system. Discussion of the understanding of atmospheric composition changes is limited to explaining the trends in forcing agents and their precursors. Areas where significant developments have occurred since the TAR are highlighted. The chapter draws on various assessments since the TAR, in particular the 2002 World Meteorological Organization (WMO), United Nations Environment Programme (UNEP) Scientific Assessment of Ozone Depletion (2003) and the IPCC Technology and Economic Assessment Panel (TEAP) special report on Safeguarding the Ozone Layer and the Global Climate System (2005). The chapter assesses anthropogenic greenhouse gas changes, aerosol changes and their impact on clouds, aviation-induced contrails and cirrus changes, surface albedo changes and natural solar and volcanic mechanisms. The chapter reassesses the 'radiative forcing' concept (Sections 2.2 and 2.8), presents spatial and temporal patterns of RF, and examines the radiative energy budget changes at the surface. For the long-lived greenhouse gases (carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), chlorofluoro-carbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulphur hexafluoride (SF6), hereinafter collectively referred to as the LLGHGs; Section 2.3), the chapter makes use of new global measurement capabilities and combines long-term measurements from various networks to update trends through 2005. Compared to other RF agents, these trends are considerably better quantified; because of this, the chapter does not devote as much space to them as previous assessments (although the processes involved and the related budgets are further discussed in Sections 7.3 and 7

  11. Reflective ‘cool’ roofs under aerosol-burdened skies: radiative benefits across selected Indian cities

    International Nuclear Information System (INIS)

    The use of reflective surfaces offers one low-cost solution for reducing solar loading to urban environments and the Earth that should be considered as part of sustainable urban design. Here, we characterize the radiative benefits, i.e. the additional shortwave radiation leaving the atmosphere, from the installation of highly reflective ‘cool’ roofs in urban areas in India that face relatively large local aerosol burdens. We use a previously tested column radiative transfer model to estimate the energy per unit area reflected to space from increasing the surface albedo at six cities within India. The model is used to characterize radiative transfer each day over five years (2008–2012) based on mid-day satellite retrievals of MODIS aerosol depth, cloud water path, and average surface albedo and MERRA atmospheric profiles of temperature and composition. Compared against ten months of field observations in two cities, the model derived incoming surface shortwave radiation estimates relative to observations show small biases (0.5% and −2.6%, at Pantnagar and Nainital, respectively). Despite the high levels of local aerosols we found cool roofs provided significant radiative benefits at all locations. Averaged over the five year period we found that increasing the albedo of 1 m2 of roof area by 0.5 would reflect to space 0.9–1.2 kWh daily from 08:30–15:30 LST, depending on location. This is equivalent to a constant forcing of 37–50 W m−2 (equivalent to reducing CO2 emissions by 74 to 101 kg CO2 m−2 roof area). Last, we identify a co-benefit of improving air quality, in that removing aerosols from the atmosphere could increase the radiative benefits from cool roofs by 23–74%, with the largest potential increase found at Delhi and the smallest change found at Nainital. (letter)

  12. Reflective ‘cool’ roofs under aerosol-burdened skies: radiative benefits across selected Indian cities

    Science.gov (United States)

    Millstein, D. E.; Fischer, M. L.

    2014-10-01

    The use of reflective surfaces offers one low-cost solution for reducing solar loading to urban environments and the Earth that should be considered as part of sustainable urban design. Here, we characterize the radiative benefits, i.e. the additional shortwave radiation leaving the atmosphere, from the installation of highly reflective ‘cool’ roofs in urban areas in India that face relatively large local aerosol burdens. We use a previously tested column radiative transfer model to estimate the energy per unit area reflected to space from increasing the surface albedo at six cities within India. The model is used to characterize radiative transfer each day over five years (2008-2012) based on mid-day satellite retrievals of MODIS aerosol depth, cloud water path, and average surface albedo and MERRA atmospheric profiles of temperature and composition. Compared against ten months of field observations in two cities, the model derived incoming surface shortwave radiation estimates relative to observations show small biases (0.5% and -2.6%, at Pantnagar and Nainital, respectively). Despite the high levels of local aerosols we found cool roofs provided significant radiative benefits at all locations. Averaged over the five year period we found that increasing the albedo of 1 m2 of roof area by 0.5 would reflect to space 0.9-1.2 kWh daily from 08:30-15:30 LST, depending on location. This is equivalent to a constant forcing of 37-50 W m-2 (equivalent to reducing CO2 emissions by 74 to 101 kg CO2 m-2 roof area). Last, we identify a co-benefit of improving air quality, in that removing aerosols from the atmosphere could increase the radiative benefits from cool roofs by 23-74%, with the largest potential increase found at Delhi and the smallest change found at Nainital.

  13. Reflective "Cool" Roofs Under Aerosol-Burdened Skies: Radiative Benefits Across Selected Indian Cities

    Science.gov (United States)

    Millstein, D.; Fischer, M. L.

    2014-12-01

    The use of reflective surfaces offers one low-cost solution for reducing solar loading to urban environments and the Earth that should be considered as part of sustainable urban design. Here, we characterize the radiative benefits, i.e. the additional shortwave radiation leaving the atmosphere, from the installation of highly reflective "cool" roofs in urban areas in India that face relatively large local aerosol burdens. We use a previously tested column radiative transfer model to estimate the energy per unit area reflected to space from increasing the surface albedo at six cities within India. The model is used to characterize radiative transfer each day over five years (2008-2012) based on mid-day satellite retrievals of MODIS aerosol depth, cloud water path, and average surface albedo and MERRA atmospheric profiles of temperature and composition. Compared against 10 months of field observations in two cities, the model derived incoming surface shortwave radiation estimates relative to observations show small biases (0.5% and -2.6%, at Pantnagar and Nainital, respectively). Despite the high levels of local aerosols we found cool roofs provided significant radiative benefits at all locations. Averaged over the five year period we found that increasing the albedo of 1 m-2 of roof area by 0.5 would reflect to space 0.9 - 1.2 kWh daily from 08:30 - 15:30 LST, depending on location. This is equivalent to a constant forcing of 37 - 50 W m-2 (equivalent to reducing CO2 emissions by 74 to 101 kg CO2 m-2 roof area). Last, we identify a co-benefit of improving air quality, in that removing aerosols from the atmosphere could increase the radiative benefits from cool roofs by 23 - 74%, with the largest potential increase found at Delhi and the smallest change found at Nainital.

  14. Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling

    Directory of Open Access Journals (Sweden)

    T. S. Bates

    2006-01-01

    Full Text Available The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001. Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regions downwind of major urban/population centers (North Indian Ocean (NIO during INDOEX, the Northwest Pacific Ocean (NWP during ACE-Asia, and the Northwest Atlantic Ocean (NWA during ICARTT, incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART. Measurements of burdens, extinction optical depth (AOD, and direct radiative effect of aerosols (DRE – change in radiative flux due to total aerosols are used as measurement-model check points to assess uncertainties. In-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity are used as input parameters to two radiative transfer models (GFDL and University of Michigan to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative

  15. Global aerosol transport and consequences for the radiation budget

    International Nuclear Information System (INIS)

    Man's activities may influence global climate by changing the atmospheric composition and surface characteristics and by waste heat. Most prominent within this discussion is the increase or decrease of radiatively active trace gases like CO/sub 2/, N/sub 2/O, O/sub 3/, and others. The general opinion is converging towards a greenhouse effect as a combined action of all trace gases, whose exact magnitude is uncertain mainly because of the unknown reaction of water cycle. The aim of our global 2-D (resolving latitude and height) aerosol transport model is the calculation of aerosol particle number density profiles as a function of latitude for present natural plus anthropogenic emissions. The aerosol transport model uses prescribed meridonal circulation, diffusivity factors and cloud climatology for January as well as July. All these latitude and height dependent input parameters were taken from well known sources. The fixed climatology excludes the feedback of aerosol particle parameter changes on mean circulation. However, the radiative parameters of six clouds types are modified, although they possess by adoption of the Telegadas and London (1954) cloud climatology prescribed amount and height. The inclusion of the feedback on mean circulation seems premature at present. Adding particles either accounting for natural emissions or natural anthropogenic emission and removing particles by all known sinks outside and within clouds gives us - for the stationary state - vertical profiles of aerosol number density in three sizes classes as a function of latitude. These profiles in turn are input for radiation flux calculations in clear and cloudy areas in order to assess net flux changes caused by the present aerosol load in comparison to a scenario without anthropogenic emissions. The net flux changes finally are compared to those calculated for increased CO/sub 2/ levels

  16. Accumulation of aerosols over the Indo-Gangetic plains and southern slopes of the Himalayas: distribution, properties and radiative effects during the 2009 pre-monsoon Season

    Directory of Open Access Journals (Sweden)

    R. Gautam

    2011-05-01

    Full Text Available We examine the distribution of aerosols and associated optical/radiative properties in the Gangetic-Himalayan region from simultaneous radiometric measurements over the Indo-Gangetic Plains (IGP and the foothill/slopes of the Himalayas during the 2009 pre-monsoon season. Enhanced dust transport extending from the Southwest Asian arid regions into the IGP, results in seasonal mean (April–June aerosol optical depths of over 0.6 – highest over southern Asia. The influence of dust loading is greater over the western IGP as suggested by pronounced coarse mode peak in aerosol size distribution and spectral single scattering albedo (SSA. The transported dust in the IGP, driven by prevailing westerly airmass, is found to be more absorbing (SSA550 nm ~0.89 than the near-desert region in NW India (SSA550 nm ~0.91 suggesting mixing with carbonaceous aerosols in the IGP. On the contrary, significantly reduced dust transport is observed over eastern IGP and foothill/elevated slopes in Nepal where strongly absorbing haze is prevalent, associated with upslope transport of pollution, as indicated by low values of SSA (0.85–0.9 for the wavelength range of 440–1020 nm, suggesting presence of more absorbing aerosols compared to IGP. Assessment of the radiative impact of aerosols over NW India suggests diurnal mean reduction in solar radiation fluxes of 19–23 Wm−2 at surface (12–15 % of the surface solar insolation. Based on limited observations of aerosol optical properties during the pre-monsoon period and comparison of our radiative forcing estimates with published literature, there exists spatial heterogeneity in the regional aerosol forcing, associated with the absorbing aerosol distribution over northern India, with both diurnal mean surface forcing and forcing efficiency over the IGP exceeding that over NW India. Additionally, the role of the seasonal progressive buildup of aerosol loading and water vapor is

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

    Science.gov (United States)

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

    2016-04-01

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

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

    Directory of Open Access Journals (Sweden)

    N. E. Rosário

    2012-07-01

    Full Text Available Intra-seasonal variability of smoke aerosol optical depth (AOD and downwelling solar irradiance at the surface during the 2002 biomass burning season in South America was modeled using the Coupled Chemistry-Aerosol-Tracer Transport model to the Brazilian developments on the Regional Atmospheric Modeling System (CCATT-BRAMS. Measurements of AOD from the AErosol RObotic NETwork (AERONET and solar irradiance at the surface from the Solar Radiation Network (SolRad-NET were used to evaluate model results. In general, the major features associated with AOD evolution over the southern part of the Amazon Basin and cerrado ecosystem are captured by the model. The main discrepancies were found for high aerosol loading events. In the northeastern portion of the Amazon Basin the model systematically underestimated AOD. This is likely due to the cloudy nature of the region, preventing accurate detection of the fire spots used in the emission model. Moreover, measured AOD were very often close to background conditions and emissions other than smoke were not considered in the simulation. Therefore, under the background scenario, one would expect the model to underestimate AOD. The issue of high aerosol loading events in the southern part of the Amazon and cerrado is also discussed in the context of emission shortcomings. The Cuiabá cerrado site was the only one where the highest quality AERONET data were unavailable. Thus, lower quality data were used. Root-mean-square-error (RMSE between the model and observations decreased from 0.48 to 0.17 when extreme AOD events (AOD550 nm ≥ 1.0 and Cuiabá were excluded from analysis. Downward surface solar irradiance comparisons also followed similar trends when extremes AOD were excluded. This highlights the need to improve the modelling of the regional smoke plume in order to enhance the accuracy of the radiative energy budget. Aerosol optical model based on the mean intensive properties of smoke from the

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

    Science.gov (United States)

    Bollasina, Massimo; Ming, Yi

    2013-04-01

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

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

    Directory of Open Access Journals (Sweden)

    H. Bian

    2009-04-01

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

  1. Sensitivity of modelled sulfate radiative forcing to DMS concentration and air-sea flux formulation

    Science.gov (United States)

    Tesdal, J.-E.; Christian, J. R.; Monahan, A. H.; von Salzen, K.

    2015-09-01

    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 radiative forcing 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 radiation 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 radiative forcing is larger than that of spatial distribution, and is significant at global scale.

  2. Variability in radiative properties of major aerosol types: A year-long study over Delhi—An urban station in Indo-Gangetic Basin

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, A.K., E-mail: atul@tropmet.res.in [Indian Institute of Tropical Meteorology (Branch), Prof. Ramnath Vij Marg, New Delhi (India); Yadav, V.; Pathak, V. [Department of Civil Engineering, Institute of Engineering and Technology, Lucknow (India); Singh, Sachchidanand [Radio and Atmospheric Sciences Division, CSIR-National Physical Laboratory, New Delhi (India); Tiwari, S.; Bisht, D.S. [Indian Institute of Tropical Meteorology (Branch), Prof. Ramnath Vij Marg, New Delhi (India); Goloub, P. [Laboratoire d' Optique Atmopshérique, Lille University/CNRS, Villeneuve d' Ascq (France)

    2014-03-01

    Aerosol measurements over an urban site at Delhi in the western Ganga basin, northern India, were carried out during 2009 using a ground-based automatic sun/sky radiometer to identify their different types and to understand their possible radiative implications. Differentiation of aerosol types over the station was made using the appropriate thresholds for size-distribution of aerosols (i.e. fine-mode fraction, FMF at 500 nm) and radiation absorptivity (i.e. single scattering albedo, SSA at 440 nm). Four different aerosol types were identified, viz., polluted dust (PD), polluted continent (PC), mostly black carbon (MBC) and mostly organic carbon (MOC), which contributed ∼ 48%, 32%, 11% and 9%, respectively to the total aerosols. Interestingly, the optical properties for these aerosol types differed considerably, which were further used, for the first time, to quantify their radiative implications over this station. The highest atmospheric forcing was observed for PC aerosol type (about + 40 W m{sup −2}, along with the corresponding atmospheric heating rate of 1.10 K day{sup −1}); whereas the lowest was for MBC aerosol type (about + 25 W m{sup −2}, along with the corresponding atmospheric heating rate of 0.69 K day{sup −1}). - Highlights: • Four different aerosol types were identified using sun/sky radiometer measurements. • Total aerosol was contributed from ∼ 48% PD, 32% PC, 11% MBC and 9% MOC aerosols. • AOD was similar for each aerosol type, with varying SSA as PD > MOC > PC > MBC aerosols. • Highest atmospheric forcing was observed for PC and the lowest for MBC aerosols.

  3. Variability in radiative properties of major aerosol types: A year-long study over Delhi—An urban station in Indo-Gangetic Basin

    International Nuclear Information System (INIS)

    Aerosol measurements over an urban site at Delhi in the western Ganga basin, northern India, were carried out during 2009 using a ground-based automatic sun/sky radiometer to identify their different types and to understand their possible radiative implications. Differentiation of aerosol types over the station was made using the appropriate thresholds for size-distribution of aerosols (i.e. fine-mode fraction, FMF at 500 nm) and radiation absorptivity (i.e. single scattering albedo, SSA at 440 nm). Four different aerosol types were identified, viz., polluted dust (PD), polluted continent (PC), mostly black carbon (MBC) and mostly organic carbon (MOC), which contributed ∼ 48%, 32%, 11% and 9%, respectively to the total aerosols. Interestingly, the optical properties for these aerosol types differed considerably, which were further used, for the first time, to quantify their radiative implications over this station. The highest atmospheric forcing was observed for PC aerosol type (about + 40 W m−2, along with the corresponding atmospheric heating rate of 1.10 K day−1); whereas the lowest was for MBC aerosol type (about + 25 W m−2, along with the corresponding atmospheric heating rate of 0.69 K day−1). - Highlights: • Four different aerosol types were identified using sun/sky radiometer measurements. • Total aerosol was contributed from ∼ 48% PD, 32% PC, 11% MBC and 9% MOC aerosols. • AOD was similar for each aerosol type, with varying SSA as PD > MOC > PC > MBC aerosols. • Highest atmospheric forcing was observed for PC and the lowest for MBC aerosols

  4. Resonant acoustic radiation force optical coherence elastography

    OpenAIRE

    Qi, Wenjuan; Li, Rui; Ma, Teng; Li, Jiawen; Kirk Shung, K.; Zhou, Qifa; Chen, Zhongping

    2013-01-01

    We report on a resonant acoustic radiation force optical coherence elastography (ARF-OCE) technique that uses mechanical resonant frequency to characterize and identify tissues of different types. The linear dependency of the resonant frequency on the square root of Young's modulus was validated on silicone phantoms. Both the frequency response spectrum and the 3D imaging results from the agar phantoms with hard inclusions confirmed the feasibility of deploying the resonant frequency as a mec...

  5. Radiative forcing calculations for CH3Br

    International Nuclear Information System (INIS)

    Methyl Bromide, CH3Br, 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--13μ, was determined using a well tested Coriolis resonance and ell-doubling (and ell-resonance) computational system. A radiative forcing value of 0.00493 W/m2/ppbv was obtained for CH3Br 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 C02, on a per molecule basis. The radiative forcing calculation is used to estimate the global warming potential (GWP) of CH3Br. The results give GWPs for CH3Br of the order of 13 for an integration period of 20 years and 4 for an integration period of 100 years (assuming C02 = 1, following IPCC [1994]). While CH3Br has a GWP which is approximately 25 percent of the GWP of CH4, the current emission rates are too low to cause serious atmospheric greenhouse heating effects at this time

  6. On the radiative forcing of volcanic plumes: modelling the impact of Mount Etna in the Mediterranean

    Directory of Open Access Journals (Sweden)

    Pasquale Sellitto

    2015-12-01

    Full Text Available The impact of small to moderate volcanic eruptions on the regional to global radiative forcing and climate is still largely unknown and thought to be presently underestimated. In this work, daily average shortwave radiative forcing efficiencies at the surface (RFEdSurf, at top of the atmosphere (RFEdTOA and their ratio (f, for upper tropospheric volcanic plumes with different optical characterization, are derived using the radiative transfer model UVSPEC and the LibRadtran suite. The optical parameters of the simulated aerosol layer, i.e., the Ångströem coefficient (alpha, the single scattering albedo (SSA and the asymmetry factor (g, have been varied to mimic volcanic ash (bigger and more absorbing particles, sulphate aerosols (smaller and more reflective particles and intermediate/mixed conditions. The characterization of the plume and its vertical distribution have been set-up to simulate Mount Etna, basing on previous studies. The radiative forcing and in particular the f ratio is strongly affected by the SSA and g, and to a smaller extent by alpha, especially for sulphates-dominated plumes. The impact of the altitude and thickness of the plume on the radiative forcing, for a fixed optical characterization of the aerosol layer, has been found negligible (less than 1% for RFEdSurf, RFEdTOA and f. The simultaneous presence of boundary layer/lower tropospheric marine or dust aerosols, like expected in the Mediterranean area, modulates only slightly (up to 12 and 14% for RFEdSurf and RFEdTOA, and 3 to 4% of the f ratio the radiative effects of the upper tropospheric volcanic layer.

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

    Science.gov (United States)

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

    2014-12-01

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

  8. Effective aerosol optical depth from pyranometer measurements of surface solar radiation (global radiation at Thessaloniki, Greece

    Directory of Open Access Journals (Sweden)

    A. V. Lindfors

    2013-04-01

    Full Text Available Pyranometer measurements of the solar surface radiation (SSR are available at many locations worldwide, often as long time series covering several decades into the past. These data constitute a potential source of information on the atmospheric aerosol load. Here, we present a method for estimating the aerosol optical depth (AOD using pyranometer measurements of the SSR together with total water vapor column information. The method, which is based on radiative transfer simulations, was developed and tested using recent data from Thessaloniki, Greece. The effective AOD calculated using this method was found to agree well with co-located AERONET measurements, exhibiting a correlation coefficient of 0.9 with 2/3 of the data found within ±20% or ±0.05 of the AERONET AOD. This is similar to the performance of current satellite aerosol methods. Differences in the AOD as compared to AERONET can be explained by variations in the aerosol properties of the atmosphere that are not accounted for in the idealized settings used in the radiative transfer simulations, such as variations in the single scattering albedo and Ångström exponent. Furthermore, the method is sensitive to calibration offsets between the radiative transfer simulations and the pyranometer SSR. The method provides an opportunity of extending our knowledge of the atmospheric aerosol load to locations and times not covered by dedicated aerosol measurements.

  9. Effective aerosol optical depth from pyranometer measurements of surface solar radiation (global radiation at Thessaloniki, Greece

    Directory of Open Access Journals (Sweden)

    A. V. Lindfors

    2012-12-01

    Full Text Available Pyranometer measurements of the solar surface radiation (SSR are available at many locations worldwide, often as long time series covering several decades into the past. These data constitute a potential source of information on the atmospheric aerosol load. Here, we present a method for estimating the aerosol optical depth (AOD using pyranometer measurements of the SSR together with total water vapor column information. The method, which is based on radiative transfer simulations, was developed and tested using recent data from Thessaloniki, Greece. The effective AOD calculated using this method was found to agree well with co-located AERONET measurements, exhibiting a correlation coefficient of 0.9 with 2/3 of the data found within ±20% or ±0.05 of the AERONET AOD. This is similar to the performance of current satellite aerosol methods. Differences in the AOD as compared to AERONET can be explained by variations in the aerosol properties of the atmosphere that are not accounted for in the idealized settings used in the radiative transfer simulations, such as variations in the single scattering albedo and Ångström exponent. Furthermore, the method is sensitive to calibration offsets between the radiative transfer simulations and the pyranometer SSR. The method provides an opportunity of extending our knowledge of the atmospheric aerosol load to locations and times not covered by dedicated aerosol measurements.

  10. Interactive Soil Dust Aerosol Model in the GISS GCM. Part 1; Sensitivity of the Soil Dust Cycle to Radiative Properties of Soil Dust Aerosols

    Science.gov (United States)

    Perlwitz, Jan; Tegen, Ina; Miller, Ron L.

    2000-01-01

    The sensitivity of the soil dust aerosol cycle to the radiative forcing by soil dust aerosols is studied. Four experiments with the NASA/GISS atmospheric general circulation model, which includes a soil dust aerosol model, are compared, all using a prescribed climatological sea surface temperature as lower boundary condition. In one experiment, dust is included as dynamic tracer only (without interacting with radiation), whereas dust interacts with radiation in the other simulations. Although the single scattering albedo of dust particles is prescribed to be globally uniform in the experiments with radiatively active dust, a different single scattering albedo is used in those experiments to estimate whether regional variations in dust optical properties, corresponding to variations in mineralogical composition among different source regions, are important for the soil dust cycle and the climate state. On a global scale, the radiative forcing by dust generally causes a reduction in the atmospheric dust load corresponding to a decreased dust source flux. That is, there is a negative feedback in the climate system due to the radiative effect of dust. The dust source flux and its changes were analyzed in more detail for the main dust source regions. This analysis shows that the reduction varies both with the season and with the single scattering albedo of the dust particles. By examining the correlation with the surface wind, it was found that the dust emission from the Saharan/Sahelian source region and from the Arabian peninsula, along with the sensitivity of the emission to the single scattering albedo of dust particles, are related to large scale circulation patterns, in particular to the trade winds during Northern Hemisphere winter and to the Indian monsoon circulation during summer. In the other regions, such relations to the large scale circulation were not found. There, the dependence of dust deflation to radiative forcing by dust particles is probably

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

    Energy Technology Data Exchange (ETDEWEB)

    Rosenfeld, Daniel [Hebrew Univ. of Jerusalem (Israel)

    2015-12-23

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

  12. Radiative forcing from particle emissions by future supersonic aircraft

    Directory of Open Access Journals (Sweden)

    G. Pitari

    2008-03-01

    Full Text Available In this work we focus on the direct radiative forcing (RF of black carbon (BC and sulphuric acid particles emitted by future supersonic aircraft, as well as on the ozone RF due to changes produced by emissions of both gas species (NOx, H2O and aerosol particles capable of affecting stratospheric ozone chemistry. Heterogeneous chemical reactions on the surface of sulphuric acid stratospheric particles (SSA-SAD are the main link between ozone chemistry and supersonic aircraft emissions of sulphur precursors (SO2 and particles (H2O-H2SO4. Photochemical O3 changes are compared from four independent 3-D atmosphere-chemistry models (ACMs, using as input the perturbation of SSA-SAD calculated in the University of L'Aquila model, which includes on-line a microphysics code for aerosol formation and growth. The ACMs in this study use aircraft emission scenarios for the year 2050 developed by AIRBUS as a part of the EU project SCENIC, assessing options for fleet size, engine technology (NOx emission index, Mach number, range and cruising altitude. From our baseline modelling simulation, the impact of supersonic aircraft on sulphuric acid aerosol and BC mass burdens is 53 and 1.5 μg/m2, respectively, with a direct RF of −11.4 and 4.6 mW/m2 (net RF=−6.8 mW/m2. This paper discusses the similarities and differences amongst the participating models in terms of O3 precursors changes due to aircraft emissions (NOx, HOx,Clx,Brx and stratospheric ozone sensitivity to them. In the baseline case, the calculated global ozone change is −0.4±0.3 DU, with a net radiative forcing (IR+UV of −2.5±2 mW/m2. The fraction of this O3-RF attributable to SSA-SAD changes is, however, highly variable among the models, depending on the NOx removal efficiency from

  13. Radiative forcing from particle emissions by future supersonic aircraft

    Directory of Open Access Journals (Sweden)

    G. Pitari

    2008-07-01

    Full Text Available In this work we focus on the direct radiative forcing (RF of black carbon (BC and sulphuric acid particles emitted by future supersonic aircraft, as well as on the ozone RF due to changes produced by emissions of both gas species (NOx, H2O and aerosol particles capable of affecting stratospheric ozone chemistry. Heterogeneous chemical reactions on the surface of sulphuric acid stratospheric particles (SSA-SAD are the main link between ozone chemistry and supersonic aircraft emissions of sulphur precursors (SO2 and particles (H2O–H2SO4. Photochemical O3 changes are compared from four independent 3-D atmosphere-chemistry models (ACMs, using as input the perturbation of SSA-SAD calculated in the University of L'Aquila model, which includes on-line a microphysics code for aerosol formation and growth. The ACMs in this study use aircraft emission scenarios for the year 2050 developed by AIRBUS as a part of the EU project SCENIC, assessing options for fleet size, engine technology (NOx emission index, Mach number, range and cruising altitude. From our baseline modeling simulation, the impact of supersonic aircraft on sulphuric acid aerosol and BC mass burdens is 53 and 1.5 μg/m2, respectively, with a direct RF of −11.4 and 4.6 mW/m2 (net RF=−6.8 mW/m2. This paper discusses the similarities and differences amongst the participating models in terms of changes to O3 precursors due to aircraft emissions (NOx, HOx,Clx,Brx and the stratospheric ozone sensitivity to them. In the baseline case, the calculated global ozone change is −0.4 ±0.3 DU, with a net radiative forcing (IR+UV of −2.5± 2 mW/m2. The fraction of this O3-RF attributable to SSA-SAD changes is, however, highly variable among the models, depending on the NOx removal

  14. Pharmaceutical aerosols. Study of their gamma radiation sterilization

    International Nuclear Information System (INIS)

    The gamma radiation sterilization of pharmaceutical aerosols was studied. The following topics were investigated: radiosterilization of nitrogen protoxide used as a propellant; radiosterilization of packaging materials (aluminium containers, plastics valves); radio-sterilization of excipients and active ingredients. Most of the investigated materials proved to be stable to irradiation (2,5 Mrads) from pharmacopoeial aspect. Stability tests of the preparations packaged showed no change in the parameters investigated

  15. Global Aerosol Direct Radiative Effect from CALIOP and C3M

    OpenAIRE

    Winker Dave; Kato Seiji; Tackett Jason

    2016-01-01

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

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

    Science.gov (United States)

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

    2016-05-01

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

  17. Radiation doses from contaminant aerosol deposition to the human body

    International Nuclear Information System (INIS)

    Nearly all assessments of radiation doses received following accidental airborne releases have focused on the contributions originating from the plume and from ground deposition. Very little thought has however been given to doses received from deposition directly onto humans. The results of recent experimental investigations of aerosol deposition to and clearance from human skin and clothing have been used to model the doses potentially received in an accident situation. It was found that both the skin dose from β-emitters and the whole body dose from γ-emitters may be significant compared with doses received through other pathways, such as external radiation from the environment. (au)

  18. Estimation of mineral dust longwave radiative forcing: sensitivity study to particle properties and application to real cases over Barcelona

    Directory of Open Access Journals (Sweden)

    M. Sicard

    2014-03-01

    Full Text Available The aerosol radiative effect in the longwave (LW spectral range is sometimes not taken into account in atmospheric aerosol forcing studies at local scale because the LW aerosol effect is assumed to be negligible. At regional and global scale this effect is partially taken into account: aerosol absorption is taken into account but scattering is still neglected. However, aerosols with strong absorbing and scattering properties in the LW region, like mineral dust, can have a non-negligible radiative effect in the LW spectral range (both at surface and top of the atmosphere which can counteract their cooling effect occurring in the shortwave spectral range. The first objective of this research is to perform a sensitivity study of mineral dust LW radiative forcing (RF as a function of dust microphysical and optical properties using an accurate radiative transfer model which can compute vertically-resolved shortwave and longwave aerosol RF. Radiative forcing simulations in the LW range have shown an important sensitivity to the following parameters: aerosol load, radius of the coarse mode, refractive index, aerosol vertical distribution, surface temperature and surface albedo. The scattering effect has been estimated to contribute to the LW RF up to 18% at the surface and up to 38% at the top of the atmosphere. The second objective is the estimation of the shortwave and longwave dust RF for 11 dust outbreaks observed in Barcelona. At the surface, the LW RF varies between +2.8 and +10.2 W m−2, which represents between 11 and 26% (with opposite sign of the SW component, while at the top of the atmosphere the LW RF varies between +0.6 and +5.8 W m−2, which represents between 6 and 26% (with opposite sign of the SW component.

  19. Global Aerosol Direct Radiative Effect from CALIOP and C3M

    Science.gov (United States)

    Winker, Dave; Kato, Seiji; Tackett, Jason

    2016-06-01

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

  20. Reduction of photosynthetically active radiation under extreme stratospheric aerosol loads

    International Nuclear Information System (INIS)

    The recently published hypothesis that the Cretaceous-Tertiary extinctions might be caused by an obstruction of sunlight is tested by model calculations. First we compute the total mass of stratospheric aerosols under normal atmospheric conditions for four different (measured) aerosol size distributions and vertical profiles. For comparison, the stratospheric dust masses after four volcanic eruptions are also evaluated. Detailed solar radiative transfer calculations are then performed for artificially increased aerosol amounts until the postulated darkness scenario is obtained. Thus we find that a total stratospheric aerosol mass between 1 and 4 times 101 g is sufficient to reduce photosynthesis to 10-3 of normal. We also infer from this result tha the impact of a 0.4- to 3-km-diameter asteroid or a close encounter with a Halley-size comet may deposit that amount of particulates into the stratosphere. The darkness scenario of Alvarez et al. is thus shown to be a possible extinction mechanism, even with smaller size asteroids of comets than previously estimated

  1. Aerosol optical and radiative properties observed at Anmyeon and Jeju, Korea in the spring of 2000 and 2001.

    Science.gov (United States)

    Oh, Sung-Nam; Sohn, Byung-Ju; Lee, Sang-Sam

    2004-03-01

    The radiative properties of atmospheric aerosols are determined by their masses, chemical characteristics, and optical properties, such as aerosol optical depth (AOD), Angström parameter (alpha) and single scattering albedo (SSA). In particular, the aerosol optical properties determine the surface temperature perturbation that may give some information in understanding regional atmospheric radiative forcing. To understand the radiative forcing and regional source of an aerosol, the present study focused on the analysis of the aerosol optical properties based on two different observations in the spring season, during the special Asian dust storm period. The Korean Global Atmosphere Watch Observatory (KGAWO), at Anmyeon Island, and the ACE-Asia super-site, at Gosan, Jeju Island, have measured radiations and aerosols since 2000. The sites are located in the mid-west and south of the Korean peninsula, which are strongly affected by the Asian dust coming from China every spring. The aerosol optical properties, measured by ground-based sun and sky radiometers, over both sites were analyzed to gain an understanding of the radiation and climate properties. The probability distributions of the aerosol optical depths were rather narrow, with a modal value of approximately 0.38 at both sites during 2001 and 2002. The Angström parameter frequency distributions showed two peaks at Anmyeon GAW, but only one peak at the Jeju ACE-Asia super site. One peak, around 0.63, characterizes the situation of a day having Asian dust, the second peak, around 1.13, corresponded to the relatively dust-free cases. The correlation between the aerosol optical depth and the Angström exponents resulted in a wide range of the Angström parameter, alpha, over a wide range of optical depths at Anmyeon, whereas a narrow range of alpha, with moderate to low values for the AOD at Jeju. Under dust free conditions the single scattering albedo (SSA) decreased with wavelength, while in the presence of

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

    OpenAIRE

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

    2007-01-01

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

  3. Sensitivity of modelled sulfate radiative forcing to DMS concentration and air-sea flux formulation

    OpenAIRE

    Tesdal, J.-E.; Christian, J.R; Monahan, A.H.; Von Salzen, K.

    2015-01-01

    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 radiative forcing is approximately linearly proportional to the global mean surface flux of DMS; the spatial and temporal dis...

  4. Material fabrication using acoustic radiation forces

    Science.gov (United States)

    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.

  5. Radiative Properties of Smoke and Aerosol Over Land Surfaces

    Science.gov (United States)

    King, Michael D.

    2000-01-01

    This talk discusses smoke and aerosol's radiative properties with particular attention to distinguishing the measurement over clear sky from clouds over land, sea, snow, etc. surfaces, using MODIS Airborne Simulator data from (Brazil, arctic sea ice and tundra and southern Africa, west Africa, and other ecosystems. This talk also discusses the surface bidirectional reflectance using Cloud Absorption Radiometer, BRDF measurements of Saudi Arabian desert, Persian Gulf, cerrado and rain forests in Brazil, sea ice, tundra, Atlantic Ocean, Great Dismal Swamp, Kuwait oil fire smoke. Recent upgrades to instrument (new TOMS UVA channels at 340 and 380 planned use in Africa (SAFARI 2000) and possibly for MEIDEX will also be discussed. This talk also plans to discuss the spectral variation of surface reflectance over land and the sensitivity of off-nadir view angles to correlation between visible near-infrared reflectance for use in remote sensing of aerosol over land.

  6. Assessment of Aerosol Radiative Impact over Oceanic Regions Adjacent to Indian Subcontinent using Multi-Satellite Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Satheesh, S. K.; Vinoj, V.; Krishnamoorthy, K.

    2010-10-01

    Using data from Ozone Monitoring Instrument (OMI) and Moderate Resolution Imaging Spectroradiometer (MODIS) instruments, we have retrieved regional distribution of aerosol column single scattering albedo (parameter indicative of the relative dominance of aerosol absorption and scattering effects), a most important, but least understood aerosol property in assessing its climate impact. Consequently we provide improved assessment of short wave aerosol radiative forcing (ARF) (on both regional and seasonal scales) estimates over this region. Large gradients in north-south ARF were observed as a consequence of gradients in single scattering albedo as well as aerosol optical depth. The highest ARF (-37 W m-2 at the surface) was observed over the northern Arabian Sea during June to August period (JJA). In general, ARF was higher over northern Bay of Bengal (NBoB) during winter and pre-monsoon period, whereas the ARF was higher over northern Arabian Sea (NAS) during the monsoon and post- monsoon period. The largest forcing observed over NAS during JJA is the consequence of large amounts of desert dust transported from the west Asian dust sources. High as well as seasonally invariant aerosol single scattering albedos (~0.98) were observed over the southern Indian Ocean region far from continents. The ARF estimates based on direct measurements made at a remote island location, Minicoy (8.3°N, 73°E) in the southern Arabian Sea are in good agreement with the estimates made following multisatellite analysis.

  7. Smoke aerosol and its radiative effects during extreme fire event over Central Russia in summer 2010

    Directory of Open Access Journals (Sweden)

    N. Chubarova

    2012-03-01

    Full Text Available Different microphysical, optical and radiative properties of aerosol were analyzed during the severe fires in summer 2010 over Central Russia using ground measurements at two AERONET sites in Moscow (Meteorological Observatory of Moscow State University – MSU MO and Zvenigorod (Moscow Region and radiative measurements at the MSU MO. Volume aerosol size distribution in smoke conditions had a bimodal character with the significant prevalence of fine mode particles, for which effective radius was shifted to higher values (reff-fine = 0.24 μm against approximately 0.15 μm in typical conditions. For smoke aerosol, the imaginary part of refractive index (REFI in the visible spectral region was lower than that for typical aerosol (REFIλ =675 nm = 0.006 against REFIλ =675 nm = 0.01, while single scattering albedo (SSA was significantly higher (SSAλ =675 nm = 0.95 against SSAλ =675 nm ~ 0.9. Extremely high aerosol optical thickness at 500 nm (AOT500 was observed on 6–8 August reaching the absolute maximum on 7 August in Moscow (AOT500 = 6.4 and at Zvenigorod (AOT500 = 5.9. A dramatic attenuation of solar irradiance at ground was also recorded. Maximum irradiance loss had reached 64% for global shortwave irradiance, 91% for UV radiation 300–380 nm, and 97% for erythemally-weighted UV irradiance at relatively high solar elevation 47°. Significant spectral dependence in attenuation of solar irradiance in smoky conditions was mainly explained by higher AOT and smaller SSA in UV (0.8–0.9 compared with SSA in the visible region of spectrum. The assessments of radiative forcing effect (RFE at the TOA indicated a significant cooling of the smoky atmosphere. Instant RFE reached −167 Wm−2 at AOT500 = 6.4, climatological RFE calculated with August 2010 monthly mean AOT was about −65 Wm−2, compared with −20 Wm−2 for typical aerosol according to

  8. Retrieval of aerosol optical depth from surface solar radiation measurements using machine learning algorithms, non-linear regression and a radiative transfer-based look-up table

    Science.gov (United States)

    Huttunen, Jani; Kokkola, Harri; Mielonen, Tero; Esa Juhani Mononen, Mika; Lipponen, Antti; Reunanen, Juha; Vilhelm Lindfors, Anders; Mikkonen, Santtu; Erkki Juhani Lehtinen, Kari; Kouremeti, Natalia; Bais, Alkiviadis; Niska, Harri; Arola, Antti

    2016-07-01

    In order to have a good estimate of the current forcing by anthropogenic aerosols, knowledge on past aerosol levels is needed. Aerosol optical depth (AOD) is a good measure for aerosol loading. However, dedicated measurements of AOD are only available from the 1990s onward. One option to lengthen the AOD time series beyond the 1990s is to retrieve AOD from surface solar radiation (SSR) measurements taken with pyranometers. In this work, we have evaluated several inversion methods designed for this task. We compared a look-up table method based on radiative transfer modelling, a non-linear regression method and four machine learning methods (Gaussian process, neural network, random forest and support vector machine) with AOD observations carried out with a sun photometer at an Aerosol Robotic Network (AERONET) site in Thessaloniki, Greece. Our results show that most of the machine learning methods produce AOD estimates comparable to the look-up table and non-linear regression methods. All of the applied methods produced AOD values that corresponded well to the AERONET observations with the lowest correlation coefficient value being 0.87 for the random forest method. While many of the methods tended to slightly overestimate low AODs and underestimate high AODs, neural network and support vector machine showed overall better correspondence for the whole AOD range. The differences in producing both ends of the AOD range seem to be caused by differences in the aerosol composition. High AODs were in most cases those with high water vapour content which might affect the aerosol single scattering albedo (SSA) through uptake of water into aerosols. Our study indicates that machine learning methods benefit from the fact that they do not constrain the aerosol SSA in the retrieval, whereas the LUT method assumes a constant value for it. This would also mean that machine learning methods could have potential in reproducing AOD from SSR even though SSA would have changed during

  9. The tropospheric aerosol at mid-latitudes - microphysics, optics, and climate forcing illustrated by the LACE 98 field study; Das troposphaerische Aerosol in mittleren Breiten - Mikrophysik, Optik und Klimaantrieb am Beispiel der Feldstudie LACE 98

    Energy Technology Data Exchange (ETDEWEB)

    Fiebig, M.

    2001-07-01

    This study investigates the column closure of optical aerosol parameters as part of the Lindenberg Aerosol Characterisation Experiment (LACE 98). The optical aerosol parameters were calculated from microphysical aerosol parameters which were measured height resolved from tropopause to boundary layer and compared with the direct measurement of the respective property (closure). The closure allows the validation of the measured aerosol properties and the inversion of aerosol properties which are not measurable directly. The radiative forcings of the measured aerosol columns are estimated. The measured, quality assured microphysical aerosol properties are parameterized and tabulated as input data for models. The successful closure of the aerosol column's optical depth validates the measured particle size distributions, whereas the successful closure of the backscatter coefficient validates the assumptions made on the aerosol chemical composition and serves to deduce its state of mixture, the latter point exemplified using a 7 day old forest fire aerosol. The local, instantaneous radiative forcing of the measured continental particle columns are estimated to lie between -33 W/m{sup 2} for continental and -6 W/m{sup 2} for marine air masses for a solar zenith angle of 56 . (orig.) [German] Als Teil des Lindenberger Aerosol Charakterisierungsexperimentes (LACE 98) behandelt diese Arbeit die Saeulenschliessung optischer Aerosolparameter. Diese wurden aus den von Tropopause bis Grenzschicht hoehenaufgeloest gemessenen mikrophysikalischen Aerosoleigenschaften berechnet, um sie mit den am gleichen Ort direkt gemessenen optischen Aerosolparametern zu vergleichen (Schliessung). Es wird gezeigt, dass die Schliessung die Qualitaetssicherung der gemessenen Aerosoleigenschaften und die Invertierung direkt nicht messbarer Aerosoleigenschaften ermoeglicht. Die Strahlungsantriebe der vermessenen Aerosolsaeulen werden abgeschaetzt. Die qualitaetsgesicherten gemessenen

  10. New approaches to quantifying aerosol influence on the cloud radiative effect

    Science.gov (United States)

    Feingold, Graham; McComiskey, Allison; Yamaguchi, Takanobu; Johnson, Jill S.; Carslaw, Kenneth S.; Schmidt, K. Sebastian

    2016-05-01

    The topic of cloud radiative forcing associated with the atmospheric aerosol has been the focus of intense scrutiny for decades. The enormity of the problem is reflected in the need to understand aspects such as aerosol composition, optical properties, cloud condensation, and ice nucleation potential, along with the global distribution of these properties, controlled by emissions, transport, transformation, and sinks. Equally daunting is that clouds themselves are complex, turbulent, microphysical entities and, by their very nature, ephemeral and hard to predict. Atmospheric general circulation models represent aerosol‑cloud interactions at ever-increasing levels of detail, but these models lack the resolution to represent clouds and aerosol‑cloud interactions adequately. There is a dearth of observational constraints on aerosol‑cloud interactions. We develop a conceptual approach to systematically constrain the aerosol‑cloud radiative effect in shallow clouds through a combination of routine process modeling and satellite and surface-based shortwave radiation measurements. We heed the call to merge Darwinian and Newtonian strategies by balancing microphysical detail with scaling and emergent properties of the aerosol‑cloud radiation system.

  11. Remote Sensing of Aerosol and their Radiative Properties from the MODIS Instrument on EOS-Terra Satellite: First Results and Evaluation

    Science.gov (United States)

    Kaufman, Yoram; Tanre, Didier; Remer, Lorraine; Holben, Brent; Lau, William K.-M. (Technical Monitor)

    2001-01-01

    The MODIS instrument was launched on the NASA Terra satellite in Dec. 1999. Since last Oct., the sensor and the aerosol algorithm reached maturity and provide global daily retrievals of aerosol optical thickness and properties. MODIS has 36 spectral channels in the visible to IR with resolution down to 250 m. This allows accurate cloud screening and multi-spectral aerosol retrievals. We derive the aerosol optical thickness over the ocean and most of the land areas, distinguishing between fine (mainly man-made aerosol) and coarse aerosol particles. The information is more precise over the ocean where we derive also the effective radius and scattering asymmetry parameter of the aerosol. New methods to derive the aerosol single scattering albedo are also being developed. These measurements are use to track different aerosol sources, transport and the radiative forcing at the top and bottom of the atmosphere. The AErosol RObotic NETwork of ground based radiometers is used for global validation of the satellite derived optical thickness, size parameters and single scattering albedo and measure additional aerosol parameters that cannot be derived from space.

  12. Regional radiative impact of volcanic aerosol from the 2009 eruption of Redoubt volcano

    Directory of Open Access Journals (Sweden)

    C. L. Young

    2011-09-01

    Full Text Available High northern latitude eruptions have the potential to release volcanic aerosol into the Arctic environment, perturbing the Arctic's climate system. In this study, we present assessments of shortwave (SW, longwave (LW and net direct aerosol radiative forcings (DARFs and atmospheric heating/cooling rates caused by volcanic aerosol from the 2009 eruption of Redoubt Volcano by performing radiative transfer modeling constrained by NASA A-Train satellite data. The Ozone Monitoring Instrument (OMI, the Moderate Resolution Imaging Spectroradiometer (MODIS, and the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT model for volcanic ash were used to characterize aerosol across the region. A representative range of aerosol optical depths (AODs at 550 nm were obtained from MODIS, and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO was used to determine the altitude and thickness of the plumes. The optical properties of volcanic aerosol were calculated using a compositionally resolved microphysical model developed for both ash and sulfates. Two compositions of volcanic aerosol were considered in order to examine a fresh, ash rich plume and an older, ash poor plume. Optical models were incorporated into a modified version of the Santa Barbara Disort Atmospheric Radiative Transfer (SBDART model. Radiative transfer calculations were made for a range of surface albedos and solar zenith angles (SZA representative of the region. We find that the total DARF caused by a fresh, thin plume (~2.5–7 km at an AOD (550 nm range of 0.16–0.58 and SZA = 55° is –46 W m−2AOD−1 at the top of the atmosphere (TOA, 110 W m−2AOD−1 in the aerosol layer, and – 150 W m−2AOD−1 at the surface over seawater. However, the total DARF for the same plume over snow and at the same SZA at TOA, in the layer, and at the surface is 170, 170, and −2 W m−2

  13. The radiative forcing potential of different climate geoengineering options

    Directory of Open Access Journals (Sweden)

    T. M. Lenton

    2009-08-01

    Full Text Available Climate geoengineering proposals seek to rectify the Earth's current and potential future radiative imbalance, either by reducing the absorption of incoming solar (shortwave radiation, or by removing CO2 from the atmosphere and transferring it to long-lived reservoirs, thus increasing outgoing longwave radiation. A fundamental criterion for evaluating geoengineering options is their climate cooling effectiveness, which we quantify here in terms of radiative forcing potential. We use a simple analytical approach, based on energy balance considerations and pulse response functions for the decay of CO2 perturbations. This aids transparency compared to calculations with complex numerical models, but is not intended to be definitive. It allows us to compare the relative effectiveness of a range of proposals. We consider geoengineering options as additional to large reductions in CO2 emissions. By 2050, some land carbon cycle geoengineering options could be of comparable magnitude to mitigation "wedges", but only stratospheric aerosol injections, albedo enhancement of marine stratocumulus clouds, or sunshades in space have the potential to cool the climate back toward its pre-industrial state. Strong mitigation, combined with global-scale air capture and storage, afforestation, and bio-char production, i.e. enhanced CO2 sinks, might be able to bring CO2 back to its pre-industrial level by 2100, thus removing the need for other geoengineering. Alternatively, strong mitigation stabilising CO2 at 500 ppm, combined with geoengineered increases in the albedo of marine stratiform clouds, grasslands, croplands and human settlements might achieve a patchy cancellation of radiative forcing. Ocean fertilisation options are only worthwhile if sustained on a millennial timescale and phosphorus addition may have greater long-term potential than iron or nitrogen fertilisation. Enhancing ocean

  14. Radiative effects of aerosols at an urban location in southern India: Observations versus model

    Science.gov (United States)

    Satheesh, S. K.; Vinoj, V.; Krishna Moorthy, K.

    2010-12-01

    The radiative impact of aerosols is one of the largest sources of uncertainty in estimating anthropogenic climate perturbations. Here we have used independent ground-based radiometer measurements made simultaneously with comprehensive measurements of aerosol microphysical and optical properties at a highly populated urban site, Bangalore (13.02°N, 77.6°E) in southern India during a dedicated campaign during winter of 2004 and summer and pre-monsoon season of 2005. We have also used longer term measurements carried out at this site to present general features of aerosols over this region. The aerosol radiative impact assessments were made from direct measurements of ground reaching irradiance as well as by incorporating measured aerosol properties into a radiative transfer model. Large discrepancies were observed between measured and modeled (using radiative transfer models, which employed measured aerosol properties) radiative impacts. It appears that the presence of elevated aerosol layers and (or) inappropriate description of aerosol state of mixing are (is) responsible for the discrepancies. On a monthly scale reduction of surface irradiance due to the presence of aerosols (estimated using radiative flux measurements) varies from 30 to 65 W m -2. The lowest values in surface radiative impact were observed during June when there is large reduction in aerosol as a consequence of monsoon rainfall. Large increase in aerosol-induced surface radiative impact was observed from winter to summer. Our investigations re-iterate the inadequacy of aerosol measurements at the surface alone and importance of representing column properties (using vertical profiles) accurately in order to assess aerosol-induced climate changes accurately.

  15. Radiative budget in the presence of multi-layered aerosol structures in the framework of AMMA SOP-0

    Directory of Open Access Journals (Sweden)

    J.-C. Raut

    2008-11-01

    Full Text Available This paper presents radiative transfer calculations performed over Niamey in the UV-Visible range over the period 26th January–1st February 2006 during the African Multidisciplinary Monsoon Analysis (AMMA international program. Climatic effects of aerosols along the vertical column have required an accurate determination of their optical properties, which are presented here for a variety of instrumented platforms: Ultralight aircraft, Facility for Airborne Atmospheric Measurements (FAAM research aircraft, AERONET station. Measurements highlighted the presence of a multi-layered structure of mineral dust located below and biomass-burning particles in the more elevated layers. Radiative forcing was affected by both the scattering and absorption effects governed by the aerosol complex refractive index (ACRI. The best agreement between our results and AERONET optical thicknesses, ground-based extinction measurements and NO2 photolysis rate coefficient was found using the synergy between all the instrumented platforms. The corresponding averaged ACRI at 355 nm were 1.53 (±0.04 −0.047i (±0.006 and 1.52 (±0.04 −0.008i (±0.001 for biomass-burning and mineral dust aerosols, respectively. Biomass-burning aerosols were characterized by single-scattering albedo ranging from 0.78 to 0.82 and asymmetry parameter ranging from 0.71 to 0.73. For dust aerosols, single-scattering albedo (asymmetry parameter ranged from 0.9 to 0.92 (0.73 to 0.75. The solar energy depletion at the surface is shown to be ~−21.2 (±1.7 W/m2 as a daily average. At the TOA, the radiative forcing appeared slightly negative but very close to zero (~−1.4 W/m2. The corresponding atmospheric radiative forcing was found to be ~19.8 (±2.3 W/m2. Mineral dust located below a more absorbing layer act as an increase in surface reflectivity of ~3–4%. The radiative forcing is also shown to be highly sensitive to the optical features of the

  16. Radiative budget in the presence of multi-layered aerosol structures in the framework of AMMA SOP-0

    Directory of Open Access Journals (Sweden)

    J.-C. Raut

    2008-07-01

    Full Text Available This paper presents radiative transfer calculations performed over Niamey in the UV-Visible range over the period 26th January – 1st February during the African Multidisciplinary Monsoon Analysis (AMMA international program. Climatic effects of aerosols along the vertical column have required an accurate determination of their optical properties, which are presented in for a variety of instrumented platforms: Ultralight aircraft, Facility for Airborne Atmospheric Measurements (FAAM research aircraft, AERONET station. Measurements highlighted the presence of a multi-layered structure of mineral dust located below and biomass-burning particles in the more elevated layers. Radiative forcing was affected by both the scattering and absorption effects governed by the aerosol complex refractive index (ACRI. The best agreement between our results and AERONET optical thicknesses, ground-based extinction measurements and NO2 photolysis rate coefficient was found using the synergy between all the instrumented platforms. The corresponding averaged ACRI were 1.53 (±0.04–0.047i (±0.006 and 1.52 (±0.04–0.008i (±0.001 for biomass-burning and mineral dust aerosols, respectively. Biomass-burning aerosols were characterized by single-scattering albedo ranging from 0.78 to 0.82 and asymmetry parameter ranging from 0.71 to 0.73. For dust aerosols, single-scattering albedo (asymmetry parameter ranged from 0.9 to 0.92 (0.73 to 0.75. The solar energy depletion at the surface is shown to be ~ −21.2 (±1.7 W/m2 as a daily average. At the TOA, the radiative forcing appeared slightly negative but very close to zero (~ −1.4 W/m2. The corresponding atmospheric radiative forcing was found to be ~19.8 (±2.3 W/m2. Mineral dust located below a more absorbing layer act as an increase in surface reflectivity of ~3–4%. The radiative forcing is also shown to be highly sensitivity the optical features of the different

  17. Acoustic radiation force impulse of the liver.

    Science.gov (United States)

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

    2013-08-14

    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

  18. Acoustic radiation force impulse of the liver

    Science.gov (United States)

    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

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

    Science.gov (United States)

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

    2012-12-01

    While aerosol radiative effects have been recognized as some of the largest sources of uncertainty among the forcers of climate change, there has been little effort devoted to verification of the spatial and temporal variability of the magnitude and directionality of aerosol radiative forcing. A comprehensive investigation of the processes regulating aerosol distributions, their optical properties, and their radiative effects and verification of their simulated effects for past conditions relative to measurements is needed in order to build confidence in the estimates of the projected impacts arising from changes in both anthropogenic forcing and climate change. This study aims at addressing this issue through a systematic investigation of changes in anthropogenic emissions of SO2 and NOx over the past two decades in the United States, their impacts on anthropogenic aerosol loading in the North American troposphere, and subsequent impacts on regional radiation budgets. A newly developed 2-way coupled meteorology and air pollution model composed of the Weather Research and Forecasting (WRF) model and the Community Multiscale Air Quality (CMAQ) model is being run for 20 years (1990 - 2010) on a 12 km resolution grid that covers most of North America including the entire conterminous US. During this period US emissions of SO2 and NOx have been reduced by about 66% and 50%, respectively, mainly due to Title IV of the U.S. Clean Air Act Amendments (CAA) that aimed to reduce emissions that contribute to acid deposition. A methodology is developed to consistently estimate emission inventories for the 20-year period accounting for air quality regulations as well as population trends, economic conditions, and technology changes in motor vehicles and electric power generation. The coupled WRF-CMAQ model includes detailed treatment of direct effects of aerosols on photolysis rates as well as on shortwave radiation and the direct effects of tropospheric ozone on the long

  20. Transthoracic Cardiac Acoustic Radiation Force Impulse Imaging

    Science.gov (United States)

    Bradway, David Pierson

    This dissertation investigates the feasibility of a real-time transthoracic Acoustic Radiation Force Impulse (ARFI) imaging system to measure myocardial function non-invasively in clinical setting. Heart failure is an important cardiovascular disease and contributes to the leading cause of death for developed countries. Patients exhibiting heart failure with a low left ventricular ejection fraction (LVEF) can often be identified by clinicians, but patients with preserved LVEF might be undetected if they do not exhibit other signs and symptoms of heart failure. These cases motivate development of transthoracic ARFI imaging to aid the early diagnosis of the structural and functional heart abnormalities leading to heart failure. M-Mode ARFI imaging utilizes ultrasonic radiation force to displace tissue several micrometers in the direction of wave propagation. Conventional ultrasound tracks the response of the tissue to the force. This measurement is repeated rapidly at a location through the cardiac cycle, measuring timing and relative changes in myocardial stiffness. ARFI imaging was previously shown capable of measuring myocardial properties and function via invasive open-chest and intracardiac approaches. The prototype imaging system described in this dissertation is capable of rapid acquisition, processing, and display of ARFI images and shear wave elasticity imaging (SWEI) movies. Also presented is a rigorous safety analysis, including finite element method (FEM) simulations of tissue heating, hydrophone intensity and mechanical index (MI) measurements, and thermocouple transducer face heating measurements. For the pulse sequences used in later animal and clinical studies, results from the safety analysis indicates that transthoracic ARFI imaging can be safely applied at rates and levels realizable on the prototype ARFI imaging system. Preliminary data are presented from in vivo trials studying changes in myocardial stiffness occurring under normal and abnormal

  1. Regional aerosol optical properties and radiative impact of the extreme smoke event in the European Arctic in spring 2006

    Directory of Open Access Journals (Sweden)

    C. Lund Myhre

    2007-11-01

    Full Text Available In spring 2006 a special meteorological situation occurred in the European Arctic region giving record high levels of air pollution. The synoptic situation resulted in extensive transport of pollution predominantly from agricultural fires in Eastern Europe into the Arctic region and record high air-pollution levels were measured at the Zeppelin observatory at Ny-Ålesund (78°54' N, 11°53' E in the period from 25 April to 12 May. In the present study we investigate the optical properties of the aerosols from this extreme event and we estimate the radiative forcing of this episode.

    We examine the aerosol optical properties from the source region and into the European Arctic and explore the evolution of the episode and the changes in the optical properties. A number of sites in Eastern Europe, Northern Scandinavia and Svalbard are included in the study. The observations show that the maximum AOD was from 2–3 May at all sites and varies from 0.52 to 0.87, and the corresponding Ångstrøm exponent was relatively large. Lidar measurements from Minsk, ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research at Andenes and Ny-Ålesund show that the aerosol layer was below 3 km at all sites the height is decreasing from the source region and into the Arctic. For the AERONET sites included (Minsk, Toravere, Hornsund we have further studied the evolution of the aerosol size. The single scattering albedo at Svalbard is provided for two sites; Ny-Ålesund and Hornsund. Importantly the calculated single scattering albedo based on the aerosol chemical composition and size distribution from Ny-Ålesund and the AERONET measurements at Hornsund are consistent. We have found strong agreement between the satellite daily MODIS AOD and the ground-based AOD observations. This agreement is crucial for accurate radiative forcing calculations. We calculate a strong negative radiative forcing for the most polluted days employing the analysed

  2. A Novel Motion Compensation Algorithm for Acoustic Radiation Force Elastography

    OpenAIRE

    Fahey, Brian J.; Hsu, Stephen J.; Trahey, Gregg E.

    2008-01-01

    A novel method of physiological motion compensation for use with radiation force elasticity imaging has been developed. The method utilizes a priori information from finite element method models of the response of soft tissue to impulsive radiation force to isolate physiological motion artifacts from radiation force-induced displacement fields. The new algorithm is evaluated in a series of clinically realistic imaging scenarios, and its performance is compared to that achieved with previously...

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

    Science.gov (United States)

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

    2016-06-01

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

  4. Regional Aerosol Optical Properties and Radiative Impact of the Extreme Smoke Event in the European Arctic in Spring 2006

    Science.gov (United States)

    Lund Myhre, C.; Toledano, C.; Myhre, G.; Stebel, K.; Yttri, K.; Aaltonen, V.; Johnsrud, M.; Frioud, M.; Cachorro, V.; deFrutos, A.; Lihavainen, H.; Campbell, J.; Chaikovsky, A.; Shiobara, M.; Welton, E.; Torseth, K.

    2007-01-01

    In spring 2006 a special meteorological situation occurred in the European Arctic region giving record high levels of air pollution. The synoptic situation resulted in extensive transport of pollution predominantly from agricultural fires in Eastern Europe into the Arctic region and record high air-pollution levels were measured at the Zeppelin observatory at Ni-Alesun(78deg 54'N, 11deg 53'E) in the period from 25 April to 12 May. In the present study we investigate the optical properties of the aerosols from this extreme event and we estimate the radiative forcing of this episode. We examine the aerosol optical properties from the source region and into the European Arctic and explore the evolution of the episode and the changes in the optical properties. A number of sites in Eastern Europe, Northern Scandinavia and Svalbard are included in the study. In addition to AOD measurements, we explored lidar measurements from Minsk, ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research at Andenes) and Ny-Alesund. For the AERONET sites included (Minsk, Toravere, Hornsund) we have further studied the evolution of the aerosol size. Importantly, at Svalbard it is consistency between the AERONET measurements and calculations of single scattering albedo based on aerosol chemical composition. We have found strong agreement between the satellite dally MODIS AOD and the ground-based AOD observations. This agreement is crucial for the radiative forcing calculations. We calculate a strong negative radiative forcing for the most polluted days employing the analysed ground based data, MODIS AOD and a multi-stream model for radiative transfer of solar radiation.

  5. Regional aerosol optical properties and radiative impact of the extreme smoke event in the European Arctic in spring 2006

    Directory of Open Access Journals (Sweden)

    C. Lund Myhre

    2007-07-01

    Full Text Available In spring 2006 a special meteorological situation occurred in the European Arctic region giving record high levels of air pollution. The synoptic situation resulted in extensive transport of pollution predominantly from agricultural fires in Eastern Europe into the Arctic region and record high air-pollution levels were measured at the Zeppelin observatory at Ny-Ålesund (78°54' N, 11°53' E in the period from 25 April to 12 May. In the present study we investigate the optical properties of the aerosols from this extreme event and we estimate the radiative forcing of this episode.

    We examine the aerosol optical properties from the source region and into the European Arctic and explore the evolution of the episode and the changes in the optical properties. A number of sites in Eastern Europe, Northern Scandinavia and Svalbard are included in the study. In addition to AOD measurements, we explored lidar measurements from Minsk, ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research at Andenes and Ny-Ålesund. For the AERONET sites included (Minsk, Toravere, Hornsund we have further studied the evolution of the aerosol size. Importantly, at Svalbard it is consistency between the AERONET measurements and calculations of single scattering albedo based on aerosol chemical composition. We have found strong agreement between the satellite daily MODIS AOD and the ground-based AOD observations. This agreement is crucial for the radiative forcing calculations. We calculate a strong negative radiative forcing for the most polluted days employing the analysed ground based data, MODIS AOD and a multi-stream model for radiative transfer of solar radiation.

  6. Variability in radiative properties of major aerosol types: a year-long study over Delhi--an urban station in Indo-Gangetic Basin.

    Science.gov (United States)

    Srivastava, A K; Yadav, V; Pathak, V; Singh, Sachchidanand; Tiwari, S; Bisht, D S; Goloub, P

    2014-03-01

    Aerosol measurements over an urban site at Delhi in the western Ganga basin, northern India, were carried out during 2009 using a ground-based automatic sun/sky radiometer to identify their different types and to understand their possible radiative implications. Differentiation of aerosol types over the station was made using the appropriate thresholds for size-distribution of aerosols (i.e. fine-mode fraction, FMF at 500 nm) and radiation absorptivity (i.e. single scattering albedo, SSA at 440 nm). Four different aerosol types were identified, viz., polluted dust (PD), polluted continent (PC), mostly black carbon (MBC) and mostly organic carbon (MOC), which contributed ~48%, 32%, 11% and 9%, respectively to the total aerosols. Interestingly, the optical properties for these aerosol types differed considerably, which were further used, for the first time, to quantify their radiative implications over this station. The highest atmospheric forcing was observed for PC aerosol type (about +40 W m(-2), along with the corresponding atmospheric heating rate of 1.10 K day(-1)); whereas the lowest was for MBC aerosol type (about +25 W m(-2), along with the corresponding atmospheric heating rate of 0.69 K day(-1)). PMID:24412733

  7. The Radiative Role of Free Tropospheric Aerosols and Marine Clouds over the Central North Atlantic

    Energy Technology Data Exchange (ETDEWEB)

    Mazzoleni, Claudio [Michigan Technological University; Kumar, Sumit [Michigan Technological University; Wright, Kendra [Michigan Technological University; Kramer, Louisa [Michigan Technological University; Mazzoleni, Lynn [Michigan Technological University; Owen, Robert [Michigan Technological University; Helmig, Detlev [University of Colorado at Boulder

    2014-12-09

    The scientific scope of the project was to exploit the unique location of the Pico Mountain Observatory (PMO) located in the summit caldera of the Pico Volcano in Pico Island in the Azores, for atmospheric studies. The observatory, located at 2225m a.s.l., typically samples free tropospheric aerosols laying above the marine low-level clouds and long-range transported from North America. The broad purpose of this research was to provide the scientific community with a better understanding of fundamental physical processes governing the effects of aerosols on radiative forcing and climate; with the ultimate goal of improving our abilities to understand past climate and to predict future changes through numerical models. The project was 'exploratory' in nature, with the plan to demonstrate the feasibility of deploying for the first time, an extensive aerosol research package at PMO. One of the primary activities was to test the deployment of these instruments at the site, to collect data during the 2012 summer season, and to further develop the infrastructure and the knowledge for performing novel research at PMO in follow-up longer-term aerosol-cloud studies. In the future, PMO could provide an elevated research outpost to support the renewed DOE effort in the Azores that was intensified in 2013 with the opening of the new sea-level ARM-DOE Eastern North Atlantic permanent facility at Graciosa Island. During the project period, extensive new data sets were collected for the planned 2012 season. Thanks to other synergistic activities and opportunities, data collection was then successfully extended to 2013 and 2014. Highlights of the scientific findings during this project include: a) biomass burning contribute significantly to the aerosol loading in the North Atlantic free troposphere; however, long-range transported black carbon concentrations decreased substantially in the last decade. b) Single black carbon particles – analyzed off-line at the electron

  8. The electric charge of the aerosols under gamma radiation; La charge electrique des aerosols sous irradiation gamma

    Energy Technology Data Exchange (ETDEWEB)

    Gensdarmes, F.; Cetier, P.; Boulaud, D. [CEA/Saclay, Inst. de Protection et de Surete Nucleaire, IPSN/DPEA/SERAC, 91 - Gif-sur-Yvette (France); Renoux, A. [Paris-12 Univ., Lab. de Physique des Aerosols et de Transfert des Contaminations, 94 - Creteil (France)

    2000-07-01

    During a PWR type reactor accident, the gamma radiation may create a high ionized atmosphere. In such a situation the aerosols properties knowledge is useful to simulate the particles transport and deposit in the enclosed. The aim of this study is to determine the aerosol charges distribution in a high ionized medium, in function of the ionic properties of the medium. (A.L.B.)

  9. Impact of the modal aerosol scheme GLOMAP-mode on aerosol forcing in the Hadley Centre Global Environmental Model

    OpenAIRE

    Bellouin, N; Mann, G.W.; Woodhouse, M.T.; Johnson, C.; Carslaw, K. S.; Dalvi, M.

    2012-01-01

    The Hadley Centre Global Environmental Model (HadGEM) includes two aerosol schemes: the Coupled Large-scale Aerosol Simulator for Studies in Climate (CLASSIC), and the new Global Model of Aerosol Processes (GLOMAP-mode). GLOMAP-mode is a modal aerosol microphysics scheme that simulates not only aerosol mass but also aerosol number, represents internally-mixed particles, and includes aerosol microphysical processes such as nucleation. In this study, both schemes provide hindcast simulations of...

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

    Science.gov (United States)

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

    2016-05-01

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

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

    Science.gov (United States)

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

    2016-05-01

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

  12. Radiative forcing and temperature response to changes in urban albedos and associated CO2 offsets

    Energy Technology Data Exchange (ETDEWEB)

    Menon, Surabi; Akbari, Hashem; Mahanama, Sarith; Sednev, Igor; Levinson, Ronnen

    2010-02-12

    The two main forcings that can counteract to some extent the positive forcings from greenhouse gases from pre-industrial times to present-day are the aerosol and related aerosol-cloud forcings, and the radiative response to changes in surface albedo. Here, we quantify the change in radiative forcing 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) radiation 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 radiation 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 radiation 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 forcings, 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.

  13. Multi-fingerprint detection and attribution analysis of greenhouse gas, greenhouse gas-plus-aerosol and solar forced climate change

    Energy Technology Data Exchange (ETDEWEB)

    Hegerl, G.C.; Hasselmann, K.; Cubasch, U.; Roeckner, E.; Voss, R. [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany); Mitchell, J.F.B. [Hadley Centre for Climate Prediction and Research, Bracknell (United Kingdom). Meteorological Office; Waszkewitz, J. [Deutsches Klimarechenzentrum (DKRZ), Hamburg (Germany)

    1997-09-01

    A multifingerprint analysis is applied to the detection and attribution of anthropogenic climate change. While a single fingerprint is optimal for the detection of climate change, further tests of the statistical consistency of the detected climate change signal with model predictions for different candidate forcing mechanisms require the simultaneous application of several fingerprints. Model-predicted climate change signals are derived from three anthropogenic global warming simulations for the period 1880 to 2049and two simulations forced by estimated changes in solar radiation from 1700 to 1992. In the first global warming simulation, the forcing is by greenhouse gas only, while in the remaining two simulations the direct influence of sulfate aerosols is also included. From the climate change signals of the greenhouse gas only and the average of the two greenhouse gas-plus-aerosol simulations, two optimized fingerprint patterns are derived by weighting the model-predicted climate change patterns towards low-noise directions. The optimized fingerprint patterns are then applied as a filter to the observed near-surface temperature trend patterns, yielding several detection variables. The space-time structure of natural climate variability needed to determine the optimal fingerprint pattern and the resultant signal-to-noise ratio of the detection variable is estimated from several multicentury control simulations with different CGCMs and from instrumental data over the last 136 y. Applying the combined greenhouse gas-plus-aerosol fingerprint in the same way as the greenhouse gas only fingerprint in a previous work, the recent 30-y trends (1966-1995) of annual mean near surface temperature are again found to represent a significant climate change at the 97.5% confidence level. (orig.) With 13 figs., 3 tabs., 63 refs.

  14. A critical assessment of direct radiative effects of different aerosol types on surface global radiation and its components

    International Nuclear Information System (INIS)

    A critical assessment of direct radiative effects of different aerosol types on surface global, direct and diffuse radiation is presented. The analysis is based on measurements of aerosol optical properties and surface solar radiation (SSR) of cloud-free days at the Baseline Surface Radiation Network (BSRN) and Aerosol Robotic Network station (AERONET) of Xianghe over the North China Plain between October 2004 and May 2012. Six aerosol types are classified based on aerosol size and absorption from the AERONET retrieval products, including two coarse-mode dominated aerosol types: dust (DU: fine mode fraction (FMF)<0.4) and polluted dust (PD: FMF within 0.4–0.7) and four fine-mode dominated aerosol types (FMF>0.7) but with different single scattering albedo (SSA): highly absorbing (HA: SSA<0.85), moderately absorbing (MA: SSA within 0.85–0.90), slightly absorbing (SA: SSA within 0.90–0.95) and very weakly absorbing (WA: SSA>0.95). Dramatic differences in aerosol direct radiative effect (ADRE) on global SSR and its components between the six aerosol types have been revealed. ADRE efficiency on global SSR for solar zenight angle (SZA) between 55° and 65° ranges from −106 W m−2 for WA to −181 W m−2 for HA. The minimum ADRE efficiency on diffuse SSR is derived for HA aerosols, being 113 W m−2 that is about half of that by DU, the maximum value of six aerosol types. ADRE efficiency on global SSR by DU and PD (−141 to −150 W m−2 for SZA between 55° and 65°) is comparable to that by MA, although 100 W m−2 more direct SSR is extincted by DU and PD than by MA. DU and PD induce more diffuse SSR than MA that offsets larger reduction of direct SSR by DU and PD. Implications of the results to related researches are detailed discussed. The results are derived from aerosol and radiation data in the North China Plain, however the method can be used to any other stations with similar measurements. - Highlights: • A statistical method is developed to

  15. Radiation Pressure Approach to the Repulsive Casimir Force

    OpenAIRE

    Hushwater, V.

    1999-01-01

    We study the Casimir force between a perfectly conducting and an infinitely permeable plate with the radiation pressure approach. This method illustrates how a repulsive force arises as a consequence of the redistribution of the vacuum-field modes corresponding to specific boundary conditions. We discuss also how the method of the zero-point radiation pressure follows from QED.

  16. Exploring the Longwave Radiative Effects of Dust Aerosols

    Science.gov (United States)

    Hansell, Richard A., Jr.

    2012-01-01

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

  17. Investigation on seasonal variations of aerosol properties and its influence on radiative effect over an urban location in central India

    Science.gov (United States)

    Jose, Subin; Gharai, Biswadip; Niranjan, K.; Rao, P. V. N.

    2016-05-01

    Aerosol plays an important role in modulating solar radiation, which are of great concern in perspective of regional climate change. The study analysed the physical and optical properties of aerosols over an urban area and estimated radiative effect using three years in-situ data from sunphotometer, aethalometer and nephelometer as input to radiative transfer model. Aerosols properties indicate the dominance of fine mode aerosols over the study area. However presence of coarse mode aerosols is also found during pre-monsoon [March-April-May]. Daily mean aerosol optical depth showed a minimum during winter [Dec-Jan-Feb] (0.45-0.52) and a maximum during pre-monsoon (0.6-0.7), while single scattering albedo (ω) attains its maximum (0.78 ± 0.05) in winter and minimum (0.67 ± 0.06) during pre-monsoon and asymmetry factor varied in the range between 0.48 ± 0.02 to 0.53 ± 0.04. Episodic events of dust storm and biomass burning are identified by analyzing intrinsic aerosol optical properties like scattering Ångström exponent (SAE) and absorption Ångström exponent (AAE) during the study periods and it has been observed that during dust storm events ω is lower (∼0.77) than that of during biomass burning (∼0.81). The aerosol direct radiative effect at top of the atmosphere during winter is -11.72 ± 3.5 Wm-2, while during pre-monsoon; it is -5.5 ± 2.5 Wm-2, which can be due to observed lower values of ω during pre-monsoon. A large positive enhancement of atmospheric effect of ∼50.53 Wm-2 is observed during pre-monsoon compared to winter. Due to high aerosol loading in pre-monsoon, a twofold negative surface forcing is also observed in comparison to winter.

  18. Investigation of mineral aerosols radiative effects over High Mountain Asia in 1990-2009 using a regional climate model

    Science.gov (United States)

    Ji, Zhenming; Kang, Shichang; Zhang, Qianggong; Cong, Zhiyuan; Chen, Pengfei; Sillanpää, Mika

    2016-09-01

    Mineral aerosols scatter and absorb incident solar radiation in the atmosphere, and play an important role in the regional climate of High Mountain Asia (the domain includes the Himalayas, Tibetan Plateau, Pamir, Hindu-kush, Karakorum and Tienshan Mountains). Dust deposition on snow/ice can also change the surface albedo, resulting in perturbations in the surface radiation balance. However, most studies that have made quantitative assessments of the climatic effect of mineral aerosols over the High Mountain Asia region did not consider the impact of dust on snow/ice at the surface. In this study, a regional climate model coupled with an aerosol-snow/ice feedback module was used to investigate the emission, distribution, and deposition of dust and the climatic effects of aerosols over High Mountain Asia. Two sets of simulations driven by a reanalysis boundary condition were performed, i.e., with and without dust-climate feedback. Results indicated that the model captured the spatial and temporal features of the climatology and aerosol optical depth (AOD). High dust emission fluxes were simulated in the interior of the Tibetan Plateau (TP) and the Yarlung Tsangpo Valley in March-April-May (MAM), with a decreasing trend during 1990-2009. Dry deposition was controlled by the topography, and its spatial and seasonal features agreed well with the dust emission fluxes. The maximum wet deposition occurred in the western (southern and central) TP in MAM (JJA). A positive surface radiative forcing was induced by dust, including aerosol-snow/ice feedback, resulting in 2-m temperature increases of 0.1-0.5 °C over the western TP and Kunlun Mountains in MAM. Mineral dust also caused a decrease of 5-25 mm in the snow water equivalent (SWE) over the western TP, Himalayas, and Pamir Mountains in DJF and MAM. The long-term regional mean radiative forcing via dust deposition on snow showed an rising trend during 1990-2009, which suggested the contribution of aerosols surface

  19. The implication of radiative forcing and feedback for meridional energy transport

    Science.gov (United States)

    Huang, Yi; Zhang, Minghong

    2014-03-01

    The distributions of radiative forcing 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 radiation anomalies and implications for the meridional energy transport. It is found that because the greenhouse gas longwave forcing peaks in the low latitudes, it reinforces the equator-to-pole net radiation gradient and accounts for the increase in the poleward energy transport in both hemispheres under global warming. The shortwave forcing 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 radiation, the temperature and albedo feedback act against it. The feedback tend to offset the zonal mean radiation anomaly caused by the forcing, although the overall feedback effect on the energy transport is rather uncertain, mainly due to the uncertainty in the cloud feedback.

  20. Aerosol Characterization and New Instrumentation for Better Understanding Snow Radiative Properties

    Science.gov (United States)

    Beres, N. D.

    2015-12-01

    Snow albedo is determined by snowpack thickness and grain size, but also affected by contamination with light-absorbing, microscopic (e.g., mineral dust, combustion aerosols, bio-aerosols) and macroscopic (e.g., microalgae, plant debris, sand, organisms) compounds. Most currently available instruments for measuring snow albedo utilize the natural, downward flux of solar radiation and the reflected upward flux. This reliance on solar radiation (and, thus, large zenith angles and clear-sky conditions) leads to severe constraints, preventing characterization of detailed diurnal snow albedo cycles. Here, we describe instrumentation and methodologies to address these limitations with the development and deployment of new snow radiation sensors for measuring surface spectral and in-snow radiative properties. This novel instrumentation will be tested at the CRREL/UCSB Eastern Sierra (CUES) Snow Study Site at Mammoth Mountain, which is extensively instrumented for characterizing snow properties including snow albedo and surface morphology. However, it has been lacking instrumentation for the characterization of aerosols that can be deposited on the snow surface through dry and wet deposition. Currently, we are installing aerosol instrumentation at the CUES site, which are also described. This includes instruments for the multi-wavelength measurement of aerosol scattering and absorption coefficients and for the characterization of aerosol size distribution. Knowledge of aerosol concentration and physical and optical properties will allow for the study of aerosol deposition and modification of snow albedo and for establishing an aerosol climatology for the CUES site.

  1. Dusty cloud radiative forcing derived from satellite data for middle latitude regions of East Asia

    Institute of Scientific and Technical Information of China (English)

    HUANG Jianping; WANG Yujie; WANG Tianhe; YI Yuhong

    2006-01-01

    The dusty cloud radiative forcing over the middle latitude regions of East Asia was estimated by using the 2-year (July 2002-June 2004) data of collocated clouds and the Earth's radiant energy system (CERES) scanner and moderate resolution imaging spectroradiometer (MOD1S) from Aqua Edition 1B SSF (single scanner footprint). The dusty cloud is defined as the cloud in dust storm environment or dust contaminated clouds. For clouds growing in the presence of dust, the instantaneous short-wave (SW) forcing at the top of the atmosphere (TOA) is about - 275.7 W/m2 for cloud over dust (COD) region. The clouds developing in no-dust cloud (CLD) regions yield the most negative short-wave (SW) forcing ( - 311.0 W/m2), which is about 12.8 % stronger than those in COD regions.For long-wave (LW) radiative forcing, the no-dust cloud (CLD) is around 102.8 W/m2, which is 20% less than the LW forcing from COD regions. The instantaneous TOA net radiative forcing for the CLD region is about - 208.2 W/m2, which is 42.1% larger than the values of COD regions. The existence of dust aerosols under clouds significantly reduces the cooling effect of clouds.

  2. Premonsoon Aerosol Characterization and Radiative Effects Over the Indo-Gangetic Plains: Implications for Regional Climate Warming

    Science.gov (United States)

    Gautam, Ritesh; Hsu, N. Christina; Lau, K.-M.

    2010-01-01

    The Himalayas have a profound effect on the South Asian climate and the regional hydrological cycle, as it forms a barrier for the strong monsoon winds and serves as an elevated heat source, thus controlling the onset and distribution of precipitation during the Indian summer monsoon. Recent studies have suggested that radiative heating by absorbing aerosols, such as dust and black carbon over the Indo-Gangetic Plains (IGP) and slopes of the Himalayas, may significantly accelerate the seasonal warming of the Hindu Kush-Himalayas-Tibetan Plateau (HKHT) and influence the subsequent evolution of the summer monsoon. This paper presents a detailed characterization of aerosols over the IGP and their radiative effects during the premonsoon season (April-May-June) when dust transport constitutes the bulk of the regional aerosol loading, using ground radiometric and spaceborne observations. During the dust-laden period, there is a strong response of surface shortwave flux to aerosol absorption indicated by the diurnally averaged forcing efficiency of -70 W/sq m per unit optical depth. The simulated aerosol single-scattering albedo, constrained by surface flux and aerosol measurements, is estimated to be 0.89+/- 0.01 (at approx.550 nm) with diurnal mean surface and top-of-atmosphere forcing values ranging from -11 to -79.8 W/sq m and +1.4 to +12 W/sq m, respectively, for the premonsoon period. The model-simulated solar heating rate profile peaks in the lower troposphere with enhanced heating penetrating into the middle troposphere (5-6 km), caused by vertically extended aerosols over the IGP with peak altitude of approx.5 km as indicated by spaceborne Cloud-Aerosol Lidar with Orthogonal Polarization observations. On a long-term climate scale, our analysis, on the basis of microwave satellite measurements of tropospheric temperatures from 1979 to 2007, indicates accelerated annual mean warming rates found over the Himalayan-Hindu Kush region (0.21 C/decade+/-0.08 C

  3. Absorbing and scattering aerosols over the source region of biomass burning emissions: Implications in the assessment of optical and radiative properties

    Science.gov (United States)

    Singh, Atinderpal; Srivastava, Rohit; Rastogi, Neeraj; Singh, Darshan

    2016-02-01

    The current study focuses on the assessment of model simulated optical and radiative properties of aerosols incorporating the measured chemical composition of aerosol samples collected at Patiala during October, 2011-February, 2012. Monthly average mass concentration of PM2.5, elemental carbon (EC), primary organic carbon (POC), water-soluble (WS) and insoluble (INS) aerosols ranged from 120 to 192, 6.2 to 7.2, 20 to 39, 59 to 111 and 35 to 90 μg m-3, respectively. Mass concentration of different components of aerosols was further used for the assessment of optical properties derived from Optical Properties of Aerosols and Clouds (OPAC) model simulations. Microtops based measured aerosol optical depth (AOD500) ranged from 0.47 to 0.62 showing maximum value during November and December, and minimum during February. Ångström exponent (α380-870) remained high (>0.90) throughout the study period except in February (0.74), suggesting predominance of fine mode particles over the study region. The observed ratio of scattering to absorbing aerosols was incorporated in OPAC model simulations and single scattering albedo (SSA at 500 nm) so obtained ranged between 0.80 and 0.92 with relatively low values during the period of extensive biomass burning. In the present study, SBDART based estimated values of aerosol radiative forcing (ARF) at the surface (SRF) and top of the atmosphere (TOA) ranged from -31 to -66 Wm-2 and -2 to -18 W m-2 respectively. The atmospheric ARF, ranged between + 18 and + 58 Wm-2 resulting in the atmospheric heating rate between 0.5 and 1.6 K day-1. These results signify the role of scattering and absorbing aerosols in affecting the magnitude of aerosol forcing.

  4. Impact of radiatively interactive dust aerosols in the NASA GEOS-5 climate model: Sensitivity to dust particle shape and refractive index

    Science.gov (United States)

    Colarco, Peter R.; Nowottnick, Edward P.; Randles, Cynthia A.; Yi, Bingqi; Yang, Ping; Kim, Kyu-Myong; Smith, Jamison A.; Bardeen, Charles G.

    2014-01-01

    The radiative effects of Saharan dust aerosols are investigated in the NASA GEOS-5 atmospheric general circulation model. A sectional aerosol microphysics model (CARMA) is run online in GEOS-5. CARMA treats the dust aerosol lifecycle, and its tracers are radiatively coupled to GEOS-5. A series of AMIP-style simulations are performed, in which input dust optical properties (particle shape and refractive index) are varied. Simulated dust distributions for summertime Saharan dust compare well to observations, with best results found when the most absorbing dust optical properties are assumed. Dust absorption leads to a strengthening of the summertime Hadley cell circulation, increased dust lofting to higher altitudes, and a strengthening of the African easterly jet, resulting in increased dust atmospheric lifetime and farther northward and westward transport. We find a positive feedback of dust radiative forcing on emissions, in contrast with previous studies, which we attribute to our having a relatively strong longwave forcing caused by our simulating larger effective particle sizes. This longwave forcing reduces the magnitude of midday net surface cooling relative to other studies, and leads to a nighttime warming that results in higher nighttime wind speeds and dust emissions. The radiative effects of dust particle shape have only minor impact on transport and emissions, with small (~5%) impact on top of atmosphere shortwave forcing, in line with previous studies, but relatively more pronounced effects on shortwave atmospheric heating and surface forcing (~20% increase in atmospheric forcing for spheroids). Shape effects on longwave heating terms are of order ~10%.

  5. Sunphotometry of the 2006–2007 aerosol optical/radiative properties at the Himalayan Nepal Climate Observatory-Pyramid (5079 m a.s.l.

    Directory of Open Access Journals (Sweden)

    G. P. Gobbi

    2010-11-01

    Full Text Available In spite of being located at the heart of the highest mountain range in the world, the Himalayan Nepal Climate Observatory (5079 m a.s.l. at the Ev-K2-CNR Pyramid is shown to be affected by the advection of pollution aerosols from the populated regions of southern Nepal and the Indo-Gangetic plains. Such an impact is observed along most of the period April 2006–March 2007 addressed here, with a minimum in the monsoon season. Backtrajectory-analysis indicates long-range transport episodes occurring in this year to originate mainly in the west Asian deserts. At this high altitude site, the measured aerosol optical depth is observed to be about one order of magnitude lower than the one measured at Ghandi College (60 m a.s.l., in the Indo-Gangetic basin. As for Ghandi College, and in agreement with the in situ ground observations at the Pyramid, the fine mode aerosol optical depth maximizes during winter and minimizes in the monsoon season. Conversely, total optical depth maximizes during the monsoon due to the occurrence of elevated, coarse particle layers. Possible origins of these particles are wind erosion from the surrounding peaks and hydrated/cloud-processed aerosols. Assessment of the aerosol radiative forcing is then expected to be hampered by the presence of these high altitude particle layers, which impede an effective, continuous measurement of anthropogenic aerosol radiative properties from sky radiance inversions and/or ground measurements alone. Even though the retrieved absorption coefficients of pollution aerosols were rather large (single scattering albedo of the order of 0.6–0.9 were observed in the month of April 2006, the corresponding low optical depths (~0.03 at 500 nm are expected to limit the relevant radiative forcing. Still, the high specific forcing of this aerosol and its capability of altering snow surface albedo provide good reasons for continuous monitoring.

  6. Sunphotometry of the 2006-2007 aerosol optical/radiative properties at the Himalayan Nepal Climate Observatory-Pyramid (5079 m a.s.l.)

    Science.gov (United States)

    Gobbi, G. P.; Angelini, F.; Bonasoni, P.; Verza, G. P.; Marinoni, A.; Barnaba, F.

    2010-11-01

    In spite of being located at the heart of the highest mountain range in the world, the Himalayan Nepal Climate Observatory (5079 m a.s.l.) at the Ev-K2-CNR Pyramid is shown to be affected by the advection of pollution aerosols from the populated regions of southern Nepal and the Indo-Gangetic plains. Such an impact is observed along most of the period April 2006-March 2007 addressed here, with a minimum in the monsoon season. Backtrajectory-analysis indicates long-range transport episodes occurring in this year to originate mainly in the west Asian deserts. At this high altitude site, the measured aerosol optical depth is observed to be about one order of magnitude lower than the one measured at Ghandi College (60 m a.s.l.), in the Indo-Gangetic basin. As for Ghandi College, and in agreement with the in situ ground observations at the Pyramid, the fine mode aerosol optical depth maximizes during winter and minimizes in the monsoon season. Conversely, total optical depth maximizes during the monsoon due to the occurrence of elevated, coarse particle layers. Possible origins of these particles are wind erosion from the surrounding peaks and hydrated/cloud-processed aerosols. Assessment of the aerosol radiative forcing is then expected to be hampered by the presence of these high altitude particle layers, which impede an effective, continuous measurement of anthropogenic aerosol radiative properties from sky radiance inversions and/or ground measurements alone. Even though the retrieved absorption coefficients of pollution aerosols were rather large (single scattering albedo of the order of 0.6-0.9 were observed in the month of April 2006), the corresponding low optical depths (~0.03 at 500 nm) are expected to limit the relevant radiative forcing. Still, the high specific forcing of this aerosol and its capability of altering snow surface albedo provide good reasons for continuous monitoring.

  7. Effect of aerosols on solar UV irradiances during the Photochemical Activity and Solar Ultraviolet Radiation Campaign

    Science.gov (United States)

    Kylling, A.; Bais, A. F.; Blumthaler, M.; Schreder, J.; Zerefos, C. S.; Kosmidis, E.

    1998-10-01

    Surface UV irradiances were measured at two different sites in Greece during June 1996 under noncloudy conditions. The measured UV irradiances are simulated by a radiative transfer model using measured ozone density and aerosol optical depth profiles. The absolute difference between model and measurements ranges between -5% and +5% with little dependence on wavelength. The temporal and solar zenith angle dependence in the difference between model and measurement suggests that part of this difference may be explained by assumptions made about the aerosol single-scattering albedo and phase function. Simulated spectra including aerosols are compared with calculated spectra excluding aerosols. It is found that for otherwise similar atmospheric conditions the UVB irradiance is reduced with respect to aerosol free conditions by 5% to 35% depending on the aerosol optical depth and single-scattering albedo. For the campaign period, changes in the aerosol loading gave larger variations in the surface UV irradiances than the changes seen in the ozone column.

  8. Reconstruction of the Tambora forcing with global aerosol models : Challenges and limitations

    Science.gov (United States)

    Khodri, Myriam; Zanchettin, Davide; Timmreck, Claudia

    2016-04-01

    It is now generally recognised that volcanic eruptions have an important effect on climate variability from inter-annual to decadal timescales. For the largest tropical volcanic eruptions of the last millennium, simulated volcanic surface cooling derived from climate models often disagrees with the cooling seen in tree-ring-based proxies. Furthermore, cooling estimates from simulations show large uncertainties. Such disagreement can be related to several sources, including inconsistency of the currently available volcanic forcing datasets, unrealistic modelled volcanic forcing, insufficient representation of relevant climate processes, and different background climate states simulated at the time of the eruption. In particular, for eruptions that occurred before the observational period forcing characteristics related to the eruption magnitude and stratospheric aerosol properties are deduced from indirect evidences. So, while climatically relevant forcing properties for recent volcanic eruptions are relatively well constrained by direct observations, large uncertainties remain regarding processes of aerosol formation and evolution in the stratosphere after large tropical eruptions of the remote past. Several coordinated modelling assessments have been defined to frame future modeling activities and constrain the above-mentioned uncertainties. Among these, the sixth phase of the Coupled Model Intercomparison Project (CMIP6) has endorsed a multi-model assessment focused on the climatic response to strong volcanic eruptions (VolMIP). VolMIP defines a protocol for idealized volcanic-perturbation experiments to improve comparability among climate model results. Identification of a consensual volcanic forcing dataset for the 1815 Tambora eruption is a key step of VolMIP, as it is the largest-magnitude volcanic eruption of the past five centuries and reference for the VolMIP core experiments. Therefore, as a first key step, five current/state-of-the-art global aerosol

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

    Science.gov (United States)

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

    2014-11-01

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

  10. Attractive optical forces from black-body radiation

    CERN Document Server

    Sonnleitner, Matthias; Ritsch, Helmut

    2013-01-01

    Black-body radiation around hot objects induces AC Stark shifts of the energy levels of nearby atoms and molecules. These shifts are roughly proportional to the fourth power of the temperature and induce a force decaying with the third power of the distance from the object's surface. We explicitly calculate the resulting attractive black-body optical dipole force for ground state hydrogen atoms. Surprisingly this force can surpass the repulsive radiation pressure and actually pull the atoms towards the surface with a force stronger than gravity. We exemplify the dominance of the "black-body force" over gravity for hydrogen in a cloud of hot dust particles. These forces, which have been neglected to date, appear highly relevant in various astrophysical scenarios, in particular since analogous results hold for a wide class of broadband radiation sources.

  11. Aerosols and their influence on radiation partitioning and savanna productivity in northern Australia

    Energy Technology Data Exchange (ETDEWEB)

    Kanniah, K. D.; Beringer, J.; Tapper, N. J.; Long, Charles N.

    2010-05-01

    We investigated the effect of aerosols and clouds on the Net Ecosystem Productivity (NEP) of savannas in northern Australia using aerosol optical depth, clouds and radiation data from the Atmospheric Radiation Measurement (ARM) site in Darwin and carbon flux data measured from eddy covariance techniques from a site at Howard Springs, 35km southeast of Darwin. Generally we found that the concentration of aerosols in this region was relatively low than observed at other sites, therefore the proportion of diffuse radiation reaching the earths surface was only ~ 30%. As a result, we observed only a modest change in carbon uptake under aerosol laden skies and there was no significant difference for dry season Radiation Use Efficiency (RUE) between clear sky, aerosols or thin clouds. On the other hand thick clouds in the wet season produce much more diffuse radiation than aerosols or thin clouds and therefore the initial canopy quantum efficiency was seen to increase 45 and 2.5 times more than under thin clouds and aerosols respectively. The normalized carbon uptake under thick clouds is 57% and 50% higher than under aerosols and thin clouds respectively even though the total irradiance received under thick clouds was reduced 59% and 50% than under aerosols and thin clouds respectively. However, reduction in total irradiance decreases the mean absolute carbon uptake as much as 22% under heavy cloud cover compared to thin clouds or aerosols. Thus, any increase in aerosol concentration or cloud cover that can enhance the diffuse component may have large impacts on productivity in this region.

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

    OpenAIRE

    Hritz, A. D.; Raymond, T. M.; Dutcher, D. D.

    2016-01-01

    Accurate estimates of particle surface tension are required for models concerning atmospheric aerosol nucleation and activation. However, it is difficult to collect sufficiently large volumes of atmospheric aerosol for use in typical instruments that measure surface tension, such as goniometers or Wilhelmy plates. In this work, a method that measures the surface tension of collected liquid nanoparticles using atomic force microscopy is presented. A...

  13. Direct and Semi-direct Radiative Responses to Observation-Constrained Aerosol Absorption over S Asia

    Science.gov (United States)

    Feng, Y.; Kotamarthi, V. R.; Manoharan, V.

    2013-12-01

    Climate impacts of aerosols over S. Asia have been studied extensively in both models and observations. However, discrepancies between observed and modeled aerosol concentrations and optical properties have hindered our understanding of the aerosol influences on the regional monsoon circulation and rainfall. We present an in-depth examination of direct and semi-direct radiative responses due to aerosols on the latitudinal heating gradient and cloud distribution, with observational constraints on solar absorption by aerosols. Regional distributions of aerosol concentration are simulated with a 12-km regional climate model (WRF-Chem) driven by the NCEP analysis data from August 2011 to March 2012. During this time period, the ground-based measurements of aerosols and clouds, surface radiation, water vapor, and temperature were taken at Nainital (29.38°N, 79.45°E) during the DOE Ganges Valley Experiment (GVAX). This data set, which is available at high temporal resolution (hourly), is used to evaluate and constrain the simulated wavelength dependence of aerosol absorption and the correlation with changes in surface radiation, cloud base height and liquid water content for the entire post-monsoon period. The analysis is extended to a regional scale by comparing with satellite observation of absorbing aerosol optical depth (OMI) and cloud properties (MODIS). Preliminary results show good agreement in monthly variations of simulated and observed aerosol optical depth (AOD) except during periods of high observed AOD. Initial analysis indicates a possible local origin for the aerosols that is not captured in the model at present. Furthermore, analysis of the spectrally resolved aerosol absorption measurements indicates that these local aerosols exhibit strong absorption in near-UV and visible wavelengths. A large fraction of increased absorption during October and November (local fall harvest season) is attributable to the super-micron sized aerosol particles. In

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

    Science.gov (United States)

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

    2015-11-01

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

  15. Surface radiative forcing of forest disturbances over northeastern China

    International Nuclear Information System (INIS)

    Forests provide important climate forcing through biogeochemical and biogeophysical processes. In this study, we investigated the climatic effects of forest disturbances due to changes in forest biomass and surface albedo in terms of radiative forcing over northeastern China. Four types of forest disturbances were considered: fires, insect damage, logging, and afforestation and reforestation. The mechanisms of the influence of forest disturbances on climate were different. ‘Instantaneous’ net radiative forcings caused by fires, insect damage, logging, and afforestation and reforestation were estimated at 0.53 ± 0.08 W m−2, 1.09 ± 0.14 W m−2, 2.23 ± 0.27 W m−2, and 0.14 ± 0.04 W m−2, respectively. Trajectories of CO2-driven radiative forcing, albedo-driven radiative forcing, and net forcing were different with time for each type of disturbance. Over a decade, the estimated net forcings were 2.24 ± 0.11 W m−2, 0.20 ± 0.31 W m−2, 1.06 ± 0.41 W m−2, and −0.47 ± 0.07 W m−2, respectively. These estimated radiative forcings from satellite observations provided evidence for the mechanisms of the influences of forest disturbances on climate. (paper)

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

    Science.gov (United States)

    Deng, Jiechun; Xu, Haiming; Zhang, Leying

    2016-05-01

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

  17. Establishing Global Source-Receptor Relationships for Carbonaceous Aerosol to Characterize Sensitivity of its Climate Forcing to Emission Uncertainties

    Science.gov (United States)

    Wang, H.; Rasch, P. J.; Easter, R. C.; Singh, B.; Qian, Y.; Ma, P.; Zhang, R.

    2013-12-01

    Carbonaceous aerosol (CA) has been identified as an important but very uncertain forcing agent in the Earth's climate system. It has cascading radiative, microphysical and dynamical effects across the different scales in the atmosphere. Light-absorbing CA (e.g., black carbon (BC) and brown carbon) deposited on snow, sea ice and glaciers can accelerate their melting, which can induce more profound impact through positive feedback mechanisms, having important implications for climate change and fresh water availability at the global and regional scale. Many factors can affect the amount and impacts of CA in a specific region such as the Arctic, among which the global distribution of emissions is of primary importance. There are many uncertainties in global CA emissions, which are changing over time. To better understand the response of climate to these uncertainties and to potential future CA emission changes, it is useful to characterize the global source-receptor relationships and attribute CA loading and radiative forcing to various regional and sectoral CA sources. Observational evidence has clearly demonstrated the occurrence of intercontinental long-range transport of aerosols and to some extent the characteristic transport pathways. However, the observational approach alone cannot provide quantitative information on global source-receptor relationships. We have recently improved the treatment of aerosol transport and wet removal processes in the Community Atmosphere Model version 5 (CAM5) and introduced a brute-force aerosol source tagging technique in which aerosol particles emitted from many independent source regions and sectors are tagged and explicitly tracked. We run the CAM5 model in an 'offline' mode (i.e., driven by reanalysis data) so the transport processes are less likely to be subject to model biases in meteorology and circulation patterns. This modeling tool is used to quantify the characteristics (e.g., burden, surface deposition rate, lifetime

  18. Influence of aerosols on the life cycle of a radiation fog event. A numerical and observational study

    Science.gov (United States)

    Stolaki, S.; Haeffelin, M.; Lac, C.; Dupont, J.-C.; Elias, T.; Masson, V.

    2015-01-01

    Despite the knowledge gained on the physical processes dominating the formation, development and dissipation of radiation fog events, uncertainties still exist about the role of the microphysical processes related to aerosol characteristics. The objective of this work is to analyze the sensitivity of fog to aerosols through their impacts on the fog droplets. A radiation fog event that formed on 15/11/2011 at the SIRTA Observatory near Paris in the context of the 2011-2012 ParisFog field campaign is the basis of this study. The selected case is one that initially forms a few hundred meters above the surface and within half an hour lowers down to the surface. A combination of SIRTA's sophisticated observations and 1D numerical simulations is employed with the aim of better understanding the influence of thermodynamics and microphysics on the life-cycle of the fog event and the degree to which aerosol characteristics such as concentration of potentially activated aerosols, size and solubility affect its characteristics. It results that the model simulates fairly well the fog life cycle, with only one half hour advance in the onset and one hour in the dissipation at the surface. The quality of the reference simulation is evaluated against several in-situ and remote sensing measurements. A numerical sensitivity analysis shows that the fog characteristics are strongly influenced by the aerosols. Doubling (halving) the cloud condensation nuclei (CCN) number translates into a 160% increase (65% decrease) in the production of fog droplets, and a 60% increase (40% decrease) of the liquid water path (LWP). The aerosols influence up to 10% the fog geometrical thickness. The necessity for more detailed local forcings that will produce better thermohygrometric conditions in the upper levels above the formed fog layer is underlined, as well as the addition of microphysical measurements in the vertical that will allow to improve two-moment microphysics schemes.

  19. Towards Optimal Aerosol Information for the Retrieval of Solar Surface Radiation Using Heliosat

    Directory of Open Access Journals (Sweden)

    Richard Mueller

    2015-06-01

    Full Text Available High quality data of surface radiation is a prerequisite for climate monitoring (Earth radiation budget and solar energy applications. A very common method to derive solar surface irradiance is the Heliosat method, a one channel approach for the retrieval of the effective cloud albedo (CAL. This information is then used to derive the solar surface irradiance by application of a clear sky model. The results of this study are based on radiative transfer modelling, visual inspection of satellite images and evaluation of satellite based solar surface radiation with ground measurements. The respective results provide evidence that variations in Aerosol Optical depth induced by desert storms and biomass burning events lead to a significant increase of the effective cloud albedo, thus, that certain aerosol events are interpreted as clouds by the method. For the estimation of the solar surface radiation aerosol information is needed as input for the clear sky model. As the aerosol effect is partly considered by CAL, there is a need to modify external aerosol information for the use within the clear sky model, e.g., by truncation of high aerosol loads. Indeed, it has been shown that a modified version of the Monitoring Atmospheric Composition and Climate (MACC aerosol information leads to better accuracy of the retrieved solar surface radiation than the original MACC data for the investigated 9 sites and time period (2006–2009. Further, the assumption of a constant aerosol optical depth of 0.18 provides also better accuracies of the estimated solar surface radiation than the original MACC data for the investigated sites and period. It is concluded that this is partly due to the consideration of scattering aerosols by the effective cloud albedo.

  20. Distinct impact of different types of aerosols on surface solar radiation in China

    Science.gov (United States)

    Yang, Xin; Zhao, Chuanfeng; Zhou, Lijing; Wang, Yang; Liu, Xiaohong

    2016-06-01

    Observations of surface direct solar radiation (DSR) and visibility, particulate matter with aerodynamic diameters less than 2.5 µm (PM2.5), together with the aerosol optical thickness (AOT) taken from Moderate-Resolution Imaging Spectroradiometer and Multiangle Imaging Spectroradiometer, were investigated to gain insight into the impact of aerosol pollution on surface solar radiation in China. The surface DSR decreased during 2004-2014 compared with 1993~2003 over eastern China, but no clear reduction was observed in remote regions with cleaner air. Significant correlations of visibility, PM2.5, and regionally averaged AOT with the surface DSR over eastern China indicate that aerosol pollution greatly affects the energy available at the surface. The net loss of surface solar radiation also reduces the surface ground temperature over eastern China. However, the slope of the linear variation of the radiation with respect to atmospheric visibility is distinctly different at different stations, implying that the main aerosol type varies regionally. The largest slope value occurs at Zhengzhou and indicates that the aerosol absorption in central China is the highest, and lower slope values suggest relatively weakly absorbing types of aerosols at other locations. The spatial distribution of the linear slopes agrees well with the geographical distribution of the absorbing aerosols derived from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations and Ozone Monitoring Instrument over China. The regional correlation between a larger slope value and higher absorbance properties of aerosols indicates that the net effects of aerosols on the surface solar energy and corresponding climatic effects are dependent on both aerosol amount and optical properties.

  1. Analytical r-mode solution with gravitational radiation reaction force

    CERN Document Server

    Dias, O J C; S\\'a, Paulo M.

    2005-01-01

    We present and discuss the analytical r-mode solution to the linearized hydrodynamic equations of a slowly rotating, Newtonian, barotropic, non-magnetized, perfect-fluid star in which the gravitational radiation reaction force is present.

  2. Unravelling the effects of radiation forces in water.

    Science.gov (United States)

    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

  3. Education and training of radiation task forces for nuclear emergency situations

    International Nuclear Information System (INIS)

    The problem of education and training of the special task forces for radiation accidents is the produce conditions close to reality. The author describes the development of the software module S3Exercise (safety support systems) that allows to present emergency situations close to reality. The module S3FAST (field assessment survey tool) is an emergency management system for the real-time field data transfer to the emergency team headquarter. For the radiation release from nuclear power plants, nuclear submarines and dirty bombs typical radioactive inventory data are provided. The scenarios are loaded on GPS supported handheld computers and allow the following notifications: dose rate, personal dosimeter, contamination and aerosol activity. The trained personal is supplied with realistic detector readouts. The field exploration is based exclusively on the indicated ''measured values''. The behavior in a given radiation field can be trained. The software is successfully used in the Canadian marine in their NER (nuclear emergency response) teams for training purposes.

  4. Unravelling the effects of radiation forces in water

    OpenAIRE

    Astrath, Nelson G. C.; Malacarne, Luis C.; Mauro L. Baesso; 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 ...

  5. Radiative Corrections to the Casimir Force and Effective Field Theories

    Energy Technology Data Exchange (ETDEWEB)

    Melnikov, Kirill

    2001-07-25

    Radiative corrections to the Casimir force between two parallel plates are considered in both scalar field theory of one massless and one massive field and in QED. Full calculations are contrasted with calculations based on employing ''boundary-free'' effective field theories. The difference between two previous results on QED radiative corrections to the Casimir force between two parallel plates is clarified and the low-energy effective field theory for the Casimir effect in QED is constructed.

  6. Radiative corrections to the Casimir force and effective field theories

    Energy Technology Data Exchange (ETDEWEB)

    Melnikov, Kirill

    2001-08-15

    Radiative corrections to the Casimir force between two parallel plates are considered in both scalar field theory of one massless and one massive field and in QED. Full calculations are contrasted with calculations based on employing 'boundary-free' effective field theories. The difference between two previous results on QED radiative corrections to the Casimir force between two parallel plates is clarified and the low-energy effective field theory for the Casimir effect in QED is constructed.

  7. Dependence of the radiative forcing of the climate system on fossil fuel type

    Science.gov (United States)

    Nunez, L. I.

    2015-12-01

    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 radiative forcing for each type of fossil fuel. The historical (1850-2011) net radiative forcing 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 forcing on fuel type. The CO2 forcing per joule of energy is largest for coal. Radiative forcing from the co-emitted pollutants (black carbon, methane, nitrogen oxides, organic carbon, sulfate aerosols) changes the global mean CO2 forcing attributed to coal and oil significantly. For natural gas, the CO2-only radiative forcing from gas is increased by about 60% when the co-emitted pollutants are included.

  8. Forcing the Issue on Radiation Policy

    International Nuclear Information System (INIS)

    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

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

    OpenAIRE

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

    2016-01-01

    The radiative effect of anthropogenic aerosols over Europe during the 2008 European Integrated Project on Aerosol Cloud Climate and Air Quality Interactions Long Range Experiment (EUCAARI-LONGREX) campaign has been calculated using measurements collected by the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft and radiative transfer modelling. The aircraft sampled anthropogenically perturbed air masses across north-western Europe under anticyclonic conditio...

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

    Directory of Open Access Journals (Sweden)

    T. C. Bond

    2011-02-01

    Full Text Available Climatic effects of short-lived climate forcers (SLCFs differ from those of long-lived greenhouse gases, because they occur rapidly after emission and because they depend upon the region of emission. The distinctive temporal and spatial nature of these impacts is not captured by measures that rely on global averages or long time integrations. Here, we propose a simple measure, the Specific Forcing Pulse (SFP, to quantify climate warming or cooling by these pollutants, where we define "immediate" as occurring primarily within the first year after emission. SFP is the amount of energy added to or removed from a receptor region in the Earth-atmosphere system by a chemical species, per mass of emission in a source region. We limit the application of SFP to species that remain in the atmosphere for less than one year. Metrics used in policy discussions, such as total forcing or global warming potential, are easily derived from SFP. However, SFP conveys purely physical information without incurring the policy implications of choosing a time horizon for the global warming potential.

    Using one model (Community Atmosphere Model, or CAM, we calculate values of SFP for black carbon (BC and organic matter (OM emitted from 23 source-region combinations. Global SFP for both atmosphere and cryosphere impacts is divided among receptor latitudes. SFP is usually greater for open-burning emissions than for energy-related (fossil-fuel and biofuel emissions because of the timing of emission. Global SFP for BC varies by about 45% for energy-related emissions from different regions. This variation would be larger except for compensating effects. When emitted aerosol has larger cryosphere forcing, it often has lower atmosphere forcing because of less deep convection and a shorter atmospheric lifetime.

    A single model result is insufficient to capture uncertainty. We develop a best estimate and uncertainties for SFP by combining forcing results from

  11. Simulated radiative forcing from contrails and contrail cirrus

    Directory of Open Access Journals (Sweden)

    C.-C. Chen

    2013-04-01

    Full Text Available 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.

  12. Aerosol Effects on Radiation and Climate: Column Closure Experiments with Towers, Aircraft, and Satellites

    Science.gov (United States)

    Russell, Philip B.

    1994-01-01

    Many theoretical studies have shown that anthropogenic aerosol particles can change the radiation balance in an atmospheric column and might thereby exert a significant effect on the Earth's climate. In particular, recent calculations have shown that sulfate particles from anthropogenic combustion may already exert a cooling influence on the Earth that partially offsets the warming caused by the greenhouse gases from the same combustion. Despite the potential climatic importance of anthropogenic aerosols, simultaneous measurements of anthropogenic aerosol properties and their effect on atmospheric radiation have been very rare. Successful comparisons of measured radiation fields with those calculated from aerosol measurements - now referred to as column closure comparisons - are required to improve the accuracy and credibility of climate predictions. This paper reviews the column closure experiment performed at the Mt. Sutro Tower in San Francisco in 1975, in which elevated radiometers measured the change in Earth-plus-atmosphere albedo caused by an aerosol layer, while a lidar, sunphotometer, nephelometer, and other radiometers measured properties of the responsible aerosol. The time-dependent albedo calculated from the measured aerosol properties agreed with that measured by the tower radiometers. Also presented are designs for future column closure studies using radiometers and aerosol instruments on the ground, aircraft, and satellites. These designs draw upon algorithms and experience developed in the Sutro Tower study, as well as more recent experience with current measurement and analysis capabilities.

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

    Science.gov (United States)

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

    2013-01-01

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

  14. Consistent sets of atmospheric lifetimes and radiative forcings on climate for CFC replacements: HCFCs and HFCs

    Science.gov (United States)

    Naik, Vaishali; Jain, Atul K.; Patten, Kenneth O.; Wuebbles, Donald J.

    2000-03-01

    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 radiative forcing 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 radiative forcings for these compounds by adopting a uniform approach. Using the latest version of our two-dimensional chemical-radiative-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 radiative forcings for CFC-11 and 20 other halocarbons using our radiative transfer model. The sensitivity of radiative forcings to the vertical distribution of these gases is investigated in this study and is shown to be significant. The difference in the global radiative forcing arising from the assumption of a

  15. Mesoscale modelling study of the interactions between aerosols and PBL meteorology during a haze episode in China Jing-Jin-Ji and its near surrounding region - Part 2: Aerosols' radiative feedback effects

    Science.gov (United States)

    Wang, H.; Shi, G. Y.; Zhang, X. Y.; Gong, S. L.; Tan, S. C.; Chen, B.; Che, H. Z.; Li, T.

    2015-03-01

    Two model experiments, namely a control (CTL) experiment without aerosol-radiation feedbacks and a experiment with online aerosol-radiation (RAD) interactions, were designed to study the radiative feedback on regional radiation budgets, planetary boundary layer (PBL) meteorology and haze formation due to aerosols during haze episodes over Jing-Jin-Ji, China, and its near surroundings (3JNS region of China: Beijing, Tianjin, Hebei, East Shanxi, West Shandong and North Henan) with a two-way atmospheric chemical transport model. The impact of aerosols on solar radiation reaching Earth's surface, outgoing long-wave emission at the top of the atmosphere, air temperature, PBL turbulence diffusion, PBL height, wind speeds, air pressure pattern and PM2.5 has been studied focusing on a haze episode during the period from 7 to 11 July 2008. The results show that the mean solar radiation flux that reaches the ground decreases by about 15% in 3JNS and 20 to 25%in the region with the highest aerosol optical depth during the haze episode. The fact that aerosol cools the PBL atmosphere but warms the atmosphere above it leads to a more stable atmospheric stratification over the region, which causes a decrease in turbulence diffusion of about 52% and a decrease in the PBL height of about 33%. This consequently forms a positive feedback on the particle concentration within the PBL and the surface as well as the haze formation. Additionally, aerosol direct radiative forcing (DRF) increases PBL wind speed by about 9% and weakens the subtropical high by about 14 hPa, which aids the collapse of haze pollution and results in a negative feedback to the haze episode. The synthetic impacts from the two opposite feedbacks result in about a 14% increase in surface PM2.5. However, the persistence time of both high PM2.5 and haze pollution is not affected by the aerosol DRF. On the contrary over offshore China, aerosols heat the PBL atmosphere and cause unstable atmospheric stratification, but

  16. Response of Mode Water and Subtropical Countercurrent to Greenhouse Gas and Aerosol Forcing in the North Pacific

    Institute of Scientific and Technical Information of China (English)

    WANG Liyi; LIU Qinyu; XU Lixiao; XIE Shang-Ping

    2013-01-01

    The response of the North Pacific Subtropical Mode Water and Subtropical Countercurrent (STCC) to changes in greenhouse gas (GHG) and aerosol is investigated based on the 20th-century historical and single-forcing simulations with the Geophysical Fluid Dynamics Laboratory Climate Model version 3 (GFDL CM3).The aerosol effect causes sea surface temperature (SST)to decrease in the mid-latitude North Pacific,especially in the Kuroshio Extension region,during the past five decades (1950-2005),and this cooling effect exceeds the warming effect by the GHG increase.The STCC response to the GHG and aerosol forcing are opposite.In the GHG (aerosol) forcing run,the STCC decelerates (accelerates) due to the decreased (increased) mode waters in the North Pacific,resulting from a weaker (stronger) front in the mixed layer depth and decreased (increased) subduction in the mode water formation region.The aerosol effect on the SST,mode waters and STCC more than offsets the GHG effect.The response of SST in a zonal band around 40°N and the STCC to the combined forcing in the historical simulation is similar to the response to the aerosol forcing.

  17. The initial dispersal and radiative forcing of a Northern Hemisphere mid latitude super volcano: a Yellowstone case study

    OpenAIRE

    Timmreck, C.; Graf, H.-F.

    2005-01-01

    International audience The chemistry climate model MAECHAM4/CHEM with interactive and prognostic volcanic aerosol and ozone, was used to study the initial dispersal and radiative forcing of a possible Yellowstone super eruption. Tropospheric climate anomalies are not analysed since sea surface temperatures are kept fix. Our experiments show that the global dispersal of a Yellowstone super eruption is strongly dependent on the season of the eruption. In Northern Hemisphere summer the volcan...

  18. Response of different regional online coupled models to aerosol-radiation interactions

    Science.gov (United States)

    Forkel, Renate; Balzarini, Alessandra; Brunner, Dominik; Baró, Rocio; Curci, Gabriele; Hirtl, Marcus; Honzak, Luka; Jiménez-Guerrero, Pedro; Jorba, Oriol; Pérez, Juan L.; Pirovano, Guido; San José, Roberto; Schröder, Wolfram; Tuccella, Paolo; Werhahn, Johannes; Wolke, Ralf; Žabkar, Rahela

    2016-04-01

    The importance of aerosol-meteorology interactions and their representation in online coupled regional atmospheric chemistry-meteorology models was investigated in COST Action ES1004 (EuMetChem, http://eumetchem.info/). Case study results from different models (COSMO-Muscat, COSMO-ART, and different configurations of WRF-Chem), which were applied for Europe as a coordinated exercise for the year 2010, are analyzed with respect to inter-model variability and the response of the different models to direct and indirect aerosol-radiation interactions. The main focus was on two episodes - the Russian heat wave and wildfires episode in July/August 2010 and a period in October 2010 with enhanced cloud cover and rain and including an of Saharan dust transport to Europe. Looking at physical plausibility the decrease in downward solar radiation and daytime temperature due to the direct aerosol effect is robust for all model configurations. The same holds for the pronounced decrease in cloud water content and increase in solar radiation for cloudy conditions and very low aerosol concentrations that was found for WRF-Chem when aerosol cloud interactions were considered. However, when the differences were tested for statistical significance no significant differences in mean solar radiation and mean temperature between the baseline case and the simulations including the direct and indirect effect from simulated aerosol concentrations were found over Europe for the October episode. Also for the fire episode differences between mean temperature and radiation from the simulations with and without the direct aerosol effect were not significant for the major part of the modelling domain. Only for the region with high fire emissions in Russia, the differences in mean solar radiation and temperature due to the direct effect were found to be significant during the second half of the fire episode - however only for a significance level of 0.1. The few observational data indicate that

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

    Science.gov (United States)

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

    2014-05-01

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

  20. Impact of transpacific aerosol on air quality over the United States: A perspective from aerosol-cloud-radiation interactions

    Science.gov (United States)

    Tao, Zhining; Yu, Hongbin; Chin, Mian

    2016-01-01

    Observations have well established that aerosols from various sources in Asia, Europe, and Africa can travel across the Pacific and reach the contiguous United States (U.S.) at least on episodic bases throughout a year, with a maximum import in spring. The imported aerosol not only can serve as an additional source to regional air pollution (e.g., direct input), but also can influence regional air quality through the aerosol-cloud-radiation (ACR) interactions that change local and regional meteorology. This study assessed impacts of the transpacific aerosol on air quality, focusing on surface ozone and PM2.5, over the U.S. using the NASA Unified Weather Research Forecast model. Based on the results of 3-month (April to June of 2010) simulations, the impact of direct input (as an additional source) of transpacific aerosol caused an increase of surface PM2.5 concentration by approximately 1.5 μg m-3 over the west coast and about 0.5 μg m-3 over the east coast of the U.S. By influencing key meteorological processes through the ACR interactions, the transpacific aerosol exerted a significant effect on both surface PM2.5 (±6 μg m-3) and ozone (±12 ppbv) over the central and eastern U.S. This suggests that the transpacific transport of aerosol could either improve or deteriorate local air quality and complicate local effort toward the compliance with the U.S. National Ambient Air Quality Standards.

  1. Evaluating the skill of high-resolution WRF-Chem simulations in describing drivers of aerosol direct climate forcing on the regional scale

    Science.gov (United States)

    Crippa, P.; Sullivan, R. C.; Thota, A.; Pryor, S. C.

    2016-01-01

    Assessing the ability of global and regional models to describe aerosol optical properties is essential to reducing uncertainty in aerosol direct radiative forcing in the contemporary climate and to improving confidence in future projections. Here we evaluate the performance of high-resolution simulations conducted using the Weather Research and Forecasting model with coupled with Chemistry (WRF-Chem) in capturing spatiotemporal variability of aerosol optical depth (AOD) and the Ångström exponent (AE) by comparison with ground- and space-based remotely sensed observations. WRF-Chem is run over eastern North America at a resolution of 12 km for a representative year (2008). A systematic positive bias in simulated AOD relative to observations is found (annual mean fractional bias (MFB) is 0.15 and 0.50 relative to MODIS (MODerate resolution Imaging Spectroradiometer) and AERONET, respectively), whereas the spatial variability is well captured during most months. The spatial correlation of observed and simulated AOD shows a clear seasonal cycle with highest correlation during summer months (r = 0.5-0.7) when the aerosol loading is large and more observations are available. The model is biased towards the simulation of coarse-mode aerosols (annual MFB for AE = -0.10 relative to MODIS and -0.59 for AERONET), but the spatial correlation for AE with observations is 0.3-0.5 during most months, despite the fact that AE is retrieved with higher uncertainty from the remote-sensing observations. WRF-Chem also exhibits high skill in identifying areas of extreme and non-extreme aerosol loading, and its ability to correctly simulate the location and relative intensity of extreme aerosol events (i.e., AOD > 75th percentile) varies between 30 and 70 % during winter and summer months, respectively.

  2. Imaging spectroscopy of albedo and radiative forcing by light-absorbing impurities in mountain snow

    Science.gov (United States)

    Painter, Thomas H.; Seidel, Felix C.; Bryant, Ann C.; McKenzie Skiles, S.; Rittger, Karl

    2013-09-01

    Recent studies show that deposition of dust and black carbon to snow and ice accelerates snowmelt and perturbs regional climate and hydrologic cycles. Radiative forcing 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 Radiative Forcing (IS-SnARF)) that provides quantitative retrievals of snow grain size, snow albedo, and radiative forcing 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. Radiative forcing 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 radiative forcing 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.

  3. Tropospheric Aerosols

    Science.gov (United States)

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

    2003-12-01

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

  4. Global model simulations of the impact of ocean-going ships on aerosols, clouds, and the radiation budget

    Directory of Open Access Journals (Sweden)

    A. Lauer

    2007-10-01

    atmosphere (ToA under clear-sky condition of about −0.014 W/m² to −0.038 W/m² for a global annual average. The corresponding all-sky direct aerosol forcing ranges between −0.011 W/m² and −0.013 W/m². The indirect aerosol effect of ships on climate is found to be far larger than previously estimated. An indirect radiative effect of −0.19 W/m² to −0.60 W/m² (a change in the atmospheric shortwave radiative flux at ToA is calculated here, contributing 17% to 39% of the total indirect effect of anthropogenic aerosols. This contribution is high because ship emissions are released in regions with frequent low marine clouds in an otherwise clean environment. In addition, the potential impact of particulate matter on the radiation budget is larger over the dark ocean surface than over polluted regions over land.

  5. A satellite view of the direct effect of aerosols on solar radiation at global scale

    Science.gov (United States)

    Hatzianastassiou, Nikolaos; Papadimas, Christos D.; Matsoukas, Christos; Fotiadi, Aggeliki; Benas, Nikolaos; Vardavas, Ilias

    2016-04-01

    Aerosols are a key parameter for better understanding and predicting current and future climate change. They are determining, apart from clouds, patterns of solar radiation through scattering and absorption processes. Especially, under cloud-free skies, aerosols are the major modulator of the solar radiation budget of the Earth-atmosphere system. Although significant improvement has been made as to better understanding the direct radiative effect (DRE) of aerosols, there is still a need for further improvement in our knowledge of the DRE spatial and temporal patterns, in particular with respect to extended spatial and temporal coverage of relevant information. In an ongoing rapidly evolving era of great satellite-based achievements, concerning the knowledge of solar radiation budget and its modulators, and with the great progress in obtaining significant information on key aerosol optical properties needed for modeling DRE, it is a great challenge to use all this new aerosol information and to see what is the new acquired scientific knowledge. The objective of this study is to obtain an improved view of global aerosol DRE effects using contemporary accurate data for the important atmospheric and surface parameters determining the solar radiation budget, with emphasis to state of the art aerosol data. Thus, a synergy is made of different datasets providing the necessary input data and of a detailed spectral radiative transfer model (RTM) to compute spectral globally distributed aerosol DREs. Emphasis is given on using highly accurate and well-tested aerosol optical properties. Spectral information on aerosol optical depth (AOD) is taken from retrieved products of the MODerate resolution Imaging Spectroradiometer (MODIS) instrument, while similar information is taken from MODIS for the aerosol asymmetry parameter (AP) over ocean. Information from MODIS is also taken for the aerosol single scattering albedo (SSA). All this information comes from the latest Collection

  6. Forcing the issue on radiation policy

    International Nuclear Information System (INIS)

    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

  7. Aerosols attenuating the solar radiation collected by solar tower plants: The horizontal pathway at surface level

    Science.gov (United States)

    Elias, Thierry; Ramon, Didier; Dubus, Laurent; Bourdil, Charles; Cuevas-Agulló, Emilio; Zaidouni, Taoufik; Formenti, Paola

    2016-05-01

    Aerosols attenuate the solar radiation collected by solar tower plants (STP), along two pathways: 1) the atmospheric column pathway, between the top of the atmosphere and the heliostats, resulting in Direct Normal Irradiance (DNI) changes; 2) the grazing pathway close to surface level, between the heliostats and the optical receiver. The attenuation along the surface-level grazing pathway has been less studied than the aerosol impact on changes of DNI, while it becomes significant in STP of 100 MW or more. Indeed aerosols mostly lay within the surface atmospheric layer, called the boundary layer, and the attenuation increases with the distance covered by the solar radiation in the boundary layer. In STP of 100 MW or more, the distance between the heliostats and the optical receiver becomes large enough to produce a significant attenuation by aerosols. We used measured aerosol optical thickness and computed boundary layer height to estimate the attenuation of the solar radiation at surface level at Ouarzazate (Morocco). High variabilities in aerosol amount and in vertical layering generated a significant magnitude in the annual cycle and significant inter-annual changes. Indeed the annual mean of the attenuation caused by aerosols over a 1-km heliostat-receiver distance was 3.7% in 2013, and 5.4% in 2014 because of a longest desert dust season. The monthly minimum attenuation of less than 3% was observed in winter and the maximum of more than 7% was observed in summer.

  8. Assimilation of Aerosols from Biomass Burning by the Radiative Transfer Model Brasil-Sr

    Science.gov (United States)

    Costa, R. S.; Gonçalves, A. R.; Souza, J. G.; Martins, F. R.; Pereira, E. B.

    2015-12-01

    The radiative transfer model BRASIL-SR is the main tool used by the Earth System Science Centre from the National Institute for Space Research (CCST / INPE) for solar energy resource assessment. Due to large and frequent events of burning biomass in Brazil there is a need to improve the aerosol representation in this model, mainly during the dry season (September - November) in Northern and Central Brazil. The standard aerosol representation in this model is inadequate to capture these events. It is based on the mean monthly climatological horizontal visibility with latitudinal values based on coarse global observation data. To improve the aerosol representation, climatological data of daily horizontal visibility from National Institute of Meteorology (INMET) was used to generate monthly averages from 1999 to 2012. To do a better representation of aerosols from burning biomass events, from megacities aerosol generation, and from transport processes, horizontal visibility estimates performed using aerosol optical thickness at 550 nm data from MACC Project Reanalysis model were used to adjust the aerosol representation in regions were the simple horizontal visibility fails. A methodology to generate these new visibility data from the Reanalysis was made and the resulting data was compared with the average horizontal visibility to implement a new corrected database. The solar irradiation simulated by the model using this new aerosol representation proved to be better than the previous version of the model in all regions with high aerosol loading.

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

    International Nuclear Information System (INIS)

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

  10. Aerosols in the Convective Boundary Layer: Radiation Effects on the Coupled Land-Atmosphere System

    Science.gov (United States)

    Barbaro, E.; Vila-Guerau Arellano, J.; Ouwersloot, H. G.; Schroter, J.; Donovan, D. P.; Krol, M. C.

    2013-12-01

    We investigate the responses of the surface energy budget and the convective boundary-layer (CBL) dynamics to the presence of aerosols using a combination of observations and numerical simulations. A detailed observational dataset containing (thermo)dynamic variables observed at CESAR (Cabauw Experimental Site for Atmospheric Research) and aerosol information from the European Integrated Project on Aerosol, Cloud, Climate, and Air Quality Interactions (IMPACT/EUCAARI) campaign is employed to design numerical experiments reproducing two prototype clear-sky days characterized by: (i) a well-mixed residual layer above a ground inversion and (ii) a continuously growing CBL. A large-eddy simulation (LES) model and a mixed-layer (MXL) model, both coupled to a broadband radiative transfer code and a land-surface model, are used to study the impacts of aerosol scattering and absorption of shortwave radiation on the land-atmosphere system. We successfully validate our model results using the measurements of (thermo)dynamic variables and aerosol properties for the two different CBL prototypes studied here. Our findings indicate that in order to reproduce the observed surface energy budget and CBL dynamics, information of the vertical structure and temporal evolution of the aerosols is necessary. Given the good agreement between the LES and the MXL model results, we use the MXL model to explore the aerosol effect on the land-atmosphere system for a wide range of optical depths and single scattering albedos. Our results show that higher loads of aerosols decrease irradiance, imposing an energy restriction at the surface. Over the studied well-watered grassland, aerosols reduce the sensible heat flux more than the latent heat flux. As a result, aerosols increase the evaporative fraction. Moreover, aerosols also delay the CBL morning onset and anticipate its afternoon collapse. If also present above the CBL during the morning transition, aerosols maintain a persistent near

  11. Sunphotometry of the 2006–2007 aerosol optical/radiative properties at the Himalayan Nepal Climate Observatory – Pyramid (5079 m a.s.l.

    Directory of Open Access Journals (Sweden)

    G. P. Gobbi

    2010-01-01

    Full Text Available In spite of being located at the heart of the highest mountain range in the world, the Himalayan Nepal Climate Observatory (5079 m a.s.l. at the Ev-K2-CNR Pyramid is shown to be affected by the advection of pollution aerosols from the populated regions of southern Nepal and the Indo-Gangetic plains. Such an impact is observed along most of the period April 2006–March 2007 addressed here, with a minimum in the monsoon season. Backtrajectory-analysis indicates long-range transport episodes occurring in this period to originate mainly in the West Asian deserts. At this high altitude site, the measured aerosol optical depth is observed to be: 1 about one order of magnitude lower than the one measured at Gandhi College (60 m a.s.l., in the Indo-Gangetic basin, and 2 maximum during the monsoon period, due to the presence of elevated (cirrus-like particle layers. Assessment of the aerosol radiative forcing results to be hampered by the persistent presence of these high altitude particle layers, which impede a continuous measurement of both the aerosol optical depth and its radiative properties from sky radiance inversions. Even though the retrieved absorption coefficients of pollution aerosols was rather large (single scattering albedo of the order of 0.6–0.9 were observed in the month of April 2006, the corresponding low optical depths (~0.03 at 500 nm are expected to limit the relevant radiative forcings. Still, the high specific forcing of this aerosol and its capability of altering snow surface albedo provide good reason for continuous monitoring.

  12. Mesoscale modeling study of the interactions between aerosols and PBL meteorology during a haze episode in China Jing-Jin-Ji and its near surrounding region - Part 2: Aerosols' radiative feedback effects

    Science.gov (United States)

    Wang, H.; Shi, G. Y.; Zhang, X. Y.; Gong, S. L.; Tan, S. C.; Chen, B.; Che, H. Z.; Li, T.

    2014-11-01

    Two model experiments, namely a control (CTL) experiment without aerosol-radiation feedbacks and a RAD experiment with online aerosol-radiation interactions, were designed to study the radiative feedback on regional radiation budgets, PBL meteorology and haze formation due to aerosols during haze episodes over China Jing-Jin-Ji and its near surroundings (3JNS Region, for Beijing, Tianjin, Hebei Province, East Shanxi Province, West Shandong Province and North Henan Province) with a two-way atmospheric chemical transport model. The impact of aerosols on solar radiation reaching Earth's surface, outgoing longwave emission at the top of the atmosphere, air temperature, PBL turbulence diffusion, PBL height, wind speeds, air pressure pattern and PM2.5 has been studied focusing on a haze episode during the period from 7 to 11 July 2008. The results show that the mean solar radiation flux that reaches the ground decreases about 15% in China 3JNS Region and by 20 to 25% in the region with the highest AOD during the haze episode. The fact that aerosol cools the PBL atmosphere but warms the atmosphere above it leads to a more stable atmospheric stratification over the region, which causes a decrease in about 52% of turbulence diffusion and a decrease in about 33% of the PBL height. This consequently forms a positive feedback on the particle concentration within the PBL and the surface as well as the haze formation. On the other hands, aerosol DRF (direct radiative forcing) increases about 9% of PBL wind speed, weakens the subtropical high by about 14 hPa, which aids the collapse of haze pollution, resulting in a negative feedback to the haze episode. The synthetic impacts from the two opposite feedbacks result in about a 14% increase in surface PM2.5. However, the persistence time of both high PM2.5 and haze pollution is not effected by the aerosol DRF. On the contrary over offshore China, aerosols heat the PBL atmosphere and cause unstable atmospheric stratification, but the

  13. Mesoscale modeling study of the interactions between aerosols and PBL meteorology during a haze episode in China Jing-Jin-Ji and its near surrounding region – Part 2: Aerosols' radiative feedback effects

    Directory of Open Access Journals (Sweden)

    H. Wang

    2014-11-01

    Full Text Available Two model experiments, namely a control (CTL experiment without aerosol-radiation feedbacks and a RAD experiment with online aerosol-radiation interactions, were designed to study the radiative feedback on regional radiation budgets, PBL meteorology and haze formation due to aerosols during haze episodes over China Jing-Jin-Ji and its near surroundings (3JNS Region, for Beijing, Tianjin, Hebei Province, East Shanxi Province, West Shandong Province and North Henan Province with a two-way atmospheric chemical transport model. The impact of aerosols on solar radiation reaching Earth's surface, outgoing longwave emission at the top of the atmosphere, air temperature, PBL turbulence diffusion, PBL height, wind speeds, air pressure pattern and PM2.5 has been studied focusing on a haze episode during the period from 7 to 11 July 2008. The results show that the mean solar radiation flux that reaches the ground decreases about 15% in China 3JNS Region and by 20 to 25% in the region with the highest AOD during the haze episode. The fact that aerosol cools the PBL atmosphere but warms the atmosphere above it leads to a more stable atmospheric stratification over the region, which causes a decrease in about 52% of turbulence diffusion and a decrease in about 33% of the PBL height. This consequently forms a positive feedback on the particle concentration within the PBL and the surface as well as the haze formation. On the other hands, aerosol DRF (direct radiative forcing increases about 9% of PBL wind speed, weakens the subtropical high by about 14 hPa, which aids the collapse of haze pollution, resulting in a negative feedback to the haze episode. The synthetic impacts from the two opposite feedbacks result in about a 14% increase in surface PM2.5. However, the persistence time of both high PM2.5 and haze pollution is not effected by the aerosol DRF. On the contrary over offshore China, aerosols heat the PBL atmosphere and cause unstable atmospheric

  14. The model evaluation of subsonic aircraft effect on the ozone and radiative forcing

    Energy Technology Data Exchange (ETDEWEB)

    Rozanov, E.; Zubov, V.; Egorova, T.; Ozolin, Y. [Main Geophysical Observatory, St.Petersburg (Russian Federation)

    1997-12-31

    Two dimensional transient zonally averaged model was used for the evaluation of the effect of subsonic aircraft exhausts upon the ozone, trace gases and radiation in the troposphere and lower stratosphere. The mesoscale transformation of gas composition was included on the base of the box model simulations. It has been found that the transformation of the exhausted gases in sub-grid scale is able to influence the results of the modelling. The radiative forcing caused by gas, sulfate aerosol, soot and contrails changes was estimated as big as 0.12-0.15 W/m{sup 2} (0.08 W/m{sup 2} globally and annually averaged). (author) 10 refs.

  15. Modeling dust as component minerals in the Community Atmosphere Model: development of framework and impact on radiative forcing

    Directory of Open Access Journals (Sweden)

    R. A. Scanza

    2014-07-01

    Full Text Available The mineralogy of desert dust is important due to its effect on radiation, clouds and biogeochemical cycling of trace nutrients. This study presents the simulation of dust radiative forcing as a function of both mineral composition and size at the global scale using mineral soil maps for estimating emissions. Externally mixed mineral aerosols in the bulk aerosol module in the Community Atmosphere Model version 4 (CAM4 and internally mixed mineral aerosols in the modal aerosol module in the Community Atmosphere Model version 5.1 (CAM5 embedded in the Community Earth System Model version 1.0.5 (CESM are speciated into common mineral components in place of total dust. The simulations with mineralogy are compared to available observations of mineral atmospheric distribution and deposition along with observations of clear-sky radiative forcing efficiency. Based on these simulations, we estimate the all-sky direct radiative forcing at the top of the atmosphere as +0.05 W m−2 for both CAM4 and CAM5 simulations with mineralogy and compare this both with simulations of dust in release versions of CAM4 and CAM5 (+0.08 and +0.17 W m−2 and of dust with optimized optical properties, wet scavenging and particle size distribution in CAM4 and CAM5, −0.05 and −0.17 W m−2, respectively. The ability to correctly include the mineralogy of dust in climate models is hindered by its spatial and temporal variability as well as insufficient global in-situ observations, incomplete and uncertain source mineralogies and the uncertainties associated with data retrieved from remote sensing methods.

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

    OpenAIRE

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

    2013-01-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

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

    OpenAIRE

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

    2014-01-01

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

  19. Estimating trace gas and aerosol emissions over South America: Relationship between fire radiative energy released and aerosol optical depth observations

    Science.gov (United States)

    Pereira, Gabriel; Freitas, Saulo R.; Moraes, Elisabete Caria; Ferreira, Nelson Jesus; Shimabukuro, Yosio Edemir; Rao, Vadlamudi Brahmananda; Longo, Karla M.

    2009-12-01

    Contemporary human activities such as tropical deforestation, land clearing for agriculture, pest control and grassland management lead to biomass burning, which in turn leads to land-cover changes. However, biomass burning emissions are not correctly measured and the methods to assess these emissions form a part of current research area. The traditional methods for estimating aerosols and trace gases released into the atmosphere generally use emission factors associated with fuel loading and moisture characteristics and other parameters that are hard to estimate in near real-time applications. In this paper, fire radiative power (FRP) products were extracted from Moderate Resolution Imaging Spectroradiometer (MODIS) and from the Geostationary Operational Environmental Satellites (GOES) fire products and new South America generic biomes FRE-based smoke aerosol emission coefficients were derived and applied in 2002 South America fire season. The inventory estimated by MODIS and GOES FRP measurements were included in Coupled Aerosol-Tracer Transport model coupled to the Brazilian developments on the Regional Atmospheric Modeling System (CATT-BRAMS) and evaluated with ground truth collected in Large Scale Biosphere-Atmosphere Smoke, Aerosols, Clouds, rainfall, and Climate (SMOCC) and Radiation, Cloud, and Climate Interactions (RaCCI). Although the linear regression showed that GOES FRP overestimates MODIS FRP observations, the use of a common external parameter such as MODIS aerosol optical depth product could minimize the difference between sensors. The relationship between the PM 2.5μm (Particulate Matter with diameter less than 2.5 μm) and CO (Carbon Monoxide) model shows a good agreement with SMOCC/RaCCI data in the general pattern of temporal evolution. The results showed high correlations, with values between 0.80 and 0.95 (significant at 0.5 level by student t test), for the CATT-BRAMS simulations with PM 2.5μm and CO.

  20. Characteristics and direct radiative effect of mid-latitude continental aerosols: the ARM case

    Directory of Open Access Journals (Sweden)

    M. G. Iziomon

    2003-01-01

    Full Text Available A multi-year field measurement analysis of the characteristics and direct radiative effect of aerosols at the Southern Great Plains (SGP central facility of the Atmospheric Radiation Measurement (ARM Program is presented. Inter-annual mean and standard deviation of submicrometer scattering fraction (at 550 nm and Ångström exponent å (450 nm, 700 nm at the mid-latitude continental site are indicative of the scattering dominance of fine mode aerosol particles, being 0.84±0.03 and 2.25±0.09, respectively. We attribute the diurnal variation of submicron aerosol concentration to coagulation, photochemistry and the evolution of the boundary layer. Precipitation does not seem to play a role in the observed afternoon maximum in aerosol concentration. Submicron aerosol mass at the site peaks in the summer (12.1±6.7mg m-3, with the summer value being twice that in the winter. Of the chemically analyzed ionic components (which exclude carbonaceous aerosols, SO4= and NH4+ constitute the dominant species at the SGP seasonally, contributing 23-30% and 9-12% of the submicron aerosol mass, respectively. Although a minor species, there is a notable rise in NO3- mass fraction in winter. We contrast the optical properties of dust and smoke haze. The single scattering albedo w0 shows the most remarkable distinction between the two aerosol constituents. We also present aircraft measurements of vertical profiles of aerosol optical properties at the site. Annually, the lowest 1.2 km contributes 70% to the column total light scattering coefficient. Column-averaged and surface annual mean values of hemispheric backscatter fraction (at 550 nm, w0 (at 550 nm and å (450 nm, 700 nm agree to within 5% in 2001. Aerosols produce a net cooling (most pronounced in the spring at the ARM site

  1. Mobile Atmospheric Aerosol and Radiation Characterization Observatory (MAARCO)

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: MAARCO is designed as a stand-alone facility for basic atmospheric research and the collection of data to assist in validating aerosol and weather models....

  2. Inverse atmospheric radiative transfer problems - A nonlinear minimization search method of solution. [aerosol pollution monitoring

    Science.gov (United States)

    Fymat, A. L.

    1976-01-01

    The paper studies the inversion of the radiative transfer equation describing the interaction of electromagnetic radiation with atmospheric aerosols. The interaction can be considered as the propagation in the aerosol medium of two light beams: the direct beam in the line-of-sight attenuated by absorption and scattering, and the diffuse beam arising from scattering into the viewing direction, which propagates more or less in random fashion. The latter beam has single scattering and multiple scattering contributions. In the former case and for single scattering, the problem is reducible to first-kind Fredholm equations, while for multiple scattering it is necessary to invert partial integrodifferential equations. A nonlinear minimization search method, applicable to the solution of both types of problems has been developed, and is applied here to the problem of monitoring aerosol pollution, namely the complex refractive index and size distribution of aerosol particles.

  3. Radiative forcings for 28 potential Archean greenhouse gases

    Directory of Open Access Journals (Sweden)

    B. Byrne

    2014-05-01

    Full Text Available Despite reduced insolation in the late Archean, evidence suggests a warm climate which was likely sustained by a stronger greenhouse effect, the so-called Faint Young Sun Problem (FYSP. CO2 and CH4 are generally thought to be the mainstays of this enhanced greenhouse, though many other gases have been proposed. We present high accuracy radiative forcings for CO2, CH4 and 26 other gases, performing the radiative transfer calculations at line-by-line resolution and using HITRAN 2012 line data for background pressures of 0.5, 1, and 2 bar. For CO2 to resolve the FYSP alone, 0.21 bar is needed with 0.5 bar of atmospheric pressure, 0.13 bar with 1 bar of atmospheric pressures, or 0.07 bar with 2 bar of atmospheric pressure. For CH4, we find that near-infrared absorption is much stronger than previously thought, arising from updates to the HITRAN database. CH4 radiative forcing peaks at 10.3, 9, or 8.3 W m−2 for background pressures of 0.5, 1 or 2 bar, likely limiting the utility of CH4 for warming the Archean. For the other 26 HITRAN gases, radiative forcings of up to a few to 10 W m−2 are obtained from concentrations of 0.1–1 ppmv for many gases. We further calculate the reduction of radiative forcing due to gas overlap for the 20 strongest gases. We recommend the forcings provided here be used both as a first reference for which gases are likely good greenhouse gases, and as a standard set of calculations for validation of radiative forcing calculations for the Archean.

  4. Modulation of ultrasound to produce multifrequency radiation force1

    OpenAIRE

    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...

  5. Radiation reaction force and unification of electromagnetic and gravitational fields

    International Nuclear Information System (INIS)

    A unified theory of electromagnetic and gravitational fields should modify classical electrodynamics such that the radiation reaction force is accounted for. The analysis leads to a five-dimensional unified theory of five variables. The theory is supported by showing that, for the case of a charged particle moving in a constant magnetic field, the radiation reaction force is indeed included. Moreover, this example shows explicitly that physical changes are associated with the fifth variable. Thus, the notion of a physical five-dimensional space should be seriously taken into consideration

  6. Absorbing aerosol radiative effects in the limb-scatter viewing geometry

    Directory of Open Access Journals (Sweden)

    A. Wiacek

    2013-02-01

    Full Text Available The limb-scatter satellite viewing geometry is well suited to detecting low-concentration aerosols in the upper troposphere due to its long observation path length (~ 50–100 km, high vertical resolution (~ 1–2 km and good geographic coverage. We use the fully three-dimensional radiative transfer code SASKTRAN to simulate the sensitivity of limb-scatter viewing Odin/OSIRIS satellite measurements to absorbing mineral dust and carbonaceous aerosols (smoke and pure soot, as well as to non-absorbing sulfate aerosols and ice in the upper troposphere.

    At long wavelengths (813 nm the addition of all aerosols (except soot to an air only atmosphere produced a radiance increase as compared to air only, on account of the low Rayleigh scattering in air only at 813 nm. The radiance reduction due to soot aerosol was negligible (< 0.1% at all heights (0–100 km.

    At short wavelengths (337, 377, 452 nm, we found that the addition of any aerosol species to an air only atmosphere caused a decrease in single-scattered radiation due to an extinction of Rayleigh scattering in the direction of OSIRIS. The reduction was clearly related to particle size first, with absorption responsible for second-order effects only. Multiple-scattered radiation could either increase or decrease in the presence of an aerosol species, depending both on particle size and absorption. Large scatterers (ice, mineral dust all increased multiple-scattered radiation within, below and above the aerosol layer. Small, highly absorbing pure soot particles produced a negligible multiple-scattering response (< 0.1% at all heights, primarily confined to within and below the soot layer. Medium-sized scatterers produced a multiple-scattering response that depended on their absorbing properties. Increased radiances were simulated as compared to air only at all short wavelengths (337, 377 and 452 nm for sulfate aerosol particles (non-absorbing while decreased radiances were

  7. Secondary organic aerosols: Formation potential and ambient data

    DEFF Research Database (Denmark)

    Barthelmie, R.J.; Pryor, S.C.

    1997-01-01

    Organic aerosols comprise a significant fraction of the total atmospheric particle loading and are associated with radiative forcing and health impacts. Ambient organic aerosol concentrations contain both a primary and secondary component. Herein, fractional aerosol coefficients (FAC) are used in...... conjunction with measurements of volatile organic compounds (VOC) to predict the formation potential of secondary organic aerosols (SOA) in the Lower Fraser Valley (LEV) of British Columbia. The predicted concentrations of SOA show reasonable accord with ambient aerosol measurements and indicate considerable...

  8. Radiative forcings for 28 potential Archean greenhouse gases

    OpenAIRE

    B. Byrne; Goldblatt, C.

    2014-01-01

    Despite reduced insolation in the late Archean, evidence suggests a~warm climate which was likely sustained by a stronger greenhouse effect, the so-called faint young sun problem (FYSP). CO2 and CH4 are generally thought to be the mainstays of this enhanced greenhouse, though many other gases have been proposed. We present high accuracy radiative forcings for CO2, CH4, and 26 other gases, performing the radiative transfer calculations at line-by-line resolution and using HIT...

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

    Directory of Open Access Journals (Sweden)

    T. Korhola

    2013-08-01

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

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

    Science.gov (United States)

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

    2016-03-01

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

  11. Aerosol Observing System (AOS) Handbook

    Energy Technology Data Exchange (ETDEWEB)

    Jefferson, A

    2011-01-17

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

  12. Implication of radiative forcing distribution for energy transport

    Science.gov (United States)

    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.

  13. Overview of the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES)

    Energy Technology Data Exchange (ETDEWEB)

    Zaveri, R. A.; Shaw, W. J.; Cziczo, D. J.; Schmid, B.; Ferrare, R. A.; Alexander, M. L.; Alexandrov, M.; Alvarez, R. J.; Arnott, W. P.; Atkinson, D. B.; Baidar, S.; Banta, R. M.; Barnard, J. C.; Beranek, J.; Berg, L. K.; Brechtel, F.; Brewer, W. A.; Cahill, J. F.; Cairns, B.; Cappa, C. D.; Chand, D.; China, S.; Comstock, J. M.; Dubey, M. K.; Easter, R. C.; Erickson, M. H.; Fast, J. D.; Floerchinger, C.; Flowers, B. A.; Fortner, E.; Gaffney, J. S.; Gilles, M. K.; Gorkowski, K.; Gustafson, W. I.; Gyawali, M.; Hair, J.; Hardesty, R. M.; Harworth, J. W.; Herndon, S.; Hiranuma, N.; Hostetler, C.; Hubbe, J. M.; Jayne, J. T.; Jeong, H.; Jobson, B. T.; Kassianov, E. I.; Kleinman, L. I.; Kluzek, C.; Knighton, B.; Kolesar, K. R.; Kuang, C.; Kubátová, A.; Langford, A. O.; Laskin, A.; Laulainen, N.; Marchbanks, R. D.; Mazzoleni, C.; Mei, F.; Moffet, R. C.; Nelson, D.; Obland, M. D.; Oetjen, H.; Onasch, T. B.; Ortega, I.; Ottaviani, M.; Pekour, M.; Prather, K. A.; Radney, J. G.; Rogers, R. R.; Sandberg, S. P.; Sedlacek, A.; Senff, C. J.; Senum, G.; Setyan, A.; Shilling, J. E.; Shrivastava, M.; Song, C.; Springston, S. R.; Subramanian, R.; Suski, K.; Tomlinson, J.; Volkamer, R.; Wallace, H. W.; Wang, J.; Weickmann, A. M.; Worsnop, D. R.; Yu, X. -Y.; Zelenyuk, A.; Zhang, Q.

    2012-01-01

    Substantial uncertainties still exist in the scientific understanding of the possible interactions between urban and natural (biogenic) emissions in the production and transformation of atmospheric aerosol and the resulting impact on climate change. The U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program’s Carbonaceous Aerosol and Radiative Effects Study (CARES) carried out in June 2010 in Central Valley, California, was a comprehensive effort designed to improve this understanding. The primary objective of the field study was to investigate the evolution of secondary organic and black carbon aerosols and their climate-related properties in the Sacramento urban plume as it was routinely transported into the forested Sierra Nevada foothills area. Urban aerosols and trace gases experienced significant physical and chemical transformations as they mixed with the reactive biogenic hydrocarbons emitted from the forest. Two heavily-instrumented ground sites – one within the Sacramento urban area and another about 40 km to the northeast in the foothills area – were set up to characterize the evolution of meteorological variables, trace gases, aerosol precursors, aerosol size, composition, and climate-related properties in freshly polluted and “aged” urban air. On selected days, the DOE G-1 aircraft was deployed to make similar measurements upwind and across the evolving Sacramento plume in the morning and again in the afternoon. The NASA B-200 aircraft, carrying remote sensing instruments, was also deployed to characterize the vertical and horizontal distribution of aerosols and aerosol optical properties within and around the plume. This overview provides: a) the scientific background and motivation for the study, b) the operational and logistical information pertinent to the execution of the study, c) an overview of key observations and initial findings from the aircraft and ground-based sampling platforms, and d) a roadmap of

  14. A steady-state analysis of the temperature responses of water vapor and aerosol lifetimes

    NARCIS (Netherlands)

    Roelofs, G.J.H.

    2013-01-01

    The dominant removal mechanism of soluble aerosol is wet deposition. The atmospheric lifetime of aerosol, relevant for aerosol radiative forcing, is therefore coupled to the atmospheric cycling time of water vapor. This study investigates the coupling between water vapor and aerosol lifetimes in a w

  15. Characterization and radiative impact of dust aerosols over northwestern part of India: a case study during a severe dust storm

    Science.gov (United States)

    Singh, Atinderpal; Tiwari, Shani; Sharma, Deepti; Singh, Darshan; Tiwari, Suresh; Srivastava, Atul Kumar; Rastogi, Neeraj; Singh, A. K.

    2016-03-01

    The present study focused on examining the impact of a severe dust storm (DS) on aerosol properties over Patiala (30.33°N, 76.4°E), a site located in the northwestern part of India during 20th-23rd March, 2012. On 20th March, average PM10 mass concentration increased abruptly from 182 to 817 µg m-3 along with significant increase in the number density of coarser particles (diameter >0.45 µm). During DS, spectral aerosol optical depth (AOD) increases significantly with more increase at longer wavelengths resulting in weak wavelength dependence (AOD at 380 nm increases by ~210 % and at 870 nm by ~270 % on 20th March). Significant decrease in Ångström exponent (AE; α 380-870) from 0.56 to 0.11 and fine-mode fraction (FMF; PM2.5/PM10) from 0.49 to 0.25 indicates dominance of coarser particles over the station. Net short wave (SW) radiation flux has been decreased by ~20 % and single scattering albedo (SSA675) has been increased from 0.86 (19th March) to 0.90 (20th March). This observation is attributed to additional loading of scattering type aerosols on arrival of DS. Wavelength dependence of SSA reverses during DS and it increases with wavelength due to dominance of coarse-mode particles. Atmospheric aerosol radiative forcing (ATM ARF) during DS ranged from +45 to +77 W m-2, consequently heating the lower atmosphere up to 2.2 K day-1. Significant atmospheric heating rate due to severe dust storm may affect the regional atmospheric dynamics and hence the climate system.

  16. Evaluating aerosol indirect effect through marine stratocumulus clouds

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-04-01

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

  17. Assessment of the impact of the greenhouse gas emission and sink scenarios in Finland on radiative forcing and greenhouse effect

    Energy Technology Data Exchange (ETDEWEB)

    Savolainen, I.; Sinisalo, J.; Pipatti, R. [Technical Research Centre of Finland, Espoo (Finland)

    1996-12-31

    The objective of this work is to study greenhouse gas emissions and sinks and their greenhouse impact as a function of time. The greenhouse impact is expressed in terms of global average radiative forcing, which measures the perturbation in the Earth`s radiation budget. Radiative forcing is calculated on the basis of the concentration changes of the greenhouse gases and the radiation absorption properties of the gases. It takes into account the relatively slow changes in the concentrations due to natural removal and transformation processes and also allows a comparison of the impact of various greenhouse gases and their possible control options as a function of time. In addition to the applications mentioned above, the anthropogenic greenhouse gas emission histories of Nordic countries have been estimated, and the radiative forcing caused by them has been calculated with REFUGE. The dynamic impact of aerosol emissions both from the global point of view and in the context of different energy sources (coal, oil and natural gas) have also been studied. In some instances the caused radiative forcing has been examined on a per capita basis. The radiative forcing calculations contain considerable uncertainty due to inaccurately known factors at several stages of the calculation (emission estimation, concentration calculation and radiative forcing calculation). The total uncertainty of the results is typically on the order of +- 40 %, when absolute values are used. If the results are used in a relative way, e.g. to compare the impacts of different scenarios, the final uncertainty is considerably less (typically + 10 %), due to correlations in almost all stages of the calculation process

  18. Interpreting the Ultraviolet Aerosol Index Observed with the OMI Satellite Instrument to Understand Absorption by Organic Aerosols: Implications for Atmospheric Oxidation and Direct Radiative Effects

    Science.gov (United States)

    Hammer, Melanie S.; Buchard, Virginie; Ridley, David A.; Spurr, Robert J. D.; Martin, Randall V.; Donkelaar, Aaron van; Torres, Omar

    2016-01-01

    Satellite observations of the ultraviolet aerosol index (UVAI) are sensitive to absorption of solar radiation by aerosols; this absorption affects photolysis frequencies and radiative forcing. We develop a global simulation of the UVAI using the 3-D chemical transport model GEOSChem coupled with the Vector Linearized Discrete Ordinate Radiative Transfer model (VLIDORT). The simulation is applied to interpret UVAI observations from the Ozone Monitoring Instrument (OMI) for the year 2007. Simulated and observed values are highly consistent in regions where mineral dust dominates the UVAI, but a large negative bias (-0.32 to -0.97) exists between simulated and observed values in biomass burning regions. We determine effective optical properties for absorbing organic aerosol, known as brown carbon (BrC), and implement them into GEOS-Chem to better represent observed UVAI values over biomass burning regions. The inclusion of absorbing BrC decreases the mean bias between simulated and OMI UVAI values from -0.57 to -0.09 over West Africa in January, from -0.32 to +0.0002 over South Asia in April, from -0.97 to -0.22 over southern Africa in July, and from -0.50 to +0.33 over South America in September. The spectral dependence of absorption after including BrC in the model is broadly consistent with reported observations for biomass burning aerosol, with absorbing Angstrom exponent (AAE) values ranging from 2.9 in the ultraviolet (UV) to 1.3 across the UV-Near IR spectrum. We assess the effect of the additional UV absorption by BrC on atmospheric photochemistry by examining tropospheric hydroxyl radical (OH) concentrations in GEOS-Chem. The inclusion of BrC decreases OH by up to 30% over South America in September, up to 20% over southern Africa in July, and up to 15% over other biomass burning regions. Global annual mean OH concentrations in GEOS-Chem decrease due to the presence of absorbing BrC, increasing the methyl chloroform lifetime from 5.62 to 5.68 years, thus

  19. Interpreting the Ultraviolet Aerosol Index observed with the OMI satellite instrument to understand absorption by organic aerosols: implications for atmospheric oxidation and direct radiative effects

    Directory of Open Access Journals (Sweden)

    M. S. Hammer

    2015-10-01

    Full Text Available Satellite observations of the Ultraviolet Aerosol Index (UVAI are sensitive to absorption of solar radiation by aerosols; this absorption affects photolysis frequencies and radiative forcing. We develop a global simulation of the UVAI using the 3-D chemical transport model GEOS-Chem coupled with the Vector Linearized Discrete Ordinate Radiative Transfer model (VLIDORT. The simulation is applied to interpret UVAI observations from the Ozone Monitoring Instrument (OMI for the year 2007. Simulated and observed values are highly consistent in regions where mineral dust dominates the UVAI, but a large negative bias (−0.32 to −0.97 exists between simulated and observed values in biomass burning regions. We determine effective optical properties for absorbing organic aerosol, known as brown carbon (BrC, and implement them into GEOS-Chem to better represent observed UVAI values over biomass burning regions. The addition of absorbing BrC decreases the mean bias between simulated and OMI UVAI values from −0.57 to −0.09 over West Africa in January, from −0.32 to +0.0002 over South Asia in April, from −0.97 to −0.22 over southern Africa in July, and from −0.50 to +0.33 over South America in September. The spectral dependence of absorption after adding BrC to the model is broadly consistent with reported observations for biomass burning aerosol, with Absorbing Angstrom Exponent (AAE values ranging from 2.9 in the ultraviolet (UV to 1.3 across the UV-Near IR spectrum. We assess the effect of the additional UV absorption by BrC on atmospheric photochemistry by examining tropospheric hydroxyl radical (OH concentrations in GEOS-Chem. The inclusion of BrC decreases OH by up to 35 % over South America in September, up to 25 % over southern Africa in July, and up to 20 % over other biomass burning regions. Global annual mean OH concentrations in GEOS-Chem decrease due to the presence of absorbing BrC, increasing the methyl chloroform lifetime from 5

  20. The initial dispersal and radiative forcing of a Northern Hemisphere mid-latitude super volcano: a model study

    Directory of Open Access Journals (Sweden)

    C. Timmreck

    2006-01-01

    Full Text Available The chemistry climate model MAECHAM4/ CHEM with interactive and prognostic volcanic aerosol and ozone was used to study the initial dispersal and radiative forcing of a possible Northern Hemisphere mid-latitude super eruption. Tropospheric climate anomalies are not analysed since sea surface temperatures are kept fixed. Our experiments show that the global dispersal of a super eruption located at Yellowstone, Wy. is strongly dependent on the season of the eruption. In Northern Hemisphere summer the volcanic cloud is transported westward and preferentially southward, while in Northern Hemisphere winter the cloud is transported eastward and more northward compared to the summer case. Aerosol induced heating leads to a more global spreading with a pronounced cross equatorial transport. For a summer eruption aerosol is transported much further to the Southern Hemisphere than for a winter eruption. In contrast to Pinatubo case studies, strong cooling tendencies appear with maximum peak values of less than −1.6 K/day three months after the eruption in the upper tropical stratosphere. This strong cooling effect weakens with decreasing aerosol density over time and initially prevents the aerosol laden air from further active rising. All-sky net radiative flux changes of less than −32 W/m2 at the surface are about a factor of 6 larger than for the Pinatubo eruption. Large positive flux anomalies of more than 16 W/m2 are found in the first months in the tropics and sub tropics. These strong forcings call for a fully coupled ocean/atmosphere/chemistry model to study climate sensitivity to such a super-eruption.

  1. Sensitivity of clear-sky direct radiative effect of the aerosol to micro-physical properties by using 6SV radiative transfer model: preliminary results

    Science.gov (United States)

    Bassani, Cristiana; Tirelli, Cecilia; Manzo, Ciro; Pietrodangelo, Adriana; Curci, Gabriele

    2015-04-01

    The aerosol micro-physical properties are crucial to analyze their radiative impact on the Earth's radiation budget [IPCC, 2007]. The 6SV model, last generation of the Second Simulation of a Satellite Signal in the Solar Spectrum (6S) radiative transfer code [Kotchenova et al., 2007; Vermote et al., 1997] has been used to perform physically-based atmospheric correction of hyperspectral airborne and aircraft remote sensing data [Vermote et al., 2009; Bassani et al. 2010; Tirelli et al., 2014]. The atmospheric correction of hyperspectral data has been shown to be sensitive to the aerosol micro-physical properties, as reported in Bassani et al., 2012. The role of the aerosol micro-physical properties on the accuracy of the atmospheric correction of hyperspectral data acquired over water and land targets is investigated within the framework of CLAM-PHYM (Coasts and Lake Assessment and Monitoring by PRISMA HYperspectral Mission) and PRIMES (Synergistic use of PRISMA products with high resolution meteo-chemical simulations and their validation on ground and from satellite) projects, both funded by Italian Space Agency (ASI). In this work, the results of the radiative field of the Earth/Atmosphere coupled system simulated by using 6SV during the atmospheric correction of hyperspectral data are presented. The analysis of the clear-sky direct radiative effect is performed considering the aerosol micro-physical properties used to define the aerosol model during the atmospheric correction process. In particular, the AERONET [Holben et al., 1998] and FLEXAOD [Curci et al., 2014] micro-physical properties are used for each image to evaluate the contribution of the size distribution and refractive index of the aerosol type on the surface reflectance and on the direct radiative forcing. The results highlight the potential of the hyperspectral remote sensing data for atmospheric studies as well as for environmental studies. Currently, the future hyperspectral missions, such as the

  2. Role of anthropogenic aerosols in the20th century surface solar radiation, temperature, and meridional heat transport in the Max Planck Earth System Model

    Science.gov (United States)

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

    2016-04-01

    It is still debated, to what degree anthropogenic aerosols were affected surface temperatures - especially over sea surfaces - through alteration of surface solar radiation (SSR). Previous work using mixed-layer ocean equilibria corroborated the relevance of anthropogenic aerosols for surface temperature response patterns obtained. Here we complement these studies by fully coupled simulations with the Max Planck Earth System Model (MPI-ESM) in its CMIP5 version. Experiments comprise preindustrial control and historical as in CMIP5, as well as transient experiments 1850 - 2000 with either anthropogenic aerosols or well-mixed greenhouse gases (WMGHG) kept at 1850 levels. With this suite of experiments, we analyse the impact of anthropogenic aerosols and WMGHG on the global energy balance and provide estimates of atmospheric and oceanic meridional heat transport changes in our modeling setup. We find that Global mean surface temperature responses to single forcings are additive. Furthermore, spatial surface temperature response patterns in the WMGHG only experiment are more strongly correlated with the historical experiment than the aerosol only case. We compare transient and equilibrium responses and discuss potential implications of not allowing for cloud-aerosol interactions in the transient modeling set-up.

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

    International Nuclear Information System (INIS)

    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

  4. Mixing states of aerosols over four environmentally distinct atmospheric regimes in Asia: coastal, urban, and industrial locations influenced by dust.

    Science.gov (United States)

    Ramachandran, S; Srivastava, Rohit

    2016-06-01

    Mixing can influence the optical, physical, and chemical characteristics of aerosols, which in turn can modify their life cycle and radiative effects. Assumptions on the mixing state can lead to uncertain estimates of aerosol radiative effects. To examine the effect of mixing on the aerosol characteristics, and their influence on radiative effects, aerosol mixing states are determined over four environmentally distinct locations (Karachi, Gwangju, Osaka, and Singapore) in Asia, an aerosol hot spot region, using measured spectral aerosol optical properties and optical properties model. Aerosol optical depth (AOD), single scattering albedo (SSA), and asymmetry parameter (g) exhibit spectral, spatial, and temporal variations. Aerosol mixing states exhibit large spatial and temporal variations consistent with aerosol characteristics and aerosol type over each location. External mixing of aerosol species is unable to reproduce measured SSA over Asia, thus providing a strong evidence that aerosols exist in mixed state. Mineral dust (MD) (core)-Black carbon (BC) (shell) is one of the most preferred aerosol mixing states. Over locations influenced by biomass burning aerosols, BC (core)-water soluble (WS, shell) is a preferred mixing state, while dust gets coated by anthropogenic aerosols (BC, WS) over urban regions influenced by dust. MD (core)-sea salt (shell) mixing is found over Gwangju corroborating the observations. Aerosol radiative forcing exhibits large seasonal and spatial variations consistent with features seen in aerosol optical properties and mixing states. TOA forcing is less negative/positive for external mixing scenario because of lower SSA. Aerosol radiative forcing in Karachi is a factor of 2 higher when compared to Gwangju, Osaka, and Singapore. The influence of g on aerosol radiative forcing is insignificant. Results emphasize that rather than prescribing one single aerosol mixing state in global climate models regionally and temporally varying aerosol

  5. Modelled Black Carbon Radiative Forcing and Atmospheric Lifetime in AeroCom Phase II Constrained by Aircraft Observations

    Energy Technology Data Exchange (ETDEWEB)

    Samset, B. H.; Myhre, G.; Herber, Andreas; Kondo, Yutaka; Li, Shao-Meng; Moteki, N.; Koike, Makoto; Oshima, N.; Schwarz, Joshua P.; Balkanski, Y.; Bauer, S.; Bellouin, N.; Berntsen, T.; Bian, Huisheng; Chin, M.; Diehl, Thomas; Easter, Richard C.; Ghan, Steven J.; Iversen, T.; Kirkevag, A.; Lamarque, Jean-Francois; Lin, Guang; Liu, Xiaohong; Penner, Joyce E.; Schulz, M.; Seland, O.; Skeie, R. B.; Stier, P.; Takemura, T.; Tsigaridis, Kostas; Zhang, Kai

    2014-11-27

    Black carbon (BC) aerosols absorb solar radiation, and are generally held to exacerbate global warming through exerting a positive radiative forcing1. However, the total contribution of BC to the ongoing changes in global climate is presently under debate2-8. Both anthropogenic BC emissions and the resulting spatial and temporal distribution of BC concentration are highly uncertain2,9. In particular, long range transport and processes affecting BC atmospheric lifetime are poorly understood, leading to large estimated uncertainty in BC concentration at high altitudes and far from emission sources10. These uncertainties limit our ability to quantify both the historical, present and future anthropogenic climate impact of BC. Here we compare vertical profiles of BC concentration from four recent aircraft measurement campaigns with 13 state of the art aerosol models, and show that recent assessments may have overestimated present day BC radiative forcing. Further, an atmospheric lifetime of BC of less than 5 days is shown to be essential for reproducing observations in transport dominated remote regions. Adjusting model results to measurements in remote regions, and at high altitudes, leads to a 25% reduction in the multi-model median direct BC forcing from fossil fuel and biofuel burning over the industrial era.

  6. Effects of model resolution on entrainment (inversion heights), cloud-radiation interactions, and cloud radiative forcing

    OpenAIRE

    H. Guo; Y. LIU; P. H. Daum; Zeng, X.; Li, X.; Tao, W.-K.

    2008-01-01

    We undertook three-dimensional numerical studies of a marine stratus deck under a strong inversion using an interactive shortwave- and longwave-radiation module. A suite of sensitivity tests were conducted to address the effects of model resolution on entrainment (inversion heights), cloud-radiation interactions, and cloud radiative-forcings by varying model horizontal resolution only, varying vertical resolution only, and varying horizontal- and vertical-resolution simultan...

  7. Optical properties and radiative forcing of the Eyjafjallajökull volcanic ash layer observed over Lille, France, in 2010

    Science.gov (United States)

    Derimian, Y.; Dubovik, O.; Tanre, D.; Goloub, P.; Lapyonok, T.; Mortier, A.

    2012-10-01

    In this work we characterize optical properties and assess the direct radiative effect of an ash plume observed on April 17, 2010 by AERONET, lidar and broadband solar flux measurements collocated on the roof of the Laboratory of Atmospheric Optics in Lille, northern France. These measurements allowed experimental evaluation of ash radiative impact and validation of simulations. The derived aerosol model of ash is characterized by a bi-modal size distribution dominated by coarse mode centered at a radius of 1.5 μm and by relatively strong absorption at short wavelengths (single scattering albedo of 0.81 ± 0.02 at 440 nm as opposed to 0.92 ± 0.02 at 670, 870 and 1020 nm). Due to relatively low aerosol optical thickness during the ash plume transport (˜0.26 at 440 nm), which is unfavorable for AERONET retrievals, the uncertainties in derived ash aerosol model were additionally evaluated. The complex refractive index of ash was derived assuming that effective refractive index retrieved by AERONET for externally mixed bi-component aerosol can be approximated as an average of refractive indices of two components weighted by their volume concentrations. Evaluation of the accuracy of this approximation showed acceptably small errors in simulations of single scattering albedo and aerosol phase function over the range of scattering angles observed by the AERONET almucantar. Daily average radiative forcing efficiency of ash calculated for a land surface reflectance representing Lille was about -93 ± 12 Wm-2 τ550-1 and -31 ± 2 Wm-2 τ550-1 at the bottom and top of the atmosphere; the values for an ocean surface reflectance are also provided.

  8. Warming-induced increase in aerosol number concentration likely to moderate climate change

    NARCIS (Netherlands)

    Paasonen, P.; Asmi, A.; Petäjä, T.; Kajos, M.K.; Äijälä, M.; Junninen, H.; Holst, T.; Abbatt, J.P.D.; Arneth, A.; Birmili, W.; Denier van der Gon, H.A.C.; Hamed, A.; Hoffer, A.; Laakso, L.; Laaksonen, A.; Richard Leaitch, W.; Plass-Dülmer, C.; Pryor, S.C.; Räisänen, P.; Swietlicki, E.; Wiedensohler, A.; Worsnop, D.R.; Kerminen, V.-M.; Kulmala, M.

    2013-01-01

    Atmospheric aerosol particles influence the climate system directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. Apart from black carbon aerosol, aerosols cause a negative radiative forcing at the top of the atmosphere and substantially mitigate

  9. Radiative forcings for 28 potential Archean greenhouse gases

    OpenAIRE

    B. Byrne; Goldblatt, C.

    2014-01-01

    Despite reduced insolation in the late Archean, evidence suggests a warm climate which was likely sustained by a stronger greenhouse effect, the so-called Faint Young Sun Problem (FYSP). CO2 and CH4 are generally thought to be the mainstays of this enhanced greenhouse, though many other gases have been proposed. We present high accuracy radiative forcings for CO2, CH4 and 26 other gases, performing the radiative transfer calculations at line-by-line resolution and using HITRAN 2012 line data ...

  10. Cooling and trapping neutral atoms with radiative forces

    International Nuclear Information System (INIS)

    Techniques to slow and trap neutral atoms at high densities with radiative forces are discussed in this review articles. Among several methods of laser cooling, it is emphasized Zeeman Tuning of the electronic levels and frequency-sweeping techniques. Trapping of neutral atoms and recent results obtained in light and magnetic traps are discussed. Techniques to further cool atoms inside traps are presented and the future of laser cooling of neutral atoms by means of radiation pressure is discussed. (A.C.A.S.)

  11. The radiative effect of aerosols from biomass burning on the transition from dry to wet season over the Amazon as tested by a regional climate model

    Science.gov (United States)

    Zhang, Yan

    2008-10-01

    I have carried out a set of ensemble simulations of a regional climate model with observed radiative forcing for smoke aerosols over the Amazon to investigate the radiative effects of aerosols on clouds, rainfall, and circulation from dry to wet season. I first modified the land surface scheme such that the modeled daily mean and diurnal cycle of the surface sensible and latent heat fluxes are much more realistic over the Amazon rainforest. The results of the ensemble simulations suggest that the radiative effect of the smoke aerosols can reduce daytime surface radiative and sensible fluxes, the depth and instability of the planetary boundary layer (PBL), consequently the clouds in the lower troposphere in early afternoon in the smoke center, where the aerosols optical depth, AOD, exceeds 0.3. The aerosol radiative forcing also appears to weaken moisture transport into the smoke center and increase moisture transport and cloudiness in the region upwind to the smoke center, namely, the northern Amazon. In particular, the absorption of solar radiation by smoke aerosols reduces cloudiness in early afternoon. This reduction of cloud partially compensates for the reduction of surface solar flux by aerosol scattering, shifting the strongest changes of surface flux and the PBL to late morning. The reduction of net solar radiation at the surface by smoke is locally largely compensated by reduction of surface sensible flux; with reduction of latent flux only about 30% as large. This is because, in model, transpiration of the forest canopy response favorably to the reduced leaf temperature by aerosols at local noon, which compensates the reduction of evapotranspiration (ET) in morning and later afternoon. Strong aerosol absorption in the top 1 km of the aerosol layer stabilizes the 2 to 3 km layer immediately above the daytime PBL and consequently cloudiness decreases. This reduced surface solar flux and more stable lapse rate at the top of the PBL stabilize the lower

  12. Analysis of the effects of aerosol distribution in the atmosphere on surface radiative measurements

    International Nuclear Information System (INIS)

    The distribution of atmospheric aerosols in the atmosphere may have important effects on the radiative properties of the atmosphere and thereby on the climate. The Atmospheric and Geophysical Sciences Division of the Lawrence Livermore National Laboratory is working with the Atmospheric Radiation Measurements (ARM) program to advise the program as to the importance of aerosols to the ARM measurement plan. The ARM Program had established a set of goals which highlight the important areas of scientific needs associated with the understanding and prediction of global climate change. This report summarizes the initial studies performed to assess the importance and effects of atmospheric aerosols<