Science.gov

Sample records for aerosol radiative effect

  1. Radiative Effects of Aerosols

    NASA Technical Reports Server (NTRS)

    Valero, Francisco P. J.

    1997-01-01

    During the Atlantic Stratocumulus Transition Experiment (ASTEX) in June 1992, two descents in cloud-free regions allowed comparison of the change in aerosol optical depth as determined by an onboard total-direct-diffuse radiometer (TDDR) to the change calculated from measured size resolved aerosol microphysics and chemistry. Both profiles included pollution haze layer from Europe but the second also included the effect of a Saharan dust layer above the haze. The separate contributions of supermicrometer (coarse) and submicrometer (fine) aerosol were determined and thermal analysis of the pollution haze indicated that the fine aerosol was composed primarily of a sulfate/water mixture with a refractory soot-like core.

  2. Radiative Effects of Aerosols

    NASA Technical Reports Server (NTRS)

    Valero, Francisco P. J.

    1996-01-01

    During the Atlantic Stratocumulus Transition Experiment (ASTEX) in June 1992, two descents in cloud-free regions allowed comparison of the change in aerosol optical depth as determined by an onboard total-direct-diffuse radiometer (TDDR) to the change calculated from measured size-resolved aerosol microphysics and chemistry. Both profiles included a pollution haze from Europe but the second also included the effect of a Saharan dust layer above the haze. The separate contributions of supermicrometer (coarse) and submicrometer (fine) aerosol were determined and thermal analysis of the pollution haze indicated that the fine aerosol was composed primarily of a sulfate/water mixture with a refractory soot-like core. The soot core increased the calculated extinction by about 10% in the most polluted drier layer relative to a pure sulfate aerosol but had significantly less effect at higher humidities. A 3 km descent through a boundary layer air mass dominated by pollutant aerosol with relative humidities (RH) 10-77% yielded a close agreement between the measured and calculated aerosol optical depths (550 nm) of 0.160 (+/- 0.07) and 0. 157 (+/- 0.034) respectively. During descent the aerosol mass scattering coefficient per unit sulfate mass varied from about 5 to 16 m(exp 2)/g and primarily dependent upon ambient RH. However, the total scattering coefficient per total fine mass was far less variable at about 4+/- 0.7 m(exp 2)/g. A subsequent descent through a Saharan dust layer located above the pollution aerosol layer revealed that both layers contributed similarly to aerosol optical depth. The scattering per unit mass of the coarse aged dust was estimated at 1.1 +/- 0.2 m(exp 2)/g. The large difference (50%) in measured and calculated optical depth for the dust layer exceeded measurements.

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

    SciTech Connect

    Ghan, Steven J.

    2013-10-09

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

  4. Aerosol radiative effects over BIMSTEC regions

    NASA Astrophysics Data System (ADS)

    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. CARES: Carbonaceous Aerosol and Radiative Effects Study Science Plan

    SciTech Connect

    Zaveri, RA; Shaw, WJ; Cziczo, DJ

    2010-05-27

    Carbonaceous aerosol components, which include black carbon (BC), urban primary organic aerosols (POA), biomass burning aerosols, and secondary organic aerosols (SOA) from both urban and biogenic precursors, have been previously shown to play a major role in the direct and indirect radiative forcing of climate. The primary objective of the CARES 2010 intensive field study is to investigate the evolution of carbonaceous aerosols of different types and their effects on optical and cloud formation properties.

  6. Stratospheric aerosol properties and their effects on infrared radiation.

    NASA Technical Reports Server (NTRS)

    Remsberg, E. E.

    1973-01-01

    This paper presents a stratospheric aerosol model and infers its effects on terrestrial radiation. Composition of the aerosol is assumed to be concentrated sulfuric acid. An appropriate size distribution has been determined from available size distribution measurements of other investigators. Aerosols composed of concentrated sulfuric acid emit energy in the atmospheric window region of the infrared spectrum, 8-13 microns. Laboratory measurements of optical constant data obtained at room temperature are presented for 75 and 90% aqueous sulfuric acid. Calculations of an aerosol extinction coefficient are then performed by using the above data. Effects of changes in aerosol phase and temperature are discussed but not resolved.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    SciTech Connect

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

    2009-09-25

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

  9. Direct radiative effect by multicomponent aerosol over China

    SciTech Connect

    Huang, Xin; Song, Yu; Zhao, Chun; Cai, Xuhui; Zhang, Hongsheng; Zhu, Tong

    2015-05-01

    The direct radiative effect (DRE) of multiple aerosol species (sulfate, nitrate, ammonium, black carbon (BC), organic carbon (OC), and mineral aerosol) and their spatiotemporal variations over China were investigated using a fully coupled meteorology–chemistry model (WRF-Chem) for the entire year of 2006. We made modifications to improve model performance, including updating land surface parameters, improving the calculation of transition metal-catalyzed oxidation of SO2, and adding in heterogeneous reactions between mineral aerosol and acid gases. The modified model well reproduced the magnitude, seasonal pattern, and spatial distribution of the measured meteorological conditions, concentrations of PM10 and its components, and aerosol optical depth (AOD). A diagnostic iteration method was used to estimate the overall DRE of aerosols and contributions from different components. At the land surface, all kinds of aerosol species reduced the incident net radiation flux with a total DRE of 10.2 W m-2 over China. Aerosols significantly warm the atmosphere with the national mean DRE of +10.8 W m-2. BC was the leading radiative-heating component (+8.7 W m-2), followed by mineral aerosol (+1.1 W m-2). At the top of the atmosphere (TOA), BC introduced the largest radiative perturbation (+4.5 W m-2), followed by sulfate (-1.4 W m-2). The overall perturbation of aerosols on radiation transfer is quite small over China, demonstrating the counterbalancing effect between scattering and adsorbing aerosols. Aerosol DRE at the TOA had distinct seasonality, generally with a summer maximum and winter minimum, mainly determined by mass loadings, hygroscopic growth, and incident radiation flux.

  10. Modeling Trends in Tropospheric Aerosol Burden & Its Radiative Effects

    EPA Science Inventory

    Large changes in emissions of aerosol precursors have occurred across the southeast U.S., North America, as well as the northern hemisphere. The spatial heterogeneity and contrasting trends in the aerosol burden is resulting in differing effects on regional radiative balance. Mul...

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  13. Quantifying Aerosol influences on the Cloud Radiative Effect

    NASA Astrophysics Data System (ADS)

    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. Effect of aerosol vertical distribution on aerosol-radiation interaction: A theoretical prospect.

    PubMed

    Mishra, Amit Kumar; Koren, Ilan; Rudich, Yinon

    2015-10-01

    This study presents a theoretical investigation of the effect of the aerosol vertical distribution on the aerosol radiative effect (ARE). Four aerosol composition models (dust, polluted dust, pollution and pure scattering aerosols) with varying aerosol vertical profiles are incorporated into a radiative transfer model. The simulations show interesting spectral dependence of the ARE on the aerosol layer height. ARE increases with the aerosol layer height in the ultraviolet (UV: 0.25-0.42 μm) and thermal-infrared (TH-IR: 4.0-20.0 μm) regions, whereas it decreases in the visible-near infrared (VIS-NIR: 0.42-4.0 μm) region. Changes in the ARE with aerosol layer height are associated with different dominant processes for each spectral region. The combination of molecular (Rayleigh) scattering and aerosol absorption is the key process in the UV region, whereas aerosol (Mie) scattering and atmospheric gaseous absorption are key players in the VIS-NIR region. The longwave emission fluxes are controlled by the environmental temperature at the aerosol layer level. ARE shows maximum sensitivity to the aerosol layer height in the TH-IR region, followed by the UV and VIS-NIR regions. These changes are significant even in relatively low aerosol loading cases (aerosol optical depth ∼0.2-0.3). Dust aerosols are the most sensitive to altitude followed by polluted dust and pollution in all three different wavelength regions. Differences in the sensitivity of the aerosol type are explained by the relative strength of their spectral absorption/scattering properties. The role of surface reflectivity on the overall altitude dependency is shown to be important in the VIS-NIR and UV regions, whereas it is insensitive in the TH-IR region. Our results indicate that the vertical distribution of water vapor with respect to the aerosol layer is an important factor in the ARE estimations. Therefore, improved estimations of the water vapor profiles are needed for the further reduction in

  15. Impacts of emission reductions on aerosol radiative effects

    NASA Astrophysics Data System (ADS)

    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.

  16. Impacts of emission reductions on aerosol radiative effects

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The global aerosol-climate model ECHAM-HAMMOZ is used to study the aerosol burden and forcing changes in the coming decades. Four different emissions scenarios are applied for 2030 (two of them applied also for 2020) and the results are compared against 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 last one is targeted to short-lived climate forcers (SLCFs). We have analysed the results in terms of global means and additionally focused on 8 sub-regions. Based on our results, aerosol burdens overall show decreasing trend, but in some locations, such as India, the burdens could increase significantly. This has impact on the direct aerosol effect (DRE), which could reduce globally 0.06-0.4 W m-2 by 2030, but can increase over India (up to 0.84 W m-2). The global values depend on the scenario and are lowest with the targeted SLCF simulation. The cloud radiative effect could decline 0.25-0.82 W m-2 by 2030 and occurs mostly over oceans, whereas the DRE effect is mostly over land. 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.

  17. Analysis of Atmospheric Aerosol Data Sets and Application of Radiative Transfer Models to Compute Aerosol Effects

    NASA Technical Reports Server (NTRS)

    Schmid, Beat; Bergstrom, Robert W.; Redemann, Jens

    2002-01-01

    This report is the final report for "Analysis of Atmospheric Aerosol Data Sets and Application of Radiative Transfer Models to Compute Aerosol Effects". It is a bibliographic compilation of 29 peer-reviewed publications (published, in press or submitted) produced under this Cooperative Agreement and 30 first-authored conference presentations. The tasks outlined in the various proposals are listed below with a brief comment as to the research performed. Copies of title/abstract pages of peer-reviewed publications are attached.

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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. Radiative effects of aerosols on the environment in China

    NASA Astrophysics Data System (ADS)

    Yu, Hongbin

    Anthropogenic emissions and concentrations of aerosol precursors and aerosols over China are among the highest in major countries of the world. Due to large emissions of soot and dust, aerosol absorption is high. Based on the observed direct and diffuse irradiance, a single scattering albedo of about 0.8 is derived for two large agri/eco/industrial areas. Aerosol direct effect can exert various environmental impacts in China. Photochemical activities in the atmospheric boundary layer (ABL) are significantly reduced because of reductions in photolysis rates and in emissions of biogenic hydrocarbons. Crop yields under optimal conditions can be reduced due to the reduction in surface solar irradiance. The most significant aerosol radiative perturbation is in changing the air-surface interaction and diurnal evolution of ABL. Reductions in various surface heat fluxes due to aerosols depend on soil moisture. Over a relatively dry surface, the evaporation has a small change, leading to the largest decrease of surface skin temperature at noon. Over a relatively wet surface, a substantial reduction in evaporation results in the largest surface cooling in the early morning. The diurnal temperature range (DTR) can be reduced by an amount comparable to the observed decrease of DTR. The longwave absorption of aerosols can lead to an increase of the daily minimum temperature and contributes to about 20% of the decrease in the DTR. The near-surface air temperature has the largest cooling in the early morning because the ABL is shallow and the temperature is sensitive to the radiative perturbation. As a result of the reduced sensible heat flux, the surface layer becomes more stable. Moreover, the aerosol heating enhances the stabilization of surface layer and in turn further reduces the sensible heat flux. As a result the ABL height can be reduced substantially. This will have many important ramifications, including trapping/accumulation of air pollutants, and perturbing the water

  4. Volcanic Aerosol Radiative Properties

    NASA Technical Reports Server (NTRS)

    Lacis, Andrew

    2015-01-01

    Large sporadic volcanic eruptions inject large amounts of sulfur bearing gases into the stratosphere which then get photochemically converted to sulfuric acid aerosol droplets that exert a radiative cooling effect on the global climate system lasting for several years.

  5. Estimates of the Spectral Aerosol Single Sea Scattering Albedo and Aerosol Radiative Effects during SAFARI 2000

    NASA Technical Reports Server (NTRS)

    Bergstrom, Robert W.; Pilewskie, Peter; Schmid, Beat; Russell, Philip B.

    2003-01-01

    Using measurements of the spectral solar radiative flux and optical depth for 2 days (24 August and 6 September 2000) during the SAFARI 2000 intensive field experiment and a detailed radiative transfer model, we estimate the spectral single scattering albedo of the aerosol layer. The single scattering albedo is similar on the 2 days even though the optical depth for the aerosol layer was quite different. The aerosol single scattering albedo was between 0.85 and 0.90 at 350 nm, decreasing to 0.6 in the near infrared. The magnitude and decrease with wavelength of the single scattering albedo are consistent with the absorption properties of small black carbon particles. We estimate the uncertainty in the single scattering albedo due to the uncertainty in the measured fractional absorption and optical depths. The uncertainty in the single scattering albedo is significantly less on the high-optical-depth day (6 September) than on the low-optical-depth day (24 August). On the high-optical-depth day, the uncertainty in the single scattering albedo is 0.02 in the midvisible whereas on the low-optical-depth day the uncertainty is 0.08 in the midvisible. On both days, the uncertainty becomes larger in the near infrared. We compute the radiative effect of the aerosol by comparing calculations with and without the aerosol. The effect at the top of the atmosphere (TOA) is to cool the atmosphere by 13 W/sq m on 24 August and 17 W/sq m on 6 September. The effect on the downward flux at the surface is a reduction of 57 W/sq m on 24 August and 200 W/sq m on 6 September. The aerosol effect on the downward flux at the surface is in good agreement with the results reported from the Indian Ocean Experiment (INDOEX).

  6. SEAC4RS Aerosol Radiative Effects and Heating Rates

    NASA Astrophysics Data System (ADS)

    Cochrane, S.; Schmidt, S.; Redemann, J.; Hair, J. W.; Ferrare, R. A.; Segal-Rosenhaimer, M.; LeBlanc, S. E.

    2015-12-01

    We will present (a) aerosol optical properties, (b) aerosol radiative forcing, (c) aerosol and gas absorption and heating rates, and (d) spectral surface albedo for cases from August 19th and 26th of the SEAC4RS mission. This analysis is based on irradiance data from the Solar Spectral Flux Radiometer (SSFR), spectral aerosol optical depth from the Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR), and extinction profiles from the DIAL/High Spectral Resolution Lidar (HSRL). We derive spectrally resolved values of single scattering albedo, asymmetry parameter, and surface albedo from the data, and determine profiles of absorption and heating rate segregated by absorber (aerosol and gas).

  7. Global Aerosol Direct Radiative Effect from CALIOP and C3M

    NASA Astrophysics Data System (ADS)

    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.

  8. Global Aerosol Direct Radiative Effect From CALIOP and C3M

    NASA Technical Reports Server (NTRS)

    Winker, Dave; Kato, Seiji; Tackett, Jason

    2015-01-01

    Aerosols are responsible for the largest uncertainties in current estimates of climate forcing. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Estimation of Aerosol Direct Radiative Effects from Satellite and In Situ Measurements

    NASA Technical Reports Server (NTRS)

    Bergstrom, Robert W.; Russell, Philip B.; Schmid, Beat; Redemann, Jens; McIntosh, Dawn

    2000-01-01

    Ames researchers have combined measurements from satellite, aircraft, and the surface to estimate the effect of airborne particles (aerosols) on the solar radiation over the North Atlantic region. These aerosols (which come from both natural and pollution sources) can reflect solar radiation, causing a cooling effect that opposes the warming caused by carbon dioxide. Recently, increased attention has been paid to aerosol effects to better understand the Earth climate system.

  11. Radiative Effects of Aerosol in the Marine Environment: Tales from the Two-Column Aerosol Project

    NASA Astrophysics Data System (ADS)

    Berg, L. K.; Fast, J. D.; Barnard, J.; Chand, D.; Chapman, E. G.; Comstock, J. M.; Ferrare, R. A.; Flynn, C. J.; Hair, J. W.; Hostetler, C. A.; Hubbe, J.; Johnson, R.; Kassianov, E.; Kluzek, C.; Laskin, A.; Lee, Y.; Mei, F.; Michalsky, J. J.; Redemann, J.; Rogers, R. R.; Russell, P. B.; Sedlacek, A. J.; Schmid, B.; Shilling, J. E.; Shinozuka, Y.; Springston, S. R.; Tomlinson, J. M.; Wilson, J. M.; Zelenyuk, A.; Berkowitz, C. M.

    2013-12-01

    There is still uncertainty associated with the direct radiative forcing by atmospheric aerosol and its representation in atmospheric models. This is particularly true in marine environments near the coast where the aerosol loading is a function of both naturally occurring and anthropogenic aerosol. These regions are also subject to variable synoptic and thermally driven flows (land-sea breezes) that transport aerosol between the continental and marine environments. The situation is made more complicated due to seasonal changes in aerosol emissions. Given these differences in emissions, we expect significant differences in the aerosol intensive and extensive properties between summer and winter and data is needed to evaluate models over the wide range of conditions. To address this issue, the recently completed Two Column Aerosol Project (TCAP) was designed to measure the key aerosol parameters in two atmospheric columns, one located over Cape Cod, Massachusetts and another approximately 200 km from the coast over the Atlantic Ocean. Measurements included aerosol size distribution, chemical composition, optical properties and vertical distribution. Several aspects make TCAP unique, including the year-long deployment of a suite of surface-based instruments by the US Department of Energy's Atmospheric Radiation Measurement (ARM) Climate Research Facility and two aircraft intensive operations periods supported by the ARM Airborne Facility, one conducted in July 2012 and a second in February 2013. The presentation will include a discussion of the impact of the aerosol optical properties and their uncertainty on simulations of the radiation budget within the TCAP domain in the context of both single column and regional scale models. Data from TCAP will be used to highlight a number of important factors, including diurnal variation in aerosol optical depth measured at the surface site, systematic changes in aerosol optical properties (including scattering, absorption, and

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

    NASA Astrophysics Data System (ADS)

    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

  13. Exploring the Longwave Radiative Effects of Dust Aerosols

    NASA Technical Reports Server (NTRS)

    Hansell, Richard A., Jr.

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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

  15. CALIPSO-inferred aerosol direct radiative effects: Bias estimates using ground-based Raman lidars

    NASA Astrophysics Data System (ADS)

    Thorsen, Tyler J.; Fu, Qiang

    2015-12-01

    Observational constraints on the change in the radiative energy budget caused by the presence of aerosols, i.e., the aerosol direct radiative effect (DRE), have recently been made using observations from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite (CALIPSO). CALIPSO observations have the potential to provide improved global estimates of aerosol DRE compared to passive sensor-derived estimates due to CALIPSO's ability to perform vertically resolved aerosol retrievals over all surface types and over cloud. In this study, uncertainties in CALIPSO-inferred aerosol DRE are estimated using multiple years of observations from the Atmospheric Radiation Measurement (ARM) program's Raman lidars at midlatitude and tropical sites. We find that CALIPSO is unable to detect all radiatively significant aerosol, resulting in an underestimate in the magnitude of the aerosol DRE by 30-50% at the two ARM sites. The undetected aerosol is likely the consequence of random noise in CALIPSO measurements and therefore will affect global observations as well. This suggests that the global aerosol DRE inferred from CALIPSO observations are likely too weak. Also examined is the impact of the ratio of extinction-to-backscatter (i.e., the lidar ratio) whose value CALIPSO retrievals must assume to obtain the aerosol extinction profile. It is shown that if CALIPSO can reproduce the climatological value of the lidar ratio at a given location, then the aerosol DRE there can be accurately calculated (within about 3%).

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

    NASA Astrophysics Data System (ADS)

    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 %).

  17. Internally Consistent MODIS Estimate of Aerosol Clear-Sky Radiative Effect Over the Global Oceans

    NASA Technical Reports Server (NTRS)

    Remer, Lorraine A.; Kaufman, Yoram J.

    2004-01-01

    Modern satellite remote sensing, and in particular the MODerate resolution Imaging Spectroradiometer (MODIS), offers a measurement-based pathway to estimate global aerosol radiative effects and aerosol radiative forcing. Over the Oceans, MODIS retrieves the total aerosol optical thickness, but also reports which combination of the 9 different aerosol models was used to obtain the retrieval. Each of the 9 models is characterized by a size distribution and complex refractive index, which through Mie calculations correspond to a unique set of single scattering albedo, assymetry parameter and spectral extinction for each model. The combination of these sets of optical parameters weighted by the optical thickness attributed to each model in the retrieval produces the best fit to the observed radiances at the top of the atmosphere. Thus the MODIS Ocean aerosol retrieval provides us with (1) An observed distribution of global aerosol loading, and (2) An internally-consistent, observed, distribution of aerosol optical models that when used in combination will best represent the radiances at the top of the atmosphere. We use these two observed global distributions to initialize the column climate model by Chou and Suarez to calculate the aerosol radiative effect at top of the atmosphere and the radiative efficiency of the aerosols over the global oceans. We apply the analysis to 3 years of MODIS retrievals from the Terra satellite and produce global and regional, seasonally varying, estimates of aerosol radiative effect over the clear-sky oceans.

  18. Influence of Observed Diurnal Cycles of Aerosol Optical Depth on Aerosol Direct Radiative Effect

    NASA Technical Reports Server (NTRS)

    Arola, A.; Eck, T. F.; Huttunen, J.; Lehtinen, K. E. J.; Lindfors, A. V.; Myhre, G.; Smirinov, A.; Tripathi, S. N.; Yu, H.

    2013-01-01

    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 24 h ADRE was

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

    NASA Astrophysics Data System (ADS)

    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.

  20. CALIPSO-inferred aerosol direct radiative effects: Bias estimates using ground-based Raman lidars

    NASA Astrophysics Data System (ADS)

    Thorsen, T. J.; Fu, Q.

    2015-12-01

    Observational constraints on the change in radiative energy budget caused by the presence of aerosols, i.e. the aerosol direct radiative effect (DRE), have recently been made using observations from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite (CALIPSO). CALIPSO observations have the potential to provide improved global estimates of aerosol DRE compared to passive sensor-derived estimates due to CALIPSO's ability to perform vertically-resolved aerosol retrievals over all surface types and over cloud. In this study we estimate the uncertainties in CALIPSO-inferred aerosol DRE using multiple years of observations from the Atmospheric Radiation Measurement (ARM) program's Raman lidars (RL) at midlatitude and tropical sites. Examined are assumptions about the ratio of extinction-to-backscatter (i.e. the lidar ratio) made by the CALIPSO retrievals, which are needed to retrieve the aerosol extinction profile. The lidar ratio is shown to introduce minimal error in the mean aerosol DRE at the top-of-atmosphere and surface. It is also shown that CALIPSO is unable to detection all radiatively-significant aerosol, resulting in an underestimate in the magnitude of the aerosol DRE. Therefore, global estimates of the aerosol DRE inferred from CALIPSO are likely too weak.

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

    NASA Astrophysics Data System (ADS)

    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

  2. North Atlantic Aerosol Properties and Direct Radiative Effects: Key Results from TARFOX and ACE-2

    NASA Technical Reports Server (NTRS)

    Russell, P. B.; Livingston, J. M.; Schmid, B.; Bergstrom, R. A.; Hignett, P.; Hobbs, P. V.; Durkee, P. A.; Condon, Estelle (Technical Monitor)

    1998-01-01

    Aerosol effects on atmospheric radiative fluxes provide a forcing function that can change the climate in potentially significant ways. This aerosol radiative Forcing is a major source of uncertainty in understanding the observed climate change of the past century and in predicting, future climate. To help reduce this uncertainty, the International Global Atmospheric Chemistry Project (IGAC) has endorsed a series of multiplatform aerosol field campaigns. The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the second Aerosol Characterization Experiment (ACE-2) were the first IGAC campaigns to address the impact of anthropogenic aerosols. Both TARFOX and ACE-2 gathered extensive data sets on aerosol properties and radiative effects. TARFOX focused on the urban-industrial haze plume flowing from the eastern United States over the western Atlantic Ocean, whereas ACE-2 studied aerosols carried over the eastern Atlantic from both European urban/industrial and African mineral sources. These aerosols often have a marked influence on the top-of-atmosphere radiances measured by satellites, as illustrated in Figure 1. Shown there are contours of aerosol optical depth derived from radiances measured by the AVHRR sensor on the NOAA-11 satellite. The contours readily show that aerosols originating in North America, Europe, and Africa impact the radiative properties of air over the North Atlantic. However, the accurate derivation of flux chances, or radiative forcing, from the satellite-measured radiances or 'etrieved optical depths remains a difficult challenge. In this paper we summarize key Initial results from TARFOX and, to a lesser extent ACE-2, with a focus on those results that allow an improved assessment of the flux changes caused by North Atlantic aerosols at middle and high latitudes.

  3. North Atlantic Aerosol Properties and Direct Radiative Effects: Key Results from TARFOX and ACE-2

    NASA Technical Reports Server (NTRS)

    Russell, P. B.; Livingston, J. M.; Schmid, B.; Bergstrom, Robert A.; Hignett, P.; Hobbs, P. V.; Durkee, P. A.

    2000-01-01

    Aerosol effects on atmospheric radiative fluxes provide a forcing function that can change the climate In potentially significant ways. This aerosol radiative forcing is a major source of uncertainty in understanding the observed climate change of the past century and in predicting future climate. To help reduce this uncertainty, the International Global Atmospheric Chemistry Project (IGAC) has endorsed a series of multiplatform aerosol field campaigns. The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the second Aerosol Characterization Experiment (ACE-2) were the first IGAC campaigns to address the impact of anthropogenic aerosols, Both TARFOX and ACE-2 gathered extensive data sets on aerosol properties and radiative effects, TARFOX focused on the urban-industrial haze plume flowing from the eastern United States over the western Atlantic Ocean, whereas ACE-2 studied aerosols carried over the eastern Atlantic from both European urban/industrial and African mineral sources. These aerosols often have a marked influence on the top-of-atmosphere radiances measured by satellites. Shown there are contours of aerosol optical depth derived from radiances measured by the AVHRR sensor on the NOAA-11 satellite. The contours readily show that aerosols originating in North America, Europe, and Africa impact the radiative properties of air over the North Atlantic. However, the accurate derivation of flux changes, or radiative forcing, from the satellite measured radiances or retrieved optical depths remains a difficult challenge. In this paper we summarize key initial results from TARFOX and, to a lesser extent, ACE-2, with a focus on those results that allow an improved assessment of the flux changes caused by North Atlantic aerosols at middle latitudes.

  4. Carbonaceous Aerosols and Radiative Effects Study (CARES), g1-aircraft, sedlacek sp2

    DOE Data Explorer

    Sedlacek, Art

    2011-08-30

    The primary objective of the Carbonaceous Aerosol and Radiative Effects Study (CARES) in 2010 was to investigate the evolution of carbonaceous aerosols of different types and their optical and hygroscopic properties in central California, with a focus on the Sacramento urban plume.

  5. North Atlantic Aerosol Radiative Effects Based on Satellite Measurements and Aerosol Intensive Properties from TARFOX and ACE-2

    NASA Technical Reports Server (NTRS)

    Bergstrom, Robert W.; Russell, Philip B.

    2000-01-01

    We estimate the impact of North Atlantic aerosols on the net shortwave flux at the tropopause by combining maps of satellite-derived aerosol optical depth (AOD) with model aerosol properties. We exclude African dust, primarily by restricting latitudes to 25-60 N. Aerosol properties were determined via column closure analyses in two recent experiments, TARFOX and ACE 2. The analyses use in situ measurements of aerosol composition and air- and ship-borne sunphotometer measurements of AOD spectra. The resulting aerosol model yields computed flux sensitivities (dFlux/dAOD) that agree with measurements by airborne flux radiometers in TARFOX. It has a midvisible single-scattering albedo of 0.9, which is in the range obtained from in situ measurements of aerosol scattering and absorption in both TARFOX and ACE 2. Combining seasonal maps of AVHRR-derived midvisible AOD with the aerosol model yields maps of 24-hour average net radiative flux changes at the tropopause. For cloud-free conditions, results range from -9 W/sq m near the eastern US coastline in the summer to -1 W/sq m in the mid-Atlantic during winter; the regional annual average is -3.5 W/sq m. Using a non- absorbing aerosol model increases these values by about 30%. We estimate the effect of clouds using ISCCP cloud-fraction maps. Because ISCCP midlatitude North Atlantic cloud fractions are relatively large, they greatly reduce the computed aerosol-induced flux changes. For example, the regional annual average decreases from -3.5 W/sq m to -0.8 W/sq m. We compare results to previous model calculations for a variety of aerosol types.

  6. A Global Modeling Study on Carbonaceous Aerosol Microphysical Characteristics and Radiative Effects

    NASA Technical Reports Server (NTRS)

    Bauer, S. E.; Menon, S.; Koch, D.; Bond, T. C.; Tsigaridis, K.

    2010-01-01

    Recently, attention has been drawn towards black carbon aerosols as a short-term climate warming mitigation candidate. However the global and regional impacts of the direct, indirect and semi-direct aerosol effects are highly uncertain, due to the complex nature of aerosol evolution and the way that mixed, aged aerosols interact with clouds and radiation. A detailed aerosol microphysical scheme, MATRIX, embedded within the GISS climate model is used in this study to present a quantitative assessment of the impact of microphysical processes involving black carbon, such as emission size distributions and optical properties on aerosol cloud activation and radiative effects. Our best estimate for net direct and indirect aerosol radiative flux change between 1750 and 2000 is -0.56 W/m2. However, the direct and indirect aerosol effects are quite sensitive to the black and organic carbon size distribution and consequential mixing state. The net radiative flux change can vary between -0.32 to -0.75 W/m2 depending on these carbonaceous particle properties at emission. Taking into account internally mixed black carbon particles let us simulate correct aerosol absorption. Absorption of black carbon aerosols is amplified by sulfate and nitrate coatings and, even more strongly, by organic coatings. Black carbon mitigation scenarios generally showed reduced radiative fluxeswhen sources with a large proportion of black carbon, such as diesel, are reduced; however reducing sources with a larger organic carbon component as well, such as bio-fuels, does not necessarily lead to a reduction in positive radiative flux.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  8. Aerosol Absorption and Radiative Forcing

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

  11. Aerosol radiative forcing over land: effect of surface and cloud reflection

    NASA Astrophysics Data System (ADS)

    Satheesh, S. K.

    2002-12-01

    It is now clearly understood that atmospheric aerosols have a significant impact on climate due to their important role in modifying the incoming solar and outgoing infrared radiation. The question of whether aerosol cools (negative forcing) or warms (positive forcing) the planet depends on the relative dominance of absorbing aerosols. Recent investigations over the tropical Indian Ocean have shown that, irrespective of the comparatively small percentage contribution in optical depth ( ~ 11%), soot has an important role in the overall radiative forcing. However, when the amount of absorbing aerosols such as soot are significant, aerosol optical depth and chemical composition are not the only determinants of aerosol climate effects, but the altitude of the aerosol layer and the altitude and type of clouds are also important. In this paper, the aerosol forcing in the presence of clouds and the effect of different surface types (ocean, soil, vegetation, and different combinations of soil and vegetation) are examined based on model simulations, demonstrating that aerosol forcing changes sign from negative (cooling) to positive (warming) when reflection from below (either due to land or clouds) is high.

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

    NASA Technical Reports Server (NTRS)

    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. Interpretation of Aerosol Optical and Morphological Properties during the Carbonaceous Aerosols and Radiative Effects Study in Sacramento, June 2010

    NASA Astrophysics Data System (ADS)

    Gorkowski, K.; Mazzoleni, C.; China, S.; Sharma, N.; Flowers, B. A.; Dubey, M. K.; Gyawali, M. S.; Arnott, W. P.; Zaveri, R. A.

    2010-12-01

    The Sacramento Carbonaceous Aerosols and Radiative Effects Study (CARES) utilized two ground sites T0 and T1 along with an aircraft platform to characterize carbonaceous aerosol chemical and physical properties and their evolution. The T0 site was chosen within the Sacramento metropolitan area for measuring primary and secondary aerosols generated in the city. The T1 site was chosen East of Sacramento on the Sierra foothill to study the evolution and processing of the Sacramento aerosol plume and to assess the characteristics of the background air. To reach T1, the Sacramento aerosols traveled often over the Blodgett Forest resulting in significant aging due coagulation, condensation, and photochemical processes. The ground sites were chosen for this unique and reoccurring transport pattern of the aerosols. The campaign took place in June 2010. Six Integrated Photoacoustic/Nephelometer Spectrometers (IPNSs) were installed at the sites to simultaneously record aerosol light scattering and absorption data. The optical properties of the aerosols were measured at 355nm (ultraviolet), 375nm (ultraviolet), 405nm (blue), 532nm (green), and 781nm (red). In conjugation with the IPNSs, aerosol filters for electron microscopy analysis were collected at each site; these were examined using a field emission scanning electron microscope to study the aerosol morphology. The origins of the air masses did vary daily, but a few general trends emerged. The processing of the IPNS data with a wavelet denoising technique greatly enhanced the signal to noise ratio of the measurements enabling a better understanding of the aerosol optical properties for various airmasses with different characteristics. Typically signals at both sites were lower than expected, however the processed signals from T0 clearly showed a daily rise and dilution of the Sacramento plume. Using the processed signals from both sites the transportation of the Sacramento plume was detectable. The IPNS data were

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Estimation of the direct aerosol radiative effect over China based on satellite remote sensing measurements

    NASA Astrophysics Data System (ADS)

    Sundström, A.-M.; Huttunen, J.; Arola, A.; Kolmonen, P.; Sogacheva, L.; de Leeuw, G.

    2012-04-01

    Aerosols influence the radiative budget of the Earth-atmosphere system directly by scattering and absorbing solar and thermal infrared radiation, and indirectly by modifying the microphysical, and hence the radiative properties and lifetimes of clouds. However, the quantification of aerosol radiative effects is complex and large uncertainties still exist, mainly due to the high spatial and temporal variation of the aerosol concentration and mass, as well as their relatively short lifetime in the atmosphere. The clear-sky direct aerosol radiative effect at the top of the atmosphere (TOA) is defined as the difference between the net solar flux ΔFTOA (difference between downward and upward fluxes) defined with (F) and without (F0) aerosols. The negative values of ΔFTOA correspond to planetary cooling, whereas positive values correspond to increased atmospheric warming. Satellites offer an opportunity to observe the spatial distribution of aerosol properties with adequate resolution and coverage from regional to global scales. In this work multisensor satellite observations are used to estimate the direct aerosol radiative effect at the top of the atmosphere over China within the shortwave (SW, 0.3-5 microns) region. The Moderate Imaging Spectroradiometer onboard (MODIS) NASA's Terra and Aqua platforms offer global observations of aerosol and cloud optical properties nearly on a daily basis, whereas the Clouds and the Earth's Radian Energy System (CERES) instruments measure simultaneously TOA broadband fluxes e.g. in the shortwave region. Hence, the instantaneous aerosol direct radiative effect for a month at TOA can be estimated using the MODIS aerosol optical depth (AOD) and coincident broadband flux from the CERES instrument. The values for F and F0 are obtained by performing a linear regression between MODIS AOD at 0.55 microns wavelength and CERES SW flux. The instantaneous values are converted to monthly means by using a radiative transfer code. Preliminary

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Technical Reports Server (NTRS)

    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

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

    PubMed

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

    2016-05-24

    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. PMID:26831092

  19. Comparison of Asian aerosol's radiative effect in Seoul and Gosan, Korea

    NASA Astrophysics Data System (ADS)

    Yoon, S.; Lee, S.; Choi, I.

    2007-05-01

    Seasonal variations of aerosol optical properties as well as their direct radiative effects were investigated using the ground-based aerosol measurements and an optical model calculation in Seoul, a mega city, and Gosan, a background rural island, Korea. From the yearly AERONET dataset, our analysis of seasonal and monthly cycle of aerosol optical depth (AOD) shows that AODs in Seoul are higher than those in Gosan because of the higher concentrations of water soluble ions in Seoul. Especially, seasonal AOD differences of both sites becomes maximum in Summer due to the synoptic meteorological patterns and hygroscopic growth of anthropogenic aerosols. OPAC (Optical Properties of Aerosol and Clouds) model and Fu-Liou RTM (Radiative Transfer Model) were employed for the evaluation of aerosol direct radiative forcing (ADRF) at surface and top of the atmosphere (TOA). A method of determining the values of aerosol optical properties as input parameters was utilized for the ADRF calculation from the AERONET dataset. In each season, the mean ADRF in Seoul turned out to be larger than that of Gosan. The ADRF in Gosan from RTM calculation was compared with the ground-based radiation measurements during the ACE-Asia IOP in 2001 and the ABC-EAREX2005 IOP in 2005. In addition, ADRF contributions by chemical compositions were compared in this study between Seoul and Gosan.

  20. Evaluation of aerosol indirect radiative effects on climate in the EMAC model

    NASA Astrophysics Data System (ADS)

    Chang, Dong Yeong; Tost, Holger; Steil, Benedikt; Lelieveld, Jos

    2013-04-01

    Anthropogenic aerosol particles directly and indirectly influence cloud properties and the Earth's radiative energy budget. Several studies have estimated the effects on climate using global circulation models (GCMs), indicating large differences between different models and large uncertainty ranges. These are mostly attributed to different cloud microphysical process parameterizations and uncertainties in the representation of aerosols. Without detailed cloud microphysical processes, using empirical relations between aerosol number or mass and cloud droplet number potentially even large discrepancies may arise. In the present study, a mechanistic aerosol activation scheme, based on double moment cloud microphysics, is used to compute aerosol indirect radiative and cloud effects in the EMAC model. Aerosol activation is linked to the cloud droplet nucleation processes in warm clouds, accounting for the number, size, and chemical composition of particles under ambient meteorological conditions. This approach uses a combination of empirical and semi-empirical parameters to represent aerosol water uptake and hygroscopic growth into cloud droplets. To evaluate the performance of our approach satellite datasets are used; for example, total cloud fraction from MODIS data and cloud radiative forcing at the top of atmosphere from CERES EBAF data.

  1. Study on aerosol optical properties and radiative effect in cloudy weather in the Guangzhou region.

    PubMed

    Deng, Tao; Deng, XueJiao; Li, Fei; Wang, ShiQiang; Wang, Gang

    2016-10-15

    Currently, Guangzhou region was facing the problem of severe air pollution. Large amount of aerosols in the polluted air dramatically attenuated solar radiation. This study investigated the vertical optical properties of aerosols and inverted the height of boundary layer in the Guangzhou region using the lidar. Simultaneously, evaluated the impact of different types of clouds on aerosol radiation effects using the SBDART. The results showed that the height of the boundary layer and the surface visibility changed consistently, the average height of the boundary layer on the hazy days was only 61% of that on clear days. At the height of 2km or lower, the aerosol extinction coefficient profile distribution decreased linearly along with height on clear days, but the haze days saw an exponential decrease. When there was haze, the changing of heating rate of atmosphere caused by the aerosol decreased from 3.72K/d to 0.9K/d below the height of 2km, and the attenuation of net radiation flux at the ground surface was 97.7W/m(2), and the attenuation amplitude was 11.4%; when there were high clouds, the attenuation was 125.2W/m(2) and the attenuation amplitude was 14.6%; where there were medium cloud, the attenuation was 286.4W/m(2) and the attenuation amplitude was 33.4%. Aerosol affected mainly shortwave radiation, and affected long wave radiation very slightly. PMID:27295588

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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 2% precipitation decease 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.

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

    NASA Astrophysics Data System (ADS)

    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

  5. A satellite view of the direct effect of aerosols on solar radiation at global scale

    NASA Astrophysics Data System (ADS)

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Potential Aerosol Indirect Effects on Atmospheric Circulation and Radiative Forcing through Deep Convection

    SciTech Connect

    Fan, Jiwen; Rosenfeld, Daniel; Ding, Yanni; Leung, Lai-Yung R.; Li, Zhanqing

    2012-05-10

    Aerosol indirect effects, i.e., the interactions of aerosols with clouds by serving as cloud condensation nuclei (CCN) or ice nuclei (IN), constitute the largest uncertainty in climate forcing and projection. Previous IPCC reported aerosol indirect forcing is negative, which does not account for aerosol-convective cloud interactions because the complex processes involved are poorly understood and represented in climate models. Here we report that aerosol indirect effect on deep convective cloud systems can lead to enhanced regional convergence and a strong top-of atmosphere (TOA) warming. Aerosol invigoration effect on convection can result in a strong radiative warming in the atmosphere (+5.6 W m-2) due to strong night-time warming, a lofted latent heating, and a reduced diurnal temperature difference, all of which could remarkably impact regional circulation and modify weather systems. We further elucidated how aerosols change convective intensity, diabatic heating, and regional circulation under different environmental conditions and concluded that wind shear and cloud base temperature play key roles in determining the significance of aerosol invigoration effect for convective systems.

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

    SciTech Connect

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

    2005-03-18

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

  9. Investigation of Trends in Aerosol Direct Radiative Effects over North America Using a Coupled Meteorology-Chemistry Model

    EPA Science Inventory

    A comprehensive investigation of the processes regulating tropospheric aerosol distributions, their optical properties, and their radiative effects in conjunction with verification of their simulated radiative effects for past conditions relative to measurements is needed in orde...

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

    NASA Astrophysics Data System (ADS)

    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.

  11. A study of regional aerosol radiative properties and effects on ultraviolet-B radiation

    NASA Astrophysics Data System (ADS)

    Wenny, B. N.; Schafer, J. S.; Deluisi, J. J.; Saxena, V. K.; Barnard, W. F.; Petropavlovskikh, I. V.; Vergamini, A. J.

    1998-07-01

    A field experiment was conducted in western North Carolina to investigate the relationship between aerosol optical properties and atmospheric transmission. Two research measurement sites in close horizontal proximity but at different altitudes were established to measure the transmission of UV radiation through a slab of atmosphere. An identical set of radiation sensing instruments, including a broadband UV-B radiometer, a direct Sun pyrheliometer, a shadowband radiometer, and a spectral photometer, was placed at both sites, a mountaintop site (Mount Gibbes 35.78°N, 82.29°W, 2004 m elevation) and a valley site (Black Mountain, North Carolina 35.66°N, 82.38°N, 951 m elevation). Aerosol size distribution sampling equipment was located at the valley site. Broadband solar pseudo-optical depth and aerosol optical depths at 415 nm, 500 nm, and 673 nm were measured for the lowest 1-km layer of the troposphere. The measurements exhibited variations based on an air mass source region as determined by back trajectory analysis. Broadband UV-B transmission through the layer also displayed variations relating to air mass source region. Spectral UV transmission revealed a dependence upon wavelength, with decreased transmission in the UV-B region (300-320 nm) versus UV-A region (320-363.5 nm). UV-B transmission was found to be negatively correlated with aerosol optical depth. Empirical relations were developed to allow prediction of solar noon UV-B transmission if aerosol optical depth at two visible wavelengths (415 and 500 nm) is known. A new method was developed for determining aerosol optical properties from the radiation and aerosol size distribution measurements. The aerosol albedo of single scatter was found to range from 0.75 to 0.93 and the asymmetry factor ranged from 0.63 to 0.76 at 312 nm, which is close to the peak response of human skin to UV radiation.

  12. Aerosols in the Convective Boundary Layer: Radiation Effects on the Coupled Land-Atmosphere System

    NASA Astrophysics Data System (ADS)

    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

  13. Ground-based remote sensing of aerosol climatology in China: Aerosol optical properties, direct radiative effect and its parameterization

    NASA Astrophysics Data System (ADS)

    Xia, X.; Che, H.; Zhu, J.; Chen, H.; Cong, Z.; Deng, X.; Fan, X.; Fu, Y.; Goloub, P.; Jiang, H.; Liu, Q.; Mai, B.; Wang, P.; Wu, Y.; Zhang, J.; Zhang, R.; Zhang, X.

    2016-01-01

    Spatio-temporal variation of aerosol optical properties and aerosol direct radiative effects (ADRE) are studied based on high quality aerosol data at 21 sunphotometer stations with at least 4-months worth of measurements in China mainland and Hong Kong. A parameterization is proposed to describe the relationship of ADREs to aerosol optical depth at 550 nm (AOD) and single scattering albedo at 550 nm (SSA). In the middle-east and south China, the maximum AOD is always observed in the burning season, indicating a significant contribution of biomass burning to AOD. Dust aerosols contribute to AOD significantly in spring and their influence decreases from the source regions to the downwind regions. The occurrence frequencies of background level AOD (AOD < 0.10) in the middle-east, south and northwest China are very limited (0.4%, 1.3% and 2.8%, respectively). However, it is 15.7% in north China. Atmosphere is pristine in the Tibetan Plateau where 92.0% of AODs are <0.10. Regional mean SSAs at 550 nm are 0.89-0.90, although SSAs show substantial site and season dependence. ADREs at the top and bottom of the atmosphere for solar zenith angle of 60 ± 5° are -16--37 W m-2 and -66--111 W m-2, respectively. ADRE efficiency shows slight regional dependence. AOD and SSA together account for more than 94 and 87% of ADRE variability at the bottom and top of the atmosphere. The overall picture of ADRE in China is that aerosols cool the climate system, reduce surface solar radiation and heat the atmosphere.

  14. Quantification of regional radiative impacts and climate effects of tropical fire aerosols

    NASA Astrophysics Data System (ADS)

    Tosca, M. G.; Zender, C. S.; Randerson, J. T.

    2011-12-01

    Regionally expansive smoke clouds originating from deforestation fires in Indonesia can modify local precipitation patterns via direct aerosol scattering and absorption of solar radiation (Tosca et al., 2010). Here we quantify the regional climate impacts of fire aerosols for three tropical burning regions that together account for about 70% of global annual fire emissions. We use the Community Atmosphere Model, version 5 (CAM5) coupled to a slab ocean model (SOM) embedded within the Community Earth System Model (CESM). In addition to direct aerosol radiative effects, CAM5 also quantifies indirect, semi-direct and cloud microphysical aerosol effects. Climate impacts are determined using regionally adjusted emissions data that produce realistic aerosol optical depths in CAM5. We first analyzed a single 12-year transient simulation (1996-2007) forced with unadjusted emissions estimates from the Global Fire Emissions Database, version 3 (GFEDv3) and compared the resulting aerosol optical depths (AODs) for 4 different burning regions (equatorial Asia, southern Africa, South America and boreal North America) to observed MISR and MODIS AODs for the same period. Based on this analysis we adjusted emissions for each burning region between 150 and 300% and forced a second simulation with the regionally adjusted emissions. Improved AODs from this simulation are compared to AERONET observations available at 15 stations throughout the tropics. We present here two transient simulations--one with the adjusted fire emissions and one without fires--to quantify the cumulative fire aerosol climate impact for three major tropical burning regions (equatorial Asia, southern Africa and South America). Specifically, we quantify smoke effects on radiation, precipitation, and temperature. References Tosca, M.G., J.T. Randerson, C.S. Zender, M.G. Flanner and P.J. Rasch (2010), Do biomass burning aerosols intensify drought in equatorial Asia during El Nino?, Atmos. Chem. Phys., 10, 3515

  15. Measurement-based estimates of direct radiative effects of absorbing aerosols above clouds

    NASA Astrophysics Data System (ADS)

    Feng, Nan; Christopher, Sundar A.

    2015-07-01

    The elevated layers of absorbing smoke aerosols from western African (e.g., Gabon and Congo) biomass burning activities have been frequently observed above low-level stratocumulus clouds off the African coast, which presents an excellent natural laboratory for studying the effects of aerosols above clouds (AAC) on regional energy balance in tropical and subtropical environments. Using spatially and temporally collocated Moderate Resolution Imaging Spectroradiometer, Ozone Monitoring Instrument (OMI), and Clouds and the Earth's Radiant Energy System data sets, the top-of-atmosphere shortwave aerosol direct shortwave radiative effects (ARE) of absorbing aerosols above low-level water clouds in the southeast Atlantic Ocean was examined in this study. The regional averaged instantaneous ARE has been estimated to be 36.7 ± 20.5 Wm-2 (regional mean ± standard deviation) along with a mean positive OMI Aerosol Index at 1.3 in August 2006 based on multisensors measurements. The highest magnitude of instantaneous ARE can even reach 138.2 Wm-2. We assess that the 660 nm cloud optical depth (COD) values of 8-12 is the critical value above (below) which aerosol absorption (scattering) effect dominates and further produces positive (negative) ARE values. The results further show that ARE values are more sensitive to aerosols above lower COD values than cases for higher COD values. This is among the first studies to provide quantitative estimates of shortwave ARE due to AAC events from an observational perspective.

  16. Direct and indirect radiative effects of aerosols using the coupled system of aerosol HAM module and the Weather Research and Forecasting (WRF) model

    NASA Astrophysics Data System (ADS)

    Mashayekhi, Rabab; Irannejad, Parviz; Feichter, Johann; Akbari Bidokhti, Abbas Ali Ali

    2010-05-01

    The fully coupled aerosol-cloud and radiation WRF-HAM modeling system is presented. The aerosol HAM model is implemented within the chemistry version of WRF modeling system. HAM is based on a "pseudo-modal" approach for representation of the particle size distribution. Aerosols are grouped into four geometrical size classes and two types of mixed and insoluble particles. The aerosol components considered are sulfate, black carbon, particulate organic matter, sea salt and mineral dust. Microphysical processes including nucleation, condensation and coagulation of aerosol particles are considered using the microphysics M7 scheme. Horizontal transport of the aerosol particles is simulated using the advection scheme in WRF. Convective transport and vertical mixing of aerosol particles are also considered in the coupled system. A flux-resistance method is used for dry deposition of aerosol particles. Aerosol sizes and chemical compositions are used to determine the aerosol optical properties. Direct effects of aerosols on incoming shortwave radiation flux are simulated by transferring the aerosol optical parameters to the Goddard shortwave radiation scheme. Indirect effects of aerosols are simulated by using a prognostic treatment of cloud droplet number and adding modules that activate aerosol particles to form cloud droplets. The first and second indirect effects, i.e. the interactions of clouds and incoming solar radiation are implemented in WRF-Chem by linking the simulated cloud droplet number with the Goddard shortwave radiation scheme and the Lin et al. microphysics scheme. The simulations are carried out for a 6-day period from 22 to 28 February 2006 in a domain with 30-km grid spacing, encompassing the south-western Asia, North Africa and some parts of Europe. The results show a negative radiative forcing over most parts of the domain, mainly due to the presence of mineral dust aerosols. The simulations are evaluated using the measured downward radiation in

  17. An Overview of the 2010 Carbonaceous Aerosol and Radiative Effects Study (CARES) Field Campaign

    NASA Astrophysics Data System (ADS)

    Zaveri, R. A.; Shaw, W. J.; Cziczo, D. J.

    2010-12-01

    The primary objective of the DOE Carbonaceous Aerosol and Radiative Effects Study (CARES) in June 2010 was to investigate the evolution of carbonaceous aerosols of different types and their optical and hygroscopic properties in central California, with a focus on the Sacramento urban plume. Carbonaceous aerosol components, which include black carbon (BC), urban primary organic aerosols (POA), biomass burning aerosols, and secondary organic aerosols (SOA) from both urban and biogenic precursors, have been shown to play a major role in the direct and indirect radiative forcing of climate. However, significant knowledge gaps and uncertainties still exist in the process-level understanding of: 1) SOA formation, 2) BC mixing state evolution, and 3) the optical and hygroscopic properties of fresh and aged carbonaceous aerosols. The CARES 2010 field study was designed to address several specific science questions under these three topics. During summer the Sacramento-Blodgett Forest corridor effectively serves as a mesoscale daytime flow reactor in which the urban aerosols undergo significant aging as they are transported to the northeast by upslope flow. The CARES campaign observation strategy consisted of the DOE G-1 aircraft sampling upwind, within, and outside of the evolving Sacramento urban plume in the morning and again in the afternoon. The G-1 payload consisted of a suite of instruments to measure trace gases, aerosol size distribution, composition, and optical properties. The NASA B-200 aircraft carrying a High Spectral Resolution Lidar (HSRL) and a Research Scanning Polarimeter (RSP) was also deployed to characterize the vertical and horizontal distribution of aerosols and aerosol optical properties. The aircraft measurements were complemented by heavily-instrumented ground sites within the Sacramento urban area and at a downwind site in Cool, California, to characterize the diurnal evolution of meteorological variables, trace gases, aerosol precursors, aerosol

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    Yu, H.; Kaufman, Y. J.; Chin, M.; Feingold, G.; Remer, L. A.; Anderson, T. L.; Balkanski, Y.; Bellouin, N.; Boucher, O.; Christopher, S.; Decola, P.; Kahn, R.; Koch, D.; Loeb, N.; Reddy, M. S.; Schulz, M.; Takemura, T.; Zhou, M.

    2006-02-01

    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 contamination

  20. Overview of the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES)

    SciTech Connect

    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

  1. Overview of the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES)

    SciTech Connect

    Zaveri, Rahul A.; Shaw, William J.; Cziczo, D. J.; Schmid, Beat; Ferrare, R.; Alexander, M. L.; Alexandrov, Mikhail; Alvarez, R. J.; Arnott, W. P.; Atkinson, D.; Baidar, Sunil; Banta, Robert M.; Barnard, James C.; Beranek, Josef; Berg, Larry K.; Brechtel, Fred J.; Brewer, W. A.; Cahill, John F.; Cairns, Brian; Cappa, Christopher D.; Chand, Duli; China, Swarup; Comstock, Jennifer M.; Dubey, Manvendra K.; Easter, Richard C.; Erickson, Matthew H.; Fast, Jerome D.; Floerchinger, Cody; Flowers, B. A.; Fortner, Edward; Gaffney, Jeffrey S.; Gilles, Mary K.; Gorkowski, K.; Gustafson, William I.; Gyawali, Madhu S.; Hair, John; Hardesty, Michael; Harworth, J. W.; Herndon, Scott C.; Hiranuma, Naruki; Hostetler, Chris A.; Hubbe, John M.; Jayne, J. T.; Jeong, H.; Jobson, Bertram T.; Kassianov, Evgueni I.; Kleinman, L. I.; Kluzek, Celine D.; Knighton, B.; Kolesar, K. R.; Kuang, Chongai; Kubatova, A.; Langford, A. O.; Laskin, Alexander; Laulainen, Nels S.; Marchbanks, R. D.; Mazzoleni, Claudio; Mei, F.; Moffet, Ryan C.; Nelson, Danny A.; Obland, Michael; Oetjen, Hilke; Onasch, Timothy B.; Ortega, Ivan; Ottaviani, M.; Pekour, Mikhail S.; Prather, Kimberly A.; Radney, J. G.; Rogers, Ray; Sandberg, S. P.; Sedlacek, Art; Senff, Christoph; Senum, Gunar; Setyan, Ari; Shilling, John E.; Shrivastava, ManishKumar B.; Song, Chen; Springston, S. R.; Subramanian, R.; Suski, Kaitlyn; Tomlinson, Jason M.; Volkamer, Rainer M.; Wallace, Hoyt A.; Wang, J.; Weickmann, A. M.; Worsnop, Douglas R.; Yu, Xiao-Ying; Zelenyuk, Alla; Zhang, Qi

    2012-08-22

    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 results from the aircraft and ground-based sampling platforms, and d) a roadmap of planned data

  2. Overview of the 2010 Carbonaceous Aerosols and Radiative Effects Study (CARES)

    NASA Technical Reports Server (NTRS)

    Zaveri, R. A.; Shaw, W. J.; Cahill, J. F.; Cairns, Brian; Cappa, C. D.; Ottaviani, Matteo; Cziczo, D. J.; Ferrare, Richard A.; Alexander, M. L.; Alexandrov, Mikhail Dmitrievic; Alvarez, R. J.; Arnott, W. P.; Atkinson, D. B.; Schmid, B.; Chand, D.; China, S.; Comstock, J. M.; Dubey, M. K.; Easter, R. C.; Erickson, M. H.; Fast, J. D.; Flowers, B. A.; Fortner, E.; Baidar, S.; Hair, J.; Hostetler, C.; Obland, M. D.; Rogers, R. R.; Floerchinger, C.; Banta, R. M.; Barnard, J. C.; Beranek, J.; Berg, L. K.; Brechtel, F.; Brewer, W. A.

    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 US 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 climaterelated 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 planned data

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  4. A review of measurement-based assessment of aerosol direct radiative effect and forcing

    NASA Astrophysics Data System (ADS)

    Yu, H.; Kaufman, Y. J.; Chin, M.; Feingold, G.; Remer, L. A.; Anderson, T. L.; Balkanski, Y.; Bellouin, N.; Boucher, O.; Christopher, S.; Decola, P.; Kahn, R.; Koch, D.; Loeb, N.; Reddy, M. S.; Schulz, M.; Takemura, T.; Zhou, M.

    2005-08-01

    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. Here we assess the aerosol optical depth, 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 thickness (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% is contributed by human activities, as determined by MODIS fine-mode fraction. The multi-angle MISR derives an annual average AOT 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 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) over global ocean. Accounting for thin cirrus contamination of the satellite derived aerosol field will reduce the TOA DRE to -5.0 Wm-2. Because of a lack of measurements of aerosol absorption and difficulty in characterizing land surface reflection, estimates of DRE over land and

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

    EPA Science Inventory

    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...

  6. CARES: Carbonaceous Aerosol and Radiative Effects Study Operations Plan

    SciTech Connect

    Zaveri, RA; Shaw, WJ; Cziczo, DJ

    2010-07-12

    The CARES field campaign is motivated by the scientific issues described in the CARES Science Plan. The primary objectives of this field campaign are to investigate the evolution and aging of carbonaceous aerosols and their climate-affecting properties in the urban plume of Sacramento, California, a mid-size, mid-latitude city that is located upwind of a biogenic volatile organic compound (VOC) emission region. Our basic observational strategy is to make comprehensive gas, aerosol, and meteorological measurements upwind, within, and downwind of the urban area with the DOE G-1 aircraft and at strategically located ground sites so as to study the evolution of urban aerosols as they age and mix with biogenic SOA precursors. The NASA B-200 aircraft, equipped with the High Spectral Resolution Lidar (HSRL), digital camera, and the Research Scanning Polarimeter (RSP), will be flown in coordination with the G-1 to characterize the vertical and horizontal distribution of aerosols and aerosol optical properties, and to provide the vertical context for the G-1 and ground in situ measurements.

  7. Radiation and temperature effects of the intensive injection of dust aerosol into the atmosphere

    NASA Astrophysics Data System (ADS)

    Gorchakova, I. A.; Mokhov, I. I.; Rublev, A. N.

    2015-03-01

    Based on the measurements at the AERONET station (Ilorin, Nigeria), quantitative estimates of radiation and temperature effects of dust aerosol during the intensive sand storm in the Sahara Desert from January 28 to February 6, 2000, are obtained. The model used in calculations implies particles of dust aerosol being no more than 15 μm in radius (according to the data from AERONET station); another model takes into account large particles (LPs) up to 60 μm in radius and involves a spectral variation in the OPAC refraction index. In the short infrared region, the optical thickness of aerosol weakening increases with LPs taken into account in the aerosol model; the albedo of aerosol single scattering reduces in comparison to the respective optical parameters of the first model. Dust aerosol cools the earth's surface. In the presence of LPs in dust aerosol, the surface-atmosphere system can both cool and warm, while if LPs less than 15 μm in size are not taken into account, the surface cools. The rate of cooling of the 10-m near-surface atmospheric layer Δ T/Δ t changes in the interval of -(4-21)°C/day without the influence of LPs over 15 μm in size on solar radiation transfer taken into account; if this influence is taken into account, the rate is -(6-36)°C/day. In the long infrared region, the surface-atmosphere system warms more intensively if LPs are taken into account by the aerosol model. The heating rate of the 10-m near-surface atmospheric layer does not exceed ~0.5°C/day during the entire period of dust emission without LPs taken into account (AERONET algorithm); if LPs are taken into account (modeling results), heating rate reaches a maximal value of ~0.6°C/day.

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

    NASA Astrophysics Data System (ADS)

    Zhao, Chuanfeng; Garrett, Timothy

    2016-04-01

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

  9. Effect of Aerosols on Surface Radiation and Air Quality in the Central American Region Estimated Using Satellite UV Instruments

    NASA Astrophysics Data System (ADS)

    Bhartia, P. K.; Torres, O.; Krotkov, N. A.

    2007-05-01

    Solar radiation reaching the Earth's surface is reduced by both aerosol scattering and aerosol absorption. Over many parts of the world the latter effect can be as large or larger than the former effect, and small changes in the aerosol single scattering albedo can either cancel the former effect or enhance it. In addition, absorbing aerosols embedded in clouds can greatly reduce the amount of radiation reaching the surface by multiple scattering. Though the potential climatic effects of absorbing aerosols have received considerable attention lately, their effect on surface UV, photosynthesis, and photochemistry can be equally important for our environment and may affect human health and agricultural productivity. Absorption of all aerosols commonly found in the Earth's atmosphere becomes larger in the UV and blue wavelengths and has a relatively strong wavelength dependence. This is particularly true of mineral dust and organic aerosols. However, these effects have been very difficult to estimate on a global basis since the satellite instruments that operate in the visible are primarily sensitive to aerosol scattering. A notable exception is the UV Aerosol Index (AI), first produced using NASA's Nimbus-7 TOMS data. AI provides a direct measure of the effect of aerosol absorption on the backscattered UV radiation in both clear and cloudy conditions, as well as over snow/ice. Although many types of aerosols produce a distinct color cast in the visible images, and aerosols absorption over clouds and snow/ice could, in principle be detected from their color, so far this technique has worked well only in the UV. In this talk we will discuss what we have learned from the long-term record of AI produced from TOMS and Aura/OMI about the possible role of aerosols on surface radiation and air quality in the Central American region.

  10. Analysis of Atmospheric Aerosol Data Sets and Application of Radiative Transfer Models to Compute Aerosol Effects

    NASA Technical Reports Server (NTRS)

    Schmid, Beat

    2005-01-01

    The Bay Area Environmental Research Institute (BAER) scientists have worked with the NASA Ames Research Center sunphotometer group led by Dr. Philip Russell for many years researching the climatic effects of aerosol particles in the stratosphere and troposphere. We have continued to work with the NASA Ames sunphotometer group in research activities representing funded, peer-reviewed proposals to NASA, NOAA and DOE. The activities are described in those proposals and also in the documents provided to the Grants Office earlier. This is the final report from January 1,2002 - June 30, 2005. The report consists of a compilation of 41 peer-reviewed publications (published, in press or submitted) produced under this Cooperative Agreement and 43 first-authored conference presentations. To save paper, reprints are not included but will, of course, be provided upon request.

  11. Direct radiative effects of anthropogenic aerosols on Indian summer monsoon circulation

    NASA Astrophysics Data System (ADS)

    Das, Sushant; Dey, Sagnik; Dash, S. K.

    2016-05-01

    The direct radiative impacts of anthropogenic aerosols on the dynamics of Indian summer monsoon circulation are examined using the regional climate model version 4.1 (RegCM4.1). High anthropogenic aerosol optical depth (AAOD >0.1) and surface shortwave cooling (<-6 W m-2) are simulated over the Indo-Gangetic Basin (IGB), northeast India, east coast of India, and its outflow to the Bay of Bengal (BoB) during the monsoon season (June to September) in the period 2001 to 2010. The analysis reveals a decrease in near surface air temperature at 2 m over the IGB and east coast of India by >0.2 °C due to the dimming effect of anthropogenic aerosols. The aerosol-induced cooling leads to an increase in surface pressure over the local hotspots in the Indian landmass, which reduces the land-sea pressure contrast resulting in weakening of summer monsoon circulation. The simulated surface pressure anomaly also inhibits moisture transport from the BoB towards Indian landmass thereby enhancing precipitation over the BoB and parts of the east coast of India. The impacts are interpreted as conservative estimates because of the underestimation of AAOD by the model due to uncertainties in emission inventory and biases in simulated meteorology. Our results demonstrate the direct radiative impacts of anthropogenic aerosols on the Indian monsoon circulation and call for future studies combining the dynamical and microphysical impacts, which are not considered in this study.

  12. Cloud Scavenging Effects on Aerosol Radiative and Cloud-nucleating Properties - Final Technical Report

    SciTech Connect

    Ogren, John A.; Sheridan, Patrick S.; Andrews, Elisabeth

    2009-03-05

    The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles’ lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.

  13. Radiative effects of tropospheric aerosols on the evolution of the atmospheric boundary layer and its feedback on the haze formation

    NASA Astrophysics Data System (ADS)

    Wei, Chao; Su, Hang; Cheng, Yafang

    2016-04-01

    Planetary boundary layer (PBL) plays a key role in air pollution dispersion and influences day-to-day air quality. Some studies suggest that high aerosol loadings during severe haze events may modify PBL dynamics by radiative effects and hence enhance the development of haze. This study mainly investigates the radiative effects of tropospheric aerosols on the evolution of the atmospheric boundary layer by conducting simulations with Weather Research and Forecasting single-column model (WRF-SCM). We find that high aerosol loading in PBL depressed boundary layer height (PBLH). But the magnitude of the changes of PBLH after adding aerosol loadings in our simulations are small and can't explain extreme high aerosol concentrations observed. We also investigate the impacts of the initial temperature and moisture profiles on the evolution of PBL. Our studies show that the impact of the vertical profile of moisture is comparable with aerosol effects.

  14. Dust aerosol radiative effect and influence on urban atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Chen, M.; Li, L.

    2007-11-01

    An 1.5-level-closure and 3-D non-stationary atmospheric boundary layer (ABL) model and a radiation transfer model with the output of Weather Research and Forecast (WRF) Model and lidar AML-1 are employed to simulate the dust aerosol radiative effect and its influence on ABL in Beijing for the period of 23-26 January 2002 when a dust storm occurred. The simulation shows that daytime dust aerosol radiative effect heats up the ABL at the mean rate of about 0.68 K/h. The horizontal wind speed from ground to 900 m layer is also overall increased, and the value changes about 0.01 m/s at 14:00 LT near the ground. At night, the dust aerosol radiative effect cools the ABL at the mean rate of -0.21 K/h and the wind speed lowers down at about -0.19 m/s at 02:00 LT near the ground.

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  16. How Do Aerosol Radiative Effects Influence Wind? a Sensitivity Study of the Aerosol Impact on the Spatially-Distributed Wind over Europe

    NASA Astrophysics Data System (ADS)

    Baro Esteban, R.; Lorente-Plazas, R.; Jerez, S.; Montavez, J. P.; Jimenez-guerrero, P.

    2014-12-01

    Atmospheric aerosols affect the Earth's climate through their radiative effects, being one of the most uncertain areas in climate modeling. Radiative effects depend mainly on the aerosol optical properties and can be divided into direct and semi-direct effect, produced by the scattering and absorption of radiation; and indirect effect, which influences the aerosols-cloud interactions. Aerosols are widely known to affect radiation, temperature, stability, clouds, and precipitation. However, scientific literature about their effects on wind is scarce. In this sense, the effects of aerosol particles on spatially-distributed winds over Europe are examined. The methodology carried out consists of two WRF-Chem simulations for Europe for the entire year 2010 differing only in the inclusion (or not) of aerosol radiative feedbacks. These simulations have been carried out under the umbrella of the second phase of the AQMEII (Air Quality Model Evaluation International Initiative, http://aqmeii.jrc.ec.europa.eu/). A Euro-CORDEX compliant domain at 0.22º and 23 km resolution has been used. The first simulation does not take into account any aerosol feedbacks (NFB) and the second simulation differs from the base case by the inclusion of direct and indirect radiative feedbacks (FB). Results show that the presence of aerosol generally reduces the wind over Europe. The absorption and scattering of solar radiation by the aerosol particles heat the air and cool the ground temperature leading to an atmospheric stability. This increases the atmospheric stability and decreases the turbulence, as consequence the vertical transfer of momentum diminishes and the surface winds are slower. In addition, the decrease of solar radiation to the ground weakens the thermal circulations, such as land-sea breezes which is more noticeable in the southern of Europe in summer. On the other hand, the indirect effect of the aerosols through their enhancement of clouds also favors a decline of winds

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-05-24

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

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

    NASA Astrophysics Data System (ADS)

    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.

  20. Effects of aerosol from biomass burning on the global radiation budget

    NASA Technical Reports Server (NTRS)

    Penner, Joyce E.; Dickinson, Robert E.; O'Neill, Christine A.

    1992-01-01

    An analysis is made of the likely contribution of smoke particles from biomass burning to the global radiation balance. These particles act to reflect solar radiation directly; they also can act as cloud condensation nuclei, increasing the reflectivity of clouds. Together these effects, although uncertain, may add up globally to a cooling effect as large as 2 watts per square meter, comparable to the estimated contribution to sulfate aerosols. Anthropogenic increases of smoke emission thus may have helped weaken the net greenhouse warming from anthropogenic trace gases.

  1. Factors Affecting Aerosol Radiative Forcing

    NASA Astrophysics Data System (ADS)

    Wang, Jingxu; Lin, Jintai; Ni, Ruijing

    2016-04-01

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

  2. "Investigation of Trends in Aerosol Direct Radiative Effects over North America Using a Coupled Meteorology-Chemistry Model"

    EPA Science Inventory

    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 radi...

  3. Vertical distribution and radiative effects of mineral dust and biomass burning aerosol over West Africa during DABEX

    SciTech Connect

    Johnson, Ben; Heese, B.; McFarlane, Sally A.; Chazette, P.; Jones, A.; Bellouin, N.

    2008-09-12

    This paper presents measurements of the vertical distribution of aerosol extinction coefficient over West Africa, during the Dust and Biomass burning aerosol Experiment (DABEX) / African Monsoon Multidisciplinary Analysis dry season Special Observing period zero (AMMA-SOP0). In situ aircraft measurements from the UK FAAM aircraft are compared with two ground based lidars (POLIS and ARM MPL) and an airborne lidar on an ultra-light aircraft. In general mineral dust was observed at low altitudes (up to 2km) and a mixture of biomass burning aerosol and dust was observed at altitudes of 2-5km. The study exposes difficulties associated with spatial and temporal variability when inter-comparing aircraft and ground measurements. Averaging over many profiles provided a better means of assessing consistent errors and biases associated with in situ sampling instruments and retrievals of lidar ratios. Shortwave radiative transfer calculations and a 3-year simulation with the HadGEM2-A climate model show that the radiative effect of biomass burning aerosol is somewhat sensitive to the vertical distribution of aerosol. Results show a 15% increase in absorption of solar radiation by elevated biomass burning aerosol when the observed low-level dust layer is included as part of the background atmospheric state in the model. This illustrates that the radiative forcing of anthropogenic absorbing aerosol is sensitive to the treatment of other aerosol species and that care is needed in simulating natural aerosols assumed to exist in the pre-industrial, or natural state of the atmosphere.

  4. Multi-decadal Change of Atmospheric Aerosols and their Effect on Surface Radiation

    NASA Technical Reports Server (NTRS)

    Chin, Mian; Diel, Thomas; Streets, David; Wild, Martin; Qian, Yun; Yu, Hongbin; Tan, Qian; Bian, Huisheng; Wang. Weiguo

    2012-01-01

    We present an investigation on multi-decadal changes of atmospheric aerosols and their effects on surface radiation using a global chemistry transport model GOCART along with the near-term to long-term data records. We focus on a 28-year time period of satellite era from 1980 to 2007 during which a suite of aerosol data from satellite observations, ground-based measurements, and intensive field experiments have become available. Particularly: (1) We compare the model calculated clear sky downward radiation at the surface with surface network data from Baseline Surface Radiation Network (BSRN) and CMA (2) We compare the model and surface data with satellite derived downward radiation products from ISCCP and SRB (3) We analyze the long-term global and regional aerosol trends in major anthropogenic source regions (North America, Europe, Asia) that have been experiencing considerable changes of emissions during the three decades, dust and biomass burning regions that have large interannual variability, downwind regions that are directly affected by the changes in the source area, and remote regions that are considered to representing "background" conditions.

  5. Modelled radiative effects of sea spray aerosol using a source function encapsulating wave state

    NASA Astrophysics Data System (ADS)

    Partanen, Antti-Ilari; Dunne, Eimear M.; Bergman, Tommi; Laakso, Anton; Kokkola, Harri; Ovadnevaite, Jurgita; Sogacheva, Larisa; Baisnée, Dominique; Sciare, Jean; Manders, Astrid; O'Dowd, Colin; de Leeuw, Gerrit; Korhonen, Hannele

    2014-05-01

    Sea spray aerosol particles have significant effects on global climate by scattering solar radiation (direct effect) and modifying cloud properties (indirect effect). Sea spray consists mainly of sea salt, but in biologically active regions, major fraction of sea spray may come in the form of primary marine organic matter (PMOM). Traditionally, sea spray flux has been parameterized in global models in terms of wind speed, and organic fraction of sea spray in terms of chlorophyll-a concentration. In this study, we have incorporated recently developed parameterizations for the sea spray aerosol source flux into the global aerosol-climate model ECHAM-HAMMOZ. The parameterizations encapsulate the wave state via Reynolds number, and predict the organic fraction of the sea spray aerosol source flux. The model was then used to investigate the direct and indirect effects of sea spray aerosol particles. We compared simulated sea spray concentrations with in-situ measurements from Mace Head (North Atlantic), Point Reyes (North Pacific), and Amsterdam Island (Southern Indian Ocean). Aerosol optical depth (AOD) was compared with satellite measurements from PARASOL. Modelled annual mean global emissions of sea salt and PMOM were 805 Tg yr-1 (uncertainty range of 378-1233 Tg yr-1) and 1.1 Tg yr-1 (0.5-1.8 Tg yr-1), respectively. Sea salt emissions were considerably lower than the majority of previous estimates, but PMOM was in the range of previous studies. The model captured sea salt concentrations fairly well in the smaller size ranges at Mace Head (annual normalized mean bias of -13% for particles with vacuum aerodynamic diameter Dva

  6. Multi-Decadal Change of Atmospheric Aerosols and Their Effect on Surface Radiation

    NASA Technical Reports Server (NTRS)

    Chin, Mian; Diehl, Thomas; Tan, Qian; Wild, Martin; Qian, Yun; Yu, Hongbin; Bian, Huisheng; Wang, Weiguo

    2012-01-01

    We present an investigation on multi-decadal changes of atmospheric aerosols and their effects on surface radiation using a global chemistry transport model along with the near-term to long-term data records. We focus on a 28-year time period of satellite era from 1980 to 2007, during which a suite of aerosol data from satellite observations and ground-based remote sensing and in-situ measurements have become available. We analyze the long-term global and regional aerosol optical depth and concentration trends and their relationship to the changes of emissions" and assess the role aerosols play in the multi-decadal change of solar radiation reaching the surface (known as "dimming" or "brightening") at different regions of the world, including the major anthropogenic source regions (North America, Europe, Asia) that have been experiencing considerable changes of emissions, dust and biomass burning regions that have large interannual variabilities, downwind regions that are directly affected by the changes in the source area, and remote regions that are considered to representing "background" conditions.

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

    SciTech Connect

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

    2013-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

  9. Radiative Effects of Carbonaceous and Inorganic Aerosols over California during CalNex and CARES: Observations versus Model Predictions

    NASA Astrophysics Data System (ADS)

    Vinoj, V.; Fast, J. D.; Liu, Y.

    2012-12-01

    Aerosols have been identified to be a major contributor to the uncertainty in understanding the present climate. Most of this uncertainty arises due to the lack of knowledge of their micro-physical and chemical properties as well as how to adequately represent their spatial and temporal distributions. Increased process level understanding can be achieved through carefully designed field campaigns and experiments. These measurements can be used to elucidate the aerosol properties, mixing, transport and transformation within the atmosphere and also to validate and improve models that include meteorology-aerosol-chemistry interactions. In the present study, the WRF-Chem model is used to simulate the evolution of carbonaceous and inorganic aerosols and their impact on radiation during May and June of 2010 over California when two field campaigns took place: the California Nexus Experiment (CalNex) and Carbonaceous Aerosol and Radiative Effects Study (CARES). We merged CalNex and CARES data along with data from operational networks such as, California Air Resources Board (CARB's) air quality monitoring network, the Interagency Monitoring of Protected Visual Environments (IMPROVE) network, the AErosol RObotic NETwork (AERONET), and satellites into a common dataset for the Aerosol Modeling Test bed. The resulting combined dataset is used to rigorously evaluate the model simulation of aerosol mass, size distribution, composition, and optical properties needed to understand uncertainties that could affect regional variations in aerosol radiative forcing. The model reproduced many of the diurnal, multi-day, and spatial variations of aerosols as seen in the measurements. However, regionally the performance varied with reasonably good agreement with observations around Los Angeles and Sacramento and poor agreement with observations in the vicinity of Bakersfield (although predictions aloft were much better). Some aerosol species (sulfate and nitrate) were better represented

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

    NASA Astrophysics Data System (ADS)

    Chubarova, N.; Nezval', Y.; Sviridenkov, M.; Smirnov, A.; Slutsker, I.

    2011-10-01

    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 and Zvenigorod (Moscow suburb) and radiative measurements in Moscow. Volume aerosol size distribution in smoke conditions was shown to have a bimodal character with the significant prevalence of fine mode aerosol particles which effective radius shifted to higher values (reff-fine = 0.24 μm against approximately 0.15 μm in typical conditions). Imaginary part of refractive index in visible region was characterized by lower values compared with typical conditions (REFI = 0.006 against REFI = 0.01) and single scattering albedo (SSA) was significantly higher (SSAλ=675nm = 0.95 against SSAλ=675nm ~ 0.9). Extremely high daily average AOT's were observed on 6-8 August reaching the absolute maximum on 7 August up to AOT500 = 6.4 in Moscow and AOT500 = 5.9 at Zvenigorod. A dramatic attenuation of solar irradiance at ground in cloudless but smoky conditions was also observed. Maximum irradiance loss has reached 64% for global shortwave irradiance, 91% for UV radiation 300-380 nm and 97% for erythemally-weighted UV irradiance even at relatively high solar elevation due to extremely high AOT and smaller SSA values in UV (0.8-0.9) compared with SSA in 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 while climatological RFE calculated for monthly mean AOT in August 2010 was about -65 Wm-2 compared with -20 Wm-2 for typical aerosol conditions according to the 10 year period of measurements in Moscow.

  11. Simulation of bulk aerosol direct radiative effects and its climatic feedbacks in South Africa using RegCM4

    NASA Astrophysics Data System (ADS)

    Tesfaye, M.; Botai, J.; Sivakumar, V.; Mengistu Tsidu, G.; Rautenbach, C. J. deW.; Moja, Shadung J.

    2016-05-01

    In this study, 12 year runs of the Regional Climate Model (RegCM4) have been used to analyze the bulk aerosol radiative effects and its climatic feedbacks in South Africa. Due to the geographical locations where the aerosol potential source regions are situated and the regional dynamics, the South African aerosol spatial-distribution has a unique feature. Across the west and southwest areas, desert dust particles are dominant. However, sulfate and carbonaceous aerosols are primarily distributed over the east and northern regions of the country. Analysis of the Radiative Effects (RE) shows that in South Africa the bulk aerosols play a role in reducing the net radiation absorbed by the surface via enhancing the net radiative heating in the atmosphere. Hence, across all seasons, the bulk aerosol-radiation-climate interaction induced statistically significant positive feedback on the net atmospheric heating rate. Over the western and central parts of South Africa, the overall radiative feedbacks of bulk aerosol predominantly induces statistically significant Cloud Cover (CC) enhancements. Whereas, over the east and southeast coastal areas, it induces minimum reductions in CC. The CC enhancement and RE of aerosols jointly induce radiative cooling at the surface which in turn results in the reduction of Surface Temperature (ST: up to -1 K) and Surface Sensible Heat Flux (SSHF: up to -24 W/m2). The ST and SSHF decreases cause a weakening of the convectively driven turbulences and surface buoyancy fluxes which lead to the reduction of the boundary layer height, surface pressure enhancement and dynamical changes. Throughout the year, the maximum values of direct and semi-direct effects of bulk aerosol were found in areas of South Africa which are dominated by desert dust particles. This signals the need for a strategic regional plan on how to reduce the dust production and monitoring of the dust dispersion as well as it initiate the need of further research on different

  12. Effects of aerosol optical properties on deep convective clouds and radiative forcing

    SciTech Connect

    Fan, Jiwen; Zhang, Renyi; Tao, Wei-Kuo; Mohr, Karen I

    2008-04-23

    The aerosol radiative effects (ARE) on the deep convective clouds are investigated by using a spectral-bin cloud-resolving model coupled with a radiation scheme and an explicit land surface model. The sensitivity of cloud properties and the associated radiative forcing to aerosol single-scattering albedo (SSA) are examined. The ARE on cloud properties is pronounced for mid-visible SSA of 0.85. Relative to the case without ARE, the cloud fraction and optical depth decrease by about 18% and 20%, respectively. Ice particle number concentrations, liquid water path, ice water path, and droplet size decrease by more than 15% when the ARE is introduced. The ARE causes a surface cooling of about 0.35 K and significantly high heating rates in the lower troposphere (about 0.6 K day-1 higher at 2 km), both of which lead to a more stable atmosphere and hence weaker convection. The weaker convection explains the less cloudiness, lower cloud optical depth, less LWP and IWP, smaller droplet size, and less precipitation resulting from the ARE. The daytime-mean direct forcing induced by black carbon is about 2.2 W m-2 at the top of atmosphere (TOA) and -17.4 W m-2 at the surface for SSA of 0.85. The semi-direct forcing is positive, about 10 and 11.2 W m-2 at the TOA and surface, respectively. Both the TOA and surface total radiative forcing values are strongly negative for the deep convective clouds, attributed mostly to aerosol indirect forcing. Aerosol direct and semi-direct effects are very sensitive to SSA when aerosol optical depth is high. Because the positive semi-direct forcing compensates the negative direct forcing at the surface, the surface temperature and heat fluxes decrease less significantly with the increase of aerosol absorption (decreasing SSA). The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable atmosphere due to enhanced

  13. Effects of aerosol optical properties on deep convective clouds and radiative forcing

    NASA Astrophysics Data System (ADS)

    Fan, Jiwen; Zhang, Renyi; Tao, Wei-Kuo; Mohr, Karen I.

    2008-04-01

    The aerosol radiative effects (ARE) on the deep convective clouds are investigated by using a spectral-bin cloud-resolving model coupled with a radiation scheme and an explicit land surface model. The sensitivity of cloud properties and the associated radiative forcing to aerosol single-scattering albedo (SSA) are examined. The ARE on cloud properties is pronounced for mid-visible SSA of 0.85. Relative to the case without ARE, the cloud fraction and optical depth decrease by about 18% and 20%, respectively. Ice particle number concentrations, liquid water path, ice water path, and droplet size decrease by more than 15% when the ARE is introduced. The ARE causes a surface cooling of about 0.35 K and significantly high heating rates in the lower troposphere (about 0.6 K day-1 higher at 2 km), both of which lead to a more stable atmosphere and hence weaker convection. The weaker convection explains the less cloudiness, lower cloud optical depth, less LWP and IWP, smaller droplet size, and less precipitation resulting from the ARE. The daytime-mean direct forcing induced by black carbon is about 2.2 W m-2 at the top of atmosphere (TOA) and -17.4 W m-2 at the surface for SSA of 0.85. The semi-direct forcing is positive, about 10 and 11.2 W m-2 at the TOA and surface, respectively. Both the TOA and surface total radiative forcing values are strongly negative for the deep convective clouds, attributed mostly to aerosol indirect forcing. Aerosol direct and semi-direct effects are very sensitive to SSA when aerosol optical depth is high. Because the positive semi-direct forcing compensates the negative direct forcing at the surface, the surface temperature and heat fluxes decrease less significantly with the increase of aerosol absorption (decreasing SSA). The cloud fraction, optical depth, convective strength, and precipitation decrease with the increase of absorption, resulting from a more stable atmosphere due to enhanced surface cooling and atmospheric heating.

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

    NASA Astrophysics Data System (ADS)

    Chubarova, N.; Nezval', Ye.; Sviridenkov, I.; Smirnov, A.; Slutsker, I.

    2012-03-01

    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 the 10 yr period of measurements in Moscow.

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

    NASA Astrophysics Data System (ADS)

    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

  16. Observed aerosol-induced radiative effect on plant productivity in the eastern United States

    NASA Astrophysics Data System (ADS)

    Strada, S.; Unger, N.; Yue, X.

    2015-12-01

    We apply satellite observations of aerosol optical depth (AOD) in conjunction with flux tower-derived estimates of gross primary productivity (GPP) to probe the relationship between atmospheric aerosol loading and carbon uptake rate at 10 select sites (4 deciduous broadleaf, 3 cropland, 1 evergreen needle leaf, 1 mixed forest and 1 grassland) on hourly time scales in the growing season in the eastern United States. For deciduous and mixed forests, the aerosol light scattering increases GPP with a maximum effect observed under polluted conditions (AOD >0.6), when diffuse radiation is 40-60%. During midday hours, high AOD conditions (>0.4) enhance plant productivity by ∼13% in deciduous forests. In contrast, we find that high diffuse light fraction does not increase the carbon uptake rate in croplands and grasslands; for these ecosystems, we estimate that high AOD conditions reduce GPP by ∼17% during midday hours. Our findings are consistent with previous studies that have attributed these contrasting response sensitivities to the complex and closed canopy architecture of forests versus crops and grasslands. C4 but not C3 crops may benefit from pollution-induced changes in diffuse and direct light. Further research is needed to investigate the role of local meteorology as a possible confounder in the connection between atmospheric aerosols and plant productivity.

  17. SILAM and MACC reanalysis aerosol data used for simulating the aerosol direct radiative effect with the NWP model HARMONIE for summer 2010 wildfire case in Russia

    NASA Astrophysics Data System (ADS)

    Toll, V.; Reis, K.; Ots, R.; Kaasik, M.; Männik, A.; Prank, M.; Sofiev, M.

    2015-11-01

    Persistent high pressure conditions over the European part of Russia during summer 2010 were responsible for an extended period of hot and dry weather, creating favourable conditions for severe wildfires. The chemical transport model SILAM is used to simulate the dispersion of smoke aerosol for this case. Aerosol fields from SILAM are compared to the Monitoring Atmospheric Composition and Climate (MACC) reanalysis. Moreover, the model output is compared to in situ and remote sensing measurements, paying particular attention to the most intense fire period of August 7 to 9, when the plume reached the Baltic countries and Finland. The maximum observed aerosol optical depth was more than 4 at 550 nm during this time. The aerosol distributions from the SILAM run and the MACC reanalysis are subsequently used in meteorological simulations using the Hirlam Aladin Research for Mesoscale Operational Numerical Weather Prediction in Euromed (HARMONIE) model. The modelling results show a significant reduction of the daily average shortwave radiation fluxes at the surface (up to 125 W/m2) and daily average near-surface temperature (up to 4 °C) through the aerosol direct radiative effect. The simulated near-surface temperature and vertical temperature profile agree better with the observations, when the aerosol direct radiative effect is considered in the meteorological simulation. The boundary layer is more stably stratified, creating poorer dispersion conditions for the smoke.

  18. Radiative impact of atmospheric aerosols and clouds

    NASA Astrophysics Data System (ADS)

    Wong, Jeff

    1998-11-01

    The effect of aerosols and clouds on Earth's shortwave radiation budget is studied in this thesis. An expression for the global annual mean radiative forcing due to sulfate aerosols is extended for absorbing aerosols using a two-stream approximation. This expression depends on the backscattering fraction of the aerosol which varies with the effective radius of the aerosol size distribution. This variation leads to a factor of 2.0 variation in the radiative forcing of slightly absorbing aerosols. Water vapor condenses onto hygroscopic aerosols which results in a change in size and a change in the concentration of the chemical components of the aerosol. The original Köhler equation accurately describes the equilibrium size of a hygroscopic aerosol. Use of the modified Köhler equation leads to errors due to its thermodynamically inconsistent nature. On a global annual average, the direct radiative forcing of hygroscopic sulfate aerosol is -0.69 W m-2. Over highly polluted regions, the local radiative forcing can be as high as -7 W m-2 which is comparable to the forcing due to increased greenhouse gas concentrations. Using a plane-parallel model, an analytical expression is derived for the cloud radiative forcing ratio which is used as a measure of enhanced shortwave radiation absorption of clouds. With this model, high values of this ratio can be achieved by thick clouds with absorptances of approximately 0.3. High values of the ratio can also be obtained with low level clouds if the transmittance of the atmosphere above the cloud is reduced to approximately 0.8. This can be achieved by a high concentration of strongly absorbing aerosols.

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

    NASA Astrophysics Data System (ADS)

    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.

  20. Thermal Infrared Radiative Forcing By Atmospheric Aerosol

    NASA Astrophysics Data System (ADS)

    Adhikari, Narayan

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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed Central

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

    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, 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. PMID:26831092

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  4. Combined multispectral/hyperspectral remote sensing of tropospheric aerosols for quantification of their direct radiative effect

    NASA Astrophysics Data System (ADS)

    McGarragh, Gregory R.

    Scattering and absorption of solar radiation by aerosols in the atmosphere has a direct radiative effect on the climate of the Earth. Unfortunately, according to the IPCC the uncertainties in aerosol properties and their effect on the climate system represent one of the largest uncertainties in climate change research. Related to aerosols, one of the largest uncertainties is the fraction of the incident radiation that is scattered rather than absorbed, or their single scattering albedo. In fact, differences in single scattering albedo have a significant impact on the magnitude of the cooling effect of aerosols (opposite to that of greenhouse gasses) which can even have a warming effect for strongly absorbing aerosols. Satellites provide a unique opportunity to measure aerosol properties on a global scale. Traditional approaches use multispectral measurements of intensity at a single view angle to retrieve at most two aerosol parameters over land but it is being realized that more detail is required for accurate quantification of the direct effect of aerosols, in particular its anthropogenic component, and therefore more measurement information is required. One approach to more advanced measurements is to use not only intensity measurements but also polarimetric measurements and to use multiple view angles. In this work we explore another alternative: the use of hyperspectral measurements in molecular absorption bands. Our study can be divided into three stages the first of which is the development of a fast radiative transfer model for rapid simulation of measurements. Our approach is matrix operator based and uses the Pade approximation for the matrix exponential to evaluate the homogeneous solution. It is shown that the method is two to four times faster than the standard and efficient discrete ordinate technique and is accurate to the 6th decimal place. The second part of our study forms the core and is divided into two chapters the first of which is a rigorous

  5. Application of Satellite and Ground-based Data to Investigate the UV Radiative Effects of Australian Aerosols

    NASA Technical Reports Server (NTRS)

    Kalashnikova, Olga V.; Mills, Franklin P.; Eldering, Annmarie; Anderson, Don

    2007-01-01

    An understanding of the effect of aerosols on biologically- and photochemically-active UV radiation reaching the Earth's surface is important for many ongoing climate, biophysical, and air pollution studies. In particular, estimates of the UV characteristics of the most common Australian aerosols will be valuable inputs to UV Index forecasts, air quality studies, and assessments of the impact of regional environmental changes. By analyzing climatological distributions of Australian aerosols we have identified sites where co-located ground-based UV-B and ozone measurements were available during episodes of relatively high aerosol activity. Since at least June 2003, surface UV global irradiance spectra (285-450 nm) have been measured routinely at Darwin and Alice Springs in Australia by the Australian Bureau of Meteorology (BoM). Using colocated sunphotometer measurements at Darwin and Alice Springs, we identified several episodes of relatively high aerosol activity. Aerosol air mass types were analyzed from sunphotometer-derived angstrom parameter, MODIS fire maps and MISR aerosol property retrievals. To assess aerosol effects we compared the measured UV irradiances for aerosol-loaded and clear-sky conditions with each other and with irradiances simulated using the libRadtran radiative transfer model for aerosol-free conditions. We found that for otherwise similar atmospheric conditions, smoke aerosols over Darwin reduced the surface UV irradiance by as much as 40-50% at 290-300 nm and 20-25% at 320-400 nm near active fires (aerosol optical depth, AOD, at 500 nm approximately equal to 0.6). Downwind of fires, the smoke aerosols over Darwin reduced the surface irradiance by 15-25% at 290-300 nm and approximately 10% at 320-350 nm (AOD at 500 nm approximately equal to 0.2). The effect of smoke increased with decrease of wavel strongest in the UV-B. The aerosol attenuation factors calculated for the selected cases suggest smoke over Darwin has an effect on surface 340

  6. Deriving Radiative Effects of Aerosol-Immersed Broken Cloud Fields from Multi-spectral Imagery

    NASA Astrophysics Data System (ADS)

    Schmidt, Sebastian

    2016-04-01

    Recently, significant progress has been made in the understanding of cloud inhomogeneity effects in shortwave passive remote sensing. Yet it has proven difficult to correct such effects on the pixel level using multi-spectral imagery alone, mainly because three-dimensional (3D) radiative transfer in cloud fields is a non-local phenomenon. As a result, estimates of irradiance - the fundamental climate variable - from space-or air-borne imagery continue to pose problems for complex cloud fields. The presence of aerosols in the vicinity of clouds exacerbates the prob- lem. I will show evidence from field experiments and 3D radiative transfer calculations that biases may exceed 40% at the pixel level at the MODIS spatial resolution, and that some of these effects "survive" spatial averaging. A new way to cope with this problem is the discovery that 3D effects manifest themselves as spectral perturba- tion in reflected radiances and in the associated irradiance fields throughout an inhomogeneous cloud domain. In parameterized form, these correlations between spatial cloud distribution and spectral signature can be used to de- rive first-order inhomogeneity corrections for irradiance fields - not on a pixel basis, but for populations of pixels within a cloud domain represented by probability density functions. I will present the first practical approach for using these new findings in a future proxy-3D algorithm for deriving irradiances below and above cloud-aerosol fields from multi-spectral imagers, and discuss the accuracy that can be expected from this simplified method to account for 3D effects in mixed aerosol-cloud scenes.

  7. Assessment of aerosol optical property and radiative effect for the layer decoupling cases over the northern South China Sea during the 7-SEAS/Dongsha Experiment

    NASA Astrophysics Data System (ADS)

    Pani, Shantanu Kumar; Wang, Sheng-Hsiang; Lin, Neng-Huei; Tsay, Si-Chee; Lolli, Simone; Chuang, Ming-Tung; Lee, Chung-Te; Chantara, Somporn; Yu, Jin-Yi

    2016-05-01

    The aerosol radiative effect can be modulated by the vertical distribution and optical properties of aerosols, particularly when aerosol layers are decoupled. Direct aerosol radiative effects over the northern South China Sea (SCS) were assessed by incorporating an observed data set of aerosol optical properties obtained from the Seven South East Asian Studies (7-SEAS)/Dongsha Experiment into a radiative transfer model. Aerosol optical properties for a two-layer structure of aerosol transport were estimated. In the radiative transfer calculations, aerosol variability (i.e., diversity of source region, aerosol type, and vertical distribution) for the complex aerosol environment was also carefully quantified. The column-integrated aerosol optical depth (AOD) at 500 nm was 0.1-0.3 for near-surface aerosols and increased 1-5 times in presence of upper layer biomass-burning aerosols. A case study showed the strong aerosol absorption (single-scattering albedo (ω) ≈ 0.92 at 440 nm wavelength) exhibited by the upper layer when associated with predominantly biomass-burning aerosols, and the ω (≈0.95) of near-surface aerosols was greater than that of the upper layer aerosols because of the presence of mixed type aerosols. The presence of upper level aerosol transport could enhance the radiative efficiency at the surface (i.e., cooling) and lower atmosphere (i.e., heating) by up to -13.7 and +9.6 W m-2 per AOD, respectively. Such enhancement could potentially modify atmospheric stability, can influence atmospheric circulation, as well as the hydrological cycle over the tropical and low-latitude marginal northern SCS.

  8. From nuclear power to coal power: Aerosol-induced health and radiative effects

    NASA Astrophysics Data System (ADS)

    Mielonen, Tero; Laakso, Anton; Karhunen, Anni; Kokkola, Harri; Partanen, Antti-Ilari; Korhonen, Hannele; Romakkaniemi, Sami; Lehtinen, Kari E. J.

    2015-12-01

    We have investigated what would be the climate and PM-induced air quality consequences if all nuclear reactors worldwide were closed down and replaced by coal combustion. In a way, this presents a "worst-case scenario" since less polluting energy sources are available. We studied simultaneously the radiative and health effects of coal power emissions using a global 3-D aerosol-climate model (ECHAM-HAMMOZ). This approach allowed us to estimate the effects of a major global energy production change from low carbon source to a high carbon one using detailed spatially resolved population density information. We included the radiative effects of both CO2 and PM2.5 but limited the study of health effects to PM2.5 only. Our results show that the replacement of nuclear power with coal power would have globally caused an average of 150,000 premature deaths per year during the period 2005-2009 with two thirds of them in Europe. For 37 years the aerosol emissions from the additional coal power plants would cool the climate but after that the accumulating CO2 emissions would accelerate the warming of the climate.

  9. Total ozone column, aerosol optical depth and precipitable water effects on solar erythemal ultraviolet radiation recorded in Malta.

    NASA Astrophysics Data System (ADS)

    Bilbao, Julia; Román, Roberto; Yousif, Charles; Mateos, David; Miguel, Argimiro

    2013-04-01

    The Universities of Malta and Valladolid (Spain) developed a measurement campaign, which took place in the Institute for Energy Technology in Marsaxlokk (Southern Malta) between May and October 2012, and it was supported by the Spanish government through the Project titled "Measurement campaign about Solar Radiation, Ozone, and Aerosol in the Mediterranean area" (with reference CGL2010-12140-E). This campaign provided the first ground-based measurements in Malta of erythemal radiation and UV index, which indicate the effectiveness of the sun exposure to produce sunburn on human skin. A wide variety of instruments was involved in the campaign, providing a complete atmospheric characterization. Data of erythemal radiation and UV index (from UVB-1 pyranometer), total shortwave radiaton (global and diffuse components from CM-6B pyranometers), and total ozone column, aerosol optical thickness, and precitable water column (from a Microtops-II sunphotometer) were available in the campaign. Ground-based and satellite instruments were used in the analysis, and several intercomparisons were carried out to validate remote sensing data. OMI, GOME, GOME-2, and MODIS instruments, which provide data of ozone, aerosol load and optical properties, were used to this end. The effects on solar radiation, ultraviolet and total shortwave ranges, of total ozone column, aerosol optical thickness and precipitable water column were obtained using radiation measurements at different fixed solar zenith angles. The empirical results shown a determinant role of the solar position, a negligible effect of ozone on total shortwave radiation, and a stronger attenuation provided by aerosol particles in the erythemal radiation. A variety of aerosol types from different sources (desert dust, biomass burning, continental, and maritime) reach Malta, in this campaign several dust events from the Sahara desert occurred and were analyzed establishing the air mass back-trajectories ending at Malta at

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Modeling of growth and evaporation effects on the extinction of 1.0-micron solar radiation traversing stratospheric sulfuric acid aerosols

    NASA Technical Reports Server (NTRS)

    Yue, G. K.; Deepak, A.

    1981-01-01

    The effects of growth and evaporation of stratospheric sulfuric acid aerosols on the extinction of solar radiation traversing such an aerosol medium are reported for the case of 1.0-micron solar radiation. Modeling results show that aerosol extinction is not very sensitive to the change of ambient water vapor concentration, but is sensitive to ambient temperature changes, especially at low ambient temperatures and high ambient water vapor concentration. A clarification is given of the effects of initial aerosol size distribution and composition on the change of aerosol extinction due to growth and evaporation processes. It is shown that experiments designed to observe solar radiation extinction of aerosols may also be applied to the determination of observed changes in aerosol optical properties, environmental parameters, or the physical and optical characteristics of sulfate aerosols.

  12. The Effects of Aerosol on Atmospheric UV Radiation: Measurements and Modeling from the MILAGRO Field Campaign

    NASA Astrophysics Data System (ADS)

    Madronich, S.; Hall, S.; Shetter, R.; Slusser, J.; Arnott, P.

    2007-05-01

    The MILAGRO field campaign took place in and near Mexico City 1-30 March 2006. A comprehensive data set was obtained on atmospheric chemical composition (gas and aerosol), aerosol microphysics, spectral radiation, and meteorology from surface-, aircraft-, and satellite-based instruments. For much of this time, the lower atmosphere was laden with large amounts of aerosols originating from urban and industrial sources, biomass fires, and wind-blown dust. Spectral radiation measurements are available from filter radiometers and spectroradiometers, and span ultraviolet (UV) wavelengths important to surface biota and tropospheric photochemistry. By combining the spectral radiation measurements, aerosol composition, optical, and microphysical measurements, and modeling, an assessment is now possible on how aerosols affect surface UV radiation (e.g. DNA damage, erythema, vitamin-D production) and vertical profiles of photolysis frequencies (e.g. JNO2, JO3(O1D), JCH2O, JHONO). Interactions between aerosol-scattered radiation and absorption by gaseous pollutants (esp. O3, SO2, and NO2) can also be evaluated. Implications for human health and photochemical oxidant formation will be discussed.

  13. Combined multispectral/hyperspectral remote sensing of tropospheric aerosols for quantification of their direct radiative effect

    NASA Astrophysics Data System (ADS)

    McGarragh, Gregory R.

    Scattering and absorption of solar radiation by aerosols in the atmosphere has a direct radiative effect on the climate of the Earth. Unfortunately, according to the IPCC the uncertainties in aerosol properties and their effect on the climate system represent one of the largest uncertainties in climate change research. Related to aerosols, one of the largest uncertainties is the fraction of the incident radiation that is scattered rather than absorbed, or their single scattering albedo. In fact, differences in single scattering albedo have a significant impact on the magnitude of the cooling effect of aerosols (opposite to that of greenhouse gasses) which can even have a warming effect for strongly absorbing aerosols. Satellites provide a unique opportunity to measure aerosol properties on a global scale. Traditional approaches use multispectral measurements of intensity at a single view angle to retrieve at most two aerosol parameters over land but it is being realized that more detail is required for accurate quantification of the direct effect of aerosols, in particular its anthropogenic component, and therefore more measurement information is required. One approach to more advanced measurements is to use not only intensity measurements but also polarimetric measurements and to use multiple view angles. In this work we explore another alternative: the use of hyperspectral measurements in molecular absorption bands. Our study can be divided into three stages the first of which is the development of a fast radiative transfer model for rapid simulation of measurements. Our approach is matrix operator based and uses the Pade approximation for the matrix exponential to evaluate the homogeneous solution. It is shown that the method is two to four times faster than the standard and efficient discrete ordinate technique and is accurate to the 6th decimal place. The second part of our study forms the core and is divided into two chapters the first of which is a rigorous

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    The Weather Research and Forecasting model with Chemistry (WRF-Chem) has been used to simulate a region of Brazil heavily influenced by biomass burning. Nested simulations were run at 5 and 1 km horizontal grid spacing for three case studies in September 2012. Simulations were run with and without fire emissions, convective parameterisation on the 5 km domain, and aerosol-radiation interactions in order to explore the differences attributable to the parameterisations and to better understand the aerosol direct effects and cloud responses. Direct aerosol-radiation interactions due to biomass burning aerosol resulted in a net cooling, with an average short-wave direct effect of -4.08 ± 1.53 Wm-2. However, around 21.7 Wm-2 is absorbed by aerosol in the atmospheric column, warming the atmosphere at the aerosol layer height, stabilising the column, inhibiting convection, and reducing cloud cover and precipitation. The changes to clouds due to radiatively absorbing aerosol (traditionally known as the semi-direct effects) increase the net short-wave radiation reaching the surface by reducing cloud cover, producing a secondary warming that counters the direct cooling. However, the magnitude of the semi-direct effect was found to be extremely sensitive to the model resolution and the use of convective parameterisation. Precipitation became organised in isolated convective cells when not using a convective parameterisation on the 5 km domain, reducing both total cloud cover and total precipitation. The SW semi-direct effect varied from 6.06 ± 1.46 with convective parameterisation to 3.61 ± 0.86 Wm-2 without. Convective cells within the 1 km domain are typically smaller but with greater updraft velocity than equivalent cells in the 5 km domain, reducing the proportion of the domain covered by cloud in all scenarios and producing a smaller semi-direct effect. Biomass burning (BB) aerosol particles acted as cloud condensation nuclei (CCN), increasing the droplet number

  15. Direct effect of aerosol on incident solar radiation at the surface as a function of aerosol mixtures measured in the center of Rome.

    NASA Astrophysics Data System (ADS)

    Campanelli, M.; Bassani, C.; Cacciani, M.; Siani, A. M.; Perrino, C.; Canepari, S.; Di Sarra, A.; Salzano, R.; Casasanta, G. P.; Tirelli, C.; Estelles, V.

    2012-04-01

    Aerosols determine a radiative effect in the atmosphere by affecting the amount of solar radiation reaching the surface and then acting on the temperature of both the layer where they are located and the surface. The presence of very absorbent particles typical of the urban environment, is therefore dangerous not only for human health but also because they are able to increase the temperature of the atmospheric layer in which they are located interacting with the "heath island" phenomenon. The resulting variation of both surface temperature and temperature vertical profile influences the dilution of atmospheric pollutants and needs to be studied in more detail, particularly in the summer period when heat waves are more frequent. Chemical analysis of surface particulate matter performed at the urban site of Rome (Perrino et al. 2009) showed that sea salt, locally produced urban aerosol and desert dust can be recognized depending on the intensity of the episodes transporting different particles types. As a result: i) the direct effect of aerosol at the surface change as a function of aerosol mixtures; ii) the variation of incident solar radiation affects the local convective air motion modifying the low level circulation and having an effect on the particles deposition and hence on the chemical characterization of the mixture. On the base of above issues a day-time intensive field campaign was held in Rome (Italy) in June and July 2011 at the University of Rome, La Sapienza, located in the city center (lat 41.9°N, long 12.5 °E). Chemical analysis of the aerosol particles was performed on particulate collected by PM10 collectors. Columnar aerosol optical and physical properties in clear sky were retrieved by using a PREDE sun-sky radiometer, part of ESR/SKYNET network. Vertical profiles of aerosol were obtained by a Lidar and incoming total solar radiation was measured by a Black and White Pyranometer . A Brewer spectrophotometer, a Sodar, and a MFRSR provided

  16. Study Of The Effects Of Aerosol And Ozone On The Ultraviolet Radiation In The Mediterranean By Means Of Measurements And Radiation Transfer Model

    NASA Astrophysics Data System (ADS)

    Meloni, D.; di Sarra, A.; Cacciani, M.; di Iorio, T.; Fiocco, G.; Junkermann, W.; Deluisi, J.

    During the Photochemical Activity and Solar Ultraviolet Radiation modulation fac- tors II (PAUR II) campaign an articulated set of measurements of ultraviolet radia- tion, aerosol properties, and atmospheric chemical composition was collected in the Mediterranean. Measurements of UV and visible irradiance, ozone and aerosol were performed also at the island of Lampedusa (35.5 N, 12.6 E) in May-June 1999. Sev- eral Saharan dust events occurred during the PAUR II campaign, and large aerosol amounts were detected over Lampedusa in different occasions. A radiative transfer model has been used to investigate the role of ozone and aerosols in modulating UV irradiance and to reproduce the UV spectra measured by the Brewer spectrophotometer in cloud-free conditions. The model is initialized with a large set of observations, allowing a detailed characterization of the atmospheric properties. Particular efforts have been devoted to reconstruct the aerosol distribution and optical properties. The combined used of the measured spectra and of the radiation transfer model allows an estimate of the aerosol refractive index, of the UV radiative forcing due to aerosol, and of the effects of different vertical distributions of ozone.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  18. Aerosols over Delhi during pre-monsoon months: Characteristics and effects on surface radiation forcing

    NASA Astrophysics Data System (ADS)

    Singh, Sachchidanand; Nath, Shambhu; Kohli, Ramesh; Singh, Risal

    2005-07-01

    The surface fluxes in the wavelength range 280-2800 nm were measured during the pre-monsoon period, April-June 2003 along with the spectral distribution of aerosol optical depth (AOD) in the visible and near infrared wavelengths. The Ångström exponent alpha retrieved from the data showed abundance of desert aerosols over Delhi during this period. The aerosol composition constructed using the OPAC model indicated a typical mixture of two aerosol types: urban and desert. Due to this the aerosol mixture had a very low value of single scattering albedo ~0.67. The average total radiative forcing efficiency observed at the surface in the broad wavelength band (280-2800 nm) was estimated and compared with the SBDART model calculated values.

  19. Simultaneous retrieval of aerosol properties and clear-sky direct radiative effect over the global ocean from MODIS

    NASA Astrophysics Data System (ADS)

    Lee, Jaehwa; Kim, Jhoon; Lee, Yun Gon

    2014-08-01

    A unified satellite algorithm is presented to simultaneously retrieve aerosol properties (aerosol optical depth; AOD and aerosol type) and clear-sky shortwave direct radiative effect (hereafter, DREA) over ocean. The algorithm is applied to Moderate Resolution Imaging spectroradiometer (MODIS) observations for a period from 2003 to 2010 to assess the DREA over the global ocean. The simultaneous retrieval utilizes lookup table (LUT) containing both spectral reflectances and solar irradiances calculated using a single radiative transfer model with the same aerosol input data. This study finds that aerosols cool the top-of-atmosphere (TOA) and bottom-of-atmosphere (BOA) by 5.2 ± 0.5 W/m2 and 8.3 W/m2, respectively, and correspondingly warm the atmosphere (hereafter, ATM) by 3.1 W/m2. These quantities, solely based on the MODIS observations, are consistent with those of previous studies incorporating chemical transport model simulations and satellite observations. However, the DREAs at BOA and ATM are expected to be less accurate compared to that of TOA due to low sensitivity in retrieving aerosol type information, which is related with the atmospheric heating by aerosols, particularly in low AOD conditions; consequently, the uncertainties could not be quantified. Despite the issue in the aerosol type information, the present method allows us to confine the DREA attributed only to fine-mode dominant aerosols, which are expected to be mostly anthropogenic origin, in the range from -1.1 W/m2 to -1.3 W/m2 at TOA. Improvements in size-resolved AOD and SSA retrievals from current and upcoming satellite instruments are suggested to better assess the DREA, particularly at BOA and ATM, where aerosol absorptivity induces substantial uncertainty.

  20. Radiative forcing under mixed aerosol conditions

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

  3. Top-of-Atmosphere Direct Radiative Effect of Aerosols over Global Oceans from Merged CERES and MODIS Observations

    NASA Technical Reports Server (NTRS)

    Loeb, N. G.; Smith, N. M.

    2004-01-01

    The direct radiative effect of aerosols (DREA) is defined as the difference between radiative fluxes in the absence and presence of aerosols. In this study, the direct radiative effect of aerosols is estimated for 46 months (March, 2000 to December, 2003) of merged CERES and MODIS Terra global measurements over ocean. This analysis includes the contribution from clear regions in both clear and partly cloudy CERES footprints. MODIS-CERES narrow-to-broadband regressions are developed to convert clear-sky MODIS narrowband radiances to broadband SW radiances, and CERES clear-sky Angular Distribution Models (ADMs) are used to estimate the corresponding TOA radiative fluxes needed to determine the DREA. Clear-sky MODIS pixels are identified using two independent cloud masks: (i) the NOAA-NESDIS algorithm used for inferring aerosol properties from MODIS on the CERES Single Scanner Footprint TOA/Surface Fluxes and Clouds (SSF) product (NOAA-SSF); and (ii) the standard algorithm used by the MODIS aerosol group to produce the MODO4 product (MODO4). Over global oceans, direct radiative cooling by aerosols for clear scenes identified from MODO4 is estimated to be 5.5 W m-2, compared to 3.8 W m-2 for clear scenes from NOAA-SSF. Regionally, differences are largest in areas affected by dust aerosol, such as oceanic regions adjacent to the Saharan and Saudi Arabian deserts, and in northern Pacific Ocean regions influenced by dust transported from Asia. The net total-sky (clear and cloudy) DREA is negative (cooling) and is estimated to be -2.0 W m-2 from MOD04, and -1.6 W m-2 from NOAA-SSF. The DREA is shown to have pronounced seasonal cycles in the Northern Hemisphere and large year-to-year fluctuations near deserts. However, no systematic trend in deseasonalized anomalies of the DREA is observed over the 46-month time series considered.

  4. Transport and Mixing Patterns over Central California during the Carbonaceous Aerosol and Radiative Effects Study (CARES)

    SciTech Connect

    Fast, Jerome D.; Gustafson, William I.; Berg, Larry K.; Shaw, William J.; Pekour, Mikhail S.; Shrivastava, ManishKumar B.; Barnard, James C.; Ferrare, R.; Hostetler, Chris A.; Hair, John; Erickson, Matthew H.; Jobson, Tom; Flowers, Bradley; Dubey, Manvendra K.; Springston, Stephen R.; Pirce, Bradley R.; Dolislager, Leon; Pederson, J. R.; Zaveri, Rahul A.

    2012-02-17

    We describe the synoptic and regional-scale meteorological conditions that affected the transport and mixing of trace gases and aerosols in the vicinity of Sacramento, California during June 2010 when the Carbonaceous Aerosol and Radiative Effects Study (CARES) was conducted. The meteorological measurements collected by various instruments deployed during the campaign and the performance of the chemistry version of the Weather Research and Forecasting model (WRF-Chem) are both discussed. WRF-Chem was run daily during the campaign to forecast the spatial and temporal variation of carbon monoxide emitted from 20 anthropogenic source regions in California to guide aircraft sampling. The model is shown to reproduce the overall circulations and boundary-layer characteristics in the region, although errors in the upslope wind speed and boundary-layer depth contribute to differences in the observed and simulated carbon monoxide. Thermally-driven upslope flows that transported pollutants from Sacramento over the foothills of the Sierra Nevada occurred every afternoon, except during three periods when the passage of mid-tropospheric troughs disrupted the regional-scales flow patterns. The meteorological conditions after the passage of the third trough were the most favorable for photochemistry and likely formation of secondary organic aerosols. Meteorological measurements and model forecasts indicate that the Sacramento pollutant plume was likely transported over a downwind site that collected trace gas and aerosol measurements during 23 periods; however, direct transport occurred during only eight of these periods. The model also showed that emissions from the San Francisco Bay area transported by intrusions of marine air contributed a large fraction of the carbon monoxide in the vicinity of Sacramento, suggesting that this source likely affects local chemistry. Contributions from other sources of pollutants, such as those in the Sacramento Valley and San Joaquin Valley

  5. Transport and mixing patterns over Central California during the carbonaceous aerosol and radiative effects study (CARES)

    SciTech Connect

    Fast J. D.; Springston S.; Gustafson Jr., W. I.; Berg, L. K.; Shaw, W. J.; Pekour, M.; Shrivastava, M.; Barnard, J. C.; Ferrare, R. A.; Hostetler, C. A.; Hair, J. A.; Erickson, M.; Jobson, B. T.; Flowers, B.; Dubey, M. K.; Pierce, R. B.; Dolislager, L.; Pederson, J.; Zaveri, R. A.

    2012-02-17

    We describe the synoptic and regional-scale meteorological conditions that affected the transport and mixing of trace gases and aerosols in the vicinity of Sacramento, California during June 2010 when the Carbonaceous Aerosol and Radiative Effects Study (CARES) was conducted. The meteorological measurements collected by various instruments deployed during the campaign and the performance of the chemistry version of the Weather Research and Forecasting model (WRF-Chem) are both discussed. WRF-Chem was run daily during the campaign to forecast the spatial and temporal variation of carbon monoxide emitted from 20 anthropogenic source regions in California to guide aircraft sampling. The model is shown to reproduce the overall circulations and boundary-layer characteristics in the region, although errors in the upslope wind speed and boundary-layer depth contribute to differences in the observed and simulated carbon monoxide. Thermally-driven upslope flows that transported pollutants from Sacramento over the foothills of the Sierra Nevada occurred every afternoon, except during three periods when the passage of mid-tropospheric troughs disrupted the regional-scale flow patterns. The meteorological conditions after the passage of the third trough were the most favorable for photochemistry and likely formation of secondary organic aerosols. Meteorological measurements and model forecasts indicate that the Sacramento pollutant plume was likely transported over a downwind site that collected trace gas and aerosol measurements during 23 time periods; however, direct transport occurred during only eight of these periods. The model also showed that emissions from the San Francisco Bay area transported by intrusions of marine air contributed a large fraction of the carbon monoxide in the vicinity of Sacramento, suggesting that this source likely affects local chemistry. Contributions from other sources of pollutants, such as those in the Sacramento Valley and San Joaquin

  6. Diurnal variations of aerosol optical properties in the North China Plain and their influences on the estimates of direct aerosol radiative effect

    NASA Astrophysics Data System (ADS)

    Kuang, Y.; Zhao, C. S.; Tao, J. C.; Ma, N.

    2015-05-01

    In this paper, the diurnal variations of aerosol optical properties and their influences on the estimation of daily average direct aerosol radiative effect (DARE) in the North China Plain (NCP) are investigated based on in situ measurements from Haze in China campaign. For ambient aerosol, the diurnal patterns of single scattering albedo (SSA) and asymmetry factor (g) in the NCP are both highest at dawn and lowest in the late afternoon, and quite different from those of dry-state aerosol. The relative humidity (RH) is the dominant factor which determines the diurnal pattern of SSA and g for ambient aerosol. Basing on the calculated SSA and g, several cases are designed to investigate the impacts of the diurnal changes of aerosol optical properties on DARE. The results demonstrate that the diurnal changes of SSA and g in the NCP have significant influences on the estimation of DARE at the top of the atmosphere (TOA). If the full temporal coverage of aerosol optical depth (AOD), SSA and g are available, an accurate estimation of daily average DARE can be achieved by using the daily averages of AOD, SSA and g. However, due to the lack of full temporal coverage data sets of SSA and g, their daily averages are usually not available. Basing on the results of designed cases, if the RH plays a dominant role in the diurnal variations of SSA and g, we suggest that using both SSA and g averaged over early morning and late afternoon as inputs for radiative transfer model to improve the accurate estimation of DARE. If the temporal samplings of SSA or g are too few to adopt this method, either averaged over early morning or late afternoon of both SSA and g can be used to improve the estimation of DARE at the TOA.

  7. Diurnal variations of aerosol optical properties in the North China Plain and their influences on the estimates of direct aerosol radiative effect

    NASA Astrophysics Data System (ADS)

    Kuang, Ye; Zhao, Chunsheng

    2016-04-01

    In this paper, the diurnal variations of aerosol optical properties and their influences on the estimation of daily average direct aerosol radiative effect (DARE) in the North China Plain (NCP) are investigated based on in situ measurements from Haze in China campaign. For ambient aerosol, the diurnal patterns of single scattering albedo (SSA) and asymmetry factor (g) in the NCP are both highest at dawn and lowest in the late afternoon, and quite different from those of dry-state aerosol. The relative humidity is the dominant factor which determines the diurnal patterns of SSA and g for ambient aerosol. Basing on the calculated SSA and g, several cases are designed to investigate the impacts of the diurnal changes of aerosol optical properties on DARE. The results demonstrate that the diurnal changes of SSA and g in the NCP have significant influences on the estimation of DARE at the top of the atmosphere (TOA). If the full temporal coverage of aerosol optical depth (AOD), SSA and g are available, an accurate estimation of daily average DARE can be achieved by using the daily averages of AOD, SSA and g. However, due to the lack of full temporal coverage datasets of SSA and g, their daily averages are usually not available. Basing on the results of designed cases, if the RH plays a dominant role in the diurnal variations of SSA and g, we suggest that using both SSA and g averaged over early morning and late afternoon as inputs for radiative transfer model to improve the accurate estimation of DARE. If the temporal samplings of SSA or g are too few to adopt this method, either averaged over early morning or late afternoon of both SSA and g can be used to improve the estimation of DARF at TOA.

  8. Parameterization of clear-sky surface irradiance and its implications for estimation of aerosol direct radiative effect and aerosol optical depth

    PubMed Central

    Xia, Xiangao

    2015-01-01

    Aerosols impact clear-sky surface irradiance () through the effects of scattering and absorption. Linear or nonlinear relationships between aerosol optical depth (τa) and have been established to describe the aerosol direct radiative effect on (ADRE). However, considerable uncertainties remain associated with ADRE due to the incorrect estimation of (τa in the absence of aerosols). Based on data from the Aerosol Robotic Network, the effects of τa, water vapor content (w) and the cosine of the solar zenith angle (μ) on are thoroughly considered, leading to an effective parameterization of as a nonlinear function of these three quantities. The parameterization is proven able to estimate with a mean bias error of 0.32 W m−2, which is one order of magnitude smaller than that derived using earlier linear or nonlinear functions. Applications of this new parameterization to estimate τa from , or vice versa, show that the root-mean-square errors were 0.08 and 10.0 Wm−2, respectively. Therefore, this study establishes a straightforward method to derive from τa or estimate τa from measurements if water vapor measurements are available. PMID:26395310

  9. Parameterization of clear-sky surface irradiance and its implications for estimation of aerosol direct radiative effect and aerosol optical depth

    NASA Astrophysics Data System (ADS)

    Xia, Xiangao

    2015-09-01

    Aerosols impact clear-sky surface irradiance () through the effects of scattering and absorption. Linear or nonlinear relationships between aerosol optical depth (τa) and have been established to describe the aerosol direct radiative effect on (ADRE). However, considerable uncertainties remain associated with ADRE due to the incorrect estimation of (τa in the absence of aerosols). Based on data from the Aerosol Robotic Network, the effects of τa, water vapor content (w) and the cosine of the solar zenith angle (μ) on are thoroughly considered, leading to an effective parameterization of as a nonlinear function of these three quantities. The parameterization is proven able to estimate with a mean bias error of 0.32 W m-2, which is one order of magnitude smaller than that derived using earlier linear or nonlinear functions. Applications of this new parameterization to estimate τa from , or vice versa, show that the root-mean-square errors were 0.08 and 10.0 Wm-2, respectively. Therefore, this study establishes a straightforward method to derive from τa or estimate τa from measurements if water vapor measurements are available.

  10. The Effect of Recent Aerosol Trends on Solar Radiation in the Central and Southeastern United States: Implications for Regional Hydrology.

    NASA Astrophysics Data System (ADS)

    Cusworth, D.; Mickley, L. J.; Leibensperger, E. M.; Iacono, M. J.

    2015-12-01

    Observations show large increases in summertime (JJA) surface solar radiation (SWdn) over the central and southeastern United States during the last 20 years, as much as a +40 Wm-2 at midday. At the same time, in response to environmental regulations in the early 1990s, emissions of U.S. aerosol precursors have decreased by as much as 60%. Detecting a possible connection between these two trends has been difficult due to the secondary effects of aerosols on cloud concentration and lifetime, and previous efforts have failed to find a direct link. Here we investigate the clear-sky direct effect of decreasing U.S. aerosols on climate, using a radiative transfer model (RRTMG) driven by 1997-2014 measurements of aerosol optical depth at Surface Radiation Budget Network (SURFRAD) sites in the central and southeastern United States. We impose aerosol asymmetry parameters and single scattering albedos from nearby Aerosol Robotic Network (AERONET) sites. Preliminary results indicate that declining aerosols drive a summer noontime change in clear-sky SWdn of +25 Wm-2 since 1997 at Goodwin Creek, MS, accounting for 56% of the observed increase in SWdn at that site. Similarly, we find that aerosols increase clear-sky SWdn by +6.5 Wm-2 in Bondville, IL, which accounts for 21% of the observed SWdn trend there. These results suggest that the climate in these regions of the U.S. may be sensitive to recent reductions in aerosol concentrations, especially during summer months. We also analyze in situ soil measurements from the Illinois Climate Network from 1990-present, and find that a significant decrease in soil moisture (-0.6 m3 m-3 a-1) accompanies the increase in SWdn, implying a link between aerosol trends and regional hydrology. Aerosol reductions are expected to continue in the United States and may further influence regional climate including hydrological factors. Our work has implications for polluted regions outside the U.S., where future reductions in the aerosol burden

  11. A Novel Method for Estimating Shortwave Direct Radiative Effect of Above-Cloud Aerosols Using CALIOP and MODIS Data

    NASA Technical Reports Server (NTRS)

    Zhang, Z.; Meyer, K.; Platnick, S.; Oreopoulos, L.; Lee, D.; Yu, H.

    2014-01-01

    This paper describes an efficient and unique method for computing the shortwave direct radiative effect (DRE) of aerosol residing above low-level liquid-phase clouds using CALIOP and MODIS data. It accounts for the overlapping of aerosol and cloud rigorously by utilizing the joint histogram of cloud optical depth and cloud top pressure. Effects of sub-grid scale cloud and aerosol variations on DRE are accounted for. It is computationally efficient through using grid-level cloud and aerosol statistics, instead of pixel-level products, and a pre-computed look-up table in radiative transfer calculations. We verified that for smoke over the southeast Atlantic Ocean the method yields a seasonal mean instantaneous shortwave DRE that generally agrees with more rigorous pixel-level computation within 4. We have also computed the annual mean instantaneous shortwave DRE of light-absorbing aerosols (i.e., smoke and polluted dust) over global ocean based on 4 yr of CALIOP and MODIS data. We found that the variability of the annual mean shortwave DRE of above-cloud light-absorbing aerosol is mainly driven by the optical depth of the underlying clouds.

  12. Air pollution and climate response to aerosol direct radiative effects: A modeling study of decadal trends across the northern hemisphere

    NASA Astrophysics Data System (ADS)

    Xing, Jia; Mathur, Rohit; Pleim, Jonathan; Hogrefe, Christian; Gan, Chuen-Meei; Wong, David C.; Wei, Chao; Wang, Jiandong

    2015-12-01

    Decadal hemispheric Weather Research and Forecast-Community Multiscale Air Quality simulations from 1990 to 2010 were conducted to examine the meteorology and air quality responses to the aerosol direct radiative effects. The model's performance for the simulation of hourly surface temperature, relative humidity, wind speed, and direction was evaluated through comparison with observations from NOAA's National Climatic Data Center Integrated Surface Data. The inclusion of aerosol direct radiative effects improves the model's ability to reproduce the trend in daytime temperature range which over the past two decades was increasing in eastern China but decreasing in eastern U.S. and Europe. Trends and spatial and diurnal variations of the surface-level gaseous and particle concentrations to the aerosol direct effect were analyzed. The inclusion of aerosol direct radiative effects was found to increase the surface-level concentrations of SO2, NO2, O3, SO42-, NO3-, and particulate matter 2.5 in eastern China, eastern U.S., and Europe by 1.5-2.1%, 1-1.5%, 0.1-0.3%, 1.6-2.3%, 3.5-10.0%, and 2.2-3.2%, respectively, on average over the entire 21 year period. However, greater impacts are noted during polluted days with increases of 7.6-10.6%, 6.2-6.7%, 2.0-3.0%, 7.8-9.5%, 11.1-18.6%, and 7.2-10.1%, respectively. Due to the aerosol direct radiative effects, stabilizing of the atmosphere associated with reduced planetary boundary layer height and ventilation leads to an enhancement of pollution. Consequently, the continual increase of aerosol optical depth (AOD) in eastern China leads to an increasing trend in the air quality feedback which exacerbates air pollution, while emission reductions in eastern U.S. and Europe result in a declining trend in both AODs and feedback which make the air pollution control strategies more effective.

  13. Direct and semi-direct aerosol radiative effect on the Mediterranean climate variability using a coupled regional climate system model

    NASA Astrophysics Data System (ADS)

    Nabat, Pierre; Somot, Samuel; Mallet, Marc; Sevault, Florence; Chiacchio, Marc; Wild, Martin

    2015-02-01

    A fully coupled regional climate system model (CNRM-RCSM4) has been used over the Mediterranean region to investigate the direct and semi-direct effects of aerosols, but also their role in the radiation-atmosphere-ocean interactions through multi-annual ensemble simulations (2003-2009) with and without aerosols and ocean-atmosphere coupling. Aerosols have been taken into account in CNRM-RCSM4 through realistic interannual monthly AOD climatologies. An evaluation of the model has been achieved, against various observations for meteorological parameters, and has shown the ability of CNRM-RCSM4 to reproduce the main patterns of the Mediterranean climate despite some biases in sea surface temperature (SST), radiation and cloud cover. The results concerning the aerosol radiative effects show a negative surface forcing on average because of the absorption and scattering of the incident radiation. The SW surface direct effect is on average -20.9 Wm-2 over the Mediterranean Sea, -14.7 Wm-2 over Europe and -19.7 Wm-2 over northern Africa. The LW surface direct effect is weaker as only dust aerosols contribute (+4.8 Wm-2 over northern Africa). This direct effect is partly counterbalanced by a positive semi-direct radiative effect over the Mediterranean Sea (+5.7 Wm-2 on average) and Europe (+5.0 Wm-2) due to changes in cloud cover and atmospheric circulation. The total aerosol effect is consequently negative at the surface and responsible for a decrease in land (on average -0.4 °C over Europe, and -0.5 °C over northern Africa) and sea surface temperature (on average -0.5 °C for the Mediterranean SST). In addition, the latent heat loss is shown to be weaker (-11.0 Wm-2) in the presence of aerosols, resulting in a decrease in specific humidity in the lower troposphere, and a reduction in cloud cover and precipitation. Simulations also indicate that dust aerosols warm the troposphere by absorbing solar radiation, and prevent radiation from reaching the surface, thus

  14. Air pollution and climate response to aerosol direct radiative effects: A modeling study of decadal trends across the northern hemisphere

    EPA Science Inventory

    Decadal hemispheric Weather Research and Forecast-Community Multiscale Air Quality simulations from 1990 to 2010 were conducted to examine the meteorology and air quality responses to the aerosol direct radiative effects. The model's performance for the simulation of hourly surfa...

  15. Statistical variability of top of atmosphere cloud-free shortwave aerosol radiative effect

    NASA Astrophysics Data System (ADS)

    Jones, T. A.; Christopher, S. A.

    2007-06-01

    The statistical variability of globally averaged MODIS aerosol optical thickness at 0.55 μm (AOT) and top of atmosphere CERES cloud-free shortwave radiative effect (SWRE) is presented. Statistical variability is defined as the robustness of globally averaged statistics relative to data distribution. At the CERES footprint level, which we label "raw data", both the AOT and SWRE data derived from clear-sky CERES-SSF products show significant deviations from a normal distribution as evidenced by high skewness values. The spatial and temporal distribution of the data is also not uniform, with a greater concentration of data occurring in aerosol heavy-regions. As a result, globally averaged AOT and SWRE are overestimated when derived from raw data alone. To compensate, raw data are gridded into 2×2 degree grid-cells (called "gridded" data) to reduce the effect of spatial non-uniformity. However, the underlying non-normal distribution remains and manifests itself by increasing the uncertainty of grid-cell values. Globally averaged AOT and SWRE derived from a gridded dataset are substantially lower than those derived from raw data alone. The range of globally averaged AOT and SWRE values suggests that up to a 50% statistical variability exists, much of which is directly tied to how the data are manipulated prior to averaging. This variability increases when analyzing aerosol components (e.g. anthropogenic) since component AOT (and SWRE) may not exist at all locations were AOT is present. As a result, regions where a particular component AOT does not exist must either not be included in the global average or have data within these regions set to null values. However, each method produces significantly different results. The results of this work indicate simple mean and standard deviation statistics do not adequately describe global aerosol climate forcing data sets like the one used here. We demonstrate that placing raw observations on to a uniform grid is a necessary

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

    PubMed

    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 (RH<40%) and ambient conditions, respectively. The average single-scattering albedo (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

  17. Aerosol direct radiative effect of smoke over clouds over the southeast Atlantic Ocean from 2006 to 2009

    NASA Astrophysics Data System (ADS)

    Graaf, M.; Bellouin, N.; Tilstra, L. G.; Haywood, J.; Stammes, P.

    2014-11-01

    The aerosol direct radiative effect (DRE) of African smoke was analyzed in cloud scenes over the southeast Atlantic Ocean, using Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) satellite observations and Hadley Centre Global Environmental Model version 2 (HadGEM2) climate model simulations. The observed mean DRE was about 30-35 W m-2 in August and September 2006-2009. In some years, short episodes of high-aerosol DRE can be observed, due to high-aerosol loadings, while in other years the loadings are lower but more prolonged. Climate models that use evenly distributed monthly averaged emission fields will not reproduce these high-aerosol loadings. Furthermore, the simulated monthly mean aerosol DRE in HadGEM2 is only about 6 W m-2 in August. The difference with SCIAMACHY mean observations can be partly explained by an underestimation of the aerosol absorption Ångström exponent in the ultraviolet. However, the subsequent increase of aerosol DRE simulation by about 20% is not enough to explain the observed discrepancy between simulations and observations.

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

    EPA Science Inventory

    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 Importance of Aerosol-Cloud Interaction

    NASA Technical Reports Server (NTRS)

    Tsay, Si-Chee

    1999-01-01

    Aerosol particles are input into the troposphere by biomass burning, among other sources. These aerosol palls cover large expanses of the earth's surface. Aerosols may directly scatter solar radiation back to space, thus increasing the earth's albedo and act to cool the earth's surface and atmosphere. Aerosols also contribute to the earth's energy balance indirectly. Hygroscopic aerosol act as cloud condensation nuclei (CCN) and thus affects cloud properties. In 1977, Twomey theorized that additional available CCN would create smaller but more numerous cloud droplets in a cloud with a given amount of liquid water. This in turn would increase the cloud albedo which would scatter additional radiation back to space and create a similar cooling pattern as the direct aerosol effect. Estimates of the magnitude of the aerosol indirect effect on a global scale range from 0.0 to -4.8 W/sq m. Thus the indirect effect can be of comparable magnitude and opposite in sign to the estimates of global greenhouse gas forcing Aerosol-cloud interaction is not a one-way process. Just as aerosols have an influence on clouds through the cloud microphysics, clouds have an influence on aerosols. Cloud droplets are solutions of liquid water and CCN, now dissolved. When the cloud droplet evaporates it leaves behind an aerosol particle. This new particle does not have to have the same properties as the original CCN. In fact, studies show that aerosol particles that result from cloud processing are larger in size than the original CCN. Optical properties of aerosol particles are dependent on the size of the particles. Larger particles have a smaller backscattering fraction, and thus less incoming solar radiation will be backscattered to space if the aerosol particles are larger. Therefore, we see that aerosols and clouds modify each other to influence the radiative balance of the earth. Understanding and quantifying the spatial and seasonal patterns of the aerosol indirect forcing may have

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  1. Light Absorption Properties and Radiative Effects of Primary Organic Aerosol Emissions

    EPA Science Inventory

    Organic aerosols (OA) in the atmosphere affect Earth’s energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called “brown carbon” (BrC) component. However, the absorptivities of OA are not or poorly represented in current climate m...

  2. Seasonal variations of aerosol optical properties, vertical distribution and associated radiative effects in the Yangtze Delta region of China

    NASA Astrophysics Data System (ADS)

    Liu, Jianjun; Zheng, Youfei; Li, Zhanqing; Flynn, Connor; Cribb, Maureen

    2012-08-01

    Four years of columnar aerosol optical properties and a one-year vertical profiles of aerosol particle extinction coefficient at 527 nm are analyzed at Taihu in the central Yangtze River Delta region in eastern China. Seasonal variations of aerosol optical properties, vertical distribution, and influence on shortwave radiation and heating rates were investigated. Multiyear variations of aerosol optical depths (AOD), Ångstrom exponents, single scattering albedo (SSA) and asymmetry factor (ASY) are analyzed, together with the vertical profile of aerosol extinction. AOD is largest in summer and smallest in winter. SSAs exhibit weak seasonal variation with the smallest values occurring during winter and the largest during summer. The vast majority of aerosol particles are below 2 km, and about 62%, 67%, 67% and 83% are confined to below 1 km in spring, summer, autumn and winter, respectively. Five-day back trajectory analyses show that the some aerosols aloft are traced back to northern/northwestern China, as far as Mongolia and Siberia, in spring, autumn and winter. The presence of dust aerosols were identified based on the linear depolarization measurements together with other information (i.e., back trajectory, precipitation, aerosol index). Dust strongly impacts the vertical particle distribution in spring and autumn, with much smaller effects in winter. The annual mean aerosol direct shortwave radiative forcing (efficiency) at the bottom, top and within the atmosphere are -34.8 ± 9.1 (-54.4 ± 5.3), -8.2 ± 4.8 (-13.1 ± 1.5) and 26.7 ± 9.4 (41.3 ± 4.6) W/m2 (Wm-2 τ-1), respectively. The mean reduction in direct and diffuse radiation reaching surface amount to 109.2 ± 49.4 and 66.8 ± 33.3 W/m2, respectively. Aerosols significantly alter the vertical profile of solar heating, with great implications for atmospheric stability and dynamics within the lower troposphere.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Strategy to use the Terra Aerosol Information to Derive the Global Aerosol Radiative Forcing of Climate

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    Terra will derive the aerosol optical thickness and properties. The aerosol properties can be used to distinguish between natural and human-made aerosol. In the polar orbit Terra will measure aerosol only once a day, around 10:30 am. How will we use this information to study the global radiative impacts of aerosol on climate? We shall present a strategy to address this problem. It includes the following steps: - From the Terra aerosol optical thickness and size distribution model we derive the effect of aerosol on reflection of solar radiation at the top of the atmosphere. In a sensitivity study we show that the effect of aerosol on solar fluxes can be derived 10 times more accurately from the MODIS data than derivation of the optical thickness itself. Applications to data over several regions will be given. - Using 1/2 million AERONET global data of aerosol spectral optical thickness we show that the aerosol optical thickness and properties during the Terra 10:30 pass are equivalent to the daily average. Due to the aerosol lifetime of several days measurements at this time of the day are enough to assess the daily impact of aerosol on radiation. - Aerosol impact on the top of the atmosphere is only part of the climate question. The INDOEX experiment showed that addressing the impact of aerosol on climate, requires also measurements of the aerosol forcing at the surface. This can be done by a combination of measurements of MODIS and AERONET data.

  5. Longwave radiative forcing by aqueous aerosols

    SciTech Connect

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

    1995-01-01

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

  6. Improvement in Clouds and the Earth's Radiant Energy System/Surface and Atmosphere Radiation Budget Dust Aerosol Properties, Effects on Surface Validation of Clouds and Radiative Swath

    SciTech Connect

    Rutan, D.; Rose, F.; Charlock, T.P.

    2005-03-18

    Within the Clouds and the Earth's Radiant Energy System (CERES) science team (Wielicki et al. 1996), the Surface and Atmospheric Radiation Budget (SARB) group is tasked with calculating vertical profiles of heating rates, globally, and continuously, beneath CERES footprint observations of Top of Atmosphere (TOA) fluxes. This is accomplished using a fast radiative transfer code originally developed by Qiang Fu and Kuo-Nan Liou (Fu and Liou 1993) and subsequently highly modified by the SARB team. Details on the code and its inputs can be found in Kato et al. (2005) and Rose and Charlock (2002). Among the many required inputs is characterization of the vertical column profile of aerosols beneath each footprint. To do this SARB combines aerosol optical depth information from the moderate-resolution imaging spectroradiometer (MODIS) instrument along with aerosol constituents specified by the Model for Atmosphere and Chemical Transport (MATCH) of Collins et al. (2001), and aerosol properties (e.g. single scatter albedo and asymmetry parameter) from Tegen and Lacis (1996) and OPAC (Hess et al. 1998). The publicly available files that include these flux profiles, called the Clouds and Radiative Swath (CRS) data product, available from the Langley Atmospheric Sciences Data Center (http://eosweb.larc.nasa.gov/). As various versions of the code are completed, publishable results are named ''Editions.'' After CRS Edition 2A was finalized it was found that dust aerosols were too absorptive. Dust aerosols have subsequently been modified using a new set of properties developed by Andy Lacis and results have been released in CRS Edition 2B. This paper discusses the effects of changing desert dust aerosol properties, which can be significant for the radiation budget in mid ocean, a few thousand kilometers from the source regions. Resulting changes are validated via comparison of surface observed fluxes from the Saudi Solar Village surface site (Myers et al. 1999), and the E13 site

  7. Radiative impact of aerosols generated from biomass burning

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    Atmospheric aerosol particles play a vital role in the Earth's radiative energy budget. They exert a net cooling influence on climate by directly reflecting the solar radiation to space and by modifying the shortwave reflective properties of clouds. Each year, increasing amounts of aerosol particles are released into the atmosphere due to biomass burning, dust storms, forest fires, and volcanic activity. These particles significantly perturb the radiative balance on local, regional, and global scales. While the detection of aerosols over water is a well established procedure, the detection of aerosols over land is often difficult due to the poor contrast between the aerosols and the underlying terrain. In this study, we use textural measures in order to detect aerosols generated from biomass burning over South America, using AVHRR data. The regional radiative effects are then examined using ERBE data. Preliminary results show that the net radiative forcing of aerosols is about -36 W/sq m.

  8. Statistical uncertainty of top of atmosphere cloud-free shortwave Aerosol Radiative Effect

    NASA Astrophysics Data System (ADS)

    Jones, T. A.; Christopher, S. A.

    2007-03-01

    The statistical uncertainty of globally averaged MODIS aerosol optical thickness at 0.55 μm (AOT) and top of atmosphere CERES cloud-free shortwave radiative effect (SWRE) is presented. All analysis is presented at the CERES footprint level which we call "raw data". Statistical uncertainty may result from the raw data not being normally distributed. Both the AOT and SWRE data derived from clear-sky CERES-SSF products show significant deviations from a normal distribution as evidenced by high skewness values. The spatial and temporal distribution of the data is also not uniform, with a greater concentration of data being in aerosol heavy regions. As a result, globally averaged AOT and SWRE are overestimated when derived from raw data. Raw data are gridded into 2×2 degree grid-cells (called "gridded" data) to reduce the effect of spatial non-uniformity. However, the underlying non-normal distribution remains and manifests itself by increasing the uncertainty of grid-cell values. Globally averaged AOT and SWRE derived from a gridded dataset are substantially lower than those derived from raw data alone. The range of globally averaged AOT and SWRE values suggests that up to a 50% statistical uncertainty exists, much of which is directly tied to how the data are manipulated prior to averaging. This uncertainty increases when analyzing aerosol components (e.g. anthropogenic) since component AOT (and SWRE) may not exist at all locations were AOT is present. As a result, regions where a particular component AOT does not exist must either not be included in the global average or have data within these regions set to null values. However, each method produces significantly different results. The results of this work indicate that placing raw observations on to a uniform grid is a necessary step before calculating global statistics. However, this by no means eliminates statistical uncertainty, while adding its own set of assumptions. When reporting any globally averaged

  9. Study on impact of aerosols on solar radiation and its climate effect in Southwest China

    NASA Astrophysics Data System (ADS)

    Zheng, Xiaobo; Zhao, Tianliang; Zhang, Xiaojuan

    Air temperature in Southwest China has changed out of phase with the Northern Hemispheric temperature change since last century, which could be connected to increasing aerosols in that region. By using the 50-year (1961-2010) data of meteorology observed at 19 ground sites in Southwest China and 10-year MODIS-AOD data, the change in global solar radiation and its correlations to the influencing elements of horizontal visibility, cloud amount, wind and AOD are analysed. The analysis results show 1) over the area with high AOD(AOD>0.3),solar radiation had decreased significantly over the 1960s-1990s, but in this century, the decreased trend in solar radiation has ceased and even slightly levelled up at some sites, but the solar radiation has not recovered to the level in the 1960s. The decreased solar radiation is corresponded with less visibility, more aerosols and weakening wind as well as is also related with change in cloud amounts. 2) over the low AOD area(AOD≦0.3)in Southwest China, solar radiation has varied in the insignificant trends excepting the significant increase in solar radiation at Emei Mountain with altitude of 3047m after the 1990s. 3) Meteorological elements are responded to climate change in solar radiation. The sunshine duration is positively correlated with solar radiation at all sites with passing significance test of 99% level at the most sites in Southwest China. Decreases in solar radiation lead to cooling in temperature and decline in evaporation at high AOD regions. The maximum temperature and solar radiation vary in relatively good phase but with a complex response of evaporation to solar radiation over low AOD sites in Southwest China.

  10. Atmospheric numerical simulation of the aerosol microphysics and radiative effects in a regional biomass burning smoke plume in South America

    NASA Astrophysics Data System (ADS)

    Longo, K.; Freitas, S.; Silva Dias, M.; Silva Dias, P.; Chatfield, R.

    2003-04-01

    A study about the atmospheric transport of biomass burning emissions in the Amazon and the central of Brazil including its radiative effects is presented. The sources are spatially and temporally distributed and daily assimilated, according to the biomass burning spots defined by GOES-8 ABBA fire products. A fire smoke particles source parameterization, including aerosol particle concentration and optical properties, was used to build the initial smoke plumes associated with biomass burning in tropical forest and savanna. This study is carried out through a numerical simulation of the atmospheric motions using the atmospheric model RAMS "Regional Atmospheric Modeling System" and the coupled microphysics aerosol model CARMA "Community Aerosol &Radiation Model for Atmospheres". In this method the mass conservation equation and aerosol particle process, like nucleation, coagulation, condensation and dry deposition, are resolved for the biomass burning aerosol particles. The advection, in a resolved scale, and turbulent transport, in a sub-grid scale, are resolved using RAMS model parameterizations. A transport sub-grid parameterization, associated to deep and shallow cumulus convection, not explicitly resolved by the model due its low spatial resolution, is introduced. Also, a wet deposition term, coupled to the cumulus parameterization, is taken into account. The methodology is applied to a case study on August 2002 and the responses of the model to the presence of the aerosol particles in the atmosphere are explored. Also the comparison of the simulated smoke haze layer with MODIS products pointed out the usefulness of the sources emissions parameterization and the suitability of the aerosol process description presented here.

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

    SciTech Connect

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

    2002-09-01

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

  12. Impacts of the direct radiative effect of aerosols in numerical weather prediction over Europe using the ALADIN-HIRLAM NWP system

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    Aerosol feedbacks are becoming more accepted as physical mechanisms that should be included in numerical weather prediction models in order to improve the accuracy of the weather forecasts. The default set-up in the Aire Limitee Adaptation dynamique Developpement INternational (ALADIN) - High Resolution Limited Area Model (HIRLAM) numerical weather prediction system includes monthly aerosol climatologies to account for the average direct radiative effect of aerosols. This effect was studied using the default aerosol climatology in the system and compared to experiments run using the more up-to-date Max-Planck-Institute Aerosol Climatology version 1 (MACv1), and time-varying aerosol data from the Monitoring Atmospheric Composition and Climate (MACC) reanalysis aerosol dataset. Accounting for the direct radiative effect using monthly aerosol climatologies or near real-time aerosol distributions improved the accuracy of the simulated radiative fluxes and temperature and humidity forecasts in the lower troposphere. However, the dependency of forecast meteorological conditions on the aerosol dataset itself was found to be weak.

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Technical Reports Server (NTRS)

    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

  15. A Novel Method for Estimating Shortwave Direct Radiative Effect of Above-Cloud Aerosols Using CALIOP and MODIS Data

    NASA Technical Reports Server (NTRS)

    Zhang, Zhibo; Meyer, Kerry G.; Platnick, Steven; Oreopoulos, Lazaros; Lee, Dongmin; Yu, Hongbin

    2014-01-01

    This paper describes an efficient and unique method for computing the shortwave direct radiative effect (DRE) of aerosol residing above low-level liquid-phase clouds using CALIOP and MODIS data. It addresses the overlap of aerosol and cloud rigorously by utilizing the joint histogram of cloud optical depth and cloud top pressure while also accounting for subgrid-scale variations of aerosols. The method is computationally efficient because of its use of grid-level cloud and aerosol statistics, instead of pixel-level products, and a pre-computed look-up table based on radiative transfer calculations. We verify that for smoke over the southeast Atlantic Ocean the method yields a seasonal mean instantaneous (approximately 1:30PM local time) shortwave DRE of above cloud aerosol (ACA) that generally agrees with more rigorous pixel-level computation within 4 percent. We also estimate the impact of potential CALIOP aerosol optical depth (AOD) retrieval bias of ACA on DRE. We find that the regional and seasonal mean instantaneous DRE of ACA over southeast Atlantic Ocean would increase, from the original value of 6.4 W m(-2) based on operational CALIOP AOD to 9.6 W m(-2) if CALIOP AOD retrieval are biased low by a factor of 1.5 (Meyer et al., 2013) and further to 30.9 W m(-2) if CALIOP AOD retrieval are biased low by a factor of 5 as suggested in (Jethva et al., 2014). In contrast, the instantaneous ACA radiative forcing efficiency (RFE) remains relatively invariant in all cases at about 53 W m(-2) AOD(-1), suggesting a near linear relation between the instantaneous RFE and AOD. We also compute the annual mean instantaneous shortwave DRE of light-absorbing aerosols (i.e., smoke and polluted dust) over global oceans based on 4 years of CALIOP and MODIS data. We find that the variability of the annual mean shortwave DRE of above-cloud light-absorbing aerosol is mainly driven by the optical depth of the underlying clouds. While we demonstrate our method using CALIOP and MODIS

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

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

    NASA Astrophysics Data System (ADS)

    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

  18. Effects of sulfate aerosol on the central Pennsylvania surface shortwave radiation budget. Master's thesis

    SciTech Connect

    Guimond, P.W.

    1994-12-01

    Surface radiation measurements are taken simultaneously with measurements of meteorological variables including temperature, pressure, relative humidity, and visibility to evaluate the impact of sulfate haze on the surface radiation budget. A relationship is sought between flux losses due only to aerosol and relative humidity, visibility or both, with the goal of facilitating parameterization of sulfate hazes by climate modelers. At the same time, a rotating shadowband radiometer (RSR) is compared with a more costly sun photometer to determine the feasibility of substituting the former for the latter in future research. It is found that depletion of surface radiation due to aerosol is typically ten to twenty percent of initial insolation, and that the losses can be correlated with zenith angle, relative humidity and optical depth. In the case of flux loss as a function of optical depth, the two are related in a nearly linear fashion. It is also discovered that the RSR has a predictable error owing to a wider field of view than the sun photometer, and can be used as a replacement for the former by correcting for the error.

  19. Point and column aerosol radiative closure during ACE 1: Effects of particle shape and size

    NASA Astrophysics Data System (ADS)

    Fridlind, A. M.; Jacobson, M. Z.

    2003-02-01

    We used data collected during the First Aerosol Characterization Experiment (ACE 1) to study point and column aerosol radiative closure over the remote ocean. To test point closure, total and hemispheric backscattering coefficients calculated with a Mie single-scattering model were compared with measurements made by ship and aircraft at three wavelengths (400, 550, and 700 nm). On the ship, assuming spherical particles, calculated total scattering was usually within 10% of measurements (closure obtained in >80% of the cases) but calculated backscattering was usually 15-25% lower than measurements (closure obtained in <50% of the cases). When a model for particle nonsphericity was applied to the dried sea spray, assuming the particles to be ideal cubes or irregular convex and concave crystals resulted in overestimation of backscattering. However, when nonsphericity parameters were fit to the measurements, calculated backscattering was also usually within 10% of measurements (closure obtained in >80% of the cases). On the aircraft, however, calculated scattering and backscattering were usually lower than measurements by 20-45% regardless of assumed particle shape (closure obtained in <50% of the cases), likely owing to differences in the aerosol inlet penetration efficiencies to each instrument or unidentified uncertainties in the measured number size distributions or scattering coefficients. To test column closure, aerosol extinction profiles calculated from in situ observations (below 5.5 km) and satellite observations (above 5.5 km) were vertically integrated, and the resulting aerosol optical depth was compared with measurements made on the ship during two clear-sky days at three wavelengths (500, 778, and 862 nm). Calculated spectral optical depths were usually within 25% of measurements (closure obtained at one or more wavelengths on both days), and agreement at longer wavelengths was improved when satellite measurements were spectrally scaled using in situ

  20. Characterization of Speciated Aerosol Direct Radiative Forcing Over California

    SciTech Connect

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

    2013-03-16

    . Aerosol radiative forcing is presented along with the contribution from individual aerosol species from the simulation with anthropogenic EC emission doubled. On statewide average over California, aerosol reduces the seasonal-average surface radiation fluxes by about 3 W m-2 with a maximum of 10 W m-2 in summer. In the atmosphere, aerosol introduces a warming effect of about 2 W m-2 with a maximum of 10 W m-2 also in summer. EC and dust contribute about 75-95% and 1-10% of the total warming through the seasons, respectively. At the top of atmosphere (TOA), the overall aerosol radiative effect is cooling with a maximum of -3.5 W m-2. EC contributes exclusively to the TOA warming of up to about 0.7 W m-2. The encouraging performance of WRF-Chem in simulating aerosols and their radiative forcing suggests that the model is suitable for further investigation of the impact of emission control on radiative forcing and regional climate over California.

  1. On the Effect of Heavy Aerosols Loads on Longwave Atmospheric Radiation, Theoretical Investigations

    NASA Astrophysics Data System (ADS)

    Maghrabi, Abdullrahman

    2014-05-01

    Dust particles affect both solar and terrestrial radiation by scattering and absorption and are therefore considered to be a significant climate-forcing factor. In this study, theoretical simulations were carried out using MODTRAN program to examine the changes in the atmospheric radiation (4- 100 μm) during dust storms occurred over Riyadah, central Saudi Arabia, between 1999-2000 . The Atmospheric Optical Depth (AOD) measurements at (500 nm) and meteorological parameters were used as an input into MODTRAN. The simulation results showed that the heavy aerosol loads brought by the dust storms increase the atmospheric emission in the atmospheric window (8-14 μm) such that the window emissions resembled those of a blackbody and the atmospheric window was almost closed.

  2. Light absorption properties and radiative effects of primary organic aerosol emissions.

    PubMed

    Lu, Zifeng; Streets, David G; Winijkul, Ekbordin; Yan, Fang; Chen, Yanju; Bond, Tami C; Feng, Yan; Dubey, Manvendra K; Liu, Shang; Pinto, Joseph P; Carmichael, Gregory R

    2015-04-21

    Organic aerosols (OAs) in the atmosphere affect Earth's energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called "brown carbon" (BrC) component. However, the absorptivities of OAs are not represented or are poorly represented in current climate and chemical transport models. In this study, we provide a method to constrain the BrC absorptivity at the emission inventory level using recent laboratory and field observations. We review available measurements of the light-absorbing primary OA (POA), and quantify the wavelength-dependent imaginary refractive indices (kOA, the fundamental optical parameter determining the particle's absorptivity) and their uncertainties for the bulk POA emitted from biomass/biofuel, lignite, propane, and oil combustion sources. In particular, we parametrize the kOA of biomass/biofuel combustion sources as a function of the black carbon (BC)-to-OA ratio, indicating that the absorptive properties of POA depend strongly on burning conditions. The derived fuel-type-based kOA profiles are incorporated into a global carbonaceous aerosol emission inventory, and the integrated kOA values of sectoral and total POA emissions are presented. Results of a simple radiative transfer model show that the POA absorptivity warms the atmosphere significantly and leads to ∼27% reduction in the amount of the net global average POA cooling compared to results from the nonabsorbing assumption. PMID:25811601

  3. The direct effect of aerosols on the radiation budget and climate of the Earth-atmosphere system: its variability in space and time

    NASA Astrophysics Data System (ADS)

    Hatzianastassiou, N.

    2009-04-01

    Atmospheric aerosols, these tiny particles suspended in the air, play a very important role for the Earth-atmosphere climate system on both global and regional scales through various mechanisms and physical processes. The climatic effects of aerosols are determined by modifications they induce on the various components of the Earth's radiation budget. Despite the progress that has been made lately, there is still much to learn about the climatic role of aerosols in various aspects. One of the most important issues that has to be addressed is the spatial and temporal variability, especially the temporal variability of aerosol properties and their consequent radiative effects. For example, there is uncertainty with regard to aerosol radiative properties and whether or not aerosol loads are increasing or decreasing with time, and what the consequences are. Moreover, the extent to which aerosols cool or warm the planet is not clear, as well as the contribution to this cooling/warming by aerosols of natural and anthropogenic origin. Given that the aerosol radiative effects, especially on radiation reaching the Earth's surface and in the atmosphere, cannot be directly measured/observed, models are necessary to overcome this problem. Specifically, radiative transfer models (RTMs) are able to calculate the radiation fluxes within the entire Earth-atmosphere system from regional to planetary scale, and the flux changes caused by aerosols. Yet, what is more interesting for models is that they allow us to study in detail the space and time resolved aerosol radiative effects and their sensitivity to various physical parameters. Using RTMs the aerosol direct effect on solar radiation can be determined at the top of the atmosphere (DRETOA) in the atmosphere (DREatm) and at the Earth's surface (DREsurf). Using a detailed radiative transfer model together with climatological input data for surface and atmospheric variables, the direct radiative effects of aerosols (DREs) were

  4. Impacts of Aerosol Direct Effects on the South Asian Climate: Assessment of Radiative Feedback Processes Using Model Simulations and Satellite/Surface Measurements

    NASA Technical Reports Server (NTRS)

    Wang, Sheng-Hsiang; Gautam, Ritesh; Lau, William K. M.; Tsay, Si-Chee; Sun, Wen-Yih; Kim, Kyu-Myong; Chern, Jiun-Dar; Hsu, Christina; Lin, Neng-Huei

    2011-01-01

    Current assessment of aerosol radiative effect is hindered by our incomplete knowledge of aerosol optical properties, especially absorption, and our current inability to quantify physical and microphysical processes. In this research, we investigate direct aerosol radiative effect over heavy aerosol loading areas (e.g., Indo-Gangetic Plains, South/East Asia) and its feedbacks on the South Asian climate during the pre-monsoon season (March-June) using the Purdue Regional Climate Model (PRCM) with prescribed aerosol data derived by the NASA Goddard Earth Observing System Model (GEOS-5). Our modeling domain covers South and East Asia (60-140E and 0-50N) with spatial resolutions of 45 km in horizontal and 28 layers in vertical. The model is integrated from 15 February to 30 June 2008 continuously without nudging (i.e., only forced by initial/boundary conditions). Two numerical experiments are conducted with and without the aerosol-radiation effects. Both simulations are successful in reproducing the synoptic patterns on seasonal-to-interannual time scales and capturing a pre-monsoon feature of the northward rainfall propagation over Indian region in early June which shown in Tropical Rainfall Measuring Mission (TRMM) observation. Preliminary result suggests aerosol-radiation interactions mainly alter surface-atmosphere energetics and further result in an adjustment of the vertical temperature distribution in lower atmosphere (below 700 hPa). The modifications of temperature and associated rainfall and circulation feedbacks on the regional climate will be discussed in the presentation.

  5. Can a coupled meteorology-chemistry model reproduce the historical trend in aerosol direct radiative effects over the Northern Hemisphere?

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    The ability of a coupled meteorology-chemistry model, i.e., Weather Research and Forecast and Community Multiscale Air Quality (WRF-CMAQ), to reproduce the historical trend in aerosol optical depth (AOD) and clear-sky shortwave radiation (SWR) over the Northern Hemisphere has been evaluated through a comparison of 21-year simulated results with observation-derived records from 1990 to 2010. Six satellite-retrieved AOD products including AVHRR, TOMS, SeaWiFS, MISR, MODIS-Terra and MODIS-Aqua as well as long-term historical records from 11 AERONET sites were used for the comparison of AOD trends. Clear-sky SWR products derived by CERES at both the top of atmosphere (TOA) and surface as well as surface SWR data derived from seven SURFRAD sites were used for the comparison of trends in SWR. The model successfully captured increasing AOD trends along with the corresponding increased TOA SWR (upwelling) and decreased surface SWR (downwelling) in both eastern China and the northern Pacific. The model also captured declining AOD trends along with the corresponding decreased TOA SWR (upwelling) and increased surface SWR (downwelling) in the eastern US, Europe and the northern Atlantic for the period of 2000-2010. However, the model underestimated the AOD over regions with substantial natural dust aerosol contributions, such as the Sahara Desert, Arabian Desert, central Atlantic and northern Indian Ocean. Estimates of the aerosol direct radiative effect (DRE) at TOA are comparable with those derived by measurements. Compared to global climate models (GCMs), the model exhibits better estimates of surface-aerosol direct radiative efficiency (Eτ). However, surface-DRE tends to be underestimated due to the underestimated AOD in land and dust regions. Further investigation of TOA-Eτ estimations as well as the dust module used for estimates of windblown-dust emissions is needed.

  6. 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

    NASA Astrophysics Data System (ADS)

    Hammer, Melanie S.; Martin, Randall V.; van Donkelaar, Aaron; Buchard, Virginie; Torres, Omar; Ridley, David A.; Spurr, Robert J. D.

    2016-03-01

    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 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 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 Ångström 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

  7. 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

    NASA Astrophysics Data System (ADS)

    Hammer, M. S.; Martin, R. V.; van Donkelaar, A.; Buchard, V.; Torres, O.; Ridley, D. A.; Spurr, R. J. D.

    2015-10-01

    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 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 5.62 to 5.68 years, thus

  8. 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

    NASA Technical Reports Server (NTRS)

    Hammer, Melanie S.; Martin, Randall V.; Donkelaar, Aaron van; Buchard, Virginie; Torres, Omar; Ridley, David A.; Spurr, Robert J. D.

    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

  9. Airborne Coarse Mode Aerosol Measurements with the CAS-DPOL Instrument: Effects of Particle Shape and Refractive Index and Implications for Radiative Transfer Estimate

    NASA Astrophysics Data System (ADS)

    Sauer, D. N.; Weinzierl, B.; Gasteiger, J.; Spanu, A.; Freudenthaler, V.; Gross, S.

    2015-12-01

    Each year huge amounts of mineral dust are mobilized in deserts and arid regions of the world and transported over large distances forming thick elevated aerosol layers with a substantial fraction of coarse mode particles. Optical properties of mineral dust, including the absorptive refractive index of some components, cause a significant effect on the atmospheric radiative energy balance from optical to infrared wavelengths. The aerosol characteristics, in particular its coarse mode size distribution, are modified during long-range transport by aging and deposition processes. This also affects the aerosol optical properties and therefore the effect on the atmospheric radiative energy budget. In-situ measurements of aerosol microphysical properties are essential to characterize those effects in order to be implemented in global climate models in parametrized form. However, in-situ measurements of airborne coarse mode aerosols such as mineral dust and volcanic ash are challenging and the measurements are usually affected by substantial uncertainties. In this work we use airborne measurements of mineral dust from our optical light-scattering spectrometer CAS-DPOL during SALTRACE 2013 to discuss the analysis of such data. We cover the effects of varying refractive index and particle shapes and develop recommendations for the configuration of the CAS-DPOL for aerosol studies. We also present an inversion method to derive coarse mode size distributions from light-scattering probes for mixtures of non-spherical, absorbing aerosols. The size distributions retrieved from the in-situ measurements are then validated using an independent analysis with a combination of sun-photometer and lidar data. We apply these methods to investigate the Saharan mineral dust particle size distributions measured on both sides of the Atlantic Ocean and discuss the influence of aerosol aging on the atmospheric radiative energy budget. With this example we also assess how the uncertainties

  10. 3D Cloud Radiative Effects on Aerosol Optical Thickness Retrievals in Cumulus Cloud Fields in the Biomass Burning Region in Brazil

    NASA Technical Reports Server (NTRS)

    Wen, Guo-Yong; Marshak, Alexander; Cahalan, Robert F.

    2004-01-01

    Aerosol amount in clear regions of a cloudy atmosphere is a critical parameter in studying the interaction between aerosols and clouds. Since the global cloud cover is about 50%, cloudy scenes are often encountered in any satellite images. Aerosols are more or less transparent, while clouds are extremely reflective in the visible spectrum of solar radiation. The radiative transfer in clear-cloudy condition is highly three- dimensional (3D). This paper focuses on estimating the 3D effects on aerosol optical thickness retrievals using Monte Carlo simulations. An ASTER image of cumulus cloud fields in the biomass burning region in Brazil is simulated in this study. The MODIS products (i-e., cloud optical thickness, particle effective radius, cloud top pressure, surface reflectance, etc.) are used to construct the cloud property and surface reflectance fields. To estimate the cloud 3-D effects, we assume a plane-parallel stratification of aerosol properties in the 60 km x 60 km ASTER image. The simulated solar radiation at the top of the atmosphere is compared with plane-parallel calculations. Furthermore, the 3D cloud radiative effects on aerosol optical thickness retrieval are estimated.

  11. Shortwave direct radiative effects of above cloud aerosols over global oceans derived from eight years of CALIOP and MODIS observations

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Meyer, K.; Yu, H.; Platnick, S.; Colarco, P.; Liu, Z.; Oreopoulos, L.

    2015-09-01

    In this paper, we studied the frequency of occurrence and shortwave direct radiative effects (DRE) of above-cloud aerosols (ACAs) over global oceans using eight years of collocated CALIOP and MODIS observations. Similar to previous work, we found high ACA occurrence in four regions: Southeast (SE) Atlantic region where ACAs are mostly light-absorbing aerosols, i.e., smoke and polluted dust according to CALIOP classification, originating from biomass burning over African Savanna; Tropical Northeast Atlantic and Arabian Sea where ACAs are predominantly windblown dust from the Sahara and Arabian desert, respectively; and Northwest Pacific where ACAs are mostly transported smoke and polluted dusts from Asian. From radiative transfer simulations based on CALIOP-MODIS observations and a set of the preselected aerosol optical models, we found the DREs of ACAs at the top of atmosphere (TOA) to be positive (i.e., warming) in the SE Atlantic and NW Pacific regions, but negative (i.e., cooling) in TNE Atlantic and Arabian Sea. The cancellation of positive and negative regional DREs results in a global ocean annual mean diurnally averaged cloudy-sky DRE of 0.015 W m-2 (range of -0.03 to 0.06 W m-2) at TOA. The DREs at surface and within atmosphere are -0.15 W m-2 (range of -0.09 to -0.21 W m-2), and 0.17 W m-2 (range of 0.11 to 0.24 W m-2), respectively. The regional and seasonal mean DREs are much stronger. For example, in the SE Atlantic region the JJA (July ~ August) seasonal mean cloudy-sky DRE is about 0.7 W m-2 (range of 0.2 to 1.2 W m-2) at TOA. The uncertainty in our DRE computations is mainly cause by the uncertainties in the aerosol optical properties, in particular aerosol absorption, and uncertainties in the CALIOP operational aerosol optical thickness retrieval. In situ and remotely sensed measurements of ACA from future field campaigns and satellite missions, and improved lidar retrieval algorithm, in particular vertical feature masking, would help reduce the

  12. Aerosol Direct Radiative Effect at the Top of the Atmosphere Over Cloud Free Ocean Derived from Four Years of MODIS Data

    NASA Technical Reports Server (NTRS)

    Remer, L. A.; Kaufman, Y. J.

    2006-01-01

    A four year record of MODIS spaceborne data provides a new measurement tool to assess the aerosol direct radiative effect at the top of the atmosphere. MODIS derives the aerosol optical thickness and microphysical properties from the scattered sunlight at 0.55-2.1 microns. The monthly MODIS data used here are accumulated measurements across a wide range of view and scattering angles and represent the aerosol s spectrally resolved angular properties. We use these data consistently to compute with estimated accuracy of +/-0.6W/sq m the reflected sunlight by the aerosol over global oceans in cloud free conditions. The MODIS high spatial resolution (0.5 km) allows observation of the aerosol impact between clouds that can be missed by other sensors with larger footprints. We found that over the clear-sky global ocean the aerosol reflected 5.3+/-0.6W/sq m with an average radiative efficiency of 49+/-2W/sq m per unit optical thickness. The seasonal and regional distribution of the aerosol radiative effects are discussed. The analysis adds a new measurement perspective to a climate change problem dominated so far by models.

  13. Spatially Refined Aerosol Direct Radiative Focusing Efficiencies

    EPA Science Inventory

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

  14. Spatially Refined Aerosol Direct Radiative Forcing Efficiencies

    EPA Science Inventory

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

  15. Stratospheric Aerosols for Solar Radiation Management

    NASA Astrophysics Data System (ADS)

    Kravitz, Ben

    SRM in the context of this entry involves placing a large amount of aerosols in the stratosphere to reduce the amount of solar radiation reaching the surface, thereby cooling the surface and counteracting some of the warming from anthropogenic greenhouse gases. The way this is accomplished depends on the specific aerosol used, but the basic mechanism involves backscattering and absorbing certain amounts of solar radiation aloft. Since warming from greenhouse gases is due to longwave (thermal) emission, compensating for this warming by reduction of shortwave (solar) energy is inherently imperfect, meaning SRM will have climate effects that are different from the effects of climate change. This will likely manifest in the form of regional inequalities, in that, similarly to climate change, some regions will benefit from SRM, while some will be adversely affected, viewed both in the context of present climate and a climate with high CO2 concentrations. These effects are highly dependent upon the means of SRM, including the type of aerosol to be used, the particle size and other microphysical concerns, and the methods by which the aerosol is placed in the stratosphere. SRM has never been performed, nor has deployment been tested, so the research up to this point has serious gaps. The amount of aerosols required is large enough that SRM would require a major engineering endeavor, although SRM is potentially cheap enough that it could be conducted unilaterally. Methods of governance must be in place before deployment is attempted, should deployment even be desired. Research in public policy, ethics, and economics, as well as many other disciplines, will be essential to the decision-making process. SRM is only a palliative treatment for climate change, and it is best viewed as part of a portfolio of responses, including mitigation, adaptation, and possibly CDR. At most, SRM is insurance against dangerous consequences that are directly due to increased surface air

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  17. A Global Model Simulation of Aerosol Effects of Surface Radiation Budget- Toward Understanding of the "Dimming to Brightening" Transition

    NASA Technical Reports Server (NTRS)

    Chin, Mian; Diehl, Thomas; Bian, Huisheng; Yu, Hongbin

    2008-01-01

    We present a global model study on the role aerosols play in the change of solar radiation at Earth's surface that transitioned from a decreasing (dimming) trend to an increasing (brightening) trend. Our primary objective is to understand the relationship between the long-term trends of aerosol emission, atmospheric burden, and surface solar radiation. More specifically, we use the recently compiled comprehensive global emission datasets of aerosols and precursors from fuel combustion, biomass burning, volcanic eruptions and other sources from 1980 to 2006 to simulate long-term variations of aerosol distributions and optical properties, and then calculate the multi-decadal changes of short-wave radiative fluxes at the surface and at the top of the atmosphere by coupling the GOCART model simulated aerosols with the Goddard radiative transfer model. The model results are compared with long-term observational records from ground-based networks and satellite data. We will address the following critical questions: To what extent can the observed surface solar radiation trends, known as the transition from dimming to brightening, be explained by the changes of anthropogenic and natural aerosol loading on global and regional scales? What are the relative contributions of local emission and long-range transport to the surface radiation budget and how do these contributions change with time?

  18. Radiative Impacts of Elevated Aerosol Layers from Different Origins

    NASA Astrophysics Data System (ADS)

    Sauer, D. N.; Weinzierl, B.; Gasteiger, J.; Heimerl, K.

    2014-12-01

    Aerosol particles are omnipresent in the Earth's atmosphere and have important impacts on weather and climate by their effects on the atmospheric radiative balance. With the advent of more and more sophisticated representations of atmospheric processes in earth system models, the lack of reliable input data on aerosols leads to significant uncertainties in the prediction of future climate scenarios. In recent years large discrepancies in radiative forcing estimates from aerosol layers in modeling studies have been revealed emphasizing the need for detailed and systematic observations of aerosols. Airborne in-situ measurements represent an important pillar for validating both model results and retrievals of aerosol distributions and properties from remote sensing methods on global scales. However, detailed observations are challenging and therefore are subject to substantial uncertainties themselves. Here we use data from airborne in-situ measurements of elevated aerosol layers from various field experiments in different regions of the world. The data set includes Saharan mineral dust layers over Africa, the Atlantic Ocean and the Caribbean from the SALTRACE and the SAMUM campaigns as well as long-range transported biomass burning aerosol layers from wild fires in the Sahel region and North America measured over the tropical Atlantic Ocean, Europe and the Arctic detected during SAMUM2, CONCERT2011, DC3 and ACCESS 2012. We aim to characterize the effects of the measured aerosol layers, in particular with respect to ageing, mixing state and vertical structure, on the overall atmospheric radiation budget as well as local heating and cooling rates. We use radiative transfer simulations of short and long-wave radiation and aerosol optical properties derived in a consistent way from the in-situ observations of microphysical properties using T-matrix calculations. The results of this characterization will help to improve the parameterization of the effects of elevated

  19. Sensitivity of clear-sky direct radiative effect of the aerosol to micro-physical properties by using 6SV radiative transfer model: preliminary results

    NASA Astrophysics Data System (ADS)

    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

  20. An assessment of the quality of aerosol retrievals over the Red Sea and evaluation of the climatological cloud-free dust direct radiative effect in the region

    NASA Astrophysics Data System (ADS)

    Brindley, H.; Osipov, S.; Bantges, R.; Smirnov, A.; Banks, J.; Levy, R.; Jish Prakash, P.; Stenchikov, G.

    2015-10-01

    Ground-based and satellite observations are used in conjunction with the Rapid Radiative Transfer Model (RRTM) to assess climatological aerosol loading and the associated cloud-free aerosol direct radiative effect (DRE) over the Red Sea. Aerosol optical depth (AOD) retrievals from the Moderate Resolution Imaging Spectroradiometer and Spinning Enhanced Visible and InfraRed Imager (SEVIRI) instruments are first evaluated via comparison with ship-based observations. Correlations are typically better than 0.9 with very small root-mean-square and bias differences. Calculations of the DRE along the ship cruises using RRTM also show good agreement with colocated estimates from the Geostationary Earth Radiation Budget instrument if the aerosol asymmetry parameter is adjusted to account for the presence of large particles. A monthly climatology of AOD over the Red Sea is then created from 5 years of SEVIRI retrievals. This shows enhanced aerosol loading and a distinct north to south gradient across the basin in the summer relative to the winter months. The climatology is used with RRTM to estimate the DRE at the top and bottom of the atmosphere and the atmospheric absorption due to dust aerosol. These climatological estimates indicate that although longwave effects can reach tens of W m-2, shortwave cooling typically dominates the net radiative effect over the Sea, being particularly pronounced in the summer, reaching 120 W m-2 at the surface. The spatial gradient in summertime AOD is reflected in the radiative effect at the surface and in associated differential heating by aerosol within the atmosphere above the Sea. This asymmetric effect is expected to exert a significant influence on the regional atmospheric and oceanic circulation.

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  2. The impacts of volcanic aerosol on stratospheric ozone and the Northern Hemisphere polar vortex: separating radiative-dynamical changes from direct effects due to enhanced aerosol heterogeneous chemistry

    NASA Astrophysics Data System (ADS)

    Muthers, S.; Arfeuille, F.; Raible, C. C.; Rozanov, E.

    2015-10-01

    After major volcanic eruptions the enhanced aerosol causes ozone changes due to greater heterogeneous chemistry on the particle surfaces (HET-AER) and from dynamical effects related to the radiative heating of the lower stratosphere (RAD-DYN). We carry out a series of experiments with an atmosphere-ocean-chemistry-climate model to assess how these two processes change stratospheric ozone and Northern Hemispheric (NH) polar vortex dynamics. Ensemble simulations are performed under present day and preindustrial conditions, and with aerosol forcings representative of different eruption strength, to investigate changes in the response behaviour. We show that the halogen component of the HET-AER effect dominates under present-day conditions with a global reduction of ozone (-21 DU for the strongest eruption) particularly at high latitudes, whereas the HET-AER effect increases stratospheric ozone due to N2O5 hydrolysis in a preindustrial atmosphere (maximum anomalies +4 DU). The halogen-induced ozone changes in the present-day atmosphere offset part of the strengthening of the NH polar vortex during mid-winter (reduction of up to -16 m s-1 in January) and slightly amplify the dynamical changes in the polar stratosphere in late winter (+11 m s-1 in March). The RAD-DYN mechanism leads to positive column ozone anomalies which are reduced in a present-day atmosphere by amplified polar ozone depletion (maximum anomalies +12 and +18 DU for present day and preindustrial, respectively). For preindustrial conditions, the ozone response is consequently dominated by RAD-DYN processes, while under present-day conditions, HET-AER effects dominate. The dynamical response of the stratosphere is dominated by the RAD-DYN mechanism showing an intensification of the NH polar vortex in winter (up to +10 m s-1 in January). Ozone changes due to the RAD-DYN mechanism slightly reduce the response of the polar vortex after the eruption under present-day conditions.

  3. 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

    NASA Astrophysics Data System (ADS)

    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

  4. Effects of aerosol-radiation interaction on precipitation during biomass-burning season in East China

    NASA Astrophysics Data System (ADS)

    Huang, Xin; Ding, Aijun; Liu, Lixia; Liu, Qiang; Ding, Ke; Niu, Xiaorui; Nie, Wei; Xu, Zheng; Chi, Xuguang; Wang, Minghuai; Sun, Jianning; Guo, Weidong; Fu, Congbin

    2016-08-01

    Biomass burning is a main source for primary carbonaceous particles in the atmosphere and acts as a crucial factor that alters Earth's energy budget and balance. It is also an important factor influencing air quality, regional climate and sustainability in the domain of Pan-Eurasian Experiment (PEEX). During the exceptionally intense agricultural fire season in mid-June 2012, accompanied by rapidly deteriorating air quality, a series of meteorological anomalies was observed, including a large decline in near-surface air temperature, spatial shifts and changes in precipitation in Jiangsu province of East China. To explore the underlying processes that link air pollution to weather modification, we conducted a numerical study with parallel simulations using the fully coupled meteorology-chemistry model WRF-Chem with a high-resolution emission inventory for agricultural fires. Evaluation of the modeling results with available ground-based measurements and satellite retrievals showed that this model was able to reproduce the magnitude and spatial variations of fire-induced air pollution. During the biomass-burning event in mid-June 2012, intensive emission of absorbing aerosols trapped a considerable part of solar radiation in the atmosphere and reduced incident radiation reaching the surface on a regional scale, followed by lowered surface sensible and latent heat fluxes. The perturbed energy balance and re-allocation gave rise to substantial adjustments in vertical temperature stratification, namely surface cooling and upper-air heating. Furthermore, an intimate link between temperature profile and small-scale processes like turbulent mixing and entrainment led to distinct changes in precipitation. On the one hand, by stabilizing the atmosphere below and reducing the surface flux, black carbon-laden plumes tended to dissipate daytime cloud and suppress the convective precipitation over Nanjing. On the other hand, heating aloft increased upper-level convective

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

    SciTech Connect

    McFarlane, Sally A.; Kassianov, Evgueni I.; Barnard, James C.; Flynn, Connor J.; Ackerman, Thomas P.

    2009-03-18

    This study presents ground-based remote sensing measurements of aerosol optical properties and corresponding shortwave surface radiative effect calculations for the deployment of the Atmospheric Radiation Measurement (ARM) Program’s Mobile Facility (AMF) to Niamey, Niger during 2006. Aerosol optical properties including aerosol optical depth (AOD), single scattering albedo (SSA), and asymmetry parameter (AP) were derived from multi-filter rotating shadowband radiometer (MFRSR) measurements during the two dry seasons (Jan-Apr and Oct-Dec) at Niamey. The vertical distribution of aerosol extinction was derived from the collocated micropulse lidar (MPL). The aerosol optical properties and vertical distribution of extinction varied significantly throughout the year, with higher AOD, lower SSA, and deeper aerosol layers during the Jan-Apr time period, when biomass burning aerosol layers were more frequent. Using the retrieved aerosol properties and vertical extinction profiles, broadband shortwave surface fluxes and atmospheric heating rate profiles were calculated. Corresponding calculations with no aerosol were used to estimate the aerosol direct radiative effect at the surface. Comparison of the calculated surface fluxes to observed fluxes for non-cloudy periods indicated that the remote sensing retrievals provided a reasonable estimation of the optical properties, with mean differences between calculated and observed fluxes of less than 5 W/m2 and RMS differences less than 25 W/m2. Sensitivity tests for a particular case study showed that the observed fluxes could be matched with variations of < 10% in the inputs to the radiative transfer model. We estimated the daily-averaged aerosol radiative effect at the surface by subtracting the clear calculations from the aerosol calculations. The average daily SW aerosol radiative effect over the study period was -27 W/m2, which is comparable to values estimated from satellite data and from climate models with sophisticated

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

    SciTech Connect

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

    2012-07-25

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

  7. Estimation of aerosol optical properties and radiative effects in the Ganga basin, northern India, during the wintertime

    NASA Astrophysics Data System (ADS)

    Dey, Sagnik; Tripathi, S. N.

    2007-02-01

    An aerosol model has been developed using mass size distributions of various chemical components measured at Kanpur (an urban location in the Ganga basin, GB, in northern India) and applied to estimate the radiative effects of the aerosols over the entire GB during the winter season. The number size distribution of various species was derived from the measured mass concentration, and the optical properties were calculated using Mie theory. The maximum anthropogenic contribution to the total extinction was estimated to be ˜83%. The relative contributions of various species to the aerosol optical depth (AOD) at 0.5 μm are in the following order: (NH4)2SO4 (nss-SO4, 30%), nitrate (NO3-, 24%), salt (mainly NaCl and KCl, 18%), dust (17%) and black carbon (BC, 11%). Relative contribution of nss-SO4, NO3- and salt to the calculated AOD decreases with wavelength, and that of dust increases with wavelength, whereas BC contribution is spectrally insensitive. The extinction coefficient strongly depends on the RH, as the scattering by fine mode fraction, which contributes 88% to the total extinction, is enhanced at high ambient RH. The spectral variation of absorption coefficient indicates that the most likely source of BC in this region is fossil fuel. The spectral variation of single scattering albedo (SSA) in the coarse mode fraction suggests mixing of BC and dust particles. During the observational period, the mean shortwave (SW) clear sky top of the atmosphere (TOA) and surface forcing over Kanpur are estimated to be -13 ± 3 and -43 ± 8 W m-2, respectively. The corresponding longwave forcings are 3.6 ± 0.7 and 2.9 ± 0.6 W m-2, respectively. Mean AOD at 0.55 μm over the GB as derived from MODIS data is 0.36 ± 0.14. Extending our model over the entire GB, the net mean TOA and surface forcing become -6.4 and -30.2 W m-2 (with overall ˜15% uncertainty). This results in high atmospheric absorption (+23.8 W m-2), translating into a heating rate of 0.67 K day-1. The SW

  8. Assessment of multi-decadal WRF-CMAQ simulations for understanding direct aerosol effects on radiation "brightening" in the United States

    NASA Astrophysics Data System (ADS)

    Gan, C.-M.; Pleim, J.; Mathur, R.; Hogrefe, C.; Long, C. N.; Xing, J.; Wong, D.; Gilliam, R.; Wei, C.

    2015-07-01

    Multi-decadal simulations with the coupled WRF-CMAQ model have been conducted to systematically investigate the changes in anthropogenic emissions of SO2 and NOx over the past 21 years (1990-2010) across the United States (US), their impacts on anthropogenic aerosol loading over North America, and subsequent impacts on regional radiation budgets. In particular, this study attempts to determine the consequences of the changes in tropospheric aerosol burden arising from substantial reductions in emissions of SO2 and NOx associated with control measures under the Clean Air Act (CAA) especially on trends in solar radiation. Extensive analyses conducted by Gan et al. (2014) utilizing observations (e.g. SURFRAD, CASTNET, IMPROVE and ARM) over the past 16 years (1995-2010) indicate a shortwave (SW) radiation (both all-sky and clear-sky) "brightening" in the US. The relationship of the radiation brightening trend with decreases in the aerosol burden is less apparent in the western US. One of the main reasons for this is that the emission controls under the CAA were aimed primarily at reducing pollutants in areas violating national air quality standards, most of which were located in the eastern US while the relatively less populated areas in the western US were less polluted at the beginning of this study period. Comparisons of model results with observations of aerosol optical depth (AOD), aerosol concentration, and radiation demonstrate that the coupled WRF-CMAQ model is capable of replicating the trends well even through it tends to underestimate the AOD. In particular, the sulfate concentration predictions were well matched with the observations. The discrenpancies found in the clear-sky diffuse SW radiation are likely due to several factors such as potential increase of ice particles associated with increasing air traffic, the definition of "clear-sky" in the radiation retrieval methodology and aerosol semi-direct and/or indirect effects which cannot be readily

  9. Experimental Characterization of Radiation Forcing due to Atmospheric Aerosols

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  10. A Novel Method for Estimating Shortwave Direct Radiative Effect of Above-cloud Aerosols over Ocean Using CALIOP and MODIS Data

    NASA Technical Reports Server (NTRS)

    Zhang, Z.; Meyer, K.; Platnick, S.; Oreopoulos, L.; Lee, D.; Yu, H.

    2013-01-01

    This paper describes an efficient and unique method for computing the shortwave direct radiative effect (DRE) of aerosol residing above low-level liquid-phase clouds using CALIOP and MODIS data. It accounts for the overlapping of aerosol and cloud rigorously by utilizing the joint histogram of cloud optical depth and cloud top pressure. Effects of sub-grid scale cloud and aerosol variations on DRE are accounted for. It is computationally efficient through using grid-level cloud and aerosol statistics, instead of pixel-level products, and a pre-computed look-up table in radiative transfer calculations. We verified that for smoke over the southeast Atlantic Ocean the method yields a seasonal mean instantaneous shortwave DRE that generally agrees with more rigorous pixel-level computation within 4%. We have also computed the annual mean instantaneous shortwave DRE of light-absorbing aerosols (i.e., smoke and polluted dust) over global ocean based on 4 yr of CALIOP and MODIS data. We found that the variability of the annual mean shortwave DRE of above-cloud light-absorbing aerosol is mainly driven by the optical depth of the underlying clouds.

  11. Advancing Solar Irradiance Measurement for Climate-Related Studies: Accurate Constraint on Direct Aerosol Radiative Effect (DARE)

    NASA Technical Reports Server (NTRS)

    Tsay, Si-Chee; Ji, Q. Jack

    2011-01-01

    Earth's climate is driven primarily by solar radiation. As summarized in various IPCC reports, the global average of radiative forcing for different agents and mechanisms, such as aerosols or CO2 doubling, is in the range of a few W/sq m. However, when solar irradiance is measured by broadband radiometers, such as the fleet of Eppley Precision Solar Pyranometers (PSP) and equivalent instrumentation employed worldwide, the measurement uncertainty is larger than 2% (e.g., WMO specification of pyranometer, 2008). Thus, out of the approx. 184 W/sq m (approx.263 W/sq m if cloud-free) surface solar insolation (Trenberth et al. 2009), the measurement uncertainty is greater than +/-3.6 W/sq m, overwhelming the climate change signals. To discern these signals, less than a 1 % measurement uncertainty is required and is currently achievable only by means of a newly developed methodology employing a modified PSP-like pyranometer and an updated calibration equation to account for its thermal effects (li and Tsay, 2010). In this talk, we will show that some auxiliary measurements, such as those from a collocated pyrgeometer or air temperature sensors, can help correct historical datasets. Additionally, we will also demonstrate that a pyrheliometer is not free of the thermal effect; therefore, comparing to a high cost yet still not thermal-effect-free "direct + diffuse" approach in measuring surface solar irradiance, our new method is more economical, and more likely to be suitable for correcting a wide variety of historical datasets. Modeling simulations will be presented that a corrected solar irradiance measurement has a significant impact on aerosol forcing, and thus plays an important role in climate studies.

  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

    NASA Astrophysics Data System (ADS)

    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. Cloud-resolving modelling of aerosol indirect effects in idealised radiative-convective equilibrium with interactive and fixed sea surface temperature

    NASA Astrophysics Data System (ADS)

    Khairoutdinov, M. F.; Yang, C.-E.

    2013-04-01

    The study attempts to evaluate the aerosol indirect effects over tropical oceans in regions of deep convection applying a three-dimensional cloud-resolving model run over a doubly-periodic domain. The Tropics are modelled using a radiative-convective equilibrium idealisation when the radiation, turbulence, cloud microphysics and surface fluxes are explicitly represented while the effects of large-scale circulation are ignored. The aerosol effects are modelled by varying the number concentration of cloud condensation nuclei (CCN) at 1% supersaturation, which serves as a proxy for the aerosol amount in the environment, over a wide range, from pristine maritime (50 cm-3) to polluted (1000 cm-3) conditions. No direct effects of aerosol on radiation are included. Two sets of simulations have been run: fixed (non-interactive) sea surface temperature (SST) and interactive SST as predicted by a simple slab-ocean model responding to the surface radiative fluxes and surface enthalpy flux. Both sets of experiments agree on the tendency of increased aerosol concentrations to make the shortwave cloud forcing more negative and reduce the longwave cloud forcing in response to increasing CCN concentration. These, in turn, tend to cool the SST in interactive-SST case. It is interesting that the absolute change of the SST and most other bulk quantities depends only on relative change of CCN concentration; that is, same SST change can be the result of doubling CCN concentration regardless of clean or polluted conditions. It is found that the 10-fold increase of CCN concentration can cool the SST by as much as 1.5 K. This is quite comparable to 2.1-2.3 K SST warming obtained in a simulation for clean maritime conditions, but doubled CO2 concentration. Assuming the aerosol concentration has increased from preindustrial time by 30%, the radiative forcing due to indirect aerosol effects is estimated to be -0.3 W m-2. It is found that the indirect aerosol effect is dominated by the first

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  15. Radiative effects of lower stratospheric volcanic and carbon aerosol as simulated by the CCM EMAC for 2002 to 2011

    NASA Astrophysics Data System (ADS)

    Brühl, Christoph; Lelieveld, Jos; Höpfner, Michael

    2015-04-01

    A 10-year simulation with the chemistry climate model EMAC with interactive aerosol module shows that medium and smaller volcanic eruptions contribute significantly to radiative forcing and also radiative heating of the lower stratosphere. This simulation includes about 140 eruptions mostly derived from SO2 observed by MIPAS on ENVISAT. Organic and black carbon from biomass burning contributes considerably to radiative heating of the lower stratosphere, notably in monsoon regions, even if its contribution to total aerosol optical depth of the stratosphere is small. We also show that the simulated stratospheric optical depth and radiative forcing at the tropopause is consistent with the corresponding values derived from SAGE and OSIRIS satellite observations, and that the inclusion of smaller eruptions is necessary.

  16. Can a coupled meteorology–chemistry model reproduce the historical trend in aerosol direct radiative effects over the Northern Hemisphere?

    EPA Science Inventory

    The ability of a coupled meteorology–chemistry model, i.e., Weather Research and Forecast and Community Multiscale Air Quality (WRF-CMAQ), to reproduce the historical trend in aerosol optical depth (AOD) and clear-sky shortwave radiation (SWR) over the Northern Hemisphere h...

  17. SGPGET: AN SBDART Module for Aerosol Radiative Transfer

    SciTech Connect

    McComiskey, A.; Ricchiazzi, P.; Ogren, J.A.; Dutton, E.

    2005-03-18

    Quantification of the aerosol direct effect and climate sensitivity requires accurate estimates of optical properties as inputs to a radiative transfer model. Long-term measurements of aerosol properties at the Southern Great Plains (SGP) site can be used as an improvement over a best guess or global average for optical properties (e.g., asymmetry factor of 0.7) used in Atmospheric Radiation Measurement (ARM) products such as the Broadband Heating Rate Profile VAP. To make this information readily available to the ARM community and others, an add-on module for a commonly used radiative transfer model, SBDART (Ricchiazzi et al. 1998), is being developed. A look up table and algorithm will provide aerosol related model inputs including aerosol optical and atmospheric state properties at high temporal resolution. These inputs can be used in conjunction with any mode of operation and with any other information, for example, cloud properties, in SBDART or any other radiative transfer model. Aerosol properties measured at three visible wavelengths are extrapolated so that flux calculations can be made in any desired wavelength across the shortwave spectrum. Several sources of uncertainty contribute to degraded accuracy of the aerosol property estimation. The effect of these uncertainties is shown through error analysis and comparisons of modeled and observed surface irradiance. A module is also being developed for the North Slope of Alaska site.

  18. Aerosol radiative forcing in the European Skynet Radiometers network

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  19. Top-of-Atmosphere Direct Radiative Effect of Aerosols from the Clouds and the Earth's Radiant Energy System Satellite Instrument (CERES)

    NASA Technical Reports Server (NTRS)

    Loeb, N. G.; Kato, S.

    2002-01-01

    Nine months of CERES/TRMM broadband fluxes combined with VIRS high-resolution imager measurements are used to estimate the daily average direct radiative effect of aerosols for clear-sky conditions over the tropical oceans. On average, aerosols have a cooling effect over the tropics of 4.6 +/- 1 W/sq m. The magnitude is approx.2 W/sq m smaller over the southern tropical oceans than it is over northern tropical oceans. The direct effect derived from CERES is highly correlated with coincident aerosol optical depth retrievals inferred from 0.63 microns VIRS radiances (correlation coefficient of 0.96). The slope of the regression line is approx. -32 W/sq m/t over the equatorial Pacific Ocean, but changes both regionally and seasonally, depending on the aerosol characteristics. Near sources of biomass burning and desert dust, the aerosol direct effect reaches -25 W sq m to -30 W/sq m. The direct effect from CERES also shows a dependence on wind speed. The reason for this dependence is unclear-it may be due to increased aerosol (e.g. sea-salt or aerosol transport) or increased surface reflection (e.g. due to whitecaps). The uncertainty in the tropical average direct effect from CERES is approx. 1 W/sq m (approx. 20%) due mainly to cloud contamination, the radiance-to-flux conversion, and instrument calibration. By comparison, uncertainties in the direct effect from the ERBE and CERES "ERBE-Like" products are a factor of 3 to 5 larger.

  20. 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

    NASA Astrophysics Data System (ADS)

    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

  1. Estimating the Direct Radiative Effect of Absorbing Aerosols Overlying Marine Boundary Layer Clouds in the Southeast Atlantic Using MODIS and CALIOP

    NASA Technical Reports Server (NTRS)

    Meyer, Kerry; Platnick, Steven; Oreopoulos, Lazaros; Lee, Dongmin

    2013-01-01

    Absorbing aerosols such as smoke strongly absorb solar radiation, particularly at ultraviolet and visible/near-infrared (VIS/NIR) wavelengths, and their presence above clouds can have considerable implications. It has been previously shown that they have a positive (i.e., warming) direct aerosol radiative effect (DARE) when overlying bright clouds. Additionally, they can cause biased passive instrument satellite retrievals in techniques that rely on VIS/NIR wavelengths for inferring the cloud optical thickness (COT) and effective radius (re) of underlying clouds, which can in turn yield biased above-cloud DARE estimates. Here we investigate Moderate Resolution Imaging Spectroradiometer (MODIS) cloud optical property retrieval biases due to overlying absorbing aerosols observed by Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and examine the impact of these biases on above-cloud DARE estimates. The investigation focuses on a region in the southeast Atlantic Ocean during August and September (2006-2011), where smoke from biomass burning in southern Africa overlies persistent marine boundary layer stratocumulus clouds. Adjusting for above-cloud aerosol attenuation yields increases in the regional mean liquid COT (averaged over all ocean-only liquid clouds) by roughly 6%; mean re increases by roughly 2.6%, almost exclusively due to the COT adjustment in the non-orthogonal retrieval space. It is found that these two biases lead to an underestimate of DARE. For liquid cloud Aqua MODIS pixels with CALIOP-observed above-cloud smoke, the regional mean above-cloud radiative forcing efficiency (DARE per unit aerosol optical depth (AOD)) at time of observation (near local noon for Aqua overpass) increases from 50.9Wm(sup-2)AOD(sup-1) to 65.1Wm(sup-2)AOD(sup -1) when using bias-adjusted instead of nonadjusted MODIS cloud retrievals.

  2. Radiative Effects of Saharan Mineral Dust Aerosols on the Structure of African Easterly Waves

    NASA Astrophysics Data System (ADS)

    Bercos-Hickey, E.; Nathan, T. R.; Chen, S. H.

    2014-12-01

    How Saharan mineral dust affects the structure of African easterly waves (AEWs) is an outstanding scientific question. Addressing this question is important because AEWs often serve as precursors to the development of tropical storms off of West Africa. In this study, the Weather Research and Forecasting Dust (WRFD) model is used to examine the radiative effects of Saharan dust on the structure of AEWs that occurred in July 1995. Two numerical experiments are conducted. The first (control) experiment uses the standard WRF model in the absence of dust. The second experiment is identical to the first, but includes the transport and radiative effects of dust. Dust is modeled by 12 continuity equations for dust-sized particles that represent the spectrum of mineral dust in the atmosphere. Analysis and comparison of the no-dust and dust experiments show that Saharan dust significantly affects the structure of AEWs. For example, a spectral density analysis of the AEWs shows that dust causes higher peak power during the 3 to 6 day period at 700mb. For the meridional wind over Dakar in West Africa, the dust causes the power to increase by about 82% and to shift to a lower frequency by about a half day. Covariance plots show spatial shifts, structural changes and magnitude differences in the AEWs between the dust and no dust experiments. Calculations show that the dust causes the maximum in momentum flux to increase by about 4%. The African easterly jet (AEJ) also shows changes between the dust and no dust experiments. Ongoing work includes quantifying the structural changes of AEWs and the AEJ.

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

    EPA Science Inventory

    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...

  4. Evaluation of aerosol indirect radiative forcing in MIRAGE

    NASA Astrophysics Data System (ADS)

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

    2001-03-01

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

  5. Evaluation of Aerosol Indirect Radiative Forcing in MIRAGE

    SciTech Connect

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

    2001-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

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

    SciTech Connect

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

    2014-08-01

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

  9. Simulated 2050 aviation radiative forcing from contrails and aerosols

    NASA Astrophysics Data System (ADS)

    Chen, Chih-Chieh; Gettelman, Andrew

    2016-06-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  12. Assessment of multi-decadal WRF-CMAQ simulations for understanding direct aerosol effects on radiation "brightening" in the United States

    DOE PAGESBeta

    Gan, C.-M.; Pleim, J.; Mathur, R.; Hogrefe, C.; Long, C. N.; Xing, J.; Wong, D.; Gilliam, R.; Wei, C.

    2015-07-01

    Multi-decadal simulations with the coupled WRF-CMAQ model have been conducted to systematically investigate the changes in anthropogenic emissions of SO2 and NOx over the past 21 years (1990–2010) across the United States (US), their impacts on anthropogenic aerosol loading over North America, and subsequent impacts on regional radiation budgets. In particular, this study attempts to determine the consequences of the changes in tropospheric aerosol burden arising from substantial reductions in emissions of SO2 and NOx associated with control measures under the Clean Air Act (CAA) especially on trends in solar radiation. Extensive analyses conducted by Gan et al. (2014) utilizingmore » observations (e.g. SURFRAD, CASTNET, IMPROVE and ARM) over the past 16 years (1995–2010) indicate a shortwave (SW) radiation (both all-sky and clear-sky) "brightening" in the US. The relationship of the radiation brightening trend with decreases in the aerosol burden is less apparent in the western US. One of the main reasons for this is that the emission controls under the CAA were aimed primarily at reducing pollutants in areas violating national air quality standards, most of which were located in the eastern US while the relatively less populated areas in the western US were less polluted at the beginning of this study period. Comparisons of model results with observations of aerosol optical depth (AOD), aerosol concentration, and radiation demonstrate that the coupled WRF-CMAQ model is capable of replicating the trends well even through it tends to underestimate the AOD. In particular, the sulfate concentration predictions were well matched with the observations. The discrenpancies found in the clear-sky diffuse SW radiation are likely due to several factors such as potential increase of ice particles associated with increasing air traffic, the definition of "clear-sky" in the radiation retrieval methodology and aerosol semi-direct and/or indirect effects which cannot be

  13. Assessment of long-term WRF-CMAQ simulations for understanding direct aerosol effects on radiation "brightening" in the United States

    NASA Astrophysics Data System (ADS)

    Gan, C.-M.; Pleim, J.; Mathur, R.; Hogrefe, C.; Long, C. N.; Xing, J.; Wong, D.; Gilliam, R.; Wei, C.

    2015-11-01

    Long-term simulations with the coupled WRF-CMAQ (Weather Research and Forecasting-Community Multi-scale Air Quality) model have been conducted to systematically investigate the changes in anthropogenic emissions of SO2 and NOx over the past 16 years (1995-2010) across the United States (US), their impacts on anthropogenic aerosol loading over North America, and subsequent impacts on regional radiation budgets. In particular, this study attempts to determine the consequences of the changes in tropospheric aerosol burden arising from substantial reductions in emissions of SO2 and NOx associated with control measures under the Clean Air Act (CAA) especially on trends in solar radiation. Extensive analyses conducted by Gan et al. (2014a) utilizing observations (e.g., SURFRAD, CASTNET, IMPROVE, and ARM) over the past 16 years (1995-2010) indicate a shortwave (SW) radiation (both all-sky and clear-sky) "brightening" in the US. The relationship of the radiation brightening trend with decreases in the aerosol burden is less apparent in the western US. One of the main reasons for this is that the emission controls under the CAA were aimed primarily at reducing pollutants in areas violating national air quality standards, most of which were located in the eastern US, while the relatively less populated areas in the western US were less polluted at the beginning of this study period. Comparisons of model results with observations of aerosol optical depth (AOD), aerosol concentration, and radiation demonstrate that the coupled WRF-CMAQ model is capable of replicating the trends well even though it tends to underestimate the AOD. In particular, the sulfate concentration predictions were well matched with the observations. The discrepancies found in the clear-sky diffuse SW radiation are likely due to several factors such as the potential increase of ice particles associated with increasing air traffic, the definition of "clear-sky" in the radiation retrieval methodology, and

  14. Assessment of long-term WRF–CMAQ simulations for understanding direct aerosol effects on radiation "brightening" in the United States

    DOE PAGESBeta

    Gan, C.-M.; Pleim, J.; Mathur, R.; Hogrefe, C.; Long, C. N.; Xing, J.; Wong, D.; Gilliam, R.; Wei, C.

    2015-11-03

    Long-term simulations with the coupled WRF–CMAQ (Weather Research and Forecasting–Community Multi-scale Air Quality) model have been conducted to systematically investigate the changes in anthropogenic emissions of SO2 and NOx over the past 16 years (1995–2010) across the United States (US), their impacts on anthropogenic aerosol loading over North America, and subsequent impacts on regional radiation budgets. In particular, this study attempts to determine the consequences of the changes in tropospheric aerosol burden arising from substantial reductions in emissions of SO2 and NOx associated with control measures under the Clean Air Act (CAA) especially on trends in solar radiation. Extensive analysesmore » conducted by Gan et al. (2014a) utilizing observations (e.g., SURFRAD, CASTNET, IMPROVE, and ARM) over the past 16 years (1995–2010) indicate a shortwave (SW) radiation (both all-sky and clear-sky) "brightening" in the US. The relationship of the radiation brightening trend with decreases in the aerosol burden is less apparent in the western US. One of the main reasons for this is that the emission controls under the CAA were aimed primarily at reducing pollutants in areas violating national air quality standards, most of which were located in the eastern US, while the relatively less populated areas in the western US were less polluted at the beginning of this study period. Comparisons of model results with observations of aerosol optical depth (AOD), aerosol concentration, and radiation demonstrate that the coupled WRF–CMAQ model is capable of replicating the trends well even though it tends to underestimate the AOD. In particular, the sulfate concentration predictions were well matched with the observations. The discrepancies found in the clear-sky diffuse SW radiation are likely due to several factors such as the potential increase of ice particles associated with increasing air traffic, the definition of "clear-sky" in the radiation retrieval

  15. Aerosol properties computed from aircraft-based observations during the ACE- Asia campaign. 2; A case study of lidar ratio closure and aerosol radiative effects

    NASA Technical Reports Server (NTRS)

    Kuzmanoski, Maja; Box, M. A.; Schmid, B.; Box, G. P.; Wang, J.; Russell, P. B.; Bates, D.; Jonsson, H. H.; Welton, Ellsworth J.; Flagan, R. C.

    2005-01-01

    For a vertical profile with three distinct layers (marine boundary, pollution and dust), observed during the ACE-Asia campaign, we carried out a comparison between the modeled lidar ratio vertical profile and that obtained from collocated airborne NASA AATS-14 sunphotometer and shipborne Micro-Pulse Lidar (MPL) measurements. Vertically resolved lidar ratio was calculated from two size distribution vertical profiles - one obtained by inversion of sunphotometer-derived extinction spectra, and one measured in-situ - combined with the same refractive index model based on aerosol chemical composition. The aerosol model implies single scattering albedos of 0.78 - 0.81 and 0.93 - 0.96 at 0.523 microns (the wavelength of the lidar measurements), in the pollution and dust layers, respectively. The lidar ratios calculated from the two size distribution profiles have close values in the dust layer; they are however, significantly lower than the lidar ratios derived from combined lidar and sunphotometer measurements, most probably due to the use of a simple nonspherical model with a single particle shape in our calculations. In the pollution layer, the two size distribution profiles yield generally different lidar ratios. The retrieved size distributions yield a lidar ratio which is in better agreement with that derived from lidar/sunphotometer measurements in this layer, with still large differences at certain altitudes (the largest relative difference was 46%). We explain these differences by non-uniqueness of the result of the size distribution retrieval and lack of information on vertical variability of particle refractive index. Radiative transfer calculations for this profile showed significant atmospheric radiative forcing, which occurred mainly in the pollution layer. We demonstrate that if the extinction profile is known then information on the vertical structure of absorption and asymmetry parameter is not significant for estimating forcing at TOA and the surface

  16. A contribution of brown carbon aerosol to the aerosol light absorption and its radiative forcing in East Asia

    NASA Astrophysics Data System (ADS)

    Park, Rokjin J.; Kim, Minjoong J.; Jeong, Jaein I.; Youn, Daeok; Kim, Sangwoo

    2010-04-01

    Brown carbon aerosols were recently found to be ubiquitous and effectively absorb solar radiation. We use a 3-D global chemical transport model (GEOS-Chem) together with aircraft and ground based observations from the TRACE-P and the ACE-Asia campaigns to examine the contribution of brown carbon aerosol to the aerosol light absorption and its climatic implication over East Asia in spring 2001. We estimated brown carbon aerosol concentrations in the model using the mass ratio of brown carbon to black carbon (BC) aerosols based on measurements in China and Europe. The comparison of simulated versus observed aerosol light absorption showed that the model accounting for brown carbon aerosol resulted in a better agreement with the observations in East Asian-Pacific outflow. We then used the model results to compute the radiative forcing of brown carbon, which amounts up to -2.4 W m -2 and 0.24 W m -2 at the surface and at the top of the atmosphere (TOA), respectively, over East Asia. Mean radiative forcing of brown carbon aerosol is -0.43 W m -2 and 0.05 W m -2 at the surface and at the TOA, accounting for about 15% of total radiative forcing (-2.2 W m -2 and 0.33 W m -2) by absorbing aerosols (BC + brown carbon aerosol), having a significant climatic implication in East Asia.

  17. Accounting for dust aerosol size distribution in radiative transfer

    NASA Astrophysics Data System (ADS)

    Li, Jiangnan; Min, Qilong; Peng, Yiran; Sun, Zhian; Zhao, Jian-Qi

    2015-07-01

    The impact of size distribution of mineral dust aerosol on radiative transfer was investigated using the Aerosol Robotic Network-retrieved aerosol size distributions. Three methods for determining the aerosol optical properties using size distributions were discussed. The first is referred to as a bin method in which the aerosol optical properties are determined for each bin of the size distribution. The second is named as an assembly mean method in which the aerosol optical properties are determined with an integration of the aerosol optical parameters over the observed size distribution. The third is a normal parameterization method based on an assumed size distribution. The bin method was used to generate the benchmark results in the radiation calculations against the methods of the assembly mean, and parameterizations based on two size distribution functions, namely, lognormal and gamma were examined. It is seen that the assembly mean method can produce aerosol radiative forcing with accuracy of better than 1%. The accuracies of the parameterizations based on lognormal and gamma size distributions are about 25% and 5%, respectively. Both the lognormal and gamma size distributions can be determined by two parameters, the effective radius and effective variance. The better results from the gamma size distribution can be explained by a third parameter of skewness which is found to be useful for judging how close the assumed distribution is to the observation result. The parameterizations based on the two assumed size distributions are also evaluated in a climate model. The results show that the reflected solar fluxes over the desert areas determined by the scheme based on the gamma size distribution are about 1 W m-2 less than those from the scheme based on the lognormal size distribution, bringing the model results closer to the observations.

  18. Radiative properties of the background aerosol: absorption component of extinction.

    PubMed

    Clarke, A D; Charlson, R J

    1985-07-19

    The light-scattering and light-absorption coefficients of the global background aerosol define its single-scatter albedo. Continuous, simultaneous measurements of these optical coefficients were made on a daily basis for the remote marine mid-troposphere; such measurements are essential for assessment of the effects of aerosol on atmospheric radiative transfer. Measurements of light-absorption coefficients made at the Mauna Loa Observatory in Hawaii were higher than expected, and the single-scatter albedo was lower than the value often used in radiative transfer models. Soot appears to be the most likely primary absorber, and hemispheric dispersal of this combustion-derived material is suggested. PMID:17759145

  19. Climatology of aerosol properties and clear-sky shortwave radiative effects using Lidar and Sun photometer observations in the Dakar site

    NASA Astrophysics Data System (ADS)

    Mortier, A.; Goloub, P.; Derimian, Y.; Tanré, D.; Podvin, T.; Blarel, L.; Deroo, C.; Marticorena, B.; Diallo, A.; Ndiaye, T.

    2016-06-01

    This paper presents the analysis of nearly a decade of continuous aerosol observations performed at the Mbour site (Senegal) with Sun photometer, Lidar, and Tapered Electromagnetic Oscillating Microbalance. This site is influenced all year-round by desert dust and sporadically, in wintertime, by biomass burning particles. Different patterns are revealed for winter and summer, seasons associated to air masses of different origin. The summer (wet season) is characterized by a high aerosol loading (optical thickness, AOT, around 0.57 at 532 nm) composed of large and weakly absorbing particles (Angstrom exponent, α, of 0.23 and single-scattering albedo, ϖ0, of 0.94 at 532 nm). A lower aerosol loading (AOT = 0.32) is observed during winter (dry season) for finer and absorbing particles (α = 0.48 and ϖ0 = 0.87) revealing the presence of biomass burning aerosols and a greater proportion of local emissions. This latter anthropogenic contribution is visible at weekly and daily scales through AOT cycles. A decrease of about 30% in AOT has been featured in autumn since 2003. The derivation of the extinction profiles highlights a dust transport close to the ground during winter and in an aloft layer (up to 5 km) during summer. Accurate calculations of the daily aerosol radiative effect in clear-sky conditions are finally addressed. From spring to winter, seasonal shortwave radiative forcing averages of 14.15, 11.15, 8.92, and 12.06 W m-2 have been found respectively. Up to 38% of the solar clear-sky atmospheric heating can be attributed to the aerosols in this site.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  2. Atmospheric Radiation Measurement (ARM) Data from Shouxian, China for the Study of Aerosol Indirect Effects in China

    DOE Data Explorer

    In a complex ARM Mobile Facility (AMF) deployment, monitoring data was collected at four locations in China during 2008. The various sites are located in regions with different climate regimes and with high aerosol loadings of different optical, physical, and chemical properties. Measurements obtained at all the AMF sites during the 8-month deployment in China will help scientists to validate satellite-based findings, understand the mechanisms of the aerosol indirect effects in the region, and examine the roles of aerosols in affecting regional climate and atmospheric circulation, with a special focus on the impact of the East Asian monsoon system. As with other collections from the ARM Mobile Facility, the datasets are available from the ARM Archive. The ARM Archive physically resides at the Oak Ridge National Laboratory.

  3. Performance of McRAS-AC in the GEOS-5 AGCM: Part 1, Aerosol-Activated Cloud Microphysics, Precipitation, Radiative Effects, and Circulation

    NASA Technical Reports Server (NTRS)

    Sud, Y. C.; Lee, D.; Oreopoulos, L.; Barahona, D.; Nenes, A.; Suarez, M. J.

    2012-01-01

    A revised version of the Microphysics of clouds with Relaxed Arakawa-Schubert and Aerosol-Cloud interaction (McRAS-AC), including, among others, the Barahona and Nenes ice nucleation parameterization, is implemented in the GEOS-5 AGCM. Various fields from a 10-year long integration of the AGCM with McRAS-AC were compared with their counterparts from an integration of the baseline GEOS-5 AGCM, and with satellite data as observations. Generally using McRAS-AC reduced biases in cloud fields and cloud radiative effects are much better over most of the regions of the Earth. Two weaknesses are identified in the McRAS-AC runs, namely, too few cloud particles around 40S-60S, and too high cloud water path during northern hemisphere summer over the Gulf Stream and North Pacific. Sensitivity analyses showed that these biases potentially originated from biases in the aerosol input. The first bias is largely eliminated in a sensitivity test using 50% smaller aerosol particles, while the second bias is much reduced when interactive aerosol chemistry was turned on. The main drawback of McRAS-AC is dearth of low-level marine stratus clouds, probably due to lack of dry-convection, not yet implemented into the cloud scheme. Despite these biases, McRAS-AC does simulate realistic clouds and their optical properties that can improve with better aerosol-input and thereby has the potential to be a valuable tool for climate modeling research because of its aerosol indirect effect simulation capabilities involving prediction of cloud particle number concentration and effective particle size for both convective and stratiform clouds is quite realistic.

  4. Global aerosol effects on convective clouds

    NASA Astrophysics Data System (ADS)

    Wagner, Till; Stier, Philip

    2013-04-01

    Atmospheric aerosols affect cloud properties, and thereby the radiation balance of the planet and the water cycle. The influence of aerosols on clouds is dominated by increase of cloud droplet and ice crystal numbers (CDNC/ICNC) due to enhanced aerosols acting as cloud condensation and ice nuclei. In deep convective clouds this increase in CDNC/ICNC is hypothesised to increase precipitation because of cloud invigoration through enhanced freezing and associated increased latent heat release caused by delayed warm rain formation. Satellite studies robustly show an increase of cloud top height (CTH) and precipitation with increasing aerosol optical depth (AOD, as proxy for aerosol amount). To represent aerosol effects and study their influence on convective clouds in the global climate aerosol model ECHAM-HAM, we substitute the standard convection parameterisation, which uses one mean convective cloud for each grid column, with the convective cloud field model (CCFM), which simulates a spectrum of convective clouds, each with distinct values of radius, mixing ratios, vertical velocity, height and en/detrainment. Aerosol activation and droplet nucleation in convective updrafts at cloud base is the primary driver for microphysical aerosol effects. To produce realistic estimates for vertical velocity at cloud base we use an entraining dry parcel sub cloud model which is triggered by perturbations of sensible and latent heat at the surface. Aerosol activation at cloud base is modelled with a mechanistic, Köhler theory based, scheme, which couples the aerosols to the convective microphysics. Comparison of relationships between CTH and AOD, and precipitation and AOD produced by this novel model and satellite based estimates show general agreement. Through model experiments and analysis of the model cloud processes we are able to investigate the main drivers for the relationship between CTH / precipitation and AOD.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Are remote-sensing retrieved aerosol radiative properties a suitable proxy for cloud condensation nuclei?

    NASA Astrophysics Data System (ADS)

    Stier, Philip

    2014-05-01

    Aerosol-cloud interactions arguably remain the single greatest uncertainty among anthropogenic perturbations of the climate system. The large uncertainties associated with their representation in global aerosol climate models have emphasised the need for observational studies. In-situ measurements provide a detailed description of aerosol and cloud microphysical properties, providing strong observational constraints on aerosol cloud interactions. However, their spatio-temporal sampling is sparse so that "observational" estimates of global aerosol cloud interactions generally rely on co-located satellite retrievals of aerosol radiative properties and cloud properties. In this study I will critically evaluate the suitability of remote-sensing retrieved aerosol radiative properties, such as aerosol optical depth (AOD), aerosol index (AI) and aerosol fine mode optical depth, as proxy for cloud condensation nuclei (CCN). This analysis based on the fully self-consistent calculation of aerosol radiative properties and CCN in the aerosol climate model ECHAM-HAM. Correlating simulated aerosol radiative properties with CCN at a range of supersaturations (sampling different sizes/composition of the aerosol spectrum) highlights limitations in the suitability of AOD and AI as proxy for CCN. These discrepancies arise from a range of factors, including the limited representativeness of column-integrated aerosol radiative properties for surface or cloud-base CCN as well as the effects of humidity growth of aerosols, affecting AOD/AI but not CCN. Simulated correlations show a strong regional variability, with significant implications for "observational" estimates of aerosol cloud interactions from remote-sensing as well as in-situ data.

  7. Evaluating aerosol indirect effect through marine stratocumulus clouds

    SciTech Connect

    Kogan, Z.N.; Kogan, Y.L.; Lilly, D.K.

    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.

  8. Aerosol delivery of beclin1 enhanced the anti-tumor effect of radiation in the lungs of K-rasLA1 mice.

    PubMed

    Shin, Ji-Young; Lim, Hwang-Tae; Minai-Tehrani, Arash; Noh, Mi-Suk; Kim, Ji-Eun; Kim, Ji-Hye; Jiang, Hu-Lin; Arote, Rohidas; Kim, Doo-Yeol; Chae, Chanhee; Lee, Kee-Ho; Kim, Mi-Sook; Cho, Myung-Haing

    2012-07-01

    Radiotherapy alone has several limitations for treating lung cancer. Inhalation, a non-invasive approach for direct delivery of therapeutic agents to the lung, may help to enhance the therapeutic efficacy of radiation. Up-regulating beclin1, known as a tumor suppressor gene that plays a major role in autophagy, may sensitize tumors and lead to tumor regression in lungs of K-ras(LA1) lung cancer model mice. To minimize the side-effects of radiotherapy, fractionated exposures (five times, 24-h interval) with low dose (2 Gy) of radiation to the restricted area (thorax, 2 cm) were conducted. After sensitizing the lungs with radiation, beclin1, complexed with a nano-sized biodegradable poly(ester amine), was prepared and delivered into the murine lung via aerosol three times/week for four weeks. In a histopathological analysis, animals treated with beclin1 and radiation showed highly significant tumor regression and low progression to adenocarcinoma. An increase in the number of autophagic vacuoles and secondary lysosomes was detected. Dissociation of beclin1-bcl2 stimulated autophagy activation and showed a synergistic anti-tumor effect by inhibiting the Akt-mTOR pathway, cell proliferation and angiogenesis. The combination of radiation with non-invasive aerosol delivery of beclin1 may provide a prospect for developing novel therapy regimens applicable in clinics. PMID:22843615

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  10. Direct Radiative Effects of Particulate Aerosols Emitted by the Space Transport Sector

    NASA Astrophysics Data System (ADS)

    Ross, M.; Zittel, P.; Toohey, D. W.; Mills, M. J.

    2010-12-01

    Rockets are the sole source of human produced nonvolatile particulate directly injected into the atmosphere above 20 km altitude. The main components of rocket particulate are submicron black carbon soot (BC) from hydrocarbon (HC) fueled engines and Al2O3 (alumina) from solid rocket motors. Since the emission index and atmospheric lifetime of BC emitted by rockets are each several orders of magnitude greater than those of aircraft, the direct shortwave (SW) radiative forcing (RF) of rocket BC could be comparable to aircraft, even though the amount of HC fuel burned in the stratosphere by rockets is small compared to aircraft. The net RF of alumina particulate, on the other hand, is more uncertain. Alumina possesses large SW scattering and large longwave (LW) absorption so that the net RF for alumina is a strong function of particle size. For submicron alumina particles that constitute the steady state stratospheric population from solid rockets, the SW scattering and LW absorption efficiencies are comparable and the net RF depends on the assumed properties of the steady state population. We present calculations of the SW and LW optical properties of BC and alumina emitted by rocket engines and estimates of the global direct RF under various assumptions of engine type combinations and growth in the space transport sector. We compare these results to the RF associated with other transport sectors and the direct RF from the CO2 emissions from the space transport sector.

  11. Vertical transport of ozone in the upper and lower troposphere during INDOEX: Radiative effects of aerosols and dynamic processes

    NASA Astrophysics Data System (ADS)

    Burkert, J.; Andres-Hernandez, M. D.; Dickerson, R. R.; Smit, H.; Wittrock, F.; Richter, A.; Burrows, J. P.

    2003-04-01

    The variations of different meteorological parameters and trace gas mixing ratios (rel. Hum., Temp., O3) in the lower troposphere over the Indian Ocean have been analysed. The measurements were performed in February-April 1999 during a ship cruise as a part of the Indian Ocean Experiment (INDOEX). During the campaign air parcels from the surrounding areas of the Bay of Bengal were encountered corresponding with a clearly structured vertical distribution of O3 in the lower troposphere (20 ppbv O3 at sea level, 80 ppbv O3 between 2 and 3 km). The remarkable vertical O3 structure vanished due to the moist convection associated to a 24 hours rain event and re-established directly afterwards. The responsible processes for the strong stability of the lower troposphere will be discussed, with special regards to the absorption of solar radiation by aerosols. Therefore, a radiative transfer model (SCIATRAN) has been used to calculate warming rates caused by the absorption of aerosols. Furthermore, the role of macro- and meso-scale processes on the vertical and horizontal distribution of O3 has been qualitatively investigated by using back trajectories, O3 soundings, and tropospheric columns of O3, NO2, and HCHO derived from satellite based measurements. Possible sources of O3 above the southern hemispheric Indian Ocean will be discussed. In addition, some questions concerning the stability of the atmosphere over the ocean will be raised.

  12. From Regional Cloud-Albedo to a Global Albedo Footprint - Studying Aerosol Effects on the Radiation Budget Using the Relation Between Albedo and Cloud Fraction

    NASA Astrophysics Data System (ADS)

    Bender, F.; Engström, A.; Karlsson, J.; Wood, R.; Charlson, R. J.

    2015-12-01

    Earth's albedo is the primary determinant of the amount of energy absorbed by the Earth-atmosphere system. The main factor controlling albedo is the amount of clouds present, but aerosols can affect and alter both clear-sky and cloudy-sky reflectance. How albedo depends on cloud fraction and how albedo varies at a given cloud fraction and a given cloud water content, reveals information about these aerosol effects on the radiation budget. Hence, the relation between total albedo and cloud fraction can be used for illustration and quantification of aerosol effects, and as a diagnostic tool, to test model performance. Here, we show examples of the utilisation of this relation focusing on satellite observations from CERES and MODIS on Aqua, as well as from Calipso and CloudSat, and performing comparisons with climate models on the way: In low-cloud regions in the subtropics, we find that climate models well represent a near-constant regional cloud albedo, and this representation has improved from CMIP3 to CMIP5. CMIP5 models indicate more reflective clouds in present-day climate than pre-industrial, as a result of increased aerosol burdens. On monthly mean time scale, models are found to over-estimate the regional cloud-brightening due to aerosols. On the global scale we find an increasing cloud albedo with increasing cloud fraction - a relation that is very well defined in observations, and less so in CMIP5 models. Cloud brightening from pre-industrial to present day is also seen on global scale. Further, controlling for both cloud fraction and cloud water content we can trace small variations in albedo, or perturbations of solar reflectivity, that create a near-global coherent geographical pattern that is consistent with aerosol impacts on climate, with albedo enhancement in regions dominant of known aerosol sources and suppression of albedo in regions associated with high rates of aerosol removal (deduced using CloudSat precipitation estimates). This mapping can be

  13. Impacts of ENSO events on cloud radiative effects in preindustrial conditions: Changes in cloud fraction and aerosol emissions, wet scavenging and transport

    NASA Astrophysics Data System (ADS)

    Yang, Y.; Russell, L. M.; Xu, L.; Lou, S.; Lamjiri, M. A.

    2015-12-01

    The impacts of the El Niño-Southern Oscillation (ENSO) events on shortwave and longwave cloud radiative effects (CRESW and CRELW) and the related changes in cloud fraction and aerosol emissions, wet scavenging and transport are quantified using three 150-year simulations for the preindustrial condition from the CESM model. Compared to recent observations from Clouds and the Earth's Radiant Energy System (CERES), the model simulation successfully reproduced larger variations of CRESW over the tropical western and central Pacific, Indonesian regions, and the eastern Pacific, as well as large variations of CRELW located mainly within the tropics. The ENSO cycle is found to dominate interannual variations of cloud radiative effects, especially over the tropics. Relative to those during La Niña events, simulated cooling (warming) effects from CRESW (CRELW) during El Niño events are stronger over tropical western and central Pacific, with the largest difference exceeding 40 Wm-2 (30 Wm-2), and weaker effects of 10-30 Wm-2 over Indonesian regions and the subtropical Pacific. Sensitivity tests show that variations of cloud radiative effects are mainly driven by ENSO-induced changes in cloud fraction. However, changes in natural aerosol concentrations, primarily due to changes in wet scavenging and transport processes, also play an important role in modulating the variations of cloud radiative effects. Because of increased (decreased) precipitation in El Niño (La Niña) events, increased (decreased) wet scavenging and transport of natural aerosols offset about 10% of variations of cloud radiative effects averaged over the tropics, whereas the emission changes enhance the variations by 4-6%. Moreover, the variation in medium and high cloud fraction accounts for about 20-50% of the interannual variations of CRESW over the tropics and almost all of the variations of CRELW between 60°S and 60°N. The variation of low cloud fraction plays a dominant role in contributing

  14. Shortwave direct radiative effects of above-cloud aerosols over global oceans derived from 8 years of CALIOP and MODIS observations

    NASA Astrophysics Data System (ADS)

    Zhang, Zhibo; Meyer, Kerry; Yu, Hongbin; Platnick, Steven; Colarco, Peter; Liu, Zhaoyan; Oreopoulos, Lazaros

    2016-03-01

    In this paper, we studied the frequency of occurrence and shortwave direct radiative effects (DREs) of above-cloud aerosols (ACAs) over global oceans using 8 years (2007-2014) of collocated CALIOP and MODIS observations. Similar to previous work, we found high ACA occurrence in four regions: southeastern (SE) Atlantic region, where ACAs are mostly light-absorbing aerosols, i.e., smoke and polluted dust according to CALIOP classification, originating from biomass burning over the African Savanna; tropical northeastern (TNE) Atlantic and the Arabian Sea, where ACAs are predominantly windblown dust from the Sahara and Arabian deserts, respectively; and the northwestern (NW) Pacific, where ACAs are mostly transported smoke and polluted dusts from Asian. From radiative transfer simulations based on CALIOP-MODIS observations and a set of the preselected aerosol optical models, we found the DREs of ACAs at the top of atmosphere (TOA) to be positive (i.e., warming) in the SE Atlantic and NW Pacific regions, but negative (i.e., cooling) in the TNE Atlantic Ocean and the Arabian Sea. The cancellation of positive and negative regional DREs results in a global ocean annual mean diurnally averaged cloudy-sky DRE of 0.015 W m-2 (range of -0.03 to 0.06 W m-2) at TOA. The DREs at surface and within the atmosphere are -0.15 W m-2 (range of -0.09 to -0.21 W m-2), and 0.17 W m-2 (range of 0.11 to 0.24 W m-2), respectively. The regional and seasonal mean DREs are much stronger. For example, in the SE Atlantic region, the JJA (July-August) seasonal mean cloudy-sky DRE is about 0.7 W m-2 (range of 0.2 to 1.2 W m-2) at TOA. All our DRE computations are publicly available1. The uncertainty in our DRE computations is mainly caused by the uncertainties in the aerosol optical properties, in particular aerosol absorption, the uncertainties in the CALIOP operational aerosol optical thickness retrieval, and the ignorance of cloud and potential aerosol diurnal cycle. In situ and remotely sensed

  15. Impact of gas-to-particle partitioning approaches on the simulated radiative effects of biogenic secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Scott, C. E.; Spracklen, D. V.; Pierce, J. R.; Riipinen, I.; D'Andrea, S. D.; Rap, A.; Carslaw, K. S.; Forster, P. M.; Kulmala, M.; Mann, G. W.; Pringle, K. J.

    2015-02-01

    The oxidation of biogenic volatile organic compounds (BVOCs) gives a range of products, from semi-volatile to extremely low-volatility compounds. To treat the interaction of these secondary organic vapours with the particle phase, global aerosol microphysics models generally use either a thermodynamic partitioning approach (assuming instant equilibrium between semi-volatile oxidation products and the particle phase) or a kinetic approach (accounting for the size-dependence of condensation). We show that model treatment of the partitioning of biogenic organic vapours into the particle phase, and consequent distribution of material across the size distribution, controls the magnitude of the first aerosol indirect effect (AIE) due to biogenic secondary organic aerosol (SOA). With a kinetic partitioning approach, SOA is distributed according to the existing condensation sink, enhancing the growth of the smallest particles, i.e., those in the nucleation mode. This process tends to increase cloud droplet number concentrations in the presence of biogenic SOA. By contrast, a thermodynamic approach distributes SOA according to pre-existing organic mass, restricting the growth of the smallest particles, limiting the number that are able to form cloud droplets. With an organically medicated new particle formation mechanism, applying a thermodynamic rather than a kinetic approach reduces our calculated global mean AIE due to biogenic SOA by 24%. Our results suggest that the mechanisms driving organic partitioning need to be fully understood in order to accurately describe the climatic effects of SOA.

  16. Impact of gas-to-particle partitioning approaches on the simulated radiative effects of biogenic secondary organic aerosol

    NASA Astrophysics Data System (ADS)

    Scott, C. E.; Spracklen, D. V.; Pierce, J. R.; Riipinen, I.; D'Andrea, S. D.; Rap, A.; Carslaw, K. S.; Forster, P. M.; Artaxo, P.; Kulmala, M.; Rizzo, L. V.; Swietlicki, E.; Mann, G. W.; Pringle, K. J.

    2015-11-01

    The oxidation of biogenic volatile organic compounds (BVOCs) gives a range of products, from semi-volatile to extremely low-volatility compounds. To treat the interaction of these secondary organic vapours with the particle phase, global aerosol microphysics models generally use either a thermodynamic partitioning approach (assuming instant equilibrium between semi-volatile oxidation products and the particle phase) or a kinetic approach (accounting for the size dependence of condensation). We show that model treatment of the partitioning of biogenic organic vapours into the particle phase, and consequent distribution of material across the size distribution, controls the magnitude of the first aerosol indirect effect (AIE) due to biogenic secondary organic aerosol (SOA). With a kinetic partitioning approach, SOA is distributed according to the existing condensation sink, enhancing the growth of the smallest particles, i.e. those in the nucleation mode. This process tends to increase cloud droplet number concentrations in the presence of biogenic SOA. By contrast, an approach that distributes SOA according to pre-existing organic mass restricts the growth of the smallest particles, limiting the number that are able to form cloud droplets. With an organically mediated new particle formation mechanism, applying a mass-based rather than a kinetic approach to partitioning reduces our calculated global mean AIE due to biogenic SOA by 24 %. Our results suggest that the mechanisms driving organic partitioning need to be fully understood in order to accurately describe the climatic effects of SOA.

  17. Model Intercomparison of Indirect Aerosol Effects

    NASA Technical Reports Server (NTRS)

    Penner, J. E.; Quaas, J.; Storelvmo, T.; Takemura, T.; Boucher, O.; Guo, H.; Kirkevag, A.; Kristjansson, J. E.; Seland, O.

    2006-01-01

    Modeled differences in predicted effects are increasingly used to help quantify the uncertainty of these effects. Here, we examine modeled differences in the aerosol indirect effect in a series of experiments that help to quantify how and why model-predicted aerosol indirect forcing varies between models. The experiments start with an experiment in which aerosol concentrations, the parameterization of droplet concentrations and the autoconversion scheme are all specified and end with an experiment that examines the predicted aerosol indirect forcing when only aerosol sources are specified. Although there are large differences in the predicted liquid water path among the models, the predicted aerosol first indirect effect for the first experiment is rather similar, about -0.6 W/sq m to -0.7 W/sq m. Changes to the autoconversion scheme can lead to large changes in the liquid water path of the models and to the response of the liquid water path to changes in aerosols. Adding an autoconversion scheme that depends on the droplet concentration caused a larger (negative) change in net outgoing shortwave radiation compared to the 1st indirect effect, and the increase varied from only 22% to more than a factor of three. The change in net shortwave forcing in the models due to varying the autoconversion scheme depends on the liquid water content of the clouds as well as their predicted droplet concentrations, and both increases and decreases in the net shortwave forcing can occur when autoconversion schemes are changed. The parameterization of cloud fraction within models is not sensitive to the aerosol concentration, and, therefore, the response of the modeled cloud fraction within the present models appears to be smaller than that which would be associated with model "noise". The prediction of aerosol concentrations, given a fixed set of sources, leads to some of the largest differences in the predicted aerosol indirect radiative forcing among the models, with values of

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

    NASA Astrophysics Data System (ADS)

    Samset, B. H.; Myhre, G.

    2012-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  20. Investigation of multiple scattering effects in aerosols

    NASA Technical Reports Server (NTRS)

    Deepak, A.

    1980-01-01

    The results are presented of investigations on the various aspects of multiple scattering effects on visible and infrared laser beams transversing dense fog oil aerosols contained in a chamber (4' x 4' x 9'). The report briefly describes: (1) the experimental details and measurements; (2) analytical representation of the aerosol size distribution data by two analytical models (the regularized power law distribution and the inverse modified gamma distribution); (3) retrieval of aerosol size distributions from multispectral optical depth measurements by two methods (the two and three parameter fast table search methods and the nonlinear least squares method); (4) modeling of the effects of aerosol microphysical (coagulation and evaporation) and dynamical processes (gravitational settling) on the temporal behavior of aerosol size distribution, and hence on the extinction of four laser beams with wavelengths 0.44, 0.6328, 1.15, and 3.39 micrometers; and (5) the exact and approximate formulations for four methods for computing the effects of multiple scattering on the transmittance of laser beams in dense aerosols, all of which are based on the solution of the radiative transfer equation under the small angle approximation.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  2. Observationally constrained estimates of carbonaceous aerosol radiative forcing.

    PubMed

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

    2012-07-17

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

  3. Impacts of ENSO events on cloud radiative effects in preindustrial conditions: Changes in cloud fraction and their dependence on interactive aerosol emissions and concentrations

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Russell, Lynn M.; Xu, Li; Lou, Sijia; Lamjiri, Maryam A.; Somerville, Richard C. J.; Miller, Arthur J.; Cayan, Daniel R.; DeFlorio, Michael J.; Ghan, Steven J.; Liu, Ying; Singh, Balwinder; Wang, Hailong; Yoon, Jin-Ho; Rasch, Philip J.

    2016-06-01

    We use three 150 year preindustrial simulations of the Community Earth System Model to quantify the impacts of El Niño-Southern Oscillation (ENSO) events on shortwave and longwave cloud radiative effects (CRESW and CRELW). Compared to recent observations from the Clouds and the Earth's Radiant Energy System data set, the model simulation successfully reproduces larger variations of CRESW and CRELW over the tropics. The ENSO cycle is found to dominate interannual variations of cloud radiative effects. Simulated cooling (warming) effects from CRESW (CRELW) are strongest over the tropical western and central Pacific Ocean during warm ENSO events, with the largest difference between 20 and 60 W m-2, with weaker effects of 10-40 W m-2 over Indonesian regions and the subtropical Pacific Ocean. Sensitivity tests show that variations of cloud radiative effects are mainly driven by ENSO-related changes in cloud fraction. The variations in midlevel and high cloud fractions each account for approximately 20-50% of the interannual variations of CRESW over the tropics and almost all of the variations of CRELW between 60°S and 60°N. The variation of low cloud fraction contributes to most of the variations of CRESW over the midlatitude oceans. Variations in natural aerosol concentrations explained 10-30% of the variations of both CRESW and CRELW over the tropical Pacific, Indonesian regions, and the tropical Indian Ocean. Changes in natural aerosol emissions and concentrations enhance 3-5% and 1-3% of the variations of cloud radiative effects averaged over the tropics.

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

    SciTech Connect

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

    2005-02-01

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

  5. Impacts of 3-D radiative effects on satellite cloud detection and their consequences on cloud fraction and aerosol optical depth retrievals

    NASA Astrophysics Data System (ADS)

    Yang, Yuekui; di Girolamo, Larry

    2008-02-01

    We present the first examination on how 3-D radiative transfer impacts satellite cloud detection that uses a single visible channel threshold. The 3-D radiative transfer through predefined heterogeneous cloud fields embedded in a range of horizontally homogeneous aerosol fields have been carried out to generate synthetic nadir-viewing satellite images at a wavelength of 0.67 μm. The finest spatial resolution of the cloud field is 30 m. We show that 3-D radiative effects cause significant histogram overlap between the radiance distribution of clear and cloudy pixels, the degree to which depends on many factors (resolution, solar zenith angle, surface reflectance, aerosol optical depth (AOD), cloud top variability, etc.). This overlap precludes the existence of a threshold that can correctly separate all clear pixels from cloudy pixels. The region of clear/cloud radiance overlap includes moderately large (up to 5 in our simulations) cloud optical depths. Purpose-driven cloud masks, defined by different thresholds, are applied to the simulated images to examine their impact on retrieving cloud fraction and AOD. Large (up to 100s of %) systematic errors were observed that depended on the type of cloud mask and the factors that influence the clear/cloud radiance overlap, with a strong dependence on solar zenith angle. Different strategies in computing domain-averaged AOD were performed showing that the domain-averaged BRF from all clear pixels produced the smallest AOD biases with the weakest (but still large) dependence on solar zenith angle. The large dependence of the bias on solar zenith angle has serious implications for climate research that uses satellite cloud and aerosol products.

  6. Spatially Refined Aerosol Direct Radiative Forcing Efficiencies

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  7. Influence of urban aerosol pollution to radiative forcing

    NASA Astrophysics Data System (ADS)

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

    2007-10-01

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

  8. Aerosol direct radiative forcing at the top of atmosphere based on satellite remote sensing over China Seas: a preliminary study

    NASA Astrophysics Data System (ADS)

    Hao, Zengzhou; Pan, Delu; Gong, Fang

    2010-09-01

    Radiative forcing as an index of climate change can reflect the relative effect of climate factors. To understand climatic implications of aerosols over the China Seas, the aerosol direct radiative forcing at the top of atmosphere (TOA) is computed using three-year collocated Clouds and the Earth's Radiant Energy System (CERES) radiation fluxes and Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical thickness data on the platform Terra. The upward radiation flux for clear skies is a key for the aerosol radiative forcing at the TOA. A linear relationship is found between the solar radiation fluxes at the TOA from CERES and the aerosol optical thickness is at 550 nm from MODIS over the China Seas. In a linear regression Eq., the intercept for zero aerosol optical thickness is the radiation flux at the TOA for clear skies. Based on the definition of the aerosol direct radiative forcing at TOA and the diurnal correction factor from a simulated radiative forcing using radiation transfer model, the daily averaged aerosol direct radiative forcing at the TOA is estimated and its seasonal variations over the cloud-free China Seas are presented. In total, the aerosol radiative forcing over the China Seas is negative. It implies that the aerosol over the China Seas is mainly a cooling effect on climate change, which is opposite to the greenhouse effect. The largest aerosol radiative forcing is found in spring, while the smallest is in summer. The aerosol radiative forcing over the coastal region is always more than that in the open ocean in four seasons. The method in the study can be used for evaluation of the aerosols impact on global or region climate from satellite measurements.

  9. Aerosol Absorption Effects in the TOMS UV Algorithm

    NASA Technical Reports Server (NTRS)

    Torres, O.; Krotkov, N.; Bhartia, P. K.

    2004-01-01

    The availability of global long-term estimates of surface UV radiation is very important, not only for preventive medicine considerations, but also as an important tool to monitor the effects of the stratospheric ozone recovery expected to occur in the next few decades as a result of the decline of the stratospheric chlorine levels. In addition to the modulating effects of ozone and clouds, aerosols also affect the levels of UV-A and W-B radiation reaching the surface. Oscillations in surface W associated with the effects of aerosol absorption may be comparable in magnitude to variations associated with the stratospheric ozone recovery. Thus, the accurate calculation of surface W radiation requires that both the scattering and absorption effects of tropospheric aerosols be taken into account. Although absorption effects of dust and elevated carbonaceous aerosols are already accounted for using Aerosol Index technique, this approach does not work for urban/industrial aerosols in the planetary boundary layer. The use of the new TOMS long-term global data record on UV aerosol absorption optical depth, can improve the accuracy of TOMS spectral UV products, by properly including the spectral attenuation effects of carbonaceous, urban/industrial and mineral aerosols. The TOMS data set on aerosol properties will be discussed, and results of its use in the TOMS surface W algorithm will be presented.

  10. Different aerosol loading and their radiative implication over Indo-Gangetic Basin

    NASA Astrophysics Data System (ADS)

    Tiwari, Shani; Singh, Abhay Kumar; Srivastava, Atul Kumar

    Abstract: The climate and environmental effects of atmospheric aerosols are presently the most critical issues in global science community because of their various emission sources and different impacts to earth’s radiation budget. Different types of atmospheric aerosols have different optical as well as radiative properties which are crucial to reduce possible uncertainties in climate forcing. Indo-Gangetic Basin (IGB)in northern part of India has been recognized for different types of aerosol loading due to various emission sources (natural and anthropogenic) of aerosols and unique topography of the region. In the present study, we have identified different aerosol types using Aerosol Robotic NETwork (AERONET) level 2 aerosol products during 2010-2011 at four different locations in the Indo-Gangetic Basin (IGB) viz. Karachi (24.870N, 67.03 E), Lahore (31.540 N, 74.320 E), Jaipur (26.900 N, 75.900E), and Kanpur (26.4◦ N, 80.4◦ E). Five different aerosol types were identified using fine-mode fraction, (FMF) and single scattering albedo (SSA) at the stations over IGB viz. PD (polluted dust), PC (polluted continental), MBC (mostly black carbon), MOC (mostly organic carbon) and NA (non-absorbing). Very interesting results are observed which are discussed in terms of different aerosol types associated with their different optical as well as radiative properties. Keywords: aerosol types, radiative properties, IGB.

  11. GCM Simulations of the Aerosol Indirect Effect: Sensitivity to Cloud Parameterization and Aerosol Burden

    NASA Technical Reports Server (NTRS)

    Menon, Surabi; DelGenio, Anthony D.; Koch, Dorothy; Tselioudis, George; Hansen, James E. (Technical Monitor)

    2001-01-01

    We describe the coupling of the Goddard Institute for Space Studies (GISS) general circulation model (GCM) to an online sulfur chemistry model and source models for organic matter and sea-salt that is used to estimate the aerosol indirect effect. The cloud droplet number concentration is diagnosed empirically from field experiment datasets over land and ocean that observe droplet number and all three aerosol types simultaneously; corrections are made for implied variations in cloud turbulence levels. The resulting cloud droplet number is used to calculate variations in droplet effective radius, which in turn allows us to predict aerosol effects on cloud optical thickness and microphysical process rates. We calculate the aerosol indirect effect by differencing the top-of-the-atmosphere net cloud radiative forcing for simulations with present-day vs. pre-industrial emissions. Both the first (radiative) and second (microphysical) indirect effects are explored. We test the sensitivity of our results to cloud parameterization assumptions that control the vertical distribution of cloud occurrence, the autoconversion rate, and the aerosol scavenging rate, each of which feeds back significantly on the model aerosol burden. The global mean aerosol indirect effect for all three aerosol types ranges from -1.55 to -4.36 W m(exp -2) in our simulations. The results are quite sensitive to the pre-industrial background aerosol burden, with low pre-industrial burdens giving strong indirect effects, and to a lesser extent to the anthropogenic aerosol burden, with large burdens giving somewhat larger indirect effects. Because of this dependence on the background aerosol, model diagnostics such as albedo-particle size correlations and column cloud susceptibility, for which satellite validation products are available, are not good predictors of the resulting indirect effect.

  12. GCM Simulations of the Aerosol Indirect Effect: Sensitivity to Cloud Parameterization and Aerosol Burden

    NASA Technical Reports Server (NTRS)

    Menon, Surabi; DelGenio, Anthony D.; Koch, Dorothy; Tselioudis, George; Hansen, James E. (Technical Monitor)

    2001-01-01

    We describe the coupling of the Goddard Institute for Space Studies (GISS) general circulation model (GCM) to an online sulfur chemistry model and source models for organic matter and sea-salt that is used to estimate the aerosol indirect effect. The cloud droplet number concentration is diagnosed empirically from field experiment datasets over land and ocean that observe droplet number and all three aerosol types simultaneously; corrections are made for implied variations in cloud turbulence levels. The resulting cloud droplet number is used to calculate variations in droplet effective radius, which in turn allows us to predict aerosol effects on cloud optical thickness and microphysical process rates. We calculate the aerosol indirect effect by differencing the top-of-the-atmosphere net cloud radiative forcing for simulations with present-day vs. pre-industrial emissions. Both the first (radiative) and second (microphysical) indirect effects are explored. We test the sensitivity of our results to cloud parameterization assumptions that control the vertical distribution of cloud occurrence, the autoconversion rate, and the aerosol scavenging rate, each of which feeds back significantly on the model aerosol burden. The global mean aerosol indirect effect for all three aerosol types ranges from -1.55 to -4.36 W/sq m in our simulations. The results are quite sensitive to the pre-industrial background aerosol burden, with low pre-industrial burdens giving strong indirect effects, and to a lesser extent to the anthropogenic aerosol burden, with large burdens giving somewhat larger indirect effects. Because of this dependence on the background aerosol, model diagnostics such as albedo-particle size correlations and column cloud susceptibility, for which satellite validation products are available, are not good predictors of the resulting indirect effect.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  14. Sulfate aerosol nucleation, primary emissions, and cloud radiative forcing in the aerosol- climate model ECHAM5-HAM

    NASA Astrophysics Data System (ADS)

    Kazil, J.; Quaas, J.; Kinne, S.; Rast, S.; Stier, P.; Feichter, J.

    2008-12-01

    Aerosol nucleation from the gas phase is a major source of aerosol particles in the Earth's atmosphere, contributing to the number of cloud condensation nuclei and consequently of cloud droplets. Nucleation can therefore act upon cloud radiative properties, cloud lifetimes, and precipitation rates via the first and second indirect aerosol effect. However, freshly nucleated particles measure a few nanometers in diameter, and need to grow to sizes of tens of nanometers in order to participate in atmospherically relevant processes. Depending on the availability of condensable molecules, this process may proceed on time scales between minutes to days. Concurrently, the aerosol particles that formed from the gas phase compete with aerosol particles emitted from the surface for condensable material. Therefore, cloud radiative properties, cloud lifetimes, and precipitation rates will depend to various degrees on aerosol nucleation rates and on the individual nucleation pathways. We have implemented a scheme describing the formation of new particles from the gas phase based on laboratory thermochemical data for neutral and charged nucleation of sulfuric acid and water into the aerosol-climate model ECHAM5-HAM. Here we discuss the role of new particle formation from the gas phase for cloud radiative properties and the contributions of the considered nucleation pathways as well as of particulate sulfate emissions. Our simulations show that sulfate aerosol nucleation plays an important role for cloud radiative forcing, in particular over the oceans and in the southern hemisphere. A comparison of the simulated cloud radiative forcing with satellite observations shows the best agreement when both neutral and charged nucleation proceed, with neutral nucleation playing a minor role in the current model version. In contrast, switching off nucleation leads to a systematic bias of the results away from the observations, indicating an important role of aerosol nucleation in the

  15. On the use of a satellite remote-sensing-based approach for determining aerosol direct radiative effect over land: a case study over China

    NASA Astrophysics Data System (ADS)

    Sundström, A.-M.; Arola, A.; Kolmonen, P.; Xue, Y.; de Leeuw, G.; Kulmala, M.

    2015-01-01

    A satellite-based approach to derive the aerosol direct shortwave (SW) radiative effect (ADRE) was studied in an environment with highly variable aerosol conditions over eastern China from March to October 2009. The method is based on using coincident SW top-of-the-atmosphere (TOA) fluxes from the Clouds and the Earth's Radiant Energy System (CERES) and aerosol optical depths (AODs) from the MODerate Resolution Imaging Spectroradiometer (MODIS) to derive SW clear-sky ADRE. The estimate for the aerosol-free TOA flux (F0,TOA) is obtained by establishing linear regression between CERES SW TOA fluxes and MODIS AODs. A normalization procedure to a fixed solar zenith angle, Earth-Sun distance and atmospheric water vapor content was applied to the CERES fluxes prior to the linear fit against AOD to reduce the flux variation not related to aerosols. In the majority of the cases, the normalization increased positive correlation between observed SW TOA fluxes and AODs, and it decreased RMSE. The key question in the satellite-based approach is the accuracy of the estimated F0,TOA. Comparison with simulated F0,TOA showed that both the satellite method and the model produced qualitatively similar spatial patterns, but absolute values differed. In 58 % of the cases the satellite-based F0,TOA was within ±10 W m-2 of the modeled value (about 7-8 % difference in flux values). Over bright surfaces, the satellite-based method tend to produce lower F0,TOA than the model. The satellite-based clear-sky estimates for median instantaneous and diurnally averaged ADRE over the study area were -8.8 W m-2 and -5.1 W m-2, respectively. Over heavily industrialized areas, the cooling at TOA was 2 to more than 3 times the median value, and associated with high AODs (> 0.5). Especially during the summer months, positive ADREs were observed locally over dark surfaces. This was most probably a method artifact related to systematic change of aerosol type, sub-visual cloud contamination or both.

  16. On the use of satellite remote sensing based approach for determining aerosol direct radiative effect over land: a case study over China

    NASA Astrophysics Data System (ADS)

    Sundström, A.-M.; Arola, A.; Kolmonen, P.; Xue, Y.; de Leeuw, G.; Kulmala, M.

    2014-06-01

    A satellite-based approach to derive the aerosol direct short wave (SW) radiative effect (ADRE) was studied in an environment with highly variable aerosol conditions over Eastern China from March to October 2009. The method is based on using coincident SW Top of the Atmosphere (TOA) fluxes from the Clouds and the Earth's Radiant Energy System (CERES) and aerosol optical depths (AODs) from the Moderate Resolution Imaging Sectroradiometer (MODIS). The estimate for instantaneous clear sky ADRE is obtained by establishing linear regression between CERES fluxes and MODIS AODs. Even though the approach has been used in a number of studies, less focus has been paid to the method itself. In this study the main goals were first to study the method in more detail as well as it's applicability over Eastern China, and second to derive a satellite-based estimate of ADRE over the study area. Before the linear fitting, CERES fluxes were normalized to a fixed solar zenith angle, Earth-Sun distance and atmospheric water vapour content to reduce the noise in the flux observations that was not related to aerosols. The satellite based clear sky estimates for median instantaneous and diurnally averaged ADRE over the study area were -8.8 W m-2, and -5.1 W m-2, respectively. Over heavily industrialized areas the cooling at TOA was two to more than three times the median value, and associated with high AODs (>0.5). Especially during the summer months positive ADREs were observed locally over dark surfaces. This was most probably a method artifact related to systematic change of aerosol type, subvisual cloud contamination or both. The key question in the satellite-based approach is the accuracy of the estimated aerosol-free TOA flux (F0,TOA). Comparison with simulated F0,TOA showed that both the satellite method and the model produced qualitatively similar spatial patterns, but absolute values differed. In 58% of the cases the satellite based F0,TOA was within ±10 W m-2 of the modeled

  17. Anthropogenic Aerosol Effects on Sea Surface Temperatures: Mixed-Layer Ocean Experiments with Explicit Aerosol Representation

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    Anthropogenic aerosols affect the Earth's radiative balance both through direct and indirect effects. These effects can lead to a reduction of the incoming solar radiation at the surface, i.e. dimming, which may lead to a change in sea surface temperatures (SST) or SST pattern. This, in turn, may affect precipitation patterns. The goal of the present work is to achieve an estimate of the equilibrium SST changes under anthropogenic aerosol forcing since industrialisation. We show preliminary results from mixed-layer ocean (MLO) experiments with explicit aerosol representation performed with ECHAM6-HAM. The (fixed) MLO heat flux into the deep ocean was derived from atmosphere only runs with fixed climatological SSTs (1961-1990 average) and present day (year 2000) aerosols and GHG burdens. Some experiments we repeated with an alternative MLO deep ocean heat flux (based on pre-industrial conditions) to test the robustness of our results with regard to this boundary condition. The maximum surface temperature responses towards anthropogenic aerosol and GHG forcing (separately and combined) were derived on a global and regional scale. The same set of experiments was performed with aerosol and GHG forcings representative of different decades over the past one and a half centuries. This allows to assess how SST patterns at equilibrium changed with changing aerosol (and GHG) forcing. Correlating SST responses with the change in downward clear-sky and all-sky shortwave radiation provides a first estimate of the response to anthropogenic aerosols. Our results show a clear contrast in hemispheric surface temperature response, as expected from the inter-hemispheric asymmetry of aerosol forcing The presented work is part of a project aiming at quantifying the effect of anthropogenic aerosol forcing on SSTs and the consequences for global precipitation patterns. Results from this study will serve as a starting point for further experiments involving a dynamic ocean model, which

  18. Impact of Mixing State on Anthropogenic Aerosol Radiative Forcing and Associated Climate Response

    NASA Astrophysics Data System (ADS)

    Avramov, A.; Shin, H. J.; Wang, C.

    2014-12-01

    Atmospheric aerosols affect Earth's radiation balance directly by scattering and absorbing solar radiation and, indirectly, by changing the microphysical structure, lifetime and spatial extent of clouds. The aerosol mixing state to a large extent determines not only their optical properties (direct effect) but also their ability to serve as cloud condensation nuclei or ice nuclei (indirect effect). Results from previous research have highlighted the importance of the aerosol mixing assumptions in radiative forcing estimates in model simulations. Here we take a step further to analyze the differences in associated climate responses, using a multimodal, size- and mixing-dependent aerosol model (MARC) incorporated within the Community Earth System Model (CESM). The new model allows for a detailed representation of aerosol-radiation and aerosol-cloud interactions by including an improved treatment of aerosol mixing state and composition. First, we estimate and compare the magnitudes of direct and indirect forcing of anthropogenic aerosols under different mixing assumptions. We then carry out several century-long fully-coupled climate simulations designed to isolate the climate responses to direct and indirect forcings under the same aerosol mixing assumptions. In our analysis, we specifically focus on the following three climate response components: 1) cloud distribution and coverage; 2) precipitation amount and distribution; and 3) changes in circulation patterns.

  19. Strong radiative heating due to the mixing state of black carbon in atmospheric aerosols

    NASA Astrophysics Data System (ADS)

    Jacobson, Mark Z.

    2001-02-01

    Aerosols affect the Earth's temperature and climate by altering the radiative properties of the atmosphere. A large positive component of this radiative forcing from aerosols is due to black carbon-soot-that is released from the burning of fossil fuel and biomass, and, to a lesser extent, natural fires, but the exact forcing is affected by how black carbon is mixed with other aerosol constituents. From studies of aerosol radiative forcing, it is known that black carbon can exist in one of several possible mixing states; distinct from other aerosol particles (externally mixed) or incorporated within them (internally mixed), or a black-carbon core could be surrounded by a well mixed shell. But so far it has been assumed that aerosols exist predominantly as an external mixture. Here I simulate the evolution of the chemical composition of aerosols, finding that the mixing state and direct forcing of the black-carbon component approach those of an internal mixture, largely due to coagulation and growth of aerosol particles. This finding implies a higher positive forcing from black carbon than previously thought, suggesting that the warming effect from black carbon may nearly balance the net cooling effect of other anthropogenic aerosol constituents. The magnitude of the direct radiative forcing from black carbon itself exceeds that due to CH4, suggesting that black carbon may be the second most important component of global warming after CO2 in terms of direct forcing.

  20. The Radiative Forcing from Biogenic Secondary Organic Aerosol

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  1. Cloud Cover Increase with Increasing Aerosol Absorptivity: A Counterexample to the Conventional Semidirect Aerosol Effect

    NASA Technical Reports Server (NTRS)

    Perlwitz, Jan; Miller, Ron L.

    2010-01-01

    We reexamine the aerosol semidirect effect using a general circulation model and four cases of the single-scattering albedo of dust aerosols. Contrary to the expected decrease in low cloud cover due to heating by tropospheric aerosols, we find a significant increase with increasing absorptivity of soil dust particles in regions with high dust load, except during Northern Hemisphere winter. The strongest sensitivity of cloud cover to dust absorption is found over land during Northern Hemisphere summer. Here even medium and high cloud cover increase where the dust load is highest. The cloud cover change is directly linked to the change in relative humidity in the troposphere as a result of contrasting changes in specific humidity and temperature. More absorption by aerosols leads to larger diabatic heating and increased warming of the column, decreasing relative humidity. However, a corresponding increase in the specific humidity exceeds the temperature effect on relative humidity. The net effect is more low cloud cover with increasing aerosol absorption. The higher specific humidity where cloud cover strongly increases is attributed to an enhanced convergence of moisture driven by dust radiative heating. Although in some areas our model exhibits a reduction of low cloud cover due to aerosol heating consistent with the conventional description of the semidirect effect, we conclude that the link between aerosols and clouds is more varied, depending also on changes in the atmospheric circulation and the specific humidity induced by the aerosols. Other absorbing aerosols such as black carbon are expected to have a similar effect.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Turnock, S. T.; Spracklen, D. V.; Carslaw, K. S.; Mann, G. W.; Woodhouse, M. T.; Forster, P. M.; Haywood, J.; Johnson, C. E.; Dalvi, M.; Bellouin, N.; Sanchez-Lorenzo, A.

    2015-08-01

    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 (Hadley Centre Global Environment Model-United Kingdom Chemistry and Aerosols) coupled chemistry-climate model for the period 1960-2009 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), aerosol size distributions (2008-2009) 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), aerosol number concentrations (N30 NMBF = -0.85; N50 NMBF = -0.65; and N100 NMBF = -0.96) and 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 > 3.0 W m-2 during the period 1970-2009 in response to changes in anthropogenic emissions and aerosol concentrations.

  5. 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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Technical Reports Server (NTRS)

    Zhang, Jiang-Long; Christopher, Sundar A.

    2003-01-01

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

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

    SciTech Connect

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

    2012-10-01

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

  8. Study of aerosol radiative properties under different relative humidity conditions in the thermal infrared region

    NASA Astrophysics Data System (ADS)

    Kuo, C. P.; Yang, P.; Nasiri, S. L.; Liu, X.

    2014-12-01

    In the aerosol transport process, the optical properties of aerosol particles can vary due to humidification or mixing with other kinds of aerosols. Previous studies have shown mixing dust with other types of aerosol tends to make the aerosol more spectrally absorptive, but the degree of impact of relative humidity (RH) along the transport path is not clear. To investigate this effect, we conduct a numerical study to estimate the radiative sensitivity of aerosols under various relative humidity conditions. Specifically, the OPAC (Optical Properties of Aerosols and Clouds) database is used, which provides the optical properties (i.e., the extinction, scattering and absorption coefficient, single-scattering albedo, asymmetry factor and phase function) of ten types of aerosols under various relative humidity conditions. Lookup tables (LUTs) of the bidirectional reflectivity, transmissivity and effective emissivity will be computed for the ten aerosol types for input to the high-spectral-resolution radiative transfer model (HRTM). Using these LUTs, the HTRM can calculate top-of-atmospheric brightness temperatures, which we can use to determine the degree of radiative sensitivity in the infrared spectral region. Furthermore, comparisons between simulations and MODIS observations will be presented.

  9. Improved aerosol radiative properties as a foundation for solar geoengineering risk assessment

    NASA Astrophysics Data System (ADS)

    Dykema, J. A.; Keith, D. W.; Keutsch, F. N.

    2016-07-01

    Side effects resulting from the deliberate injection of sulfate aerosols intended to partially offset climate change have motivated the investigation of alternatives, including solid aerosol materials. Sulfate aerosols warm the tropical tropopause layer, increasing the flux of water vapor into the stratosphere, accelerating ozone loss, and increasing radiative forcing. The high refractive index of some solid materials may lead to reduction in these risks. We present a new analysis of the scattering efficiency and absorption of a range of candidate solid aerosols. We utilize a comprehensive radiative transfer model driven by updated, physically consistent estimates of optical properties. We compute the potential increase in stratospheric water vapor and associated longwave radiative forcing. We find that the stratospheric heating calculated in this analysis indicates some materials to be substantially riskier than previous work. We also find that there are Earth-abundant materials that may reduce some principal known risks relative to sulfate aerosols.

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

    NASA Astrophysics Data System (ADS)

    Gunn, L. N.; Collins, W.

    2010-12-01

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

  11. I. The effect of volcanic aerosols on ultraviolet radiation in Antarctica. II. A novel method for enhancing subsurface radar imaging using radar interferometry

    NASA Astrophysics Data System (ADS)

    Tsitas, Steven Ronald

    The theory of radiative transfer is used to explain how a stratospheric aerosol layer may, for large solar zenith angles, increase the flux of UV-B light at the ground. As previous explanations are heuristic and incomplete, I first provide a rigorous and complete explanation of how this occurs. I show that an aerosol layer lying above Antarctica during spring will decrease the integrated daily dose of biologically weighted irradiance, weighted by the erythema action spectrum, by only up to 5%. Thus after a volcanic eruption, life in Antarctica during spring will suffer the combined effects of the spring ozone hole and ozone destruction induced by volcanic aerosols, with the latter effect only slightly offset by aerosol scattering. I extend subsurface radar imaging by considering the additional information that may be derived from radar interferometry. I show that, under the conditions that temporal and spatial decorrelation between observations is small so that the effects of these decorrelations do not swamp the signature expected from a subsurface layer, the depth of burial of the lower surface may be derived. Also, the echoes from the lower and upper surfaces may be separated. The method is tested with images acquired by SIR-C of the area on the Egypt/Sudan border where buried river channels were first observed by SIR-A. Temporal decorrelation between the images, due to some combination of physical changes in the scene, changes in the spacecraft attitude and errors in the processing by NASA of the raw radar echoes into the synthetic aperture radar images, swamps the expected signature for a layer up to 40 meters thick. I propose a test to determine whether or not simultaneous observations are required, and then detail the radar system requirements for successful application of the method for both possible outcomes of the test. I also describe in detail the possible applications of the method. These include measuring the depth of burial of ice in the polar

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

    SciTech Connect

    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.

  13. Dust Aerosol Impact on North Africa Climate: A GCM Investigation of Aerosol-Cloud-Radiation Interactions Using A-Train Satellite Data

    SciTech Connect

    Gu, Y.; Liou, K. N.; Jiang, Jonathan; Su, Hui; Liu, Xiaohong

    2012-02-15

    The climatic effects of dust aerosols in North Africa have been investigated using the atmospheric general circulation model (AGCM) developed at the University of California, Los Angeles (UCLA). The model includes an efficient and physically based radiation parameterization scheme developed specifically for application to clouds and aerosols. Parameterization of the effective ice particle size in association with the aerosol indirect effect based on cloud and aerosol data retrieved from A-Train satellite observations have been employed in the climate model simulations. Offline simulations reveal that the direct solar, IR, and net forcings by dust aerosols generally increase with increasing aerosol optical depth (AOD). When the dust semi-direct effect is included with the presence of ice clouds, positive IR radiative forcing is enhanced, since ice clouds trap substantial IR radiation, while the positive solar forcing with dust aerosols alone has been changed to negative values due to the strong reflection of solar radiation by clouds, indicating that cloud forcing could exceed aerosol forcing. With the aerosol indirect effect, the net cloud forcing is generally reduced for ice water path (IWP) larger than 20 g m-2. The magnitude of the reduction increases with IWP. AGCM simulations show that the reduced ice crystal mean effective size due to the aerosol first indirect effect result in less OLR and net solar flux at the top of the atmosphere over the cloudy area of the North Africa region because ice clouds with smaller size trap more IR radiation and reflect more solar radiation. The precipitation in the same area, however, increases due to the aerosol indirect effect on ice clouds, corresponding to the enhanced convection as indicated by reduced OLR. The increased precipitation seems to be associated with enhanced ice water contents in this region. The 200 mb radiative heating rate shows more cooling with the aerosol indirect effect since greater cooling is

  14. MODIS Observation of Aerosols over Southern Africa During SAFARI 2000: Data, Validation, and Estimation of Aerosol Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Ichoku, Charles; Kaufman, Yoram; Remer, Lorraine; Chu, D. Allen; Mattoo, Shana; Tanre, Didier; Levy, Robert; Li, Rong-Rong; Kleidman, Richard; Lau, William K. M. (Technical Monitor)

    2001-01-01

    Aerosol properties, including optical thickness and size parameters, are retrieved operationally from the MODIS sensor onboard the Terra satellite launched on 18 December 1999. The predominant aerosol type over the Southern African region is smoke, which is generated from biomass burning on land and transported over the southern Atlantic Ocean. The SAFARI-2000 period experienced smoke aerosol emissions from the regular biomass burning activities as well as from the prescribed burns administered on the auspices of the experiment. The MODIS Aerosol Science Team (MAST) formulates and implements strategies for the retrieval of aerosol products from MODIS, as well as for validating and analyzing them in order to estimate aerosol effects in the radiative forcing of climate as accurately as possible. These activities are carried out not only from a global perspective, but also with a focus on specific regions identified as having interesting characteristics, such as the biomass burning phenomenon in southern Africa and the associated smoke aerosol, particulate, and trace gas emissions. Indeed, the SAFARI-2000 aerosol measurements from the ground and from aircraft, along with MODIS, provide excellent data sources for a more intensive validation and a closer study of the aerosol characteristics over Southern Africa. The SAFARI-2000 ground-based measurements of aerosol optical thickness (AOT) from both the automatic Aerosol Robotic Network (AERONET) and handheld Sun photometers have been used to validate MODIS retrievals, based on a sophisticated spatio-temporal technique. The average global monthly distribution of aerosol from MODIS has been combined with other data to calculate the southern African aerosol daily averaged (24 hr) radiative forcing over the ocean for September 2000. It is estimated that on the average, for cloud free conditions over an area of 9 million square kin, this predominantly smoke aerosol exerts a forcing of -30 W/square m C lose to the terrestrial

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

    NASA Technical Reports Server (NTRS)

    Toon, Owen B.

    1994-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

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

    SciTech Connect

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

    2011-06-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    PubMed

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

    2016-05-24

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

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

    PubMed Central

    Reddington, Carly L.; Carslaw, Kenneth S.

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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

  3. Seasonal variation of atmospheric aerosols and its impact on aerosol radiation forcing over Delhi

    NASA Astrophysics Data System (ADS)

    Singh, S.; Srivastava, M. K.; Bano, T.; Nath, S.; Tanwar, R. S.; Singh, R.

    Seasonal variability in suspended particulate matter concentration optical properties of aerosol and radiation flux have been studied for Delhi station India using long-term data that comprised of ground based and satellite-borne observations Ground based measurements were taken by a hand-held portable spectrometer MICROTOPS II Solar Light Co Inc USA operating at central wavelengths 340 500 675 870 and 1020 nms FWHM pm 2-10 nm The global radiation flux was measured using the CM-21 pyranometer Kipp and Zonen Germany for wavelength range 305-2800 nm The flux for 290-320 nm wavelength range was measured using UV-Biometer Solar Light Co Inc USA The seasonal change in radiative forcing due to seasonal variability in number density and character of the aerosols is done using Santa Barbara Discrete Ordinate Radiation Transfer model SBDART Since the chemical character of the dominating aerosols for different season was not readily available an estimation of the aerosol composition was done using Optical Properties of Aerosols and Cloud OPAC model The output of the OPAC model gives the required parameters for the estimation of radiation forcing by SBDART These include single scattering albedo and asymmetry parameter Initial results reveal three specific seasonal characteristics of aerosols pre-monsoon post monsoon and the winter excluding monsoon period when data is highly irregular due to predominantly cloudy conditions and heavy downpour During pre-monsoon high aerosol optical depth AOD and near zero often

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    Turnock, S. T.; Spracklen, D. V.; Carslaw, K. S.; Mann, G. W.; Woodhouse, M. T.; Forster, P. M.; Haywood, J.; Johnson, C. E.; Dalvi, M.; Bellouin, N.; Sanchez-Lorenzo, A.

    2015-05-01

    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.

  6. Aerosol Indirect Effects on Cirrus Clouds in Global Aerosol-Climate Models

    NASA Astrophysics Data System (ADS)

    Liu, X.; Zhang, K.; Wang, Y.; Neubauer, D.; Lohmann, U.; Ferrachat, S.; Zhou, C.; Penner, J.; Barahona, D.; Shi, X.

    2015-12-01

    Cirrus clouds play an important role in regulating the Earth's radiative budget and water vapor distribution in the upper troposphere. Aerosols can act as solution droplets or ice nuclei that promote ice nucleation in cirrus clouds. Anthropogenic emissions from fossil fuel and biomass burning activities have substantially perturbed and enhanced concentrations of aerosol particles in the atmosphere. Global aerosol-climate models (GCMs) have now been used to quantify the radiative forcing and effects of aerosols on cirrus clouds (IPCC AR5). However, the estimate uncertainty is very large due to the different representation of ice cloud formation and evolution processes in GCMs. In addition, large discrepancies have been found between model simulations in terms of the spatial distribution of ice-nucleating aerosols, relative humidity, and temperature fluctuations, which contribute to different estimates of the aerosol indirect effect through cirrus clouds. In this presentation, four GCMs with the start-of-the art representations of cloud microphysics and aerosol-cloud interactions are used to estimate the aerosol indirect effects on cirrus clouds and to identify the causes of the discrepancies. The estimated global and annual mean anthropogenic aerosol indirect effect through cirrus clouds ranges from 0.1 W m-2 to 0.3 W m-2 in terms of the top-of-the-atmosphere (TOA) net radiation flux, and 0.5-0.6 W m-2 for the TOA longwave flux. Despite the good agreement on global mean, large discrepancies are found at the regional scale. The physics behind the aerosol indirect effect is dramatically different. Our analysis suggests that burden of ice-nucleating aerosols in the upper troposphere, ice nucleation frequency, and relative role of ice formation processes (i.e., homogeneous versus heterogeneous nucleation) play key roles in determining the characteristics of the simulated aerosol indirect effects. In addition to the indirect effect estimate, we also use field campaign

  7. Volcanic aerosols: Chemistry, evolution, and effects

    NASA Technical Reports Server (NTRS)

    Turco, Richard

    1991-01-01

    Stratospheric aerosols have been the subject of scientific speculation since the 1880s, when the powerful eruption of Krakatoa attracted worldwide attention to the upper atmosphere through spectacular optical displays. The presence of a permanent tenuous dust layer in the lower stratosphere was postulated in the 1920s following studies of the twilight glow. Junge collected the first samples of these 'dust' particles and demonstrated that they were actually composed of sulfates, most likely concentrated sulfuric acid (Junge and Manson, 1961; Junge, 1963). Subsequent research has been spurred by the realization that stratospheric particles can influence the surface climate of earth through their effects on atmospheric radiation. Such aerosols can also influence, through chemical and physical effects, the trace composition of the atmosphere, ozone concentrations, and atmospheric electrical properties. The properties of stratospheric aerosols (both the background particles and those enhanced by volcanic eruptions) were measured in situ by balloon ascents and high altitude aircraft sorties. The aerosols were also observed remotely from the ground and from satellites using both active (lidar) and passive (solar occultation) techniques (remote sensing instruments were carried on aircraft and balloon platforms as well). In connection with the experimental work, models were developed to test theories of particle formation and evolution, to guide measurement strategies, to provide a means of connecting laboratory and field data, and to apply the knowledge gained to answer practical questions about global changes in climate, depletion of the ozone layer, and related environmental problems.

  8. Effect of Dust and Anthropogenic Aerosols on Columnar Aerosol Optical Properties over Darjeeling (2200 m asl), Eastern Himalayas, India

    PubMed Central

    Chatterjee, Abhijit; Ghosh, Sanjay K.; Adak, Anandamay; Singh, Ajay K.; Devara, Panuganti C. S.; Raha, Sibaji

    2012-01-01

    Background The loading of atmospheric particulate matter (aerosol) in the eastern Himalaya is mainly regulated by the locally generated anthropogenic aerosols from the biomass burning and by the aerosols transported from the distance sources. These different types of aerosol loading not only affect the aerosol chemistry but also produce consequent signature on the radiative properties of aerosol. Methodology/Principal Findings An extensive study has been made to study the seasonal variations in aerosol components of fine and coarse mode aerosols and black carbon along with the simultaneous measurements of aerosol optical depth on clear sky days over Darjeeling, a high altitude station (2200 masl) at eastern Himalayas during the year 2008. We observed a heavy loading of fine mode dust component (Ca2+) during pre-monsoon (Apr – May) which was higher by 162% than its annual mean whereas during winter (Dec – Feb), the loading of anthropogenic aerosol components mainly from biomass burning (fine mode SO42− and black carbon) were higher (76% for black carbon and 96% for fine mode SO42−) from their annual means. These high increases in dust aerosols during pre-monsoon and anthropogenic aerosols during winter enhanced the aerosol optical depth by 25 and 40%, respectively. We observed that for every 1% increase in anthropogenic aerosols, AOD increased by 0.55% during winter whereas for every 1% increase in dust aerosols, AOD increased by 0.46% during pre-monsoon. Conclusion/Significance The natural dust transport process (during pre-monsoon) plays as important a role in the radiation effects as the anthropogenic biomass burning (during winter) and their differential effects (rate of increase of the AOD with that of the aerosol concentration) are also very similar. This should be taken into account in proper modeling of the atmospheric environment over eastern Himalayas. PMID:22792264

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  10. North Atlantic Aerosol Properties for Radiative Impact Assessments. Derived from Column Closure Analyses in TARFOX and ACE-2

    NASA Technical Reports Server (NTRS)

    Russell, Philip A.; Bergstrom, Robert A.; Schmid, Beat; Livingston, John M.

    2000-01-01

    Aerosol effects on atmospheric radiative fluxes provide a forcing function that can change the climate in potentially significant ways. This aerosol radiative forcing is a major source of uncertainty in understanding the climate change of the past century and predicting future climate. To help reduce this uncertainty, the 1996 Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the 1997 Aerosol Characterization Experiment (ACE-2) measured the properties and radiative effects of aerosols over the Atlantic Ocean. Both experiments used remote and in situ measurements from aircraft and the surface, coordinated with overpasses by a variety of satellite radiometers. TARFOX focused on the urban-industrial haze plume flowing from the United States over the western Atlantic, whereas ACE-2 studied aerosols over the eastern Atlantic from both Europe and Africa. These aerosols often have a marked impact on satellite-measured radiances. However, accurate derivation of flux changes, or radiative forcing, from the satellite measured radiances or retrieved aerosol optical depths (AODs) remains a difficult challenge. Here we summarize key initial results from TARFOX and ACE-2, with a focus on closure analyses that yield aerosol microphysical models for use in improved assessments of flux changes. We show how one such model gives computed radiative flux sensitivities (dF/dAOD) that agree with values measured in TARFOX and preliminary values computed for the polluted marine boundary layer in ACE-2. A companion paper uses the model to compute aerosol-induced flux changes over the North Atlantic from AVHRR-derived AOD fields.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Biomass-burning (BB) aerosols are the significant contributor to the regional/global aerosol loading and radiation budgets. BB aerosols affect the radiation budget of the earth and atmosphere by scattering and absorbing directly the incoming solar and outgoing terrestrial radiation. These aerosols can exert either cooling or warming effect on climate, depending on the balance between scattering and absorption. BB activities in the form of wildland forest fires and agricultural crop burning are very pronounced in the Indochina peninsular regions in Southeast Asia mainly in spring (late February to April) season. The region of interest includes Doi Ang Khang (19.93° N, 99.05° E, 1536 msl) in northern Thailand, as part of the Seven South East Asian Studies (7-SEAS)/BASELInE (Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles & Interactions Experiment) campaign in 2013. In this study, for the first time, the direct aerosol radiative effects of BB aerosols over near-source BB emissions, during the peak loading spring season, in northern Indochina were investigated by using ground-based physical, chemical, and optical properties of aerosols as well as the aerosol optical and radiative transfer models. Information on aerosol parameters in the field campaign was used in the OPAC (Optical Properties of Aerosols and Clouds) model to estimate various optical properties corresponding to aerosol compositions. Clear-sky shortwave direct aerosol radiative effects were further estimated with a raditive transfer model SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer). The columnar aerosol optical depth (AOD500) was found to be ranged from 0.26 to 1.13 (with the mean value 0.71 ± 0.24). Fine-mode (fine mode fraction ≈0.98, angstrom exponent ≈1.8) and significantly absorbing aerosols (columnar single-scattering albedo ≈0.89, asymmetry-parameter ≈0.67 at 441 nm wavelength) dominated in this region. Water soluble and black carbon (BC) aerosols mainly

  12. New Results from Space and Field Observations on the Aerosol Direct and Indirect Radiative Forcing

    NASA Technical Reports Server (NTRS)

    Kaufman, Yoram J.; Remer, Lorraine; Tanre, Didier; Boucher, Olivier; Chin, Mian; Dubovik, Oleg; Holben, Brent

    2002-01-01

    New space observations from the MODIS instrument on board the Terra satellite and analysis of POLDER data flown on the ADEOS satellite, show in great details the spatial and seasonal variability of the global aerosol system. These spaceborne instruments distinguish fine aerosol from man-made regional pollution and biomass burning from mostly natural coarse dust and sea salt aerosol. E.g. fine regional pollution in and around the Indian sub-continent, Europe and North America; smoke from biomass burning in Southern Africa and Southern America; coarse dust from West Africa and mixed dust pollution and smoke from West and central Africa and East Asia. These regions were also studied extensively in focused field experiments and by the distributed AERONET network. The results generate the first climatologies of the aerosol system, are used to derive the aerosol radiative effects and to estimate the anthropogenic component. The measurements are also used to evaluate each other and constrain aerosol transport models.

  13. Effect of aerosols on evapo-transpiration

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  14. Atmospheric effects on insolation in the Brazilian Amazon: Observed modification of solar radiation by clouds and smoke and derived single scattering albedo of fire aerosols

    NASA Astrophysics Data System (ADS)

    Schafer, J. S.; Holben, B. N.; Eck, T. F.; Yamasoe, M. A.; Artaxo, P.

    2002-10-01

    Five aerosol and solar flux monitoring sites were established in Brazil for the Large Scale Biosphere-Atmosphere Experiment in Amazônia (LBA) project. The first two sites were developed in the states of Rondonia and Mato Grosso in January 1999, while the others were initiated in September 1999 in Amazonas, Para, and near Brasilia (later relocated to Acre). Daily insolation [photosynthetically active radiation (PAR) and total solar] for 1999 and 9 months of 2000 was determined from flux measurements, and the daily fraction of theoretical cloud-free, background-aerosol insolation, fB(day), was evaluated for each site. Observed daily shortfall (MJ m-2 d-1) of PAR insolation due to clouds and aerosols (relative to modeled values for background aerosol), and the instantaneous reductions of PAR irradiance due to high aerosol optical thickness (AOT) smoke events are presented for 1999 at Alta Floresta. The ratio of PAR flux to total solar flux (PAR fraction) was examined for all atmospheric conditions during 1999, and the observed dependence of this parameter on column water vapor and smoke AOT was quantified. No significant relationship with cloud amount (as quantified) was found. Instantaneous PAR irradiance measurements and concurrent, cloud-cleared aerosol data from collocated CIMEL sunphotometers were used with a radiative transfer model to investigate the optical properties of smoke aerosols during the burning season. In particular, the single scattering albedo (SSA) was evaluated in the PAR spectral range for AOT440 nm values ranging from 0.8 to 3.0. These estimates were compared with the operational retrievals of the same parameter from algorithms developed by AERONET for CIMEL sunphotometer radiance measurements.

  15. Aerosol effects and corrections in the Halogen Occultation Experiment

    NASA Technical Reports Server (NTRS)

    Hervig, Mark E.; Russell, James M., III; Gordley, Larry L.; Daniels, John; Drayson, S. Roland; Park, Jae H.

    1995-01-01

    The eruptions of Mt. Pinatubo in June 1991 increased stratospheric aerosol loading by a factor of 30, affecting chemistry, radiative transfer, and remote measurements of the stratosphere. The Halogen Occultation Experiment (HALOE) instrument on board Upper Atmosphere Research Satellite (UARS) makes measurements globally for inferring profiles of NO2, H2O, O3, HF, HCl, CH4, NO, and temperature in addition to aerosol extinction at five wavelengths. Understanding and removing the aerosol extinction is essential for obtaining accurate retrievals from the radiometer channels of NO2, H2O and O3 in the lower stratosphere since these measurements are severely affected by contaminant aerosol absorption. If ignored, aerosol absorption in the radiometer measurements is interpreted as additional absorption by the target gas, resulting in anomalously large mixing ratios. To correct the radiometer measurements for aerosol effects, a retrieved aerosol extinction profile is extrapolated to the radiometer wavelengths and then included as continuum attenuation. The sensitivity of the extrapolation to size distribution and composition is small for certain wavelength combinations, reducing the correction uncertainty. The aerosol corrections extend the usable range of profiles retrieved from the radiometer channels to the tropopause with results that agree well with correlative measurements. In situations of heavy aerosol loading, errors due to aerosol in the retrieved mixing ratios are reduced to values of about 15, 25, and 60% in H2O, O3, and NO2, respectively, levels that are much less than the correction magnitude.

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

    NASA Astrophysics Data System (ADS)

    Srivastava, R.; Ramachandran, S.

    2012-12-01

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

  17. Significant radiative impact of volcanic aerosol in the lowermost stratosphere.

    PubMed

    Andersson, Sandra M; Martinsson, Bengt G; Vernier, Jean-Paul; Friberg, Johan; Brenninkmeijer, Carl A M; Hermann, Markus; van Velthoven, Peter F J; Zahn, Andreas

    2015-01-01

    Despite their potential to slow global warming, until recently, the radiative forcing associated with volcanic aerosols in the lowermost stratosphere (LMS) had not been considered. Here we study volcanic aerosol changes in the stratosphere using lidar measurements from the NASA CALIPSO satellite and aircraft measurements from the IAGOS-CARIBIC observatory. Between 2008 and 2012 volcanism frequently affected the Northern Hemisphere stratosphere aerosol loadings, whereas the Southern Hemisphere generally had loadings close to background conditions. We show that half of the global stratospheric aerosol optical depth following the Kasatochi, Sarychev and Nabro eruptions is attributable to LMS aerosol. On average, 30% of the global stratospheric aerosol optical depth originated in the LMS during the period 2008-2011. On the basis of the two independent, high-resolution measurement methods, we show that the LMS makes an important contribution to the overall volcanic forcing. PMID:26158244

  18. Significant radiative impact of volcanic aerosol in the lowermost stratosphere

    PubMed Central

    Andersson, Sandra M.; Martinsson, Bengt G.; Vernier, Jean-Paul; Friberg, Johan; Brenninkmeijer, Carl A. M.; Hermann, Markus; van Velthoven, Peter F. J.; Zahn, Andreas

    2015-01-01

    Despite their potential to slow global warming, until recently, the radiative forcing associated with volcanic aerosols in the lowermost stratosphere (LMS) had not been considered. Here we study volcanic aerosol changes in the stratosphere using lidar measurements from the NASA CALIPSO satellite and aircraft measurements from the IAGOS-CARIBIC observatory. Between 2008 and 2012 volcanism frequently affected the Northern Hemisphere stratosphere aerosol loadings, whereas the Southern Hemisphere generally had loadings close to background conditions. We show that half of the global stratospheric aerosol optical depth following the Kasatochi, Sarychev and Nabro eruptions is attributable to LMS aerosol. On average, 30% of the global stratospheric aerosol optical depth originated in the LMS during the period 2008–2011. On the basis of the two independent, high-resolution measurement methods, we show that the LMS makes an important contribution to the overall volcanic forcing. PMID:26158244

  19. Exploiting Representation of the Aerosol-Radiation interactions in Climate Systems: Observation-based Analyses and Global Climate Modeling

    NASA Astrophysics Data System (ADS)

    Chen, Y. C.; Li, J.; Lee, W. L.; Diner, D. J.; Garay, M. J.; Kalashnikova, O. V.

    2015-12-01

    Aerosols affect the Earth's climate by perturbing the radiation budget through scattering and absorption of solar radiation and emitting thermal infrared radiation (defined and referred to as aerosol direct effect). At first order, it is essential for a model to realistically represent the distributions of clouds, convection, aerosol profiles and their associated radiative properties (cloud fraction and effective radius), which are critical for simulating Earth's surface energy and water budgets. The representation of aerosols and their radiative properties remains problematic both in retrieval and modeling. Up to now, the representation of aerosol optical depth (AOD) in GCMs is still far from agreement with the observation. We evaluate the aerosol simulations from the 20th century CMIP5 simulations, and investigate the biases in aerosol loadings against observations. AOD and retrieved aerosol types (e.g., sea salt, organic matter, sulfate) from MISR, MODIS, and CALIPSO satellite observations are utilized to compare with model simulated aerosols. The impacts of the biases of modeled AOD and cloud fraction on aerosol direct effects in GCMs will be presented.

  20. Coupling Aerosol-Cloud-Radiative Processes in the WRF-Chem Model: Investigating the Radiative Impact of Elevated Point Sources

    SciTech Connect

    Chapman, Elaine G.; Gustafson, William I.; Easter, Richard C.; Barnard, James C.; Ghan, Steven J.; Pekour, Mikhail S.; Fast, Jerome D.

    2009-02-01

    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 slightly 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 domain (the extent of which corresponds to

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

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

    SciTech Connect

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

    2011-11-14

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

  4. Revisiting Aerosol Effects in Global Climate Models Using an Aerosol Lidar Simulator

    NASA Astrophysics Data System (ADS)

    Ma, P. L.; Chepfer, H.; Winker, D. M.; Ghan, S.; Rasch, P. J.

    2015-12-01

    Aerosol effects are considered a major source of uncertainty in global climate models and the direct and indirect radiative forcings have strong model dependency. These forcings are routinely evaluated (and calibrated) against observations, among them satellite retrievals are greatly used for their near-global coverage. However, the forcings calculated from model output are not directly comparable with those computed from satellite retrievals since sampling and algorithmic differences (such as cloud screening, noise reduction, and retrieval) between models and observations are not accounted for. It is our hypothesis that the conventional model validation procedures for comparing satellite observations and model simulations can mislead model development and introduce biases. Hence, we have developed an aerosol lidar simulator for global climate models that simulates the CALIOP lidar signal at 532nm. The simulator uses the same algorithms as those used to produce the "GCM-oriented CALIPSO Aerosol Product" to (1) objectively sample lidar signal profiles; and (2) derive aerosol fields (e.g., extinction profile, aerosol type, etc) from lidar signals. This allows us to sample and derive aerosol fields in the model and real atmosphere in identical ways. Using the Department of Energy's ACME model simulations, we found that the simulator-retrieved aerosol distribution and aerosol-cloud interactions are significantly different from those computed from conventional approaches, and that the model is much closer to satellite estimates than previously believed.

  5. Carbonaceous aerosols influencing atmospheric radiation: Black and organic carbon

    SciTech Connect

    Penner, J.E.

    1994-09-01

    Carbonaceous particles in the atmosphere may both scatter and absorb solar radiation. The fraction associated with the absorbing component is generally referred to as black carbon (BC) and is mainly produced from incomplete combustion processes. The fraction associated with condensed organic compounds is generally referred to as organic carbon (OC) or organic matter and is mainly scattering. Absorption of solar radiation by carbonaceous aerosols may heat the atmosphere, thereby altering the vertical temperature profile, while scattering of solar radiation may lead to a net cooling of the atmosphere/ocean system. Carbonaceous aerosols may also enhance the concentrations of cloud condensation nuclei. This paper summarizes observed concentrations of aerosols in remote continental and marine locations and provides estimates for the fine particle (D < 2.5 {mu}m) source rates of both OC and BC. The source rates for anthropogenic organic aerosols may be as large as the source rates for anthropogenic sulfate aerosols, suggesting a similar magnitude of direct forcing of climate. The role of BC in decreasing the amount of reflected solar radiation by OC and sulfates is discussed. The total estimated forcing depends on the source estimates for organic and black carbon aerosols which are highly uncertain. The role of organic aerosols acting as cloud condensation nuclei (CCN) is also described.

  6. Global profiles of the direct aerosol effect using vertically resolved aerosol data

    NASA Astrophysics Data System (ADS)

    Korras Carraca, Marios Bruno; Pappas, Vasilios; Matsoukas, Christos; Hatzianastassiou, Nikolaos; Vardavas, Ilias

    2014-05-01

    Atmospheric aerosols, both natural and anthropogenic, can cause climate change through their direct, indirect, and semi-direct effects on the radiative energy budget of the Earth-atmosphere system. In general, aerosols cause cooling of the surface and the planet, while they warm the atmosphere due to scattering and absorption of incoming solar radiation. The importance of vertically resolved direct radiative effect (DRE) and heating/cooling effects of aerosols is strong, while large uncertainties still lie with their magnitudes. In order to be able to quantify them throughout the atmosphere, a detailed vertical profile of the aerosol effect is required. Such data were made available recently by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite. CALIOP is the first polarization lidar to fly in space and has been acquiring unique data on aerosols and clouds since June 2006. The aim of this study is to investigate both the vertically resolved geographic and seasonal variation of the DRE due to aerosols. The vertical profile of DRE under all-sky and clear-sky conditions is computed using the deterministic spectral radiative transfer model FORTH. From the DRE, the effect on atmospheric heating/cooling rate profiles due to aerosols can also be derived. We use CALIOP Level 2-Version 3 Layer aerosol optical depth data as input to our radiation transfer model, for a period of 3 complete years (2007-2009). These data are provided on a 5 km horizontal resolution and in up to 8 vertical layers and have been regridded on our model horizontal and vertical resolutions. We use cloud data from the International Satellite Cloud Climatology Project (ISCCP), while the aerosol asymmetry factor and single scattering albedo are taken from the Global Aerosol Data Set (GADS). The model computations are performed on a monthly, 2.5°× 2.5° resolution on global scale, at 40

  7. New Satellite Measurements of Aerosol Direct Radiative Forcing from MODIS, MISR, and POLDER

    NASA Technical Reports Server (NTRS)

    Kaufman, Y.

    2000-01-01

    New set of satellites, MODIS and MISR launched on EOS-Terra and POLDER launched on ADEOS-1, and scheduled for ADEOS-II and PARASOL in orbit with EOS-AQUA, open exciting opportunities to measure aerosol and their radiative forcing of climate. Each of these instruments has a different approach to invert remote sensing data to derive the aerosol properties. MODIS is using wide spectral range 0.47-2.1 micron. MISR is using narrower spectral range (0.44 to 0.87 micron) but observing the same spot from 9 different angles along the satellite track. POLDER using similar wavelengths, uses two dimensional view with a wide angle optics and adds polarization to the inversion process. Among these instruments, we expect to measure the global distribution of aerosol, to distinguish small pollution particles from large particles from deserts and ocean spray. We shall try to measure the aerosol absorption of solar radiation, and their refractive index that indicates the effect of liquid water on the aerosol size and interaction with sunlight. The radiation field measured by these instruments in variety of wavelengths and angles, is also used to derive the effect of the aerosol on reflection of sunlight spectral fluxes to space. When combined with flux measurements at the ground, it gives a complete characterization of the effect of aerosol on solar illumination, heating in the atmosphere and reflection to space.

  8. Revealing the aerosol radiative impact of volcanic ash on synoptic time scales

    NASA Astrophysics Data System (ADS)

    Walter, Carolin; Rieger, Daniel; Gasch, Philipp; Förstner, Jochen; Vogel, Bernhard

    2016-04-01

    Including the interactions of aerosols with radiation in weather forecast models often leads to perturbations of the temperature field even at locations not directly influenced by the regarded aerosols. They arise out of signals propagating with the speed of sound leading to abrupt changes in cloud cover. The temperature perturbations due to these changes hamper the quantification of the aerosol radiative impact as they can appear in the same order of magnitude. In order to reveal the aerosol radiative impact on synoptic time scales we introduce a new method to separate the aerosol induced temperature effect from atmospheric perturbations. We simulated the impact of volcanic ash aerosol on radiation with the new global to regional scale modelling system ICON-ART (ICOsahedral Nonhydrostatic - Aerosols and Reactive Trace gases; Rieger et al., 2015). Within ICON-ART the radiative fluxes and cooling rates are calculated with the RRTM (Rapid Radiative Transfer Model; Mlawer et al., 1997) for 30 longwave and shortwave bands. To determine the optical properties of the prognostic ash aerosol, Mie calculations were conducted for a compilation of ash refractive indices. We obtain a significant change in 2 m temperature of up to several Kelvin for the Puyehue-Cordon Caulle eruption in 2011. In addition to the temperature effect the atmospheric stability is modified and as a consequence the ash concentrations. The temperature effect during the Eyjafjallajökull eruption in 2010 over Europe is much less pronounced. Nevertheless, we are able to show the impact of volcanic ash on the state of the atmosphere by this eruption.

  9. Aerosol Composition and Morphology during the 2005 Marine Stratus Radiation Aerosol and Drizzle Study

    SciTech Connect

    Berkowitz, Carl M.; Jobson, B Tom T.; Alexander, M. Lizabeth; Laskin, Alexander; Laulainen, Nels S.

    2005-12-01

    The composition and morphology of aerosols activated within cloud droplets relative to the properties of aerosols not activated is of central importance to studies directed at improved parameterization of the treatment of aerosols in large-scale models. These models have many applications, including evaluations of the impact of anthropogenic aerosols on climate. To further our understanding of these aerosol characteristics, scientists from the U.S. Department of Energy Atmospheric Science Program (ASP), joined forces with other participants of the Atmospheric Radiation Measurement (ARM) "Marine Stratus Radiation Aerosol and Drizzle Study" between July 4 and July 29, 2005, at Pt. Reyes, California. Observations from in situ aerosol instruments and from the ARM Mobile Facility will be combined in a first look at observations from this period. The in situ aerosol measurements included high time resolution data of size-resolved bulk composition (sulfate, nitrate, NH4, organics, etc.) and single particle analysis to determine elemental composition and morphology. A CCN counter was also deployed to measure the fraction of cloud droplet kernels that are CCN active over a range of super-saturations. Our presentation will partition measurements into periods of cloudy and cloud-free periods, and will also be partitioned between periods associated with northerly back trajectories that arrived at Pt. Reyes after passing along the Washington-Oregon coast, westerly oceanic trajectories and a very limited number of periods when the air flow appeared to be associated with urban areas to the south and southeast.

  10. Optical and radiative-transfer properties of mixed atmospheric aerosols

    NASA Astrophysics Data System (ADS)

    Degheidy, A. R.; Sallah, M.; Elgarayhi, A.; Shaaban, S. M.

    2015-04-01

    The optical and radiative-transfer properties of mixed atmospheric aerosols have been investigated. The aerosol medium is considered as a plane-parallel anisotropic scattering medium with diffusive reflecting boundaries and containing an internal radiation source. The basic components are defined by their complex refractive index, a lognormal size distribution and humidity dependence in hygroscopic particles. The aerosol particles are assumed to be spherical, so the scattering parameters in the form of single scattering albedo, asymmetry factor, scattering, absorption, extinction efficiencies and linear anisotropic coefficient are calculated using the Mie theory. The calculations have been performed for individual aerosol particles, internal and external mixing media. Radiation transfer problem through the considered aerosol medium has been solved in terms of the solution of the corresponding source-free problem with simple boundary conditions. For the solution of the source-free problem, the Variational Pomraning-Eddington technique has been employed. The variation of the radiative-transfer properties (partial radiative fluxes at the medium boundaries) have been calculated and represented graphically for the different aerosols with their different mixing states. A comparison of the obtained results versus available published data has been performed and a very good agreement was observed.

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

    NASA Astrophysics Data System (ADS)

    Russo, Felicita

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

  12. Evaluation of Aerosol Direct Radiative Forcing in MIRAGE

    SciTech Connect

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

    2001-04-01

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

  13. Urban aerosol effects on surface insolation and surface temperature

    NASA Astrophysics Data System (ADS)

    Jin, M.; Burian, S. J.; Remer, L. A.; Shepherd, M. J.

    2007-12-01

    Urban aerosol particulates may play a fundamental role in urban microclimates and city-generated mesoscale circulations via its effects on energy balance of the surface. Key questions that need to be addressed include: (1) How do these particles affect the amount of solar energy reaching the surface and resulting surface temperature? (2) Is the effect the same in all cities? and (3) How does it vary from city to city? Using NASA AERONET in-situ observations, a radiative transfer model, and a regional climate mode (MM5), we assess aerosol effects on surface insolation and surf ace temperature for dense urban-polluted regions. Two big cities, one in a developing country (Beijing, P.R. China) and another in developed country (New York City, USA), are selected for inter-comparison. The study reveals that aerosol effects on surface temperature depends largely on aerosols' optical and chemical properties as well as atmosphere and land surface conditions, such as humidity and land cover. Therefore, the actual magnitudes of aerosol effects differ from city to city. Aerosol measurements from AERONET show both average and extreme cases for aerosol impacts on surface insolation. In general, aerosols reduce surface insolation by 30Wm-2. Nevertheless, in extreme cases, such reduction can exceed 100 Wm-2. Consequently, this reduces surface skin temperature 2-10C in an urban environment.

  14. Evaluation of aerosol direct radiative forcing in MIRAGE

    NASA Astrophysics Data System (ADS)

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

    2001-03-01

    A variety of measurements have been used to evaluate the treatment of aerosol radiative properties and radiative impacts of aerosols simulated by the Model for Integrated Research on Atmospheric Global Exchange (MIRAGE). The treatment of water uptake in MIRAGE agrees with laboratory measurements, and the growth of aerosol extinction with relative humidity in MIRAGE simulations agrees with field measurements. The simulated frequency of relative humidity near 100% is about twice that of analyzed relative humidity. When the analyzed relative humidity is used to calculate aerosol water uptake in MIRAGE, the simulated aerosol optical depth agrees with most surface measurements after cloudy conditions are filtered out and differences between model and station elevations are accounted for, but simulated optical depths are too low over Brazil and central Canada. Simulated optical depths are mostly within a factor of 2 of satellite estimates, but are too high off the east coasts of the United States and China and too low off the coast of West Africa and in the Arabian Sea. The simulated single-scatter albedo is consistent with surface measurements. MIRAGE correctly simulates a larger Ångström exponent near regions with emissions of submicron particles and aerosol precursor gases, and a smaller exponent near regions with emissions of coarse particles. The simulated sensitivity of radiative forcing to aerosol optical depth is consistent with estimates from measurements. The simulated direct forcing is within the uncertainty of estimates from measurements in the North Atlantic.

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

    NASA Astrophysics Data System (ADS)

    Carslaw, Ken; Lee, Lindsay; Reddington, Carly

    2016-04-01

    There has been no systematic assessment of how reduction in the uncertainty of global aerosol models will feed through to the uncertainty in the predicted forcing. We use a global model perturbed parameter ensemble to show that tight observational constraint of aerosol concentrations in the model has a relatively small effect on the aerosol-related uncertainty in the calculated aerosol-cloud forcing between pre-industrial and present day periods. One factor is the low sensitivity of present-day aerosol to natural emissions that determine the pre-industrial aerosol state. But the major cause of the weak constraint is that the full uncertainty space of the model generates a large number of model variants that are "equally acceptable" compared to present-day aerosol observations. The narrow range of aerosol concentrations in the observationally constrained model gives the impression of low aerosol model uncertainty, but this hides a range of very different aerosol models. These multiple so-called "equifinal" model variants predict a wide range of forcings. Equifinality in the aerosol model means that tuning of a small number of model processes to achieve model-observation agreement could give a misleading impression of model robustness.

  16. Radiative transfer model for aerosols in infrared wavelengths for passive remote sensing applications.

    PubMed

    Ben-David, Avishai; Embury, Janon F; Davidson, Charles E

    2006-09-10

    A comprehensive analytical radiative transfer model for isothermal aerosols and vapors for passive infrared remote sensing applications (ground-based and airborne sensors) has been developed. The theoretical model illustrates the qualitative difference between an aerosol cloud and a chemical vapor cloud. The model is based on two and two/four stream approximations and includes thermal emission-absorption by the aerosols; scattering of diffused sky radiances incident from all sides on the aerosols (downwelling, upwelling, left, and right); and scattering of aerosol thermal emission. The model uses moderate resolution transmittance ambient atmospheric radiances as boundary conditions and provides analytical expressions for the information on the aerosol cloud that is contained in remote sensing measurements by using thermal contrasts between the aerosols and diffused sky radiances. Simulated measurements of a ground-based sensor viewing Bacillus subtilis var. niger bioaerosols and kaolin aerosols are given and discussed to illustrate the differences between a vapor-only model (i.e., only emission-absorption effects) and a complete model that adds aerosol scattering effects. PMID:16926922

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  18. Aerosol types and radiative forcing estimates over East Asia

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  19. Application of a coupled aerosol formation: Radiative transfer model to climatic studies of aerosols

    NASA Technical Reports Server (NTRS)

    Toon, O. B.; Pollack, J. B.

    1979-01-01

    A sophisticated one dimensional physical-chemical model of the formation and evolution of stratospheric aerosols was used to predict the size and number concentration of the stratospheric aerosols as functions of time and altitude following: a large volcanic eruption; increased addition of carbonyl sulfide (OCS) or sulfur dioxide (SO2) to the troposphere; increased supersonic aircraft (SST) flights in the stratosphere; and, large numbers of space shuttle (SS) flights through the stratosphere. A radiative-convective one dimensional climate sensitivity study, using the results of the aerosol formation model, was performed to assess the ground level climatic significance of these perturbations to the stratospheric aerosol layer. Volcanic eruptions and large OCS or SO2 increases could cause significant climatic changes. Currently projected SS launches and moderate fleets of SST's are unlikely to upset the stratospheric aerosol layer enough to significantly impact climate.

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

    SciTech Connect

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

    2013-03-20

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

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

    SciTech Connect

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

    2013-06-17

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  3. Impact of Cloud-Borne Aerosol Representation on Aerosol Direct and Indirect Effects

    SciTech Connect

    Ghan, Steven J.; Easter, Richard C.

    2006-09-21

    Aerosol particles attached to cloud droplets are much more likely to be removed from the atmosphere and are much less efficient at scattering sunlight than if unattached. Models used to estimate direct and indirect effects of aerosols employ a variety of representations of such cloud-borne particles. Here we use a global aerosol model with a relatively complete treatment of cloud-borne particles to estimate the sensitivity of simulated aerosol, cloud and radiation fields to various approximations to the representation of cloud-borne particles. We find that neglecting transport of cloud-borne particles introduces little error, but that diagnosing cloud-borne particles produces global mean biases of 20% and local errors of up to 40% for many variables of interest. A treatment that predicts the total mass concentration of cloud-borne particles for each mode yields smaller errors and runs 20% faster than the complete treatment.

  4. Speciated local aerosol characteristics and radiative forcing at a rural midwestern site

    NASA Astrophysics Data System (ADS)

    Dillner, Ann Marie

    2000-11-01

    internally mixed aerosol was shown to suppress forcing. This research supports the view that species other than ammonium sulfate, namely EC, OC and dust-like aerosol, have significant radiative effects. Although the mass percentage of EC may be low at rural sites, ignoring the presence of EC aerosol leads to an over estimation of the aerosol forcing.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    Emissions of biogenic volatile organic compounds (BVOC) have changed in the past millennium due to changes in land use, temperature and CO2 concentrations. Recent model reconstructions of BVOC emissions over the past millennium predicted changes in dominant secondary organic aerosol (SOA) producing BVOC classes (isoprene, monoterpenes and sesquiterpenes). The reconstructions predicted that global isoprene emissions have decreased (land-use changes to crop/grazing land dominate the reduction), while monoterpene and sesquiterpene emissions have increased (temperature increases dominate the increases); however, all three show regional variability due to competition between the various influencing factors. These BVOC changes have largely been anthropogenic in nature, and land-use change was shown to have the most dramatic effect by decreasing isoprene emissions. In this work, we use two modeled estimates of BVOC emissions from the years 1000 to 2000 to test the effect of anthropogenic changes to BVOC emissions on SOA formation, global aerosol size distributions, and radiative effects using the GEOS-Chem-TOMAS global aerosol microphysics model. With anthropogenic emissions (e.g. SO2, NOx, primary aerosols) held at present day values and BVOC emissions changed from year 1000 to year 2000 values, decreases in the number concentration of particles of size Dp > 80 nm (N80) of >25% in year 2000 relative to year 1000 were predicted in regions with extensive land-use changes since year 1000 which led to regional increases in direct plus indirect aerosol radiative effect of >0.5 W m-2 in these regions. We test the sensitivity of our results to BVOC emissions inventory, SOA yields and the presence of anthropogenic emissions; however, the qualitative response of the model to historic BVOC changes remains the same in all cases. Accounting for these uncertainties, we estimate millennial changes in BVOC emissions cause a global mean direct effect of between +0.022 and +0.163 W m-2

  6. Downscaling Aerosols and the Impact of Neglected Subgrid Processes on Direct Aerosol Radiative Forcing for a Representative Global Climate Model Grid Spacing

    SciTech Connect

    Gustafson, William I.; Qian, Yun; Fast, Jerome D.

    2011-07-13

    Recent improvements to many global climate models include detailed, prognostic aerosol calculations intended to better reproduce the observed climate. However, the trace gas and aerosol fields are treated at the grid-cell scale with no attempt to account for sub-grid impacts on the aerosol fields. This paper begins to quantify the error introduced by the neglected sub-grid variability for the shortwave aerosol radiative forcing for a representative climate model grid spacing of 75 km. An analysis of the value added in downscaling aerosol fields is also presented to give context to the WRF-Chem simulations used for the sub-grid analysis. We found that 1) the impact of neglected sub-grid variability on the aerosol radiative forcing is strongest in regions of complex topography and complicated flow patterns, and 2) scale-induced differences in emissions contribute strongly to the impact of neglected sub-grid processes on the aerosol radiative forcing. The two of these effects together, when simulated at 75 km vs. 3 km in WRF-Chem, result in an average daytime mean bias of over 30% error in top-of-atmosphere shortwave aerosol radiative forcing for a large percentage of central Mexico during the MILAGRO field campaign.

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

    SciTech Connect

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

    1996-12-31

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

  8. Radiative absorption enhancement from coatings on black carbon aerosols.

    PubMed

    Cui, Xinjuan; Wang, Xinfeng; Yang, Lingxiao; Chen, Bing; Chen, Jianmin; Andersson, August; Gustafsson, Örjan

    2016-05-01

    The radiative absorption enhancement of ambient black carbon (BC), by light-refractive coatings of atmospheric aerosols, constitutes a large uncertainty in estimates of climate forcing. The direct measurements of radiative absorption enhancement require the experimentally-removing the coating materials in ambient BC-containing aerosols, which remains a challenge. Here, the absorption enhancement of the BC core by non-absorbing aerosol coatings was quantified using a two-step removal of both inorganic and organic matter coatings of ambient aerosols. The mass absorption cross-section (MAC) of decoated/pure atmospheric BC aerosols of 4.4±0.8m(2)g(-1) was enhanced to 9.6±1.8m(2)g(-1) at 678-nm wavelength for ambiently-coated BC aerosols at a rural Northern China site. The enhancement of MAC (EMAC) rises from 1.4±0.3 in fresh combustion emissions to ~3 for aged ambient China aerosols. The three-week high-intensity campaign observed an average EMAC of 2.25±0.55, and sulfates were primary drivers of the enhanced BC absorption. PMID:26874760

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  10. Global Lidar Observations of Aerosol Distribution and Radiative Influence

    NASA Technical Reports Server (NTRS)

    Spinhirne, James; Starr, David OC. (Technical Monitor)

    2001-01-01

    A very visible impact of human activities is the brownish aerosol haze that pervades many industrialized regions as well as areas in the subtropics and tropics where biomass burning occurs. Well known examples are the Asian Brown Cloud, Arctic Haze and East Coast Haze. Atmospheric transport transforms this haze into regional and hemispheric aerosol layers of significant concentrations. The overall impact on the radiation balance of the atmosphere, surface solar irradiance and other meteorology factors is recognized as a major uncertainty for climate change. In order to understand the impact, the global distribution of aerosol and their properties must be known. . A missing element of observations, but critical for understanding transport has been the height distribution of aerosol. Lidar measurements of aerosol height distribution have been important in GLOBE, ACE, INDOEX and other field studies A network of continuously operating eye safe lidar ground sites has now been established for baseline aerosol profiling. In 2002 NASA will launch the Geoscience Laser Altimeter System (GLAS) mission which will provide for the first time global observations of the height distribution of aerosol. The combination of these and other modem satellite observations, field experiments and models of global aerosol composition and transport should begin to unravel the impacts of particles in the atmosphere.

  11. Simulating aerosol-radiation-cloud feedbacks on meteorology and air quality over eastern China under severe haze conditionsin winter

    NASA Astrophysics Data System (ADS)

    Zhang, B.; Wang, Y.; Hao, J.

    2015-03-01

    The aerosol-radiation-cloud feedbacks on meteorology and air quality over eastern China under severe winter haze conditions in January 2013 are simulated using the fully coupled online Weather Research and Forecasting/Chemistry (WRF-Chem) model. Three simulation scenarios including different aerosol configurations are undertaken to distinguish the aerosol's radiative (direct and semi-direct) and indirect effects. Simulated spatial and temporal variations of PM2.5 are generally consistent with surface observations, with a mean bias of -18.9 μg m-3 (-15.0%) averaged over 71 big cities in China. Comparisons between different scenarios reveal that aerosol radiative effects (direct effect and semi-direct effects) result in reductions of downward shortwave flux at the surface, 2 m temperature, 10 m wind speed and planetary boundary layer (PBL) height by up to 84.0 W m-2, 3.2°C, 0.8 m s-1, and 268 m, respectively. The simulated impact of the aerosol indirect effects is comparatively smaller. Through reducing the PBL height and stabilizing lower atmosphere, the aerosol effects lead to increases in surface concentrations of primary pollutants (CO and SO2). Surface O3 mixing ratio is reduced by up to 6.9 ppb (parts per billion) due to reduced incoming solar radiation and lower temperature, while the aerosol feedbacks on PM2.5 mass concentrations show some spatial variations. Comparisons of model results with observations show that inclusion of aerosol feedbacks in the model significantly improves model performance in simulating meteorological variables and improves simulations of PM2.5 temporal distributions over the North China Plain, the Yangtze River delta, the Pearl River delta, and central China. Although the aerosol-radiation-cloud feedbacks on aerosol mass concentrations are subject to uncertainties, this work demonstrates the significance of aerosol-radiation-cloud feedbacks for real-time air quality forecasting under haze conditions.

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  13. The effect of aerosols on northern hemisphere wintertime stationary waves

    NASA Astrophysics Data System (ADS)

    Lewinschal, Anna; Ekman, Annica M. L.

    2010-05-01

    Aerosol particles have a considerable impact on the energy budget of the atmosphere because of their ability to scatter and absorb incoming solar radiation. Since the beginning of the industrialisation a large increase has been seen mainly in the concentrations of sulphate and black carbon as a result of combustion of fossil fuel and biomass burning. Aerosol particles have a relatively short residence time in the atmosphere why the aerosol concentration shows a large variation spatially as well as in time where high concentrations are found close to emission sources. This leads to a highly varying radiative forcing pattern which modifies temperature gradients which in turn can alter the pressure distribution and lead to changes in the circulation in the atmosphere. In this study, the effect on the wintertime planetary scale waves on the northern hemisphere is specifically considered together with the regional climate impact due to changes in the stationary waves. To investigate the effect of aerosols on the circulation a global general circulation model based on the ECMWF operational forecast model is used (EC-Earth). The aerosol description in EC-Earth consists of prescribed monthly mean mass concentration fields of five different types of aerosols: sulphate, black carbon, organic carbon, dust and sea salt. Only the direct radiative effect is considered and the different aerosol types are treated as external mixtures. Changes in the stationary wave pattern are determined by comparing model simulations using present-day and pre-industrial concentrations of aerosol particles. Since the planetary scale waves largely influence the storm tracks and are an important part of the meridional heat transport, changes in the wave pattern may have substantial impact on the climate globally and locally. By looking at changes in the model simulations globally it can be found that the aerosol radiative forcing has the potential to change the stationary wave pattern. Furthermore

  14. CLouds, and Aerosols Radiative Impacts and Forcing: Year 2016 (CLARIFY-2016)

    NASA Astrophysics Data System (ADS)

    Haywood, J. M.; Bellouin, N.; Carslaw, K. S.; Coe, H.; Field, P.; Highwood, E. J.; Redemann, J.; Stier, P.; Wood, R.; Zuidema, P.

    2013-12-01

    Strongly absorbing biomass burning aerosols (BBAs) exist above highly reflectant stratocumulus clouds in the SE Atlantic with implications on the direct (e.g. Haywood et al., 2003), semi-direct (e.g. Johnson et al., 2006), and indirect effect of aerosols, implications on the remote sensing of cloud optical properties, development of clouds and feedback processes. Here, we present an analysis of modelled estimates of the direct effect using twelve models from the AEROCOM project (Myhre et al., 2013) to show that estimates of the direct effect in SE Atlantic range from strongly negative to strongly positive. Furthermore, we evaluate the performance of the HadGEM2 model and show it cannot replicate the extreme values of positive forcing inferred from high spectral resolution satellite retrievals. By examining patterns of deposition, we infer that the indirect effect from biomass burning aerosols is very limited in the model, but without detailed measurements we are unsure of the validity of this inference. We conclude that the SE Atlantic is therefore of key importance in determining the radiative forcing of biomass burning aerosols and provides a very stringent test for global climate models as they need to accurately represent the geographic distribution of the aerosol optical depth, the wavelength dependent aerosol single scattering albedo, the vertical profile of the aerosol, the geographic distribution of the cloud, the cloud fraction, the cloud liquid water content, the cloud droplet effective radii, and the vertical profile of the cloud. These results are used as scientific rationale to justify a new measurement campaign: CLouds and Aerosol Radiative Impacts and Forcing: Year-2016 (CLARIFY-2016). Haywood, J.M., Osborne, S.R. Francis, P.N., Keil, A., Formenti, P., Andreae, M.O., and Kaye, P.H., The mean physical and optical properties of regional haze dominated by biomass burning aerosol measured from the C-130 aircraft during SAFARI 2000, J. Geophys. Res., 108

  15. An initial assessment of the impact of Australian aerosols on surface ultraviolet radiation and implications for human health

    NASA Astrophysics Data System (ADS)

    Chee, C. Y.; Mills, F. P.

    2010-08-01

    Aerosols can have significant influence on surface radiation, and the intense surface ultraviolet radiation Australia experiences contributes to Australia's high incidence rates for related human diseases. Aerosol properties, such as total column aerosol optical depth, have been measured over several years for varying lengths of time at sites across Australia using sunphotometers. Statistical analysis of the average daily aerosol optical depth over sites near Alice Springs, Canberra, Darwin, and Perth provides one measure of the annual atmospheric loading of aerosols over these sites. The sunphotometers used at these sites do not make measurements in the UV-B spectral region and have only one channel in the UV-A spectral region, the regions of most interest for assessing human health impact. Consequently, model calculations using standard aerosol types have been used to make an initial estimate of the impact of the aerosols found over these four sites on surface ultraviolet radiation. The aerosol loading is at times sufficient to significantly reduce the surface ultraviolet radiation, but few such days occur each year. The annual average effect of aerosols on surface ultraviolet radiation, thus, appears to be small compared to lifestyle factors, such as clothing and use of sunscreen.

  16. Atmospheric Teleconnection over Eurasia Induced by Aerosol Radiative Forcing during Boreal Spring

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    The direct effects of aerosols on global and regional climate during boreal spring are investigated based on numerical simulations with the NASA Global Modeling and Assimilation Office finite-volume general circulation model (fvGCM) with Microphyics of Clouds with the Relaxed Arakawa Schubert Scheme (McRAS), using aerosol forcing functions derived from the Goddard Ozone Chemistry Aerosol Radiation and Transport model (GOCART). The authors find that anomalous atmospheric heat sources induced by absorbing aerosols (dust and black carbon) excite a planetary-scale teleconnection pattern in sea level pressure, temperature, and geopotential height spanning North Africa through Eurasia to the North Pacific. Surface cooling due to direct effects of aerosols is found in the vicinity and downstream of the aerosol source regions, that is, South Asia, East Asia, and northern and western Africa. Significant atmospheric heating is found in regions with large loading of dust (over northern Africa and the Middle East) and black carbon (over Southeast Asia). Paradoxically, the most pronounced feature in aerosol-induced surface temperature is an east west dipole anomaly with strong cooling over the Caspian Sea and warming over central and northeastern Asia, where aerosol concentrations are low. Analyses of circulation anomalies show that the dipole anomaly is a part of an atmospheric teleconnection pattern driven by atmospheric heating anomalies induced by absorbing aerosols in the source regions, but the influence was conveyed globally through barotropic energy dispersion and sustained by feedback processes associated with the regional circulations. The surface temperature signature associated with the aerosol-induced teleconnection bears striking resemblance to the spatial pattern of observed long-term trend in surface temperature over Eurasia. Additionally, the boreal spring wave train pattern is similar to that reported by Fukutomi et al. associated with the boreal summer

  17. 3D Radiative Transfer Effects in Multi-Angle/Multi-Spectral Radio-Polarimetric Signals from a Mixture of Clouds and Aerosols Viewed by a Non-Imaging Sensor

    NASA Technical Reports Server (NTRS)

    Davis, Anthony B.; Garay, Michael J.; Xu, Feng; Qu, Zheng; Emde, Claudia

    2013-01-01

    When observing a spatially complex mix of aerosols and clouds in a single relatively large field-of-view, nature entangles their signals non-linearly through polarized radiation transport processes that unfold in the 3D position and direction spaces. In contrast, any practical forward model in a retrieval algorithm will use only 1D vector radiative transfer (vRT) in a linear mixing technique. We assess the difference between the observed and predicted signals using synthetic data from a high-fidelity 3D vRT model with clouds generated using a Large Eddy Simulation model and an aerosol climatology. We find that this difference is signal--not noise--for the Aerosol Polarimetry Sensor (APS), an instrument developed by NASA. Moreover, the worst case scenario is also the most interesting case, namely, when the aerosol burden is large, hence hase the most impact on the cloud microphysics and dynamics. Based on our findings, we formulate a mitigation strategy for these unresolved cloud adjacency effects assuming that some spatial information is available about the structure of the clouds at higher resolution from "context" cameras, as was planned for NASA's ill-fated Glory mission that was to carry the APS but failed to reach orbit. Application to POLDER (POLarization and Directionality of Earth Reflectances) data from the period when PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar) was in the A-train is briefly discussed.

  18. Albedo enhancement and perturbation of radiation balance due to stratospheric aerosols

    NASA Technical Reports Server (NTRS)

    HARSHVARDHAN

    1978-01-01

    The effect of stratospheric aerosols on the earth's monthly zonal radiation balance is investigated using a model layer consisting of 75% H2SO4, which is the primary constituent of the background aerosol layer. The reduction in solar energy absorbed by the earth-atmosphere system is determined through the albedo sensitivity, defined here as the change in albedo per unit mid-visible optical depth of the aerosol layer. The optically thin approximation is used in conjunction with the Henyey-Greenstein phase function for scattering to simplify computations. Satellite derived planetary albedos are used as the frame of reference about which the change in albedo is computed. An infrared radiative transfer model is used to estimate the increased greenhouse effect attributed to the aerosol layer. The infrared heating tends to compensate for the albedo effect in altering the radiation balance. The results indicate that the dominant influence of the thin model stratospheric aerosol layer is an increased reflection of solar energy all over the globe except for the polar-winter region, but the change in the radiation balance is seen to be uniform and small equatorwards of 50%.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  20. Final Technical Report. Cloud and Radiation Testbed (CART) Raman Lidar measurement of atmospheric aerosols for the Atmospheric Radiation Measurement (ARM) Program

    SciTech Connect

    Ferrare, Richard A.

    2002-08-19

    Vertical profiles of aerosol extinction are required for determination of the effects of aerosols on the clear-sky radiative flux. Since recent studies have demonstrated the inability to compute these profiles on surface aerosol measurements alone, vertical profiles of aerosol optical properties must be acquired to compute aerosol radiative effects throughout the entire atmospheric column. Following the recommendation of the ARM Aerosol Working Group, the investigator developed, evaluated, and implemented algorithms for the CART Raman Lidar to provide profiles of aerosol extinction and backscattering. By virtue of its ability to measure vertical profiles of both aerosol extinction and water vapor simultaneously in the same scattering volume, we used the resulting profiles from the CART Raman Lidar to investigate the impact of water vapor and relative humidity on aerosol extinction throughout the column on a continuous and routine basis. The investigator used these the CART Raman Lidar aerosol extinction and backscattering profiles to evaluate the vertical variability of aerosol extinction and the extinction/backscatter ratio over the ARM SGP site.

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  2. The Atmospheric Radiation Measurement Program May 2003 Intensive Operations Period Examining Aerosol Properties and Radiative Influences: Preface to Special Section

    NASA Technical Reports Server (NTRS)

    Ferrare, Richard; Feingold, Graham; Ghan, Steven; Ogren, John; Schmid, Beat; Schwartz, Stephen E.; Sheridan, Pat

    2006-01-01

    Atmospheric aerosols influence climate by scattering and absorbing radiation in clear air (direct effects) and by serving as cloud condensation nuclei, modifying the microphysical properties of clouds, influencing radiation and precipitation development (indirect effects). Much of present uncertainty in forcing of climate change is due to uncertainty in the relations between aerosol microphysical and optical properties and their radiative influences (direct effects) and between microphysical properties and their ability to serve as cloud condensation nuclei at given supersaturations (indirect effects). This paper introduces a special section that reports on a field campaign conducted at the Department of Energy Atmospheric Radiation Measurement site in North Central Oklahoma in May, 2003, examining these relations using in situ airborne measurements and surface-, airborne-, and space-based remote sensing.

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

    USGS Publications Warehouse

    Guo, S.; Leighton, H.

    2008-01-01

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

  4. Near-cloud aerosols in monsoon environment and its impact on radiative forcing

    NASA Astrophysics Data System (ADS)

    Konwar, M.; Panicker, A. S.; Axisa, D.; Prabha, T. V.

    2015-02-01

    In order to understand the near-cloud aerosol properties and their impact on radiative forcing, we utilized in situ aircraft measurements of aerosol particles and cloud droplets during the Cloud Aerosol Interaction and Precipitation Enhancement Experiment carried out over the Indian subcontinent in the monsoon season. From the measurement of aerosol size distribution of diameter range from 0.1 to 50 µm, we reported that aerosol concentrations could be enhanced by 81% and the effective diameter (deff, µm) by a factor of 2 near the cloud edges when compared with regions far from the cloud. These enhanced aerosol concentrations are a function of the relative humidity (RH) in the cloud-free zone, attributed to mixing and entrainment processes in the cloud edges. It is also found that for warm clouds, RH increases exponentially in the near-cloud regions. In addition, deff was increased linearly with RH. Through model simulations, we found that aerosol optical depth decreases with distance from the cloud edge. Further, aerosols in cloud edges were found to increase the reflected flux by 20% compared to cloud-free regions, thus brightening the near-cloud areas.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  7. International Workshop on Stratospheric Aerosols: Measurements, Properties, and Effects

    NASA Technical Reports Server (NTRS)

    Pueschel, Rudolf F. (Editor)

    1991-01-01

    Following a mandate by the International Aerosol Climatology Program under the auspices of International Association of Meteorology and Atmospheric Physics International Radiation Commission, 45 scientists from five nations convened to discuss relevant issues associated with the measurement, properties, and effects of stratospheric aerosols. A summary is presented of the discussions on formation and evolution, transport and fate, effects on climate, role in heterogeneous chemistry, and validation of lidar and satellite remote sensing of stratospheric aerosols. Measurements are recommended of the natural (background) and the volcanically enhanced aerosol (sulfuric acid and silica particles), the exhaust of shuttle, civil aviation and supersonic aircraft operations (alumina, soot, and ice particles), and polar stratospheric clouds (ice, condensed nitric and hydrochloric acids).

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

    NASA Astrophysics Data System (ADS)

    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. Quantifying Aerosol Direct Effects from Broadband Irradiance and Spectral Aerosol Optical Depth Observations

    SciTech Connect

    Creekmore, Torreon N.; Joseph, Everette; Long, Charles N.; Li, Siwei

    2014-05-16

    We outline a methodology using broadband and spectral irradiances to quantify aerosol direct effects on the surface diffuse shortwave (SW) irradiance. Best Estimate Flux data span a 13 year timeframe at the Department of Energy Atmospheric Radiation Measurement Program’s Southern Great Plains (SGP) site. Screened clear-sky irradiances and aerosol optical depth (AOD), for solar zenith angles ≤ 65°, are used to estimate clear-sky diffuse irradiances. We validate against detected clear-sky observations from SGP’s Basic Radiation System (BRS). BRS diffuse irradiances were in accordance with estimates, producing a root-mean-square error and mean bias errors of 4.0 W/m2 and -1.4 W/m2, respectively. Absolute differences show 99% of estimates within ±10 W/m2 (10%) of the mean BRS observations. Clear-sky diffuse estimates are used to derive quantitative estimates of aerosol radiative effects, represented as the aerosol diffuse irradiance (ADI). ADI is the contribution of diffuse SW to global SW, attributable to scattering of atmospheric transmission by natural plus anthropogenic aerosols. Estimated slope for the ADI as a function of AOD indicates an increase of ~22 W/m2 in diffuse SW for every 0.1 increase in AOD. Such significant increases in the diffuse fraction could possibly increase photosynthesis. Annual mean ADI is 28.2 W/m2, and heavy aerosol loading at SGP provides up to a maximum increase of 120 W/m2 in diffuse SW over background conditions. With regard to seasonal variation, the mean diffuse forcings are 17.2, 33.3, 39.0, and 23.6 W/m2 for winter, spring, summer, and fall, respectively.

  10. Impact of transpacific aerosol on air quality over the United States: A perspective from aerosol-cloud-radiation interactions

    NASA Astrophysics Data System (ADS)

    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.

  11. Simulation of aerosol distributions and radiative forcing for INDOEX: Regional climate impacts

    NASA Astrophysics Data System (ADS)

    Collins, William D.; Rasch, Phillip J.; Eaton, Brian E.; Fillmore, David W.; Kiehl, Jeffrey T.; Beck, C. Trevor; Zender, Charles S.

    2002-10-01

    The direct radiative forcing by aerosols over the Indian Ocean region is simulated for the Indian Ocean Experiment (INDOEX) Intensive Field Phase during Spring 1999. The forcing is calculated for the top-of-atmosphere (TOA), surface, and atmosphere by differencing shortwave fluxes computed with and without aerosols. The calculation includes the effects of sea-salt, sulfate, carbonaceous, and soil-dust aerosols. The aerosol distributions are obtained from a global aerosol simulation including assimilation of satellite retrievals of aerosol optical thickness (AOT). The time-dependent, three-dimensional aerosol distributions are derived with a chemical transport model driven with meteorological analyses for this period. The surface albedos are obtained from a land-surface model forced with an identical meteorological analysis and satellite-derived rainfall and insolation. These calculations are consistent with in situ observations of the surface insolation over the central Indian Ocean and with satellite measurements of the reflected shortwave radiation. The calculations show that the surface insolation under clear skies is reduced by as much as 40 W/m2 over the Indian subcontinent by natural and anthropogenic aerosols. This reduction in insolation is accompanied by an increase in shortwave flux absorbed in the atmosphere by 25 W/m2. The inclusion of clouds in the calculations changes the direct effect by less than 2 W/m2 over the Indian subcontinent, although the reduction is much larger over China. The magnitude of the difference between all-sky and clear-sky forcing is quite sensitive to the three-dimensional spatial relationship between the aerosol and cloud fields, and other estimates of the difference for the INDOEX Intensive Field Phase are as large as 5 W/m2.

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

    NASA Astrophysics Data System (ADS)

    Kazil, J.; Stier, P.; Zhang, K.; Quaas, J.; Kinne, S.; O'Donnell, D.; Rast, S.; Esch, M.; Ferrachat, S.; Lohmann, U.; Feichter, J.

    2010-11-01

    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 forcing. 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 forcing 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 pristine clouds owing to the saturation of effects. The large effect of charged nucleation in our simulations is not in contradiction with small effects seen in local

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

    NASA Astrophysics Data System (ADS)

    Kazil, J.; Stier, P.; Zhang, K.; Quaas, J.; Kinne, S.; O'Donnell, D.; Rast, S.; Esch, M.; Ferrachat, S.; Lohmann, U.; Feichter, J.

    2010-05-01

    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 pristine clouds owing to the saturation of effects. The large effect of charged nucleation in our simulations is not in contradiction with small effects seen in local

  14. Evaluating WRF-Chem multi-scale model in simulating aerosol radiative properties over the tropics – A case study over India

    SciTech Connect

    Seethala, C.; Pandithurai, G.; Fast, Jerome D.; Polade, Suraj D.; Reddy, M. S.; Peckham, Steven E.

    2012-01-24

    We utilized WRF-Chem multi-scale model to simulate the regional distribution of aerosols, optical properties and its effect on radiation over India for a winter month. The model is evaluated using measurements obtained from upper-air soundings, AERONET sun photometers, various satellite instruments, and pyranometers operated by the Indian Meteorological Department. The simulated downward shortwave flux was overestimated when the effect of aerosols on radiation and clouds was neglected. Downward shortwave radiation from a simulation that included aerosol-radiation interaction processes was 5 to 25 Wm{sup -2} closer to the observations, while a simulation that included aerosol-cloud interaction processes were another 1 to 20 Wm{sup -2} closer to the observations. For the few observations available, the model usually underestimated particulate concentration. This is likely due to turbulent mixing, transport errors and the lack of secondary organic aerosol treatment in the model. The model efficiently captured the broad regional hotspots such as high aerosol optical depth over Indo-Gangetic basin as well as the northwestern and southern part of India. The regional distribution of aerosol optical depth compares well with AVHRR aerosol optical depth and the TOMS aerosol index. The magnitude and wavelength-dependence of simulated aerosol optical depth was also similar to the AERONET observations across India. Differences in surface shortwave radiation between simulations that included and neglected aerosol-radiation interactions were as high as -25 Wm{sup -2}, while differences in surface shortwave radiation between simulations that included and neglect aerosol-radiation-cloud interactions were as high as -30 Wm{sup -2}. The spatial variations of these differences were also compared with AVHRR observation. This study suggests that the model is able to qualitatively simulate the impact of aerosols on radiation over India; however, additional measurements of particulate

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

    SciTech Connect

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

    2010-07-05

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

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

    NASA Astrophysics Data System (ADS)

    Rao, Roshan

    2016-04-01

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

  17. Radiative Flux Changes by Aerosols from North America, Europe, and Africa over the Atlantic Ocean: Measurements and Calculations from TARFOX and ACE-2

    NASA Technical Reports Server (NTRS)

    Russell, P. B.; Hignett, P.; Livingston, J. M.; Schmid, B.; Chien, A.; Bergstrom, R.; Durkee, P. A.; Hobbs, P. V.; Bates, T. S.; Quinn, P. K.; Condon, Estelle (Technical Monitor)

    1998-01-01

    Aerosol effects on atmospheric radiative fluxes provide a forcing function that is a major source of uncertainty in understanding the past climate and predicting climate change. To help reduce this uncertainty, the 1996 Tropospheric Aerosol Radiative Forcing Experiment (TARFOX) and the 1997 second Aerosol Characterization Experiment (ACE-2) measured the properties and radiative effects of American, European, and African aerosols over the Atlantic. In TARFOX, radiative fluxes and microphysics of the American aerosol were measured from the UK C-130 while optical depth spectra, aerosol composition, and other properties were measured by the University of Washington C-131A and the CIRPAS Pelican. Closure studies show that the measured flux changes agree with those derived from the aerosol measurements using several modelling approaches. The best-fit midvisible single-scatter albedos (approx. 0.89 to 0.93) obtained from the TARFOX flux comparisons are in accord with values derived by independent techniques. In ACE-2 we measured optical depth and extinction spectra for both European urban-marine aerosols and free-tropospheric African dust aerosols, using sunphotometers on the R/V Vodyanitskiy and the Pelican. Preliminary values for the radiative flux sensitivities (Delta Flux / Delta Optical depth) computed for ACE-2 aerosols (boundary layer and African dust) over ocean are similar to those found in TARFOX. Combining a satellite-derived optical depth climatology with the aerosol optical model validated for flux sensitivities in TARFOX provides first-cut estimates of aerosol-induced flux changes over the Atlantic Ocean.

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

    SciTech Connect

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

    2013-11-01

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

  19. Indirect aerosol effect increases CMIP5 models projected Arctic warming

    DOE PAGESBeta

    Chylek, Petr; Vogelsang, Timothy J.; Klett, James D.; Hengartner, Nicholas; Higdon, Dave; Lesins, Glen; Dubey, Manvendra K.

    2016-02-20

    Phase 5 of the Coupled Model Intercomparison Project (CMIP5) climate models’ projections of the 2014–2100 Arctic warming under radiative forcing from representative concentration pathway 4.5 (RCP4.5) vary from 0.9° to 6.7°C. Climate models with or without a full indirect aerosol effect are both equally successful in reproducing the observed (1900–2014) Arctic warming and its trends. However, the 2014–2100 Arctic warming and the warming trends projected by models that include a full indirect aerosol effect (denoted here as AA models) are significantly higher (mean projected Arctic warming is about 1.5°C higher) than those projected by models without a full indirect aerosolmore » effect (denoted here as NAA models). The suggestion is that, within models including full indirect aerosol effects, those projecting stronger future changes are not necessarily distinguishable historically because any stronger past warming may have been partially offset by stronger historical aerosol cooling. In conclusion, the CMIP5 models that include a full indirect aerosol effect follow an inverse radiative forcing to equilibrium climate sensitivity relationship, while models without it do not.« less

  20. A Measurement-Based Climatology of Aerosol Radiative Properties and Direct Radiative Forcing in the Southeastern U.S.-Initial Results from a Regionally-Representative Site

    NASA Astrophysics Data System (ADS)

    Sherman, J. P.; Robertson, L.; Taubman, B.; Brewbaker, A.; Sheridan, P. J.

    2011-12-01

    The southeastern U.S.(SEUS), home to large emission sources of biogenic VOCs, is one of only a few regions where surface temperatures did not increase from 1901-2005. Recent studies (Goldstein et al., 2008) show that negative top-of-atmosphere (TOA) aerosol direct radiative forcing (DRF) is consistent with a warm-season regional cooling effect dominated by secondary organic aerosols resulting from BVOC oxidation in the presence of anthropogenic NOx and SO2. Established in 2009, the Appalachian Atmospheric Interdisciplinary Research Facility (AppalAIR) at Appalachian State University is home to the only co-located NOAA-ESRL and NASA AERONET aerosol monitoring sites in the SEUS. Equipped with a comprehensive list of aerosol optical, microphysical, and newly-added chemical measurements, this regionally representative, high elevation site (1100 m asl) removed from local pollution sources allows us to significantly advance the state of the science by better quantifying regional aerosol DRF, the relative contributions of source types and source regions to DRF, seasonal and diurnal DRF variability, and an estimate of the anthropogenic contribution to DRF. Seasonal statistics of measured aerosol optical and microphysical properties, aerosol optical depth, and aerosol DRF will be presented. The optical property statistics are placed in the context of those measured at the other three U.S.-based NOAA-ESRL aerosol monitoring sites. Winter months are characterized by smaller, more absorbing particles, low aerosol loading, and negligible DRF. Summer months are characterized by lower aerosol concentrations of primarily scattering particles, high aerosol loading, and a significant negative DRF. Aerosols measured at AppalAIR were smaller in size than those measured at the other U.S. NOAA-ESRL sites for all seasons and seasonal variability of aerosol light scattering was largest. Air mass back-trajectories were used to classify aerosols by source type and region for each season in

  1. Effect of tropospheric aerosols upon atmospheric infrared cooling rates

    NASA Technical Reports Server (NTRS)

    Harshvardhan, MR.; Cess, R. D.

    1978-01-01

    The effect of tropospheric aerosols on atmospheric infrared cooling rates is investigated by the use of recent models of infrared gaseous absorption. A radiative model of the atmosphere that incorporates dust as an absorber and scatterer of infrared radiation is constructed by employing the exponential kernel approximation to the radiative transfer equation. Scattering effects are represented in terms of a single scattering albedo and an asymmetry factor. The model is applied to estimate the effect of an aerosol layer made of spherical quartz particles on the infrared cooling rate. Calculations performed for a reference wavelength of 0.55 microns show an increased greenhouse effect, where the net upward flux at the surface is reduced by 10% owing to the strongly enhanced downward emission. There is a substantial increase in the cooling rate near the surface, but the mean cooling rate throughout the lower troposphere was only 10%.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  3. Moisture dynamics in the cloudy and polluted tropical atmosphere: The Cloud Aerosol Radiative Forcing Dynamics Experiment (CARDEX)

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Aerosols are well known to modify the microphysical properties of clouds. This modification is expected to yield brighter clouds that cover a greater area. However, observations from satellites show little inter-hemispheric difference in cloud optical thickness and liquid water path in spite of the clear inter-hemispheric difference in aerosol optical thickness. Furthermore, comparisons of observations with global atmospheric models suggest that models that parameterize the mechanisms of aerosol nucleation of cloud drops but do not resolve cloud-scale dynamics may be overestimating the magnitude of aerosol effects on cloud radiative forcing. Resolving these discrepancies requires a deeper understanding of the factors determining the transport of moisture to the cloud layer and the effects of aerosols on that transport. Towards this goal, we have conducted a new field experiment to study the moisture dynamics in the boundary layer and lower troposphere of the polluted and cloudy tropical atmosphere. The Cloud Aerosol Radiative Forcing Dynamics Experiment (CARDEX) was conducted during the winter of 2012 at the Maldives Climate Observatory - Hanimaadhoo in the tropical northern Indian Ocean during the period of extensive outflow of the South Asian pollution. Pollution in the CARDEX region has been well documented to both modify the microphysical properties of low clouds and strongly absorb solar radiation with significant consequences for the lower atmosphere and surface radiative energy budgets. Three unmanned aerial vehicles (UAVs) flew nearly 60 research flights instrumented to measure turbulent latent and sensible heat fluxes, aerosol concentrations, and cloud microphysical properties. Airborne measurements wer