Optical properties in the UV and visible spectral region of organic acids relevant to tropospheric aerosols

Myhre, C. E. Lund; Nielsen, Claus J.

doi:10.5194/acp-4-1759-2004

Cited by 99 publications

(55 citation statements)

References 49 publications

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“…We assume pure scattering aerosol for OC from fossil fuel. Measurements of OC show that the absorption in the UV is quite variable from some components having pure scattering to other compounds having rather strong absorption in the UV region (Barnard et al, 2008;Dinar et al, 2007;Kanakidou et al, 2005;Kirchstetter et al, 2004;Martins, 2009;Myhre and Nielsen, 2004;Sun, 2007). We assume internally mixing for aerosols from biomass burning and thus OC and BC aerosols from this source have the same optical properties.…”

Section: Methodsmentioning

confidence: 99%

Extensive reduction of surface UV radiation since 1750 in world's populated regions

Kvalevåg

Myhre

2009

Atmos. Chem. Phys.

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Abstract. Human activity influences a wide range of components that affect the surface UV radiation levels, among them ozone at high latitudes. We calculate the effect of human-induced changes in the surface erythemally weighted ultra-violet radiation (UV-E) since 1750. We compare results from a radiative transfer model to surface UV-E radiation for year 2000 derived by satellite observations (from Total Ozone Mapping Spectroradiometer) and to ground based measurements at 14 sites. The model correlates well with the observations; the correlation coefficients are 0.97 and 0.98 for satellite and ground based measurements, respectively. In addition to the effect of changes in ozone, we also investigate the effect of changes in SO 2 , NO 2 , the direct and indirect effects of aerosols, albedo changes and aviation-induced contrails and cirrus. The results show an increase of surface UV-E in polar regions, most strongly in the Southern Hemisphere. Furthermore, our study also shows an extensive surface UV-E reduction over most land areas; a reduction up to 20% since 1750 is found in some industrialized regions. This reduction in UV-E over the industrial period is particularly large in highly populated regions.

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Section: Methodsmentioning

confidence: 99%

Extensive reduction of surface UV radiation since 1750 in world's populated regions

Kvalevåg

Myhre

2009

Atmos. Chem. Phys.

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“…Wavelength-dependent specific scattering and absorption coefficients are obtained using Mie calculations from prescribed size distributions and refractive indices, as given in Table A1. Sets of wavelength-dependent complex refractive indices are taken from Toon et al [1976] for ammonium sulphate and sea salt, World Climate Research Program [1986] for fossil fuel black carbon, Haywood et al [2003] for biomass burning, Jarzembski et al [2003], Gosse et al [1997], and Weast [1977] for ammonium nitrate, Balkanski et al [2007] for mineral dust, and Lund- Myhre and Nielsen [2004] for biogenic aerosols. The real part of the refractive index of fossil fuel organic carbon is taken to be equal to that of biomass burning, with the imaginary part set to −0.006i for all wavelengths.…”

Section: Appendix A: Aerosol Schemes In Hadgem2mentioning

confidence: 99%

Aerosol forcing in the Climate Model Intercomparison Project (CMIP5) simulations by HadGEM2-ES and the role of ammonium nitrate

Bellouin¹,

Rae²,

Jones³

et al. 2011

J. Geophys. Res.

440

475

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[1] The latest Hadley Centre climate model, HadGEM2-ES, includes Earth system components such as interactive chemistry and eight species of tropospheric aerosols. It has been run for the period 1860-2100 in support of the fifth phase of the Climate Model Intercomparison Project (CMIP5). Anthropogenic aerosol emissions peak between 1980 and 2020, resulting in a present-day all-sky top of the atmosphere aerosol forcing of −1.6 and −1.4 W m −2 with and without ammonium nitrate aerosols, respectively, for the sum of direct and first indirect aerosol forcings. Aerosol forcing becomes significantly weaker in the 21st century, being weaker than −0.5 W m −2 in 2100 without nitrate. However, nitrate aerosols become the dominant species in Europe and Asia and decelerate the decrease in global mean aerosol forcing. Considering nitrate aerosols makes aerosol radiative forcing 2-4 times stronger by 2100 depending on the representative concentration pathway, although this impact is lessened when changes in the oxidation properties of the atmosphere are accounted for. Anthropogenic aerosol residence times increase in the future in spite of increased precipitation, as cloud cover and aerosol-cloud interactions decrease in tropical and midlatitude regions. Deposition of fossil fuel black carbon onto snow and ice surfaces peaks during the 20th century in the Arctic and Europe but keeps increasing in the Himalayas until the middle of the 21st century. Results presented here confirm the importance of aerosols in influencing the Earth's climate, albeit with a reduced impact in the future, and suggest that nitrate aerosols will partially replace sulphate aerosols to become an important anthropogenic species in the remainder of the 21st century.

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“…STEM employs the SAPRC-99 gaseous mechanism (Carter, 2000), the aerosol thermodynamics module SCAPE II (Simulating Composition of Atmospheric Particles at Equilibrium) (Kim et al, 1993a, b;Kim and Seinfeld, 1995) and the NCAR Tropospheric Ultraviolet-Visible (TUV) radiation model (Madronich and Flocke, 1999). The aerosol species simulated here include inorganic salts (sulfate, nitrate, and associated cations), black carbon, primary organic carbon, sea salt and mineral dust aerosol in 4 size bins: 0.1-0.3 µm, 0.3-1.0 µm, 1.0-2.5 µm, and 2.5-10 µm dry geometric diameter .…”

Section: Calculation Details 421 Model Descriptionsmentioning

confidence: 99%

“…The aerosol single scattering albedo also varies with wavelength. There is stronger absorption at UV wavelengths for dust (e.g., ) and for some, but not all, organic aerosols (e.g., Jacobson, 2001;Lund Myhre and Nielsen, 2004;Kirchstetter et al, 2004). The optical depth due to molecular (Rayleigh) scattering varies as λ −4 with extra features due to absorption.…”

Section: Uncertainties and Correlations Related To The Spectral Integmentioning

confidence: 99%

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

et al. 2006

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Abstract. The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar) radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001). Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regionsCorrespondence to: T. S. Bates (tim.bates@noaa.gov) downwind of major urban/population centers (North Indian Ocean (NIO) during INDOEX, the Northwest Pacific Ocean (NWP) during ACE-Asia, and the Northwest Atlantic Ocean (NWA) during ICARTT), incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART). Measurements of burdens, extinction optical depth (AOD), and direct radiative effect of aerosols (DRE -change in radiative flux due to total aerosols) are used as measurement-model check points to assess uncertainties. In-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity) are used as input parameters to two radiative transfer models (GFDL and UniversityPublished by Copernicus GmbH on behalf of the European Geosciences Union. T. S. Bates et al.:Constraining aerosol climate models with observations of Michigan) to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative transfer calculations by observational inputs increases the clear-sky, 24-h averaged AOD (34±8%), top of atmosphere (TOA) DRE (32±12%), and TOA direct climate forcing of aerosols (DCF -change in radiative flux due to anthropogenic aerosols) (37±7%) relative to values obtained with "a priori" parameterizations of aerosol loadings and properties (GFDL RTM). The resulting constrained clear-sky TOA DCF is −3.3±0.47, −14±2.6, −6.4±2.1 Wm −2 for the NIO, NWP, and NWA, respectively. With the use of constrained quantities (extensive and intensive parameters) the calculated uncertainty in DCF was 25% less than the "structural uncertainties" used in the IPCC-2001 global estimates of direct aerosol climate forcing. Such comparisons with observations and resultant reductions in uncertainties are essential for improving and developing confidence in climate model calculations in...

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Optical properties in the UV and visible spectral region of organic acids relevant to tropospheric aerosols

Cited by 99 publications

References 49 publications

Extensive reduction of surface UV radiation since 1750 in world's populated regions

Extensive reduction of surface UV radiation since 1750 in world's populated regions

Aerosol forcing in the Climate Model Intercomparison Project (CMIP5) simulations by HadGEM2-ES and the role of ammonium nitrate

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

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