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Publications (10 of 54) Show all publications
Kanngiesser, F. & Kahnert, M. (2018). Calculation of optical properties of light-absorbing carbon with weakly absorbing coating: A model with tunable transition from film-coating to spherical-shell coating. Journal of Quantitative Spectroscopy and Radiative Transfer, 216, 17-36
Open this publication in new window or tab >>Calculation of optical properties of light-absorbing carbon with weakly absorbing coating: A model with tunable transition from film-coating to spherical-shell coating
2018 (English)In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 216, p. 17-36Article in journal (Refereed) Published
National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-4795 (URN)10.1016/j.jqsrt.2018.05.014 (DOI)000437059600003 ()
Available from: 2018-08-07 Created: 2018-08-07 Last updated: 2018-08-07Bibliographically approved
Kahnert, M. (2018). Information constraints in variational data assimilation. Quarterly Journal of the Royal Meteorological Society, 144(716), 2230-2244
Open this publication in new window or tab >>Information constraints in variational data assimilation
2018 (English)In: Quarterly Journal of the Royal Meteorological Society, ISSN 0035-9009, E-ISSN 1477-870X, Vol. 144, no 716, p. 2230-2244Article in journal (Refereed) Published
National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-5013 (URN)10.1002/qj.3347 (DOI)000450035900015 ()
Available from: 2018-11-28 Created: 2018-11-28 Last updated: 2018-11-28Bibliographically approved
Haapanala, P., Raisanen, P., McFarquhar, G. M., Tiira, J., Macke, A., Kahnert, M., . . . Nousiainen, T. (2017). Disk and circumsolar radiances in the presence of ice clouds. Atmospheric Chemistry And Physics, 17(11), 6865-6882
Open this publication in new window or tab >>Disk and circumsolar radiances in the presence of ice clouds
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2017 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 17, no 11, p. 6865-6882Article in journal (Refereed) Published
National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-4139 (URN)10.5194/acp-17-6865-2017 (DOI)000403214200005 ()
Available from: 2017-08-08 Created: 2017-08-08 Last updated: 2017-08-08Bibliographically approved
Kahnert, M. & Andersson, E. (2017). How much information do extinction and backscattering measurements contain about the chemical composition of atmospheric aerosol?. Atmospheric Chemistry And Physics, 17(5), 3423-3444
Open this publication in new window or tab >>How much information do extinction and backscattering measurements contain about the chemical composition of atmospheric aerosol?
2017 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 17, no 5, p. 3423-3444Article in journal (Refereed) Published
National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-4043 (URN)10.5194/acp-17-3423-2017 (DOI)000397795000003 ()
Available from: 2017-04-12 Created: 2017-04-12 Last updated: 2017-11-29Bibliographically approved
Kahnert, M. (2017). Optical properties of black carbon aerosols encapsulated in a shell of sulfate: comparison of the closed cell model with a coated aggregate model. Optics Express, 25(20), 24579-24593
Open this publication in new window or tab >>Optical properties of black carbon aerosols encapsulated in a shell of sulfate: comparison of the closed cell model with a coated aggregate model
2017 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, no 20, p. 24579-24593Article in journal (Refereed) Published
National Category
Earth and Related Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-4308 (URN)10.1364/OE.25.024579 (DOI)000412048500107 ()29041403 (PubMedID)
Available from: 2017-11-13 Created: 2017-11-13 Last updated: 2017-11-29Bibliographically approved
Andersson, E. & Kahnert, M. (2016). Coupling aerosol optics to the MATCH (v5.5.0) chemical transport model and the SALSA (v1) aerosol microphysics module. Geoscientific Model Development, 9(5), 1803-1826
Open this publication in new window or tab >>Coupling aerosol optics to the MATCH (v5.5.0) chemical transport model and the SALSA (v1) aerosol microphysics module
2016 (English)In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 9, no 5, p. 1803-1826Article in journal (Refereed) Published
Abstract [en]

A new aerosol-optics model is implemented in which realistic morphologies and mixing states are assumed, especially for black carbon particles. The model includes both external and internal mixing of all chemical species, it treats externally mixed black carbon as fractal aggregates, and it accounts for inhomogeneous internal mixing of black carbon by use of a novel "core-grey-shell" model. Simulated results of aerosol optical properties, such as aerosol optical depth, backscattering coefficients and the Angstrom exponent, as well as radiative fluxes are computed with the new optics model and compared with results from an older optics-model version that treats all particles as externally mixed homogeneous spheres. The results show that using a more detailed description of particle morphology and mixing state impacts the aerosol optical properties to a degree of the same order of magnitude as the effects of aerosol-microphysical processes. For instance, the aerosol optical depth computed for two cases in 2007 shows a relative difference between the two optics models that varies over the European region between 28 and 18 %, while the differences caused by the inclusion or omission of the aerosol-microphysical processes range from 50 to 37 %. This is an important finding, suggesting that a simple optics model coupled to a chemical transport model can introduce considerable errors affecting radiative fluxes in chemistry-climate models, compromising comparisons of model results with remote sensing observations of aerosols, and impeding the assimilation of satellite products for aerosols into chemical-transport models.

National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-2199 (URN)10.5194/gmd-9-1803-2016 (DOI)000376937800007 ()
Available from: 2016-07-08 Created: 2016-07-08 Last updated: 2017-11-28Bibliographically approved
Kahnert, M., Nousiainen, T. & Markkanen, J. (2016). Morphological models for inhomogeneous particles: Light scattering by aerosols, cometary dust, and living cells (2ed.). In: Kokhanovsky, Alexander (Ed.), Light Scattering Reviews, Volume 11: Light Scattering and Radiative Transfer (pp. 299-337). Berlin: Springer
Open this publication in new window or tab >>Morphological models for inhomogeneous particles: Light scattering by aerosols, cometary dust, and living cells
2016 (English)In: Light Scattering Reviews, Volume 11: Light Scattering and Radiative Transfer / [ed] Kokhanovsky, Alexander, Berlin: Springer , 2016, 2, p. 299-337Chapter in book (Refereed)
Place, publisher, year, edition, pages
Berlin: Springer, 2016 Edition: 2
National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-3330 (URN)
Available from: 2016-10-14 Created: 2016-10-14 Last updated: 2016-10-14Bibliographically approved
Silver, J. D., Christensen, J. H., Kahnert, M., Robertson, L., Rayner, P. J. & Brandt, J. (2016). Multi-species chemical data assimilation with the Danish Eulerian hemispheric model: system description and verification. Journal of Atmospheric Chemistry, 73(3), 261-302
Open this publication in new window or tab >>Multi-species chemical data assimilation with the Danish Eulerian hemispheric model: system description and verification
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2016 (English)In: Journal of Atmospheric Chemistry, ISSN 0167-7764, E-ISSN 1573-0662, Vol. 73, no 3, p. 261-302Article in journal (Refereed) Published
National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-3036 (URN)10.1007/s10874-015-9326-0 (DOI)000380265800003 ()
External cooperation:
Available from: 2016-09-01 Created: 2016-09-01 Last updated: 2017-11-21Bibliographically approved
Kahnert, M. (2016). Numerical solutions of the macroscopic Maxwell equations for scattering by non-spherical particles: A tutorial review. Paper presented at 15th Conference on Electromagnetic and Light Scattering (ELS), JUN 21-26, 2015, Leipzig, GERMANY. Journal of Quantitative Spectroscopy and Radiative Transfer, 178, 22-37
Open this publication in new window or tab >>Numerical solutions of the macroscopic Maxwell equations for scattering by non-spherical particles: A tutorial review
2016 (English)In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 178, p. 22-37Article in journal (Refereed) Published
Abstract [en]

Numerical solution methods for electromagnetic scattering by non-spherical particles comprise a variety of different techniques, which can be traced back to different assumptions and solution strategies applied to the macroscopic Maxwell equations. One can distinguish between time- and frequency-domain methods; further, one can divide numerical techniques into finite-difference methods (which are based on approximating the differential operators), separation-of-variables methods (which are based on expanding the solution in a complete set of functions, thus approximating the fields), and volume integral-equation methods (which are usually solved by discretisation of the target volume and invoking the long-wave approximation in each volume cell). While existing reviews of the topic often tend to have a target audience of program developers and expert users, this tutorial review is intended to accommodate the needs of practitioners as well as novices to the field. The required conciseness is achieved by limiting the presentation to a selection of illustrative methods, and by omitting many technical details that are not essential at a first exposure to the subject. On the other hand, the theoretical basis of numerical methods is explained with little compromises in mathematical rigour; the rationale is that a good grasp of numerical light scattering methods is best achieved by understanding their foundation in Maxwell's theory. (C) 2015 Elsevier Ltd. All rights reserved.

National Category
Environmental Sciences
Research subject
Environment
Identifiers
urn:nbn:se:smhi:diva-2196 (URN)10.1016/j.jqsrt.2015.10.029 (DOI)000376705900004 ()
Conference
15th Conference on Electromagnetic and Light Scattering (ELS), JUN 21-26, 2015, Leipzig, GERMANY
Available from: 2016-07-08 Created: 2016-07-08 Last updated: 2017-11-28Bibliographically approved
Thomas, M. A., Kahnert, M., Andersson, C., Kokkola, H., Hansson, U., Jones, C., . . . Devasthale, A. (2015). Integration of prognostic aerosol-cloud interactions in a chemistry transport model coupled offline to a regional climate model. Geoscientific Model Development, 8(6), 1885-1898
Open this publication in new window or tab >>Integration of prognostic aerosol-cloud interactions in a chemistry transport model coupled offline to a regional climate model
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2015 (English)In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 8, no 6, p. 1885-1898Article in journal (Refereed) Published
Abstract [en]

To reduce uncertainties and hence to obtain a better estimate of aerosol (direct and indirect) radiative forcing, next generation climate models aim for a tighter coupling between chemistry transport models and regional climate models and a better representation of aerosol-cloud interactions. In this study, this coupling is done by first forcing the Rossby Center regional climate model (RCA4) with ERA-Interim lateral boundaries and sea surface temperature (SST) using the standard cloud droplet number concentration (CDNC) formulation (hereafter, referred to as the 'stand-alone RCA4 version' or 'CTRL' simulation). In the stand-alone RCA4 version, CDNCs are constants distinguishing only between land and ocean surface. The meteorology from this simulation is then used to drive the chemistry transport model, Multiple-scale Atmospheric Transport and Chemistry (MATCH), which is coupled online with the aerosol dynamics model, Sectional Aerosol module for Large Scale Applications (SALSA). CDNC fields obtained from MATCH-SALSA are then fed back into a new RCA4 simulation. In this new simulation (referred to as 'MOD' simulation), all parameters remain the same as in the first run except for the CDNCs provided by MATCH-SALSA. Simulations are carried out with this model setup for the period 2005-2012 over Europe, and the differences in cloud microphysical properties and radiative fluxes as a result of local CDNC changes and possible model responses are analysed. Our study shows substantial improvements in cloud microphysical properties with the input of the MATCH-SALSA derived 3-D CDNCs compared to the stand-alone RCA4 version. This model setup improves the spatial, seasonal and vertical distribution of CDNCs with a higher concentration observed over central Europe during boreal summer (JJA) and over eastern Europe and Russia during winter (DJF). Realistic cloud droplet radii (CD radii) values have been simulated with the maxima reaching 13 mu m, whereas in the stand-alone version the values reached only 5 mu m. A substantial improvement in the distribution of the cloud liquid-water paths (CLWP) was observed when compared to the satellite retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) for the boreal summer months. The median and standard deviation values from the 'MOD' simulation are closer to observations than those obtained using the stand-alone RCA4 version. These changes resulted in a significant decrease in the total annual mean net fluxes at the top of the atmosphere (TOA) by -5 W m(-2) over the domain selected in the study. The TOA net fluxes from the 'MOD' simulation show a better agreement with the retrievals from the Clouds and the Earth's Radiant Energy System (CERES) instrument. The aerosol indirect effects are estimated in the 'MOD' simulation in comparison to the pre-industrial aerosol emissions (1900). Our simulations estimated the domain averaged annual mean total radiative forcing of -0.64 W m(-2) with a larger contribution from the first indirect aerosol effect (-0.57 W m(-2)) than from the second indirect aerosol effect (-0.14 W m(-2)).

National Category
Climate Research
Research subject
Climate
Identifiers
urn:nbn:se:smhi:diva-1972 (URN)10.5194/gmd-8-1885-2015 (DOI)000357125000019 ()
Available from: 2016-04-26 Created: 2016-03-03 Last updated: 2017-11-30Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5695-1356

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