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  • 1
    Online Resource
    Online Resource
    The libRadtran software package for radiative transfer calculations (version 2.0.1)
    Copernicus GmbH ; 2016
    In:  Geoscientific Model Development Vol. 9, No. 5 ( 2016-05-03), p. 1647-1672
    Details
    In: Geoscientific Model Development, Copernicus GmbH, Vol. 9, No. 5 ( 2016-05-03), p. 1647-1672
    Abstract: Abstract. libRadtran is a widely used software package for radiative transfer calculations. It allows one to compute (polarized) radiances, irradiance, and actinic fluxes in the solar and thermal spectral regions. libRadtran has been used for various applications, including remote sensing of clouds, aerosols and trace gases in the Earth's atmosphere, climate studies, e.g., for the calculation of radiative forcing due to different atmospheric components, for UV forecasting, the calculation of photolysis frequencies, and for remote sensing of other planets in our solar system. The package has been described in Mayer and Kylling (2005). Since then several new features have been included, for example polarization, Raman scattering, a new molecular gas absorption parameterization, and several new parameterizations of cloud and aerosol optical properties. Furthermore, a graphical user interface is now available, which greatly simplifies the usage of the model, especially for new users. This paper gives an overview of libRadtran version 2.0.1 with a focus on new features. Applications including these new features are provided as examples of use. A complete description of libRadtran and all its input options is given in the user manual included in the libRadtran software package, which is freely available at http://www.libradtran.org.
    Type of Medium: Online Resource
    ISSN: 1991-9603
    URL: Article
    URL: Article
    DOI: 10.5194/gmd-9-1647-2016
    DOI: 10.5194/gmd-9-1647-2016-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2016
    detail.hit.zdb_id: 2456725-5
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  • 2
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    Quantifying the mass loading of particles in an ash cloud remobilized from tephra deposits on Iceland
    Copernicus GmbH ; 2017
    In:  Atmospheric Chemistry and Physics Vol. 17, No. 7 ( 2017-04-03), p. 4401-4418
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 17, No. 7 ( 2017-04-03), p. 4401-4418
    Abstract: Abstract. On 16–17 September 2013 strong surface winds over tephra deposits in southern Iceland led to the resuspension and subsequent advection of significant quantities of volcanic ash. The resulting resuspended ash cloud was transported to the south-east over the North Atlantic Ocean and, due to clear skies at the time, was exceptionally well observed in satellite imagery. We use satellite-based measurements in combination with radiative transfer and dispersion modelling to quantify the total mass of ash resuspended during this event. Typically ash clouds from explosive eruptions are identified in satellite measurements from a negative brightness temperature difference (BTD) signal; however this technique assumes that the ash resides at high levels in the atmosphere. Due to a temperature inversion in the troposphere over southern Iceland during 16 September 2013, the resuspended ash cloud was constrained to altitudes of  〈  2 km a.s.l. We show that a positive BTD signal can instead be used to identify ash-containing pixels from satellite measurements. The timing and location of the ash cloud identified using this technique from measurements made by the Visible Infrared Imaging Radiometer Suite (VIIRS) on board the Suomi National Polar-orbiting Partnership (NPP) satellite agree well with model predictions using the dispersion model NAME (Numerical Atmospheric-dispersion Modelling Environment). Total column mass loadings are determined from the VIIRS data using an optimal estimation technique which accounts for the low altitude of the resuspended ash cloud and are used to calibrate the emission rate in the resuspended ash scheme in NAME. Considering the tephra deposits from the recent eruptions of Eyjafjallajökull and Grímsvötn as the potential source area for resuspension for this event, we estimate that  ∼  0.2 Tg of ash was remobilized during 16–17 September 2013.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    URL: Article
    DOI: 10.5194/acp-17-4401-2017
    DOI: 10.5194/acp-17-4401-2017-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2017
    detail.hit.zdb_id: 2092549-9
    detail.hit.zdb_id: 2069847-1
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  • 3
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    Total ozone trends at three northern high-latitude stations
    Copernicus GmbH ; 2023
    In:  Atmospheric Chemistry and Physics Vol. 23, No. 7 ( 2023-04-06), p. 4165-4184
    Details
    In: Atmospheric Chemistry and Physics, Copernicus GmbH, Vol. 23, No. 7 ( 2023-04-06), p. 4165-4184
    Abstract: Abstract. After the decrease of ozone-depleting substances (ODSs) as a consequence of the Montreal Protocol, it is still challenging to detect a recovery in the total column amount of ozone (total ozone) at northern high latitudes. To assess regional total ozone changes in the “ozone-recovery” period (2000–2020) at northern high latitudes, this study investigates trends from ground-based total ozone measurements at three stations in Norway (Oslo, Andøya, and Ny-Ålesund). For this purpose, we combine measurements from Brewer spectrophotometers, ground-based UV filter radiometers (GUVs), and a SAOZ (Système d'Analyse par Observation Zénithale) instrument. The Brewer measurements have been extended to work under cloudy conditions using the global irradiance (GI) technique, which is also presented in this study. We derive trends from the combined ground-based time series with the multiple linear regression model from the Long-term Ozone Trends and Uncertainties in the Stratosphere (LOTUS) project. We evaluate various predictors in the regression model and found that tropopause pressure and lower-stratospheric temperature contribute most to ozone variability at the three stations. We report significantly positive annual trends at Andøya (0.9±0.7 % per decade) and Ny-Ålesund (1.5±0.1 % per decade) and no significant annual trend at Oslo (0.1±0.5 % per decade) but significantly positive trends in autumn at all stations. Finally we found positive but insignificant trends of around 3 % per decade in March at all three stations, which may be an indication of Arctic springtime ozone recovery. Our results contribute to a better understanding of regional total ozone trends at northern high latitudes, which is essential to assess how Arctic ozone responds to changes in ODSs and to climate change.
    Type of Medium: Online Resource
    ISSN: 1680-7324
    URL: Article
    DOI: 10.5194/acp-23-4165-2023
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2023
    detail.hit.zdb_id: 2092549-9
    detail.hit.zdb_id: 2069847-1
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  • 4
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    Impact of 3D cloud structures on the atmospheric trace gas products from UV–Vis sounders – Part 3: Bias estimate using synthetic and observational data
    Copernicus GmbH ; 2022
    In:  Atmospheric Measurement Techniques Vol. 15, No. 11 ( 2022-06-10), p. 3481-3495
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 15, No. 11 ( 2022-06-10), p. 3481-3495
    Abstract: Abstract. Three-dimensional (3D) cloud structures may impact atmospheric trace gas products from ultraviolet–visible (UV–Vis) sounders. We used synthetic and observational data to identify and quantify possible cloud-related bias in NO2 tropospheric vertical column density (TVCD). The synthetic data were based on high-resolution large eddy simulations which were input to a 3D radiative transfer model. The simulated visible spectra for low-earth-orbiting and geostationary geometries were analysed with standard retrieval methods and cloud correction schemes that are employed in operational NO2 satellite products. For the observational data, the NO2 products from the TROPOspheric Monitoring Instrument (TROPOMI) were used, while the Visible Infrared Imaging Radiometer Suite (VIIRS) provided high-spatial-resolution cloud and radiance data. NO2 profile shape, cloud shadow fraction, cloud top height, cloud optical depth, and solar zenith and viewing angles were identified as the metrics being the most important in identifying 3D cloud impacts on NO2 TVCD retrievals. For a solar zenith angle less than about 40∘ the synthetic data show that the NO2 TVCD bias is typically below 10 %, while for larger solar zenith angles the NO2 TVCD is low-biased by tens of percent. The horizontal variability of NO2 and differences in TROPOMI and VIIRS overpass times make it challenging to identify a similar bias in the observational data. However, for optically thick clouds above 3000 m, a low bias appears to be present in the observational data.
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    URL: Article
    DOI: 10.5194/amt-15-3481-2022
    DOI: 10.5194/amt-15-3481-2022-supplement
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2022
    detail.hit.zdb_id: 2505596-3
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  • 5
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    Comparison of dust-layer heights from active and passive satellite sensors
    Copernicus GmbH ; 2018
    In:  Atmospheric Measurement Techniques Vol. 11, No. 5 ( 2018-05-18), p. 2911-2936
    Details
    In: Atmospheric Measurement Techniques, Copernicus GmbH, Vol. 11, No. 5 ( 2018-05-18), p. 2911-2936
    Abstract: Abstract. Aerosol-layer height is essential for understanding the impact of aerosols on the climate system. As part of the European Space Agency Aerosol_cci project, aerosol-layer height as derived from passive thermal and solar satellite sensors measurements have been compared with aerosol-layer heights estimated from CALIOP measurements. The Aerosol_cci project targeted dust-type aerosol for this study. This ensures relatively unambiguous aerosol identification by the CALIOP processing chain. Dust-layer height was estimated from thermal IASI measurements using four different algorithms (from BIRA-IASB, DLR, LMD, LISA) and from solar GOME-2 (KNMI) and SCIAMACHY (IUP) measurements. Due to differences in overpass time of the various satellites, a trajectory model was used to move the CALIOP-derived dust heights in space and time to the IASI, GOME-2 and SCIAMACHY dust height pixels. It is not possible to construct a unique dust-layer height from the CALIOP data. Thus two CALIOP-derived layer heights were used: the cumulative extinction height defined as the height where the CALIOP extinction column is half of the total extinction column, and the geometric mean height, which is defined as the geometrical mean of the top and bottom heights of the dust layer. In statistical average over all IASI data there is a general tendency to a positive bias of 0.5–0.8 km against CALIOP extinction-weighted height for three of the four algorithms assessed, while the fourth algorithm has almost no bias. When comparing geometric mean height there is a shift of −0.5 km for all algorithms (getting close to zero for the three algorithms and turning negative for the fourth). The standard deviation of all algorithms is quite similar and ranges between 1.0 and 1.3 km. When looking at different conditions (day, night, land, ocean), there is more detail in variabilities (e.g. all algorithms overestimate more at night than during the day). For the solar sensors it is found that on average SCIAMACHY data are lower by −1.097 km (−0.961 km) compared to the CALIOP geometric mean (cumulative extinction) height, and GOME-2 data are lower by −1.393 km (−0.818 km).
    Type of Medium: Online Resource
    ISSN: 1867-8548
    URL: Article
    DOI: 10.5194/amt-11-2911-2018
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2018
    detail.hit.zdb_id: 2505596-3
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  • 6
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    Performance comparison of the MODIS and the VIIRS 1.38 μm cirrus cloud channels using libRadtran and CALIOP data
    Elsevier BV ; 2018
    In:  Remote Sensing of Environment Vol. 206 ( 2018-03), p. 363-374
    Details
    In: Remote Sensing of Environment, Elsevier BV, Vol. 206 ( 2018-03), p. 363-374
    Type of Medium: Online Resource
    ISSN: 0034-4257
    URL: Article
    DOI: 10.1016/j.rse.2017.12.040
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2018
    detail.hit.zdb_id: 1498713-2
    SSG: 11
    SSG: 14
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  • 7
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    Ultraviolet radiation in partly snow covered terrain: Observations and three‐dimensional simulations
    American Geophysical Union (AGU) ; 2001
    In:  Geophysical Research Letters Vol. 28, No. 19 ( 2001-10), p. 3665-3668
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 28, No. 19 ( 2001-10), p. 3665-3668
    Abstract: Coastal regions with fiords and mountains with seasonally varying snowcover form complex environments for ultraviolet radiative transfer. The presence of snow causes enhanced levels of UV radiation, the quantitative interpretation of which is only possible with detailed three‐dimensional radiative transfer simulations. Such calculations of the irradiance at 340 nm have been performed for the location of Tromsø, Norway, under cloudless and overcast conditions, moving the snowline from 0 to 1000 m.a.s.l. and finally for snow free conditions. The evolution of the radiation enhancement as the snowline moves up is compared with measurements made by a narrow bandwidth multichannel filter instrument. For a cloudless sky the simulations and measurements exhibit a similar radiation enhancement of 23–27%. For the investigated overcast situation the radiation enhancement is about 40–60%.
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2001GL013034
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2001
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 8
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    Monte Carlo linear accelerator simulation of megavoltage photon beams: Independent determination of initial beam parameters : Monte Carlo benchmarking of megavoltage photon beams
    Wiley ; 2011
    In:  Medical Physics Vol. 39, No. 1 ( 2011-12-09), p. 40-47
    Details
    In: Medical Physics, Wiley, Vol. 39, No. 1 ( 2011-12-09), p. 40-47
    Type of Medium: Online Resource
    ISSN: 0094-2405
    URL: Article
    DOI: 10.1118/1.3668315
    Language: English
    Publisher: Wiley
    Publication Date: 2011
    detail.hit.zdb_id: 1466421-5
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  • 9
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    Fast simulation tool for ultraviolet radiation at the earth’s surface
    SPIE-Intl Soc Optical Eng ; 2005
    In:  Optical Engineering Vol. 44, No. 4 ( 2005-04-01), p. 041012-
    Details
    In: Optical Engineering, SPIE-Intl Soc Optical Eng, Vol. 44, No. 4 ( 2005-04-01), p. 041012-
    Type of Medium: Online Resource
    ISSN: 0091-3286
    URL: Article
    DOI: 10.1117/1.1885472
    Language: English
    Publisher: SPIE-Intl Soc Optical Eng
    Publication Date: 2005
    detail.hit.zdb_id: 2010512-5
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  • 10
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    Tilt error in cryospheric surface radiation measurements at high latitudes: a model study
    Copernicus GmbH ; 2016
    In:  The Cryosphere Vol. 10, No. 2 ( 2016-03-15), p. 613-622
    Details
    In: The Cryosphere, Copernicus GmbH, Vol. 10, No. 2 ( 2016-03-15), p. 613-622
    Abstract: Abstract. We have evaluated the magnitude and makeup of error in cryospheric radiation observations due to small sensor misalignment in in situ measurements of solar irradiance. This error is examined through simulation of diffuse and direct irradiance arriving at a detector with a cosine-response fore optic. Emphasis is placed on assessing total error over the solar shortwave spectrum from 250 to 4500 nm, as well as supporting investigation over other relevant shortwave spectral ranges. The total measurement error introduced by sensor tilt is dominated by the direct component. For a typical high-latitude albedo measurement with a solar zenith angle of 60°, a sensor tilted by 1, 3, and 5° can, respectively introduce up to 2.7, 8.1, and 13.5 % error into the measured irradiance and similar errors in the derived albedo. Depending on the daily range of solar azimuth and zenith angles, significant measurement error can persist also in integrated daily irradiance and albedo. Simulations including a cloud layer demonstrate decreasing tilt error with increasing cloud optical depth.
    Type of Medium: Online Resource
    ISSN: 1994-0424
    URL: Article
    DOI: 10.5194/tc-10-613-2016
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2016
    detail.hit.zdb_id: 2393169-3
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