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

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 SO2, NO2, 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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Extensive reduction of surface UV radiation since 1750 in world's populated regions

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-10457-2009 ◽

2009 ◽

Vol 9 (2) ◽

pp. 10457-10486 ◽

Cited By ~ 1

Author(s):

M. M. Kvalev&aring;g ◽

G. Myhre ◽

C. E. Lund Myhre

Keyword(s):

Uv Radiation ◽

Correlation Coefficients ◽

Ultra Violet ◽

Radiative Transfer Model ◽

Transfer Model ◽

Polar Regions ◽

Ultra Violet Radiation ◽

Wide Range ◽

Extensive Surface ◽

Year 2000

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Validation of a radiative transfer model with measurements of UV radiation inside a commercial aircraft

Journal of Radiological Protection ◽

10.1088/1361-6498/ab5153 ◽

2020 ◽

Vol 40 (1) ◽

pp. 181-196 ◽

Cited By ~ 2

Author(s):

Ralf Meerkötter ◽

Kai Schennetten

Keyword(s):

Radiative Transfer ◽

Uv Radiation ◽

Radiative Transfer Model ◽

Transfer Model ◽

Commercial Aircraft

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Influence of Leaf Specular Reflection on Canopy Radiative Regime Using an Improved Version of the Stochastic Radiative Transfer Model

Remote Sensing ◽

10.3390/rs10101632 ◽

2018 ◽

Vol 10 (10) ◽

pp. 1632 ◽

Cited By ~ 1

Author(s):

Bin Yang ◽

Yuri Knyazikhin ◽

Donghui Xie ◽

Haimeng Zhao ◽

Junqiang Zhang ◽

...

Keyword(s):

Radiative Transfer ◽

Flux Density ◽

Vegetation Index ◽

Radiation Flux ◽

Specular Reflection ◽

Radiative Transfer Model ◽

Transfer Model ◽

Remotely Sensed Data ◽

Wide Range ◽

Radiative Regime

Interpreting remotely-sensed data requires realistic, but simple, models of radiative transfer that occurs within a vegetation canopy. In this paper, an improved version of the stochastic radiative transfer model (SRTM) is proposed by assuming that all photons that have not been specularly reflected enter the leaf interior. The contribution of leaf specular reflection is considered by modifying leaf scattering phase function using Fresnel reflectance. The canopy bidirectional reflectance factor (BRF) estimated from this model is evaluated through comparisons with field-measured maize BRF. The result shows that accounting for leaf specular reflection can provide better performance than that when leaf specular reflection is neglected over a wide range of view zenith angles. The improved version of the SRTM is further adopted to investigate the influence of leaf specular reflection on the canopy radiative regime, with emphases on vertical profiles of mean radiation flux density, canopy absorptance, BRF, and normalized difference vegetation index (NDVI). It is demonstrated that accounting for leaf specular reflection can increase leaf albedo, which consequently increases canopy mean upward/downward mean radiation flux density and canopy nadir BRF and decreases canopy absorptance and canopy nadir NDVI when leaf angles are spherically distributed. The influence is greater for downward/upward radiation flux densities and canopy nadir BRF than that for canopy absorptance and NDVI. The results provide knowledge of leaf specular reflection and canopy radiative regime, and are helpful for forward reflectance simulations and backward inversions. Moreover, polarization measurements are suggested for studies of leaf specular reflection, as leaf specular reflection is closely related to the canopy polarization.

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Improvement of the Simulation of Cloud Longwave Scattering in Broadband Radiative Transfer Models

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-18-0014.1 ◽

2018 ◽

Vol 75 (7) ◽

pp. 2217-2233 ◽

Cited By ~ 7

Author(s):

Guanglin Tang ◽

Ping Yang ◽

George W. Kattawar ◽

Xianglei Huang ◽

Eli J. Mlawer ◽

...

Keyword(s):

Radiative Transfer ◽

Multiple Scattering ◽

General Circulation ◽

General Circulation Models ◽

Radiative Transfer Model ◽

Transfer Model ◽

Discrete Ordinate ◽

Wide Range ◽

Scaling Methods ◽

Computational Errors

Abstract Cloud longwave scattering is generally neglected in general circulation models (GCMs), but it plays a significant and highly uncertain role in the atmospheric energy budget as demonstrated in recent studies. To reduce the errors caused by neglecting cloud longwave scattering, two new radiance adjustment methods are developed that retain the computational efficiency of broadband radiative transfer simulations. In particular, two existing scaling methods and the two new adjustment methods are implemented in the Rapid Radiative Transfer Model (RRTM). The results are then compared with those based on the Discrete Ordinate Radiative Transfer model (DISORT) that explicitly accounts for multiple scattering by clouds. The two scaling methods are shown to improve the accuracy of radiative transfer simulations for optically thin clouds but not effectively for optically thick clouds. However, the adjustment methods reduce computational errors over a wide range, from optically thin to thick clouds. With the adjustment methods, the errors resulting from neglecting cloud longwave scattering are reduced to less than 2 W m−2 for the upward irradiance at the top of the atmosphere and less than 0.5 W m−2 for the surface downward irradiance. The adjustment schemes prove to be more accurate and efficient than a four-stream approximation that explicitly accounts for multiple scattering. The neglect of cloud longwave scattering results in an underestimate of the surface downward irradiance (cooling effect), but the errors are almost eliminated by the adjustment methods (warming effect).

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Using a Parameterization of a Radiative Transfer Model to Build High-Resolution Maps of Typical Clear-Sky UV Index in Catalonia, Spain

Journal of Applied Meteorology ◽

10.1175/jam2237.1 ◽

2005 ◽

Vol 44 (6) ◽

pp. 789-803 ◽

Cited By ~ 13

Author(s):

Jordi Badosa ◽

Josep-Abel González ◽

Josep Calbó ◽

Michiel van Weele ◽

Richard L. McKenzie

Keyword(s):

High Resolution ◽

Radiative Transfer ◽

Zenith Angle ◽

Solar Zenith Angle ◽

Absolute Error ◽

Single Scattering ◽

Radiative Transfer Model ◽

Transfer Model ◽

Uv Index ◽

Wide Range

Abstract To perform a climatic analysis of the annual UV index (UVI) variations in Catalonia, Spain (northeast of the Iberian Peninsula), a new simple parameterization scheme is presented based on a multilayer radiative transfer model. The parameterization performs fast UVI calculations for a wide range of cloudless and snow-free situations and can be applied anywhere. The following parameters are considered: solar zenith angle, total ozone column, altitude, aerosol optical depth, and single-scattering albedo. A sensitivity analysis is presented to justify this choice with special attention to aerosol information. Comparisons with the base model show good agreement, most of all for the most common cases, giving an absolute error within ±0.2 in the UVI for a wide range of cases considered. Two tests are done to show the performance of the parameterization against UVI measurements. One uses data from a high-quality spectroradiometer from Lauder, New Zealand [45.04°S, 169.684°E, 370 m above mean sea level (MSL)], where there is a low presence of aerosols. The other uses data from a Robertson–Berger-type meter from Girona, Spain (41.97°N, 2.82°E, 100 m MSL), where there is more aerosol load and where it has been possible to study the effect of aerosol information on the model versus measurement comparison. The parameterization is applied to a climatic analysis of the annual UVI variation in Catalonia, showing the contributions of solar zenith angle, ozone, and aerosols. High-resolution seasonal maps of typical UV index values in Catalonia are presented.

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Polarization data from SCIAMACHY limb backscatter observations compared to vector radiative transfer model simulations

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-5-2221-2012 ◽

2012 ◽

Vol 5 (2) ◽

pp. 2221-2271

Author(s):

P. Liebing ◽

K. Bramstedt ◽

S. Noël ◽

V. Rozanov ◽

H. Bovensmann ◽

...

Keyword(s):

Radiative Transfer ◽

Polarization Measurement ◽

Radiative Transfer Model ◽

Polarization Sensitivity ◽

Transfer Model ◽

Systematic Bias ◽

Radiometric Calibration ◽

Polarization Data ◽

Imaging Spectrometer ◽

Wide Range

Abstract. SCIAMACHY is a passive imaging spectrometer onboard ENVISAT, designed to obtain trace gas abundances from measured radiances and irradiances in the UV to SWIR range in nadir, limb and occultation viewing modes. Its grating spectrometer introduces a substantial sensitivity to the polarization of the incoming light with nonnegligible effects on the radiometric calibration. To be able to correct for the polarization sensitivity, SCIAMACHY utilizes broadband Polarization Measurement Devices (PMDs). While for the nadir viewing mode the measured atmospheric polarization has been validated against POLDER data (Tilstra and Stammes, 2007, 2010), a similar validation study regarding the limb viewing mode has not yet been performed. This paper aims at an assessment of the quality of the SCIAMACHY limb polarization data. Since limb polarization measurements by other air- or spaceborne instruments in the spectral range of SCIAMACHY are not available, a comparison with radiative transfer simulations by SCIATRAN V3.1(Rozanov et al., 2012) using a wide range of atmospheric parameters is performed. SCIATRAN is a vector radiative transfer model (VRTM) capable of performing calculations of the multiply scattered radiance in a~spherically symmetric atmosphere. The study shows that the limb polarization data exhibit a large systematic bias which is decreasing with wavelength. The most likely reason for this bias is an instrumental phase shift which changes the relative contributions of different Stokes vector components to the PMD signal as compared to on-ground calibration measurements. It is also shown that it is in principle feasible to recalibrate the polarization sensitivity using the in-flight data and the VRTM simulations, enabling also the monitoring of its degradation. Together with an optimization of the algorithm used to calculate the in-flight polarization data an improved polarization correction can increase the radiometric accuracy of SCIAMACHY limb radiance spectra substantially.

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Polarization data from SCIAMACHY limb backscatter observations compared to vector radiative transfer model simulations

Atmospheric Measurement Techniques ◽

10.5194/amt-6-1503-2013 ◽

2013 ◽

Vol 6 (6) ◽

pp. 1503-1520 ◽

Cited By ~ 6

Author(s):

P. Liebing ◽

K. Bramstedt ◽

S. Noël ◽

V. Rozanov ◽

H. Bovensmann ◽

...

Keyword(s):

Radiative Transfer ◽

Polarization Measurement ◽

Radiative Transfer Model ◽

Polarization Sensitivity ◽

Transfer Model ◽

Calibration Data ◽

Radiometric Calibration ◽

Polarization Data ◽

Imaging Spectrometer ◽

Wide Range

Abstract. SCIAMACHY is a passive imaging spectrometer onboard ENVISAT designed to obtain trace gas abundances from measured radiances and irradiances in the UV to SWIR range in nadir-, limb- and occultation-viewing modes. Its grating spectrometer introduces a substantial sensitivity to the polarization of the incoming light with nonnegligible effects on the radiometric calibration. To be able to correct for the polarization sensitivity, SCIAMACHY utilizes broadband Polarization Measurement Devices (PMDs). While for the nadir-viewing mode the measured atmospheric polarization has been validated against POLDER data (Tilstra and Stammes, 2007, 2010), a similar validation study regarding the limb-viewing mode has not yet been performed. This paper aims at an assessment of the quality of the SCIAMACHY limb polarization data. Since limb polarization measurements by other air/spaceborne instruments in the spectral range of SCIAMACHY are not available, a comparison with radiative transfer simulations by SCIATRAN V3.1 (Rozanov et al., 2013) using a wide range of atmospheric parameters is performed. SCIATRAN is a vector radiative transfer model (VRTM) capable of performing calculations of the multiply scattered radiance in a spherically symmetric atmosphere. The study shows that the limb polarization data exhibit a large time-dependent bias that decreases with wavelength. Possible reasons for this bias are a still unknown combination of insufficient accuracy or inconsistencies of the on-ground calibration data, scan mirror degradation and stress induced changes of the polarization response of components inside the optical bench of the instrument. It is shown that it should in principle be feasible to recalibrate the effective polarization sensitivity of the instrument using the in-flight data and VRTM simulations.

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A Parametric Radiative Forcing Model for Contrail Cirrus

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-11-0242.1 ◽

2012 ◽

Vol 51 (7) ◽

pp. 1391-1406 ◽

Cited By ~ 43

Author(s):

U. Schumann ◽

B. Mayer ◽

K. Graf ◽

H. Mannstein

Keyword(s):

Analytical Model ◽

Optical Depth ◽

Zenith Angle ◽

Radiative Forcing ◽

Solar Zenith Angle ◽

Life Cycles ◽

Radiative Transfer Model ◽

Model Parameters ◽

Transfer Model ◽

Wide Range

AbstractA new parameterized analytical model is presented to compute the instantaneous radiative forcing (RF) at the top of the atmosphere (TOA) produced by an additional thin contrail cirrus layer (called “contrail” below). The model calculates the RF using as input the outgoing longwave radiation and reflected solar radiation values at TOA for a contrail-free atmosphere, so that the model is applicable for both cloud-free and cloudy ambient atmospheres. Additional input includes the contrail temperature, contrail optical depth (at 550 nm), effective particle radius, particle habit, solar zenith angle, and the optical depth of cirrus above the contrail layer. The model parameters (5 for longwave and 10 for shortwave) are determined from least squares fits to calculations from the “libRadtran” radiative transfer model over a wide range of atmospheric and surface conditions. The correlation coefficient between model and calculations is larger than 98%. The analytical model is compared with published results, including a 1-yr simulation of global RF, and is found to agree well with previous studies. The fast analytical model is part of a larger modeling system to simulate contrail life cycles (“CoCiP”) and can allow for the rapid simulation of contrail cirrus RF over a wide range of meteorological conditions and for a given size-dependent habit mixture. Ambient clouds are shown to have large local impact on the net RF of contrails. Net RF of contrails may both increase and decrease and even change sign in the presence of higher-level cirrus, depending on solar zenith angle.

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Polarimetric remote sensing in O<sub>2</sub> A and B bands: Sensitivity study and information content analysis for vertical profile of aerosols

10.5194/amt-2015-340 ◽

2016 ◽

Author(s):

Shouguo Ding ◽

Jun Wang ◽

Xiaoguang Xu

Keyword(s):

Information Content ◽

Vertical Profile ◽

Sensitivity Study ◽

Peak Height ◽

Gas Absorption ◽

Radiative Transfer Model ◽

Transfer Model ◽

Aerosol Layer ◽

Gaussian Shape ◽

Wide Range

Abstract. Theoretical analysis is conducted to reveal the information content of aerosol vertical profile in space-borne measurements of the backscattered radiance and degree of linear polarization (DOLP) in the O2 A and B bands. Assuming a quasi-Gaussian shape for aerosol vertical profile characterized by peak height H and half width γ (at half maximum), the Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) is used to simulate the Stokes 4-vector elements of upwelling radiation at the top of atmosphere (TOA) and their Jacobians with respect to H and γ. Calculations for different aerosol types and different combinations of H and γ values show that the wide range of gas absorption optical depth in O2 A and B band enables the sensitivity of backscattered DOLP and radiance at TOA to the aerosol layer at different altitudes. Quantitatively, DOLP in O2 A and B bands is found to be more sensitive to H and γ than radiance, especially over the bright surfaces (with large visible reflectance). In many O2 wavelengths, Degree of Freedom for Signal (DFS) for retrieving H (or γ) generally increases with H (and γ) and can be close to unity in many cases, assuming that the composite uncertainty from surface and aerosol scattering properties as well as measurements is less than 5%. Further analysis demonstrates that DFS needed for simultaneous retrieval of H and γ for high-lofted aerosol profiles (H > 2 km) can be obtained from a combined use of DOLP measurements at ~10 O2 absorption A and B absorption wavelengths. However, challenges still remain for resolving aerosol profiles with H less than 2 km. Future hyperspectral measurements of DOPL in O2 A and B bands are needed to continue studying their potential and their combination with radiance and DOPL in atmospheric window channels for retrieving the vertical profiles of aerosols, especially highly scattering aerosols, over land.

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The impact of atmospheric mineral aerosol deposition on the albedo of snow and sea ice: are snow and sea ice optical properties more important than mineral aerosol optical properties?

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-23131-2015 ◽

2015 ◽

Vol 15 (16) ◽

pp. 23131-23172

Author(s):

M. L. Lamare ◽

J. Lee-Taylor ◽

M. D. King

Keyword(s):

Optical Properties ◽

Sea Ice ◽

Atmospheric Aerosols ◽

Aerosol Deposition ◽

Shortwave Radiation ◽

Radiative Transfer Model ◽

Transfer Model ◽

Polar Regions ◽

Polar Snow ◽

The Impact

Abstract. Knowledge of the albedo of polar regions is crucial for understanding a range of climatic processes that have an impact on a global scale. Light absorbing impurities in atmospheric aerosols deposited on snow and sea ice by aeolian transport absorb solar radiation, reducing albedo. Here, the effects of five mineral aerosol deposits reducing the albedo of polar snow and sea ice are considered. Calculations employing a coupled atmospheric and snow/sea ice radiative-transfer model (TUV-snow) show that the effects of mineral aerosol deposits is strongly dependent on the snow or sea ice type rather than the differences between the aerosol optical characteristics. The change in albedo between five different mineral aerosol deposits with refractive indices varying by a factor of 2 reaches a maximum of 0.0788, whereas the difference between cold polar snow and melting sea ice is 0.8893 for the same mineral loading. Surprisingly, the thickness of a surface layer of snow or sea ice loaded with the same mass-ratio of mineral dust has little effect on albedo. On the contrary, multiple layers of mineral aerosols deposited during episodic events evenly distributed play a similar role in the surface albedo of snow as a loading distributed throughout, even when the layers are further apart. The impact of mineral aerosol deposits is much larger on melting sea ice than on other types of snow and sea ice. Therefore, the higher input of shortwave radiation during the summer melt cycle associated with melting sea ice accelerates the melt process.

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