Reflection of solar radiation by the Antarctic snow surface at ultraviolet, visible, and near-infrared wavelengths

1994 ◽  
Vol 99 (D9) ◽  
pp. 18669 ◽  
Author(s):  
Thomas C. Grenfell ◽  
Stephen G. Warren ◽  
Peter C. Mullen
Keyword(s):  
Solar Radiation ◽  
Near Infrared ◽  
Snow Surface ◽  
Antarctic Snow ◽  
Infrared Wavelengths ◽  
The Antarctic

scholarly journals Absorption of Solar Radiation at the Antarctic Snow Surface (Abstract)

1988 ◽  
Vol 11 ◽  
pp. 200
Author(s):  
Thomas C. Grenfell ◽  
Stephen G. Warren ◽  
Peter C. Mullen
Keyword(s):  
Grain Size ◽  
Solar Radiation ◽  
Theoretical Calculations ◽  
Solar Spectrum ◽  
Theoretical Models ◽  
Snow Surface ◽  
Snow Albedo ◽  
Infra Red ◽  
Antarctic Snow ◽  
The Antarctic

Solar radiation incident on, and reflected by, the snow surface was measured near the South Pole as a function of wavelength, angle, and distance from the station. The objectives of the study were: (1) to observe spectral albedos of snow across the solar spectrum, (2) to obtain depth profiles of snow-grain radius in order to construct theoretical models of spectral albedo for pure snow, (3) to document the extent and degree of soot pollution due to station activities and to assess whether it could invalidate solar-radiation measurements made close to large stations, and (4) to obtain the spectral distribution of incident solar radiation at the Antarctic surface for various cloud conditions, in order to test radiation models of the Antarctic atmosphere. Spectral albedo, measured under diffuse lighting conditions (overcast cloud) on many days, repeatedly agreed with the results of theoretical models which predicted values approaching unity in the visible and found grain-size to be the most important variable controlling snow albedo in the near-infra-red. A representative albedo curve is shown in Figure 1.The visible albedo values were found to be 98–99% and were relatively insensitive to grain-size. (These results disagree with the only previous measurements of Antarctic snow albedo which had good spectral resolution: those of Kuhn and Siogas. Their maximum albedo was only about 90% in the visible.) The near-infra-red albedo, however, varied substantially among the experiments, due to day-to-day variations in snow grain-size, caused by precipitation and wind drifting. The experimental points in the figure match theoretical calculations for grain radius less than 50 μm at wavelengths beyond 1.5 μm, and 50–100 μm for shorter wavelengths. At the shorter wavelengths the light penetrates more deeply into the snow, so the albedo is sensitive to grains beneath the surface, whereas at the longer wavelengths the albedo is influenced only by the grains very close to the surface. The observed albedos can thus be explained by an increase in grain-size with depth. In order that our measurements would be representative of large areas, we were concerned to avoid possible effects of pollution from the station. We collected samples from the top 20 cm of snow, melted and filtered them, and analyzed the filters. The conclusion is that the pollution is very minor. Just 500 m up-wind of the station there is normally less than 1 ng of carbon per gram of snow (1 ppb). Even down-wind of the station the carbon content did not exceed 3 ppb. For snow grain-sizes typical of Antarctica, our models predict that 15 ppb carbon would reduce snow albedo by only 1% at the most sensitive wavelength. Thus we reject our earlier suggestion that the low visible albedos of Kuhn and Siogas were due to impurities in the snow and now favor other explanations.

scholarly journals Absorption of Solar Radiation at the Antarctic Snow Surface (Abstract)

1988 ◽  
Vol 11 ◽  
pp. 200-200
Author(s):  
Thomas C. Grenfell ◽  
Stephen G. Warren ◽  
Peter C. Mullen
Keyword(s):  
Grain Size ◽  
Solar Radiation ◽  
Theoretical Calculations ◽  
Solar Spectrum ◽  
Theoretical Models ◽  
Snow Surface ◽  
Snow Albedo ◽  
Infra Red ◽  
Antarctic Snow ◽  
The Antarctic

Solar radiation incident on, and reflected by, the snow surface was measured near the South Pole as a function of wavelength, angle, and distance from the station. The objectives of the study were: (1) to observe spectral albedos of snow across the solar spectrum, (2) to obtain depth profiles of snow-grain radius in order to construct theoretical models of spectral albedo for pure snow, (3) to document the extent and degree of soot pollution due to station activities and to assess whether it could invalidate solar-radiation measurements made close to large stations, and (4) to obtain the spectral distribution of incident solar radiation at the Antarctic surface for various cloud conditions, in order to test radiation models of the Antarctic atmosphere.Spectral albedo, measured under diffuse lighting conditions (overcast cloud) on many days, repeatedly agreed with the results of theoretical models which predicted values approaching unity in the visible and found grain-size to be the most important variable controlling snow albedo in the near-infra-red. A representative albedo curve is shown in Figure 1.The visible albedo values were found to be 98–99% and were relatively insensitive to grain-size. (These results disagree with the only previous measurements of Antarctic snow albedo which had good spectral resolution: those of Kuhn and Siogas. Their maximum albedo was only about 90% in the visible.) The near-infra-red albedo, however, varied substantially among the experiments, due to day-to-day variations in snow grain-size, caused by precipitation and wind drifting. The experimental points in the figure match theoretical calculations for grain radius less than 50 μm at wavelengths beyond 1.5 μm, and 50–100 μm for shorter wavelengths. At the shorter wavelengths the light penetrates more deeply into the snow, so the albedo is sensitive to grains beneath the surface, whereas at the longer wavelengths the albedo is influenced only by the grains very close to the surface. The observed albedos can thus be explained by an increase in grain-size with depth.In order that our measurements would be representative of large areas, we were concerned to avoid possible effects of pollution from the station. We collected samples from the top 20 cm of snow, melted and filtered them, and analyzed the filters. The conclusion is that the pollution is very minor. Just 500 m up-wind of the station there is normally less than 1 ng of carbon per gram of snow (1 ppb). Even down-wind of the station the carbon content did not exceed 3 ppb. For snow grain-sizes typical of Antarctica, our models predict that 15 ppb carbon would reduce snow albedo by only 1% at the most sensitive wavelength. Thus we reject our earlier suggestion that the low visible albedos of Kuhn and Siogas were due to impurities in the snow and now favor other explanations.

scholarly journals Antarctic atmospheric transparency at infrared and millimetre wavelengths

1992 ◽  
Vol 9 ◽  
pp. 579-579
Author(s):  
John Bally
Keyword(s):  
Near Infrared ◽  
Polar Vortex ◽  
High Elevation ◽  
Moist Air ◽  
Atmospheric Water ◽  
Atmospheric Water Vapour ◽  
The Earth ◽  
Infrared Wavelengths ◽  
The Antarctic ◽  
Astrophysical Research

The Antarctic Plateau is the best site on Earth for astrophysical research from millimetre to near-infrared wavelengths. The low temperature, high elevation on top of the ice sheet, and the Polar Vortex, which blocks the infusion of moist air, result in extremely low column densities of atmospheric water vapour. These unique conditions may result in the clearest and darkest sky available from the surface of the Earth in this wavelength range.

Sensible heat exchange at the Antarctic snow surface: a study with automatic weather stations

2005 ◽  
Vol 25 (8) ◽  
pp. 1081-1101 ◽  
Author(s):  
Michiel van den Broeke ◽  
Dirk van As ◽  
Carleen Reijmer ◽  
Roderik van de Wal
Keyword(s):  
Heat Exchange ◽  
Sensible Heat ◽  
Snow Surface ◽  
Antarctic Snow ◽  
Weather Stations ◽  
The Antarctic

Porphyrin nanorods-polymer composites for solar radiation harvesting applications

2014 ◽  
Vol 18 (12) ◽  
pp. 1145-1156 ◽  
Author(s):  
Nametso P. Mongwaketsi ◽  
Lebogang Kotsedi ◽  
Zebib Y. Nuru ◽  
Raymond Sparrow ◽  
Gyozo Garab ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Polymer Composites ◽  
Near Infrared ◽  
Structural Similarity ◽  
Morphological Properties ◽  
Key Factors ◽  
Key Factor ◽  
Harvesting Systems ◽  
Microscopic Studies ◽  
Infrared Wavelengths

The interest in exploring porphyrin-based nanostructures for artificial solar radiation harvesting stems from their structural similarity to chlorophylls. In nature, the precise organization and orientation of the chlorophylls result in efficient absorption of light energy. Inspired by these naturally occurring architectures relevant optical studies including the dynamics of intermolecular and intra-molecular processes of the porphyrin nanorods were investigated. The design of artificial light harvesting systems requires several key factors, such as absorption in the UV-visible and near-infrared wavelengths, energy transfer ability and the selection of light absorbing pigments. Another key factor is the organizational structure through which the components will interact. We attempted to accomplish this by incorporating porphyrin nanorods into polymer matrices and this will also aid in achieving an arrangement where they can be directly used as devices. The nanorods were embedded in a polymeric matrix, using latex technology and electrospinning which gave the possibility of investigating the orientation of nanorods in the polymer. Spectroscopic and microscopic studies were conducted to investigate the optical and morphological properties of the porphyrin nanorods-polymer composites for applications in artificial solar radiation harvesting systems.

scholarly journals Spectral Radiation Modeling for the Antarctic Plateau: Effects of Clouds, Ozone and CO2 ON THE Radiation Budget(Abstract only)

1982 ◽  
Vol 3 ◽  
pp. 356 ◽  
Author(s):  
Stephen G. Warren ◽  
Warren J. Wiscombe
Keyword(s):  
Water Vapor ◽  
Solar Radiation ◽  
Zenith Angle ◽  
Surface Albedo ◽  
Radiation Budget ◽  
Radiation Balance ◽  
Snow Surface ◽  
Absorption Bands ◽  
Planetary Albedo ◽  
The Antarctic

The radiation balance at and above a snow-covered surface is affected not only by the high general level of the surface albedo, but also by the strong spectral variation of that albedo. Furthermore, the fact that clouds and snow have highly correlated optical properties means that the radiative problem of clouds over a snow surface is a particularly difficult one. Both for its own intrinsic interest, and because it is in many ways as clear an example of snowatmosphere radiative interactions as one is likely to find, we have chosen to make spectrally detailed model calculations of solar and long-wave radiation over Antarctica using an atmospheric radiation model of Wiscombe (1975) coupled to the recent snow reflectivity model of Wiscombe and Warren (1980). Typical clear and cloudy situations are studied. Radiative fluxes are examined particularly at the surface and the top of the atmosphere since these are the locations of most past and future measurements. Radiation budget calculations are compared with observations at Plateau station for various sun angles and cloud conditions. The effects on the radiation balance of a sub-visible ice-crystal cloud (“clear-sky ice-crystal precipitation”), as well as observed water clouds over the snow surface are investigated. Because the snow of the Antarctic plateau is very clean, falls throughout the summer, and never melts, we can make accurate calculations of the surface albedo using our model for fine-grained snow. The absorbed solar radiation at the surface is almost entirely in the near-infrared where snow albedo is considerably lower than its visible values. Snow-surface albedo increases with zenith angle for all sun angles. The spectrally integrated planetary albedo is about 10% less than the surface albedo and shows the same zenith-angle dependence for high sun. But for solar zenith angles greater than about 70° the planetary albedo may show a contrary trend because the increased atmospheric absorption in the long slant path overwhelms the zenith-angle dependence of the snow albedo. Clouds raise the spectrally integrated planetary albedo because the cloud particles are smaller, on average, than the snow grains. Clouds raise the surface albedo by absorbing near-infrared radiation and thus altering the spectral distribution of the solar radiation reaching the surface. The Antarctic atmosphere is so dry that more solar radiation may actually be absorbed by ozone than by water vapor, even for a water-vapor saturated troposphere, in contrast to the situation elsewhere. As the solar absorption due to ozone is enhanced by the lack of water vapor, so is the absorption due to C02. Because some of the water-vapor absorption bands overlap CO2 absorption bands, the radiation budget is more sensitive to CO2 variations in the Antarctic than elsewhere. The radiation-budget effects of possible future increases as well as the likely Pleistocene reductions of atmospheric CO2 are investigated. This paper will be submitted in full to the Journal of Geophysical Research. This research was supported by US National Science Foundation grant ATM-80-24641. The computations were done at the National Center for Atmospheric Research.

scholarly journals Spectral Radiation Modeling for the Antarctic Plateau: Effects of Clouds, Ozone and CO2 ON THE Radiation Budget(Abstract only)

1982 ◽  
Vol 3 ◽  
pp. 356-356
Author(s):  
Stephen G. Warren ◽  
Warren J. Wiscombe
Keyword(s):  
Water Vapor ◽  
Solar Radiation ◽  
Zenith Angle ◽  
Surface Albedo ◽  
Radiation Budget ◽  
Radiation Balance ◽  
Snow Surface ◽  
Absorption Bands ◽  
Planetary Albedo ◽  
The Antarctic

The radiation balance at and above a snow-covered surface is affected not only by the high general level of the surface albedo, but also by the strong spectral variation of that albedo. Furthermore, the fact that clouds and snow have highly correlated optical properties means that the radiative problem of clouds over a snow surface is a particularly difficult one.Both for its own intrinsic interest, and because it is in many ways as clear an example of snowatmosphere radiative interactions as one is likely to find, we have chosen to make spectrally detailed model calculations of solar and long-wave radiation over Antarctica using an atmospheric radiation model of Wiscombe (1975) coupled to the recent snow reflectivity model of Wiscombe and Warren (1980). Typical clear and cloudy situations are studied. Radiative fluxes are examined particularly at the surface and the top of the atmosphere since these are the locations of most past and future measurements.Radiation budget calculations are compared with observations at Plateau station for various sun angles and cloud conditions. The effects on the radiation balance of a sub-visible ice-crystal cloud (“clear-sky ice-crystal precipitation”), as well as observed water clouds over the snow surface are investigated.Because the snow of the Antarctic plateau is very clean, falls throughout the summer, and never melts, we can make accurate calculations of the surface albedo using our model for fine-grained snow. The absorbed solar radiation at the surface is almost entirely in the near-infrared where snow albedo is considerably lower than its visible values.Snow-surface albedo increases with zenith angle for all sun angles. The spectrally integrated planetary albedo is about 10% less than the surface albedo and shows the same zenith-angle dependence for high sun. But for solar zenith angles greater than about 70° the planetary albedo may show a contrary trend because the increased atmospheric absorption in the long slant path overwhelms the zenith-angle dependence of the snow albedo.Clouds raise the spectrally integrated planetary albedo because the cloud particles are smaller, on average, than the snow grains. Clouds raise the surface albedo by absorbing near-infrared radiation and thus altering the spectral distribution of the solar radiation reaching the surface.The Antarctic atmosphere is so dry that more solar radiation may actually be absorbed by ozone than by water vapor, even for a water-vapor saturated troposphere, in contrast to the situation elsewhere.As the solar absorption due to ozone is enhanced by the lack of water vapor, so is the absorption due to C02. Because some of the water-vapor absorption bands overlap CO2 absorption bands, the radiation budget is more sensitive to CO2 variations in the Antarctic than elsewhere. The radiation-budget effects of possible future increases as well as the likely Pleistocene reductions of atmospheric CO2 are investigated.This paper will be submitted in full to the Journal of Geophysical Research. This research was supported by US National Science Foundation grant ATM-80-24641. The computations were done at the National Center for Atmospheric Research.

scholarly journals Electromechanically reconfigurable optical nano-kirigami

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shanshan Chen ◽  
Zhiguang Liu ◽  
Huifeng Du ◽  
Chengchun Tang ◽  
Chang-Yin Ji ◽  
...  
Keyword(s):  
Near Infrared ◽  
Large Range ◽  
Three Dimensional ◽  
High Contrast ◽  
Si Substrate ◽  
High Modulation ◽  
Gold Nanostructure ◽  
Infrared Wavelengths ◽  
On Chip ◽  
Nano Electromechanical System

AbstractKirigami, with facile and automated fashion of three-dimensional (3D) transformations, offers an unconventional approach for realizing cutting-edge optical nano-electromechanical systems. Here, we demonstrate an on-chip and electromechanically reconfigurable nano-kirigami with optical functionalities. The nano-electromechanical system is built on an Au/SiO2/Si substrate and operated via attractive electrostatic forces between the top gold nanostructure and bottom silicon substrate. Large-range nano-kirigami like 3D deformations are clearly observed and reversibly engineered, with scalable pitch size down to 0.975 μm. Broadband nonresonant and narrowband resonant optical reconfigurations are achieved at visible and near-infrared wavelengths, respectively, with a high modulation contrast up to 494%. On-chip modulation of optical helicity is further demonstrated in submicron nano-kirigami at near-infrared wavelengths. Such small-size and high-contrast reconfigurable optical nano-kirigami provides advanced methodologies and platforms for versatile on-chip manipulation of light at nanoscale.

scholarly journals Accuracy Analysis of International Reference Ionosphere 2016 and NeQuick2 in the Antarctic

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1551
Author(s):  
Zihuai Guo ◽  
Yibin Yao ◽  
Jian Kong ◽  
Gang Chen ◽  
Chen Zhou ◽  
...  
Keyword(s):  
Solar Radiation ◽  
International Reference Ionosphere ◽  
Electron Content ◽  
Observation Data ◽  
Dual Frequency ◽  
Total Electron ◽  
International Reference ◽  
Antarctic Continent ◽  
The Antarctic ◽  
Frequency Observation

Global navigation satellite system (GNSS) can provide dual-frequency observation data, which can be used to effectively calculate total electron content (TEC). Numerical studies have utilized GNSS-derived TEC to evaluate the accuracy of ionospheric empirical models, such as the International Reference Ionosphere model (IRI) and the NeQuick model. However, most studies have evaluated vertical TEC rather than slant TEC (STEC), which resulted in the introduction of projection error. Furthermore, since there are few GNSS observation stations available in the Antarctic region and most are concentrated in the Antarctic continent edge, it is difficult to evaluate modeling accuracy within the entire Antarctic range. Considering these problems, in this study, GNSS STEC was calculated using dual-frequency observation data from stations that almost covered the Antarctic continent. By comparison with GNSS STEC, the accuracy of IRI-2016 and NeQuick2 at different latitudes and different solar radiation was evaluated during 2016–2017. The numerical results showed the following. (1) Both IRI-2016 and NeQuick2 underestimated the STEC. Since IRI-2016 utilizes new models to represent the F2-peak height (hmF2) directly, the IRI-2016 STEC is closer to GNSS STEC than NeQuick2. This conclusion was also confirmed by the Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) occultation data. (2) The differences in STEC of the two models are both normally distributed, and the NeQuick2 STEC is systematically biased as solar radiation increases. (3) The root mean square error (RMSE) of the IRI-2016 STEC is smaller than that of the NeQuick2 model, and the RMSE of the two modeling STEC increases with solar radiation intensity. Since IRI-2016 relies on new hmF2 models, it is more stable than NeQuick2.

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