Ångström exponent errors prevent accurate visibility measurement

Visibility is an indicator of atmospheric transparency, and it is widely used in many research fields, including air pollution, climate change, ground transportation, and aviation. Although efforts have been made to improve the performance of visibility meters, a significant error exists in measured visibility data. This study conducts a well-designed simulation calibration of visibility meters, which proves that current methods of visibility measurement include a false assumption, leading to the long-term neglect of an important source of visibility error caused by erroneous values of Ångström exponents. This error has two characteristics, namely (1) independence, which means that the magnitude of the error is independent of the performance of the visibility meter. It is impossible to reduce this error by improving the performance of visibility meters. The second characteristic is (2) uncertainty, which means the magnitude of the error does not show a clear change pattern but can be substantially larger than the measurement error of visibility meters. It is impossible to accurately estimate the magnitude of this error or its influence on visibility measurements. Our simulations indicate that, as errors in visibility caused by erroneous values of Ångström exponents are inevitable using current methods of visibility measurement, reliable visibility data cannot be obtained without major adjustments to current measurement methods.

Lidar for atmospheric transparency monitoring

The transparency of the atmosphere affects the quality of astronomical observations and optical communications, but above all, it directly controls the fluxes of radiation, which is of particular interest for the study of weather and climate changes. The transparency of the atmosphere also affects the success of observing thermospheric lidar reflections. Since they are a consequence of the high transparency of the atmosphere, the reflections can be used as characteristics of atmospheric transparency.

Ångström exponent errors prevent accurate visibility measurement

Visibility is an indicator of atmospheric transparency and is widely used in many research fields, including air pollution, climate change, ground transportation, and aviation. Although efforts have been made to improve the performance of visibility meters, a significant error exists in measured visibility data. This study conducts a well-designed simulation calibration of visibility meters, which proves that current methods of visibility measurement include a false assumption, which leads to the long-term neglect of an important source of visibility error caused by erroneous values of Ångström exponents. This error has two characteristics. (1) Independence, in which the magnitude of the error is independent of the performance of the visibility meter. It is impossible to reduce this error by improving the performance of visibility meters. (2) Uncertainty, in which the magnitude of the error does not show a clear change pattern but can be substantially larger than the measurement error of visibility meters. It is impossible to accurately estimate the magnitude of this error nor its influence on visibility measurements. Our simulations indicate that, as errors in visibility caused by erroneous values of Ångström exponents are inevitable using current methods of visibility measurement, reliable visibility data cannot be obtained without major adjustments to current visibility measurement methods.

Split-cube-resonator-based metamaterials for polarization-selective asymmetric perfect absorption

A split-cube-resonator-based metamaterial structure that can act as a polarization- and direction-selective perfect absorber for the infrared region is theoretically and experimentally demonstrated. The structure, fabricated by direct laser writing and electroless silver plating, is comprised of four layers of conductively-coupled split-cube magnetic resonators, appropriately rotated to each other to bestow the desired electromagnetic properties. We show narrowband polarization-selective perfect absorption when the structure is illuminated from one side; the situation is reversed when illuminating from the other side, with the orthogonal linear polarization being absorbed. The absorption peak can be tuned in a wide frequency range by a sparser or denser arrangement of the split cube resonators, allowing to cover the entire atmospheric transparency window. The proposed metamaterial structure can find applications in polarization-selective thermal emission at the IR atmospheric transparency window for radiative cooling, in cost-effective infrared sensing devices, and in narrowband filters and linear polarizers in reflection mode.

Absence of the Impact of the Flux of Cosmic Rays and the Cloud Cover on the Energy Balance of the Earth

The energy of solar radiation absorbed by the Earth, as well as the thermal radiation of the Earth’s surface, which is released to the space through the atmospheric transparency window, depends on variations of the area of the cloud cover. Svensmark et al. suggest that the increase in the area of the cloud cover in the lower atmosphere, presumably caused by an increase in the flux of galactic cosmic rays during the quasi-bicentennial minimum of solar activity, results only in an increase in the fraction of the solar radiation reflected back to the space and weakens the flux of the solar radiation that reached the Earth surface. It is suggested, without any corresponding calculations of the variations of the average annual energy balance of the Earth Е, that the consequences will include only a deficit of the solar energy absorbed by the Earth and a cooling of the climate up to the onset of the Little Ice Age. These suggestions ignore simultaneous impact of the opposite aspects of the increase in the area of the cloud cover on the climate warming. The latter will result from a decrease in the power of thermal radiation of the Earth’s surface released to the space, and also in the power of the solar radiation reflected from the Earth’s surface, due to the increase in their absorption and reflection back to the surface. A substantial strengthening in the greenhouse effect and the narrowing of the atmospheric transparency window will also occur. Here, we estimate the impact of all aspects of possible long-term 2% growth of the cloud cover area in the lower atmosphere by Е. We found that an increase in the cloud cover area in the lower atmosphere will result simultaneously both in the decrease and in the increase in the temperature, which will virtually compensate each other, while the energy balance of the Earth E before and after the increase in the cloud cover area by 2% will stay essentially the same: E1 – Eо ≈ 0.

Numerical Procedures and their Practical Application in PV Module Analyses. Part IV: Atmospheric Transparency Parameters - Application

The presented article relates to aspects of PV module testing using natural sunlight in outdoor conditions. It is a continuation of the article Part III: parameters of atmospheric transparency - determining and correlations. This article discusses the practical application of the indexes: atmosphere purity - kTm, diffused component content - ks/o, beam clear sky index - Kb - in testing various modules in outdoor conditions. Their influence on the conversion of modules made from various absorbers and various technologies is demonstrated. Their practical application in module testing in outdoor conditions is described and it - has been demonstrated that the results of the analyses carried out using the indexes conform to the results obtained using spectral parameters of solar radiation (i.e. APE and UF). These are the measurements that require the use of very expensive equipment.