Atmospheric Extinction Research Articles

Generalised Trends In Atmospheric Attenuation And The Importance of Accurate Extinction Calculation

The purpose of this literature review is to explore and quantify the causes of attenuation of electromagnetic radiation, as well as to develop generalized trends for extinction as a function of influential factors (wavelength of incident electromagnetic wave, altitude of observatory, variations in seasons). This literature review also discusses the implications of precise measurement of atmospheric attenuation in determining intrinsic luminosity of stars in astronomical photometry and significance of accurate measurement for atmospheric extinction to precisely calculate the mass, size and lifetime of stars in the main sequence of the Hertzsprung-Russell plot diagram.

Source apportionment of PM2.5 and visibility in Jinan, China

Atmospheric extinction is impacted by the chemical composition of particles. To better understand the chemical composition of PM2.5 (particles with diameters of less than 2.5 μm) and its relationship with extinction, one-month sampling campaigns were carried out in four different seasons from 2013 to 2014 in Jinan, China. The seasonal average concentrations of PM2.5 were 120.9 (autumn), 156.6 (winter), 102.5 (spring), and 111.8 μg/m3 (summer). The reconstructed PM2.5 chemical composition showed that sulfate, nitrate, chlorine salt, organic matter (OM), mineral dust, elemental carbon (EC) and others accounted for 25%, 14%, 2%, 24%, 22%, 3% and 10%, respectively. The relationship between the chemical composition of PM2.5 and visibility was reconstructed by the IMPROVE method, and ammonium sulfate, ammonium nitrate, OM and EC dominated the visibility. Seven main sources were resolved for PM2.5, including secondary particles, coal combustion, biomass burning, industry, motor vehicle exhaust, soil dust and cooking, which accounted for 37%, 21%, 13%, 13%, 12%, 3% and 1%, respectively. The contributions of different sources to visibility were similar to those to PM2.5. With increasing severity of air pollution, the contributions of secondary particles and coal combustion increased, while the contribution of motor vehicle exhaust decreased. The results showed that coal combustion and biomass burning were still the main sources of air pollution in Jinan.

An automated all-sky atmospheric monitoring camera for a next-generation ultrahigh-energy cosmic-ray observatory

We have developed a fully-automated instrument (FASCam—Fast All Sky Camera) designed to capture night all-sky images and analyse cloudiness and coarse atmospheric properties for a proposed next-generation ultrahigh energy cosmic ray observatory, called the Fluorescence detector Array of Single-pixel Telescopes (FAST). FASCam has a 360 × 90̂ (azimuth and elevation) field of view and is equipped with a series of photometric Johnson-Cousins filters (BVR) and an Ultra-violet (UV) filter. The camera is installed on the top of one of the three FAST prototype telescope buildings located in central Utah, U.S.A. . An online analysis of the images provides real time cloud coverage maps and coarse atmospheric extinction measurements and a night sky background estimate in the field of view of the FAST fluorescence telescopes. The result serves as an input parameter for the operation of the telescopes and avoids unnecessary data taking in the case of clouds covering the field of view of the telescopes, high atmospheric extinction, or high night sky background.

Impact of dimethylsulfide chemistry on air quality over the Northern Hemisphere

We implement oceanic dimethylsulfide (DMS) emissions and its atmospheric chemical reactions into the Community Multiscale Air Quality (CMAQv53) model and perform annual simulations without and with DMS chemistry to quantify its impact on tropospheric composition and air quality over the Northern Hemisphere. DMS chemistry enhances both sulfur dioxide (SO2) and sulfate (SO42−) over seawater and coastal areas. It enhances annual mean surface SO2 concentration by +46 pptv and SO42−by +0.33 μg/m3 and decreases aerosol nitrate concentration by −0.07 μg/m3 over seawater compared to the simulation without DMS chemistry. The changes decrease with altitude and are limited to the lower atmosphere. Impacts of DMS chemistry on SO42− are largest in the summer and lowest in the fall due to the seasonality of DMS emissions, atmospheric photochemistry and resultant oxidant levels. Hydroxyl and nitrate radical-initiated pathways oxidize 75% of the DMS while halogen-initiated pathways oxidize 25%. DMS chemistry leads to more acidic particles over seawater by decreasing aerosol pH. Increased SO42−from DMS enhances atmospheric extinction while lower aerosol nitrate reduces the extinction so that the net effect of DMS chemistry on visibility tends to remain unchanged over most of the seawater.

Humidity and PM2.5 composition determine atmospheric light extinction in the arid region of northwest China

Atmospheric visibility can directly reflect the air quality. In this study, we measured water-soluble ions (WSIs), organic and element carbon (OC and EC) in PM2.5 from September 2017 to August 2018 in Urumqi, NW China. The results show that SO42−, NO3− and NH4+ were the major WSIs, together accounting for 7.32%–84.12% of PM2.5 mass. Total carbon (TC=OC+EC) accounted for 12.12% of PM2.5 mass on average. And OC/EC > 2 indicated the formation of secondary organic carbon (SOC). The levels of SO42−, NO3− and NH4+ in low visibility days were much higher than those in high visibility days. Relative humidity (RH) played a key role in affecting visibility. The extinction coefficient (bext) that estimated via Koschmieder formula with visibility was the highest in winter (1441.05 ± 739.95 Mm−1), and the lowest in summer (128.58 ± 58.00 Mm−1). The bext that estimated via IMPROVE formula with PM2.5 chemical component was mainly contributed by (NH4)2SO4 and NH4NO3. The bext values calculated by both approaches presented a good correlation with each other (R2 = 0.87). Multiple linear regression (MLR) method was further employed to reconstruct the empirical regression model of visibility as a function of PM2.5 chemical components, NO2 and RH. The results of source apportionment by Positive Matrix Factorization (PMF) model showed that residential coal combustion and vehicle emissions were the major sources of bext.

Study of aerosol content based on spectrophotometric observations: A comparison with long-term extinction profile from photometric observations

Spectroscopic observations of standard stars (spectrophotometric) have been carried out at Bosscha Observatory ITB (latitude= 6°49′28″ S, longitude= 107°36′56″ E, altitude=1310 m) using the Celestron C-11 reflector (D=11 inches, F/10.0), equipped with NEO R-1000 spectrograph (Resolution of 1000), and ST-8XME CCD camera to deduce total atmospheric extinction curve. Spectrograms were reduced with the long-slit task in the Image Reduction and Analysis Facility (IRAF). The total extinction curve obtained from observation is decomposed into three main components, i.e. Rayleigh scattering, Ozone and water vapor absorptions, and extinction by aerosol. The extinction profile by Aerosol serves as an important indication on size and distribution of particulates as the main constituent of atmospheric pollutant. This pollutant can be resulted from natural process or anthropogenic activities. The behavior of atmospheric extinction over Bosscha Observatory based on long-term astronomical photometric database (1982-1993) was previously studied by one of us in 1993. In this study we analyze new data and study the dynamics of atmosphere by comparing our recent result with that from long-term photometric observations to indicate variation of degree of atmospheric turbidity, particulate size and its distribution over the atmosphere. We recommend that long-term regular based spectrophotometry at an Observatory is imperative as an effective means to gain our insight on atmospheric dynamic.

Comparison of the Lunar Models Using the Hyper-Spectral Imager Observations in Lijiang, China

A lunar observation campaign was conducted using a hyper-spectral imaging spectrometer in Lijiang, China from December 2015 to February 2016. The lunar hyper-spectral images in the visible to near-infrared region (VNIR) have been obtained in different lunar phases with absolute scale established by the National Institute of Metrology (NIM), China using the lamp–plate calibration system. At the same time, the aerosol optical depth (AOD) is measured regularly by a lidar and a lunar CE318U for atmospheric characterization to provide nightly atmosphere extinction correction of lunar observations. This paper addressed the complicated data processing procedure in detail from raw images of the spectrometer into the spectral lunar irradiance in different lunar phases. The result of measurement shows that the imaging spectrometer can provide lunar irradiance with uncertainties less than 3.30% except for absorption bands. Except for strong atmosphere absorption region, the mean spectral irradiance difference between the measured irradiance and the ROLO (Robotic Lunar Observatory) model is 8.6 ± 2% over the course of the lunar observation mission. The ROLO model performs more reliable to clarify absolute and relative accuracy of lunar irradiance than that of the MT2009 model in different Sun–Moon–Earth geometry. The spectral ratio analysis of lunar irradiance shows that band-to-band variability in the ROLO model is consistent within 2%, and the consistency of the models in the lunar phase and spectrum is well analyzed and evaluated from phase dependence and phase reddening analysis respectively.

Toward an atlas of the number of visible stars

Modelling techniques for the propagation of light pollution in the atmosphere allow the computation of maps of artificial night sky brightness in any direction of the sky, involving a large number of details from satellite data. Cinzano et al. (2001a) introduced a method of mapping naked eye star visibility at the zenith from large areas based on satellite radiance measurements and Garstang models of the propagation of light pollution. It takes into account the altitude of each land area from digital elevation data, natural sky brightness in the chosen sky direction based on the Garstang approach, eye capability after Garstang and Schaefer, and atmospheric extinction in the visual photometric band. Here we discuss how to use these methods to obtain maps of the average number of visible stars when looking at the night sky hemisphere, finally answering, site by site, the question of how many stars are visible in the sky. This is not trivial, as the number of stars visible depends on the limiting magnitude in each direction in the sky, and this depends on sky brightness in that direction, atmospheric extinction at that zenith distance and the observer's visual acuity and experience. We present, as an example, a map of the number of visible stars in Italy to an average observer on clear nights with a resolution of approximately 1 km.

Exploring Thermospheric Variations Triggered by Severe Geomagnetic Storm on 26 August 2018 Using GRACE Follow‐On Data

AbstractWith the successful launch of the satellite mission Gravity Recovery and Climate Experiment (GRACE) Follow‐On in May 2018 the opportunity arises to resume the analysis of accelerometer data regarding space weather induced perturbations of the Earth's thermosphere. On 21 August 2018 a complex interplanetary coronal mass ejections occurred on the Sun, which subsequently triggered an unexpected large geomagnetic storm on 26 August. We present a detailed analysis of the interplanetary coronal mass ejection eruption and explore the occurred perturbation of the neutral mass density in the upper Earth's atmosphere. Due to the heating and the subsequent expansion of the thermosphere also the drag force acting on the spacecraft is enhanced. This leads to an additional storm‐induced orbit decay, which we calculate by means of variations in the semimajor axis. The evaluation is based on the utilization of accelerometer measurements from GRACE Follow‐On. For the reduction of disturbing nongravitational forces we implemented a physical shadow function, which incorporates the Earth's oblateness and the atmospheric refraction and extinction. Additionally, the estimation of Earth's reradiation is now based on hourly measurements by the Clouds and the Earth's Radiant Energy System. The resulting atmospheric densities and orbit decays are compared with predictions from our preliminary thermospheric forecasting tool, which is based on the study by Krauss et al. (2018, https://doi.org/10.1029/2018JA025778). The evaluation shows that the maximum estimated orbit decay triggered by the geomagnetic storm on 26 August is in the order of approximately 8.2 m and thus in good accordance with the forecasted value (9.5 m)—predicted with a lead time of about 60 min.

Measurement of Atmospheric Scintillation during a Period of Saharan Dust (Calima) at Observatorio del Teide, Iz̃ana, Tenerife, and the Impact on Photometric Exposure Times

We present scintillation noise profiles captured at the Observatorio del Teide, Izaña, Tenerife, over a one-week period in 2017 September. Contemporaneous data from the Birmingham Solar Oscillations Network (BiSON) and the Stellar Activity (STELLA) robotic telescopes provides estimates of daily atmospheric extinction allowing the scintillation noise to be placed within the context of overall atmospheric conditions. We discuss the results both in terms of the impact on BiSON spectrophotometer design, and for astronomical observations more generally. We find that scintillation noise power reduces by half at about 5 Hz, and is reduced to one tenth between 20 and 30 Hz even during periods of mild Calima, where visibility is reduced due to high concentrations of mineral dust in the atmosphere. We show that the common accepted exposure time of <10 ms for limiting the effect of scintillation noise in ground based photometry may be increased, and that depending on the application there may be little benefit to achieving exposure times shorter than 50 ms, relaxing constraints on detector gain and bandwidth.

Seasonal variation of atmospheric vertical extinction and its interaction with meteorological factors in the Yangtze River Delta region

Based on ground-based lidar and microwave radiometer observations in Hangzhou from 1 January 2013 to 31 December 2015, the monthly characteristics of diurnal extinction as well as atmospheric boundary layer (ABL) were studied. The interactions between temperature (T), humidity fields including relative humidity (RH) and specific humidity (SH) and atmospheric stratification (AS) were analyzed to discuss the meteorological factors in the Yangtze River Delta region during the study period. The top of ABLMPL varied from 0.8 km to 1.0 km throughout in January with higher extinction intensity close to the surface combined to the largest PM2.5 about 100–120 μg/m3. Then the ABLMPL could develop up to 1.5 km in the spring due to the weaker extinction during the daytime. The RH in the whole column in January and December was lower than the mean value (ranging from 5% to 20%) distributed from the ground to 3 km. From May to September, the RH anomaly profiles became positive contributed to larger extinction by strengthened the particle scattering ability. In January and December, the AS was stable from the surface to 3 km coincided with the extinction distribution; while in July and August, the gradient of Δθse decreased which favored the diffusion of particle in the air. Moreover, April and October presented turning points in the variation of θse. The humidity field reveals a stable condition in January and December which favored particles suppressed from the near surface to 3 km; the temperature field has tended towards a neutral state in most months except for February. The first change-point of the meteorological fields was found in April possibly attributable to the abnormal abrupt in the subtropical high. This study could have important reference for understanding regional air quality and governing air control.

Characteristics of Aerosol during a Severe Haze-Fog Episode in the Yangtze River Delta: Particle Size Distribution, Chemical Composition, and Optical Properties

Particle size distribution, water soluble ions, and black carbon (BC) concentration in a long-term haze-fog episode were measured using a wide-range particle spectrometer (WPS), a monitor for aerosols and gases (MARGA), and an aethalometer (AE33) in Nanjing from 16 to 27 November, 2018. The observation included five processes of clean, mist, mix, haze, and fog. Combined with meteorological elements, the HYSPLIT model, and the IMPROVE model, we analyzed the particle size distribution, chemical composition, and optical properties of aerosols in different processes. The particle number size distribution (PNSD) in five processes differed: It was bimodal in mist and fog and unimodal in clean, mix, and haze. The particle surface area size distribution (PSSD) in different processes showed a bimodal distribution, and the second peak of the mix and fog processes shifted to a larger particle size at 480 nm. The dominant air masses in five processes differed and primarily originated in the northeast direction in the clean process and the southeast direction in the haze process. In the mist, mix, and fog processes local air masses dominated. NO3− was the primary component of water soluble ions, with the lowest proportion of 45.6% in the clean process and the highest proportion of 53.0% in the mix process. The ratio of NH4+ in the different processes was stable at approximately 23%. The ratio of SO42− in the clean process was 26.2%, and the ratio of other processes was approximately 20%. The average concentration of BC in the fog processes was 10,119 ng·m−3, which was 3.55, 1.80, 1.60, and 1.46 times that in the processes of clean, mist, mix, and haze, respectively. In the different processes, BC was primarily based on liquid fuel combustion. NO3−, SO42−, and BC were the main contributors to the atmospheric extinction coefficient and contributed more than 90% in different processes. NO3− contributed 398.43 Mm−1 in the mix process, and SO42− and BC contributed 167.90 Mm−1 and 101.19 Mm−1, respectively, during the fog process.

Real-time atmospheric extinction variation analysis with the Photometric Telescope at Xinglong Observatory

We present the Photometric Auxiliary System (PAS) attached to the 25-cm Photometric Telescope (PT) at Xinglong Observatory of National Astronomical Observatories, Chinese Academy of Sciences (NAOC). This PAS can provide real-time atmospheric extinction for other telescopes at the same station for flux calibration via observing standard stars, e.g. the 2.16-m reflector and 1-m telescope. Moreover, the real-time atmospheric extinction could act as a useful reference for other local telescopes regarding the adjustment of observing strategies, such as changing the exposure time, which is important for the observers. This PAS has been operated since February 2012, and we have obtained the r-band atmospheric extinction of Xinglong Observatory from February 2012 to March 2018. With these data, we have analyzed the atmospheric extinction of Xinglong Observatory in detail.

Urban air pollution monitoring using scanning Lidar

We have developed a scanning Lidar system in this work to detect urban air pollution changes in real time and locate the sources of urban air pollution. We first proposed an algorithm to retrieve atmospheric extinction coefficients, which we used to create Lidar maps. Using Lidar map of the average extinction coefficients, we identified the locations of the local maximum values, and hence, the positions of the urban air pollution sources. Experimental results indicate that this method is effective for urban air pollution monitoring.

Monsoon Season Quantitative Assessment of Biomass Burning Clear-Sky Aerosol Radiative Effect at Surface by Ground-Based Lidar Observations in Pulau Pinang, Malaysia in 2014

Direct and indirect aerosol effects are still one of the largest uncertainties related to the Earth energy budget, especially in a wild and remote region like South-East Asia, where ground-based measurements are still difficult and scarce, while endemic cloudy skies make difficult active and passive satellite observations. In this preliminary study, we analyzed and quantitatively assessed the differences between monsoon and inter-monsoon seasons, in terms of radiative effects at surface and columnar heating rate, of clear-sky biomass burning aerosols (no clouds) using ground-based lidar observations obtained with a 355 nm elastic lidar instrument, deployed since 2012 at the Physics Department of Universiti Sains Malaysia (USM). The model-based back-trajectory analysis put in evidence that, during the monsoon seasons (November–March and June–September), the air masses advected towards the observational site transit over active fire hotspot regions, in contrast with the inter-monsoon season. In between the monsoon seasons (April–May, October), the atmosphere over Penang is constituted by local background urban aerosols that originate from road traffic emissions, domestic cooking, and industrial plants emissions. The analysis was carried out using the vertically-resolved profiles of the seasonal averaged aerosol optical properties (monsoon vs. inter-monsoon seasons), e.g., the atmospheric extinction coefficient, to evaluate the seasonal surface aerosol radiative effect and column heating rate differences through the Fu–Liou–Gu (FLG) radiative transfer model. The results put in evidence that the biomass burning advection during the monsoon season (especially during the South West monsoon from June to September) lowers the noon daytime incoming solar shortwave solar radiation reaching the Earth surface with respect to the local background conditions by 91.5 W/m2 (114–69 W/m2). The aerosols also lead to an averaged heating in the first kilometer of the atmosphere of about 4.9 K/day (6.4–3.4 W/m2). The two combined effects, i.e., less absorbed energy by Earth surface and warming of the first kilometer of the boundary layer, increase the low-level stability during monsoon seasons, with a possible reduction in cloud formation and precipitation. The net effect is to exacerbate the haze episodes, as the pollutants rest trapped into the boundary layer. Besides these considerations, the lidar measurements are of great interest in this particular world region and might be used for cal/val of the future space missions, e. g., Earthcare.

Investigation of physical and optical properties of aerosol over high altitude stations along the sub-Himalayan region of North-Eastern India

The present study focuses on exploring the spectral dependency of atmospheric extinction, the size distribution of aerosols, black carbon concentration and absorption and compensation parameter along the sub-Himalayan region of northeastern India, a field campaign was conducted from 1st February to 20th February 2018. Measurements were taken at three different stations in Arunachal Pradesh i.e., Tawang (2990 m a.s.l), New Palin (1300 m a.s.l.), and Geku (200 m a.s.l.). Techniques of Ångström exponent's curvature effect has been used to determine the aerosol size distribution over the stations. The mean black carbon concentration was 3.98 ± 1.03 μg m−3, 4.27 ± 1.22 μg m−3 and 2.38 ± 1.05 μg m−3 at Tawang, New Palin, and Geku respectively. The daily mean absorption coefficient at 370 nm (σ370) was (1.46 ± 0.56) × 10−4, (1.84 ± 0.42) × 10−4, and (1.85 ± 1.8) × 10−4 at Tawang, New Palin, and Geku. Whereas daily mean absorption coefficient at 880 nm (σ880) was (0.33 ± 0.08) × 10−4, (0.42 ± 0.05) × 10−4, and (0.2 ± 0.17) × 10−4. The σ370 was 126%, 125%, and 164% higher than the absorption at the longer wavelength (880 nm) which indicates a higher biomass burning BC. The average Absorption Ångström Exponent (AAE) at 370–880 nm were 1.59 ± 0.23, 1.63 ± 0.23 and 2.28 ± 0.57 at Tawang, New Palin, and Geku. In addition, at Tawang, New Palin, and Geku, the average AAE in the shorter spectral range (370–520 nm) were 2.43 ± 0.97, 2.41 ± 1.22 and 3.09 ± 1.54, whereas in longer spectral range (520–880 nm) were 1.05 ± 0.05, 1.13 ± 0.18 and 1.44 ± 0.33, respectively.

Numerical and statistical modeling based investigation of the detection efficiency of high-spectral-resolution lidars at different laser radiation wavelengths

In the present work, a numerical and statistical modeling approach is developed for estimating the operation efficiency of high-spectral-resolution lidars (HSRLs), when determining the atmospheric aerosol extinction profiles along the lidar line of sight (LOS) at different sensing (laser) radiation wavelengths from the UV, VIS and NIR spectral ranges. The efficiency estimation is based on numerical modeling of the lidar signal profile along the LOS and the corresponding profile of the signal-to-noise ratio (SNR) of its measurement. The optimally efficient wavelength (at certain distances along the LOS) is that ensuring maximum signal strength and SNR and, consequently, brighter and clearer lidar images of specific aerosol objects and background. The results about the optimum wavelengths obtained under different atmospheric-turbidity conditions (clear or hazy atmosphere), in the presence of cirrus clouds, are proved by statistical modeling and processing of realistic (noisy) lidar profiles and recovering the atmospheric extinction profiles along the LOS. It is shown that up to certain characteristic altitudes (that are lower at higher turbidity) the UV wavelengths are advantageous in the above sense. Above the mentioned altitudes, successively, first the VIS and then the NIR wavelengths become more efficient compared to the UV wavelengths.

Atmospheric extinction levels of solar radiation using aerosol optical thickness satellite data. Validation methodology with measurement system

In order to make the concentrating solar power (CSP) more competitive, an accurate prediction of the solar radiation incident on CSP tower plant receivers is necessary. The extinction in the heliostat-receiver pathway plays an important role in the optical loss of the solar field and therefore, in the performance of the plant. In order to correctly operate these kind of plants and to select new potential emplacements, it is necessary to know the on-site levels of extinction. A methodology was developed in another published work, called Extinction AOT method (EAM), with the purpose of finding out the levels of extinction present at a location using AERONET AOT as input data. However, there is no AERONET AOT data available at any potential site of interest for setting up a solar tower plant, so, alternative approaches were necessary. This paper proposes to determine levels of extinction at any location using AOT satellite data instead of AERONET data. These results have been compared with results obtained applying the EAM with AERONET data and using real extinction measurements obtained with the CIEMAT extinction measurement system. The extinction obtained at PSA has been 5% in all cases considering the error rates.

Characteristics of Atmospheric PM2.5 Pollution and Its Influence on Visibility in Background Areas of Ji'nan

In order to study the seasonal variations in the chemical composition of atmospheric particulate matter with diameters less than 2.5 μm (PM2.5) and its influence on visibility in background areas, atmospheric PM2.5 samples were collected in spring, summer, autumn, and winter 2016 at Qixingtai in Ji'nan. The pollution characteristics of water-soluble ions components, organic carbon (OC), and elemental carbon (EC) were analyzed, and their regional transmission contributions were studied. The results show that NH4+, SO42-, and NO3- were the main components of water-soluble ions, accounting for 90.24% of the annual total ion concentration. The secondary water soluble inorganic ions were polluted severely. NO3-/SO42- presented obvious seasonal variations of high (low) levels in winter (summer). In each season, SO42- and NH4+ existed mainly in the form of (NH4)2SO4. The value of secondary OC (SOC)/OC ranged from 21.17% to 54.21%, indicating the presence of relatively severe secondary organic pollution in this area. The sulfur oxidation ratio (SOR) value in all seasons was greater than 0.1, indicating that the secondary generation of SO42- occurs in all seasons in this region, and the value of nitrogen oxidation ratio (NOR) in all seasons was higher than the SOR value. The secondary transformation of NO2 in the Qixingtai region was stronger than that of SO2. The range of atmospheric extinction coefficient (Bext) was 172.68-320.61 Mm-1, with an annual mean of 256.48 Mm-1. The atmospheric extinction coefficient showed an obvious seasonal trend of the lowest (highest) in summer (winter). The backward airflow trajectory shows that the Qixingtai was affected mainly by the long-distance transmission from Northwest China and the ocean in spring and summer and by local sources in autumn and winter. A comparison of the characteristics of atmospheric PM2.5 pollution in Ji'nan in 2008 revealed that the influence of motor vehicles on the atmospheric environment has been significantly improved.

Atmospheric horizontal extinction determined with a single digital camera-based system in the scope of solar power tower plants

A methodology based on the use of a single digital camera has been developed to determine the horizontal attenuation of solar radiation between the field of heliostats and the receiver in a solar tower plant. For this purpose, only the measurement of ambient light and a dark object at known distance is needed. The scenario for this work has been the Plataforma Solar de Almería (PSA, SE Spain), where a large black surface is available. This surface has been designed to be used for a horizontal attenuation measurement system, developed and implemented at the PSA, which is based on the use of two identical digital cameras. Specifically, the horizontal atmospheric attenuation values provided from the single camera-based system and the two camera-based system were compared during several days of July 2018, in conditions of medium values of atmospheric turbidity. A good agreement between the attenuation values obtained with both methods, within their respective uncertainty margins, has been found.