scholarly journals Restoring the night sky darkness at Observatorio del Teide: First application of the model Illumina version 2

2020 ◽  
Vol 497 (3) ◽  
pp. 2501-2516 ◽  
Author(s):  
Martin Aubé ◽  
Alexandre Simoneau ◽  
Casiana Muñoz-Tuñón ◽  
Javier Díaz-Castro ◽  
Miquel Serra-Ricart
Keyword(s):  
Radiative Transfer Model ◽  
Small Scale ◽  
Transfer Model ◽  
Light Emitting ◽  
The Past ◽  
V Band ◽  
Tenerife Island ◽  
Sky Brightness ◽  
Night Sky ◽  
Sky Radiance

ABSTRACT The propagation of artificial light into real environments is complex. To perform its numerical modelling with accuracy, one must consider hyperspectral properties of the lighting devices and their geographic positions, the hyperspectral properties of the ground reflectance, the size and distribution of small-scale obstacles, the blocking effect of topography, the lamps angular photometry and the atmospheric transfer function (aerosols and molecules). A detailed radiative transfer model can be used to evaluate how a particular change in the lighting infrastructure may affect the sky radiance. In this paper, we use the new version (v2) of the Illumina model to evaluate a night sky restoration plan for the Teide Observatory located on the island of Tenerife, Spain. In the past decades, the sky darkness was severely degraded by growing light pollution on the Tenerife Island. In this work, we use the contribution maps giving the effect of each pixel of the territory to the artificial sky radiance. We exploit the hyperspectral capabilities of Illumina v2 and show how the contribution maps can be integrated over regions or municipalities according to the Johnson–Cousins photometric bands spectral sensitivities. The sky brightness reductions per municipality after a complete shutdown and a conversion to light-emitting diodes are calculated in the Johnson–Cousins B, V, R bands. We found that the conversion of the lighting infrastructure of Tenerife with LED (1800 and 2700 K), according to the conversion strategy in force, would result in a zenith V-band sky brightness reduction of ≈0.3 mag arcsec−2.

scholarly journals Ozone formation under low solar radiation in eastern China

2019 ◽  
Author(s):  
Xuexi Tie ◽  
Xin Long ◽  
Guohui Li ◽  
Shuyu Zhao ◽  
Jianming Xu
Keyword(s):  
Solar Radiation ◽  
Eastern China ◽  
Threshold Level ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Oh Radicals ◽  
Chemical Production ◽  
The Past ◽  
Photochemical Production ◽  
Steady State Model

Abstract. PM2.5, a particulate matter with a diameter of 2.5 micrometers or less, is one of the major components of the air pollution in eastern China. In the past few years, China's government made strong efforts to reduce the PM2.5 pollutions. However, another important pollutant (ozone) becomes an important problem in eastern China. Ozone (O3) is produced by photochemistry, which requires solar radiation for the formation of O3. Under heavy PM2.5 pollution, the solar radiation is often depressed, and the photochemical production of O3 is prohibited. This study shows that during fall in eastern China, under heavy PM2.5 pollutions, there were often strong O3 photochemical productions, causing a co-occurrence of high PM2.5 and O3 concentrations. This co-occurrence of high PM2.5 and O3 is un-usual and is the main focus of this study. Recent measurements show that there were often high HONO surface concentrations in major Chinese mega cities, especially during daytime, with maximum concentrations ranging from 0.5 to 2 ppbv. It is also interesting to note that the high HONO concentrations were occurred during high aerosol concentration periods, suggesting that there were additional HONO surface sources in eastern China. Under the high daytime HONO concentrations, HONO can be photo-dissociated to be OH radicals, which enhance the photochemical production of O3. In order to study the above scientific issues, a radiative transfer model (TUV; Tropospheric Ultraviolet-Visible) is used in this study, and a chemical steady state model is established to calculate OH radical concentrations. The calculations show that by including the OH production of the photo-dissociated of HONO, the calculated OH concentrations are significantly higher than the values without including this production. For example, by including HONO production, the maximum of OH concentration under the high aerosol condition (AOD = 2.5) is similar to the value under low aerosol condition (AOD = 0.25) in the no-HONO case. This result suggests that even under the high aerosol condition, the chemical oxidizing process for O3 production can occurred, which explain the co-occurrence of high PM2.5 and high O3 in fall season in eastern China. However, the O3 concentrations were not significantly affected by the appearance of HONO in winter. This study shows that the seasonal variation of solar radiation plays important roles for controlling the OH production in winter. When the solar radiation is in a very low level in winter, it reaches the threshold level to prevent the OH chemical production, even by including the HONO production of OH. This study provides some important scientific highlights to better understand the O3 pollutions in eastern China.

scholarly journals Relative sky radiance from multi-exposure all-sky camera images

2021 ◽  
Vol 14 (3) ◽  
pp. 2201-2217
Author(s):  
Juan C. Antuña-Sánchez ◽  
Roberto Román ◽  
Victoria E. Cachorro ◽  
Carlos Toledano ◽  
César López ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Quality Criteria ◽  
High Dynamic Range ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
High Dynamic ◽  
Sky Radiance ◽  
Black Level ◽  
Hdr Image

Abstract. All-sky cameras are frequently used to detect cloud cover; however, this work explores the use of these instruments for the more complex purpose of extracting relative sky radiances. An all-sky camera (SONA202-NF model) with three colour filters narrower than usual for this kind of cameras is configured to capture raw images at seven exposure times. A detailed camera characterization of the black level, readout noise, hot pixels and linear response is carried out. A methodology is proposed to obtain a linear high dynamic range (HDR) image and its uncertainty, which represents the relative sky radiance (in arbitrary units) maps at three effective wavelengths. The relative sky radiances are extracted from these maps and normalized by dividing every radiance of one channel by the sum of all radiances at this channel. Then, the normalized radiances are compared with the sky radiance measured at different sky points by a sun and sky photometer belonging to the Aerosol Robotic Network (AERONET). The camera radiances correlate with photometer ones except for scattering angles below 10∘, which is probably due to some light reflections on the fisheye lens and camera dome. Camera and photometer wavelengths are not coincident; hence, camera radiances are also compared with sky radiances simulated by a radiative transfer model at the same camera effective wavelengths. This comparison reveals an uncertainty on the normalized camera radiances of about 3.3 %, 4.3 % and 5.3 % for 467, 536 and 605 nm, respectively, if specific quality criteria are applied.

scholarly journals Influence of spatial heterogeneity of local surface albedo on the area-averaged surface albedo retrieved from airborne irradiance measurements

2013 ◽  
Vol 6 (3) ◽  
pp. 527-537 ◽  
Author(s):  
E. Jäkel ◽  
M. Wendisch ◽  
B. Mayer
Keyword(s):  
Optical Depth ◽  
Surface Albedo ◽  
Radiative Transfer Model ◽  
Small Scale ◽  
Mean Deviation ◽  
Transfer Model ◽  
Horizontal Distance ◽  
Local Surface ◽  
Atmospheric Scattering ◽  
The Mean

Abstract. Spectral airborne upward and downward irradiance measurements are used to derive the area-averaged surface albedo. Real surfaces are not homogeneous in their reflectivity. Therefore, this work studies the effects of the heterogeneity of surface reflectivity on the area-averaged surface albedo to quantify how well aircraft measurements can resolve the small-scale variability of the local surface albedo. For that purpose spatially heterogeneous surface albedo maps were input into a 3-dimensional (3-D) Monte Carlo radiative transfer model to simulate 3-D irradiance fields. The calculated up- and downward irradiances in altitudes between 0.1 and 5 km are used to derive the area-averaged surface albedo using an iterative retrieval method that removes the effects due to atmospheric scattering and absorption within the layer beneath the considered level. For the case of adjacent land and sea surfaces, parametrizations are presented which quantify the horizontal distance from the coastline that is required to reduce surface heterogeneity effects on the area-averaged surface albedo to a given limit. The parametrization which is a function of altitude, aerosol optical depth, single scattering albedo, and the ratio of local land and sea albedo was applied for airborne spectral measurements. In addition, the deviation between area-averaged and local surface albedo is determined for more complex surface albedo maps. For moderate aerosol conditions (optical depth less than 0.4) and a wavelength range between 400 and 1000 nm, the altitude and the heterogeneity of the surface albedo are the dominant factors determining the mean deviation between local and area-averaged surface albedo. A parametrization of the mean deviation is applied to an albedo map that was derived from a Landsat image of an area in East Anglia (UK). Parametrization and direct comparison of local and area-averaged surface albedo show similar mean deviations (20% vs. 25%) over land.

scholarly journals Influence of spatial heterogeneity of local surface albedo on the area-averaged surface albedo retrieved from airborne irradiance measurements

2012 ◽  
Vol 5 (5) ◽  
pp. 7457-7487
Author(s):  
E. Jäkel ◽  
M. Wendisch ◽  
B. Mayer
Keyword(s):  
Optical Depth ◽  
Surface Albedo ◽  
Radiative Transfer Model ◽  
Small Scale ◽  
Mean Deviation ◽  
Transfer Model ◽  
Horizontal Distance ◽  
Local Surface ◽  
Atmospheric Scattering ◽  
The Mean

Abstract. Spectral airborne upward and downward irradiance measurements are used to derive the area-averaged surface albedo. Real surfaces are not homogeneous in their reflectivity. Therefore, this work studies the effects of the heterogeneity of surface reflectivity on the area-averaged surface albedo to quantify how well aircraft measurements can resolve the small-scale variability of the local surface albedo. For that purpose spatially heterogeneous surface albedo maps were input into a 3-dimensional (3-D) Monte Carlo radiative transfer model to simulate 3-D irradiance fields. The calculated up- and downward irradiances in altitudes between 0.1 km and 5 km are used to derive the area-averaged surface albedo using an iterative retrieval method that removes the effects due to atmospheric scattering and absorption within the layer beneath the considered level. For the case of adjacent land and sea surfaces a parametrization is presented which quantifies the horizontal distance to the coastline that is required to reduce surface heterogeneity effects on the area-averaged surface albedo to a given limit. The parametrization which is a function of altitude, aerosol optical depth, and the ratio of local land and sea albedo was applied for airborne spectral measurements. In addition, the deviation between area-averaged and local surface albedo is determined for more complex surface albedo maps. For moderate aerosol conditions (optical depth less than 0.4) and the visible wavelength range, the altitude and the heterogeneity of the surface albedo are the dominant factors determining the mean deviation between local and area-averaged surface albedo. A parametrization of the mean deviation is applied to an albedo map that was derived from a Landsat image of an area in East Anglia (UK). Parametrization and direct comparison of local and area-averaged surface albedo show similar mean deviations (20% vs. 25%) over land.

scholarly journals Relative sky radiance from multi-exposure all-sky camera images

2020 ◽  
Author(s):  
Juan C. Antuña-Sánchez ◽  
Roberto Román ◽  
Victoria E. Cachorro ◽  
Carlos Toledano ◽  
César López ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Quality Criteria ◽  
High Dynamic Range ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
High Dynamic ◽  
Sky Radiance ◽  
Black Level ◽  
Hdr Image

Abstract. All-sky cameras are frequently used to detect cloud cover; however, this work explores the use of these instruments for the more complex purpose of extracting relative sky radiances. An all-sky camera (SONA202-NF model) with three colour filters, narrower than usual for this kind of cameras, is configured to capture raw images at seven exposure times. A detailed camera characterization of the black level, readout noise, hot pixels and linear response is carried out. A methodology is proposed to obtain a linear high dynamic range (HDR) image and its uncertainty, which represents the relative sky radiance map at three effective wavelengths. The relative sky radiance (normalized by the sum of all radiances) is extracted from these maps and compared with the sky radiance measured at different sky points by a sun/sky photometer belonging to the Aerosol Robotic Network (AERONET). The camera radiances are in line with photometer ones excepting for scattering angles below 10º, which is probably due to some light reflections on the fisheye lens and camera dome. Camera and photometer wavelengths are not coincident, hence camera radiances are also compared with sky radiances simulated by a radiative transfer model at the same camera effective wavelengths. This comparison reveals an uncertainty on the normalized camera radiances about 3.3 %, 4.3 % and 5.3 % for 467, 536 and 605 nm, respectively, if specific quality criteria are applied.

Exploring the Assimilation of ATMS Cloud Retrieval Products and its Benefits for CrIS All-sky Radiance Simulations

2021 ◽  
Author(s):  
Xin Li ◽  
Xiaolei Zou ◽  
Mingjian Zeng ◽  
Ning Wang ◽  
Fei Tang
Keyword(s):  
Advanced Technology ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Liquid Water Path ◽  
Water Path ◽  
Sky Radiance ◽  
Cloud Liquid Water Path ◽  
Cross Track ◽  
Ice Water ◽  
Statistical Interpolation

AbstractAimed at improving all-sky Cross-track Infrared Sounder (CrIS) radiance assimilation, this study explores the benefits for CrIS all-sky radiance simulations, focusing on the accuracy of background cloud information, through assimilating cloud liquid water path (LWP), ice water path (IWP), and rain water path (RWP) data retrieved from the Advanced Technology Microwave Sounder (ATMS). The Community Radiative Transfer Model (CRTM), which considers cloud scattering and absorption processes, is applied to simulate CrIS radiances. The Gridpoint Statistical Interpolation ensemble-variational data assimilation (DA) is updated by incorporating ensemble covariances of hydrometeor variables and observation operators of LWP, IWP, and RWP. First, two DA experiments named DActrl and DAcwp are conducted with (DAcwp) and without (DActrl) assimilating ATMS LWP, IWP, and RWP data. Assimilating ATMS cloud retrieval data results in better spatial distributions of hydrometers for both a Meiyu rainfall case and a typhoon case. Analyses of DActrl and DAcwp are then used as input to the CRTM to generate CrIS all-sky radiance simulations SMallsky_DActrl and SMallsky_DAcwp, respectively. Improvements in the DAcwp analyses of hydrometeor variables are found to benefit CrIS radiance simulations, especially in cloudy regions. A long period of statistics reveals that the biases and standard deviations of all-sky observations minus simulations from SMallsky_DAcwp are notably smaller than those from SMallsky_DActrl. This pilot study suggests the potential benefit of combining the use of microwave cloud retrieval products for all-sky infrared DA.

Object-Based Metrics for Forecast Verification of Convective Development with Geostationary Satellite Data

2017 ◽  
Vol 145 (8) ◽  
pp. 3161-3178 ◽  
Author(s):  
Martin Rempel ◽  
Fabian Senf ◽  
Hartwig Deneke
Keyword(s):  
Object Identification ◽  
Geostationary Satellite ◽  
Radiative Transfer Model ◽  
Small Scale ◽  
Transfer Model ◽  
Average Brightness ◽  
Object Based ◽  
Cloud Characteristics ◽  
Summer Half ◽  
Identification Techniques

Object-based metrics are adapted and applied to geostationary satellite observations with the evaluation of cloud forecasts in convective situations as the goal. Forecasts of the convection-permitting German-focused Consortium for Small-Scale Modeling (COSMO-DE) numerical model are transformed into synthetic observations using the RTTOV radiative transfer model, and contrasted with the corresponding real observations. Threshold-based segmentation techniques are applied to the fields for object identification. The statistical properties of the traditional measures cold cloud cover and average brightness temperature amplitude are contrasted to object-based metrics of spatial aggregation and object structure. Based on 59 case days from the summer half-years between 2012 and 2014, a variance decomposition technique is applied to the time series of the metrics to identify deficits in day-to-day, diurnal, and weather-regime-related variability of cold cloud characteristics in the forecasts. Furthermore, sensitivities of the considered metrics are discussed, which result from uncertainties in the satellite forward operator and from the choice of parameters in the object identification techniques.

scholarly journals The Selection and Protection of Optical Astronomical Observing Sites in China

2012 ◽  
Vol 10 (H16) ◽  
pp. 748-748
Author(s):  
Jin Wenjing ◽  
Jinming Bai ◽  
Yongqiang Yao
Keyword(s):  
Artificial Satellite ◽  
Astronomical Observatory ◽  
Light Pollution ◽  
Time Service ◽  
Radio Stations ◽  
V Band ◽  
Sky Brightness ◽  
Night Sky ◽  
Economic Developments ◽  
Night Sky Brightness

Before 1950 there are two observatories, Shanghai and Purple Mountain Astronomical Observatories (SHAO and PMO), and two observing stations, Qingdao and Kunming stations in China. With the requirements of astronomical research, two observatories, Beijing and Shaanxi Astronomical Observatories (BAO and SXAO) and two artificial satellite stations, Urumqi and Changchun, were established about 1960. Based on the current management, now there are 4 observatories, SHAO, PMO, NAOC(National Astronomical Observatories), which was grouped from BAO, YNAO and 2 others, as well as XAO (Xinjiang Astronomical Observatory). The optical 1-2 m class telescopes are being operated at former four observatories. SXAO is changed as National Time Service Center. Because of city expansion as well as the traveling and economic developments, these observatories are suffered severe light pollution. For example, Zo Ce is located at the suburb of Shanghai city. A 40 cm double astrograph was installed in 1900 and a 1.56 m optical reflector have been operated since November 1987. In 1994 the seeing is better than 1 and the night sky brightness in V is about 19 mag/arcsec2, stars fainter than 20 mag with CCD are visibles. In 2007 a large playground was built in Zô Cè area. The light pollution is severe gradually. The night sky brightness has been increased to 15.8 mag/arcsec2. The other observatories have similar situation. New site surveys and found new stations to solve the problem. Except the solar and radio stations of each Astronomical Observatory, now there are 3 optical observing sites at PMO (Hong-He, Xu-Yi and Yaoan), 2 at SHAO (Zô Cè and Tian Huang Ping) and 2 at YNAO (Kunming and Gao-Mei-Gu) as well as 1 optical observing site at BAO (Xing-Long). The best observing site is Gao-Mei-Gu, which is selected as the optical observing site of YNAO and where atmospheric turbulence distribution is 0.11 near ground with heights from 6.5m to 2.7m during night. Sky brightness in B and V band are 22.34 and 21.54. The extinction coefficient K,bv and K,v are 0.298 and 0.135. The seeing measurement is 0.72’,. In the recent years a new 2.4m telescope the second largest telescope in China, was installed there.

scholarly journals Optical Properties of Polystyrene-ZnO Nanocomposite Scattering Layer to Improve Light Extraction in Organic Light-Emitting Diode

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
G. Nenna ◽  
A. De Girolamo Del Mauro ◽  
E. Massera ◽  
A. Bruno ◽  
T. Fasolino ◽  
...  
Keyword(s):  
Optical Properties ◽  
Light Emitting Diode ◽  
Light Extraction ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Experimental Measurements ◽  
Scattering Layer ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Organic Light

In this work, experimental measurements on polystyrene-ZnO nanocomposite scattering films and on organic light-emitting device with and without the scattering layers are presented. The results are also compared with Henyey-Greenstein radiative-transfer model to narrow down the parameters that can be important in the identification of more suitable scattering layers. As a result, an increase of efficiency of about 30% has been obtained that it can be translated in 60% of outcoupled light in respect to the total generated amount.

scholarly journals Global distributions of water vapour isotopologues retrieved from IMG/ADEOS data

2007 ◽  
Vol 7 (14) ◽  
pp. 3957-3968 ◽  
Author(s):  
H. Herbin ◽  
D. Hurtmans ◽  
S. Turquety ◽  
C. Wespes ◽  
B. Barret ◽  
...  
Keyword(s):  
Water Vapour ◽  
Experimental Studies ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Temporal Variations ◽  
Global Scale ◽  
Radiative Transfer Model ◽  
Small Scale ◽  
Transfer Model ◽  
Water Isotopologues

Abstract. The isotopologic composition of water vapour in the atmosphere provides valuable information on many climate, chemical and dynamical processes. The accurate measurements of the water isotopologues by remote-sensing techniques remains a challenge, due to the large spatial and temporal variations. Simultaneous profile retrievals of the main water isotopologues (i.e. H216O, H218O and HDO) and their ratios are presented here for the first time, along their retrieved global distributions. The results are obtained by exploiting the high resolution infrared spectra recorded by the Interferometric Monitor for Greenhouse gases (IMG) instrument, which has operated in the nadir geometry onboard the ADEOS satellite between 1996 and 1997. The retrievals are performed on cloud-free radiances, measured during ten days of April 1997, considering two atmospheric windows (1205–1228 cm−1; 2004–2032 cm−1) and using a line-by-line radiative transfer model and an inversion procedure based on the Optimal Estimation Method (OEM). Characterizations in terms of vertical sensitivity and error budget are provided. We show that a relatively high vertical resolution is achieved for H216O (~4–5 km), and that the retrieved profiles are in fair agreement with local sonde measurements, at different latitudes. The retrieved global distributions of H216O, H218O, HDO and their ratios are presented and found to be consistent with previous experimental studies and models. The Ocean-Continent difference, the latitudinal and vertical dependence of the water vapour amount and the isotopologic depletion are notably well reproduced. Others trends, possibly related to small-scale variations in the vertical profiles are also discussed. Despite the difficulties encountered for computing accurately the isotopologic ratios, our results demonstrate the ability of infrared nadir sounding for monitoring atmospheric isotopologic water vapour distributions on a global scale.

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